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International Journal of Alzheimer's Disease
Volume 2011 (2011), Article ID 548380, 11 pages
Mechanisms of Amyloid-Beta Peptide Uptake by Neurons: The Role of Lipid Rafts and Lipid Raft-Associated Proteins
1Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, 6 Queen's Park Crescent West, Toronto, ON, Canada M5S 3H2
2Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada M5S 3H2
Received 15 October 2010; Accepted 29 November 2010
Academic Editor: Anne Eckert
Copyright © 2011 Aaron Y. Lai and JoAnne McLaurin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
A hallmark pathological feature of Alzheimer's disease (AD) is the accumulation of extracellular plaques composed of the amyloid-beta (Aβ) peptide. Thus, classically experiments were designed to examine Aβ toxicities within the central nervous system (CNS) from the extracellular space. However, a significant amount of evidence now suggests that intraneuronal accumulation of Aβ is neurotoxic and may play an important role in the disease progression of AD. One of the means by which neurons accumulate intracellular Aβ is through uptake of extracellular Aβ peptides, and this process may be a potential link between Aβ generation, synaptic dysfunction, and AD pathology. Recent studies have found that neuronal internalization of Aβ involves lipid rafts and various lipid raft-associated receptor proteins. Uptake mechanisms independent of lipid rafts have also been implicated. The aim of this paper is to summarize these findings and discuss their significance in the pathogenesis of AD.
1. Introduction
Alzheimer's disease (AD) is the most common form of dementia with a high prevalence rate among the aging population [1]. The clinical symptoms are characterized by loss of selective cognitive functions, particularly memory loss [1]. These traits are accompanied by neuropathological features observed in postmortem AD brains, including loss of neurons and synapses in cortical and subcortical regions, as well as extracellular plaques composed of aggregated amyloid-beta (Aβ) peptides and intracellular neurofibrillary tangles that contain hyperphosphorylated Tau protein [2]. Although the precise role of Aβ in AD etiology remains inconclusive, the current consensus is that it is a central player in the development of the disease. This hypothesis is supported by a variety of transgenic mouse lines that contain mutations in the Aβ processing machinery [3]. These mice display some of the neuropathologies and behavioral deficits similar to that observed in AD patients, providing a link between abnormal Aβ production and disease development [3]. Nevertheless, the cellular events that occur between production of the Aβ peptide and degeneration of a neuron remain inconclusive. Aβ is produced from its membrane-embedded precursor, amyloid precursor protein (APP), through sequential cleavage by enzyme complexes β- and γ-secretases [4]. Two distinct cleavage pathways exist. In the nonamyloidogenic pathway, APP is cleaved by α-secretase resulting in an 83-amino-acid C-terminal fragment that is further cleaved by the γ-secretase into a short p3 peptide [5]. In the amyloidogenic pathway, the cleavage occurs at 99 rather than 83 amino acids from the C-terminus and is mediated by the β-secretase [6]. This results in a 99-amino-acid peptide that contains an intact hydrophobic region termed the Aβ region [6]. Subsequent cleavage by γ-secretase releases this peptide region forming the Aβ peptide normally 40-amino-acids in length (Aβ40) [6]. An alternate cleavage by the γ-secretase results in a less abundant form of the peptide 42 residues in length (Aβ42) [7]. Aβ42 is more hydrophobic and has a greater tendency to aggregate into fibrils and plaques compared to Aβ40 [7]. Aβ42 is also the prevalent isoform found in the amyloid plaques of AD patients [8]. Several hypotheses have been proposed in regards to how Aβ production leads to neuronal degeneration and toxicity: Aβ monomers are known to aggregate into higher-molecular weight oligomers and fibrils [9]. The hydrophobicity of Aβ allows it to target neurons directly; extracellular Aβ aggregates can interact with neuronal membranes resulting in disruptions in bilayer permeability [10]. Aβ oligomers and fibrils also bind to several membrane proteins which may induce change or loss of protein function [11].
2. Sources of Intracellular Aβ
Despite evidence suggesting that Aβ exerts its effects extracellularly, reports have shown that Aβ in the intraneuronal compartment may play an important role. As early as the 1980s, researchers have observed that in AD patients, Aβ deposition inside the cells precedes its accumulation in the extracellular space [12, 13]. The findings in human subjects are corroborated by transgenic mouse models of AD, where intraneuronal Aβ is commonly observed. Various mouse models display Aβ deposits inside neurons well before the appearance of extracellular plaques [14–21]. In the triple transgenic (3xTg) AD mice, the level of intraneuronal Aβ is found to correlate with synaptic dysfunction and memory impairment [21, 22]. In spite of these observations, the concept that intraneuronal Aβ contributes to disease progression has not been ubiquitously accepted. One large-scale human study found contradicting evidence, such that the level of intraneuronal Aβ increases with age even in non-AD individuals [23], suggesting that Aβ inside neurons may not have a pathological role. This might be explained by the fact that some fixation and staining methods detect Aβ in the extracellular space more strongly than inside cells [24–26]. For example, studies have shown that exposure to formic acid, which is a commonly used step in Aβ staining, does not yield the strongest intracellular Aβ signal whereas antigen retrieval by heating enhances the signal [24, 25]. Bayer and Wirths [26] suggested that in transgenic mice studies, brains are normally fixed by cardiac perfusion in a short time frame, leading to more frequent observations of intraneuronal Aβ in mouse models than in human tissues that are exposed to extended periods of postmortem fixation.
Although the role of intraneuronal Aβ in disease development is controversial, there is no dispute regarding the presence of Aβ within neurons. The key question that follows is the origin of the accumulated Aβ inside neurons. Thus far it is unclear whether the accumulation originates from direct deposition of Aβ intracellularly or from uptake from the extracellular Aβ pool. In addition to the plasma membrane, APP is also found on membranes of mitochondria, the trans-Golgi network, endoplasmic reticulum (ER), endosomes, autophagosomes, and lysosomes [27]. β- and γ-secretases have been found in these subcellular compartments [27]; hence Aβ production occurs intracellularly as well. Endosomes in particular are hypothesized to be a major site of Aβ production due to their acidic pH and coexpression of both β- and γ-secretases [27]. Studies have shown that internalization of APP from the plasma membrane to endosomes can occur via endocytosis, and that blockade of this process reduces intracellular Aβ levels [28]. Coexpression of β- and γ-secretases is also found in the Golgi [27], suggesting that the secretory pathways are also potential sites of Aβ production. Intracellular trafficking of APP may act as a cellular mechanism that regulates the production of Aβ since some cellular compartments have optimal conditions for APP cleavage while others do not. Nonetheless, there is no question that a significant amount of APP is cleaved at the plasma membrane resulting in extracellular deposition of Aβ. One possible fate of deposited Aβ is re-entry into cells. Glial cells including astrocytes and microglia are the putative phagocytic cells in the CNS. Extracellular Aβ can be internalized by glial cells via phagocytosis as well as pinocytosis and endocytosis [29–31]. A significant portion of deposited Aβ is likely taken up by glia. Neurons, on the other hand, are not generally considered phagocytic cells. Nonetheless, reports have shown that Aβ uptake can occur in neurons contributing to the accumulation of intraneuronal Aβ [6, 26]. Due to their potential significance in AD etiology, the cellular mechanisms that mediate neuronal Aβ uptake have garnered increased attention in recent years. Current data suggest that the majority of Aβ uptake mechanisms in neurons involve membrane microdomains termed lipid rafts.
3. Lipid Metabolism, Lipid Rafts, and AD
Lipid rafts are mobile microdomains in plasma or organelle membranes that are rich in cholesterol and sphingolipids [32]. This specialized lipid composition distinct from the surrounding membrane phospholipids allows lipid rafts to associate with select groups of proteins [32]. Lipid raft-associated proteins have key roles in protein entry and trafficking as well as signal transduction [32]. The idea that lipid rafts may be associated with Aβ metabolism originated from cholesterol studies [32]. In AD patients, serum cholesterol levels correlated with Aβ load in the brain [33]. Individuals with high cholesterol levels during midlife are at a higher risk to develop AD later in life [34], whereas individuals treated with cholesterol lowering drugs have a lower prevalence of AD [35, 36]. Similar trends were observed in animal and cell culture models [32]. Notably, accumulation of intraneuronal Aβ was increased in transgenic AD mice fed with a high cholesterol diet [37, 38]. Despite evidence supporting a role for cholesterol in AD pathogenesis, clinical use of cholesterol-lowering statins to treat AD patients has not yielded consistent results [39]. Furthermore, postmortem analyses of AD brains showed that cholesterol levels in the hippocampus and the frontal cortex were not significantly different from that of age-matched controls [40, 41]. Although the precise role of cholesterol in AD is unclear, the discovery of β-secretase, γ-secretase, and APP at lipid rafts suggests that cholesterol is involved in APP processing and Aβ production [42–44]. Indeed, cholesterol depletion in cultured neurons decreases the production of Aβ [45]. Cholesterol depletion is a commonly used method to compromise lipid raft integrity and has been shown to dissociate γ-secretase from lipid rafts [44, 46]. Increased targeting of β-secretase to lipid rafts promoted its cleavage activity of APP [47]. Studies have also found that unlike APP cleavage, which occurs mostly at lipid rafts, non-APP substrates of the γ-secretase were cleaved at non-lipid raft domains [44]. Lipid rafts may thus serve as a platform for secretases to differentiate APP processing from other secretase-dependent cellular processes.
4. Aβ Binding, Aggregation, and Internalization at Lipid Rafts
In addition to processing of APP, lipid rafts have been proposed as a site for binding of extracellular Aβ and a niche for Aβ aggregation [11, 48]. Exogenously applied oligomeric Aβ has been shown to concentrate at lipid rafts of cultured neurons [49]. Lipid rafts isolated from AD mice are also concentrated with soluble nonfibrillar Aβ [50]. Sphingolipid derivatives such as sphingomyelin and gangliosides can readily bind both soluble and fibrillar Aβ and are thought to be the major Aβ-recruiting component in lipid rafts [51–54]. Cholesterol has also been shown to interact with soluble and fibrillar Aβ [55]. Gangliosides, in particular monosialotetrahexosylganglioside (GM1), is known to form an "Aβ-seed" by complexing with soluble Aβ [51, 52]. GM1-bound Aβ (GM1/Aβ) has a different conformation than that of soluble Aβ and seeds the formation of Aβ aggregates [51, 52]. Binding of Aβ to lipid rafts has been shown to promote its oligomerization and subsequently fibril formation, possibly via the seeding and aggregation-promoting effect of GM1/Aβ [56, 57]. Disruption of lipid rafts in cultured pheochromocytoma cells was able to protect them against toxicity induced by Aβ oligomers [58, 59]. The interaction of Aβ with lipid rafts may induce toxicity via several mechanisms: Aβ aggregation at lipid rafts can induce membrane perturbations by oxidative damage [60, 61]. Alternatively, interaction of Aβ oligomers with GM1 decreases membrane fluidity and in turn stimulates APP processing, resulting in a vicious cycle of Aβ overproduction [62]. It has also been suggested that rather than aggregating on the cell surface, a portion of the Aβ binding to lipid rafts is internalized [63]. One of the earlier studies examining Aβ internalization observed that in human fibroblast cells, Aβ accumulated intracellularly were in a high-molecular weight oligomeric state [64]. A later study using human neuroblastoma cells showed that not all of the applied exogenous Aβ oligomers were internalized; the oligomers bound to the membrane formed aggregates larger than the internalized oligomers [63]. These findings suggest that Aβ uptake may precede its aggregation at the membrane, and that surface aggregation of Aβ takes place as a result of saturation of the uptake pathway. The authors also demonstrated that oligomeric Aβ was internalized more efficiently than fibrillar Aβ [63]. Saavedra et al. [65] in a study using cervical sympathetic neurons found that internalized Aβ oligomers colocalized with cholera toxin subunit B (CTxB), a lipid raft marker that specifically binds to GM1, suggesting that Aβ internalization occurs at lipid rafts, possibly via GM1 binding. The authors further showed that reduction of cellular cholesterol and sphingolipid levels significantly decreased Aβ uptake [65]. A recent study by Singh et al. [66] using mouse neuroblastomas also found colocalization of internalized Aβ with CTxB. The authors pharmacologically inhibited lipid raft-dependent endocytosis which resulted in decreased uptake of soluble Aβ [66]. Thus far it is unclear whether the lipid components or the associated receptor proteins are responsible for initiating Aβ uptake at lipid rafts. Aβ, in addition to lipids, can bind to a wide range of membrane proteins [11], which may act as carriers of Aβ upon endocytosis of the Aβ-receptor protein complex. The following section discusses the various routes of cellular entry for extracellular Aβ.
5. Mechanisms of Aβ Uptake
5.1. Glutamate Receptors
One of the earliest pathological features in AD that coincides with accumulation of intraneuronal Aβ is synaptic aberrations including changes in the shape and the protein composition of synapses as well as an overall decrease in abundance. Application of exogenous soluble Aβ to hippocampal slices leads to Aβ accumulation in CA1 neurons coupled with decreased expression of the synaptic marker synaptophysin [67]. Extracellular Aβ may thus preferentially target synapses. There is a wide range of lipid raft-associated receptors localized at the synaptic membrane. One receptor that is highly expressed at synapses is the N-methyl-D-aspartic acid (NMDA) receptor for the neurotransmitter glutamate. NMDA receptors are associated with lipid rafts [68, 69]. Exposure of the NMDA receptor to Aβ oligomers is known to promote endocytosis of the receptor as well as other signaling events associated with NMDA receptor trafficking [28]. In hippocampal slices treated with soluble Aβ, cotreatment with an NMDA receptor antagonist prevented the neuronal accumulation of Aβ, suggesting that activation of the receptor by Aβ may trigger endocytosis of the Aβ-NMDA receptor complex [70]. However, whether Aβ actually binds to NMDA receptor is unclear. In a study examining the effects of Aβ oligomers on primary hippocampal neurons, Lacor et al. [71] noted that the binding sites of Aβ oligomers overlap with immunoreactivity of NMDA receptor 1 (NR1), a subunit of the NMDA receptor, and postsynaptic density-95 (PSD-95), an anchoring protein associated with the NMDA receptor. This would suggest physical associations between Aβ and the NMDA receptor. However, colocalization and co-precipitation of the two in an intracellular compartment have not been demonstrated. Some hypothesized that the NMDA receptor and its associated signaling cascades interact with Aβ via another Aβ-binding receptor protein. In the study by Bi et al. [70], cotreatment of antagonists against integrins with soluble Aβ nearly doubled the amount of internalized Aβ compared to Aβ treatment alone. As NMDA receptor antagonist yielded opposite trends, the authors hypothesize that membrane integrins and the NMDA receptor modulate Aβ uptake cooperatively [70]. Integrins are associated with lipid rafts as well [72]. Aβ is known to bind integrins directly [73], and in addition to regulating Aβ uptake, integrins also modulate the neurotoxic effects of soluble Aβ [70]. There is currently no data suggesting that integrins physically interact with the NMDA receptor despite evidence showing that integrin signaling modulates NMDA receptor activity and trafficking [74–76]. Therefore, it is possible that both receptors act as Aβ carriers but at the same time induce other signaling cascades independent of the uptake process.
Another glutamate receptor modulated by integrin signaling is the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor [76–78]. The AMPA and NMDA receptors are often co-expressed by the same glutamatergic synapses. Like NMDA receptors, AMPA receptors are closely associated with lipid rafts and GM1 in particular [68, 79–81]. However, AMPA receptor recycling to and from the synaptic surface is fast compared to that of NMDA receptors, suggesting that AMPA receptors may act as a more efficient carrier of Aβ than NMDA receptors [82]. In a study using primary hippocampal neurons, Zhao et al. [82] showed that AMPA receptor trafficking is regulated by Aβ oligomers. Antagonists against the AMPA receptor inhibited Aβ internalization as in the case with NMDA receptor antagonists [82]. The authors further demonstrated that the glutamate receptor 2/3 (GluR2/3) subunit of AMPA receptors co-immunoprecipitated with Aβ oligomers [82], implicating a role for AMPA receptors as an Aβ carrier. Several other research groups have also reported endocytosis of AMPA receptors induced by Aβ oligomers [83, 84], leading to the speculation that endogenous Aβ at physiological levels may have essential roles in the maintenance of synapses. A recent study demonstrated that in mice overexpressing APP, the density of dendritic spines is increased at a young age before accumulation of Aβ nullifies the effect at an older age [85]. Hence it is possible that APP at synaptic membranes promotes surface expression and stabilization of glutamate receptors, while cleavage of APP and synaptic release of Aβ would promote opposite effects. The uptake of Aβ by glutamate receptors may serve as a regulatory mechanism that prevents Aβ-induced synaptic depression.
5.2. Acetylcholine Receptors
Another neurotransmitter receptor implicated in the uptake of Aβ is the α7 nicotinic cholinergic receptor (α7nChR) for the neurotransmitter acetylcholine. The role of acetylcholine and its receptors have received continuous attention in the AD field due to the high susceptibility of cholinergic neurons to degenerate in AD pathology [86]. Several hypotheses have been formed to explain this regional transmitter-specific vulnerability. It has been proposed that cholinergic signaling modulates APP processing [86]. Conversely, Aβ can affect acetylcholine release from the presynaptic terminal as well as signaling of nicotinic receptors in the postsynaptic compartment [86]. The α7nChR in particular is known to bind soluble Aβ with high affinity [87, 88], leading to the speculation that Aβ may be internalized via complex formation with the α7nChR. Nagele et al. [89] investigated this possibility in a study examining both human AD tissues and human neuroblastoma cells. The authors found that immunoreactivity of α7nChR and Aβ is highly colocalized in neurons of the hippocampus, entorhinal cortex, and cerebellum [89]. They observed similar findings in vitro; in neuroblastoma cells transfected with α7nChR, soluble Aβ treatment induced large punctate staining of α7nChR which colocalized with Aβ immunoreactivity [89]. Untransfected cells exhibited slower internalization of Aβ and lower susceptibility to Aβ-induced toxicity, suggesting a role for α7nChR as an Aβ carrier [89]. Although subcellular colocalization of Aβ and α7nChR has not been reported, circumstantial evidence indicates that neurotoxic effects of intracellular Aβ are mediated at least partly by uptake via α7nChR independent of its agonist effects. For instance, binding of α7nChR by Aβ results in primarily neurotoxic effects, yet paradoxically, binding of the same receptor by other competing agonists promotes neuroprotection [90]. Another study showed similar paradoxical results where disruption of lipid rafts attenuated Aβ-mediated α7nChR signaling but not nicotine-mediated signaling [91]. An explanation for this paradox is that the toxic effects of Aβ on cholinergic synapses occur after internalization by cholinergic receptors, and that activation of the receptor upon Aβ binding at common agonist sites triggers other independent pathways. This explanation may also justify contradictory findings in animal studies, where transgenic AD mice deficient in α7nChR expression exhibited exacerbated AD pathology in one report [92] and ameliorated pathology in another [93].
5.3. Apolipoproteins
A group of proteins implicated in the trafficking of Aβ that are not localized to synaptic membranes are apolipoproteins. As implied by the nomenclature, the amphipathic nature of apolipoproteins enables them to bind and transport lipids within a water-soluble milieu. Some apolipoproteins act as soluble chaperones for hydrophobic peptides such as Aβ [94]. In nonfamilial AD, the ε4 allele of the gene encoding apolipoprotein E (apoE) is the most prevalent genetic risk factor [94]. Consequently, the potential link between apoE function and Aβ toxicity has been studied extensively. Transgenic AD mice deficient in apoE display reduced Aβ load, suggesting a role for apoE in promoting Aβ accumulation [95]. Isoform-specific properties of the apoE4 allele were also investigated: binding studies comparing different apoE isoforms showed that apoE2 and apoE3 bind soluble Aβ more efficiently than apoE4 that preferentially binds to an intermediate aggregate form of Aβ [96, 97]. An in vitro study on purified synaptosomes showed that soluble Aβ, but not fibrillar Aβ, complexes with apoE, and that formation of the apoE-Aβ complex is crucial in the capacity of apoE3 to promote Aβ internalization [98]. The authors observed the same trend in intact neurons of the dorsal root ganglia [98]. The capacity of apoE to promote uptake of soluble Aβ is isoform-dependent; in the case of apoE4, promotion of uptake requires proteolytic cleavage [99]. In tissues of AD patients, immunoreactivity of apoE strongly correlates with that of intracellular Aβ, suggesting that apoE is internalized with Aβ [100]. Whether Aβ enters neurons as a complex with apoE or as a chaperone-free entity is unclear. The receptor that mediates apoE-dependent internalization of Aβ is also undefined. Similar to Aβ, apoE does not appear to have a dedicated receptor but is known to bind several putative receptor proteins. In transgenic AD mice, apoE is found to accumulate in lipid rafts suggesting that the apoE-Aβ complex may target raft-associated receptor proteins [50]. Moreover, apoE has been observed to target neurotransmitter receptors such as α7nChR [90], leading to the hypothesis that uptake of Aβ by neurotransmitter receptors results from apoE-receptor binding rather than direct interaction between Aβ and the receptor. The surface receptors most often associated with apoE are the low-density lipoprotein receptor-related proteins (LRPs), a family of multiligand receptors known to have a high endocytosis rate [101]. LRP1 in particular has several known roles in AD. For instance, LRP1 binds to APP at the cell surface and subsequent endocytosis targets APP to the lysosome, modulating Aβ production [101]. The same endocytic mechanism is thought to mediate the uptake of Aβ. Gylys et al. [98] showed that addition of receptor-associated protein (RAP), an antagonist of LRP1, along with the apoE-Aβ complex significantly reduced internalization of soluble Aβ. A recent study in neuroblastoma and neuronal cell lines observed similar trends, such that RNA interference of LRP1 inhibited and overexpression of LRP1 stimulated soluble Aβ uptake [102]. In vivo experiments found that AD mice overexpressing LRP had increased intraneuronal accumulation of Aβ [103]. It has been suggested that LRP1 may bind soluble Aβ directly without chaperones. Binding assays, however, showed otherwise [104], and in an apoE-free environment, LRP inhibition did not alter Aβ uptake [65], suggesting that formation of the apoE-Aβ complex is required for internalization by LRP1. Notably, LRP1 associates with lipid rafts transiently such that it traffics between raft and nonraft membrane domains [105]. The motility of LRP1 may serve as a mechanism to regulate its availability to Aβ. The LRP antagonist receptor-associated protein (RAP), in addition to its LRP-modulating activities, has molecular properties similar to chaperone proteins like apoE. Kanekiyo and Bu [106] showed that RAP forms complexes with soluble Aβ much like apoE and similarly promotes Aβ uptake into neuroblastoma cells. They further demonstrated that uptake of soluble Aβ with RAP is independent of LRP1 [106], which is somewhat surprising as RAP is routinely used experimentally to inhibit LRP1 activity. The precise route of entry for RAP-Aβ complexes is thus unclear.
5.4. Other Aβ-Binding Proteins
The proteins implicated in Aβ uptake represent only a small percentage of soluble and membrane proteins that physically interact with Aβ. The list of Aβ-binding proteins is extensive (see [11] for a review). One notable receptor protein implicated in neuronal internalization of Aβ is the receptor for advanced glycation end products (RAGE). RAGE is a member of the immunoglobulin superfamily that interacts with several classes of ligands [107]. Complex formation between RAGE and soluble Aβ has been demonstrated [108]. Neuronal overexpression of RAGE in transgenic AD mice results in exacerbated AD pathology [109], suggesting that RAGE may promote intracellular Aβ accumulation. To demonstrate the role of RAGE in Aβ uptake, Takuma et al. [107] derived primary cortical neurons from RAGE-deficient mice, showing that neurons without RAGE expression internalized markedly less soluble Aβ compared to wild-type neurons. Interestingly, while internalization facilitated by most receptors appeared to localize to lysosomes, the authors showed by electron microscopy that Aβ internalized by RAGE accumulates in the mitochondria [107]. Accumulation of Aβ in the mitochondria is a well-documented occurrence (reviewed in [110]). Mitochondria are closely associated with the ER [111], hence it is possible that Aβ in the mitochondria originates from endosome-Golgi and Golgi-ER vesicular transport. However, since mitochondria are not classically associated with the endosomal pathways, it is proposed that mitochondrial Aβ derives from transport of cytosolic Aβ. Although mitochondria have been shown to import cytosolic Aβ via translocases [112], it is unclear how extracellular Aβ, which enters the cell by endocytosis of RAGE, translocates out of the endo-lysosomal compartments into the cytosol. Localization of internalized Aβ to the mitochondria may not be specific to RAGE endocytosis; therefore, future studies need to determine whether Aβ endocytosed through other receptor proteins also localize to mitochondria.
The serpin-enzyme complex receptor (SEC-R) is another less documented protein implicated in the uptake of Aβ [113]. It was originally identified in leukocytes as a receptor for antiprotease enzymes. Although SEC-R is also expressed in neurons [113], its role in neuronal cells and Aβ-associated processes is unknown. Boland et al. [113] showed that SEC-R binds to soluble Aβ and promotes uptake in pheochromocytoma cells. Whether SEC-R functions similarly in neurons has not been determined. A recent study reported that multiple epidermal growth factor-like domains 10 (MEGF10), a newly identified receptor involved in clearance of cell corpses, also modulates soluble Aβ uptake [66]. Although the authors show expression of MEGF10 in neurons of the hippocampus, it is unclear whether MEGF10 physically interacts with Aβ, and henceforth whether MEGF10 mediates Aβ uptake or merely modulates the process.
5.5. Endocytic Pathways of Aβ
A topic that has generated a significant amount of interest concerns the specific endocytic pathways involved in Aβ uptake. Endocytosis is a well-studied phenomenon in cell biology and to date several distinct pathways involving different protein machinery have been identified (for a review see [114]). The classical endocytic pathway involves invagination of the plasma membrane at the site of the receptor-cargo binding; the invaginated vesicle is then coated with adaptor proteins, which recruit guanosine triphosphatases (GTPases) that provide the necessary energy to facilitate cleavage of the vesicle from the cell membrane and delivery to endosomes or other subcellular compartments [114]. By far the most frequently reported process is dependent on clathrin and dynamins [114]. Clathrin is an adaptor protein that forms the primary component of the vesicle coating complex [114]. Dynamins are responsible for the membrane cleavage to release the invaginated vesicle from the plasma membrane [114]. Endocytosis at lipid rafts, however, is thought to proceed in a clathrin-independent manner (reviewed in [115]). Invaginations formed from lipid rafts, termed caveolae, are rich in cholesterol and sphingolipids and are morphologically distinct from clathrin-coated invaginations [115]. Caveolins are the major protein component of caveolae and are thought to cooperatively regulate lipid raft endocytosis with cholesterol and gangliosides [115]. It was originally thought that endocytosis at lipid rafts are caveolin- and dynamin-dependent. However, there is increasing evidence suggesting a caveolin-independent dynamin-dependent pathway as well as a flotillin-dependent dynamin-independent pathway [114]. The notion that lipid raft endocytosis does not involve clathrin has also been challenged as studies have observed clathrin-dependent endocytosis of lipid raft-associated proteins [116, 117].
Among receptor proteins that mediate Aβ uptake, LRP1 has been shown to endocytose Aβ via a clathrin-dependent process; neuroblastoma and neuronal cell lines deficient in clathrin internalized significantly less soluble Aβ as well as LRP1 [102]. Requirement for clathrin has also been shown in endocytosis of the NMDA and AMPA receptors for glutamate [118]. Not all routes of Aβ uptake, however, are clathrin-dependent. In the case of α7nChR, in Chinese hamster ovary cells transfected with α7nChR, endocytosis of the receptor occurs in the absence of clathrin, and in fact, dynamins as well [119]. This contradicts an earlier study in α7nChR-transfected human neuroblastomas that reported inhibition of α7nChR endocytosis along with decreased soluble Aβ internalization by treatment with phenylarsine oxide, an inhibitor of clathrin-coat formation [89]. It is possible that both pathways mediate α7nChR endocytosis and that the specific cell type can determine which pathway is dominant. Clathrin-independent internalization of Aβ has been reported in several different neuronal cell types. In mouse neuroblastoma cells, neither knockdown of clathrin nor inhibition of AP180, a clathrin-associated assembly protein, had an effect on internalization of oligomeric Aβ [120]. The authors reported that inhibition of dynamin and RhoA, a small GTPase, decreased the uptake of Aβ oligomers into the cell [120]. These data suggest that Aβ can be internalized through an IL-2 receptor-β-like endocytic pathway dependent on lipid rafts, dynamins, and RhoA [115]. In cervical sympathetic neurons, Saavedra et al. [65] also reported that uptake of Aβ oligomers is independent of clathrin. A role for dynamins is again implicated, as expression of dominant negative dynamin mutant decreased Aβ internalization [65]. The authors further demonstrate that the internalized Aβ oligomers colocalized with lipid rafts, but not caveolins [65]. This dynamin-/raft-dependent caveolin-independent pathway has also been demonstrated in MEGF10-mediated uptake of soluble Aβ [66] and is likely similar to the IL-2 receptor-like pathway [120]. Collectively these data show that in the absence of clathrin-associated receptors, neurons endocytose Aβ predominantly at lipid rafts via caveolin-independent mechanisms. Clathrin-dependent endocytosis of Aβ can occur, but it is uncertain whether it takes place at lipid rafts. Notably, internalization of Aβ oligomers in cervical sympathetic neurons preferentially occur in axons [65] while in primary hippocampal neurons and neuron-like cell lines described in other reports, the uptake appears to occur in dendritic synapses and cell bodies. These results suggest that endocytic mechanisms are varied not only in different types of neurons, but in different parts of the neuron.
Aside from endocytosis, an unconventional route of Aβ uptake was proposed by Kandimalla and colleagues [121]. By comparing Aβ uptake between primary hippocampal neurons and endothelial cells, the authors reported that while the latter requires endocytosis to internalize soluble Aβ, neurons can take up soluble Aβ by passive diffusion [121]. Neuronal uptake of soluble Aβ was unaffected by low temperature or low glucose, suggesting that neuronal internalization of Aβ is not mediated by energy-dependent processes including endocytosis [121]. There are biophysical data supporting this conclusion, such that both Aβ40 and Aβ42 intercalate into phospholipid bilayers [122]. It is not unreasonable to propose that endocytosis and passive diffusion of Aβ can coexist in the same neuron. Further investigation is needed to reconcile the seemingly contradicting results in regards to studies showing endocytosis-dependent Aβ uptake.
6. Future Directions and Conclusions
With the recent wealth of novel findings, our understanding of neuronal Aβ uptake has improved since the original discovery of intraneuronal Aβ in AD brains. Cumulatively, the current data implicate several distinct pathways of entry for extracellular Aβ (Table 1). Lipid raft-dependent endocytosis is the predominant Aβ uptake mechanism although lipid raft-independent endocytosis and nonendocytic pathways also exist. Lipid components such as cholesterol and sphingolipids have a role in modulating Aβ endocytosis as well as recruiting Aβ to the lipid raft. Questions remain as to whether lipids can act as carriers of Aβ uptake independent of lipoprotein chaperones and receptor proteins. It may be the case that lipid components and raft-associated receptors synergistically carry Aβ into the cell. Further investigations are needed to address these speculations. There is also little data on the long-term effects of internalized Aβ, which is found not only in endocytic pathways but also in other compartments including the cytosol. In vitro studies in general found that internalized Aβ cause lysosomal leakage and neurotoxicity, but whether the same occurs in vivo in the presence of physiological buffers is yet to be determined. In fact, most of the mechanisms of Aβ uptake have not been investigated in animal models. The wealth of culture studies has nonetheless demonstrated the potential importance of Aβ uptake mechanisms in the pathogenesis of AD.
The authors acknowledge support from CIHR (J. McLaurin), NSERC (J. McLaurin), Ontario Alzheimer's Society (J. McLaurin), and Ontario Postdoctoral Fellowship (A. Y. Lai).
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text: for my podcast on the news this week go to www.moesports.com (http://www.moesportsblog.com) and click on my newest addition. The Nba has had a crazy week of publicity, with the missed calls in the Lakers Spurs game, the new rules for giving fines for flopping and all the big playoff games this week. The NBA is going through some major changes with now starting to take control of the players who get away with flopping over and over (Ginobili, Kerilinko, Battier...) there will now be fines given out to players who flop over and over and the fines will increase for each flop. I am looking for the league to be handing technicals for each flop as well, the nba can start really hunting down the BS players in the league which will cause the league to get a new cleaner look. On to playoff talk, I am looking for the Lakers to win the series now even though I would rather the Spurs win. I dont see the Spurs coming back from 3-1 against a team 10 times faster than them. The Spurs just cant pull it off and consider the Spurs though winning 4 NBA titles never pulled off consecutive titles so it wouldnt be right for them to win it all this year.

subset: commoncrawl


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Up next in Scarves & Other Accessories (28 videos)
The key to looking chic? The right accessories. Learn how to rock a summer scarf; choose the best handbag for your outfit; tie a scarf into a Ladies Ascot, French twist, or even a sexy top; choose sunglasses that flatter your face; prevent hat head; tie a turban; and much, much more with these Howcast videos.
You Will Need
- A measuring tape
- A variety of belts
- A selection of outfits
- A men's tie (optional)
- Velcro (optional)
Step 1
Try outfit first
Try on the outfit and decide where you want the belt to sit – hips or waist. Use a measuring tape to determine the proper belt length
Step 2
Determine width
Determine the width you need. A belt worn over a dress or shirt can be any width. If you're wearing it around your hips, use a belt that is narrow at the top and follows the contour of your hips.
Step 3
Choose a color
Select a belt that is the same color as your outfit. Or, if you choose a belt for contrast, make sure it complements colors or design elsewhere in the outfit.
Step 4
Enhance but don't clash
Enhance your outfit with a fancy-cut or textured belt, but avoid clashing. For a conservative ensemble the belt should be less noticeable.
Step 5
Highlight your waist
Highlight your waist when wearing separates by tucking your shirt in. Add a belt that best fits the belt loop width.
Step 6
Try fun alternatives
Wear metal belts with segments, Indian beads and leather, fancy fabric weaves, even scarves, for a fun look when going casual.


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With tax loss, small business gains
PUBLISHED: 12 May 2012 00:05:07 | UPDATED: 12 May 2012 11:33:58PUBLISHED: 12 May 2012 PRINT EDITION: 12 May 2012Katie Walsh
Business and industry groups have thrashed the federal government for its failure to implement the promised company tax cut in the budget, but at least one sector has benefited from the funds provided by that backflip – small businesses.
From July, the new carry-back loss measure will allow small businesses to draw from taxes paid in the previous year to get a refund of up to $300,000 when they are in the red, extending to a two-year carry-back from the 2014 tax year.
It is a $700 million gift to 110,000 companies over the next four years but therein lies the rub: it is limited to incorporated businesses. The roughly three-quarters of the nation's 2.7 million small businesses that operate under different structures, such as sole traders or partnerships, miss out.
It is a failing that has disappointed many. The Australian Chamber of Commerce & Industry has pointed out that the benefit is meagre compared to the $4.8 billion that a 1 percentage point cut to the company income tax rate would have delivered – although again, only incorporated businesses.
Despite its shortcomings, small businesses have welcomed the change. "It gives people who have been through a hard time the opportunity to use tax to an advantage," said Council of Small Business of Australia chief executive Peter Strong. As independent MP Rob Oakeshott, a supporter of the initiative, has noted, making the measure a reality was the important thing, however "small" it may start out as.
The Australian Financial Review
Read more
People | Peter Strong, Rob Oakeshott |
Topics | Economy /Taxation |


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@ZipLine-- Is he going to have his gallbladder removed?
I hope the taste of bile disappears after that. In my case, it was just the opposite. I developed the bile taste in my mouth after my gallbladder removal surgery. My doctor said that the bile taste will slowly go away and it did. So if your dad continues to have this issue for a while after the surgery, don't be surprised. Chewing gum helps get rid of the taste.


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Painting Power
Tuition: $149.00
Instructor: Judith Bogart
Time: 1:00 p.m. - 4:00 p.m.
Location: LCC East
Express yourself in watercolor and tempera painting with the guidance of a professional artist. This talented instructor will show you how to compose your work of art, study and detail your subject matter and bring out your hidden talent. Discover color by mixing and preparing your palette and preparing yourself to follow a process in creating a work of art that reflects feeling, emotion and texture.


text: Interview Tut YanasPrecursor :iconcommunityrelations: communityrelations :iconcommunityrelations:An Interview with :iconYanasPrecursor: YanasPrecursor and a Tutorial she created, "Tips for Entering Contests" ~How did you get started on dA? A good friend showed me his art here on deviantART. When I took a look around I felt inspired to join as well. At the time I was only going to High School and doing some intense gaming.. after joining I began my journey in digital art which was mostly abstract and 3-D renders inspired by my friend, vhm-Cain.Is there a meaning behind your screen name? Yes, Yana is definitely Latin and is the female version of the male name Yan. Yan comes from Janus who is the God of light. Precursor has several links but I perceived it as "one who foresees" or an omen; therefore, Yanasprecursor could mean several things; initially my intentions were "god of li


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Assets auctioned as Johel Group in receivership
The fate of Lake Cowichan's Johel Brothers Contracting was reflected in a recent massive public auction of the firm's construction vehicles.
As instructed by PricewaterhouseCoopers Inc., Maynards auctioneers held the Feb. 19 sale of Johel Brothers' large and small construction equipment.
The auction, held in Lake Cowichan at the Johel Group site, was ordered by PWC in its role as court-appointed receiver for the struggling, long-time lake company.
"We have no comment at this time, however, will be filing a receiver's report within a few weeks time where you can obtain further updates on the file. It will be posted to our website," PWC senior associate Blair W. Linnen said in an email to the News Leader Pictorial.
Owner Dave Johel and his staff did not return repeated calls last week.
Browsing some 20-pages of items on the block at Maynards, it appears a wide range of the company's gear was being sold.
Hand tools and a fleet of pick-up trucks, to shelving, dump trucks — even hot-water heaters — were up for bids.
Results of the auction were unavailable, but it attracted a lot of attention.
Throughout the day more than 350 registered bidders checked out the equipment on location.
Bidders arrived from as far as California to the Yukon and Alberta. Other bidders from as far away as Dubai used the internet to purchase the equipment they were interested in.
According to a statement on the PWC website, various entities within the Johel Group were put into receivership on Oct. 19.
"Following the receiver's application on Dec. 20, 2013, the court authorized the proposed auction agreement," PWC states.
Johel Brothers, a valley excavating-and-development pillar, for 33 years, filed for creditor protection last spring, under the Companies' Creditors Arrangement Act.
More information about the receivership can be read by going to pwc.com/ca and searching Johel Group.
—with a file from Malcolm Chalmers
Read the latest eEdition
Browse the print edition page by page, including stories and ads.
Feb 27 edition online now. Browse the archives.


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Hamburg Wadden Sea National Park is located in the north of Germany. It surrounds a small group of islands on the North Sea coast off Cuxhaven, just beyond the Elbe estuary, and protects around 12,000 hectares of coastal mudflats.
Three islands on the coast of Lower Saxony, off Cuxhaven and just beyond the Elbe estuary, are the focal points of the Hamburg Wadden Sea National Park, the smallest of the three Wadden Sea parks. They are the lush, green island of Neuwerk (population approx. 40), the dune island of Scharhörn and the artificial island of Nigehörn.
On fascinating excursions through the mudflats, visitors can search for amber and see large colonies of little, common, sandwich and Arctic terns. In addition to the natural sights of the wetlands, the region also offers many cultural attractions.
The history of Neuwerk Island is particularly intriguing, with records linking it to the city of Hamburg going back as far as 1299. The island paths lead through verdant scenery to a fortified tower in the Elbe estuary, a relic from the days of the Hanseatic League. This bastion was an outpost in the battle against piracy. Feature attractions include horse-drawn carriage rides through the mudflats from Sahlenburg to the car-free island of Neuwerk and cruises from Cuxhaven to Neuwerk, which offers guided bird-watching tours and excursions through the salt marshes and the coastal mudflats. There is also a delightful exhibition of amber.
The mudflats are again much in evidence on the trip from Neuwerk to Scharhörn. Originally a sandbank, Scharhörn is popular with visitors for its colonies of sea birds. Just like the artificial bird island of Nigehörn, which is closed to the public, Scharhörn has impressive expanses of unspoilt natural scenery.
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Henry and I went to see the pyramids, which are pointy buildings in the desert. Roy said something about mummy being found in one and being taken to the museum in Cairo. I didn't know she was lost and don't understand why they took her there, but Henry and I went to see her anyway.
We searched the museum and found the Mummies Department but it was full of injured people all bandaged up. There must have been a very bad accident. We then found a room for Animal Mummies but didn't find mine there either, so I think Roy must be confused, again.
We drove to a town called Hurghada where Henry and I wanted to play on the beach, but Roy and Chris didn't like it and refused to stay. So we continued to Luxor. It has become very hot now and Henry's coat is too heavy so he has decided to moult. There is fur everywhere.
We visited some temples around Luxor and I went off to the Valley of the Queens. I suddenly smelt a bone and, as I was feeling peckish, I started to dig. I soon had three bones and was digging furiously for a fourth when a guard lifted me bodily and threw me out of the site. He didn't even let me fetch the bones I had already got, so I assume he must have wanted them for himself.
We are now in a town called Aswan. I am going to search in the desert for more bones and Henry was last seen sun-bathing. He says his new coat is too light and he wants to give it a tan. Roy says we are waiting for a boat, but Henry and I are quite happy here.
Don't forget to take a look at Benji's Odyssey in the photo gallery. There are forty pictures, now.


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Teen arrested for bringing loaded handgun to Glen Oaks High School
POSTED: Monday, April 15, 2013 - 1:30pm
UPDATED: Monday, April 15, 2013 - 6:09pm
BATON ROUGE, LA (NBC33) — An 8th grader at Glen Oaks High School was arrested today for allegedly bringing a loaded gun on campus.
The East Baton Rouge Parish Sheriff's Office reports that a teacher saw a 15-year-old student place something in his sock at some point during the morning on Monday, April 15. A Resource Officer at the school searched the student and found a loaded .22 revolver.
Officials say the student provided no explanation for bringing the weapon to the school. It was determined that no threats were made.
The teen was arrested and charged with Illegal Carrying of a Weapon on School Property. He was booked into the Juvenile Detention Center.
Students with information concerning this incident or similar incidents are encouraged to notify a school administrator, contact the East Baton Rouge Sheriff's Office at (225) 389-5000 or Crime Stoppers anonymously at (225) 344- STOP or (225) 344-7867. Students can also text "CS225" plus their message to CRIMES (274637).


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How Smart Is Your Dog? Test Your Pet's Brain Power for Science
Wired: What do you hope to accomplish with Dognition?
Hare: There are three goals. One is outreach, to get people to have a better understanding of what science is, and that they can participate in it. I want to get people to not be scared of science. The second goal is discovery. It can give us a really powerful tool to answer scientific questions. The third thing is funding. When we're profitable we'll fund non-invasive animal behavior research with 2 to 5 percent of the profits.
Wired: That's not very much, is it?
Hare: It depends what the profits are. I'm not saying it's a huge percentage, but it's not nothing. The National Science Foundation budget for anthropology, basically all research on human evolution, is $3 million a year. If we could contribute another million or two, that would be great.
Wired: Is that realistic?
Hare: One percent of the market would be 1 million dogs, more or less worldwide. In our beta program we had people from 38 countries sign up.
Wired: That's 60 million bucks!
Hare: And that's just for the canine assessment test. But there's also a subscription program. You pay $10 a month and you get a new game every month and access to trainer tips. We've got some really awesome trainers who will give ideas on how to train your dog based on the cognitive profile. That's going to launch in March.
Wired: How would researchers get access to funding?
Hare: We have to figure out how that's going to work. We have a scientific advisory board, and the model would be something like National Geographic or the Leakey Foundation. There would be applications and people would decide.
Wired: You're billing this as citizen science, but doesn't asking people to pay to play go against the spirit of citizen science?
Hare: That's a great question, and it's true, I don't think it's conventional to have people who are participating in citizen science pay. Citizen science is an altruistic endeavor. It's a collective action, crowdsourcing approach. We're doing that, but the other half of it is we'll tell you about your dog. That's what you're paying for, the technology and expertise and the time that went into developing this new way that you can find out instantly about your dog in your own home. And it's also going to help us understand all dogs. It is different, and I think some people will think it's good and some people will see it as bad, but it's the only way we could do this. I don't feel bad about it.


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Fires in Kingtown area labeled "suspicious"
POSTED: Wednesday, August 29, 2012 - 10:00am
UPDATED: Wednesday, August 29, 2012 - 10:14am
NACOGDCOHES, TX — A series of small fires along County Road 555 north of Kingtown on Tuesday have been called suspicious by Texas Forest Service officials.
