where is myosin found in the skeletal muscle cells
the sarcomere
2674969
to actin again to repeat the cycle. The combined effect of the myriad power strokes causes the muscle to contract. The wide variety of myosin genes found throughout the eukaryotic phyla were named according to different schemes as they were discovered. The nomenclature can therefore be somewhat confusing when attempting to compare the functions of myosin proteins within and between organisms. Skeletal muscle myosin, the most conspicuous of the myosin superfamily due to its abundance in muscle fibers, was the first to be discovered. This protein makes up part of the sarcomere and forms macromolecular filaments composed of multiple myosin
Myosin
2345156
its axis. In addition to the actin and myosin components that constitute the sarcomere, skeletal muscle fibers also contain two other important regulatory proteins, troponin and tropomyosin, that are necessary for muscle contraction to occur. These proteins are associated with actin and cooperate to prevent its interaction with myosin. Skeletal muscle cells are excitable and are subject to depolarization by the neurotransmitter acetylcholine, released at the neuromuscular junction by motor neurons. Once a cell is sufficiently stimulated, the cell's sarcoplasmic reticulum releases ionic calcium (Ca2+), which then interacts with the regulatory protein troponin. Calcium-bound troponin undergoes a conformational change that
Skeletal muscle
4979137
unit of skeletal muscle. The sarcomere is a highly structured protein array, consisting of interdigitating thick and thin filaments, where the thin filaments are tethered to a protein structure, the Z-line. The dynamic interaction between the thick and thin filaments results in muscle contraction. Myosin belongs to a family of motor proteins, and the muscle isoforms of this family comprise the thick filament. The thin filament is made of the skeletal muscle isoforms of actin. Each myosin protein 'paddles' along the thin actin filament, repeatedly binding to myosin-binding sites along the actin filament, ratcheting and letting go. In effect, the
Tropomyosin
2674969
to actin again to repeat the cycle. The combined effect of the myriad power strokes causes the muscle to contract. The wide variety of myosin genes found throughout the eukaryotic phyla were named according to different schemes as they were discovered. The nomenclature can therefore be somewhat confusing when attempting to compare the functions of myosin proteins within and between organisms. Skeletal muscle myosin, the most conspicuous of the myosin superfamily due to its abundance in muscle fibers, was the first to be discovered. This protein makes up part of the sarcomere and forms macromolecular filaments composed of multiple myosin
Myosin
11307184
of endogenous mutant "Mybpc3". Additional expression of a sarcomeric protein is expected to replace partially or completely the endogenous protein level in the sarcomere, as it has been shown in transgenic mice expressing sarcomeric proteins. Myosin binding protein C, cardiac The myosin-binding protein C, cardiac-type is a protein that in humans is encoded by the "MYBPC3" gene. This isoform is expressed exclusively in heart muscle during human and mouse development, and is distinct from those expressed in slow skeletal muscle (MYBPC1) and fast skeletal muscle (MYBPC2). cMyBP-C is a 140.5 kDa protein composed of 1273 amino acids. cMyBP-C is a
Myosin binding protein C, cardiac
1394780
to keep warm. Skeletal muscles, like other striated muscles, are composed of myocytes, or muscle fibers, which are in turn composed of myofibrils, which are composed of sarcomeres, the basic building block of striated muscle tissue. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere. The best proposed model for understanding contraction is the sliding filament model of muscle contraction. Within the sarcomere, actin and myosin fibers overlap in a contractile motion towards each other. Myosin filaments have club-shaped heads that project toward the actin filaments. Larger structures along the myosin filament called
Muscular system
2345145
fibres are cylindrical, and have more than one nucleus. They also have multiple mitochondria to meet energy needs. Muscle fibers are in turn composed of myofibrils. The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, which are the basic functional units of the muscle fiber. The sarcomere is responsible for the striated appearance of skeletal muscle, and forms the basic machinery necessary for muscle contraction. Connective tissue is present in all muscles as fascia. Enclosing each muscle is a layer of connective tissue known as the epimysium; enclosing each fascicle is a layer called the
Skeletal muscle
2483897
which forms the thick filament, and actin, which forms the thin filament. Myosin has a long, fibrous tail and a globular head, which binds to actin. The myosin head also binds to ATP, which is the source of energy for muscle movement. Myosin can only bind to actin when the binding sites on actin are exposed by calcium ions. Actin molecules are bound to the Z line, which forms the borders of the sarcomere. Other bands appear when the sarcomere is relaxed. A muscle fiber from a biceps muscle may contain 100,000 sarcomeres. The myofibrils of smooth muscle cells are
Sarcomere
3981617
. Like skeletal muscles, cytosolic ions are also required for crossbridge cycling in smooth muscle cells. The two sources for cytosolic in smooth muscle cells are the extracellular entering through calcium channels and the ions that are released from the sarcoplasmic reticulum. The elevation of cytosolic results in more binding to calmodulin, which then binds and activates myosin light-chain kinase. The calcium-calmodulin-myosin light-chain kinase complex phosphorylates myosin on the 20 kilodalton (kDa) myosin light chains on amino acid residue-serine 19, initiating contraction and activating the myosin ATPase. Unlike skeletal muscle cells, smooth muscle cells lack troponin, even though they contain
Muscle contraction
12561001
formed from the somatic lateral plate mesoderm. Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongate skeletal muscle cells. The three types of muscle (skeletal, cardiac and smooth) have significant differences. However, all three use the movement of actin against myosin to create contraction. In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the nerves, the motoneurons (motor nerves) in particular. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle
Muscle
4739448
myosin in thick filaments. Phosphorylated myosin is able to form crossbridges with actin thin filaments, and the smooth muscle fiber (i.e., cell) contracts via the sliding filament mechanism. (See reference for an illustration of the signaling cascade involving L-type calcium channels in smooth muscle). L-type calcium channels are also enriched in the t-tubules of striated muscle cells, i.e., skeletal and cardiac myofibers. When these cells are depolarized, the L-type calcium channels open as in smooth muscle. In skeletal muscle, the actual opening of the channel, which is mechanically gated to a calcium-release channel (a.k.a. ryanodine receptor, or RYR) in the
Voltage-gated calcium channel
20146469
skeletal muscle myosin IC50=0.4 μM). It has been successfully used in fluorescent imaging experiments involving myosin IIA-GFP expressing live dendritic cells A water-soluble blebbistatin derivative developed in 2016, its high water solubility (~400 uM) enables in vivo research applications. Para-aminoblebbistatin is a slightly weaker myosin inhibitor than blebbistatin (for rabbit skeletal muscle myosin S1 IC50=1.3 μM, for Dictyostelium discoideum myosinII motor domain IC50=6.6 μM with only 90% maximal inhibition), it is non-fluorescent, photostable, neither cytotoxic nor phototoxic. A photoreactive myosin inhibitor developed in 2012. A permanent inhibition of myosin may be achieved by covalently crosslinking the inhibitor azidoblebbistatin to its
Blebbistatin
2483887
the thick (myosin) and thin (actin) filaments along each other. The filaments of myofibrils, myofilaments, consist of two types, thick and thin: The protein complex composed of actin and myosin is sometimes referred to as "actinomyosin". In striated muscle, such as skeletal and cardiac muscle, the actin and myosin filaments each have a specific and constant length on the order of a few micrometers, far less than the length of the elongated muscle cell (a few millimeters in the case of human skeletal muscle cells). The filaments are organized into repeated subunits along the length of the myofibril. These subunits
Myofibril
2345147
Differentiation into this state is primarily completed before birth with the cells continuing to grow in size thereafter. Skeletal muscle exhibits a distinctive banding pattern when viewed under the microscope due to the arrangement of cytoskeletal elements in the cytoplasm of the muscle fibers. The principal cytoplasmic proteins are myosin and actin (also known as "thick" and "thin" filaments, respectively) which are arranged in a repeating unit called a sarcomere. The interaction of myosin and actin is responsible for muscle contraction. Every single organelle and macromolecule of a muscle fiber is arranged to ensure form meets function. The cell membrane
Skeletal muscle
14245547
of muscle wasting. C2C12 cells demonstrate rapid development and maturation into functional skeletal muscle cells or cardiac muscle cells, having the ability to contract and generate force. The rate of muscle formation from C2C12 cells can be controlled by the introduction of loss-of-functions genes vital for the fusion of myoblasts and myogenesis. Under necrotic conditions, such as tumor necrosis factor alpha (TNF-α), direct protein loss, particularly myosin heavy chain protein, in C2C12 skeletal muscle cells has been shown. C2C12 cells were used to elucidate inactivated X chromosome (Xi) replication during early S-phase of the cell cycle and is regulated epigenetically.
C2C12
7043411
muscle fibers and myofilaments. However, there is some evidence of animal satellite cells differentiating into new muscle fibers and not merely providing a support function to muscle cells. The weakened contractile function of skeletal muscle is also linked to the state of the myofibrils. Recent studies suggest that these conditions are associated with altered single fiber performance due to decreased expression of myofilament proteins and/or changes in myosin-actin cross-bridge interactions. Furthermore, cellular and myofilament-level adaptations are related to diminished whole muscle and whole body performance. Myofilament Myofilaments are the filaments of myofibrils, constructed from proteins, principally myosin or actin. Types
Myofilament
7043404
Myofilament Myofilaments are the filaments of myofibrils, constructed from proteins, principally myosin or actin. Types of muscle are striated muscle (such as skeletal muscle and cardiac muscle), obliquely striated muscle (found in some invertebrates), and smooth muscle. Various arrangements of myofilaments create different muscles. Striated muscle has transverse bands of filaments. In obliquely striated muscle, the filaments are staggered. Smooth muscle has irregular arrangements of filaments. There are three different types of myofilaments: thick, thin, and elastic filaments. The protein complex composed of actin myosin, contractile proteins, is sometimes referred to as "actomyosin". In striated muscle, such as skeletal and
Myofilament
20146467
nm, therefore at high concentrations its fluorescence interferes with GFP imaging or FRET experiments. Reduction of the concentration of blebbistatin to 6.25 uM allows for FRET imaging in isolated adult mouse cardiac muscle cells. Long-term incubation with blebbistatin results in cell damage and cytotoxicity, which are independent of the myosin inhibitory effect. This photo-instability, phototoxicity and fluorescence makes in-vivo imaging of blebbistatin-treated samples impossible. Blebbistatin is a potent inhibitor of nonmuscle myosin IIA and IIB, cardiac myosin, skeletal myosin and smooth muscle but does not inhibit myosin I, V and X. The table below summarizes IC50 data of blebbistatin on
Blebbistatin
10704122
tissue is also possible, depending on among other things the content of myoglobin, mitochondria, myosin ATPase etc. Muscle cells (myocytes) are elongated cells ranging from several millimetres to about 10 centimetres in length and from 10 to 100 micrometres in width. These cells are joined together in tissues that may be either striated or smooth, depending on the presence or absence, respectively, of organized, regularly repeated arrangements of myofibrillar contractile proteins called myofilaments. Striated muscle is further classified as either skeletal or cardiac muscle. Striated muscle is typically subject to conscious control, while smooth muscle is not. Thus, muscle tissue
Muscle tissue
2446377
muscles are unable to relax properly due to myosin fibers not fully detaching from actin filaments. In skeletal muscle, ATP levels must be large enough to bind to the myosin heads for them to attach or detach from the actin and allow contraction or relaxation; the absence of enough levels of ATP means that the myosin heads remains attached to actin. The muscle must be allowed to recover (resynthesize ATP), before the myosin fibres can detach and allow the muscle to relax. Skeletal muscles work as antagonistic pairs. Contracting one skeletal muscle requires the relaxation of the opposing muscle in
Cramp
7043405
cardiac muscle, the actin and myosin filaments each have a specific and constant length in the order of a few micrometers, far less than the length of the elongated muscle cell (a few millimeters in the case of human skeletal muscle cells). The filaments are organized into repeated subunits along the length of the myofibril. These subunits are called sarcomeres. The contractile nature of this protein complex is based on the structure of the thick and thin filaments. The thick filament, myosin, has a double-headed structure, with the heads positioned at opposite ends of the molecule. During muscle contraction, the
Myofilament
17073963
paradox of rapamycin inhibiting the immune system response has been linked to several reasons, including its interaction with regulatory T cells. Resistance exercise, the amino acid -leucine, and beta-hydroxy beta-methylbutyric acid (HMB) are known to induce signaling cascades in skeletal muscle cells that result in mTOR phosphorylation, the activation of mTORC1, and subsequently the initiation of myofibrillar protein synthesis (i.e., the production of proteins such as myosin, titin, and actin), thereby facilitating muscle hypertrophy. The NMDA receptor antagonist ketamine has been found to activate the mTORC1 pathway in the medial prefrontal cortex (mPFC) of the brain as an essential downstream
MTORC1
11307165
Myosin binding protein C, cardiac The myosin-binding protein C, cardiac-type is a protein that in humans is encoded by the "MYBPC3" gene. This isoform is expressed exclusively in heart muscle during human and mouse development, and is distinct from those expressed in slow skeletal muscle (MYBPC1) and fast skeletal muscle (MYBPC2). cMyBP-C is a 140.5 kDa protein composed of 1273 amino acids. cMyBP-C is a myosin-associated protein that binds at 43 nm intervals along the myosin thick filament backbone, stretching for 200 nm on either side of the M-line within the crossbridge-bearing zone (C-region) of the A band in striated
Myosin binding protein C, cardiac
2047053
(mainly β-actin) that does not take part in contraction, but that polymerizes just below the plasma membrane in the presence of a contractile stimulant and may thereby assist in mechanical tension. Alpha actin is also expressed as distinct genetic isoforms such as smooth muscle, cardiac muscle and skeletal muscle specific isoforms of alpha actin. The ratio of actin to myosin is between 2:1 and 10:1 in smooth muscle. Conversely, from a mass ratio standpoint (as opposed to a molar ratio), myosin is the dominant protein in striated skeletal muscle with the actin to myosin ratio falling in the 1:2 to
Smooth muscle
7345228
lo-12-fold higher than that of MLCK and only 2-3-fold less than that of myosin. Vascular muscles have a lower KRP/MLCK ratio. