text:
ABC Transporters, Atherosclerosis and Inflammation
Fitzgerald, Michael L.; Mujawar, Zahedi; Tamehiro, Norimasa
Atherosclerosis, driven by inflamed lipid-laden lesions, can occlude the coronary arteries and lead to myocardial infarction. This chronic disease is a major and expensive health burden. However, the body is able to mobilize and excrete cholesterol and other lipids, thus preventing atherosclerosis by a process termed reverse cholesterol transport (RCT). Insight into the mechanism of RCT has been gained by the study of two rare syndromes caused by the mutation of ABC transporter loci. In Tangi...
Mapping the functional yeast ABC transporter interactome.
Snider, Jamie; Hanif, Asad; Lee, Mid Eum; Jin, Ke; Yu, Analyn R; Graham, Chris; Chuk, Matthew; Damjanovic, Dunja; Wierzbicka, Marta; Tang, Priscilla; Balderes, Dina; Wong, Victoria; Jessulat, Matthew; Darowski, Katelyn D; San Luis, Bryan-Joseph; Shevelev, Igor; Sturley, Stephen L; Boone, Charles; Greenblatt, Jack F; Zhang, Zhaolei; Paumi, Christian M; Babu, Mohan; Park, Hay-Oak; Michaelis, Susan; Stagljar, Igor
ATP-binding cassette (ABC) transporters are a ubiquitous class of integral membrane proteins of immense clinical interest because of their strong association with human disease and pharmacology. To improve our understanding of these proteins, we used membrane yeast two-hybrid technology to map the protein interactome of all of the nonmitochondrial ABC transporters in the model organism Saccharomyces cerevisiae and combined this data with previously reported yeast ABC transporter interactions in the BioGRID database to generate a comprehensive, integrated 'interactome'. We show that ABC transporters physically associate with proteins involved in an unexpectedly diverse range of functions. We specifically examine the importance of the physical interactions of ABC transporters in both the regulation of one another and in the modulation of proteins involved in zinc homeostasis. The interaction network presented here will be a powerful resource for increasing our fundamental understanding of the cellular role and regulation of ABC transporters. PMID:23831759
Mapping the functional yeast ABC transporter interactome
Snider, Jamie; Hanif, Asad; Lee, Mid Eum; Jin, Ke; Yu, Analyn R.; Graham, Chris; Chuk, Matthew; Damjanovic, Dunja; Wierzbicka, Marta; Tang, Priscilla; Balderes, Dina; Wong, Victoria; Jessulat, Matthew; Darowski, Katelyn D.; Luis, Bryan-Joseph San
ABC transporters are a ubiquitous class of integral membrane proteins of immense clinical interest because of their strong association with human disease and pharmacology. To improve our understanding of these proteins, we used Membrane Yeast Two-Hybrid (MYTH) technology to map the protein interactome of all non-mitochondrial ABC transporters in the model organism Saccharomy cescerevisiae, and combined this data with previously reported yeast ABC transporter interactions in the BioGRID databa...
Abc1: a new ABC transporter from the fission yeast Schizosaccharomyces pombe
Christensen, P U; Davis, K; Nielsen, O; Davey, William John; Nielsen, Olaf
We have isolated the abc1 gene from the fission yeast Schizosaccharomyces pombe. Sequence analysis suggests that the Abc1 protein is a member of the ABC superfamily of transporters and is composed of two structurally homologous halves, each consisting of a hydrophobic region of six transmembrane...
Identification and functional characterization of Penicillium marneffei pleiotropic drug resistance transporters ABC1 and ABC2.
Panapruksachat, Siribun; Iwatani, Shun; Oura, Takahiro; Vanittanakom, Nongnuch; Chindamporn, Ariya; Niimi, Kyoko; Niimi, Masakazu; Lamping, Erwin; Cannon, Richard D; Kajiwara, Susumu
Penicilliosis caused by the dimorphic fungus Penicillium marneffei is an endemic, AIDS-defining illness and, after tuberculosis and cryptococcosis, the third most common opportunistic infection of AIDS patients in tropical Southeast Asia. Untreated, patients have poor prognosis; however, primary amphotericin B treatment followed by prolonged itraconazole prophylaxis is effective. To identify ATP-binding cassette (ABC) transporters that may play a role in potential multidrug resistance of P. marneffei, we identified and classified all 46 P. marneffei ABC transporters from the genome sequence. PmABC1 and PmABC2 were most similar to the archetype Candida albicans multidrug efflux pump gene CDR1. P. marneffei Abc1p (PmAbc1p) was functionally expressed in Saccharomyces cerevisiae, although at rather low levels, and correctly localized to the plasma membrane, causing cells to be fourfold to eightfold more resistant to azoles and many other xenobiotics than untransformed cells. P. marneffei Abc2p (PmAbc2p) was expressed at similarly low levels, but it had no efflux activity and did not properly localize to the plasma membrane. Interestingly, PmAbc1p mislocalized and lost its transport activity when cells were shifted to 37 °C. We conclude that expression of PmAbc1p in S. cerevisiae confers resistance to several xenobiotics indicating that PmAbc1p may be a multidrug efflux pump. PMID:26782644
Isolation and Characterization of the Colletotrichum acutatum ABC Transporter CaABC1
Suyoung Kim
Full Text Available Fungi tolerate exposure to various abiotic stresses, including cytotoxic compounds and fungicides, via their ATP-driven efflux pumps belonging to ATP-binding cassette (ABC transporters. To clarify the molecular basis of interaction between the fungus and various abiotic stresses including fungicides, we constructed a cDNA library from germinated conidia of Colletotrichum acutatum, a major anthracnose pathogen of pepper (Capsicum annum L.. Over 1,000 cDNA clones were sequenced, of which single clone exhibited significant nucleotide sequence homology to ABC transporter genes. We isolated three fosmid clones containing the C. acutatum ABC1 (CaABC1 gene in full-length from genomic DNA library screening. The CaABC1 gene consists of 4,059 bp transcript, predicting a 1,353-aa protein. The gene contains the typical ABC signature and Walker A and B motifs. The 5′-flanking region contains a CAAT motif, a TATA box, and a Kozak region. Phylogenetic and structural analysis suggested that the CaABC1 is a typical ABC transporter gene highly conserved in various fungal species, as well as in Chromista, Metazoans, and Viridiplantae. We also found that CaABC1 was up-regulated during conidiation and a minimal medium condition. Moreover, CaABC1 was induced in iprobenfos, kresoxim-methyl, thiophanate-methyl, and hygromycin B. These results demonstrate that CaABC1 is necessary for conidiation, abiotic stress, and various fungicide resistances. These results will provide the basis for further study on the function of ABC transporter genes in C. acutatum.
How heterogeneous is the involvement of ABC transporters against insecticides?
Porretta, Daniele; Epis, Sara; Mastrantonio, Valentina; Ferrari, Marco; Bellini, Romeo; Favia, Guido; Urbanelli, Sandra
Understanding the molecular mechanisms underlying cellular defense against xenobiotic compounds is a main research issue in medical and veterinary entomology, as insecticide/acaricide resistance is a major threat in the control of arthropods. ABC transporters are recognized as a component of the detoxifying mechanism in arthropods. We investigated the possible involvement of ABC transporters in defense to the organophosphate insecticide temephos in the malarial vector Anopheles stephensi. We performed bioassays on larvae of An. stephensi, using insecticide alone and in combination with ABC-transporter inhibitors, to assess synergism between these compounds. Next, we investigated the expression profiles of six ABC transporter genes in larvae exposed to temephos. Surprisingly, neither bioassays nor gene expression analyses provided any evidence for a major role of ABC transporters in defense against temephos in An. stephensi. We thus decided to review existing literature to generate a record of other studies that failed to reveal a role for ABC transporters against particular insecticides/acaricides. A review of the scientific literature led to the recovery of 569 papers about ABC transporters; among these, 50 involved arthropods, and 10 reported negative results. Our study on An. stephensi and accompanying literature review highlight the heterogeneity that exists in ABC transporter involvement in defense/resistance mechanisms in arthropods. PMID:26855383
Fungal ABC transporter deletion and localization analysis.
Kovalchuk, Andriy; Weber, Stefan S; Nijland, Jeroen G; Bovenberg, Roel A L; Driessen, Arnold J M
Fungal cells are highly complex as their metabolism is compartmentalized harboring various types of subcellular organelles that are bordered by one or more membranes. Knowledge about the intracellular localization of transporter proteins is often required for the understanding of their biological function. Among different approaches available, the localization analysis based on the expression of GFP fusions is commonly used as a relatively fast and cost-efficient method that allows visualization of proteins of interest in both live and fixed cells. In addition, inactivation of transporter genes is an important tool to resolve their specific function. Here we provide a detailed protocol for the deletion and localization analysis of ABC transporters in the filamentous fungus Penicillium chrysogenum. It includes construction of expression plasmids, their transformation into fungal strains, cultivation of transformants, microscopy analysis, as well as additional protocols on staining of fungal cells with organelle-specific dyes like Hoechst 33342, MitoTracker DeepRed, and FM4-64. PMID:22183644
Human ATP-binding cassette (ABC transporter family
Vasiliou Vasilis
Full Text Available Abstract There exist four fundamentally different classes of membrane-bound transport proteins: ion channels; transporters; aquaporins; and ATP-powered pumps. ATP-binding cassette (ABC transporters are an example of ATP-dependent pumps. ABC transporters are ubiquitous membrane-bound proteins, present in all prokaryotes, as well as plants, fungi, yeast and animals. These pumps can move substrates in (influx or out (efflux of cells. In mammals, ABC transporters are expressed predominantly in the liver, intestine, blood-brain barrier, blood-testis barrier, placenta and kidney. ABC proteins transport a number of endogenous substrates, including inorganic anions, metal ions, peptides, amino acids, sugars and a large number of hydrophobic compounds and metabolites across the plasma membrane, and also across intracellular membranes. The human genome contains 49 ABC genes, arranged in eight subfamilies and named via divergent evolution. That ABC genes are important is underscored by the fact that mutations in at least I I of these genes are already known to cause severe inherited diseases (eg cystic fibrosis and X-linked adrenoleukodystrophy [X-ALD]. ABC transporters also participate in the movement of most drugs and their metabolites across cell surface and cellular organelle membranes; thus, defects in these genes can be important in terms of cancer therapy, pharmacokinetics and innumerable pharmacogenetic disorders.
ABC-B transporter genes in Dirofilaria immitis.
Bourguinat, Catherine; Che, Hua; Mani, Thangadurai; Keller, Kathy; Prichard, Roger K
Dirofilaria immitis is a filarial nematode causing infection and heartworm disease in dogs and other canids, cats, and occasionally in humans. Prevention with macrocyclic lactones (ML) is recommended during the mosquito transmission season. Recently, ML resistance has been reported. ABC-B transporter genes are thought to be involved in the mechanism of ML resistance in other nematodes. This study aimed to identify all the ABC-B transporter genes in D. immitis using as a reference the nDi.2.2 D. immitis whole genome, which is not completely annotated. Using bioinformatic tools and PCR amplification on pooled D. immitis genomic DNA and on pooled cDNA, nine ABC transporter genes including one pseudogene were characterized. Bioinformatic and phylogenetic analyses allowed identification of three P-glycoproteins (Pgps) (Dim-pgp-3 Dim-pgp-10, Dim-pgp-11), of two ABC-B half transporter genes (one ortholog of Cel-haf-4 and Cel-haf-9; and one ortholog of Cel-haf-1 and Cel-haf-3), of one ABC half transporter gene (ortholog of Cel-haf-5) that contained an ABC-C motif, and of one additional half transporter that would require functional study for characterization. The number of ABC-B transporter genes identified was lower than in Caenorhabditis elegans and Haemonchus contortus. Further studies are needed to understand their possible role in ML resistance in D. immitis. These ABC transporters constitute a base for ML resistance investigation in D. immitis and advance our understanding of the molecular biology of this parasite. PMID:27164440
Export of recombinant proteins in Escherichia coli using ABC transporter with an attached lipase ABC transporter recognition domain (LARD
Moon Yuseok
Full Text Available Abstract Background ATP binding cassette (ABC transporter secretes the protein through inner and outer membranes simultaneously in gram negative bacteria. Thermostable lipase (TliA of Pseudomonas fluorescens SIK W1 is secreted through the ABC transporter. TliA has four glycine-rich repeats (GGXGXD in its C-terminus, which appear in many ABC transporter-secreted proteins. From a homology model of TliA derived from the structure of P. aeruginosa alkaline protease (AprA, lipase ABC transporter domains (LARDs were designed for the secretion of fusion proteins. Results The LARDs included four glycine-rich repeats comprising a β-roll structure, and were added to the C-terminus of test proteins. Either Pro-Gly linker or Factor Xa site was added between fusion proteins and LARDs. We attached different length of LARDs such as LARD0, LARD1 or whole TliA (the longest LARD to three types of proteins; green fluorescent protein (GFP, epidermal growth factor (EGF and cytoplasmic transduction peptide (CTP. These fusion proteins were expressed in Escherichia coli together with ABC transporter of either P. fluorescens or Erwinia chrysanthemi. Export of fusion proteins with the whole TliA through the ABC transporter was evident on the basis of lipase enzymatic activity. Upon supplementation of E. coli with ABC transporter, GFP-LARDs and EGF-LARDs were excreted into the culture supernatant. Conclusion The LARDs or whole TliA were attached to C-termini of model proteins and enabled the export of the model proteins such as GFP and EGF in E. coli supplemented with ABC transporter. These results open the possibility for the extracellular production of recombinant proteins in Pseudomonas using LARDs or TliA as a C-terminal signal sequence.
Asymmetric switching in a homodimeric ABC transporter: a simulation study.
Jussi Aittoniemi
Full Text Available ABC transporters are a large family of membrane proteins involved in a variety of cellular processes, including multidrug and tumor resistance and ion channel regulation. Advances in the structural and functional understanding of ABC transporters have revealed that hydrolysis at the two canonical nucleotide-binding sites (NBSs is co-operative and non-simultaneous. A conserved core architecture of bacterial and eukaryotic ABC exporters has been established, as exemplified by the crystal structure of the homodimeric multidrug exporter Sav1866. Currently, it is unclear how sequential ATP hydrolysis arises in a symmetric homodimeric transporter, since it implies at least transient asymmetry at the NBSs. We show by molecular dynamics simulation that the initially symmetric structure of Sav1866 readily undergoes asymmetric transitions at its NBSs in a pre-hydrolytic nucleotide configuration. MgATP-binding residues and a network of charged residues at the dimer interface are shown to form a sequence of putative molecular switches that allow ATP hydrolysis only at one NBS. We extend our findings to eukaryotic ABC exporters which often consist of two non-identical half-transporters, frequently with degeneracy substitutions at one of their two NBSs. Interestingly, many residues involved in asymmetric conformational switching in Sav1866 are substituted in degenerate eukaryotic NBS. This finding strengthens recent suggestions that the interplay of a consensus and a degenerate NBS in eukaroytic ABC proteins pre-determines the sequence of hydrolysis at the two NBSs.
ABC transporters from Botrytis cinerea in biotic and abiotic interactions
Schoonbeek, H.
Botrytis cinereais the causal agent of grey mould disease on a wide variety of crop plants. It is relatively insensitive to natural and synthetic fungitoxic compounds. This thesis describes how ABC (ATP-binding cassette) transporters contribute to protection by actively secre
The ABCs of Candida albicans Multidrug Transporter Cdr1.
Prasad, Rajendra; Banerjee, Atanu; Khandelwal, Nitesh Kumar; Dhamgaye, Sanjiveeni
In the light of multidrug resistance (MDR) among pathogenic microbes and cancer cells, membrane transporters have gained profound clinical significance. Chemotherapeutic failure, by far, has been attributed mainly to the robust and diverse array of these proteins, which are omnipresent in every stratum of the living world. Candida albicans, one of the major fungal pathogens affecting immunocompromised patients, also develops MDR during the course of chemotherapy. The pivotal membrane transporters that C. albicans has exploited as one of the strategies to develop MDR belongs to either the ATP binding cassette (ABC) or the major facilitator superfamily (MFS) class of proteins. The ABC transporter Candida drug resistance 1 protein (Cdr1p) is a major player among these transporters that enables the pathogen to outplay the battery of antifungals encountered by it. The promiscuous Cdr1 protein fulfills the quintessential need of a model to study molecular mechanisms of multidrug transporter regulation and structure-function analyses of asymmetric ABC transporters. In this review, we cover the highlights of two decades of research on Cdr1p that has provided a platform to study its structure-function relationships and regulatory circuitry for a better understanding of MDR not only in yeast but also in other organisms. PMID:26407965
Know your ABCs: Characterization and gene expression dynamics of ABC transporters in the polyphagous herbivore Helicoverpa armigera.
Bretschneider, Anne; Heckel, David G; Vogel, Heiko
Polyphagous insect herbivores are adapted to many different secondary metabolites of their host plants. However, little is known about the role of ATP-binding cassette (ABC) transporters, a multigene family involved in detoxification processes. To study the larval response of the generalist Helicoverpa armigera (Lepidoptera) and the putative role of ABC transporters, we performed developmental assays on artificial diet supplemented with secondary metabolites from host plants (atropine-scopolamine, nicotine and tomatine) and non-host plants (taxol) in combination with a replicated RNAseq experiment. A maximum likelihood phylogeny identified the subfamily affiliations of the ABC transporter sequences. Larval performance was equal on the atropine-scopolamine diet and the tomatine diet. For the latter we could identify a treatment-specific upregulation of five ABC transporters in the gut. No significant developmental difference was detected between larvae fed on nicotine or taxol. This was also mirrored in the upregulation of five ABC transporters when fed on either of the two diets. The highest number of differentially expressed genes was recorded in the gut samples in response to feeding on secondary metabolites. Our results are consistent with the expectation of a general detoxification response in a polyphagous herbivore. This is the first study to characterize the multigene family of ABC transporters and identify gene expression changes across different developmental stages and tissues, as well as the impact of secondary metabolites in the agricultural pest H. armigera. PMID:26951878
A reciprocating twin-channel model for ABC transporters.
Jones, Peter M; George, Anthony M
ABC transporters comprise a large, diverse, and ubiquitous superfamily of membrane active transporters. Their core architecture is a dimer of dimers, comprising two transmembrane (TM) domains that bind substrate, and two ATP-binding cassettes, which use the cell's energy currency to couple substrate translocation to ATP hydrolysis. Despite the availability of over a dozen resolved structures and a wealth of biochemical and biophysical data, this field is bedeviled by controversy and long-standing mechanistic questions remain unresolved. The prevailing paradigm for the ABC transport mechanism is the Switch Model, in which the ATP-binding cassettes dimerize upon binding two ATP molecules, and thence dissociate upon sequential ATP hydrolysis. This cycle of nucleotide-binding domain (NBD) dimerization and dissociation is coupled to a switch between inward- or outward facing conformations of a single TM channel; this alternating access enables substrate binding on one face of the membrane and its release at the other. Notwithstanding widespread acceptance of the Switch Model, there is substantial evidence that the NBDs do not separate very much, if at all, and thus physical separation of the ATP cassettes observed in crystallographic structures may be an artefact. An alternative Constant Contact Model has been proposed, in which ATP hydrolysis occurs alternately at the two ATP-binding sites, with one of the sites remaining closed and containing occluded nucleotide at all times. In this model, the cassettes remain in contact and the active sites swing open in an alternately seesawing motion. Whilst the concept of NBD association/dissociation in the Switch Model is naturally compatible with a single alternating-access channel, the asymmetric functioning proposed by the Constant Contact model suggests an alternating or reciprocating function in the TMDs. Here, a new model for the function of ABC transporters is proposed in which the sequence of ATP binding, hydrolysis, and
Inhibition of ABC transporters associated with multidrug resistance
Egger, Michael
The first part of this dissertation (chapters 1 and 2) deals with the inhibition of the ABC transporters ABCB1 (p-glycoprotein) and ABCG2 (breast cancer resistance protein). Less lipophilic and better water soluble analogues of the known ABCB1 inhibitor tariquidar were synthesized from one central building block via Cu(I)-catalyzed N/O-arylation reactions. These compounds were tested for their inhibitory activity against the ABCB1 transporter in a flow cytometric calcein-AM efflux assay and a...
The Twisted Dwarf's ABC: How Immunophilins Regulate Auxin Transport
Bailly, Aurélien; Sovero, Valpuri; Geisler, Markus
There is increasing evidence that immunophilins function as key regulators of plant development. One of the best investigated members, the multi-domain FKBP TWISTED DWARF1 (TWD1)/FKBP42, has been shown to reside on both the vacuolar and plasma membranes where it interacts in mirror image with two pairs of ABC transporters, MRP1/ MRP2 and PGP1/PGP19(MDR1), respectively. Twisted dwarf1 and pgp1/pgp19 mutants display strongly overlapping phenotypes, including reduction and disorientation of grow...
The role of ABCG-type ABC transporters in phytohormone transport
Borghi, Lorenzo; Kang, Joohyun; Ko, Donghwi; Lee, Youngsook; Martinoia, Enrico
Plant hormones (phytohormones) integrate endogenous and exogenous signals thus synchronizing plant growth with environmental and developmental changes. Similar to animals, phytohormones have distinct source and target tissues, hence controlled transport and focused targeting are required for their functions. Many evidences accumulated in the last years about the regulation of long-distance and directional transport of phytohormones. ATP-binding cassette (ABC) transporters turned out to play m...
Functional analysis of the ATP-binding cassette (ABC transporter gene family of Tribolium castaneum
Broehan Gunnar
Full Text Available Abstract Background The ATP-binding cassette (ABC transporters belong to a large superfamily of proteins that have important physiological functions in all living organisms. Most are integral membrane proteins that transport a broad spectrum of substrates across lipid membranes. In insects, ABC transporters are of special interest because of their role in insecticide resistance. Results We have identified 73 ABC transporter genes in the genome of T. castaneum, which group into eight subfamilies (ABCA-H. This coleopteran ABC family is significantly larger than those reported for insects in other taxonomic groups. Phylogenetic analysis revealed that this increase is due to gene expansion within a single clade of subfamily ABCC. We performed an RNA interference (RNAi screen to study the function of ABC transporters during development. In ten cases, injection of double-stranded RNA (dsRNA into larvae caused developmental phenotypes, which included growth arrest and localized melanization, eye pigmentation defects, abnormal cuticle formation, egg-laying and egg-hatching defects, and mortality due to abortive molting and desiccation. Some of the ABC transporters we studied in closer detail to examine their role in lipid, ecdysteroid and eye pigment transport. Conclusions The results from our study provide new insights into the physiological function of ABC transporters in T. castaneum, and may help to establish new target sites for insect control.
Plant ABC Transporters Enable Many Unique Aspects of a Terrestrial Plant's Lifestyle.
Hwang, Jae-Ung; Song, Won-Yong; Hong, Daewoong; Ko, Donghwi; Yamaoka, Yasuyo; Jang, Sunghoon; Yim, Sojeong; Lee, Eunjung; Khare, Deepa; Kim, Kyungyoon; Palmgren, Michael; Yoon, Hwan Su; Martinoia, Enrico; Lee, Youngsook
Terrestrial plants have two to four times more ATP-binding cassette (ABC) transporter genes than other organisms, including their ancestral microalgae. Recent studies found that plants harboring mutations in these transporters exhibit dramatic phenotypes, many of which are related to developmental processes and functions necessary for life on dry land. These results suggest that ABC transporters multiplied during evolution and assumed novel functions that allowed plants to adapt to terrestrial environmental conditions. Examining the literature on plant ABC transporters from this viewpoint led us to propose that diverse ABC transporters enabled many unique and essential aspects of a terrestrial plant's lifestyle, by transporting various compounds across specific membranes of the plant. PMID:26902186
Two molybdate/tungstate ABC transporters that interact very differently with their substrate binding proteins
Vigonsky, Elena; Ovcharenko, Elena; Lewinson, Oded
In all kingdoms of life, ATP Binding Cassette (ABC) transporters participate in many physiological and pathological processes. Despite the diversity of their functions, they have been considered to operate by a largely conserved mechanism. One deviant is the vitamin B12 transporter BtuCD that has been shown to operate by a distinct mechanism. However, it is unknown if this deviation is an exotic example, perhaps arising from the nature of the transported moiety. Here we compared two ABC impor...
An ambiguous interface – on the transport mechanism of the ABC transport complex TAP
Großmann, Nina
The adaptive immune system protects against daily infections and malignant transformation. In this, the translocation of antigenic peptides by the transporter associated with antigen processing (TAP) into the ER lumen is an essential step in the antigen presentation by MHC I molecules. The heterodimeric ATP-binding cassette transporter (ABC) TAP consist of the two halftransporters TAP1 and TAP2. Each monomer contains an N-terminal transmembrane domain (TMD) and a conserved C-terminal nucleoti...
Functional analysis of candidate ABC transporter proteins for sitosterol transport
Albrecht, C; Elliott, J I; Sardini, A;
protein (Bcrp; Abcg2) and the bile salt export pump (Bsep; Abcb11) was assessed using several assays. Unexpectedly, none of the candidate proteins mediated significant sitosterol transport. This has implications for the pathology of sitosterolemia. In addition, the data suggest that otherwise broad...
The predicted ABC transporter AbcEDCBA is required for type IV secretion system expression and lysosomal evasion by Brucella ovis.
Teane M A Silva
Full Text Available Brucella ovis is a major cause of reproductive failure in rams and it is one of the few well-described Brucella species that is not zoonotic. Previous work showed that a B. ovis mutant lacking a species-specific ABC transporter (ΔabcBA was attenuated in mice and was unable to survive in macrophages. The aim of this study was to evaluate the role of this ABC transporter during intracellular survival of B. ovis. In HeLa cells, B. ovis WT was able to survive and replicate at later time point (48 hpi, whereas an ΔabcBA mutant was attenuated at 24 hpi. The reduced survival of the ΔabcBA mutant was associated with a decreased ability to exclude the lysosomal marker LAMP1 from its vacuolar membrane, suggesting a failure to establish a replicative niche. The ΔabcBA mutant showed a reduced abundance of the Type IV secretion system (T4SS proteins VirB8 and VirB11 in both rich and acid media, when compared to WT B. ovis. However, mRNA levels of virB1, virB8, hutC, and vjbR were similar in both strains. These results support the notion that the ABC transporter encoded by abcEDCBA or its transported substrate acts at a post-transcriptional level to promote the optimal expression of the B. ovis T4SS within infected host cells.
Glycolysis Inhibition Inactivates ABC Transporters to Restore Drug Sensitivity in Malignant Cells
Ayako Nakano; Daisuke Tsuji; Hirokazu Miki; Qu Cui; Salah Mohamed El Sayed; Akishige Ikegame; Asuka Oda; Hiroe Amou; Shingen Nakamura; Takeshi Harada; Shiro Fujii; Kumiko Kagawa; Kyoko Takeuchi; Akira Sakai; Shuji Ozaki
Cancer cells eventually acquire drug resistance largely via the aberrant expression of ATP-binding cassette (ABC) transporters, ATP-dependent efflux pumps. Because cancer cells produce ATP mostly through glycolysis, in the present study we explored the effects of inhibiting glycolysis on the ABC transporter function and drug sensitivity of malignant cells. Inhibition of glycolysis by 3-bromopyruvate (3BrPA) suppressed ATP production in malignant cells, and restored the retention of daunorubic...
ABC Transporters and their Role in Nucleoside and Nucleotide Drug Resistance
Fukuda, Yu; Schuetz, John D.
ATP-binding cassette (ABC) transporters confer drug resistance against a wide range of chemotherapeutic agents, including nucleoside and nucleotide based drugs. While nucleoside based drugs have been used for many years in the treatment of solid and hematological malignancies as well as viral and autoimmune diseases, the potential contribution of ABC transporters has only recently been recognized. This neglect is likely because activation of nucleoside derivatives require an initial carrier-m...
Influence of detergents on the activity of the ABC transporter LmrA
Infed, Nacera; Hanekop, Nils; Driessen, Arnold J. M.; Smits, Sander H. J.; Schmitt, Lutz
The ABC transporter LmrA from Lactococcus lactis has been intensively studied and a role in multidrug resistance was proposed. Here, we performed a comprehensive detergent screen to analyze the impact of detergents for a successful solubilization, purification and retention of functional properties of this ABC transporter. Our screen revealed the preference of LmrA for zwitterionic detergents. In detergent solution, LmrA purified with FC-16 was highly active with respect to ATPase activity, w...
Mechanism of ABC transporters: A molecular dynamics simulation of a well characterized nucleotide-binding subunit
Peter M Jones; Anthony M George
ATP-binding cassette (ABC) transporters are membrane-bound molecular pumps that form one of the largest of all protein families. Several of them are central to phenomena of biomedical interest, including cystic fibrosis and resistance to chemotherapeutic drugs. ABC transporters share a common architecture comprising two hydrophilic nucleotide-binding domains (NBDs) and two hydrophobic transmembrane domains (TMDs) that form the substrate pathway across the membrane. The conformational changes ...
Interaction of ABC multidrug transporters with anticancer protein kinase inhibitors: substrates and/or inhibitors?
Hegedus, Csilla; Ozvegy-Laczka, Csilla; Szakács, Gergely; Sarkadi, Balázs
Protein kinase inhibitors (PKI) are becoming key agents in modern cancer chemotherapy, and combination of PKIs with classical chemotherapeutic drugs may help to overcome currently untreatable metastatic cancers. Since chemotherapy resistance is a recurrent problem, mechanisms of resistance should be clarified in order to help further drug development. Here we suggest that in addition to PKI resistance based on altered target structures, the active removal of these therapeutic agents by the MDR-ABC transporters should also be considered as a major cause of clinical resistance. We discuss the occurring systemic and cellular mechanisms, which may hamper PKI efficiency, and document the role of selected MDR-ABC transporters in these phenomena through their interactions with these anticancer agents. Moreover, we suggest that PKI interactions with ABC transporters may modulate overall drug metabolism, including the fate of diverse, chemically or target-wise unrelated drugs. These effects are based on multiple forms of MDR-ABC transporter interaction with PKIs, as these compounds may be both substrates and/or inhibitors of an ABC transporter. We propose that these interactions should be carefully considered in clinical application, and a combined MDR-ABC transporter and PKI effect may bring a major advantage in future drug development. PMID:19442047
Phenotypic profiling of ABC transporter coding genes in Myxococcus xanthus
Full Text Available Information about a gene sometimes can be deduced by examining the impact of its mutation on phenotype. However, the genome-scale utility of the method is limited because, for nearly all model organisms, the majority of mutations result in little or no observable phenotypic impact. The cause of this is often attributed to robustness or redundancy within the genome, but that is only one plausible hypothesis. We examined a standard set of phenotypic traits, and applied statistical methods commonly used in the study of natural variants to an engineered mutant strain collection representing disruptions in 180 of the 192 ABC transporters within the bacterium Myxococcus xanthus. These strains display continuous variation in their phenotypic distributions, with a small number of "outlier" strains at both phenotypic extremes, and the majority within a confidence interval about the mean that always includes wild type. Correlation analysis reveals substantial pleiotropy, indicating that the traits do not represent independent variables. The traits measured in this study co-cluster with expression profiles, thereby demonstrating that these changes in phenotype correspond to changes at the molecular level, and therefore can be indirectly connected to changes in the genome. However, the continuous distributions, the pleiotropy, and the placement of wild type always within the confidence interval all indicate that this standard set of M. xanthus phenotypic assays is measuring a narrow range of partially overlapping traits that do not directly reflect fitness. This is likely a significant cause of the observed small phenotypic impact from mutation, and is unrelated to robustness and redundancy.
A PhoPQ-Regulated ABC Transporter System Exports Tetracycline in Pseudomonas aeruginosa.
Chen, Lin; Duan, Kangmin
Pseudomonas aeruginosa is an important human pathogen whose infections are difficult to treat due to its high intrinsic resistance to many antibiotics. Here, we show that the disruption of PA4456, encoding the ATP binding component of a putative ATP-binding cassette (ABC) transporter, increased the bacterium's susceptible to tetracycline and other antibiotics or toxic chemicals. Fluorescence spectroscopy and antibiotic accumulation tests showed that the interruption of the ABC transporter caused increased intracellular accumulation of tetracycline, demonstrating a role of the ABC transporter in tetracycline expulsion. Site-directed mutagenesis proved that the conserved residues of E170 in the Walker B motif and H203 in the H-loop, which are important for ATP hydrolysis, were essential for the function of PA4456. Through a genome-wide search, the PhoPQ two-component system was identified as a regulator of the computationally predicted PA4456-4452 operon that encodes the ABC transporter system. A >5-fold increase of the expression of this operon was observed in the phoQ mutant. The results obtained also show that the expression of the phzA1B1C1D1E1 operon and the production of pyocyanin were significantly higher in the ABC transporter mutant, signifying a connection between the ABC transporter and pyocyanin production. These results indicated that the PhoPQ-regulated ABC transporter is associated with intrinsic resistance to antibiotics and other adverse compounds in P. aeruginosa, probably by extruding them out of the cell. PMID:26953208
ATP-dependent substrate transport by the ABC transporter MsbA is proton-coupled
Singh, Himansha; Velamakanni, Saroj; Deery, Michael J.; Howard, Julie; Wei, Shen L.; van Veen, Hendrik W.
ATP-binding cassette transporters mediate the transbilayer movement of a vast number of substrates in or out of cells in organisms ranging from bacteria to humans. Current alternating access models for ABC exporters including the multidrug and Lipid A transporter MsbA from Escherichia coli suggest a role for nucleotide as the fundamental source of free energy. These models involve cycling between conformations with inward- and outward-facing substrate-binding sites in response to engagement and hydrolysis of ATP at the nucleotide-binding domains. Here we report that MsbA also utilizes another major energy currency in the cell by coupling substrate transport to a transmembrane electrochemical proton gradient. The dependence of ATP-dependent transport on proton coupling, and the stimulation of MsbA-ATPase by the chemical proton gradient highlight the functional integration of both forms of metabolic energy. These findings introduce ion coupling as a new parameter in the mechanism of this homodimeric ABC transporter. PMID:27499013
ABC transporters as multidrug resistance mechanisms and the development of chemosensitizers for their reversal
Choi Cheol-Hee
Full Text Available Abstract One of the major problems related with anticancer chemotherapy is resistance against anticancer drugs. The ATP-binding cassette (ABC transporters are a family of transporter proteins that are responsible for drug resistance and a low bioavailability of drugs by pumping a variety of drugs out cells at the expense of ATP hydrolysis. One strategy for reversal of the resistance of tumor cells expressing ABC transporters is combined use of anticancer drugs with chemosensitizers. In this review, the physiological functions and structures of ABC transporters, and the development of chemosensitizers are described focusing on well-known proteins including P-glycoprotein, multidrug resistance associated protein, and breast cancer resistance protein.
Glycolysis inhibition inactivates ABC transporters to restore drug sensitivity in malignant cells.
Ayako Nakano
Full Text Available Cancer cells eventually acquire drug resistance largely via the aberrant expression of ATP-binding cassette (ABC transporters, ATP-dependent efflux pumps. Because cancer cells produce ATP mostly through glycolysis, in the present study we explored the effects of inhibiting glycolysis on the ABC transporter function and drug sensitivity of malignant cells. Inhibition of glycolysis by 3-bromopyruvate (3BrPA suppressed ATP production in malignant cells, and restored the retention of daunorubicin or mitoxantrone in ABC transporter-expressing, RPMI8226 (ABCG2, KG-1 (ABCB1 and HepG2 cells (ABCB1 and ABCG2. Interestingly, although side population (SP cells isolated from RPMI8226 cells exhibited higher levels of glycolysis with an increased expression of genes involved in the glycolytic pathway, 3BrPA abolished Hoechst 33342 exclusion in SP cells. 3BrPA also disrupted clonogenic capacity in malignant cell lines including RPMI8226, KG-1, and HepG2. Furthermore, 3BrPA restored cytotoxic effects of daunorubicin and doxorubicin on KG-1 and RPMI8226 cells, and markedly suppressed subcutaneous tumor growth in combination with doxorubicin in RPMI8226-implanted mice. These results collectively suggest that the inhibition of glycolysis is able to overcome drug resistance in ABC transporter-expressing malignant cells through the inactivation of ABC transporters and impairment of SP cells with enhanced glycolysis as well as clonogenic cells.
Evidence that Bacterial ABC-Type Transporter Imports Free EDTA for Metabolism▿
Zhang, Hua; Herman, Jacob P.; Bolton, Harvey; Zhang, Zhicheng; Clark, Sue; XUN, Luying
EDTA, a common chelating agent, is becoming a major organic pollutant in the form of metal-EDTA complexes in surface waters, partly due to its recalcitrance to biodegradation. Even an EDTA-degrading bacterium, BNC1, does not degrade stable metal-EDTA complexes. In the present study, an ABC-type transporter was identified for possible uptake of EDTA because the transporter genes and the EDTA monooxygenase gene were expressed from a single operon in BNC1. The ABC-type transporter had a periplas...
Inhibition or knockdown of ABC transporters enhances susceptibility of adult and juvenile schistosomes to Praziquantel.
Ravi S Kasinathan
Full Text Available Parasitic flatworms of the genus Schistosoma cause schistosomiasis, a neglected tropical disease that affects hundreds of millions. Treatment of schistosomiasis depends almost entirely on the drug praziquantel (PZQ. Though essential to treating and controlling schistosomiasis, a major limitation of PZQ is that it is not active against immature mammalian-stage schistosomes. Furthermore, there are reports of field isolates with heritable reductions in PZQ susceptibility, and researchers have selected for PZQ-resistant schistosomes in the laboratory. P-glycoprotein (Pgp; ABCB1 and other ATP binding cassette (ABC transporters remove a wide variety of toxins and xenobiotics from cells, and have been implicated in multidrug resistance (MDR. Changes in ABC transporter structure or expression levels are also associated with reduced drug susceptibility in parasitic helminths, including schistosomes. Here, we show that the activity of PZQ against schistosome adults and juveniles ex vivo is potentiated by co-administration of either the highly potent Pgp inhibitor tariquidar or combinations of inhibitors targeting multiple ABC multidrug transporters. Adult worms exposed to sublethal PZQ concentrations remain active, but co-administration of ABC transporter inhibitors results in complete loss of motility and disruption of the tegument. Notably, juvenile schistosomes (3-4 weeks post infection, normally refractory to 2 µM PZQ, become paralyzed when transporter inhibitors are added in combination with the PZQ. Experiments using the fluorescent PZQ derivative (R-PZQ-BODIPY are consistent with the transporter inhibitors increasing effective intraworm concentrations of PZQ. Adult worms in which expression of ABC transporters has been suppressed by RNA interference show increased responsiveness to PZQ and increased retention of (R-PZQ-BODIPY consistent with an important role for these proteins in setting levels of PZQ susceptibility. These results indicate that
Overcoming ABC transporter-mediated multidrug resistance: Molecular mechanisms and novel therapeutic drug strategies.
Li, Wen; Zhang, Han; Assaraf, Yehuda G; Zhao, Kun; Xu, Xiaojun; Xie, Jinbing; Yang, Dong-Hua; Chen, Zhe-Sheng
Multidrug resistance is a key determinant of cancer chemotherapy failure. One of the major causes of multidrug resistance is the enhanced efflux of drugs by membrane ABC transporters. Targeting ABC transporters projects a promising approach to eliminating or suppressing drug resistance in cancer treatment. To reveal the functional mechanisms of ABC transporters in drug resistance, extensive studies have been conducted from identifying drug binding sites to elucidating structural dynamics. In this review article, we examined the recent crystal structures of ABC proteins to depict the functionally important structural elements, such as domains, conserved motifs, and critical amino acids that are involved in ATP-binding and drug efflux. We inspected the drug-binding sites on ABC proteins and the molecular mechanisms of various substrate interactions with the drug binding pocket. While our continuous battle against drug resistance is far from over, new approaches and technologies have emerged to push forward our frontier. Most recent developments in anti-MDR strategies include P-gp inhibitors, RNA-interference, nano-medicines, and delivering combination strategies. With the advent of the 'Omics' era - genomics, epigenomics, transcriptomics, proteomics, and metabolomics - these disciplines play an important role in fighting the battle against chemoresistance by further unraveling the molecular mechanisms of drug resistance and shed light on medical therapies that specifically target MDR. PMID:27449595
Conformational coupling of the nucleotide-binding and the transmembrane domains in ABC transporters.
Wen, Po-Chao; Tajkhorshid, Emad
Basic architecture of ABC transporters includes two transmembrane domains (TMDs) and two nucleotide-binding domains (NBDs). Although the transport process takes place in the TMDs, which provide the substrate translocation pathway across the cell membrane and control its accessibility between the two sides of the membrane, the energy required for the process is provided by conformational changes induced in the NBDs by binding and hydrolysis of ATP. Nucleotide-dependent conformational changes in the NBDs, therefore, need to be coupled to structural changes in the TMDs. Using molecular dynamics simulations, we have investigated the structural elements involved in the conformational coupling between the NBDs and the TMDs in the Escherichia coli maltose transporter, an ABC importer for which an intact structure is available both in inward-facing and outward-facing conformations. The prevailing model of coupling is primarily based on a single structural motif, known as the coupling helices, as the main structural element for the NBD-TMD coupling. Surprisingly, we find that in the absence of the NBDs the coupling helices can be conformationally decoupled from the rest of the TMDs, despite their covalent connection. That is, the structural integrity of the coupling helices and their tight coupling to the core of the TMDs rely on the contacts provided by the NBDs. Based on the conformational and dynamical analysis of the simulation trajectories, we propose that the core coupling elements in the maltose transporter involve contributions from several structural motifs located at the NBD-TMD interface, namely, the EAA loops from the TMDs, and the Q-loop and the ENI motifs from the NBDs. These three structural motifs in small ABC importers show a high degree of correlation in motion and mediate the necessary conformational coupling between the core of TMDs and the helical subdomains of NBDs. A comprehensive analysis of the structurally known ABC transporters shows a high degree
Molecular and immunological analysis of an ABC transporter complex required for cytochrome c biogenesis.
Goldman, B S; Beckman, D L; Bali, A; Monika, E M; Gabbert, K K; Kranz, R G
The helABC genes are predicted to encode an ATP-binding cassette (ABC) transporter necessary for heme export for ligation in bacterial cytochrome c biogenesis. The recent discoveries of homologs of the helB and helC genes in plant mitochondrial genomes suggest this is a highly conserved transporter in prokaryotes and some eukaryotes with the HelB and HelC proteins comprising the transmembrane components. Molecular genetic analysis in the Gram-negative bacterium Rhodobacter capsulatus was used to show that the helABC and helDX genes are part of an operon linked to the secDF genes. To facilitate analysis of this transporter, strains with non-polar deletions in each gene, epitope and reporter-tagged HelABCD proteins, and antisera specific to the HelA and HelX proteins were generated. We directly demonstrate that this transporter is present in the cytoplasmic membrane as an HelABCD complex. The HelB and HelC but not HelD proteins are necessary for the binding and stability of the HelA protein, the cytoplasmic subunit containing the ATP-binding region. In addition we show that the HelA protein co-immunoprecipitates with either the HelC or HelD proteins. Thus, the HelABCD heme export complex is distinguished by the presence of four membrane-associated subunits and represents a unique subfamily of ABC transporters. PMID:9175857
Surface charge-specific interactions between polymer nanoparticles and ABC transporters in Caco-2 cells
Bhattacharjee, Sourav, E-mail: email@example.com [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Opstal, Edward J. van; Alink, Gerrit M. [Wageningen University, Division of Toxicology (Netherlands); Marcelis, Antonius T. M.; Zuilhof, Han [Wageningen University, Laboratory of Organic Chemistry (Netherlands); Rietjens, Ivonne M. C. M. [Wageningen University, Division of Toxicology (Netherlands)
The surface charge-dependent transport of polymeric nanoparticles (PNPs) across Caco-2 monolayers grown on transwell culture systems as an in vitro model for intestinal transport was tested. The transport of well-characterized, monodisperse, and fluorescent tri-block copolymer nanoparticles (TCNPs/size {approx}45 nm) and polystyrene nanoparticles (PSNPs/size {approx}50 nm), with different surface charges (positive and negative), was quantified. The positive PNPs showed a higher intracellular uptake and flux across the Caco-2 monolayers than the negative PNPs. Multidrug resistance/P-glycoprotein (MDR1/P-gp), a specific ATP-binding cassette (ABC) transporter, was found to play a major role in the cellular efflux of positive PNPs, whereas the multidrug resistance protein 1 took part in the efflux of negative PNPs from Caco-2 cells. The positive PNPs also caused an increased cellular uptake and apical to basolateral transport of the carcinogen PhIP across the Caco-2 monolayer. The flavonoid quercetin, which is known to interact with ABC transporters, promoted the intracellular uptake of different PNPs and interfered with the normal distribution patterns of PNPs in the transwell system. These results indicate that PNPs display surface charge-specific interactions with ABC transporters and can even affect the bioavailability of toxic food-borne compounds (like pro-carcinogens).
Sensitive and specific fluorescent probes for functional analysis of the three major types of mammalian ABC transporters.
Irina V Lebedeva
Full Text Available An underlying mechanism for multi drug resistance (MDR is up-regulation of the transmembrane ATP-binding cassette (ABC transporter proteins. ABC transporters also determine the general fate and effect of pharmaceutical agents in the body. The three major types of ABC transporters are MDR1 (P-gp, P-glycoprotein, ABCB1, MRP1/2 (ABCC1/2 and BCRP/MXR (ABCG2 proteins. Flow cytometry (FCM allows determination of the functional expression levels of ABC transporters in live cells, but most dyes used as indicators (rhodamine 123, DiOC(2(3, calcein-AM have limited applicability as they do not detect all three major types of ABC transporters. Dyes with broad coverage (such as doxorubicin, daunorubicin and mitoxantrone lack sensitivity due to overall dimness and thus may yield a significant percentage of false negative results. We describe two novel fluorescent probes that are substrates for all three common types of ABC transporters and can serve as indicators of MDR in flow cytometry assays using live cells. The probes exhibit fast internalization, favorable uptake/efflux kinetics and high sensitivity of MDR detection, as established by multidrug resistance activity factor (MAF values and Kolmogorov-Smirnov statistical analysis. Used in combination with general or specific inhibitors of ABC transporters, both dyes readily identify functional efflux and are capable of detecting small levels of efflux as well as defining the type of multidrug resistance. The assay can be applied to the screening of putative modulators of ABC transporters, facilitating rapid, reproducible, specific and relatively simple functional detection of ABC transporter activity, and ready implementation on widely available instruments.
Effects of the L511P and D512G Mutations on the Escherichia coli ABC Transporter MsbA
Schultz, Kathryn M.; Merten, Jacqueline A.; Klug, Candice S.
MsbA is a member of the ABC transporter superfamily and is homologous to ABC transporters linked to multidrug resistance. The nucleotide binding domains (NBDs) of these proteins include conserved motifs that are involved in ATP binding, including conserved SALD residues (D-loop) that are diagnostic in identifying ABC transporters but whose roles have not been identified. Within the D-loop, single point mutations L511P and D512G were discovered by random mutational analysis of MsbA to disrupt ...
ABC transporters involved in the biogenesis of the outer membrane in gram-negative bacteria.
Narita, Shin-ichiro
The outer membrane of gram-negative bacteria is an asymmetric lipid bilayer with phospholipids and lipopolysaccharides (LPSs). β-Barreled outer membrane proteins and lipoproteins are embedded in the outer membrane. All of these constituents are essential to the function of the outer membrane. The transport systems for lipoproteins have been characterized in detail. An ATP-binding cassette (ABC) transporter, LolCDE, initiates sorting by mediating the detachment of lipoproteins from the inner membrane to form a water-soluble lipoprotein-LolA complex in the periplasm. Lipoproteins are then transferred to LolB at the outer membrane and are incorporated into the lipid bilayer. A model analogous to the Lol system has been suggested for the transport of LPS, where an ABC transporter, LptBFG, mediates the detachment of LPS from the inner membrane. Recent developments in the functional characterization of ABC transporters involved in the biogenesis of the outer membrane in gram-negative bacteria are discussed. PMID:21670534
Functional analysis of ABC transporter genes from Botrytis cinerea identifies BcatrB as a transporter of eugenol
Schoonbeek, H.; Nistelrooy, van J.G.M.; Waard, de M.A.
The role of multiple ATP-binding cassette (ABC) and major facilitator superfamily (MFS) transporter genes from the plant pathogenic fungus Botrytis cinerea in protection against natural fungitoxic compounds was studied by expression analysis and phenotyping of gene-replacement mutants. The expressio
Nucleotide-induced conformational dynamics in ABC transporters from structure-based coarse grained modelling.
Flechsig, Holger
ATP-binding cassette (ABC) transporters are integral membrane proteins which mediate the exchange of diverse substrates across membranes powered by ATP molecules. Our understanding of their activity is still hampered since the conformational dynamics underlying the operation of such proteins cannot yet be resolved in detailed molecular dynamics studies. Here a coarse grained model which allows to mimic binding of nucleotides and follow subsequent conformational motions of full-length transporter structures in computer simulations is proposed and implemented. To justify its explanatory quality, the model is first applied to the maltose transporter system for which multiple conformations are known and we find that the model predictions agree remarkably well with the experimental data. For the MalK subunit the switching from open to the closed dimer configuration upon ATP binding is reproduced and, moreover, for the full-length maltose transporter, progression from inward-facing to the outward-facing state is correctly obtained. For the heme transporter HmuUV, for which only the free structure could yet be determined, the model was then applied to predict nucleotide-induced conformational motions. Upon binding of ATP-mimicking ligands the structure changed from a conformation in which the nucleotide-binding domains formed an open shape, to a conformation in which they were found in tight contact, while, at the same time, a pronounced rotation of the transmembrane domains was observed. This finding is supported by normal mode analysis, and, comparison with structural data of the homologous vitamin B12 transporter BtuCD suggests that the observed rotation mechanism may contribute a common functional aspect for this class of ABC transporters. Although in HmuuV noticeable rearrangement of essential transmembrane helices was detected, there are no indications from our simulations that ATP binding alone may facilitate propagation of substrate molecules in this transporter
ABC transporters and xenobiotic defense systems in early life stages of rainbow trout (Oncorhynchus mykiss).
Kropf, Christian; Segner, Helmut; Fent, Karl
Embryos of oviparous fish, in contrast to (ovo) viviparous species, develop in the aquatic environment, and therefore need solute transport systems at their body surfaces for maintaining internal homeostasis and defending against potentially harmful substances. We hypothesized that solute transporters undergo changes in tissue distribution from the embryo to the larval stage. We therefore studied the mRNA profiles of eight ABC transporters (abcb1a, abcb1b, abcc1, abcc2, abcc3, abcc4, abcc5, abcg2) and three solute carriers (oatp1d, putative oatp2 putative, mate1) in different body regions (head, yolk sac epithelium, abdominal viscera, skin/muscles) of developing rainbow trout. Additionally, we investigated mRNA levels of phase I (cyp1a, cyp3a) and phase II (gstp, putative ugt1, putative ugt2) biotransformation enzymes. The study covered the developmental period from the eleuthero-embryo stage to the first-feeding larval stage (1-20days post-hatch, dph). At 1dph, transcripts of abcc2, abcc4, abcg2, cyp3a, gstp, putative mate1, and putative oatp2 occurred primarily in the yolk sac epithelium, whereas at later stages expression of these genes was predominantly observed in the abdominal viscera. The functional activity of ABC transporters in fish early life stages was assessed by rhodamine B accumulation assays. Finally, we investigated the potential impact of xenobiotics (clotrimazole, clofibric acid) on the ABC and biotransformation systems of trout early life stages. While clofibric acid had no effect, clotrimazole lead to an increased rhodamine B accumulation. The results provide evidence that the transition from the eleuthero-embryo to the larval stage is accompanied by a major alteration in tissue expression of ABC transporters. PMID:26945521
Functionally Relevant Residues of Cdr1p: A Multidrug ABC Transporter of Human Pathogenic Candida albicans
Rajendra Prasad
Full Text Available Reduced intracellular accumulation of drugs (due to rapid efflux mediated by the efflux pump proteins belonging to ABC (ATP Binding Cassette and MFS (Major Facilitators superfamily is one of the most common strategies adopted by multidrug resistance (MDR pathogenic yeasts. To combat MDR, it is essential to understand the structure and function of these transporters so that inhibitors/modulators to these can be developed. The sequence alignments of the ABC transporters reveal selective divergence within much conserved domains of Nucleotide-Binding Domains (NBDs which is unique to all fungal transporters. Recently, the role of conserved but divergent residues of Candida Drug Resistance 1 (CDR1, an ABC drug transporter of human pathogenic Candida albicans, has been examined with regard to ATP binding and hydrolysis. In this paper, we focus on some of the recent advances on the relevance of divergent and conserved amino acids of CaCdr1p and also discuss as to how drug interacts with Trans Membrane Domains (TMDs residues for its extrusion from MDR cells.
Direct Observation of a Gate Tunable Band Gap in Electrical Transport in ABC-Trilayer Graphene.
Khodkov, Tymofiy; Khrapach, Ivan; Craciun, Monica Felicia; Russo, Saverio
Few layer graphene systems such as Bernal stacked bilayer and rhombohedral (ABC-) stacked trilayer offer the unique possibility to open an electric field tunable energy gap. To date, this energy gap has been experimentally confirmed in optical spectroscopy. Here we report the first direct observation of the electric field tunable energy gap in electronic transport experiments on doubly gated suspended ABC-trilayer graphene. From a systematic study of the nonlinearities in current versus voltage characteristics and the temperature dependence of the conductivity, we demonstrate that thermally activated transport over the energy-gap dominates the electrical response of these transistors. The estimated values for energy gap from the temperature dependence and from the current voltage characteristics follow the theoretically expected electric field dependence with critical exponent 3/2. These experiments indicate that high quality few-layer graphene are suitable candidates for exploring novel tunable terahertz light sources and detectors. PMID:26079989
A putative ABC transporter is involved in negative regulation of biofilm formation by Listeria monocytogenes
Zhu, Xinna; Long, Fei; Chen, Yonghui;
Listeria monocytogenes may persist for long periods in food processing environments. In some instances, this may be due to aggregation or biofilm formation. To investigate the mechanism controlling biofilm formation in the food-borne pathogen L. monocytogenes, we characterized LM-49, a mutant with...... enhanced ability of biofilm-formation generated via transposon Tn917 mutagenesis of L. monocytogenes 4b G. In this mutant, a Tn917 insertion has disrupted the coding region of the gene encoding a putative ATP binding cassette (ABC) transporter permease identical to Lmof2365_1771 (a putative ABC......-transporter permease) presented in the sequenced strain L. monocytogenes str. 4b F2365. This disrupted gene, denoted lm.G_1771, encoded a protein with 10 transmembrane helixes. The revertant, LM-49RE, was obtained by replacing lm.G_1771::Tn917 with lm.G_1771 via homologous recombination. We found that LM-49RE formed...
ABC transporters in CSCs membranes as a novel target for treating tumour relapse
LAURA eZINZI; Marialessandra eContino; Mariangela eCantore; Elena eCapparelli; Marcello eLeopoldo; Nicola Antonio Colabufo
CSCs are responsible for the high rate of recurrence and chemoresistance of different type of cancers. The current antineoplastic agents, able to inhibit bulk replicating cancer cells and radiation treatment, were found inefficacious towards CSCs since this subpopulation has several intrinsic mechanisms of resistance. Among these mechanisms, the expression of ATP-Binding Cassette (ABC) transporters family and the activation of different signaling pathway (such as Wnt/β-catenin signaling, Hedg...
ABC transporters in CSCs membranes as a novel target for treating tumor relapse
Zinzi, Laura; Contino, Marialessandra; Cantore, Mariangela; Capparelli, Elena; Leopoldo, Marcello; Nicola A. Colabufo
CSCs are responsible for the high rate of recurrence and chemoresistance of different types of cancer. The current antineoplastic agents able to inhibit bulk replicating cancer cells and radiation treatment are not efficacious toward CSCs since this subpopulation has several intrinsic mechanisms of resistance. Among these mechanisms, the expression of ATP-Binding Cassette (ABC) transporters family and the activation of different signaling pathways (such as Wnt/β-catenin signaling, Hedgehog, N...
Deoxycytidine kinase modulates the impact of the ABC transporter ABCG2 on clofarabine cytotoxicity
Nagai, Shinjiro; Takenaka, Kazumasa; Nachagari, Deepa; Rose, Charles; Domoney, Kali; Sun, Daxi; Sparreboom, Alex; Schuetz, John D.
Purine nucleoside antimetabolites, such as clofarabine, are effective antileukemic agents. However, their effectiveness depends on an initial activation step in which they are monophosphorylated by deoxycytidine kinase (dCK). Some purine nucleoside antimetabolites and their monophosphate derivatives are exported by the ABC transporter ABCG2. Because clofarabine is a dCK substrate, and we show substantial variation in dCK and ABCG2 in myeloid leukemia, we hypothesized that the activity of dCK ...
CD4+ T cell immunity to the Burkholderia pseudomallei ABC transporter LolC in melioidosis
Chu, Karen K.; Tippayawat, Patcharaporn; Walker, Nicola J.; Harding, Sarah V.; Atkins, Helen S.; Maillere, Bernard; Bancroft, Gregory J; Lertmemongkolchai, Ganjana; Altmann, Daniel M
Burkholderia pseudomallei (Bp) causes melioidosis, a disease with a wide range of possible outcomes, from seroconversion and dormancy to sepsis and death. This spectrum of host-pathogen interactions poses challenging questions about heterogeneity in immunity to Bp. Models show protection to be dependent on CD4+ cells and IFNγ, but little is known about specific target antigens. Having previously implicated the ABC transporter, LolC, in protective immunity, we here use epitope prediction, HLA ...
Effect of selected ABC-drug transporters and anticancer drug disposition in vitro and in vivo
Marchetti, S
Studies described in the thesis that is lying in front of you aim to address the possible implications of selected ABC-drug transporters on the disposition of a number of important anticancer drugs. Although variability in drug disposition has been known for as long as pharmacological studies supported drug development and clinical therapeutics general molecular pharmacological concepts explaining the given interpatient variation in drug disposition have been lacking for many decades. Firm ex...
RLIP76, a non-ABC transporter, and drug resistance in epilepsy
Awasthi Yogesh C; Cucullo Luca; Singhal Sharad S; Fazio Vince; Hallene Kerri L; Awasthi Sanjay; Dini Gabriele; Janigro Damir
Abstract Background Permeability of the blood-brain barrier is one of the factors determining the bioavailability of therapeutic drugs and resistance to chemically different antiepileptic drugs is a consequence of decreased intracerebral accumulation. The ABC transporters, particularly P-glycoprotein, are known to play a role in antiepileptic drug extrusion, but are not by themselves sufficient to fully explain the phenomenon of drug-resistant epilepsy. Proteomic analyses of membrane protein ...
Structural arrangement of the transmission interface in the antigen ABC transport complex TAP
Oancea, Giani; O'Mara, Megan L.; Bennett, W.F. Drew; Tieleman, D. Peter; Abele, Rupert; Tampé, Robert
The transporter associated with antigen processing (TAP) represents a focal point in the immune recognition of virally or malignantly transformed cells by translocating proteasomal degradation products into the endoplasmic reticulum–lumen for loading of MHC class I molecules. Based on a number of experimental data and the homology to the bacterial ABC exporter Sav1866, we constructed a 3D structural model of the core TAP complex and used it to examine the interface between the transmembrane a...
Antitubercular Agent Delamanid and Metabolites as Substrates and Inhibitors of ABC and Solute Carrier Transporters.
Sasabe, Hiroyuki; Shimokawa, Yoshihiko; Shibata, Masakazu; Hashizume, Kenta; Hamasako, Yusuke; Ohzone, Yoshihiro; Kashiyama, Eiji; Umehara, Ken
Delamanid (Deltyba, OPC-67683) is the first approved drug in a novel class of nitro-dihydro-imidazooxazoles developed for the treatment of multidrug-resistant tuberculosis. Patients with tuberculosis require treatment with multiple drugs, several of which have known drug-drug interactions. Transporters regulate drug absorption, distribution, and excretion; therefore, the inhibition of transport by one agent may alter the pharmacokinetics of another, leading to unexpected adverse events. Therefore, it is important to understand how delamanid affects transport activity. In the present study, the potencies of delamanid and its main metabolites as the substrates and inhibitors of various transporters were evaluated in vitro Delamanid was not transported by the efflux ATP-binding cassette (ABC) transporters P-glycoprotein (P-gp; MDR1/ABCB1) and breast cancer resistance protein (BCRP/ABCG2), solute carrier (SLC) transporters, organic anion-transporting polypeptides, or organic cation transporter 1. Similarly, metabolite 1 (M1) was not a substrate for any of these transporters except P-gp. Delamanid showed no inhibitory effect on ABC transporters MDR1, BCRP, and bile salt export pump (BSEP; ABCB11), SLC transporters, or organic anion transporters. M1 and M2 inhibited P-gp- and BCRP-mediated transport but did so only at the 50% inhibitory concentrations (M1, 4.65 and 5.71 μmol/liter, respectively; M2, 7.80 and 6.02 μmol/liter, respectively), well above the corresponding maximum concentration in plasma values observed following the administration of multiple doses in clinical trials. M3 and M4 did not affect the activities of any of the transporters tested. These in vitro data suggest that delamanid is unlikely to have clinically relevant interactions with drugs for which absorption and disposition are mediated by this group of transporters. PMID:27021329
ABC transporters in CSCs membranes as a novel target for treating tumour relapse
LAURA eZINZI
Full Text Available CSCs are responsible for the high rate of recurrence and chemoresistance of different type of cancers. The current antineoplastic agents, able to inhibit bulk replicating cancer cells and radiation treatment, were found inefficacious towards CSCs since this subpopulation has several intrinsic mechanisms of resistance. Among these mechanisms, the expression of ATP-Binding Cassette (ABC transporters family and the activation of different signaling pathway (such as Wnt/β-catenin signaling, Hedgehog, Notch, Akt/PKB are reported. Therefore, considering ABC transporters expression on CSCs membranes, compounds able to modulate MDR could induce cytotoxicity in these cells disclosing an exciting and alternative strategy for targeting CSCs in tumour therapy. The next challenge in the cure of cancer relapse may be a multimodal strategy, an approach in which specific CSCs targeting drugs exert simultaneously the ability to circumvent tumor drug resistance (ABC transporters modulation and cytotoxic activity towards CSCs and the corresponding differentiated tumour cells. The efficacy of suggested multimodal strategy could be probed by using several scaffolds active towards MDR pumps on CSCs isolated by tumour specimens.
The ABC family of multidrug transporters in microorganisms
van Veen, H.W; Konings, W.N
Multidrug transporters are membrane proteins that are able to expel a broad range of toxic molecules from the cell. In humans, the overexpression of the multidrug resistance P-glycoprotein (Pgp) and the multidrug resistance-associated protein MRP1 (MRP) is a principal cause of resistance of cancers
Protein secretion by hybrid bacterial ABC-transporters: specific functions of the membrane ATPase and the membrane fusion protein.
Binet, R; Wandersman, C
The Erwinia chrysanthemi metalloprotease C and the Serratia marcescens haem acquisition protein HasA are both secreted from Gram-negative bacteria by a signal peptide-independent pathway which requires a C-terminal secretion signal and a specific ABC-transporter made up of three proteins: a membrane ATPase (the ABC-protein), a second inner membrane component belonging to the membrane fusion protein family and an outer membrane polypeptide. HasA and protease C transporters are homologous altho...
[Role of ABC efflux transporters in the oral bioavailability and drug-induced intestinal toxicity].
Yokooji, Tomoharu
The gastrointestinal tract is the organ that absorbs nutrients and water from foods and drinks. This organ is often exposed to various harmful xenobiotics, and therefore possesses various detoxification/barrier systems, including metabolizing enzymes and efflux transporters. Intestinal epithelial cells express ATP-binding cassette (ABC) efflux transporters such as P-glycoprotein, multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein, in addition to various solute carrier (SLC) influx transporters. These transporters are expressed site- and membrane-specifically in enterocytes, which affects the bioavailability of ingested substrate drugs. Expression and/or function of transporters can be modulated by various compounds, including therapeutic drugs, herbal products, some foods, and by disease states. The modulation of transporters could cause unexpectedly higher or lower blood concentrations, marked inter- and intra-individual variations in pharmacokinetics, and unreliable pharmacological actions in association with toxicities of substrates. Recently, we found that hyperbilirubinemia, which occurs in some disease states, increased intestinal accumulation and toxicity of methotrexate, an MRP substrate, because of the suppression of MRP function by high plasma concentrations of conjugated bilirubin. We also attempted to ameliorate the intestinal toxicity of irinotecan hydrochloride by modulating the hepatic and intestinal functions of MRP2. This review summarizes our findings regarding the role of ABC transporters, especially MRPs, in oral bioavailability and in drug-induced intestinal toxicity. Our approach to treat intestinal toxicity using an MRP2 modulator is also described. PMID:23811769
ATP-Binding Cassette (ABC) Transporters of the Human Respiratory Tract Pathogen, Moraxella catarrhalis: Role in Virulence.
Murphy, Timothy F; Brauer, Aimee L; Johnson, Antoinette; Kirkham, Charmaine
Moraxella catarrhalis is a human respiratory tract pathogen that causes otitis media (middle ear infections) in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. In view of the huge global burden of disease caused by M. catarrhalis, the development of vaccines to prevent these infections and better approaches to treatment have become priorities. In previous work, we used a genome mining approach that identified three substrate binding proteins (SBPs) of ATP-binding cassette (ABC) transporters as promising candidate vaccine antigens. In the present study, we performed a comprehensive assessment of 19 SBPs of 15 ABC transporter systems in the M. catarrhalis genome by engineering knockout mutants and studying their role in assays that assess mechanisms of infection. The capacity of M. catarrhalis to survive and grow in the nutrient-limited and hostile environment of the human respiratory tract, including intracellular growth, account in part for its virulence. The results show that ABC transporters that mediate uptake of peptides, amino acids, cations and anions play important roles in pathogenesis by enabling M. catarrhalis to 1) grow in nutrient-limited conditions, 2) invade and survive in human respiratory epithelial cells and 3) persist in the lungs in a murine pulmonary clearance model. The knockout mutants of SBPs and ABC transporters showed different patterns of activity in the assay systems, supporting the conclusion that different SBPs and ABC transporters function at different stages in the pathogenesis of infection. These results indicate that ABC transporters are nutritional virulence factors, functioning to enable the survival of M catarrhalis in the diverse microenvironments of the respiratory tract. Based on the role of ABC transporters as virulence factors of M. catarrhalis, these molecules represent potential drug targets to eradicate the organism from the human respiratory tract. PMID:27391026
Mutations in the Arabidopsis Peroxisomal ABC Transporter COMATOSE Allow Differentiation between Multiple Functions In Planta: Insights from an Allelic Series
Dietrich, Daniela; Schmuths, Heike; Lousa, Carine De Marcos; Baldwin, Jocelyn M.; Baldwin, Stephen A.; Baker, Alison; Theodoulou, Frederica L; Holdsworth, Michael J
COMATOSE (CTS), the Arabidopsis homologue of human Adrenoleukodystrophy protein (ALDP), is required for import of substrates for peroxisomal β-oxidation. A new allelic series and a homology model based on the bacterial ABC transporter, Sav1866, provide novel insights into structure-function relations of ABC subfamily D proteins. In contrast to ALDP, where the majority of mutations result in protein absence from the peroxisomal membrane, all CTS mutants produced stable protein. Mutation of con...
Pharmacogenomics of the human ABC transporter ABCG2: from functional evaluation to drug molecular design
Ishikawa, Toshihisa; Tamura, Ai; Saito, Hikaru; Wakabayashi, Kanako; Nakagawa, Hiroshi
In the post-genome-sequencing era, emerging genomic technologies are shifting the paradigm for drug discovery and development. Nevertheless, drug discovery and development still remain high-risk and high-stakes ventures with long and costly timelines. Indeed, the attrition of drug candidates in preclinical and development stages is a major problem in drug design. For at least 30% of the candidates, this attrition is due to poor pharmacokinetics and toxicity. Thus, pharmaceutical companies have begun to seriously re-evaluate their current strategies of drug discovery and development. In that light, we propose that a transport mechanism-based design might help to create new, pharmacokinetically advantageous drugs, and as such should be considered an important component of drug design strategy. Performing enzyme- and/or cell-based drug transporter, interaction tests may greatly facilitate drug development and allow the prediction of drug-drug interactions. We recently developed methods for high-speed functional screening and quantitative structure-activity relationship analysis to study the substrate specificity of ABC transporters and to evaluate the effect of genetic polymorphisms on their function. These methods would provide a practical tool to screen synthetic and natural compounds, and these data can be applied to the molecular design of new drugs. In this review article, we present an overview on the genetic polymorphisms of human ABC transporter ABCG2 and new camptothecin analogues that can circumvent AGCG2-associated multidrug resistance of cancer.
The Heterodimeric ABC Transporter EfrCD Mediates Multidrug Efflux in Enterococcus faecalis.
Hürlimann, Lea M; Corradi, Valentina; Hohl, Michael; Bloemberg, Guido V; Tieleman, D Peter; Seeger, Markus A
Nosocomial infections with Enterococcus faecalis are an emerging health problem. However, drug efflux pumps contributing to intrinsic drug resistance are poorly studied in this Gram-positive pathogen. In this study, we functionally investigated seven heterodimeric ABC transporters of E. faecalis that are annotated as drug efflux pumps. Deletion of ef0789-ef0790 on the chromosome of E. faecalis resulted in increased susceptibility to daunorubicin, doxorubicin, ethidium, and Hoechst 33342, and the corresponding transporter was named EfrCD. Unexpectedly, the previously described heterodimeric multidrug ABC transporter EfrAB contributes marginally to drug efflux in the endogenous context of E. faecalis In contrast, heterologous expression in Lactococcus lactis revealed that EfrAB, EfrCD, and the product of ef2226-ef2227 (EfrEF) mediate the efflux of fluorescent substrates and confer resistance to multiple dyes and drugs, including fluoroquinolones. Four of seven transporters failed to exhibit drug efflux activity for the set of drugs and dyes tested, even upon overexpression in L. lactis Since all seven transporters were purified as heterodimers after overexpression in L. lactis, a lack of drug efflux activity is not attributed to poor expression or protein aggregation. Reconstitution of the purified multidrug transporters EfrAB, EfrCD, and EfrEF in proteoliposomes revealed functional coupling between ATP hydrolysis and drug binding. Our analysis creates an experimental basis for the accurate prediction of drug efflux transporters and indicates that many annotated multidrug efflux pumps might be incapable of drug transport and thus might fulfill other physiological functions in the cell. PMID:27381387
Gene expression of ABC transporters in Cooperia oncophora after field and laboratory selection with macrocyclic lactones.
Tydén, Eva; Skarin, Moa; Höglund, Johan
The most widespread helminth parasites of grazing cattle in northern Europe are the gastrointestinal nematodes Ostertagia ostertagi and Cooperia oncophora. Heavy reliance on the use of macrocyclic lactone (ML) in cattle has led to world-wide emergence of resistance to this drug class in C. oncophora. There is evidence that members of the ATP-binding cassette (ABC) transporter family, such as P-glycoproteins (P-gp) and multidrug-resistant proteins (MRP), play a role in resistance to ML. In this study gene expression of Con-pgp9, Con-pgp11, Con-pgp12, Con-pgp16 and Con-mrp1 was examined in two isolates of C. oncophora sharing the same genetic background but exposed to ML differently. For isolate one (Laboratory-selected), adult worms were recovered before and after treatment with ML in vivo. For isolate two (Field-selected), adult worms were collected from tracer animals that had never received anthelmintics themselves. One group grazed together with untreated animals and one group grazed with animals that received suppressive prophylactic treatment with ML at monthly intervals for up to two consecutive grazing seasons. Real-time PCR data demonstrated differences in gene expression after ML selection, with the highest constitutive expression levels for Con-pgp16 and Con-mrp1. Remarkably, the same pattern of increasing expression levels of the ABC transport genes was observed in both Laboratory- and Field-selected isolates, despite the Field-selected isolate not being directly exposed to ML. The higher expression levels of ABC transporters observed in the Field-selected isolate was thus not a response to direct exposure to ML, but rather appeared to reflect a genetic characteristic inherited from worms in the previous generation which had survived exposure to ML in the co-grazing treated animals. PMID:25619799
The multidrug-resistant phenotype associated with overexpression of the new ABC half-transporter, MXR (ABCG2)
Litman, Thomas; Brangi, M; Hudson, E;
Mechanisms of drug resistance other than P-glycoprotein are of increasing interest as the list of newly identified members of the ABC transport family has grown. We sought to characterize the phenotype of the newly discovered ABC transporter encoded by the mitoxantrone resistance gene, MXR, also...... known as ABCP1 or BCRP. The pharmacodynamics of mitoxantrone and 12 other fluorescent drugs were evaluated by confocal microscopy in four multidrug-resistant human colon (S1) and breast (MCF-7) cancer cell lines. We utilized two sublines, MCF-7 AdVp3000 and S1-M1-80, and detected overexpression of MXR...... studies suggest that the ABC half-transporter, MXR, is a potent, new mechanism for conferring multiple drug resistance. Definition of its mechanism of transport and its role in clinical oncology is required....
Integrated analysis of residue coevolution and protein structure in ABC transporters.
Attila Gulyás-Kovács
Full Text Available Intraprotein side chain contacts can couple the evolutionary process of amino acid substitution at one position to that at another. This coupling, known as residue coevolution, may vary in strength. Conserved contacts thus not only define 3-dimensional protein structure, but also indicate which residue-residue interactions are crucial to a protein's function. Therefore, prediction of strongly coevolving residue-pairs helps clarify molecular mechanisms underlying function. Previously, various coevolution detectors have been employed separately to predict these pairs purely from multiple sequence alignments, while disregarding available structural information. This study introduces an integrative framework that improves the accuracy of such predictions, relative to previous approaches, by combining multiple coevolution detectors and incorporating structural contact information. This framework is applied to the ABC-B and ABC-C transporter families, which include the drug exporter P-glycoprotein involved in multidrug resistance of cancer cells, as well as the CFTR chloride channel linked to cystic fibrosis disease. The predicted coevolving pairs are further analyzed based on conformational changes inferred from outward- and inward-facing transporter structures. The analysis suggests that some pairs coevolved to directly regulate conformational changes of the alternating-access transport mechanism, while others to stabilize rigid-body-like components of the protein structure. Moreover, some identified pairs correspond to residues previously implicated in cystic fibrosis.
Lysimachia foenum-graecum Herba Extract, a Novel Biopesticide, Inhibits ABC Transporter Genes and Mycelial Growth of Magnaporthe oryzae.
Lee, Youngjin
To identify a novel biopesticide controlling rice blast disease caused by Magnaporthe oryzae, 700 plant extracts were evaluated for their inhibitory effects on mycelial growth of M. oryzae. The L. foenum-graecum Herba extract showed the lowest inhibition concentration (IC50) of 39.28 μg/ml, which is lower than the IC50 of blasticidin S (63.06 μg/ml), a conventional fungicide for rice blast disease. When treatments were combined, the IC50 of blasticidin S was dramatically reduced to 10.67 μg/ml. Since ABC transporter genes are involved in fungicide resistance of many organisms, we performed RT-PCR to investigate the transcriptional changes of 40 ABC transporter family genes of M. oryzae treated with the plant extract, blasticidin S, and tetrandrine, a recognized ABC transporter inhibitor. Four ABC transporter genes were prominently activated by blasticidin S treatment, but were suppressed by combinational treatment of blasticidin S with the plant extract, or with tetrandrine that didn't show cellular toxicity by itself in this study. Mycelial death was detected via confocal microscopy at 24 h after plant extract treatment. Finally, subsequent rice field study revealed that the plant extract had high control efficacy of 63.3% and should be considered a biopesticide for rice blast disease. These results showed that extract of L. foenum graecum Herba suppresses M. oryzae ABC transporter genes inducing mycelial death and therefore may be a potent novel biopesticide. PMID:26889110
Toward Determining ATPase Mechanism in ABC Transporters: Development of the Reaction Path–Force Matching QM/MM Method
Zhou, Y.; Ojeda-May, P.; Nagaraju, M.; Pu, J.
Adenosine triphosphate (ATP)-binding cassette (ABC) transporters are ubiquitous ATP-dependent membrane proteins involved in translocations of a wide variety of substrates across cellular membranes. To understand the chemomechanical coupling mechanism as well as functional asymmetry in these systems, a quantitative description of how ABC transporters hydrolyze ATP is needed. Complementary to experimental approaches, computer simulations based on combined quantum mechanical and molecular mechanical (QM/MM) potentials have provided new insights into the catalytic mechanism in ABC transporters. Quantitatively reliable determination of the free energy requirement for enzymatic ATP hydrolysis, however, requires substantial statistical sampling on QM/MM potential. A case study shows that brute force sampling of ab initio QM/MM (AI/MM) potential energy surfaces is computationally impractical for enzyme simulations of ABC transporters. On the other hand, existing semiempirical QM/MM (SE/MM) methods, although affordable for free energy sampling, are unreliable for studying ATP hydrolysis. To close this gap, a multiscale QM/MM approach named reaction path–force matching (RP–FM) has been developed. In RP–FM, specific reaction parameters for a selected SE method are optimized against AI reference data along reaction paths by employing the force matching technique. The feasibility of the method is demonstrated for a proton transfer reaction in the gas phase and in solution. The RP–FM method may offer a general tool for simulating complex enzyme systems such as ABC transporters. PMID:27498639
Toward Determining ATPase Mechanism in ABC Transporters: Development of the Reaction Path-Force Matching QM/MM Method.
Zhou, Y; Ojeda-May, P; Nagaraju, M; Pu, J
Adenosine triphosphate (ATP)-binding cassette (ABC) transporters are ubiquitous ATP-dependent membrane proteins involved in translocations of a wide variety of substrates across cellular membranes. To understand the chemomechanical coupling mechanism as well as functional asymmetry in these systems, a quantitative description of how ABC transporters hydrolyze ATP is needed. Complementary to experimental approaches, computer simulations based on combined quantum mechanical and molecular mechanical (QM/MM) potentials have provided new insights into the catalytic mechanism in ABC transporters. Quantitatively reliable determination of the free energy requirement for enzymatic ATP hydrolysis, however, requires substantial statistical sampling on QM/MM potential. A case study shows that brute force sampling of ab initio QM/MM (AI/MM) potential energy surfaces is computationally impractical for enzyme simulations of ABC transporters. On the other hand, existing semiempirical QM/MM (SE/MM) methods, although affordable for free energy sampling, are unreliable for studying ATP hydrolysis. To close this gap, a multiscale QM/MM approach named reaction path-force matching (RP-FM) has been developed. In RP-FM, specific reaction parameters for a selected SE method are optimized against AI reference data along reaction paths by employing the force matching technique. The feasibility of the method is demonstrated for a proton transfer reaction in the gas phase and in solution. The RP-FM method may offer a general tool for simulating complex enzyme systems such as ABC transporters. PMID:27498639
A single intact ATPase site of the ABC transporter BtuCD drives 5% transport activity yet supports full in vivo vitamin B12 utilization
Tal, Nir; Ovcharenko, Elena; Lewinson, Oded
In all kingdoms of life, ATP binding cassette (ABC) transporters are essential to many cellular functions. In this large superfamily of proteins, two catalytic sites hydrolyze ATP to power uphill substrate translocation. A central question in the field concerns the relationship between the two ATPase catalytic sites: Are the sites independent of one another? Are both needed for function? Do they function cooperatively? These issues have been resolved for type I ABC transporters but never for ...
An asymmetric post-hydrolysis state of the ABC transporter ATPase dimer.
George, Anthony M; Jones, Peter M
ABC transporters are a superfamily of enzyme pumps that hydrolyse ATP in exchange for translocation of substrates across cellular membranes. Architecturally, ABC transporters are a dimer of transmembrane domains coupled to a dimer of nucleotide binding domains (NBDs): the NBD dimer contains two ATP-binding sites at the intersubunit interface. A current controversy is whether the protomers of the NBD dimer separate during ATP hydrolysis cycling, or remain in constant contact. In order to investigate the ABC ATPase catalytic mechanism, MD simulations using the recent structure of the ADP+Pi-bound MJ0796 isolated NBD dimer were performed. In three independent simulations of the ADP+Pi/apo state, comprising a total of >0.5 µs, significant opening of the apo (empty) active site was observed; occurring by way of intrasubunit rotations between the core and helical subdomains within both NBD monomers. In contrast, in three equivalent simulations of the ATP/apo state, the NBD dimer remained close to the crystal structure, and no opening of either active site occurred. The results thus showed allosteric coupling between the active sites, mediated by intrasubunit conformational changes. Opening of the apo site is exquisitely tuned to the nature of the ligand, and thus to the stage of the reaction cycle, in the opposite site. In addition to this, in also showing how one active site can open, sufficient to bind nucleotide, while the opposite site remains occluded and bound to the hydrolysis products ADP+Pi, the results are consistent with a Constant Contact Model. Conversely, they show how there may be no requirement for the NBD protomers to separate to complete the catalytic cycle. PMID:23573213
An asymmetric post-hydrolysis state of the ABC transporter ATPase dimer.
Anthony M George
Full Text Available ABC transporters are a superfamily of enzyme pumps that hydrolyse ATP in exchange for translocation of substrates across cellular membranes. Architecturally, ABC transporters are a dimer of transmembrane domains coupled to a dimer of nucleotide binding domains (NBDs: the NBD dimer contains two ATP-binding sites at the intersubunit interface. A current controversy is whether the protomers of the NBD dimer separate during ATP hydrolysis cycling, or remain in constant contact. In order to investigate the ABC ATPase catalytic mechanism, MD simulations using the recent structure of the ADP+Pi-bound MJ0796 isolated NBD dimer were performed. In three independent simulations of the ADP+Pi/apo state, comprising a total of >0.5 µs, significant opening of the apo (empty active site was observed; occurring by way of intrasubunit rotations between the core and helical subdomains within both NBD monomers. In contrast, in three equivalent simulations of the ATP/apo state, the NBD dimer remained close to the crystal structure, and no opening of either active site occurred. The results thus showed allosteric coupling between the active sites, mediated by intrasubunit conformational changes. Opening of the apo site is exquisitely tuned to the nature of the ligand, and thus to the stage of the reaction cycle, in the opposite site. In addition to this, in also showing how one active site can open, sufficient to bind nucleotide, while the opposite site remains occluded and bound to the hydrolysis products ADP+Pi, the results are consistent with a Constant Contact Model. Conversely, they show how there may be no requirement for the NBD protomers to separate to complete the catalytic cycle.
Pleiotropic effects of the vacuolar ABC transporter MLT1 of Candida albicans on cell function and virulence.
Khandelwal, Nitesh Kumar; Kaemmer, Philipp; Förster, Toni M; Singh, Ashutosh; Coste, Alix T; Andes, David R; Hube, Bernhard; Sanglard, Dominique; Chauhan, Neeraj; Kaur, Rupinder; d'Enfert, Christophe; Mondal, Alok Kumar; Prasad, Rajendra
Among the several mechanisms that contribute to MDR (multidrug resistance), the overexpression of drug-efflux pumps belonging to the ABC (ATP-binding cassette) superfamily is the most frequent cause of resistance to antifungal agents. The multidrug transporter proteins Cdr1p and Cdr2p of the ABCG subfamily are major players in the development of MDR in Candida albicans Because several genes coding for ABC proteins exist in the genome of C. albicans, but only Cdr1p and Cdr2p have established roles in MDR, it is implicit that the other members of the ABC family also have alternative physiological roles. The present study focuses on an ABC transporter of C. albicans, Mlt1p, which is localized in the vacuolar membrane and specifically transports PC (phosphatidylcholine) into the vacuolar lumen. Transcriptional profiling of the mlt1∆/∆ mutant revealed a down-regulation of the genes involved in endocytosis, oxidoreductase activity, virulence and hyphal development. High-throughput MS-based lipidome analysis revealed that the Mlt1p levels affect lipid homoeostasis and thus lead to a plethora of physiological perturbations. These include a delay in endocytosis, inefficient sequestering of reactive oxygen species (ROS), defects in hyphal development and attenuated virulence. The present study is an emerging example where new and unconventional roles of an ABC transporter are being identified. PMID:27026051
Molecular dynamics simulations of the bacterial ABC transporter SAV1866 in the closed form.
St-Pierre, Jean-François; Bunker, Alex; Róg, Tomasz; Karttunen, Mikko; Mousseau, Normand
The ATP binding cassette (ABC) transporter family of proteins contains members involved in ATP-mediated import or export of ligands at the cell membrane. For the case of exporters, the translocation mechanism involves a large-scale conformational change that involves a clothespin-like motion from an inward-facing open state, able to bind ligands and adenosine triphosphate (ATP), to an outward-facing closed state. Our work focuses on SAV1866, a bacterial member of the ABC transporter family for which the structure is known for the closed state. To evaluate the ability of this protein to undergo conformational changes at physiological temperature, we first performed conventional molecular dynamics (MD) on the cocrystallized adenosine diphosphate (ADP)-bound structure and on a nucleotide-free structure. With this assessment of SAV1866's stability, conformational changes were induced by steered molecular dynamics (SMD), in which the nucleotide binding domains (NBD) were pushed apart, simulating the ATP hydrolysis energy expenditure. We found that the transmembrane domain is not easily perturbed by large-scale motions of the NBDs. PMID:22339391
ABC transporters in Mycoplasma hyopneumoniae and Mycoplasma synoviae: insights into evolution and pathogenicity
Marisa Fabiana Nicolás
Full Text Available ABC transporters represent one of the largest superfamilies of active membrane transport proteins (MTPs with a highly conserved ATPase domain that binds and hydrolyzes ATP, supplying energy for the uptake of a variety of nutrients and for the extrusion of drugs and metabolic wastes. The complete genomes of a non-pathogenic (J and pathogenic (7448 strain of Mycoplasma hyopneumoniae, as well as of a pathogenic (53 strain of Mycoplasma synoviae have been recently sequenced. A detailed study revealed a high percentage of CDSs encoding MTPs in M. hyopneumoniae strains J (13.4%, 7448 (13.8%, and in M. synoviae 53 (11.2%, and the ABC systems represented from 85.0 to 88.6% of those CDSs. Uptake systems are mainly involved in cell nutrition and some might be associated with virulence. Exporter systems include both drug and multidrug resistant systems (MDR, which may represent mechanisms of resistance to toxic molecules. No relation was found between the phylogeny of the ATPase domains and the lifestyle or pathogenicity of Mycoplasma, but several proteins, potentially useful as targets for the control of infections, were identified.
1.55 Å Structure of the Ectoine Binding Protein TeaA of the Osmoregulated TRAP-Transporter TeaABC from Halomonas elongata
Kuhlmann, Sonja I.; Terwisscha van Scheltinga, Anke C; Bienert, Ralf; Kunte, Hans-Jörg; Ziegler, Christine
TeaABC from the moderate halophilic bacterium Halomonas elongata belongs to the tripartite ATP-independent periplasmic transporters (TRAP-T), a family of secondary transporters functioning in conjunction with periplasmic substrate binding proteins. TeaABC facilitates the uptake of the compatible solutes ectoine and hydroxyectoine that are accumulated in the cytoplasm under hyperosmotic stress to protect the cell from dehydration. TeaABC is the only known TRAP-T activated by osmotic stress. Cu...
Using mass spectrometry for identification of ABC transporters from Xanthomonas citri and mutants expressed in different growth conditions
Faria, J.N.; Balan, A. [Laboratorio Nacional de Biociencias - LNBIO, Campinas, SP (Brazil); Paes Leme, A.F. [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil)
Full text: Xanthomonas citri is a phytopathogenic bacterium that infects citrus plants causing significant losses for the economy. In our group, we have focused on the identification and characterization of ABC transport proteins of this bacterium, in order to determinate their function for growth in vitro and in vivo, during infection. ABC transporters represent one of the largest families of proteins, which transport since small molecules as ions up to oligopeptides and sugars. In prokaryotic cells many works have reported the ABC transport function in pathogenesis, resistance, biofilm formation, infectivity and DNA repair, but until our knowledge, there is no data related to these transporters and X. citri. So, In order to determinate which transporters are expressed in X. citri, we started a proteomic analysis based on mono and bi-dimensional gels associated to mass spectrometry analyses. After growing X. citri and two different mutants deleted for ssuA and nitA genes in LB and minimum media, cellular extracts were obtained and used for preparation of mono and bi-dimensional gels. Seven bands covering the expected mass of ABC transporter components (20 kDa to 50 kDa) in SDS-PAGE were cut off the gel, treated with trypsin and submitted to the MS for protein identification. The results of 2D gels were good enough and will serve as a standard for development of similar experiments in large scale. (author)
Using mass spectrometry for identification of ABC transporters from Xanthomonas citri and mutants expressed in different growth conditions
Full text: Xanthomonas citri is a phytopathogenic bacterium that infects citrus plants causing significant losses for the economy. In our group, we have focused on the identification and characterization of ABC transport proteins of this bacterium, in order to determinate their function for growth in vitro and in vivo, during infection. ABC transporters represent one of the largest families of proteins, which transport since small molecules as ions up to oligopeptides and sugars. In prokaryotic cells many works have reported the ABC transport function in pathogenesis, resistance, biofilm formation, infectivity and DNA repair, but until our knowledge, there is no data related to these transporters and X. citri. So, In order to determinate which transporters are expressed in X. citri, we started a proteomic analysis based on mono and bi-dimensional gels associated to mass spectrometry analyses. After growing X. citri and two different mutants deleted for ssuA and nitA genes in LB and minimum media, cellular extracts were obtained and used for preparation of mono and bi-dimensional gels. Seven bands covering the expected mass of ABC transporter components (20 kDa to 50 kDa) in SDS-PAGE were cut off the gel, treated with trypsin and submitted to the MS for protein identification. The results of 2D gels were good enough and will serve as a standard for development of similar experiments in large scale. (author)
ABC transporters affect the elimination and toxicity of CdTe quantum dots in liver and kidney cells.
Chen, Mingli; Yin, Huancai; Bai, Pengli; Miao, Peng; Deng, Xudong; Xu, Yingxue; Hu, Jun; Yin, Jian
This paper aimed to investigate the role of adenosine triphosphate-binding cassette (ABC) transporters on the efflux and the toxicity of nanoparticles in liver and kidney cells. In this study, we synthesized CdTe quantum dots (QDs) that were monodispersed and emitted green fluorescence (maximum peak at 530nm). Such QDs tended to accumulate in human hepatocellular carcinoma cells (HepG2), human kidney cells 2 (HK-2), and Madin-Darby canine kidney (MDCK) cells, and cause significant toxicity in all the three cell lines. Using specific inhibitors and inducers of P-glycoprotein (Pgp) and multidrug resistance associated proteins (Mrps), the cellular accumulation and subsequent toxicity of QDs in HepG2 and HK-2 cells were significantly affected, while only slight changes appeared in MDCK cells, corresponding well with the functional expressions of ABC transporters in cells. Moreover, treatment of QDs caused concentration- and time- dependent induction of ABC transporters in HepG2 and HK-2 cells, but such phenomenon was barely found in MDCK cells. Furthermore, the effects of CdTe QDs on ABC transporters were found to be greater than those of CdCl2 at equivalent concentrations of cadmium, indicating that the effects of QDs should be a combination of free Cd(2+) and specific properties of QDs. Overall, these results indicated a strong dependence between the functional expressions of ABC transporters and the efflux of QDs, which could be an important reason for the modulation of QDs toxicity by ABC transporters. PMID:27131644
Genome-wide analysis of the ATP-binding cassette (ABC) transporter gene family in the silkworm, Bombyx mori.
Xie, Xiaodong; Cheng, Tingcai; Wang, Genhong; Duan, Jun; Niu, Weihuan; Xia, Qingyou
The ATP-binding cassette (ABC) superfamily is a larger protein family with diverse physiological functions in all kingdoms of life. We identified 53 ABC transporters in the silkworm genome, and classified them into eight subfamilies (A-H). Comparative genome analysis revealed that the silkworm has an expanded ABCC subfamily with more members than Drosophila melanogaster, Caenorhabditis elegans, or Homo sapiens. Phylogenetic analysis showed that the ABCE and ABCF genes were highly conserved in the silkworm, indicating possible involvement in fundamental biological processes. Five multidrug resistance-related genes in the ABCB subfamily and two multidrug resistance-associated-related genes in the ABCC subfamily indicated involvement in biochemical defense. Genetic variation analysis revealed four ABC genes that might be evolving under positive selection. Moreover, the silkworm ABCC4 gene might be important for silkworm domestication. Microarray analysis showed that the silkworm ABC genes had distinct expression patterns in different tissues on day 3 of the fifth instar. These results might provide new insights for further functional studies on the ABC genes in the silkworm genome. PMID:22311044
Inhibition of ABC transport proteins by oil sands process affected water.
Alharbi, Hattan A; Saunders, David M V; Al-Mousa, Ahmed; Alcorn, Jane; Pereira, Alberto S; Martin, Jonathan W; Giesy, John P; Wiseman, Steve B
The ATP-binding cassette (ABC) superfamily of transporter proteins is important for detoxification of xenobiotics. For example, ABC transporters from the multidrug-resistance protein (MRP) subfamily are important for excretion of polycyclic aromatic hydrocarbons (PAHs) and their metabolites. Effects of chemicals in the water soluble organic fraction of relatively fresh oil sands process affected water (OSPW) from Base Mine Lake (BML-OSPW) and aged OSPW from Pond 9 (P9-OSPW) on the activity of MRP transporters were investigated in vivo by use of Japanese medaka at the fry stage of development. Activities of MRPs were monitored by use of the lipophilic dye calcein, which is transported from cells by ABC proteins, including MRPs. To begin to identify chemicals that might inhibit activity of MRPs, BML-OSPW and P9-OSPW were fractionated into acidic, basic, and neutral fractions by use of mixed-mode sorbents. Chemical compositions of fractions were determined by use of ultrahigh resolution orbitrap mass spectrometry in ESI(+) and ESI(-) mode. Greater amounts of calcein were retained in fry exposed to BML-OSPW at concentration equivalents greater than 1× (i.e., full strength). The neutral and basic fractions of BML-OSPW, but not the acidic fraction, caused greater retention of calcein. Exposure to P9-OSPW did not affect the amount of calcein in fry. Neutral and basic fractions of BML-OSPW contained relatively greater amounts of several oxygen-, sulfur, and nitrogen-containing chemical species that might inhibit MRPs, such as O(+), SO(+), and NO(+) chemical species, although secondary fractionation will be required to conclusively identify the most potent inhibitors. Naphthenic acids (O2(-)), which were dominant in the acidic fraction, did not appear to be the cause of the inhibition. This is the first study to demonstrate that chemicals in the water soluble organic fraction of OSPW inhibit activity of this important class of proteins. However, aging of OSPW attenuates
1.55 Å Structure of the Ectoine Binding Protein TeaA of the Osmoregulated TRAP-Transporter TeaABC from Halomonas elongata
Kuhlmann, Sonja I.; Terwisscha van Scheltinga, Anke C.; Bienert, Ralf; Kunte, Hans-Jörg; Ziegler, Christine
TeaABC from the moderate halophilic bacterium Halomonas elongata belongs to the tripartite ATP-independent periplasmic transporters (TRAP-T), a family of secondary transporters functioning in conjunction with periplasmic substrate binding proteins. TeaABC facilitates the uptake of the compatible sol
ABC- and SLC-Transporters in Murine and Bovine Mammary Epithelium - Effects of Prochloraz
Yagdiran, Yagmur; Oskarsson, Agneta; Knight, Christopher H.; Tallkvist, Jonas
Some chemicals are ligands to efflux transporters which may result in high concentrations in milk. Limited knowledge is available on the influence of maternal exposure to chemicals on the expression and function of transporters in the lactating mammary gland. We determined gene expression of ABC and SLC transporters in murine mammary tissue of different gestation and lactation stages, in murine mammary cells (HC11) featuring resting and secreting phenotypes and in bovine mammary tissue and cells (BME-UV). Effects on transporter expression and function of the imidazole fungicide prochloraz, previously reported to influence BCRP in mammary cells, was investigated on transporter expression and function in the two cell lines. Transporters studied were BCRP, MDR1, MRP1, OATP1A5/OATP1A2, OCTN1 and OCT1. Gene expressions of BCRP and OCT1 in murine mammary glands were increased during gestation and lactation, whereas MDR1, MRP1, OATP1A5 and OCTN1 were decreased, compared to expressions in virgins. All transporters measured in mammary glands of mice were detected in bovine mammary tissue and in HC11 cells, while only MDR1 and MRP1 were detected in BME-UV cells. Prochloraz treatment induced MDR1 gene and protein expression in both differentiated HC11 and BME-UV cells and increased protein function in HC11 cells, resulting in decreased accumulation of the MDR1 substrate digoxin. In conclusion, our results demonstrate that murine (HC11) and bovine (BME-UV) mammary epithelial cells can be applied to characterize expression and function of transporters as well as effects of contaminants on the mammary transporters. An altered expression, induced by a drug or toxic chemical, on any of the transporters expressed in the mammary epithelial cells during lactation may modulate the well-balanced composition of nutrients and/or secretion of contaminants in milk with potential adverse effects on breast-fed infants and dairy consumers. PMID:27028005
A Bacitracin-Resistant Bacillus subtilis Gene Encodes a Homologue of the Membrane-Spanning Subunit of the Bacillus licheniformis ABC Transporter
Ohki, Reiko; Tateno, Kozue; Okada, Youji; Okajima, Haruo; Asai, Kei; Sadaie, Yoshito; Murata, Makiko; Aiso, Toshiko
Bacitracin is a peptide antibiotic nonribosomally produced by Bacillus licheniformis. The bcrABC genes which confer bacitracin resistance to the bacitracin producer encode ATP binding cassette (ABC) transporter proteins, which are hypothesized to pump out bacitracin from the cells. Bacillus subtilis 168, which has no bacitracin synthesizing operon, has several genes homologous to bcrABC. It was found that the disruption of ywoA, a gene homologous to bcrC, resulted in hypersensitivity to bacit...
Homologous Expression of the Lipase and ABC Transporter Gene Cluster, tliDEFA, Enhances Lipase Secretion in Pseudomonas spp.
Ahn, Jung Hoon; Pan, Jae Gu; Rhee, Joon Shick
The ABC transporter TliDEF was found to be an efficient secretory apparatus for extracellular lipase TliA in Pseudomonas fluorescens. For the enhanced secretion of the lipase, we tried to coexpress tliA and tliDEF in various Pseudomonas species. Whereas the coexpression of tliA and tliDEF was required for the lipase secretion in P. fragi, the expression of tliA was sufficient for the lipase secretion in P. fluorescens, P. syringae, and P. putida, indicating the existence of compatible ABC tra...
Imaging of ABC transporters with positron emission tomography – new insights from the development of new radiotracers
Adenosine triphosphate-binding cassette (ABC) transporters, such as P-glycoprotein (Pgp), breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 1 (MRP1), form through their ability to transport a multitude of chemically unrelated compounds across cellular membranes a powerful physiological defense system which protects the body from exposure to xenobiotics. Historically, ABC transporters have been implicated in multidrug resistance (MDR) in cancer, but more recent evidence suggests that changes in ABC transporter function and expression at the blood-brain barrier (BBB) occur in several neurological disorders, such as epilepsy, Alzheimer's and Parkinson's disease. To better understand the role of ABC transporters in disease a tool is needed to assess their function and expression in-vivo. The nuclear imaging technique positron emission tomography (PET), which enables measurement of tissue concentration levels of radiolabeled compounds, has great potential for studying ABC transporters in-vivo, provided the availability of suitable radiotracers and imaging protocols. In this thesis the interaction of new radiotracers with Pgp and BCRP was investigated in order to assess their suitability for PET imaging. The radiolabeled Pgp inhibitors [11C]tariquidar and [11C]elacridar had been initially developed to visualize Pgp density at the BBB but had failed to provide useful, quantifiable brain PET signals. In this thesis, the suitability of [11C]tariquidar and [11C]elacridar to visualize Pgp density in tumors was investigated. An experimental murine tumor model comprising a wild-type and a Pgp overexpressing variant was developed and binding characteristics of [11C]tariquidar and [11C]elacridar as well as two other newly developed PET tracers ([11C]MC113 and [11C]HM30181) were systematically evaluated. These studies showed, that contrary to the BBB, radiolabeled Pgp inhibitors were able to assess Pgp density in tumors, which may find
ABC transporter functions as a pacemaker for sequestration of plant glucosides in leaf beetles.
Strauss, Anja S; Peters, Sven; Boland, Wilhelm; Burse, Antje
Plant-herbivore interactions dominate the planet's terrestrial ecology. When it comes to host-plant specialization, insects are among the most versatile evolutionary innovators, able to disarm multiple chemical plant defenses. Sequestration is a widespread strategy to detoxify noxious metabolites, frequently for the insect's own benefit against predation. In this study, we describe the broad-spectrum ATP-binding cassette transporter CpMRP of the poplar leaf beetle, Chrysomela populi as the first candidate involved in the sequestration of phytochemicals in insects. CpMRP acts in the defensive glands of the larvae as a pacemaker for the irreversible shuttling of pre-selected metabolites from the hemolymph into defensive secretions. Silencing CpMRP in vivo creates a defenseless phenotype, indicating its role in the secretion process is crucial. In the defensive glands of related leaf beetle species, we identified sequences similar to CpMRP and assume therefore that exocrine gland-based defensive strategies, evolved by these insects to repel their enemies, rely on ABC transporters as a key element. DOI: http://dx.doi.org/10.7554/eLife.01096.001. PMID:24302568
Phenotypic, Proteomic, and Genomic Characterization of a Putative ABC-Transporter Permease Involved in Listeria monocytogenes Biofilm Formation
Zhu, Xinna; Liu, Weibing; Lametsch, René;
The foodborne pathogen Listeria monocytogenes is able to form biofilms in food processing environments. Previously, we have reported that an lm.G_1771 gene (encoding a putative ABC-transporter permease) was involved in negative regulation of L. monocytogenes biofilm formation using LM-49, a biofilm......-enhanced mutant isolated on Tn917 mutagenesis (AEM 2008 p.7675–7683). Here, the possible action of this ABC-transporter permease in L. monocytogenes biofilm formation was characterized by phenotypic, proteomic, and genomic analyses using an lm.G_1771 gene deletant (Δ1771). The Δ1771 mutant exhibited the same...... enhanced ability for biofilm formation as the LM-49 strain using a crystal violet staining assay. DNA microarrays and two-dimensional gel electrophoresis revealed 49 and 11 differentially expressed (twofold or more) genes or proteins in Δ1771, respectively. The transcriptomics study indicated that lm...
Pharmacogenetics of human ABC transporter ABCC11:new insights into apocrine gland growth and metabolite secretion
Toshihisa eIshikawa
Full Text Available Cell secretion is an important physiological process that ensures smooth metabolic activities and tissue repair as well as growth and immunological functions in the body. Apocrine secretion occurs when the secretory process is accomplished with a partial loss of cell cytoplasm. The secretory materials are contained within secretory vesicles and are released during secretion as cytoplasmic fragments into the glandular lumen or interstitial space. The recent finding that the nonsynonymous SNP 538G>A (rs17822931; Gly180Arg in the ABCC11 gene determines the type of earwax in humans has shed light on the novel function of this ABC transporter in apocrine glands. The wild type (Gly180 of ABCC11 is associated with wet-type earwax, axillary osmidrosis, and colostrum secretion from the mammary gland as well as the potential risk of mastopathy. Furthermore, the SNP (538G>A in the ABCC11 gene is suggested to be a clinical biomarker for the prediction of chemotherapeutic efficacy. The aim of this review article is to provide an overview on the discovery and characterization of genetic polymorphisms in the human ABCC11 gene and to explain the impact of ABCC11 538G>A on the apocrine phenotype as well as the anthropological aspect of this SNP in the ABCC11 gene and patients' response to nucleoside-based chemotherapy.
Lysophosphatidylinositol: a novel link between ABC transporters and G-protein-coupled receptors.
Ruban, Emily L; Ferro, Riccardo; Arifin, Syamsul Ahmad; Falasca, Marco
Lysophosphatidylinositol (LPI) is a well-known bioactive lipid that is able to activate signalling cascades relevant to cell proliferation, migration, survival and tumorigenesis. Our previous work suggested that LPI is involved in cancer progression since it can be released in the medium of Ras-transformed fibroblasts and can function as an autocrine modulator of cell growth. Different research groups have established that LPI is the specific and functional ligand for G-protein-coupled receptor 55 (GPR55) and that this GPR55-LPI axis is able to activate signalling cascades that are relevant for different cell functions. Work in our laboratory has recently unravelled an autocrine loop, by which LPI synthesized by cytosolic phospholipase A₂ (cPLA₂) is pumped out of the cell by ATP-binding cassette (ABC) transporter C1 (ABCC1)/multidrug resistance protein 1 (MRP1), initiating a signalling cascade downstream of GPR55. Our current work suggests that blockade of this pathway may represent a novel strategy to inhibit cancer cell proliferation. PMID:25233417
Identification and characterization of an iron ABC transporter operon in Gluconacetobacter diazotrophicus Pal 5.
Urzúa, Lucia Soto; Vázquez-Candanedo, Ada P; Sánchez-Espíndola, Adriana; Ramírez, Carlos Ávila; Baca, Beatriz E
Gluconacetobacter diazotrophicus is a nitrogen-fixing bacterium and endophyte of sugarcane. We have cloned and sequenced the genes coding for the components of the iron ABC-type acquisition system of G. diazotrophicus. Sequence analysis revealed three ORFs, (feuA, feuB, and feuC) organized as an operon and encoding polypeptides of 346 (38 kDa), 342 (34.2 kDa), and 240 (26 kDa) amino acids, respectively. The deduced translation products of the feu operon showed similarity with a periplasmic solute-binding protein (FeuA), permease (FeuB), and ATPase (FeuC) involved in Fe transport. The role of FeuB in the survival of G. diazotrophicus under iron depletion was evaluated by comparing the ability of wild-type and FeuB-Km(R) -mutant strains in a medium without iron supplementation and in a medium containing 2, 2'-dipyridyl (DP). Growth of the mutant was affected in the medium containing DP. The operon was expressed at higher levels in cells depleted for iron than in those that contained the metal. A decrease in nitrogenase activity was observed with the FeuB-Km(R) -mutant strain that with the wild-type under iron deficiency conditions, suggesting that the Feu operon play role in Fe nutrition of G. diazotrophicus. PMID:23624722
Crystal structure of the phosphate-binding protein (PBP-1) of an ABC-type phosphate transporter from Clostridium perfringens
Gonzalez, Daniel; Richez, Magali; Bergonzi, Celine; Chabriere, Eric; Elias, Mikael
Phosphate limitation is an important environmental stress that affects the metabolism of various organisms and, in particular, can trigger the virulence of numerous bacterial pathogens. Clostridium perfringens, a human pathogen, is one of the most common causes of enteritis necroticans, gas gangrene and food poisoning. Here, we focused on the high affinity phosphate-binding protein (PBP-1) of an ABC-type transporter, responsible for cellular phosphate uptake. We report the crystal structure (...
A two-component system regulates the expression of an ABC transporter for xylo-oligosaccharides in Geobacillus stearothermophilus.
Shulami, Smadar; Zaide, Galia; Zolotnitsky, Gennady; Langut, Yael; Feld, Geoff; Sonenshein, Abraham L; Shoham, Yuval
Geobacillus stearothermophilus T-6 utilizes an extensive and highly regulated hemicellulolytic system. The genes comprising the xylanolytic system are clustered in a 39.7-kb chromosomal segment. This segment contains a 6-kb transcriptional unit (xynDCEFG) coding for a potential two-component system (xynDC) and an ATP-binding cassette (ABC) transport system (xynEFG). The xynD promoter region contains a 16-bp inverted repeat resembling the operator site for the xylose repressor, XylR. XylR was found to bind specifically to this sequence, and binding was efficiently prevented in vitro in the presence of xylose. The ABC transport system was shown to comprise an operon of three genes (xynEFG) that is transcribed from its own promoter. The nonphosphorylated fused response regulator, His6-XynC, bound to a 220-bp fragment corresponding to the xynE operator. DNase I footprinting analysis showed four protected zones that cover the -53 and the +34 regions and revealed direct repeat sequences of a GAAA-like motif. In vitro transcriptional assays and quantitative reverse transcription-PCR demonstrated that xynE transcription is activated 140-fold in the presence of 1.5 microM XynC. The His6-tagged sugar-binding lipoprotein (XynE) of the ABC transporter interacted with different xylosaccharides, as demonstrated by isothermal titration calorimetry. The change in the heat capacity of binding (DeltaCp) for XynE with xylotriose suggests a stacking interaction in the binding site that can be provided by a single Trp residue and a sugar moiety. Taken together, our data show that XynEFG constitutes an ABC transport system for xylo-oligosaccharides and that its transcription is negatively regulated by XylR and activated by the response regulator XynC, which is part of a two-component sensing system. PMID:17142383
Mutational Analysis of Intracellular Loops Identify Cross Talk with Nucleotide Binding Domains of Yeast ABC Transporter Cdr1p
Shah, Abdul Haseeb; Rawal, Manpreet Kaur; Dhamgaye, Sanjiveeni; Komath, Sneha Sudha; Saxena, Ajay Kumar; Prasad, Rajendra
The ABC transporter Cdr1 protein (Cdr1p) of Candida albicans, which plays a major role in antifungal resistance, has two transmembrane domains (TMDs) and two nucleotide binding domains (NBDs) that are interconnected by extracellular (ECLs) and intracellular (ICLs) loops. To examine the communication interface between the NBDs and ICLs of Cdr1p, we subjected all four ICLs to alanine scanning mutagenesis, replacing each of the 85 residues with an alanine. The resulting ICL mutant library was an...
The ABC transporter BcatrB from Botrytis cinerea exports camalexin and is a virulence factor on Arabidopsis thaliana
Stefanato, Francesca L.; Abou-Mansour, Eliane; Buchala, Antony; Kretschmer, Matthias; Mosbach, Andreas; Hahn, Matthias; Bochet, Christian G.; Métraux, Jean-Pierre; Schoonbeek, Henk-jan
Arabidopsis thaliana is known to produce the phytoalexin camalexin in response to abiotic and biotic stress. Here we studied the mechanisms of tolerance to camalexin in the fungus Botrytis cinerea, a necrotrophic pathogen of A. thaliana. Exposure of B. cinerea to camalexin induces expression of BcatrB, an ABC transporter that functions in the efflux of fungitoxic compounds. B. cinerea inoculated on wild-type A. thaliana plants yields smaller lesions than on camalexin-deficient A. thaliana mut...
Identification of the tliDEF ABC Transporter Specific for Lipase in Pseudomonas fluorescens SIK W1
Ahn, Jung Hoon; Pan, Jae Gu; Rhee, Joon Shick
Pseudomonas fluorescens, a gram-negative psychrotrophic bacterium, secretes a thermostable lipase into the extracellular medium. In our previous study, the lipase of P. fluorescens SIK W1 was cloned and expressed in Escherichia coli, but it accumulated as inactive inclusion bodies. Amino acid sequence analysis of the lipase revealed a potential C-terminal targeting sequence recognized by the ATP-binding cassette (ABC) transporter. The genetic loci around the lipase gene were searched, and a s...
Role of ABC and Solute Carrier Transporters in the Placental Transport of Lamivudine.
Ceckova, Martina; Reznicek, Josef; Ptackova, Zuzana; Cerveny, Lukas; Müller, Fabian; Kacerovsky, Marian; Fromm, Martin F; Glazier, Jocelyn D; Staud, Frantisek
Lamivudine is one of the antiretroviral drugs of choice for the prevention of mother-to-child transmission (MTCT) in HIV-positive women. In this study, we investigated the relevance of drug efflux transporters P-glycoprotein (P-gp) (MDR1 [ABCB1]), BCRP (ABCG2), MRP2 (ABCC2), and MATE1 (SLC47A1) for the transmembrane transport and transplacental transfer of lamivudine. We employed in vitro accumulation and transport experiments on MDCK cells overexpressing drug efflux transporters, in situ-perfused rat term placenta, and vesicular uptake in microvillous plasma membrane (MVM) vesicles isolated from human term placenta. MATE1 significantly accelerated lamivudine transport in MATE1-expressing MDCK cells, whereas no transporter-driven efflux of lamivudine was observed in MDCK-MDR1, MDCK-MRP2, and MDCK-BCRP monolayers. MATE1-mediated efflux of lamivudine appeared to be a low-affinity process (apparent Km of 4.21 mM and Vmax of 5.18 nmol/mg protein/min in MDCK-MATE1 cells). Consistent with in vitro transport studies, the transplacental clearance of lamivudine was not affected by P-gp, BCRP, or MRP2. However, lamivudine transfer across dually perfused rat placenta and the uptake of lamivudine into human placental MVM vesicles revealed pH dependency, indicating possible involvement of MATE1 in the fetal-to-maternal efflux of the drug. To conclude, placental transport of lamivudine does not seem to be affected by P-gp, MRP2, or BCRP, but a pH-dependent mechanism mediates transport of lamivudine in the fetal-to-maternal direction. We suggest that MATE1 might be, at least partly, responsible for this transport. PMID:27401571
Increased expression of the yeast multidrug resistance ABC transporter Pdr18 leads to increased ethanol tolerance and ethanol production in high gravity alcoholic fermentation
Teixeira Miguel C; Godinho Cláudia P; Cabrito Tânia R; Mira Nuno P; Sá-Correia Isabel
Abstract Background The understanding of the molecular basis of yeast tolerance to ethanol may guide the design of rational strategies to increase process performance in industrial alcoholic fermentations. A set of 21 genes encoding multidrug transporters from the ATP-Binding Cassette (ABC) Superfamily and Major Facilitator Superfamily (MFS) in S. cerevisiae were scrutinized for a role in ethanol stress resistance. Results A yeast multidrug resistance ABC transporter encoded by the PDR18 gene...
Active transmembrane drug transport in microgravity: a validation study using an ABC transporter model [v1; ref status: indexed, http://f1000r.es/41n
Sergi Vaquer
Full Text Available Abstract Microgravity has been shown to influence the expression of ABC (ATP-Binding Cassette transporters in bacteria, fungi and mammals, but also to modify the activity of certain cellular components with structural and functional similarities to ABC transporters. Changes in activity of ABC transporters could lead to important metabolic disorders and undesired pharmacological effects during spaceflights. However, no current means exist to study the functionality of these transporters in microgravity. To this end, a Vesicular Transport Assay® (Solvo Biotechnology, Hungary was adapted to evaluate multi-drug resistance-associated protein 2 (MRP2 trans-membrane estradiol-17-β-glucuronide (E17βG transport activity, when activated by adenosine-tri-phosphate (ATP during parabolic flights. Simple diffusion, ATP-independent transport and benzbromarone inhibition were also evaluated. A high accuracy engineering system was designed to perform, monitor and synchronize all procedures. Samples were analysed using a validated high sensitivity drug detection protocol. Experiments were performed in microgravity during parabolic flights, and compared to 1g on ground results using identical equipment and procedures in all cases. Our results revealed that sufficient equipment accuracy and analytical sensitivity were reached to detect transport activity in both gravitational conditions. Additionally, transport activity levels of on ground samples were within commercial transport standards, proving the validity of the methods and equipment used. MRP2 net transport activity was significantly reduced in microgravity, so was signal detected in simple diffusion samples. Ultra-structural changes induced by gravitational stress upon vesicle membranes or transporters could explain the current results, although alternative explanations are possible. Further research is needed to provide a conclusive answer in this regard. Nevertheless, the present validated technology
The Schizosaccharomyces pombe mam1 gene encodes an ABC transporter mediating secretion of M-factor
Christensen, P U; Davey, William John; Nielsen, O;
In the fission yeast Schizosaccharomyces pombe, cells of opposite mating type communicate via diffusible peptide pheromones prior to mating. We have cloned the S. pombe mam1 gene, which encodes a 1336-amino acid protein belonging to the ATP-binding cassette (ABC) superfamily. The mam1 gene is onl...
Tivantinib (ARQ 197) exhibits antitumor activity by directly interacting with tubulin and overcomes ABC transporter-mediated drug resistance.
Aoyama, Aki; Katayama, Ryohei; Oh-Hara, Tomoko; Sato, Shigeo; Okuno, Yasushi; Fujita, Naoya
Tivantinib (ARQ197) was first reported as a highly selective inhibitor of c-MET and is currently being investigated in a phase III clinical trial. However, as recently reported by us and another group, tivantinib showed cytotoxic activity independent of cellular c-MET status and also disrupted microtubule dynamics. To investigate if tivantinib exerts its cytotoxic activity by disrupting microtubules, we quantified polymerized tubulin in cells and xenograft tumors after tivantinib treatment. Consistent with our previous report, tivantinib reduced tubulin polymerization in cells and in mouse xenograft tumors in vivo. To determine if tivantinib directly binds to tubulin, we performed an in vitro competition assay. Tivantinib competitively inhibited colchicine but not vincristine or vinblastine binding to purified tubulin. These results imply that tivantinib directly binds to the colchicine binding site of tubulin. To predict the binding mode of tivantinib with tubulin, we performed computer simulation of the docking pose of tivantinib with tubulin using GOLD docking program. Computer simulation predicts tivantinib fitted into the colchicine binding pocket of tubulin without steric hindrance. Furthermore, tivantinib showed similar IC50 values against parental and multidrug-resistant cells. In contrast, other microtubule-targeting drugs, such as vincristine, paclitaxel, and colchicine, could not suppress the growth of cells overexpressing ABC transporters. Moreover, the expression level of ABC transporters did not correlate with the apoptosis-inducing ability of tivantinib different from other microtubule inhibitor. These results suggest that tivantinib can overcome ABC transporter-mediated multidrug-resistant tumor cells and is potentially useful against various tumors. PMID:25313010
The ABC transporter ABCG29 is involved in H2O2 tolerance and biocontrol traits in the fungus Clonostachys rosea.
Dubey, Mukesh; Jensen, Dan Funck; Karlsson, Magnus
For successful biocontrol interactions, biological control organisms must tolerate toxic metabolites produced by themselves or plant pathogens during mycoparasitic/antagonistic interactions, by host plant during colonization of the plant, and xenobiotics present in the environment. ATP-binding cassette (ABC) transporters can play a significant role in tolerance of toxic compounds by mediating active transport across the cellular membrane. This paper reports on functional characterization of an ABC transporter ABCG29 in the biocontrol fungus Clonostachys rosea strain IK726. Gene expression analysis showed induced expression of abcG29 during exposure to the Fusarium spp. mycotoxin zearalenone (ZEA) and the fungicides Cantus, Chipco Green and Apron. Expression of abcG29 in C. rosea was significantly higher during C. rosea-C. rosea (Cr-Cr) interaction or in exposure to C. rosea culture filtrate for 2 h, compared to interaction with Fusarium graminearum or 2 h exposure to F. graminearum culture filtrate. In contrast with gene expression data, ΔabcG29 strains did not display reduced tolerance towards ZEA, fungicides or chemical agents known for inducing oxidative, cell wall or osmotic stress, compared to C. rosea WT. The exception was a significant reduction in tolerance to H2O2 (10 mM) in ΔabcG29 strains when conidia were used as an inoculum. The antagonistic ability of ΔabcG29 strains towards F. graminearum, Fusarium oxysporum or Botrytis cinerea in dual plate assays were not different compared with WT. However, in biocontrol assays ΔabcG29 strains displayed reduced ability to protect Arabidopsis thaliana leaves from B. cinerea, and barley seedling from F. graminearum as measured by an A. thaliana detached leaf assay and a barley foot rot disease assay, respectively. These data show that the ABCG29 is dispensable for ZEA and fungicides tolerance, and antagonism but not H2O2 tolerance and biocontrol effects in C. rosea. PMID:26520102
Heme Transfer from Streptococcal Cell Surface Protein Shp to HtsA of Transporter HtsABC
Liu, Mengyao; Lei, Benfang
Human pathogen group A streptococcus (GAS) can take up heme from host heme-containing proteins as a source of iron. Little is known about the heme acquisition mechanism in GAS. We recently identified a streptococcal cell surface protein (designated Shp) and the lipoprotein component (designated HtsA) of an ATP-binding cassette (ABC) transporter made by GAS as heme-binding proteins. In an effort to delineate the molecular mechanism involved in heme acquisition by GAS, heme-free Shp (apo-Shp) a...
Efficient and stable reconstitution of the ABC transporter BmrA for solid-state NMR studies
Kunert, Britta; Gardiennet, Carole; Lacabanne, Denis; Calles-Garcia, Daniel; Falson, Pierre; Jault, Jean-Michel; Meier, Beat H; Penin, François; Böckmann, Anja
We present solid-state NMR sample preparation and first 2D spectra of the Bacillus subtilis ATP-binding cassette (ABC) transporter BmrA, a membrane protein involved in multidrug resistance. The homodimeric 130-kDa protein is a challenge for structural characterization due to its membrane-bound nature, size, inherent flexibility and insolubility. We show that reconstitution of this protein in lipids from Bacillus subtilis at a lipid-protein ratio of 0.5 w/w allows for optimal protein insertion...
The Caulobacter crescentus Paracrystalline S-Layer Protein Is Secreted by an ABC Transporter (Type I) Secretion Apparatus
Awram, Peter; Smit, John
Caulobacter crescentus is a gram-negative bacterium that produces a two-dimensional crystalline array on its surface composed of a single 98-kDa protein, RsaA. Secretion of RsaA to the cell surface relies on an uncleaved C-terminal secretion signal. In this report, we identify two genes encoding components of the RsaA secretion apparatus. These components are part of a type I secretion system involving an ABC transporter protein. These genes, lying immediately 3′ of rsaA, were found by screen...
In vitro functional characterization of BtuCD-F, the Escherichia coli ABC transporter for vitamin B-12 uptake
Borths, EL; Poolman, B; Hvorup, RN; Locher, KP; Rees, DC; Hvorup, Rikki N.; Locher, Kaspar P.; Rees, Douglas C.
BtuCD is an ATP binding cassette (ABC) transporter that facilitates uptake of vitamin B-12 into the cytoplasm of Escherichia coli. The crystal structures of BtuCD and its cognate periplasmic binding protein BtuF have been recently determined. We have now explored BtuCD-F function in vitro, both in proteoliposomes and in various detergents. BtuCD reconstituted into proteoliposomes has a significant basal ATP hydrolysis rate that is stimulated by addition of BtuF and inhibited by sodium ortho-v...
The abcEDCBA-Encoded ABC Transporter and the virB Operon-Encoded Type IV Secretion System of Brucella ovis Are Critical for Intracellular Trafficking and Survival in Ovine Monocyte-Derived Macrophages.
Auricelio A Macedo
Full Text Available Brucella ovis infection is associated with epididymitis, orchitis and infertility in rams. Most of the information available on B. ovis and host cell interaction has been generated using murine macrophages or epithelial cell lines, but the interaction between B. ovis and primary ovine macrophages has not been studied. The aim of this study was to evaluate the role of the B. ovis abcEDCBA-encoded ABC transporter and the virB operon-encoded Type IV Secretion System (T4SS during intracellular survival of B. ovis in ovine peripheral blood monocyte-derived macrophages. ΔabcBA and ΔvirB2 mutant strains were unable to survive in the intracellular environment when compared to the WT B. ovis at 48 hours post infection (hpi. In addition, these mutant strains cannot exclude the lysosomal marker LAMP1 from its vacuolar membrane, and their vacuoles do not acquire the endoplasmic reticulum marker calreticulin, which takes place in the WT B. ovis containing vacuole. Higher levels of nitric oxide production were observed in macrophages infected with WT B. ovis at 48 hpi when compared to macrophages infected with the ΔabcBA or ΔvirB2 mutant strains. Conversely, higher levels of reactive oxygen species were detected in macrophages infected with the ΔabcBA or ΔvirB2 mutant strains at 48 hpi when compared to macrophages infected with the WT strain. Our results demonstrate that B. ovis is able to persist and multiply in ovine macrophages, while ΔabcBA and ΔvirB2 mutations prevent intracellular multiplication, favor phagolysosome fusion, and impair maturation of the B. ovis vacuole towards an endoplasmic reticulum-derived compartment.
Quantitative Analysis of the Relative Transcript Levels of ABC Transporter Atr Genes in Aspergillus nidulans by Real-Time Reverse Transcription-PCR Assay
Pizeta Semighini, Camile; Marins, Mozart; Goldman, Maria Helena S.; Goldman, Gustavo Henrique
The development of assays for quantitative analysis of the relative transcript levels of ABC transporter genes by real-time reverse transcription-PCR (RT-PCR) might provide important information about multidrug resistance in filamentous fungi. Here, we evaluate the potential of real-time RT-PCR to quantify the relative transcript levels of ABC transporter Atr genes from Aspergillus nidulans. The AtrA to AtrD genes showed different and higher levels in the presence of structurally unrelated dr...
Human ABC transporter ABCG2/BCRP expression in chemoresistance: basic and clinical perspectives for molecular cancer therapeutics
Noguchi K
Full Text Available Kohji Noguchi, Kazuhiro Katayama, Yoshikazu Sugimoto Division of Chemotherapy, Faculty of Pharmacy, Keio University, Tokyo, Japan Abstract: Adenine triphosphate (ATP-binding cassette (ABC transporter proteins, such as ABCB1/P-glycoprotein (P-gp and ABCG2/breast cancer resistance protein (BCRP, transport various structurally unrelated compounds out of cells. ABCG2/BCRP is referred to as a "half-type" ABC transporter, functioning as a homodimer, and transports anticancer agents such as irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38, gefitinib, imatinib, methotrexate, and mitoxantrone from cells. The expression of ABCG2/BCRP can confer a multidrug-resistant phenotype on cancer cells and affect drug absorption, distribution, metabolism, and excretion in normal tissues, thus modulating the in vivo efficacy of chemotherapeutic agents. Clarification of the substrate preferences and structural relationships of ABCG2/BCRP is essential for our understanding of the molecular mechanisms underlying its effects in vivo during chemotherapy. Its single-nucleotide polymorphisms are also involved in determining the efficacy of chemotherapeutics, and those that reduce the functional activity of ABCG2/BCRP might be associated with unexpected adverse effects from normal doses of anticancer drugs that are ABCG2/BCRP substrates. Importantly, many recently developed molecular-targeted cancer drugs, such as the tyrosine kinase inhisbitors, imatinib mesylate, gefitinib, and others, can also interact with ABCG2/BCRP. Both functional single-nucleotide polymorphisms and inhibitory agents of ABCG2/BCRP modulate the in vivo pharmacokinetics and pharmacodynamics of these molecular cancer treatments, so the pharmacogenetics of ABCG2/BCRP is an important consideration in the application of molecular-targeted chemotherapies. Keywords: kinase inhibitor, SNP, single-nucleotide polymorphisms, molecular target
Environmental Conditions Influence Induction of Key ABC-Transporter Genes Affecting Glyphosate Resistance Mechanism in Conyza canadensis
Tani, Eleni; Chachalis, Demosthenis; Travlos, Ilias S.; Bilalis, Dimitrios
Conyza canadensis has been reported to be the most frequent weed species that evolved resistance to glyphosate in various parts of the world. The objective of the present study was to investigate the effect of environmental conditions (temperature and light) on the expression levels of the EPSPS gene and two major ABC-transporter genes (M10 and M11) on glyphosate susceptible (GS) and glyphosate resistant (GR) horseweed populations, collected from several regions across Greece. Real-time PCR was conducted to determine the expression level of the aforementioned genes when glyphosate was applied at normal (1×; 533 g·a.e.·ha−1) and high rates (4×, 8×), measured at an early one day after treatment (DAT) and a later stage (four DAT) of expression. Plants were exposed to light or dark conditions, at three temperature regimes (8, 25, 35 °C). GR plants were made sensitive when exposed to 8 °C with light; those sensitized plants behaved biochemically (shikimate accumulation) and molecularly (expression of EPSPS and ABC-genes) like the GS plants. Results from the current study show the direct link between the environmental conditions and the induction level of the above key genes that likely affect the efficiency of the proposed mechanism of glyphosate resistance. PMID:27104532
Environmental Conditions Influence Induction of Key ABC-Transporter Genes Affecting Glyphosate Resistance Mechanism in Conyza canadensis.
Tani, Eleni; Chachalis, Demosthenis; Travlos, Ilias S; Bilalis, Dimitrios
Conyza canadensis has been reported to be the most frequent weed species that evolved resistance to glyphosate in various parts of the world. The objective of the present study was to investigate the effect of environmental conditions (temperature and light) on the expression levels of the EPSPS gene and two major ABC-transporter genes (M10 and M11) on glyphosate susceptible (GS) and glyphosate resistant (GR) horseweed populations, collected from several regions across Greece. Real-time PCR was conducted to determine the expression level of the aforementioned genes when glyphosate was applied at normal (1×; 533 g·a.e.·ha(-1)) and high rates (4×, 8×), measured at an early one day after treatment (DAT) and a later stage (four DAT) of expression. Plants were exposed to light or dark conditions, at three temperature regimes (8, 25, 35 °C). GR plants were made sensitive when exposed to 8 °C with light; those sensitized plants behaved biochemically (shikimate accumulation) and molecularly (expression of EPSPS and ABC-genes) like the GS plants. Results from the current study show the direct link between the environmental conditions and the induction level of the above key genes that likely affect the efficiency of the proposed mechanism of glyphosate resistance. PMID:27104532
Structural basis for the hydrolysis of ATP by a nucleotide binding subunit of an amino acid ABC transporter from Thermus thermophilus.
Devi, Seenivasan Karthiga; Chichili, Vishnu Priyanka Reddy; Jeyakanthan, J; Velmurugan, D; Sivaraman, J
ATP-binding cassette (ABC) transporters are a major family of small molecule transporter proteins, and their deregulation is associated with several diseases, including cancer. Here, we report the crystal structure of the nucleotide binding domain (NBD) of an amino acid ABC transporter from Thermus thermophilus (TTHA1159) in its apo form and as a complex with ADP along with functional studies. TTHA1159 is a putative arginine ABC transporter. The apo-TTHA1159 was crystallized in dimeric form, a hitherto unreported form of an apo NBD. Structural comparison of the apo and ADP-Mg(2+) complexes revealed that Phe14 of TTHA1159 undergoes a significant conformational change to accommodate ADP, and that the bound ADP interacts with the P-loop (Gly40-Thr45). Modeling of ATP-Mg(2+):TTHA1159 complex revealed that Gln86 and Glu164 are involved in water-mediated hydrogen bonding contacts and Asp163 in Mg(2+) ion-mediated hydrogen bonding contacts with the γ-phosphate of ATP, consistent with the findings of other ABC transporters. Mutational studies confirmed the necessity of each of these residues, and a comparison of the apo/ADP Mg(2+):TTHA1159 with its ATP-complex model suggests the likelihood of a key conformational change to the Gln86 side chain for ATP hydrolysis. PMID:25916755
Secondary metabolites inhibiting ABC transporters and reversing resistance of cancer cells and fungi to cytotoxic and antimicrobial agents
Michael eWink
Full Text Available Fungal, bacterial and cancer cells can develop resistance against antifungal, antibacterial or anticancer agents. Mechanisms of resistance are complex and often multifactorial. Mechanisms include: 1. Activation of ABC transporters, such as P-gp, which pump out lipophilic compounds that have entered a cell, 2. Activation of cytochrome p450 oxidases which can oxidise lipophilic agents to make them more hydrophilic and accessible for conjugation reaction with glucuronic acid, sulphate or amino acids, and 3. Activation of glutathione transferase, which can conjugate xenobiotics. This review summarises the evidence that secondary metabolites of plants, such as alkaloids, phenolics and terpenoids can interfere with ABC transporters in cancer cells, parasites, bacteria and fungi. Among the active natural products several lipophilic terpenoids ( monoterpenes, diterpenes, triterpenes (including saponins, steroids (including cardiac glycosides and tetraterpenes but also some alkaloids (isoquinoline, protoberberine, quinoline, indole, monoterpene indole, and steroidal alkaloids function probably as competitive inhibitors of P-gp, MRP1 and BCRP in cancer cells, or efflux pumps in bacteria (NorA and fungi. More polar phenolics (phenolic acids, flavonoids, catechins, chalcones, xanthones, stilbenes, anthocyanins, tannins, anthraquinones, and naphthoquinones directly inhibit proteins forming several hydrogen and ionic bonds and thus disturbing the 3D structure of the transporters. The natural products may be interesting in medicine or agriculture as they can enhance the activity of active chemotherapeutics or pesticides or even reverse MDR, at least partially, of adapted and resistant cells. If these secondary metabolites are applied in combination with a cytotoxic or antimicrobial agent, they may reverse resistance in a synergistic fashion.
Reversing multidrug resistance in breast cancer cells by silencing ABC transporter genes with nanoparticle-facilitated delivery of target siRNAs
Li YT
Full Text Available Yong Tsuey Li,1 Ming Jang Chua,1 Anil Philip Kunnath,1 Ezharul Hoque Chowdhury,1,21Faculty of Medicine and Health Science, International Medical University (IMU, No 126, Jalan 19/155B, Bukit Jalil, 57000 Kuala Lumpur, Malaysia; 2Jeffrey Cheah School of Medicine and Health Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University Kuala Lumpur, MalaysiaBackground: Multidrug resistance, a major impediment to successful cancer chemotherapy, is the result of overexpression of ATP-binding cassette (ABC transporters extruding internalized drugs. Silencing of ABC transporter gene expression with small interfering RNA (siRNA could be an attractive approach to overcome multidrug resistance of cancer, although delivery of siRNA remains a major hurdle to fully exploit the potential of siRNA-based therapeutics. Recently, we have developed pH-sensitive carbonate apatite nanoparticles to efficiently carry and transport siRNA across the cell membrane, enabling knockdown of the cyclin B1 gene and consequential induction of apoptosis in synergy with anti-cancer drugs.Methods and results: We report that carbonate apatite-mediated delivery of the siRNAs targeting ABCG2 and ABCB1 gene transcripts in human breast cancer cells which constitutively express both of the transporter genes dose-dependently enhanced chemosensitivity to doxorubicin, paclitaxel and cisplatin, the traditionally used chemotherapeutic agents. Moreover, codelivery of two specific siRNAs targeting ABCB1 and ABCG2 transcripts resulted in a more robust increase of chemosensitivity in the cancer cells, indicating the reversal of ABC transporter-mediated multidrug resistance.Conclusion: The delivery concept of multiple siRNAs against ABC transporter genes is highly promising for preclinical and clinical investigation in reversing the multidrug resistance phenotype of breast cancer.Keywords: carbonate apatite, siRNA, gene expression, transfection, breast cancer, ABC transporter
Alleviation of temperature-sensitive secretion defect of Pseudomonas fluorescens ATP-binding cassette (ABC) transporter, TliDEF, by a change of single amino acid in the ABC protein, TliD.
Eom, Gyeong Tae; Oh, Joon Young; Park, Ji Hyun; Lim, Hye Jin; Lee, So Jeong; Kim, Eun Young; Choi, Ji-Eun; Jegal, Jonggeon; Song, Bong Keun; Yu, Ju-Hyun; Song, Jae Kwang
An ABC transporter, TliDEF, from Pseudomonas fluorescens SIK W1, mediates the secretion of its cognate lipase, TliA, in a temperature-dependent secretion manner; the TliDEF-mediated secretion of TliA was impossible at the temperatures over 33°C. To isolate a mutant TliDEF capable of secreting TliA at 35°C, the mutagenesis of ABC protein (TliD) was performed. The mutated tliD library where a random point mutation was introduced by error-prone PCR was coexpressed with the wild-type tliE, tliF and tliA in Escherichia coli. Among approximately 10,000 colonies of the tliD library, we selected one colony that formed transparent halo on LB-tributyrin plates at 35°C. At the growth temperature of 35°C, the selected mutant TliD showed 1.75 U/ml of the extracellular lipase activity, while the wild-type TliDEF did not show any detectable lipase activity in the culture supernatant of E. coli. Moreover, the mutant TliD also showed higher level of TliA secretion than the wild-type TliDEF at other culture temperatures, 20°C, 25°C and 30°C. The mutant TliD had a single amino acid change (Ser287Pro) in the predicted transmembrane region in the membrane domain of TliD, implying that the corresponding region of TliD was important for causing the temperature-dependent secretion of TliDEF. These results suggested that the property of ABC transporter could be changed by the change of amino acid in the ABC protein. PMID:27033673
Cell differentiation and infectivity of Leishmania mexicana are inhibited in a strain resistant to an ABC-transporter blocker.
Silva, N; Camacho, N; Figarella, K; Ponte-Sucre, A
We analysed whether markers of cell differentiation and infectivity differed when compared to the parental sensitive strain [NR(Gs)] in an in vitro selected Leishmania strain [NR(Gr)] resistant to Glibenclamide, an ATP-binding-cassette (ABC)-transporter blocker. The data show that the cell body area was larger in NR(Gr) compared to NR(Gs) and that functional characters associated with an infective metacyclic phenotype, such as resistance to the lytic effect of the alternative complement pathway and expression of the Meta-1 protein, were reduced. The infectivity of NR(Gr) to J774.1 macrophages was also significantly reduced. These results suggest that resistance in Leishmania against Glibenclamide, a general blocker of P-glycoproteins, could produce functional modifications that may be relevant for Leishmania differentiation, infectivity and survival. PMID:15206465
Salinomycin overcomes ABC transporter-mediated multidrug and apoptosis resistance in human leukemia stem cell-like KG-1a cells
Fuchs, Dominik [Research Group Molecular Neuro-Oncology, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg (Germany); Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Daniel, Volker; Sadeghi, Mahmoud; Opelz, Gerhard [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany); Naujokat, Cord, E-mail: firstname.lastname@example.com [Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg (Germany)
Leukemia stem cells are known to exhibit multidrug resistance by expression of ATP-binding cassette (ABC) transporters which constitute transmembrane proteins capable of exporting a wide variety of chemotherapeutic drugs from the cytosol. We show here that human promyeloblastic leukemia KG-1a cells exposed to the histone deacetylase inhibitor phenylbutyrate resemble many characteristics of leukemia stem cells, including expression of functional ABC transporters such as P-glycoprotein, BCRP and MRP8. Consequently, KG-1a cells display resistance to the induction of apoptosis by various chemotherapeutic drugs. Resistance to apoptosis induction by chemotherapeutic drugs can be reversed by cyclosporine A, which effectively inhibits the activity of P-glycoprotein and BCRP, thus demonstrating ABC transporter-mediated drug resistance in KG-1a cells. However, KG-1a are highly sensitive to apoptosis induction by salinomycin, a polyether ionophore antibiotic that has recently been shown to kill human breast cancer stem cell-like cells and to induce apoptosis in human cancer cells displaying multiple mechanisms of drug and apoptosis resistance. Whereas KG-1a cells can be adapted to proliferate in the presence of apoptosis-inducing concentrations of bortezomib and doxorubicin, salinomycin does not permit long-term adaptation of the cells to apoptosis-inducing concentrations. Thus, salinomycin should be regarded as a novel and effective agent for the elimination of leukemia stem cells and other tumor cells exhibiting ABC transporter-mediated multidrug resistance.
Salinomycin overcomes ABC transporter-mediated multidrug and apoptosis resistance in human leukemia stem cell-like KG-1a cells
Leukemia stem cells are known to exhibit multidrug resistance by expression of ATP-binding cassette (ABC) transporters which constitute transmembrane proteins capable of exporting a wide variety of chemotherapeutic drugs from the cytosol. We show here that human promyeloblastic leukemia KG-1a cells exposed to the histone deacetylase inhibitor phenylbutyrate resemble many characteristics of leukemia stem cells, including expression of functional ABC transporters such as P-glycoprotein, BCRP and MRP8. Consequently, KG-1a cells display resistance to the induction of apoptosis by various chemotherapeutic drugs. Resistance to apoptosis induction by chemotherapeutic drugs can be reversed by cyclosporine A, which effectively inhibits the activity of P-glycoprotein and BCRP, thus demonstrating ABC transporter-mediated drug resistance in KG-1a cells. However, KG-1a are highly sensitive to apoptosis induction by salinomycin, a polyether ionophore antibiotic that has recently been shown to kill human breast cancer stem cell-like cells and to induce apoptosis in human cancer cells displaying multiple mechanisms of drug and apoptosis resistance. Whereas KG-1a cells can be adapted to proliferate in the presence of apoptosis-inducing concentrations of bortezomib and doxorubicin, salinomycin does not permit long-term adaptation of the cells to apoptosis-inducing concentrations. Thus, salinomycin should be regarded as a novel and effective agent for the elimination of leukemia stem cells and other tumor cells exhibiting ABC transporter-mediated multidrug resistance.
Function of the ABC transporters, P-glycoprotein, multidrug resistance protein and breast cancer resistance protein, in minimal residual disease in acute myeloid leukemia.
Pol, van der M.A.; Broxterman, H.J.; Pater, JM; Feller, N.; Maas, M.; Weijers, GW; Scheffer, G.L.; Allen, JD; Scheper, R.J.; Loevezijn, van A; Ossenkoppele, G.J.; Schuurhuis, G.J.
BACKGROUND AND OBJECTIVES: Relapse is common in acute myeloid leukemia (AML) because of persistence of minimal residual disease (MRD). ABC-transporters P-glycoprotein (Pgp) and multidrug resistance protein (MRP), are thought to contribute to treatment failure, while it is unknown whether breast canc
Polarized location of SLC and ABC drug transporters in monolayer-cultured human hepatocytes.
Le Vee, Marc; Jouan, Elodie; Noel, Gregory; Stieger, Bruno; Fardel, Olivier
Human hepatocytes cultured in a monolayer configuration represent a well-established in vitro model in liver toxicology, notably used in drug transporter studies. Polarized status of drug transporters, i.e., their coordinated location at sinusoidal or canalicular membranes, remains however incompletely documented in these cultured hepatocytes. The present study was therefore designed to analyze transporter expression and location in such cells. Most of drug transporters were first shown to be present at notable mRNA levels in monolayer-cultured human hepatocytes. Cultured human hepatocytes, which morphologically exhibited bile canaliculi-like structures, were next demonstrated, through immunofluorescence staining, to express the influx transporters organic anion transporting polypeptide (OATP) 1B1, OATP2B1 and organic cation transporter (OCT) 1 and the efflux transporter multidrug resistance-associated protein (MRP) 3 at their sinusoidal pole. In addition, the efflux transporters P-glycoprotein and MRP2 were detected at the canalicular pole of monolayer-cultured human hepatocytes. Moreover, canalicular secretion of reference substrates for the efflux transporters bile salt export pump, MRP2 and P-glycoprotein as well as sinusoidal drug transporter activities were observed. This polarized and functional expression of drug transporters in monolayer-cultured human hepatocytes highlights the interest of using this human in vitro cell model in xenobiotic transport studies. PMID:25862123
Novel understanding of ABC transporters ABCB1/MDR/P-glycoprotein, ABCC2/MRP2, and ABCG2/BCRP in colorectal pathophysiology
Andersen, Vibeke; Svenningsen, Katrine; Knudsen, Lina Almind;
transporter proteins, inflammatory bowel disease, ulcerative, colitis, Crohns disease, colorectal cancer, colitis, intestinal inflammation, intestinal carcinogenesis, ABCB1/P-glycoprotein (P-gp/CD243/MDR1), ABCC2/multidrug resistance protein 2 (MRP2) and ABCG2/breast cancer resistance protein (BCRP), Abcb1....../Mdr1a, abcc2/Mrp2, abcg2/Bcrp, knock-out mice, tight junction, membrane lipid function. RESULTS: Recently, human studies reported that changes in the levels of ABC transporters were early events in the adenoma-carcinoma sequence leading to CRC. A link between ABCB1, high fat diet and gut microbes in...... which may additionally affect ABC transporter function through nuclear receptors and transcriptional regulation. Another critical role of ABCB1 was suggested by the finding that ABCB1 expression identifies a subpopulation of pro-inflammatory Th17 cells which were resistant to treatment with...
The Klebsiella pneumoniae O12 ATP-binding Cassette (ABC) Transporter Recognizes the Terminal Residue of Its O-antigen Polysaccharide Substrate.
Mann, Evan; Mallette, Evan; Clarke, Bradley R; Kimber, Matthew S; Whitfield, Chris
Export of the Escherichia coli serotype O9a O-antigenic polysaccharides (O-PS) involves an ATP-binding cassette (ABC) transporter. The process requires a non-reducing terminal residue, which is recognized by a carbohydrate-binding module (CBM) appended to the C terminus of the nucleotide-binding domain of the transporter. Here, we investigate the process in Klebsiella pneumoniae serotype O12 (and Raoultella terrigena ATCC 33257). The O12 polysaccharide is terminated at the non-reducing end by a β-linked 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) residue. The O12 ABC transporter also binds its cognate O-PS via a CBM, and export is dependent on the presence of the terminal β-Kdo residue. The overall structural architecture of the O12 CBM resembles the O9a prototype, but they share only weak sequence similarity, and the putative binding pocket for the O12 glycan is different. Removal of the CBM abrogated O-PS transport, but export was restored when the CBM was expressed in trans with the mutant CBM-deficient ABC transporter. These results demonstrate that the CBM-mediated substrate-recognition mechanism is evolutionarily conserved and can operate with glycans of widely differing structures. PMID:26934919
Purification, crystallization and preliminary X-ray diffraction analysis of the putative ABC transporter ATP-binding protein from Thermotoga maritima
The putative ABC transporter ATP-binding protein TM0222 from T. maritima was cloned, overproduced, purified and crystallized. A complete MAD diffraction data set has been collected to 2.3 Å resolution. Adenosine triphosphate (ATP) binding cassette transporters (ABC transporters) are ATP hydrolysis-dependent transmembrane transporters. Here, the overproduction, purification and crystallization of the putative ABC transporter ATP-binding protein TM0222 from Thermotoga maritima are reported. The protein was crystallized in the hexagonal space group P6422, with unit-cell parameters a = b = 148.49, c = 106.96 Å, γ = 120.0°. Assuming the presence of two molecules in the asymmetric unit, the calculated VM is 2.84 Å3 Da−1, which corresponds to a solvent content of 56.6%. A three-wavelength MAD data set was collected to 2.3 Å resolution from SeMet-substituted TM0222 crystals. Data sets were collected on the BL38B1 beamline at SPring-8, Japan
Efficient and stable reconstitution of the ABC transporter BmrA for solid-state NMR studies.
Kunert, Britta; Gardiennet, Carole; Lacabanne, Denis; Calles-Garcia, Daniel; Falson, Pierre; Jault, Jean-Michel; Meier, Beat H; Penin, François; Böckmann, Anja
We present solid-state NMR sample preparation and first 2D spectra of the Bacillus subtilis ATP-binding cassette (ABC) transporter BmrA, a membrane protein involved in multidrug resistance. The homodimeric 130-kDa protein is a challenge for structural characterization due to its membrane-bound nature, size, inherent flexibility and insolubility. We show that reconstitution of this protein in lipids from Bacillus subtilis at a lipid-protein ratio of 0.5 w/w allows for optimal protein insertion in lipid membranes with respect to two central NMR requirements, high signal-to-noise in the spectra and sample stability over a time period of months. The obtained spectra point to a well-folded protein and a highly homogenous preparation, as witnessed by the narrow resonance lines and the signal dispersion typical for the expected secondary structure distribution of BmrA. This opens the way for studies of the different conformational states of the transporter in the export cycle, as well as on interactions with substrates, via chemical-shift fingerprints and sequential resonance assignments. PMID:25988146
ABC transporters P-gp and Bcrp do not limit the brain uptake of the novel antipsychotic and anticonvulsant drug cannabidiol in mice.
Brzozowska, Natalia; Li, Kong M; Wang, Xiao Suo; Booth, Jessica; Stuart, Jordyn; McGregor, Iain S; Arnold, Jonathon C
Cannabidiol (CBD) is currently being investigated as a novel therapeutic for the treatment of CNS disorders like schizophrenia and epilepsy. ABC transporters such as P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) mediate pharmacoresistance in these disorders. P-gp and Bcrp are expressed at the blood brain barrier (BBB) and reduce the brain uptake of substrate drugs including various antipsychotics and anticonvulsants. It is therefore important to assess whether CBD is prone to treatment resistance mediated by P-gp and Bcrp. Moreover, it has become common practice in the drug development of CNS agents to screen against ABC transporters to help isolate lead compounds with optimal pharmacokinetic properties. The current study aimed to assess whether P-gp and Bcrp impacts the brain transport of CBD by comparing CBD tissue concentrations in wild-type (WT) mice versus mice devoid of ABC transporter genes. P-gp knockout (Abcb1a/b (-∕-)), Bcrp knockout (Abcg2 (-∕-)), combined P-gp/Bcrp knockout (Abcb1a/b (-∕-) Abcg2 (-∕-)) and WT mice were injected with CBD, before brain and plasma samples were collected at various time-points. CBD results were compared with the positive control risperidone and 9-hydroxy risperidone, antipsychotic drugs that are established ABC transporter substrates. Brain and plasma concentrations of CBD were not greater in P-gp, Bcrp or P-gp/Bcrp knockout mice than WT mice. In comparison, the brain/plasma concentration ratios of risperidone and 9-hydroxy risperidone were profoundly higher in P-gp knockout mice than WT mice. These results suggest that CBD is not a substrate of P-gp or Bcrp and may be free from the complication of reduced brain uptake by these transporters. Such findings provide favorable evidence for the therapeutic development of CBD in the treatment of various CNS disorders. PMID:27257556
The N-terminal extension domain of the C. elegans half-molecule ABC transporter, HMT-1, is required for protein-protein interactions and function.
Sungjin Kim
Full Text Available BACKGROUND: Members of the HMT-1 (heavy metal tolerance factor 1 subfamily of the ATP-binding cassette (ABC transporter superfamily detoxify heavy metals and have unique topology: they are half-molecule ABC transporters that, in addition to a single transmembrane domain (TMD1 and a single nucleotide-binding domain (NBD1, possess a hydrophobic NH2-terminal extension (NTE. These structural features distinguish HMTs from other ABC transporters in different species including Drosophila and humans. Functional ABC transporters, however, are comprised of at least four-domains (two TMDs and two NDBs formed from either a single polypeptide or by the association of two or four separate subunits. Whether HMTs act as oligomers and what role the NTE domain plays in their function have not been determined. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we examined the oligomeric status of Caenorhabditis elegans HMT-1 and the functional significance of its NTE using gel-filtration chromatography in combination with the mating-based split-ubiquitin yeast two-hybrid system (mbSUS and functional in vivo assays. We found that HMT-1 exists in a protein complex in C. elegans. Studies in S. cerevisiae showed that HMT-1 at a minimum homodimerizes and that oligomerization is essential for HMT-1 to confer cadmium tolerance. We also established that the NTE domain plays an important structural and functional role: it is essential for HMT-1 oligomerization and Cd-detoxification function. However, the NTE itself was not sufficient for oligomerization suggesting that multiple structural features of HMT-1 must associate to form a functional transporter. CONCLUSIONS: The prominence of heavy metals as environmental toxins and the remarkable conservation of HMT-1 structural architecture and function in different species reinforce the value of continued studies of HMT-1 in model systems for identifying functional domains in HMT1 of humans.
ABC-type transporters and cuticle assembly: Linking function to polarity in epidermis cells
Panikashvili, David; Aharoni, Asaph
The aerial organs of plants are covered with a cuticle, a continuous layer overlaying the outermost cell walls of the epidermis. The cuticle is composed of two major classes of the lipid biopolymers: cutin and waxes, collectively termed cuticular lipids. Biosynthesis and transport of cuticular lipids occur predominantly in the epidermis cells. In the transport pathway, cuticular lipids are exported from their site of biosynthesis in the ER/plastid to the extracellular space through the plasma...
Classification of a Haemophilus influenzae ABC Transporter HI1470/71 through Its Cognate Molybdate Periplasmic Binding Protein, MolA
Tirado-Lee, Leidamarie; Lee, Allen; Rees, Douglas C.; Pinkett, Heather W. (CIT); (NWU)
molA (HI1472) from H. influenzae encodes a periplasmic binding protein (PBP) that delivers substrate to the ABC transporter MolB{sub 2}C{sub 2} (formerly HI1470/71). The structures of MolA with molybdate and tungstate in the binding pocket were solved to 1.6 and 1.7 {angstrom} resolution, respectively. The MolA-binding protein binds molybdate and tungstate, but not other oxyanions such as sulfate and phosphate, making it the first class III molybdate-binding protein structurally solved. The {approx}100 {mu}M binding affinity for tungstate and molybdate is significantly lower than observed for the class II ModA molybdate-binding proteins that have nanomolar to low micromolar affinity for molybdate. The presence of two molybdate loci in H. influenzae suggests multiple transport systems for one substrate, with molABC constituting a low-affinity molybdate locus.
Classification of a Haemophilus influenzae ABC transporter HI1470/71 through its cognate molybdate periplasmic binding protein, MolA.
Tirado-Lee, Leidamarie; Lee, Allen; Rees, Douglas C; Pinkett, Heather W
molA (HI1472) from H. influenzae encodes a periplasmic binding protein (PBP) that delivers substrate to the ABC transporter MolB(2)C(2) (formerly HI1470/71). The structures of MolA with molybdate and tungstate in the binding pocket were solved to 1.6 and 1.7 Å resolution, respectively. The MolA-binding protein binds molybdate and tungstate, but not other oxyanions such as sulfate and phosphate, making it the first class III molybdate-binding protein structurally solved. The ∼100 μM binding affinity for tungstate and molybdate is significantly lower than observed for the class II ModA molybdate-binding proteins that have nanomolar to low micromolar affinity for molybdate. The presence of two molybdate loci in H. influenzae suggests multiple transport systems for one substrate, with molABC constituting a low-affinity molybdate locus. PMID:22078568
The novel ABC transporter ABCH1 is a potential target for RNAi-based insect pest control and resistance management.
Guo, Zhaojiang; Kang, Shi; Zhu, Xun; Xia, Jixing; Wu, Qingjun; Wang, Shaoli; Xie, Wen; Zhang, Youjun
Insect pests cause serious crop damage and develop high-level resistance to chemical insecticides and Bacillus thuringiensis (Bt) insecticidal Cry toxins. A new promising approach for controlling them and overcoming this resistance is RNA interference (RNAi). The RNAi-based insect control strategy depends on the selection of suitable target genes. In this study, we cloned and characterized a novel ABC transporter gene PxABCH1 in diamondback moth, Plutella xylostella (L.). Phylogenetic analysis showed that PxABCH1 is closely related to ABCA and ABCG subfamily members. Spatial-temporal expression detection revealed that PxABCH1 was expressed in all tissues and developmental stages, and highest expressed in head and male adult. Midgut sequence variation and expression analyses of PxABCH1 in all the susceptible and Bt-resistant P. xylostella strains and the functional analysis by sublethal RNAi demonstrated that Cry1Ac resistance was independent of this gene. Silencing of PxABCH1 by a relatively high dose of dsRNA dramatically reduced its expression and resulted in larval and pupal lethal phenotypes in both susceptible and Cry1Ac-resistant P. xylostella strains. To our knowledge, this study provides the first insight into ABCH1 in lepidopterans and reveals it as an excellent target for RNAi-based insect pest control and resistance management. PMID:26333918
The naphthoquinones, vitamin K3 and its structural analog plumbagin, are substrates of the multidrug resistance-linked ABC drug transporter ABCG2
Shukla, Suneet; Wu, Chung-Pu; Nandigama, Krishnamachary; Ambudkar, Suresh V.
Vitamin K3 (Menadione; 2-methyl-1,4-naphthoquinone) is a structural precursor of vitamins K1 and K2 which are essential for blood clotting. The naturally occurring structural analog of this vitamin, plumbagin (5-hydroxy-menadione), is known to modulate cellular proliferation, apoptosis, carcinogenesis, and radioresistance. We, here, report that both vitamin K3 and plumbagin are substrates of the multidrug resistance-linked ATP binding cassette (ABC) drug transporter, ABCG2. Vitamin K3 and plu...
The ABC transporter MgAtr4 is a virulence factor of Mycosphaerella graminicola that affects colonization of substomatal cavities in wheat leaves
Stergiopoulos, I.; Zwiers, L.H.; Waard, de M.A.
The role in virulence of the ATP-binding cassette (ABC) transporters MgAtr1, MgAtr2, MgAtr3, MgAtr4, and MgAtr5 from Mycosphaerella graminicola was analyzed by gene disruption or replacement on seedlings of the susceptible wheat cultivar Obelisk. Disruption strains of MgAtr1 and MgAtr2 and replaceme
Distribution and Genetic Diversity of the ABC Transporter Lipoproteins PiuA and PiaA within Streptococcus pneumoniae and Related Streptococci
Whalan, Rachael H.; Funnell, Simon G.P.; Bowler, Lucas D.; Hudson, Michael J.; Robinson, Andrew; Dowson, Christopher G.
Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. The existence of approximately 90 antigenically distinct capsular serotypes has greatly complicated the development of an effective pneumococcal vaccine. Virulence-associated proteins common and conserved among all capsular types now represent the best strategy to combat pneumococcal infections. PiuA and PiaA are the lipoprotein components of two pneumococcal iron ABC transporters and are required for full virulen...
Overexpression of patA and patB, Which Encode ABC Transporters, Is Associated with Fluoroquinolone Resistance in Clinical Isolates of Streptococcus pneumoniae▿
Garvey, Mark I.; Baylay, Alison J.; Wong, Ryan L.; Piddock, Laura J. V.
Fifty-seven clinical isolates of Streptococcus pneumoniae were divided into four groups based on their susceptibilities to the fluoroquinolones ciprofloxacin and norfloxacin and the dyes ethidium bromide and acriflavine. Comparative reverse transcription-PCR was used to determine the level of expression of the genes patA and patB, which encode putative ABC transporters. Overexpression was observed in 14 of the 15 isolates that were resistant to both fluoroquinolones and dyes and in only 3 of ...
The putative ABC transporter encoded by the orf19.4531 plays a role in the sensitivity of Candida albicans cells to azole antifungal drugs.
Jiang, Linghuo; Xu, Dayong; Chen, Zhen; Cao, Yongbing; Gao, Pinghui; Jiang, Yuanying
ATP-binding cassette (ABC) transporters constitute a large superfamily of integral membrane proteins in prokaryotic and eukaryotic cells. In the human fungal pathogenCandida albicans, there are 28 genes encoding ABC transporters and many of them have not been characterized so far. The orf19.4531 (also known as IPF7530) encodes a putative ABC transporter. In this study, we have demonstrated that disruption of orf19.4531 causesC. albicanscells to become tolerant to azoles, but not to polyene antifungals and terbinafine. Therefore, the protein encoded by orf19.4531 is involved in azole sensitivity and we name it asROA1, the regulator of azole sensitivity 1 gene. Consistently, we show that the expression ofROA1is responsive to treatment of either fluconazole or ketoconazole inC. albicans In addition, through a GFP tagging approach, Roa1 is localized in a small punctuate compartment adjacent to the vacuolar membrane. However,ROA1is not essential for thein vitrofilamentation ofC. albicanscells. PMID:26975389
Drosophila ABC Transporter DmHMT-1 Confers Tolerance to Cadmium.
Half molecule ATP-binding cassette transporters of the HMT1(heavy metal tolerance factor 1)subfamily are required for Cd2+ tolerance in Schizosaccharomyces pombe, Caenorhabditis elegans and Chlamydomonas reinhardtii, and have homologs in other species, including plants and humans. Based on studies i...
Reversal of resistance by GF120918 in cell lines expressing the ABC half-transporter, MXR
de Bruin, M; Miyake, K; Litman, Thomas;
in S1-B1-20 and S1-M1-80 cells when incubated in the presence of GF120918 than when incubated with mitoxantrone alone. Thus, GF120918 appears to fit the paradigm of a multispecific blocker and is able to block rhodamine and mitoxantrone efflux by the newly identified mitoxantrone transporter. Further...
Formation of a Chloride-conducting State in the Maltose ATP-binding Cassette (ABC) Transporter.
Carlson, Michael L; Bao, Huan; Duong, Franck
ATP-binding cassette transporters use an alternating access mechanism to move substrates across cellular membranes. This mode of transport ensures the selective passage of molecules while preserving membrane impermeability. The crystal structures of MalFGK2, inward- and outward-facing, show that the transporter is sealed against ions and small molecules. It has yet to be determined whether membrane impermeability is maintained when MalFGK2 cycles between these two conformations. Through the use of a mutant that resides in intermediate conformations close to the transition state, we demonstrate that not only is chloride conductance occurring, but also to a degree large enough to compromise cell viability. Introduction of mutations in the periplasmic gate lead to the formation of a channel that is quasi-permanently open. MalFGK2 must therefore stay away from these ion-conducting conformations to preserve the membrane barrier; otherwise, a few mutations that increase access to the ion-conducting states are enough to convert an ATP-binding cassette transporter into a channel. PMID:27059961
The Riboswitch Regulates a Thiamine Pyrophosphate ABC Transporter of the Oral Spirochete Treponema denticola ▿ †
Bian, Jiang; Shen, Hongwu; Tu, Youbin; Yu, Aiming; Li, Chunhao
Thiamine pyrophosphate (TPP), a biologically active form of thiamine (vitamin B1), is an essential cofactor in all living systems. Microorganisms either synthesize TPP via de novo biosynthesis pathways or uptake exogenous thiamine from the environment via specific transporters. The oral spirochete Treponema denticola is an important pathogen that is associated with human periodontal diseases. It lacks a de novo TPP biosynthesis pathway and needs exogenous TPP for growth, suggesting that it ma...
ABC protein transport of MRI contrast agents in canalicular rat liver plasma vesicles and yeast vacuoles
The mechanism of excretion into bile of hepatospecific magnetic resonance imaging (MRI) contrast media employed labeled Gd-reagents EOB.DTPA, BOPTA, B 20790 (iopanoate-linked), and B 21690 (glycocholate-linked) for measurement in rat liver canalicular plasma membrane vesicles and yeast vacuoles. The presence of ATP gave threefold greater transport of B 20790 and B 21690 than of EOB.DTPA and BOPTA. In yeast vacuoles the ATP stimulatory effect was eightfold with B 20790 and fivefold greater for B 21690, whereas in YCF1- or YLLO115w-deleted yeast cells the transport was significantly reduced and absent from double mutants, YCF1 and YLLO15w. The transport was similar in wild-type and deletant cells for B 21690; taurocholate gave 85% inhibition. These data suggest that bilary secretion of structurally related MRI agents depend on molecular structure. The findings are suggestive as of possible value for clinical diagnosis of inherited hyperbilirubinemias and other liver disorders
Heteronuclear multidimensional NMR and homology modelling studies of the C-terminal nucleotide-binding domain of the human mitochondrial ABC transporter ABCB6
Human ATP-binding cassette, sub-family B, member 6 (ABCB6) is a mitochondrial ABC transporter, and presumably contributes to iron homeostasis. Aimed at understanding the structural basis for the conformational changes accompanying the substrate-transportation cycle, we have studied the C-terminal nucleotide-binding domain of ABCB6 (ABCB6-C) in both the nucleotide-free and ADP-bound states by heteronuclear multidimensional NMR and homology modelling. A non-linear sampling scheme was utilised for indirectly acquired 13C and 15N dimensions of all 3D triple-resonance NMR experiments, in order to overcome the instability and the low solubility of ABCB6-C. The backbone resonances for approximately 25% of non-proline residues, which are mostly distributed around the functionally important loops and in the Helical domain, were not observed for nucleotide-free form of ABCB6-C. From the pH, temperature and magnetic field strength dependencies of the resonance intensities, we concluded that this incompleteness in the assignments is mainly due to the exchange between multiple conformations at an intermediate rate on the NMR timescale. These localised conformational dynamics remained in ADP-bound ABCB6-C except for the loops responsible for adenine base and α/β-phosphate binding. These results revealed that the localised dynamic cooperativity, which was recently proposed for a prokaryotic ABC MJ1267, also exists in a higher eukaryotic ABC, and is presumably shared by all members of the ABC family. Since the Helical domain is the putative interface to the transmembrane domain, this cooperativity may explain the coupled functions between domains in the substrate-transportation cycle
Lateral gene transfer of an ABC transporter complex between major constituents of the human gut microbiome
Meehan Conor J
Full Text Available Abstract Background Several links have been established between the human gut microbiome and conditions such as obesity and inflammatory bowel syndrome. This highlights the importance of understanding what properties of the gut microbiome can affect the health of the human host. Studies have been undertaken to determine the species composition of this microbiome and infer functional profiles associated with such host properties. However, lateral gene transfer (LGT between community members may result in misleading taxonomic attributions for the recipient organisms, thus making species-function links difficult to establish. Results We identified a peptides/nickel transport complex whose components differed in abundance based upon levels of host obesity, and assigned the encoded proteins to members of the microbial community. Each protein was assigned to several distinct taxonomic groups, with moderate levels of agreement observed among different proteins in the complex. Phylogenetic trees of these proteins produced clusters that differed greatly from taxonomic attributions and indicated that habitat-directed LGT of this complex is likely to have occurred, though not always between the same partners. Conclusions These findings demonstrate that certain membrane transport systems may be an important factor within an obese-associated gut microbiome and that such complexes may be acquired several times by different strains of the same species. Additionally, an example of individual proteins from different organisms being transferred into one operon was observed, potentially demonstrating a functional complex despite the donors of the subunits being taxonomically disparate. Our results also highlight the potential impact of habitat-directed LGT on the resident microbiota.
Novel understanding of ABC transporters ABCB1/MDR/P-glycoprotein, ABCC2/MRP2, and ABCG2/BCRP in colorectal pathophysiology
Andersen, Vibeke; Svenningsen, Katrine; Almind Knudsen, Lina; Hansen, Axel Kornerup; Holmskov, Uffe; Stensballe, Allan; Vogel, Ulla
transporter proteins, inflammatory bowel disease, ulcerative, colitis, Crohns disease, colorectal cancer, colitis, intestinal inflammation, intestinal carcinogenesis, ABCB1/P-glycoprotein (P-gp/CD243/MDR1), ABCC2/multidrug resistance protein 2 (MRP2) and ABCG2/breast cancer resistance protein (BCRP), Abcb1....../Mdr1a, abcc2/Mrp2, abcg2/Bcrp, knock-out mice, tight junction, membrane lipid function. RESULTS: Recently, human studies reported that changes in the levels of ABC transporters were early events in the adenoma-carcinoma sequence leading to CRC. A link between ABCB1, high fat diet and gut microbes in...
Membrane topology and functional importance of the periplasmic region of ABC transporter LolCDE.
Yasuda, Masaki; Iguchi-Yokoyama, Asako; Matsuyama, Shin-ichi; Tokuda, Hajime; Narita, Shin-ichiro
The LolCDE complex is an ATP-binding cassette transporter that mediates the release of newly synthesized lipoproteins from the cytoplasmic membrane of gram-negative bacteria, which results in the initiation of outer-membrane sorting of lipoproteins through the Lol pathway. LolCDE is composed of one copy each of membrane subunits LolC and LolE, and two copies of nucleotide-binding subunit LolD. In this study, we examined the membrane topology of LolC and LolE by PhoA fusion analysis. Both LolC and LolE were found to have four transmembrane segments with a large periplasmic loop exposed to the periplasm. Despite similarities in sequence and topology, the accessibility of a sulfhydryl reagent to Cys introduced into the periplasmic loop suggested that the structure of the periplasmic region differs between LolC and LolE. Inhibition of the release of lipoproteins by the sulfhydryl reagent supported a previous proposal that LolC and LolE have distinct functions. PMID:19809197
Subtle Structural Differences Trigger Inhibitory Activity of Propafenone Analogues at the Two Polyspecific ABC Transporters: P-Glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP).
Schwarz, Theresa; Montanari, Floriane; Cseke, Anna; Wlcek, Katrin; Visvader, Lene; Palme, Sarah; Chiba, Peter; Kuchler, Karl; Urban, Ernst; Ecker, Gerhard F
The transmembrane ABC transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are widely recognized for their role in cancer multidrug resistance and absorption and distribution of compounds. Furthermore, they are linked to drug-drug interactions and toxicity. Nevertheless, due to their polyspecificity, a molecular understanding of the ligand-transporter interaction, which allows designing of both selective and dual inhibitors, is still in its infancy. This study comprises a combined approach of synthesis, in silico prediction, and in vitro testing to identify molecular features triggering transporter selectivity. Synthesis and testing of a series of 15 propafenone analogues with varied rigidity and basicity of substituents provide first trends for selective and dual inhibitors. Results indicate that both the flexibility of the substituent at the nitrogen atom, as well as the basicity of the nitrogen atom, trigger transporter selectivity. Furthermore, inhibitory activity of compounds at P-gp seems to be much more influenced by logP than those at BCRP. Exploiting these differences further should thus allow designing specific inhibitors for these two polyspecific ABC-transporters. PMID:26970257
Combined phylogeny and neighborhood analysis of the evolution of the ABC transporters conferring multiple drug resistance in hemiascomycete yeasts
Goffeau André
Full Text Available Abstract Background Pleiotropic Drug Resistant transporters (PDR are members of the ATP-Binding Cassette (ABC subfamily which export antifungals and other xenobiotics in fungi and plants. This subfamily of transmembrane transporters has nine known members in Saccharomyces cerevisiae. We have analyzed the complex evolution of the pleiotropic drug resistance proteins (Pdrp subfamily where gene duplications and deletions occur independently in individual genomes. This study was carried out on 62 Pdrp from nine hemiascomycetous species, seven of which span 6 of the 14 clades of the Saccharomyces complex while the two others species, Debaryomyces hansenii and Yarrowia lipolytica, are further apart from an evolutive point of view. Results Combined phylogenetic and neighborhood analyses enabled us to identify five Pdrp clusters in the Saccharomyces complex. Three of them comprise orthologs of the Pdrp sensu stricto, Pdr5p, Pdr10p, Pdr12p, Pdr15p, Snq2p and YNR070wp. The evolutive pathway of the orthologs of Snq2 and YNR070w is particularly complex due to a tandem gene array in Eremothecium gossypii, Kluyveromyces lactis and Saccharomyces (Lachancea kluyveri. This pathway and different cases of duplications and deletions were clarified by using a neighborhood analysis based on synteny. For the two distant species, Yarrowia lipolytica and Debaryomyces hansenii, no neighborhood evidence is available for these clusters and many homologs of Pdr5 and Pdr15 are phylogenetically assigned to species-based clusters. Two other clusters comprise the orthologs of the sensu lato Pdrp, Aus1p/Pdr11p and YOL075cp respectively. The evolutionary pathway of these clusters is simpler. Nevertheless, orthologs of these genes are missing in some species. Conclusion Numerous duplications were traced among the Hemiascomycetous Pdrp studied. The role of the Whole Genome Duplication (WGD is sorted out and our analyses confirm the common ancestrality of Pdr5p and Pdr15p. A tandem
Classification of a Haemophilus influenzae ABC transporter HI1470/71 through its cognate molybdate periplasmic binding protein, MolA
Tirado-Lee, Leidamarie; Lee, Allen; Rees, Douglas C.; Pinkett, Heather W.
molA(HI1472) from H. influenzae encodes a periplasmic binding protein (PBP) that delivers substrate to the ABC transporter MolB2C2 (formerly HI1470/71). The structures of MolA with molybdate and tungstate in the binding pocket were solved to 1.6 and 1.7-Å resolution, respectively. The MolA binding protein binds molybdate and tungstate but not other oxyanions such as sulfate and phosphate, making it the first class III molybdate binding protein structurally solved. The ~100 μM binding affinity...
A role for tungsten in the biology of Campylobacter jejuni: tungstate stimulates formate dehydrogenase activity and is transported via an ultra-high affinity ABC system distinct from the molybdate transporter.
Smart, Jonathan P; Cliff, Matthew J; Kelly, David J
The food-borne pathogen Campylobacter jejuni possesses no known tungstoenzymes, yet encodes two ABC transporters (Cj0300-0303 and Cj1538-1540) homologous to bacterial molybdate (ModABC) uptake systems and the tungstate transporter (TupABC) of Eubacterium acidaminophilum respectively. The actual substrates and physiological role of these transporters were investigated. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry of the purified periplasmic binding proteins of each system revealed that while Cj0303 is unable to discriminate between molybdate and tungstate (K(D) values for both ligands of 4-8 nM), Cj1540 binds tungstate with a K(D) of 1.0 +/- 0.2 pM; 50 000-fold more tightly than molybdate. Induction-coupled plasma mass spectroscopy of single and double mutants showed that this large difference in affinity is reflected in a lower cellular tungsten content in a cj1540 (tupA) mutant compared with a cj0303c (modA) mutant. Surprisingly, formate dehydrogenase (FDH) activity was decreased approximately 50% in the tupA strain, and supplementation of the growth medium with tungstate significantly increased FDH activity in the wild type, while inhibiting known molybdoenzymes. Our data suggest that C. jejuni possesses a specific, ultra-high affinity tungstate transporter that supplies tungsten for incorporation into FDH. Furthermore, possession of two MoeA paralogues may explain the formation of both molybdopterin and tungstopterin in this bacterium. PMID:19818021
The quorum-sensing molecule farnesol is a modulator of drug efflux mediated by ABC multidrug transporters and synergizes with drugs in Candida albicans.
Sharma, Monika; Prasad, Rajendra
Overexpression of the CaCDR1-encoded multidrug efflux pump protein CaCdr1p (Candida drug resistance protein 1), belonging to the ATP binding cassette (ABC) superfamily of transporters, is one of the most prominent contributors of multidrug resistance (MDR) in Candida albicans. Thus, blocking or modulating the function of the drug efflux pumps represents an attractive approach in combating MDR. In the present study, we provide first evidence that the quorum-sensing molecule farnesol (FAR) is a specific modulator of efflux mediated by ABC multidrug transporters, such as CaCdr1p and CaCdr2p of C. albicans and ScPdr5p of Saccharomyces cerevisiae. Interestingly, FAR did not modulate the efflux mediated by the multidrug extrusion pump protein CaMdr1p, belonging to the major facilitator superfamily (MFS). Kinetic data revealed that FAR competitively inhibited rhodamine 6G efflux in CaCdr1p-overexpressing cells, with a simultaneous increase in an apparent K(m) without affecting the V(max) values and the ATPase activity. We also observed that when used in combination, FAR at a nontoxic concentration synergized with the drugs at their respective nonlethal concentrations, as was evident from their resistant clinical isolates of C. albicans. Our biochemical experiments revealed that the synergistic interaction of FAR with the drugs led to reactive oxygen species accumulation, which triggered early apoptosis, and that both could be partly reversed by the addition of an antioxidant. Collectively, FAR modulates drug extrusion mediated exclusively by ABC proteins and is synergistic to fluconazole (FLC), ketoconazole (KTC), miconazole (MCZ), and amphotericin (AMB). PMID:21768514
Synthesis and characterization of a BODIPY conjugate of the BCR-ABL kinase inhibitor Tasigna® (Nilotinib): Evidence for transport of Tasigna® and its fluorescent derivative by ABC drug transporters
Shukla, Suneet; Skoumbourdis, Amanda P.; Walsh, Martin J.; Hartz, Anika M. S.; Fung, King Leung; Wu, Chung-pu; Gottesman, Michael M.; Bauer, Björn; Thomas, Craig J.; Suresh V Ambudkar
Tasigna® (Nilotinib) is a recently approved BCR-ABL kinase inhibitor by the Food and Drug Administration, which is indicated for the treatment of drug-resistant chronic myelogenous leukemia (CML). The efflux of tyrosine kinase inhibitors by ATP-binding cassette (ABC) drug transporters, which actively pump these drugs out of cells utilizing ATP as an energy source, has been linked to the development of drug resistance in CML patients. We report here synthesis and characterization of a fluoresc...
Quantitative Analysis of the Relative Transcript Levels of ABC Transporter Atr Genes in Aspergillus nidulans by Real-Time Reverse Transcription-PCR Assay
Pizeta Semighini, Camile; Marins, Mozart; Goldman, Maria Helena S.; Goldman, Gustavo Henrique
The development of assays for quantitative analysis of the relative transcript levels of ABC transporter genes by real-time reverse transcription-PCR (RT-PCR) might provide important information about multidrug resistance in filamentous fungi. Here, we evaluate the potential of real-time RT-PCR to quantify the relative transcript levels of ABC transporter Atr genes from Aspergillus nidulans. The AtrA to AtrD genes showed different and higher levels in the presence of structurally unrelated drugs, such as camptothecin, imazalil, itraconazole, hygromycin, and 4-nitroquinoline oxide. We also verified the relative transcript levels of the Atr genes in the A. nidulans imazalil-resistant mutants. These genes displayed a very complex pattern in different ima genetic backgrounds. The imaB mutant has higher basal transcript levels of AtrB and -D than those of the wild-type strain. The levels of these two genes are comparable when the imaB mutant is grown in the presence and absence of imazalil. The imaC, -D, and -H mutants have higher basal levels of AtrA than that of the wild type. The same behavior is observed for the relative transcript levels of AtrB in the imaG mutant background. PMID:11872487
Detergent screening and purification of the human liver ABC transporters BSEP (ABCB11 and MDR3 (ABCB4 expressed in the yeast Pichia pastoris.
Philipp Ellinger
Full Text Available The human liver ATP-binding cassette (ABC transporters bile salt export pump (BSEP/ABCB11 and the multidrug resistance protein 3 (MDR3/ABCB4 fulfill the translocation of bile salts and phosphatidylcholine across the apical membrane of hepatocytes. In concert with ABCG5/G8, these two transporters are responsible for the formation of bile and mutations within these transporters can lead to severe hereditary diseases. In this study, we report the heterologous overexpression and purification of human BSEP and MDR3 as well as the expression of the corresponding C-terminal GFP-fusion proteins in the yeast Pichia pastoris. Confocal laser scanning microscopy revealed that BSEP-GFP and MDR3-GFP are localized in the plasma membrane of P. pastoris. Furthermore, we demonstrate the first purification of human BSEP and MDR3 yielding ∼1 mg and ∼6 mg per 100 g of wet cell weight, respectively. By screening over 100 detergents using a dot blot technique, we found that only zwitterionic, lipid-like detergents such as Fos-cholines or Cyclofos were able to extract both transporters in sufficient amounts for subsequent functional analysis. For MDR3, fluorescence-detection size exclusion chromatography (FSEC screens revealed that increasing the acyl chain length of Fos-Cholines improved monodispersity. BSEP purified in n-dodecyl-β-D-maltoside or Cymal-5 after solubilization with Fos-choline 16 from P. pastoris membranes showed binding to ATP-agarose. Furthermore, detergent-solubilized and purified MDR3 showed a substrate-inducible ATPase activity upon addition of phosphatidylcholine lipids. These results form the basis for further biochemical analysis of human BSEP and MDR3 to elucidate the function of these clinically relevant ABC transporters.
An ABC Transporter Mutation Alters Root Exudation of Phytochemicals That Provoke an Overhaul of Natural Soil Microbiota1[C][W][OA
Badri, Dayakar V.; Quintana, Naira; El Kassis, Elie G.; Kim, Hye Kyong; Choi, Young Hae; Sugiyama, Akifumi; Verpoorte, Robert; Martinoia, Enrico; Manter, Daniel K.; Vivanco, Jorge M.
Root exudates influence the surrounding soil microbial community, and recent evidence demonstrates the involvement of ATP-binding cassette (ABC) transporters in root secretion of phytochemicals. In this study, we examined effects of seven Arabidopsis (Arabidopsis thaliana) ABC transporter mutants on the microbial community in native soils. After two generations, only the Arabidopsis abcg30 (Atpdr2) mutant had significantly altered both the fungal and bacterial communities compared with the wild type using automated ribosomal intergenic spacer analysis. Similarly, root exudate profiles differed between the mutants; however, the largest variance from the wild type (Columbia-0) was observed in abcg30, which showed increased phenolics and decreased sugars. In support of this biochemical observation, whole-genome expression analyses of abcg30 roots revealed that some genes involved in biosynthesis and transport of secondary metabolites were up-regulated, while some sugar transporters were down-regulated compared with genome expression in wild-type roots. Microbial taxa associated with Columbia-0 and abcg30 cultured soils determined by pyrosequencing revealed that exudates from abcg30 cultivated a microbial community with a relatively greater abundance of potentially beneficial bacteria (i.e. plant-growth-promoting rhizobacteria and nitrogen fixers) and were specifically enriched in bacteria involved in heavy metal remediation. In summary, we report how a single gene mutation from a functional plant mutant influences the surrounding community of soil organisms, showing that genes are not only important for intrinsic plant physiology but also for the interactions with the surrounding community of organisms as well. PMID:19854857
ABC Technology Development Program
The Accelerator-Based Conversion (ABC) facility will be designed to accomplish the following mission: 'Provide a weapon's grade plutonium disposition capability in a safe, economical, and environmentally sound manner on a prudent schedule for [50] tons of weapon's grade plutonium to be disposed on in [20] years.' This mission is supported by four major objectives: provide a reliable plutonium disposition capability within the next [15] years; provide a level of safety and of safety assurance that meets or exceeds that afforded to the public by modern commercial nuclear power plants; meet or exceed all applicable federal, state, and local regulations or standards for environmental compliance; manage the program in a cost effective manner. The ABC Technology Development Program defines the technology development activities that are required to accomplish this mission. The technology development tasks are related to the following topics: blanket system; vessel systems; reactivity control systems; heat transport system components; energy conversion systems; shutdown heat transport systems components; auxiliary systems; technology demonstrations - large scale experiments
A burst of ABC genes in the genome of the polyphagous spider mite Tetranychus urticae
Dermauw, W.; Osborne, E.J.; Clark, R.M.; Grbić, M.; Tirry, L.; Van Leeuwen, T
Background: The ABC (ATP-binding cassette) gene superfamily is widespread across all living species. The majority of ABC genes encode ABC transporters, which are membrane-spanning proteins capable of transferring substrates across biological membranes by hydrolyzing ATP. Although ABC transporters have often been associated with resistance to drugs and toxic compounds, within the Arthropoda ABC gene families have only been characterized in detail in several insects and a crustacean. In this st...
Increased expression of the yeast multidrug resistance ABC transporter Pdr18 leads to increased ethanol tolerance and ethanol production in high gravity alcoholic fermentation
Teixeira Miguel C
Full Text Available Abstract Background The understanding of the molecular basis of yeast tolerance to ethanol may guide the design of rational strategies to increase process performance in industrial alcoholic fermentations. A set of 21 genes encoding multidrug transporters from the ATP-Binding Cassette (ABC Superfamily and Major Facilitator Superfamily (MFS in S. cerevisiae were scrutinized for a role in ethanol stress resistance. Results A yeast multidrug resistance ABC transporter encoded by the PDR18 gene, proposed to play a role in the incorporation of ergosterol in the yeast plasma membrane, was found to confer resistance to growth inhibitory concentrations of ethanol. PDR18 expression was seen to contribute to decreased 3 H-ethanol intracellular concentrations and decreased plasma membrane permeabilization of yeast cells challenged with inhibitory ethanol concentrations. Given the increased tolerance to ethanol of cells expressing PDR18, the final concentration of ethanol produced during high gravity alcoholic fermentation by yeast cells devoid of PDR18 was lower than the final ethanol concentration produced by the corresponding parental strain. Moreover, an engineered yeast strain in which the PDR18 promoter was replaced in the genome by the stronger PDR5 promoter, leading to increased PDR18 mRNA levels during alcoholic fermentation, was able to attain a 6 % higher ethanol concentration and a 17 % higher ethanol production yield than the parental strain. The improved fermentative performance of yeast cells over-expressing PDR18 was found to correlate with their increased ethanol tolerance and ability to restrain plasma membrane permeabilization induced throughout high gravity fermentation. Conclusions PDR18 gene over-expression increases yeast ethanol tolerance and fermentation performance leading to the production of highly inhibitory concentrations of ethanol. PDR18 overexpression in industrial yeast strains appears to be a promising approach to
Identification of the minimal region in lipase ABC transporter recognition domain of Pseudomonas fluorescens for secretion and fluorescence of green fluorescent protein
Park Yeonwoo
Full Text Available Abstract Background TliA is a thermostable lipase secreted by the type 1 secretion system (T1SS of Pseudomonas fluorescens. The secretion is promoted by its secretion/chaperone domain located near the C-terminus, which is composed mainly of four Repeat-in-Toxin (RTX repeats. In order to identify the minimal region of TliA responsible for its secretion, five different copies of the secretion/chaperone domain, each involving truncated N-terminal residues and a common C-terminus, were acquired and named as lipase ABC transporter recognition domains (LARDs. Each LARD was fused to epidermal growth factor (EGF or green fluorescent protein (GFP, and the secretion of EGF-LARD or GFP-LARD fusion proteins was assessed in Escherichia coli with ABC transporter. Results Among the fusion proteins, GFP or EGF with 105-residue LARD3 was most efficiently secreted. In addition, GFP-LARD3 emitted wild type GFP fluorescence. Structurally, LARD3 had the 4 RTX repeats exposed at the N-terminus, while other LARDs had additional residues prior to them or missed some of the RTX repeats. LARD3 was both necessary and sufficient for efficient secretion and maintenance of GFP fluorescence in E. coli, which was also confirmed in P. fluorescens and P. fluorescens ▵tliA, a knock-out mutant of tliA. Conclusion LARD3 was a potent secretion signal in T1SS for its fusion flanking RTX motif, which enhanced secretion and preserved the fluorescence of GFP. LARD3-mediated secretion in E. coli or P. fluorescens will enable the development of enhanced protein manufacturing factory and recombinant microbe secreting protein of interest in situ.
Effects of in vitro exposure to ivermectin and levamisole on the expression patterns of ABC transporters in Haemonchus contortus larvae
Ali Raza
Full Text Available This study investigated the interaction of ATP binding cassette (ABC transport proteins with ivermectin (IVM and levamisole (LEV in larvae of susceptible and resistant isolates of Haemonchus contortus in vitro by measuring transcription patterns following exposure to these anthelmintics. Furthermore, we studied the consequences of drug exposure by measuring the sensitivity of L3 to subsequent exposure to higher drug concentrations using larval migration assays. The most highly transcribed transporter genes in both susceptible and resistant L3 were pgp-9.3, abcf-1, mrp-5, abcf-2, pgp-3, and pgp-10. The resistant isolate showed significantly higher transcription of pgp-1, pgp-9.1 and pgp-9.2 compared to the susceptible isolate. Five P-gp genes and the haf-6 gene showed significantly higher transcription (up to 12.6-fold after 3 h exposure to IVM in the resistant isolate. Similarly, five P-gp genes, haf-6 and abcf-1 were transcribed at significantly higher levels (up to 10.3-fold following 3 h exposure to LEV in this isolate. On the other hand, there were no significant changes in transcriptional patterns of all transporter genes in the susceptible isolate following 3 and 6 h exposure to IVM or LEV. In contrast to these isolate-specific transcription changes, both isolates showed an increase in R-123 efflux following exposure to the drugs, suggesting that the drugs stimulated activity of existing transporter proteins in both isolates. Exposure of resistant larvae to IVM or LEV resulted, in some instances, in an increase in the proportion of the population able to migrate at the highest IVM concentrations in subsequent migration assays. The significant increase in transcription of some ABC transporter genes following 3 h exposure to both IVM and LEV in the resistant isolate only, suggests that an ability to rapidly upregulate protective pathways in response to drugs may be a component of the resistance displayed by this isolate.
The Nucleotide-Free State of the Multidrug Resistance ABC Transporter LmrA: Sulfhydryl Cross-Linking Supports a Constant Contact, Head-to-Tail Configuration of the Nucleotide-Binding Domains.
Peter M Jones
Full Text Available ABC transporters are integral membrane pumps that are responsible for the import or export of a diverse range of molecules across cell membranes. ABC transporters have been implicated in many phenomena of medical importance, including cystic fibrosis and multidrug resistance in humans. The molecular architecture of ABC transporters comprises two transmembrane domains and two ATP-binding cassettes, or nucleotide-binding domains (NBDs, which are highly conserved and contain motifs that are crucial to ATP binding and hydrolysis. Despite the improved clarity of recent structural, biophysical, and biochemical data, the seemingly simple process of ATP binding and hydrolysis remains controversial, with a major unresolved issue being whether the NBD protomers separate during the catalytic cycle. Here chemical cross-linking data is presented for the bacterial ABC multidrug resistance (MDR transporter LmrA. These indicate that in the absence of nucleotide or substrate, the NBDs come into contact to a significant extent, even at 4°C, where ATPase activity is abrogated. The data are clearly not in accord with an inward-closed conformation akin to that observed in a crystal structure of V. cholerae MsbA. Rather, they suggest a head-to-tail configuration 'sandwich' dimer similar to that observed in crystal structures of nucleotide-bound ABC NBDs. We argue the data are more readily reconciled with the notion that the NBDs are in proximity while undergoing intra-domain motions, than with an NBD 'Switch' mechanism in which the NBD monomers separate in between ATP hydrolysis cycles.
The Half-Size ABC Transporter FOLDED PETALS 2/ABCG13 Is Involved in Petal Elongation through Narrow Spaces in Arabidopsis thaliana Floral Buds
Seiji Takeda
Full Text Available Flowers are vital for attracting pollinators to plants and in horticulture for humans. Petal morphogenesis is a central process of floral development. Petal development can be divided into three main processes: the establishment of organ identity in a concentric pattern, primordia initiation at fixed positions within a whorl, and morphogenesis, which includes petal elongation through the narrow spaces within the bud. Here, we show that the FOLDED PETALS 2 (FOP2 gene, encoding a member of the half-size ATP binding cassette (ABC transporter family ABCG13, is involved in straight elongation of petals in Arabidopsis thaliana. In fop2 mutants, flowers open with folded petals, instead of straight-elongated ones found in the wild type. The epicuticular nanoridge structures are absent in many abaxial epidermal cells of fop2 petals, and surgical or genetic generation of space in young fop2 buds restores the straight elongation of petals, suggesting that the physical contact of sepals and petals causes the petal folding. Similar petal folding has been reported in the fop1 mutant, and the petals of fop2 fop1 double mutants resemble those of both the fop1 and fop2 single mutants, although the epidermal structure and permeability of the petal surface is more affected in fop2. Our results suggest that synthesis and transport of cutin or wax in growing petals play an important role for their smooth elongation through the narrow spaces of floral buds.
ABC Kinga kauplused = ABC King shoe stores
Tallinnas Kristiine keskuses, Tartu Kaubamajas ja Pärnus Port Artur 2 asuvate ABC Kinga kaupluste sisekujundusest. Sisearhitekid Andres Labi ja Janno Roos (Ruumilabor OÜ), loetletud nende ühiselt tehtud töid
75 FR 49549 - ABC & D Recycling, Inc.-Lease and Operation Exemption-a Line of Railroad in Ware, MA
... Surface Transportation Board ABC & D Recycling, Inc.--Lease and Operation Exemption--a Line of Railroad in Ware, MA ABC & D Recycling, Inc. (ABC & D), a noncarrier, has filed a verified notice of exemption... operation of this trackage in FD 35356, ABC & D Recycling, Inc.--Lease and Operation Exemption--a Line...
Multidrug resistance mediated by ABC transporters in osteosarcoma cell lines: mRNA analysis and functional radiotracer studies
Gomes, Celia Maria Freitas [Department of Pathology, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Faculty of Medicine, Institute of Biophysics/Biomathematics, IBILI, 3000-354 Coimbra (Portugal)]. E-mail: firstname.lastname@example.com; van Paassen, Heidi [Department of Pathology, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Romeo, Salvatore [Department of Pathology, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Welling, Mick M. [Department of Radiology, Section of Nuclear Medicine, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Feitsma, R.I.J. [Department of Radiology, Section of Nuclear Medicine, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Abrunhosa, Antero J. [Faculty of Medicine, Institute of Biophysics/Biomathematics, IBILI, 3000-354 Coimbra (Portugal); Botelho, M. Filomena [Faculty of Medicine, Institute of Biophysics/Biomathematics, IBILI, 3000-354 Coimbra (Portugal); Hogendoorn, Pancras C.W. [Department of Pathology, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Pauwels, Ernest [Department of Radiology, Section of Nuclear Medicine, Leiden University Medical Center, 2300 RC Leiden (Netherlands); Cleton-Jansen, Anne Marie [Department of Pathology, Leiden University Medical Center, 2300 RC Leiden (Netherlands)
Drug resistance remains a significant impediment to successful chemotherapy and constitutes a major prognostic factor in osteosarcoma (OS) patients. This study was designed to identify the role and prognostic significance of multidrug-resistance (MDR)-related transporters, such as multidrug resistance protein 1 (MDR1), multidrug-resistance-associated protein (MRP1) and breast-cancer-related protein (BCRP), in OS using cationic lipophilic radiotracers. We evaluated the chemosensitivity of four OS cell lines (Saos-2, 143B, MNNG/HOS and U-2OS) to doxorubicin (DOX), cisplatin (CIS) and methotrexate. The expression of MDR-related transporters was analyzed at mRNA level by quantitative polymerase chain reaction and at functional level by {sup 99m}Tc sestamibi and {sup 99m}Tc tetrofosmin. The effectiveness of MDR modulators [cyclosporin A (CsA) and imatinib] on transporter inhibition and on the reversal of resistance was also assessed. MNNG/HOS and U-2OS cells expressing high levels of MDR1 were highly resistant to DOX and showed reduced accumulation and higher efflux for radiotracers. Although MRP1 was uniformly expressed in all cells, only U-2OS was resistant to CIS. CsA restored sensitivity to DOX and CIS, and enhanced the accumulation and efflux half-life of radiotracers in MDR1-expressing cell lines. The chemosensitivity of OS cells to DOX was strongly dependent on mRNA MDR1 expression and could be circumvented by adding CsA. The kinetic parameters of radiotracers correlated with MDR1 expression levels, hence predicting DOX resistance. We concluded that sensitivity to chemotherapy is strongly dependent on the expression of MDR1 transporter and that radiotracer studies could prove clinically useful in predicting chemotherapy response and in evaluating the efficacy of MDR-reversing agents.
Diversity and evolution of ABC proteins in mycorrhiza-forming fungi
Kohler, Annegret; Martin, Francis; Asiegbu, Fred O
Background Transporter proteins are predicted to have an important role in the mycorrhizal symbiosis, due to the fact that this type of an interaction between plants and fungi requires a continuous nutrient and signalling exchange. ABC transporters are one of the large groups of transporter proteins found both in plants and in fungi. The crucial role of plant ABC transporters in the formation of the mycorrhizal symbiosis has been demonstrated recently. Some of the fungal ABC transporter-encod...
The cystic-fibrosis-associated ΔF508 mutation confers post-transcriptional destabilization on the C. elegans ABC transporter PGP-3
Liping He
Membrane proteins make up ∼30% of the proteome. During the early stages of maturation, this class of proteins can experience localized misfolding in distinct cellular compartments, such as the cytoplasm, endoplasmic reticulum (ER lumen and ER membrane. ER quality control (ERQC mechanisms monitor folding and determine whether a membrane protein is appropriately folded or is misfolded and warrants degradation. ERQC plays crucial roles in human diseases, such as cystic fibrosis, in which deletion of a single amino acid (F508 results in the misfolding and degradation of the cystic fibrosis transmembrane conductance regulator (CFTR Cl– channel. We introduced the ΔF508 mutation into Caenorhabditis elegans PGP-3, a 12-transmembrane ABC transporter with 15% identity to CFTR. When expressed in intestinal epithelial cells, PGP-3wt was stable and efficiently trafficked to the apical plasma membrane through a COPII-dependent mechanism. However, PGP-3ΔF508 was post-transcriptionally destabilized, resulting in reduced total and apical membrane protein levels. Genetic or physiological activation of the osmotic stress response pathway, which causes accumulation of the chemical chaperone glycerol, stabilized PGP-3ΔF508. Efficient degradation of PGP-3ΔF508 required the function of several C. elegans ER-associated degradation (ERAD homologs, suggesting that destabilization occurs through an ERAD-type mechanism. Our studies show that the ΔF508 mutation causes post-transcriptional destabilization and degradation of PGP-3 in C. elegans epithelial cells. This model, combined with the power of C. elegans genetics, provides a new opportunity to genetically dissect metazoan ERQC.
A Putative ABC Transporter Permease Is Necessary for Resistance to Acidified Nitrite and EDTA in Pseudomonas aeruginosa under Aerobic and Anaerobic Planktonic and Biofilm Conditions
McDaniel, Cameron; Su, Shengchang; Panmanee, Warunya; Lau, Gee W.; Browne, Tristan; Cox, Kevin; Paul, Andrew T.; Ko, Seung-Hyun B.; Mortensen, Joel E.; Lam, Joseph S.; Muruve, Daniel A.; Hassett, Daniel J.
Pseudomonas aeruginosa (PA) is an important airway pathogen of cystic fibrosis and chronic obstructive disease patients. Multiply drug resistant PA is becoming increasing prevalent and new strategies are needed to combat such insidious organisms. We have previously shown that a mucoid, mucA22 mutant PA is exquisitely sensitive to acidified nitrite (A-NO2−, pH 6.5) at concentrations that are well tolerated in humans. Here, we used a transposon mutagenesis approach to identify PA mutants that are hypersensitive to A-NO2−. Among greater than 10,000 mutants screened, we focused on PA4455, in which the transposon was found to disrupt the production of a putative cytoplasmic membrane-spanning ABC transporter permease. The PA4455 mutant was not only highly sensitive to A-NO2−, but also the membrane perturbing agent, EDTA and the antibiotics doxycycline, tigecycline, colistin, and chloramphenicol, respectively. Treatment of bacteria with A-NO2− plus EDTA, however, had the most dramatic and synergistic effect, with virtually all bacteria killed by 10 mM A-NO2−, and EDTA (1 mM, aerobic, anaerobic). Most importantly, the PA4455 mutant was also sensitive to A-NO2− in biofilms. A-NO2− sensitivity and an anaerobic growth defect was also noted in two mutants (rmlC and wbpM) that are defective in B-band LPS synthesis, potentially indicating a membrane defect in the PA4455 mutant. Finally, this study describes a gene, PA4455, that when mutated, allows for dramatic sensitivity to the potential therapeutic agent, A-NO2− as well as EDTA. Furthermore, the synergy between the two compounds could offer future benefits against antibiotic resistant PA strains. PMID:27064218
Full Text Available ... among people with diabetes. Judith Fradkin, M.D.: We call this approach "the ABCs of diabetes." A ... the importance of all three of these and we know that controlling the three can dramatically reduce ...
Full Text Available ... just live to survive. Announcer: People with diabetes should work with their doctors to monitor the ABCs ... my A1C, my blood pressure, my cholesterol, what should it be" "and what can I do to ...
Full Text Available ... Announcer: People with diabetes should work with their doctors to monitor the ABCs of diabetes. Judith Fradkin, ... want patients who have diabetes to ask their doctors, "What is my A1C, my blood pressure, my ...
Full Text Available ... the importance of blood pressure, cholesterol and diabetes management to prevent heart attacks and strokes. Sharon Boykin: ... Knowing your ABCs will help you reduce your risk of heart attack and stroke to live a ...
Full Text Available ... between diabetes and heart disease. Judith Fradkin, M.D.: What most people don't know is that ... stroke among people with diabetes. Judith Fradkin, M.D.: We call this approach "the ABCs of diabetes." ...
Full Text Available ... prevent two of the disease's most serious complications. John Buse, M.D.: As the population ages, we ... of living -- your living conditions will be better. John Buse, M.D.: Knowing your ABCs will help ...
Full Text Available ... As the population ages, we would expect some increase in the proportion of people with diabetes and ... ABC numbers are, you'll be able to help save your own life -- the lower they are, ...
The ABC of cholesterol transport
Plösch, Torsten
Cholesterol fulfills an indispensable role in mammalian physiology. It is an important constituent of all cell membranes. Furthermore, it is the precursor of steroid hormones, which regulate a variety of physiological functions, and of bile salts, which are necessary for the generation of bile flow
Full Text Available ... somebody who's already had a heart attack. Announcer: Research shows that controlling blood sugar, blood pressure and cholesterol are critical in preventing heart disease and stroke among people with diabetes. Judith Fradkin, M.D.: We call this approach "the ABCs of diabetes." A is the A1C, ...
Full Text Available ... are at the same risk for heart disease as somebody who's already had a heart attack. Announcer: Research shows that controlling blood ... We call this approach "the ABCs of diabetes." A is the A1C, a measure of how well ...
Wiese, Lars Ole
I denne artikel diskuteres Activity Based Costing (ABC) som rapporterings-teknik for kunde profitabilitet. Der argumenteres for, at indtægtserhvervel-sen inkl. dens direkte omkostningsforbrug bør adskilles fra omkostnings-beskrivelsen til produktfremstilling. Dvs. der gennemføres en aktivitetsba...
The Tangier disease gene product ABC1 controls the cellular apolipoprotein-mediated lipid removal pathway
Lawn, Richard M.; Wade, David P.; Garvin, Michael R.; Wang, Xingbo; Schwartz, Karen; Porter, J. Gordon; Seilhamer, Jeffrey J.; Ashley M Vaughan; Oram, John F.
The ABC1 transporter was identified as the defect in Tangier disease by a combined strategy of gene expression microarray analysis, genetic mapping, and biochemical studies. Patients with Tangier disease have a defect in cellular cholesterol removal, which results in near zero plasma levels of HDL and in massive tissue deposition of cholesteryl esters. Blocking the expression or activity of ABC1 reduces apolipoprotein-mediated lipid efflux from cultured cells, and increasing expression of ABC...
Flavonoid-mediated inhibition of intestinal ABC transporters may affect the oral bioavailability of drugs, food-borne toxic compounds and bioactive ingredients
Brand, W.; Schutte, M.E.; Bladeren, van P.J.; Rietjens, I.M.C.M.
The transcellular transport of ingested food ingredients across the intestinal epithelial barrier is an important factor determining bioavailability upon oral intake. This transcellular transport of many chemicals, food ingredients, drugs or toxic compounds over the intestinal epithelium can be high
ABCs in College English Education
As is known to us all, human beings are always brought under control by such many things as the hormone in our body, the mood produced in our brain and the external world, which leads us to a topic of how to create an atmosphere for the undergraduates to fit well in with the college English education. In our teaching management, the ABCs about college English education works as an assistant. Here, ABCs about college English education refer to some fundamental skills with regard to the undergraduates English education. The ABCs, which always encourage students' involvement, would work effectively if teachers understand them well.
Genome-wide comparative analysis of ABC systems in the Bdellovibrio-and-like organisms.
Li, Nan; Chen, Huan; Williams, Henry N
Bdellovibrio-and-like organisms (BALOs) are gram-negative, predatory bacteria with wide variations in genome sizes and GC content and ecological habitats. The ATP-binding cassette (ABC) systems have been identified in several prokaryotes, fungi and plants and have a role in transport of materials in and out of cells and in cellular processes. However, knowledge of the ABC systems of BALOs remains obscure. A total of 269 putative ABC proteins were identified in BALOs. The genes encoding these ABC systems occupy nearly 1.3% of the gene content in freshwater Bdellovibrio strains and about 0.7% in their saltwater counterparts. The proteins found belong to 25 ABC system families based on their structural characteristics and functions. Among these, 16 families function as importers, 6 as exporters and 3 are involved in various cellular processes. Eight of these 25 ABC system families were deduced to be the core set of ABC systems conserved in all BALOs. All Bacteriovorax strains have 28 or less ABC systems. On the contrary, the freshwater Bdellovibrio strains have more ABC systems, typically around 51. In the genome of Bdellovibrio exovorus JSS (CP003537.1), 53 putative ABC systems were detected, representing the highest number among all the BALO genomes examined in this study. Unexpected high numbers of ABC systems involved in cellular processes were found in all BALOs. Phylogenetic analysis suggests that the majority of ABC proteins can be assigned into many separate families with high bootstrap supports (>50%). In this study, a general framework of sequence-structure-function connections for the ABC systems in BALOs was revealed providing novel insights for future investigations. PMID:25707746
Politseiniku lustlik ABC / Pekka Erelt
Erelt, Pekka, 1965-
Politsei on välja andnud 'Politseiniku ABC', mis antakse igale politseinikule. Karikaturist Heiki Ernits on peaaegu igale taskuraamatu leheküljele joonistanud pildikese mundrimeestest kentsakates situatsioonides.
The ABC of Ribosome-Related Antibiotic Resistance
Wilson, Daniel N.
ABSTRACT The increase in multidrug-resistant pathogenic bacteria is limiting the utility of our current arsenal of antimicrobial agents. Mechanistically understanding how bacteria obtain antibiotic resistance is a critical first step to the development of improved inhibitors. One common mechanism for bacteria to obtain antibiotic resistance is by employing ATP-binding cassette (ABC) transporters to actively pump the drug from the cell. The ABC-F family includes proteins conferring resistance to a variety of clinically important ribosome-targeting antibiotics; however, controversy remains as to whether resistance is conferred via efflux like other ABC transporters or whether another mechanism, such as ribosome protection, is at play. A recent study by Sharkey and coworkers (L. K. Sharkey, T. A. Edwards, and A. J. O'Neill, mBio 7:e01975-15, 2016, http://dx.doi.org/10.1128/mBio.01975-15) provides strong evidence that ABC-F proteins conferring antibiotic resistance utilize ribosome protection mechanisms, namely, by interacting with the ribosome and displacing the drug from its binding site, thus revealing a novel role for ABC-F proteins in antibiotic resistance. PMID:27143393
Purification, crystallization and preliminary X-ray analysis of the galacto-N-biose-/lacto-N-biose I-binding protein (GL-BP) of the ABC transporter from Bifidobacterium longum JCM1217
Preliminary X-ray analysis of the galacto-N-biose-/lacto-N-biose I-binding protein (GL-BP) of the ABC transporter from B. longum is described. A recombinant galacto-N-biose-/lacto-N-biose I-binding protein (GL-BP) from Bifidobacterium longum JCM1217 has been prepared and crystallized by the hanging-drop vapour-diffusion method using 10 mg ml−1 purified enzyme, 0.01 M zinc sulfate, 0.1 M MES buffer pH 5.9–6.4 and 20–22%(v/v) PEG MME 550 in the presence of 5 mM disaccharide ligands. Suitable crystals grew after 10 d incubation at 293 K. The crystals belong to space group C2221, with unit-cell parameters a = 106.3, b = 143.6, c = 114.6 Å for the lacto-N-biose I complex and a = 106.4, b = 143.4, c = 115.5 Å for the galacto-N-biose complex, and diffracted to 1.85 and 1.99 Å resolution, respectively
The multidrug ABC transporter BmrC/BmrD of Bacillus subtilis is regulated via a ribosome-mediated transcriptional attenuation mechanism
Reilman, Ewoud; Mars, Ruben A. T.; van Dijl, Jan Maarten; Denham, Emma L.
Expression of particular drug transporters in response to antibiotic pressure is a critical element in the development of bacterial multidrug resistance, and represents a serious concern for human health. To obtain a better understanding of underlying regulatory mechanisms, we have dissected the tra
Prognostic impact of high ABC transporter activity in 111 adult acute myeloid leukemia patients with normal cytogenetics when compared to FLT3, NPM1, CEBPA and BAALC.
Hirsch, Pierre; Tang, Ruoping; Marzac, Christophe; Perrot, Jean-Yves; Fava, Fanny; Bernard, Chantal; Jeziorowska, Dorota; Marie, Jean Pierre; Legrand, Ollivier
ATP-binding cassette transporter (and specially P-glycoprotein) activity is a well known prognostic factor in acute myeloid leukemia, but when compared to other molecular markers its prognostic value has not been well studied. Here we study relationships between this activity, fms-like tyro-sine kinase 3(FLT3/ITD), nucleophosmin(NPM1), CAAT-enhancer binding protein alpha(CEBPα), and brain and acute leukemia cytoplasmic protein (BAALC), in 111 patients with normal cytogenetics who underwent the same treatment, and evaluate its prognostic impact. Independent factors for survival were age (P=0.0126), ATP-binding cassette transporter activity (P=0.018) and duplications in the fms-like tyrosine kinase 3 (P=0.0273). In the 66 patients without fms-like tyrosine kinase 3 duplication and without nucleophosmin mutation, independent prognostic factors for complete remission achievement and survival were age and ATP-binding cassette transporter activity. In conclusion, ATP-binding cassette transporter activity remains an independent prognostic factor, and could assist treatment decisions in patients with no nucleophosmin mutation and no fms-like tyrosine kinase 3 duplication. PMID:22058196
Prognostic impact of high ABC transporter activity in 111 adult acute myeloid leukemia patients with normal cytogenetics when compared to FLT3, NPM1, CEBPA and BAALC
Hirsch, Pierre; Tang, Ruoping; Marzac, Christophe; Perrot, Jean-Yves; FAVA, FANNY; Bernard, Chantal; Jeziorowska, Dorota; MARIE, JEAN PIERRE; Legrand, Ollivier
ATP-binding cassette transporter (and specially P-glycoprotein) activity is a well known prognostic factor in acute myeloid leukemia, but when compared to other molecular markers its prognostic value has not been well studied. Here we study relationships between this activity, fms-like tyro-sine kinase 3(FLT3/ITD), nucleophosmin(NPM1), CAAT-enhancer binding protein alpha(CEBPα), and brain and acute leukemia cytoplasmic protein (BAALC), in 111 patients with normal cytogenetics who underwent th...
Trehalose-recycling ABC transporter LpqY-SugA-SugB-SugC is essential for virulence of Mycobacterium tuberculosis
Kalscheuer, Rainer; Weinrick, Brian; Veeraraghavan, Usha; Besra, Gurdyal S; Jacobs, William R.
Mycobacterium tuberculosis (Mtb) is an exclusively human pathogen that proliferates within phagosomes of host phagocytes. Host lipids are believed to provide the major carbon and energy sources for Mtb, with only limited availability of carbohydrates. There is an apparent paradox because five putative carbohydrate uptake permeases are present in Mtb, but there are essentially no host carbohydrates inside phagosomes. Nevertheless, carbohydrate transporters have been implicated in Mtb pathogene...
The maize glossy13 gene, cloned via BSR-Seq and Seq-walking encodes a putative ABC transporter required for the normal accumulation of epicuticular waxes.
Li Li
Full Text Available Aerial plant surfaces are covered by epicuticular waxes that among other purposes serve to control water loss. Maize glossy mutants originally identified by their "glossy" phenotypes exhibit alterations in the accumulation of epicuticular waxes. By combining data from a BSR-Seq experiment and the newly developed Seq-Walking technology, GRMZM2G118243 was identified as a strong candidate for being the glossy13 gene. The finding that multiple EMS-induced alleles contain premature stop codons in GRMZM2G118243, and the one knockout allele of gl13, validates the hypothesis that gene GRMZM2G118243 is gl13. Consistent with this, GRMZM2G118243 is an ortholog of AtABCG32 (Arabidopsis thaliana, HvABCG31 (barley and OsABCG31 (rice, which encode ABCG subfamily transporters involved in the trans-membrane transport of various secondary metabolites. We therefore hypothesize that gl13 is involved in the transport of epicuticular waxes onto the surfaces of seedling leaves.
Cadmium-inducible expression of the ABC-type transporter AtABCC3 increases phytochelatin-mediated cadmium tolerance in Arabidopsis
Brunetti, Patrizia; Zanella, Letizia; De Paolis, Angelo; Di Litta, Davide; Cecchetti, Valentina; Falasca, Giuseppina; Barbieri, Maurizio; Altamura, Maria Maddalena; Costantino, Paolo; Cardarelli, Maura
The heavy metal cadmium (Cd) is a widespread environmental contaminant with harmful effects on living cells. In plants, phytochelatin (PC)-dependent Cd detoxification requires that PC–Cd complexes are transported into vacuoles. Here, it is shown that Arabidopsis thaliana seedlings defective in the ABCC transporter AtABCC3 (abcc3) have an increased sensitivity to different Cd concentrations, and that seedlings overexpressing AtABCC3 (AtABCC3ox) have an increased Cd tolerance. The cellular distribution of Cd was analysed in protoplasts from abcc3 mutants and AtABCC3 overexpressors grown in the presence of Cd, by means of the Cd-specific fluorochromes 5-nitrobenzothiazole coumarin (BTC-5N) and Leadmium™ Green AM dye. This analysis revealed that Cd is mostly localized in the cytosol of abcc3 mutant protoplasts whereas there is an increase in vacuolar Cd in protoplasts from AtABCC3ox plants. Overexpression of AtABCC3 in cad1-3 mutant seedlings defective in PC production and in plants treated with l-buthionine sulphoximine (BSO), an inhibitor of PC biosynthesis, had no effect on Cd tolerance, suggesting that AtABCC3 acts via PCs. In addition, overexpression of AtABCC3 in atabcc1 atabcc2 mutant seedlings defective in the Cd transporters AtABCC1 and AtABCC2 complements the Cd sensitivity of double mutants, but not in the presence of BSO. Accordingly, the level of AtABCC3 transcript in wild type seedlings was lower than that of AtABCC1 and AtABCC2 in the absence of Cd but higher after Cd exposure, and even higher in atabcc1 atabcc2 mutants. The results point to AtABCC3 as a transporter of PC–Cd complexes, and suggest that its activity is regulated by Cd and is co-ordinated with the activity of AtABCC1/AtABCC2. PMID:25900618
Cadmium-inducible expression of the ABC-type transporter AtABCC3 increases phytochelatin-mediated cadmium tolerance in Arabidopsis.
Brunetti, Patrizia; Zanella, Letizia; De Paolis, Angelo; Di Litta, Davide; Cecchetti, Valentina; Falasca, Giuseppina; Barbieri, Maurizio; Altamura, Maria Maddalena; Costantino, Paolo; Cardarelli, Maura
The heavy metal cadmium (Cd) is a widespread environmental contaminant with harmful effects on living cells. In plants, phytochelatin (PC)-dependent Cd detoxification requires that PC-Cd complexes are transported into vacuoles. Here, it is shown that Arabidopsis thaliana seedlings defective in the ABCC transporter AtABCC3 (abcc3) have an increased sensitivity to different Cd concentrations, and that seedlings overexpressing AtABCC3 (AtABCC3ox) have an increased Cd tolerance. The cellular distribution of Cd was analysed in protoplasts from abcc3 mutants and AtABCC3 overexpressors grown in the presence of Cd, by means of the Cd-specific fluorochromes 5-nitrobenzothiazole coumarin (BTC-5N) and Leadmium™ Green AM dye. This analysis revealed that Cd is mostly localized in the cytosol of abcc3 mutant protoplasts whereas there is an increase in vacuolar Cd in protoplasts from AtABCC3ox plants. Overexpression of AtABCC3 in cad1-3 mutant seedlings defective in PC production and in plants treated with l-buthionine sulphoximine (BSO), an inhibitor of PC biosynthesis, had no effect on Cd tolerance, suggesting that AtABCC3 acts via PCs. In addition, overexpression of AtABCC3 in atabcc1 atabcc2 mutant seedlings defective in the Cd transporters AtABCC1 and AtABCC2 complements the Cd sensitivity of double mutants, but not in the presence of BSO. Accordingly, the level of AtABCC3 transcript in wild type seedlings was lower than that of AtABCC1 and AtABCC2 in the absence of Cd but higher after Cd exposure, and even higher in atabcc1 atabcc2 mutants. The results point to AtABCC3 as a transporter of PC-Cd complexes, and suggest that its activity is regulated by Cd and is co-ordinated with the activity of AtABCC1/AtABCC2. PMID:25900618
稻瘟病菌ABC转运蛋白基因中SSR的分布及其功能预测%SSR distribution and its potential effects on function of ABC transporter genes in rice blast fungus Magnaporthe grisea
刘林; 李成云; 杨静; 苏源; 吴晗; 徐玲; 胡燕玲
ABC transporters play an important role in pathogenicity of fungi. In this study, 47 ABC transporter genes were retrieved from the genome of Magnaporthe grisea. The component and distribution of simple sequence repeats (SSR) within the extron, intron, 5'-UTR and 3'-UTR regions of these genes were analyzed respectively. Furthermore, effects of SSR expansion and contraction on protein structure in the gene coding regions was predicted. The results showed that component and distribution of the SSRs in these regions were different and the SSRs also distributed unevenly in regulation and function regions of these genes. Compared with other regions, the tri-nucleotide and hexa-nucleotide appeared more frequently in coding region. In addition, the G + C component was more abundant and the frequency of hydrophilic amino acids was relatively higher than that of hydrophobic amino acids in the SSRs. Depending on the variation among field isolates of M. Grisea, the expansion or contraction of amino acids encoding SSR sequence were potentially affected on protein secondary structure and gene function. These data implicated that the mutation of SSR might play an important role in variation of pathogenicity-related genes.%ABC转运蛋白在真菌的致病性方面起着重要的作用.本研究查找和分析了稻瘟病菌基因组中47个ABC转运蛋白基因的外显子区、内含子区、5′-UTR和3′-UTR区中的SSR,并对编码区中SSR的扩张或收缩对蛋白结构的影响进行了预测.结果表明,SSR在这些基因的调控区和编码区分布不均一,且在基因的外显子区、内含子区、5′-UTR和3′-UTR区中SSR的组成和分布均不相同;基因的编码区中三碱基和六碱基SSR相对较多,SSR的基序大都表现为GC含量较高,编码的亲水性氨基酸出现频率远远高于疏水性氨基酸.根据稻瘟病菌自然群体中SSR的变化幅度,预测了SSR的扩张或收缩对蛋白二级结构的影响,发现SSR的扩张或收�
The ABCs of Student Engagement
Parsons, Seth A.; Nuland, Leila Richey; Parsons, Allison Ward
Student engagement is an important consideration for teachers and administrators because it is explicitly associated with achievement. What the authors call the ABC's of engagement they outline as: Affective engagement, Behavioral engagement, and Cognitive engagement. They also present "Three Things Every Teacher Needs to Know about…
75 FR 11991 - ABC & D Recycling, Inc.-Lease and Operation Exemption-a Line of Railroad in Ware, MA
... Surface Transportation Board ABC & D Recycling, Inc.--Lease and Operation Exemption--a Line of Railroad in... under 49 CFR 1150.31 to lease from O'Riley Family Trust (O'Riley), and to operate 773 feet of rail line... lease and operate the railroad trackage owned by O'Riley. ABC & D states that it has and intends...
Sustaining an Effective ABC-ABM System
Gary COKINS
Full Text Available The purpose of this paper is to describe the Activity- Based Costing (ABC and Activity-Based Management (ABM system and techniques to sustain them as a permanent and repeatable production reporting system, not just for one-off analysis. A comparison is made between ABC/ABM modeling software that extracts source data and business systems that include ABC/ABM modeling features. There are presented the stages of updating, running and rerunning the ABC/ABM system. The resulting information calculated and provided by the ABC/ABM system are analyzed and interpreted in terms of a multidimensional data analysis. The article ends with the authors' conclusions about the benefits of continued operation of sustaining the ABC/ABM system.
ABC model and floral evolution
LI Guisheng; MENG Zheng; KONG Hongzhi; CHEN Zhiduan; LU Anming
The paper introduces the classical ABC model of floral development and thereafter ABCD, ABCDE and quartet models, and presents achievements in the studies on floral evolution such as the improved understanding on the relationship of reproductive organs between gnetophytes and angiosperms, new results in perianth evolution and identified homology of floral organs between dicots and monocots. The evo-devo studies on plant taxa at different evolutionary levels are useful to better understanding the homology of floral organs, and to clarifying the mysteries of the origin and subsequent diversification of flowers.
Learning the ABCs: Activity based costing in waste operations
The United States Department of Energy (DOE) is facing a challenging new national role based on current world events, changing public perception and awareness, and a legacy of wastes generated in the past. Clearly, the DOE must put mechanisms in place to comply with environmental rules, regulations, and good management practices so that public health risk is minimized while programmatic costs are controlled. DOE has begun this process and has developed a Five-Year Plan to describe the activities necessary to comply with both cleanup, or environmental restoration, and waste management of existing waste streams. The focus of this paper is how to best manage the treatment, storage, disposal, and transportation of waste throughout the DOE weapons complex by using Activity Based Costing (ABC) to both plan and control expenditures in DOE Waste Management (WM). The basics of ABC, along with an example, will be detailed. (author)
Garcia, Luiz Henrique Costa, E-mail: email@example.com [Associacao de Medicina Intensiva Brasileira (AMIB), Sao Paulo, SP (Brazil); Irmandade da Santa Casa de Misericordia de Sao Paulo, SP (Brazil); Ferreira, Bruna Cortez [Hospital de Base de Sao Jose do Rio Preto, SP (Brazil)
The present study was aimed at proposing a systematic evaluation of cranial computed tomography, identifying the main aspects to be analyzed in order to facilitate the decision making process regarding diagnosis and management in emergency settings. The present descriptive study comprised a literature review at the following databases: Access Medicine and Access Emergency Medicine (McGraw-Hill Education); British Medical Journal Evidence Center; UptoDate; Bireme; PubMed; Lilacs; SciELO; ProQuest; Micromedex (Thomson Reuters); Embase. Once the literature review was completed, the authors identified the main diseases with tomographic repercussions and proposed the present system to evaluate cranial computed tomography images. An easy-to-memorize ABC system will facilitate the decision making in emergency settings, as it covers the main diseases encountered by intensivists and emergency physicians, and provides a sequential guidance about anatomical structures to be investigated as well as their respective alterations. (author)
Garcia, Luiz Henrique Costa; Ferreira, Bruna Cortez
The present study was aimed at proposing a systematic evaluation of cranial computed tomography, identifying the main aspects to be analyzed in order to facilitate the decision making process regarding diagnosis and management in emergency settings. The present descriptive study comprised a literature review at the following databases: Access Medicine and Access Emergency Medicine (McGraw- Hill Education); British Medical Journal Evidence Center; UptoDate; Bireme; PubMed; Lilacs; SciELO; ProQuest; Micromedex (Thomson Reuters); Embase. Once the literature review was completed, the authors identified the main diseases with tomographic repercussions and proposed the present system to evaluate cranial computed tomography images. An easy-to-memorize ABC system will facilitate the decision making in emergency settings, as it covers the main diseases encountered by intensivists and emergency physicians, and provides a sequential guidance about anatomical structures to be investigated as well as their respective alterations. PMID:25987751
The present study was aimed at proposing a systematic evaluation of cranial computed tomography, identifying the main aspects to be analyzed in order to facilitate the decision making process regarding diagnosis and management in emergency settings. The present descriptive study comprised a literature review at the following databases: Access Medicine and Access Emergency Medicine (McGraw-Hill Education); British Medical Journal Evidence Center; UptoDate; Bireme; PubMed; Lilacs; SciELO; ProQuest; Micromedex (Thomson Reuters); Embase. Once the literature review was completed, the authors identified the main diseases with tomographic repercussions and proposed the present system to evaluate cranial computed tomography images. An easy-to-memorize ABC system will facilitate the decision making in emergency settings, as it covers the main diseases encountered by intensivists and emergency physicians, and provides a sequential guidance about anatomical structures to be investigated as well as their respective alterations. (author)
Luiz Henrique Costa Garcia
Full Text Available The present study was aimed at proposing a systematic evaluation of cranial computed tomography, identifying the main aspects to be analyzed in order to facilitate the decision making process regarding diagnosis and management in emergency settings. The present descriptive study comprised a literature review at the following databases: Access Medicine and Access Emergency Medicine (McGraw- Hill Education; British Medical Journal Evidence Center; UptoDate; Bireme; PubMed; Lilacs; SciELO; ProQuest; Micromedex (Thomson Reuters; Embase. Once the literature review was completed, the authors identified the main diseases with tomographic repercussions and proposed the present system to evaluate cranial computed tomography images. An easy-to-memorize ABC system will facilitate the decision making in emergency settings, as it covers the main diseases encountered by intensivists and emergency physicians, and provides a sequential guidance about anatomical structures to be investigated as well as their respective alterations.
abc: An extensible AspectJ compiler
Avgustinov, Pavel; Christensen, Aske Simon; Hendren, Laurie;
checking and code generation, as well as data flow and control flow analyses. The AspectBench Compiler (abc) is an implementation of such a workbench. The base version of abc implements the full AspectJ language. Its frontend is built, using the Polyglot framework, as a modular extension of the Java...... language. The use of Polyglot gives flexibility of syntax and type checking. The backend is built using the Soot framework, to give modular code generation and analyses. In this paper, we outline the design of abc, focusing mostly on how the design supports extensibility. We then provide a general overview...
Performance Optimization of Benchmark Functions Using VTS-ABC Algorithm
Twinkle Gupta
Full Text Available A new variant based on tournament selection called VTS-ABC algorithm is provided in this paper. Its performance is compared with standard ABC algorithm with different size of data on several Benchmark functions and results show that VTS-ABC provides better quality of solution than original ABC algorithm in every case.
ABC of childhood memories [artists' book
Wood, Philippa; MacLellan, Tamar
The limited edition artists' book by Philippa Wood and Tamar MacLellan – ABC of Childhood Memories was a collaborative project that explored the 1960s/70s childhood memories of each artist through text based narrative and image.
The abc-conjecture for Algebraic Numbers
Jerzy BROWKIN
The abc-conjecture for the ring of integers states that, for every ε> 0 and every triple of relatively prime nonzero integers (a, b, c) satisfying a + b = c, we have max(|a|, |b|, |c|) ≤ rad(abc)1+ε with a finite number of exceptions. Here the radical rad(m) is the product of all distinct prime factors of m.In the present paper we propose an abc-conjecture for the field of all algebraic numbers. It is based on the definition of the radical (in Section 1) and of the height (in Section 2) of an algebraic number.From this abc-conjecture we deduce some versions of Fermat's last theorem for the field of all algebraic numbers, and we discuss from this point of view known results on solutions of Fermat's equation in fields of small degrees over Q.
An ABC analysis for power generation project
Batool Hasani
Full Text Available One of the primary concerns on performance measurement is to know how much a particular project cost. However, using traditional method on project-based products often leads to inappropriate results. In this paper, we re-examine this issue by comparing the cost of a power station construction project using ABC versus traditional method. The results of survey show that ABC method is capable of providing better estimates for overhead costs compared with traditional method. In other words, ABC method helps reduce some of the unnecessary overhead cost items and increase on some other cost components. This helps increase the relative efficiency of the system by reducing total cost of project.
The ABC-paradox: is Time Driven ABC relevant for small and Medium sized enterprises (SME)?
Fladkjær, Henrik Find; Jensen, Erling
Several articles suggest that Activity Based Costing (ABC) has failed to succeed in practical use. It is even argued that we have an ABC-paradox. Activity Based Costing has won theoretically in nu-merous articles in journals, through books, being included in all major Business Accounting text-books...... manufacturing company we will analyse whether it is possible to create a satisfactory decision making foundation using a TDABC as a less complex cost model in the company. We have analysed our way to the conclusion that compared to ABC, the TDABC model provides the management with a number of pragmatic...
A note on ABC implementation: An evaluation case.
Nur Naha Abu Mansor
Whilst featuring prominently in management accounting research for at least the last decade, activity-based costing (ABC) may have reached a plateau in term of implementation and success. This paper reports the results of a survey of activity-based costing (ABC) in a telecommunication organization. The study considers ABC information and systems being used in various parts of division of the company. It reports on success measures adapted from the Foster and Swenson (1997) survey of ABC imple...
Approximate maximum likelihood estimation using data-cloning ABC
Picchini, Umberto; Anderson, Rachele
A maximum likelihood methodology for a general class of models is presented, using an approximate Bayesian computation (ABC) approach. The typical target of ABC methods are models with intractable likelihoods, and we combine an ABC-MCMC sampler with so-called "data cloning" for maximum likelihood estimation. Accuracy of ABC methods relies on the use of a small threshold value for comparing simulations from the model and observed data. The proposed methodology shows how to use large threshold ...
Christian Schreger
Full Text Available Das WeltABC ist eine Einladung zur Reise durch Sprache(n und damit verknüpften Bildern. Es ist eine Sammlung scheinbar klarer Begriffe, deren Ausgangspunkt die Sprache Deutsch ist. Diese Begriffe werden mit weiteren Begriffen assoziiert und durch Fotos illustriert.
New Broom To Sweep Clean At ABC
The Agricultural Bank of China (ABC) has a new president. The last non- publicly traded state-owned lender in China announced on July 6 that Xiang Junbo, former Vice Governor of the People's Bank of China, or the central bank, had beenappointed to take o
An Electrically Tight In Vitro Blood-Brain Barrier Model Displays Net Brain-to-Blood Efflux of Substrates for the ABC Transporters, P-gp, Bcrp and Mrp-1
Helms, Hans Christian; Hersom, Maria; Kuhlmann, Louise Borella;
Efflux transporters of the ATP-binding cassette superfamily including breast cancer resistance protein (Bcrp/Abcg2), P-glycoprotein (P-gp/Abcb1) and multidrug resistance-associated proteins (Mrp's/Abcc's) are expressed in the blood-brain barrier (BBB). The aim of this study was to investigate if a......143, zosuquidar, reversan and MK 571 alone or in combinations. Digoxin was mainly transported via P-gp, estrone-3-sulphate via Bcrp and Mrp's and etoposide via P-gp and Mrp's. The expression of P-gp, Bcrp and Mrp-1 was confirmed using immunocytochemistry. The findings indicate that P-gp, Bcrp and at...... least one isoform of Mrp are functionally expressed in our bovine/rat co-culture model and that the model is suitable for investigations of small molecule transport....
A note on ABC implementation: An evaluation case.
Nur Naha Abu Mansor
Full Text Available Whilst featuring prominently in management accounting research for at least the last decade, activity-based costing (ABC may have reached a plateau in term of implementation and success. This paper reports the results of a survey of activity-based costing (ABC in a telecommunication organization. The study considers ABC information and systems being used in various parts of division of the company. It reports on success measures adapted from the Foster and Swenson (1997 survey of ABC implementation.The Survey data was collected through a questionnaire to users of ABC sent through the company's e-mail system. 243 questionnaires were sent out for the 16 different ABC systems developed, 173 usable questionnaires were returned (a response rate of 71%. The respondents were selected based on their experience in using the various ABC systems irrespective of the divisions they operated in. They were mainly senior executives and executive level employees.The study is reported in four parts. Firstly, it reports on the usage of ABC information as compared to the traditional costing systems. It was found that budgeting, improving opportunities and aiding in product management decisions were highly scored as the main usage of ABC/M implementation. It states that ABC/M helped change in company's strategic focus, pricing strategy and changes in operations. Interestingly, it was found that ABC implementation provided almost no financial improvements, as perceived by respondents. Finally, the overall evaluation of the ABC systems is perceived by the users of the various ABC systems was to be mostly unsuccessful. A comparison of the survey results is made with the Foster and Swenson (1997 survey. The work is hoped to make a contribution to studying ABC implementation success in various settings.
The ABC exporter MsbA probed by solid state NMR – challenges and opportunities.
Kaur, Hundeep; Lakatos, Andrea; Spadaccini, Roberta; Vogel, Ramona; Hoffmann, Christian; Becker-Baldus, Johanna; Ouari, Olivier; Tordo, Paul; Mchaourab, Hassane; Glaubitz, Clemens
ATP binding cassette (ABC) transporters form a superfamily of integral membrane proteins involved in translocation of substrates across the membrane driven by ATP hydrolysis. Despite available crystal structures and extensive biochemical data, many open questions regarding their transport mechanisms remain. Therefore, there is a need to explore spectroscopic techniques such as solid state NMR in order to bridge the gap between structural and mechanistic data. In this study, we investigate the feasibility of using Escherichia coli MsbA as a model ABC transporter for solid state NMR studies. We show that optimised solubilisation and reconstitution procedures enable preparing stable and homogenous protein samples. Depending on the duration of solubilisation, MsbA can be obtained in either an apo- or in a native lipid A bound form. Building onto these optimisations, the first promising MAS-NMR spectra with narrow lines have been recorded. However, further sensitivity improvements are required so that complex NMR experiments can be recorded within a reasonable amount of time. We therefore demonstrate the usability of paramagnetic doping for rapid data acquisition and explore dynamic nuclear polarisation as a method for general signal enhancement. Our results demonstrate that solid state NMR provides an opportunity to address important biological questions related to complex mechanisms of ABC transporters. PMID:25849794
Nanostructured assemblies from amphiphilic ABC multiblock polymers
Hillmyer, Marc A.
Amphiphilic AB diblock copolymers containing a water compatible segment can self-assemble in aqueous media to give supramolecular structures that include simple spherical micelles and macromolecular vesicles termed polymersomes. Amphiphilic ABA triblocks with hydrophobic end blocks can adopt analogous structures but can also form gels at high polymer concentrations. The structural and chemical diversity demonstrated in block copolymer micelles and gels makes them attractive for applications ranging from drug delivery to personal care products to nanoreactors. The inclusion of a third block in amphiphilic ABC triblock systems can lead to a much wider array of self-assembled structures that depend not only on composition but also on block sequence, architecture and incompatibility considerations. I will present our recent efforts on tuning micelle and gel structure and behavior using controlled architecture ABC triblocks. The combination of diverse polymer segments into a single macromolecule is a powerful method for development of self-assembled structures with both new form and new function.
Evaristus Didik Madyatmadja
Full Text Available The purpose of this paper is to analyze the current system to find out problems faced by the company and propose alternative solutions and generate information needed by management by designing a data warehouse according to the information needs of PT ABC. This research implements analysis and design of data warehouse by Ralph Kimball and Ross cited by Connolly and Begg, known as Nine-Step Methodology. The result obtained is a data warehouse application that may present a multidimensional historical data that can assist the management in decisions. Designing data warehouse at PT ABC makes concise the enterprise data and can be viewed from several dimensions. It helps users analyze data for strategic decision quickly and accurately.
Harpunsoiton ABC : harpunsoiton alkeiskirjan luominen lapselle
Purhonen, Tiia
Tässä opinnäytetyössä kerron tekeillä olevan projektini Harpunsoiton ABC:n luomisen taustoista ja vaiheista. Projektin tavoitteena on valmistaa lapsille suunnattu harpunsoiton alkeiskirja. Opinnäyteyössäni etenen harpunsoiton harrastamisen historiasta edelleen nykytilanteeseen Suomessa ja esittelen modernin harpun ominaisuuksia ja soittotekniikkaa. Vertailen nykyistä harpun opetusmateriaalin kirjoa muiden soittimien oppikirjojen laajaan tarjontaan etsien hyviä pedagogisia ideoita. Ope...
ABC of physics a very brief guide
Okun, Lev Borisovich
This little book concentrates on the foundations of modern physics (its "ABC's") and its most fundamental constants: c - the velocity of light and ? - the quantum of action. First of all, the book is addressed to professional physicists, but in order to achieve maximal concentration and clarity it uses the simplest (high school) mathematics. As a result many pages of the book will be useful to college students and may appeal to a more general audience.
ATP and AMP Mutually Influence Their Interaction with the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) at Separate Binding Sites*
Randak, Christoph O.; Dong, Qian; Ver Heul, Amanda R.; Elcock, Adrian H.; Welsh, Michael J.
Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel in the ATP-binding cassette (ABC) transporter protein family. In the presence of ATP and physiologically relevant concentrations of AMP, CFTR exhibits adenylate kinase activity (ATP + AMP ⇆ 2 ADP). Previous studies suggested that the interaction of nucleotide triphosphate with CFTR at ATP-binding site 2 is required for this activity. Two other ABC proteins, Rad50 and a structural maintenance of chromosome protein, ...
Genome-wide identification and characterization of ATP-binding cassette transporters in the silkworm, Bombyx mori
Liu, Shumin; Zhou, Shun; Tian, Ling; Guo, Enen; Luan, Yunxia; Zhang, Jianzhen; Li, Sheng
Background The ATP-binding cassette (ABC) transporter superfamily is the largest transporter gene family responsible for transporting specific molecules across lipid membranes in all living organisms. In insects, ABC transporters not only have important functions in molecule transport, but also play roles in insecticide resistance, metabolism and development. Results From the genome of the silkworm, Bombyx mori, we have identified 51 putative ABC genes which are classified into eight subfamil...
Caracterización y análisis del coste de mejora de la calidad de servicio en transporte urbano en autobús, basado en la metodología ABC (activity based costing)
García Pastor, Antonio
El estudio de la calidad de servicio en transporte público ha tenido distintos enfoques, tanto en la investigación como en sus aplicaciones prácticas, tales como el desarrollo del método SERVQUAL, los proyectos QUATTRO y EQUIP de la Comisión Europea, el Transit Capacity and Quality of Service Manual y finalmente el estándar EN 13816, siendo la consideración principal la calidad desde el punto de vista del usuario, es decir, la calidad percibida, cuyo objetivo en la práctica tra...
Phase behavior of model ABC triblock copolymers
Chatterjee, Joon
The phase behavior of poly(isoprene-b-styrene- b-ethylene oxide) (ISO), a model ABC triblock copolymer has been studied. This class of materials exhibit self-assembly, forming a large array of ordered morphologies at length scales of 5-100 nm. The formation of stable three-dimensionally continuous network morphologies is of special interest in this study. Since these nanostructures considerably impact the material properties, fundamental knowledge for designing ABC systems have high technological importance for realizing applications in the areas of nanofabrication, nanoporous media, separation membranes, drug delivery and high surface area catalysts. A comprehensive framework was developed to describe the phase behavior of the ISO triblock copolymers at weak to intermediate segregation strengths spanning a wide range of composition. Phases were characterized through a combination of characterization techniques, including small angle x-ray scattering, dynamic mechanical spectroscopy, transmission electron microscopy, and birefringence measurements. Combined with previous investigations on ISO, six different stable ordered state symmetries have been identified: lamellae (LAM), Fddd orthorhombic network (O70), double gyroid (Q230), alternating gyroid (Q214), hexagonal (HEX), and body-centered cubic (BCC). The phase map was found to be somewhat asymmetric around the fI = fO isopleth. This work provides a guide for theoretical studies and gives insight into the intricate effects of various parameters on the self-assembly of ABC triblock copolymers. Experimental SAXS data evaluated with a simple scattering intensity model show that local mixing varies continuously across the phase map between states of two- and three-domain segregation. Strategies of blending homopolymers with ISO triblock copolymer were employed for studying the swelling properties of a lamellar state. Results demonstrate that lamellar domains swell or shrink depending upon the type of homopolymer that
Structural basis for allosteric cross-talk between the asymmetric nucleotide binding sites of a heterodimeric ABC exporter.
Hohl, Michael; Hürlimann, Lea M; Böhm, Simon; Schöppe, Jendrik; Grütter, Markus G; Bordignon, Enrica; Seeger, Markus A
ATP binding cassette (ABC) transporters mediate vital transport processes in every living cell. ATP hydrolysis, which fuels transport, displays positive cooperativity in numerous ABC transporters. In particular, heterodimeric ABC exporters exhibit pronounced allosteric coupling between a catalytically impaired degenerate site, where nucleotides bind tightly, and a consensus site, at which ATP is hydrolyzed in every transport cycle. Whereas the functional phenomenon of cooperativity is well described, its structural basis remains poorly understood. Here, we present the apo structure of the heterodimeric ABC exporter TM287/288 and compare it to the previously solved structure with adenosine 5'-(β,γ-imido)triphosphate (AMP-PNP) bound at the degenerate site. In contrast to other ABC exporter structures, the nucleotide binding domains (NBDs) of TM287/288 remain in molecular contact even in the absence of nucleotides, and the arrangement of the transmembrane domains (TMDs) is not influenced by AMP-PNP binding, a notion confirmed by double electron-electron resonance (DEER) measurements. Nucleotide binding at the degenerate site results in structural rearrangements, which are transmitted to the consensus site via two D-loops located at the NBD interface. These loops owe their name from a highly conserved aspartate and are directly connected to the catalytically important Walker B motif. The D-loop at the degenerate site ties the NBDs together even in the absence of nucleotides and substitution of its aspartate by alanine is well-tolerated. By contrast, the D-loop of the consensus site is flexible and the aspartate to alanine mutation and conformational restriction by cross-linking strongly reduces ATP hydrolysis and substrate transport. PMID:25030449
LSSVM-ABC Algorithm for Stock Price prediction
Hegazy, Osman; Soliman, Omar S.; Salam, Mustafa Abdul
In this paper, Artificial Bee Colony (ABC) algorithm which inspired from the behavior of honey bees swarm is presented. ABC is a stochastic population-based evolutionary algorithm for problem solving. ABC algorithm, which is considered one of the most recently swarm intelligent techniques, is proposed to optimize least square support vector machine (LSSVM) to predict the daily stock prices. The proposed model is based on the study of stocks historical data, technical indicators and optimizing...
Television Viewing and ABC Program Policy: An Econometric Study
Glenn Withers
There has been a long-standing debate over whether the ABC should engage in programming that is directly competitive with commercial television stations. This study uses an econometric model of television viewing to examine determinants of television set ownership and use, of ABC viewing levels and of diversity in programming. It is established that complementary not competitive programming most enhances ABC viewing levels, though production of greater diversity of television programming may ...
Biliary cholesterol secretion: More than a simple ABC
Arne Dikkers, Uwe JF Tietge
Full Text Available Biliary cholesterol secretion is a process important for 2 major disease complexes, atherosclerotic cardiovascular disease and cholesterol gallstone disease. With respect to cardiovascular disease, biliary cholesterol secretion is regarded as the final step for the elimination of cholesterol originating from cholesterol-laden macrophage foam cells in the vessel wall in a pathway named reverse cholesterol transport. On the other hand, cholesterol hypersecretion into the bile is considered the main pathophysiological determinant of cholesterol gallstone formation. This review summarizes current knowledge on the origins of cholesterol secreted into the bile as well as the relevant processes and transporters involved. Next to the established ATP-binding cassette (ABC transporters mediating the biliary secretion of bile acids (ABCB11, phospholipids (ABCB4 and cholesterol (ABCG5/G8, special attention is given to emerging proteins that modulate or mediate biliary cholesterol secretion. In this regard, the potential impact of the phosphatidylserine flippase ATPase class I type 8B member 1, the Niemann Pick C1-like protein 1 that mediates cholesterol absorption and the high density lipoprotein cholesterol uptake receptor, scavenger receptor class B type I, is discussed.
OSTOTOIMINNAN TEHOSTAMINEN : Case ABC Kokkolan ravintola
Huldén, Elin
Tämän toiminnallisen opinnäytetyön tarkoituksena oli kehittää ravintolan tilaus-toimitusrytmiä, huomioiden riviteho, logistiikka, ekologisuus ja varaston hallinta. Työn toimeksiantaja oli Keskipohjanmaan Osuuskauppa KPO, ja tutkimus kohdistui ABC Kokkola liikennemyymälän ravintolaan. Teoriaosa koostuu työn keskeisempien käsitteiden määrittelystä, kuten tilaus-toimitusketju, riviteho, varastonhallinta ja varastonkierto. Teoriaosuus sisältää myös toimeksiantajan esittelyn sekä tietoa toimin...
Genome-wide identification and characterization of ATP-binding cassette transporters in the silkworm,
Zhang Jianzhen; Luan Yunxia; Guo Enen; Tian Ling; Zhou Shun; Liu Shumin; Li Sheng
Abstract Background The ATP-binding cassette (ABC) transporter superfamily is the largest transporter gene family responsible for transporting specific molecules across lipid membranes in all living organisms. In insects, ABC transporters not only have important functions in molecule transport, but also play roles in insecticide resistance, metabolism and development. Results From the genome of the silkworm, Bombyx mori, we have identified 51 putative ABC genes which are classified into eight...
Dashboard auditing of ABC (Activity-Based Costing). Theoretical approaches
Căpuşneanu, Sorinel/I
This article aims to define the dashboard auditing according to the specifics of Activity-Based Costing method (ABC). It describes the main objectives of dashboard auditing, the criteria that a dashboard auditor should meet and the step-by-step stages of the entire dashboard auditing process of an enterprise from steel industry according to the Activity-Based Costing method (ABC).
Dashboard Auditing of Activity-Based Costing (ABC)
Sorinel Capusneanu
This article aims to define the dashboard auditing according to the specifics of Activity-Based Costing method (ABC). It describes the main objectives of dashboard auditing, the criteria that a dashboard auditor should meet and the step-by-step stages of the entire dashboard auditing process according to the Activity-Based Costing method (ABC).
Dashboard Auditing of Activity-Based Costing (ABC
Sorinel Capusneanu
Full Text Available This article aims to define the dashboard auditing according to the specifics of Activity-Based Costing method (ABC. It describes the main objectives of dashboard auditing, the criteria that a dashboard auditor should meet and the step-by-step stages of the entire dashboard auditing process according to the Activity-Based Costing method (ABC.
Sustained Delivery of Chondroitinase ABC from Hydrogel System
Filippo Rossi
Full Text Available In the injured spinal cord, chondroitin sulfate proteoglycans (CSPGs are the principal responsible of axon growth inhibition and they contribute to regenerative failure, promoting glial scar formation. Chondroitinase ABC (chABC is known for being able to digest proteoglycans, thus degrading glial scar and favoring axonal regrowth. However, its classic administration is invasive, infection-prone and clinically problematic. An agarose-carbomer (AC1 hydrogel, already used in SCI repair strategies, was here investigated as a delivery system capable of an effective chABC administration: the material ability to include chABC within its pores and the possibility to be injected into the target tissue were firstly proved. Subsequently, release kinetic and the maintenance of enzymatic activity were positively assessed: AC1 hydrogel was thus confirmed to be a feasible tool for chABC delivery and a promising device for spinal cord injury topic repair strategies.
The Role of the Actin Cytoskeleton and Lipid Rafts in the Localization and Function of the ABCC1 Transporter
Jan Willem Kok
Full Text Available ATP-binding cassette (ABC transporters are known to be important factors in multidrug resistance of tumor cells. Lipid rafts have been implicated in their localization in the plasma membrane, where they function as drug efflux pumps. This specific localization in rafts may support the activity of ABC/Abc transporters. This raises questions regarding the nature and composition of the lipid rafts that harbor ABC/Abc transporters and the dependence of ABC/Abc transporters—concerning their localization and activity—on lipid raft constituents. Here we review our work of the past 10 years aimed at evaluating whether ABC/Abc transporters are dependent on a particular membrane environment for their function. What is the nature of this membrane environment and which of the lipid raft constituents are important for this dependency? It turns out that cortical actin is of major importance for stabilizing the localization and function of the ABC/Abc transporter, provided it is localized in an actin-dependent subtype of lipid rafts, as is the case for human ABCC1/multidrug resistance-related protein 1 (MRP1 and rodent Abcc1/Mrp1 but not human ABCB1/P-glycoprotein (PGP. On the other hand, sphingolipids do not appear to be modulators of ABCC1/MRP1 (or Abcc1/Mrp1, even though they are coregulated during drug resistance development.
Women: the ABC of food security.
Arcellana, N P
While the 1996 World Food Summit Plan of Action was being approved, a companion NGO (nongovernmental organization) Forum provided opportunities for rural women from 29 countries to relay their perspectives and recommendations. The Rural Women's Workshop was organized by four NGOs: Isis International-Manila, La Via Campesina, the People-Centred Development Forum, and the Women's Food and Agriculture Working Group. Isis International-Manila seeks to create spaces, facilitate processes, and disseminate information for rural women to voice concerns, network, and plan responses. The La Via Campesina network operates in Latin American and the Caribbean where it applies a strong gender perspective to all of its activities. Ultimate progress on the World Food Summit Plan of Action can be evaluated using the ABCs of food security: does the program or policy assure 1) access for women to the total means of production; 2) benefits for women; and 3) community-based resource management and sustainable agriculture. PMID:12321562
ABC transporter genes and risk of type 2 diabetes
Schou, Jesper; Tybjærg-Hansen, Anne; Møller, Holger J; Nordestgaard, Børge; Frikke-Schmidt, Ruth
risk of type 2 diabetes in the general population is unknown. RESEARCH DESIGN AND METHODS: We tested whether genetic variation in the promoter and coding regions of ABCA1 and ABCG1 predicted risk of type 2 diabetes in the general population. Twenty-seven variants, identified by previous resequencing of...... of the variants examined, ABCG1 g.-530A>G, predicted a decreased risk of type 2 diabetes in the CCHS (P for trend = 0.05). Furthermore, when validated in the CGPS or in the CCHS and CGPS combined (n = 40,600), neither the two loss-of-function mutations (ABCA1 N1800H, ABCG1 g.-376C>T) nor ABCG1 g.-530......A>G were associated with type 2 diabetes (P values >0.57 and >0.30, respectively). CONCLUSIONS: Genetic variations in ABCA1 and ABCG1 were not associated with increased risk of type 2 diabetes in the general population. These data were obtained in general population samples harboring the largest...
abc: An Extensible AspectJ Compiler
Avgustinov, Pavel; Christensen, Aske Simon; Hendren, Laurie J.;
checking and code generation, as well as data flow and control flow analyses. The AspectBench Compiler (abc) is an implementation of such a workbench. The base version of abc implements the full AspectJ language. Its front end is built using the Polyglot framework, as a modular extension of the Java...... language. The use of Polyglot gives flexibility of syntax and type checking. The back end is built using the Soot framework, to give modular code generation and analyses. In this paper, we outline the design of abc, focusing mostly on how the design supports extensibility. We then provide a general...
A New Activity-Based Cost (ABC) Mathematical Model
JIANG Shuo; SONG Lei
Along with the product price competition growing intensely, it is apparently important for reasonably distributing and counting cost. But, in sharing indirect cost, traditional cost accounting unveils the limitations increasingly, especially in authenticity of cost information. And the accounting theory circles and industry circles begin seeking one kind of new accurate cost calculation method, and the activity-based cost (ABC) method emerges as the times require. In this paper, we will build its mathematical model by the basic principle of ABC, and will improve its mathematical model further. We will establish its comparison mathematical model and make the ABC method go a step further to its practical application.
Enhanced form of solving real coded numerical optimization problem using ABC algorithm with linear crossover operator
Mrs. Shanana Gajala Qureshi; Mrs. Uzma Arshi Ansari
Artificial Bee Colony (ABC) algorithm is population-based swarm intelligence algorithm. There are many algorithms Present for solving numeric optimization problem.ABC is based on the intellectual behaviour of honey bee crowd. In this work, ABC algorithm is used with Genetic crossover machinist and tested on standard benchmark functions, and also result compared with the X-ABC algorithm with the advantage of fewer organize Parameters. Obtained results show that the performance of the ABC with ...
Redundancy Level Optimization in Modular Software System Models using ABC
Tarun Kumar Sharma
Full Text Available The performance of optimization algorithms is problem dependent and as per no free lunch theorem, there exists no such algorithm which can be efficiently applied to every type of problem(s. However, we can modify the algorithm/ technique in a manner such that it is able to deal with a maximum type of problems. In this study we have modified the structure of basic Artificial Bee Colony (ABC, a recently proposed metaheuristic algorithm based on the concept of swarm intelligence to optimize the models of software reliability. The modified variant of ABC is termed as balanced ABC (B-ABC. The simulated results show the efficiency and capability of the variant to solve such type of the problems.
Yang-Mills Theory and the ABC Conjecture
He, Yang-Hui; Probst, Malte; Read, James
We establish a precise correspondence between the ABC Conjecture and N=4 super-Yang-Mills theory. This is achieved by combining three ingredients: (i) Elkies' method of mapping ABC-triples to elliptic curves in his demonstration that ABC implies Mordell/Faltings; (ii) an explicit pair of elliptic curve and associated Belyi map given by Khadjavi-Scharaschkin; and (iii) the fact that the bipartite brane-tiling/dimer model for a gauge theory with toric moduli space is a particular dessin d'enfant in the sense of Grothendieck. We explore this correspondence for the highest quality ABC-triples as well as large samples of random triples. The Conjecture itself is mapped to a statement about the fundamental domain of the toroidal compactification of the string realization of N=4 SYM.
Multicompartment Micelles From π-Shaped ABC Block Copolymers
XIA Jun; ZHONG Chong-Li
Dissipative particle dynamics simulations were performed on the morphology and structure of multicompartment micelles formed from n-shaped ABC block copolymers in water. The influences of chain architectures were studied in a systematic way, and a rich variety of morphologies were observed, such as spherical, wormlike,X-shaped, Y-shaped, ribbon-like, layered rod-like, layered disk-like, as well as network morphologies. The simulations show that the distance between the two grafts plays an important role in control of the morphology. Since π-shaped ABC block copolymers can be reduced to linear ABC and star ABC block copolymers, they are good model copolymers for studying the self-assembly of complex block copolymers into micelles. The knowledge obtained in this work as well as the new morphologies identified provide useful information for future rational design and synthesis of novel multicompartment micelles.
The saci_2123 gene of the hyperthermoacidophile Sulfolobus acidocaldarius encodes an ATP-binding cassette multidrug transporter
Yang, Nuan; Driessen, Arnold J. M.
Multidrug resistance (MDR) transporters are capable of secreting structurally and functionally unrelated toxic compounds from the cell. Among this group are ATP-binding cassette (ABC) transporters. These membrane proteins are typically arranged as either hetero- or homo-dimers of ABC half-transporte
Product development in company ABC: Strategic analysis and recommendations
Tadaniewicz, Darius
ABC is a mature company, operating in the power electronics market, using the stage gate process to develop products. This analysis evaluates the company's development process including innovation and portfolio management. An examination of the market reveals that speed-to-market and commitment to innovation are critical success factors. Benchmarking shows how comparable companies have adapted the traditional stage gate process to incorporate more flexible practices. Analysis of ABC uncovers ...
Product Profitability Analysis Based on EVA and ABC
Chen Lin; Shuangyuan Wang; Zhilin Qiao
On the purpose of maximizing shareholders' value, the profitability analysis established on the basis oftraditional accounting earnings cannot meet the demands of providing accurate decision-making information forenterprises. Therefore, this paper implements the Activity Based Costing (ABC) and the Economic Value Added(EVA) into the traditional profitability analysis system, sets up an improved EVA-ABC based profitabilityanalysis system as well as its relative indexes, and applies it to the s...
The 'ABC' of examining foot radiographs.
Pearse, Eyiyemi O.; Klass, Benjamin; Bendall, Stephen P.
INTRODUCTION: We report a simple systematic method of assessing foot radiographs that improves diagnostic accuracy and can reduce the incidence of inappropriate management of serious forefoot and midfoot injuries, particularly the Lisfranc-type injury. STUDY GROUP AND METHODS: Five recently appointed senior house officers (SHOs), with no casualty or Orthopaedic experience prior to their appointment, were shown a set of 10 foot radiographs and told the history and examination findings recorded in the casualty notes of each patient within 6 weeks of taking up their posts. They were informed that the radiographs might or might not demonstrate an abnormality. They were asked to make a diagnosis and decide on a management plan. The test was repeated after they were taught the 'ABC' method of evaluating foot radiographs. RESULTS: Diagnostic accuracy improved after SHOs were taught a systematic method of assessing foot radiographs. The proportion of correct diagnoses increased from 0.64 to 0.78 and the probability of recognising Lisfranc injuries increased from 0 to 0.6. CONCLUSIONS: The use of this simple method of assessing foot radiographs can reduce the incidence of inappropriate management of serious foot injuries by casualty SHOs, in particular the Lisfranc type injury. PMID:16263015
Bacterial multidrug resistance mediated by a homologue of the human multidrug transporter P-glycoprotein
Konings, WN; Poelarends, GJ
Most ATP-binding cassette (ABC) multidrug transporters known to date are of eukaryotic origin, such as the P-glycoproteins (Pgps) and multidrug resistance-associated proteins (MRPs). Only one well-characterized ABC multidrug transporter, LmrA, is of bacterial origin. On the basis of its structural a
Metodologia ABC: implantação numa microempresa ABC methodology: implementation on a micro firm
Orlando Duran
Full Text Available Este trabalho relata a implantação da metodologia de custos baseados em atividades numa microempresa do ramo metalúrgico. A proposta pretende demonstrar a viabilidade de aplicar esta técnica em empresas sem importar seu tamanho, só realizando algumas adaptações que garantam baixo investimento e curto espaço de tempo para obter os resultados. Na parte final do trabalho se realiza uma análise dos resultados obtidos verificando-se o potencial da informação gerada pela metodologia e seu uso como ferramenta de gestão.This paper presents an implementation of the activity based costing (ABC methodology in a small firm. The approach presented is intended to demonstrate the feasibility of applying the ABC methodology at any sized firm, only through few adaptations for ensuring low investments fees and speed in obtaining results and information from the system. Discussion about the results obtained during the implementation case are presented and the potential of using the information generated from the system as a managing tool is commented.