Volunteers from Woden and Kingtown were joined by TFS crews to fight the multiple fires which burned on both sides of the road Tuesday afternoon. TFS spokesperson John Boyette said the location and spacing of the fires made them appear "suspicious in nature."
Read more from the Nacogdoches Daily Sentinel.


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Join IPI
CAPP Program
The City of Fort Lauderdale has embarked on a groundbreaking initiative, leading the way in exploring sustainability in surface parking lots and pushing the boundaries of sustainability in the parking industry. The city has collaborated with the International Parking Institute, the Green Parking Council, and Timothy Haahs & Associates to design and construct one of the greenest parking lots in the country as a demonstration site for best practices, new technology, and innovative strategies. The Orchid Lot, located adjacent to City Hall, will be redesigned, retrofitted, and launched as a pilot site to showcase strategies and educate both parking professionals and the general public. The entire team has brought to fruition an exciting project, to be featured as the tour at the IPI 2013 Conference & Expo and designated a Green Parking Council Demonstrator Site, that integrates sustainability in planning, water use and management, energy use and management, and programs and operations. This project takes sustainability from a high level conversation of "should do" to an on the ground experience and reality check of "we did." Featured strategies include construction waste management, recycling, bicycle parking, energy-efficient lighting and control, alternative fuel vehicles and charging stations, and more.
The tour of the project will be offered to conference attendees on Tuesday, May 22 at 3:15 p.m. Tour participants will receive a packet of materials on green and sustainable product/service providers. The Greening the Lot project is supported by a broad range of green parking technology providers. Thanks to the project sponsors and supporters:
Are you ready? Less than 20 days until the opening of the IPI Conference & Expo in Fort Lauderdale, Florida. There's still time to register and plan ahead to get the most out of all the opportunities in store for you! Here are six things to help you ride the wave to the best parking event ever:
Explore more and register here: ipiconference.parking.org
Valet employees can be taught the basics of their jobs, but is caring -- really caring -- something that can be learned? The Cleveland Clinic thinks so, and has brought top-notch customer service and productivity (and caring) from art to science.
This webinar will cover how a large medical center embraced a custom model of valet staffing productivity, bi-weekly payroll cost analysis, master schedule methodology, shift huddles, and finally an employee culture of being courteous, attentive, resourceful, and efficient (that's the CARE). You'll learn about the Cleveland Clinic's custom productivity tools that evaluate staffing needs to optimize retrieval times and minimize congestion and costs. Other topics to be covered include master schedules, shift huddles, staffing vacancy tracking, and the service expectations that ensure all employees CARE about their work. The results have been fantastic!
Instructor: Stephanie Barnes, Director, Cleveland Clinic Parking Services
Wednesday, May 15 at 2:00 p.m. EDT/ 11:00 a.m. PDT (60 minutes)
For more information and to register!
All CAPP candidates and graduates who register and participate in the webinar will receive .5 points toward their CAPP certification or recertification requirements.
The Parking Professional: Food Trucks, Meters, and More
The May issue is chock-full of information and ideas for you to put to work, including a feature on how different cities are dealing with food trucks and parking, smart meters, and how to build the right amount of parking for different needs. And also use the Expo guide in the issue to plan your visits with exhibitors at the upcoming IPI Conference & Expo, May 19-22 in Fort Lauderdale.
Rolling Controversy
City parking departments are finding unique ways to balance the needs of restaurants, citizens, and entrepreneurs in what many have deemed the downtown food truck wars.
Beyond Supply & Demand
Moving past traditional spaces-per-square-foot calculations to build parking that's actually needed.
To Market, To Market
How one municipality is using market-based pricing for on-street parking with great results.
Mensa Meters
Transitioning to smart meters can have wide effects on municipality parking.
Prep Work
When it comes to passing a PCI audit, the key is in a familiar mantra: be prepared.
Tourist Transitions
Resort towns face special challenges when it comes to parking management plans.
The 2013 IPI Conference & Expo Products and Services Directory
Where to find products and resources at the 2013 IPI Conference & Expo.
Questions, comments, or thoughts about The Parking Professional? Be sure to stop by The Parking Professional booth (#836) at the IPI Conference & Expo and share them with Kim Fernandez, editor, The Parking Professional.
IPI members can access the online version of the May issue now.
Have a job to post? Reach thousands of parking professionals at www.parking.org/careers. Looking for a job in the parking industry? View our latest listings:
General Manager - Municipal Parking Department - City of Detroit, Mich.
Parking Analyst - San Francisco Municipal Transportation Agency
Senior Customer Facilities & Accessible Services (CFAS) Coordinator - Sound Transit
Director of Parking and Traffic - Stephen F. Austin State University
View more job listings
Santa Monica, Calif.For: Transit Project Marketing ServicesTexas Tech UniversityFor: Printing of Tickets/Parking PassesUniversity of Texas Southwestern Medical CenterFor: Valet Parking Vehicle Tracking and Retrieval SystemCity of Glendale, Calif.For: Parking Citation Processing, Delinquent Collection Services and Preferential Parking Permit ProgramAmtrak, Lancaster, Pa.For: Parking Management Services
View all RFPs
Organizations can post RFPs at no charge. For more information, contact Henry Wallmeyer at 540.371.7535.
*Not an IPI member, but want access to the RFPs? Join Now!
Sign up to receive Parking Matters® Blog posts as they are published (about two to three times each week). Recent posts:
Join the conversation and sign up for free.
Solar Roadways chief presented for Google/GE. Don't miss his keynote at the IPI Conference & Expo! http://ow.ly/knweb
Santa Rosa may spend $172K to bring back parking meters http://ow.ly/kswmu
Apple Patents Method for Locating a Vehicle in a Parking Garage http://ow.ly/kswHt
Proposed University of Utah parking garage spurring student protest http://ow.ly/ksxgy
Boylston Strong: Parking meters fees waived in Back Bay to encourage commerce http://ow.ly/ksxEV
Fredericksburg ponders more parking decks http://ow.ly/ksy96
Sacramento plans solar-powered 'smart' parking meters http://ow.ly/kz0dR
Hapless attempt at parallel parking in Belfast is internet hit http://ow.ly/kz108
Free Sunday parking in Chicago neighborhoods, meter dispute settled http://ow.ly/kz79b


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Amazing quality! I love this skin! This has got to be my favourite amongst the designs I bought from you guys, and I love the fact that I can easily interchange the skins to the pattern I feel like wearing for the day.Sarah Jessy, United States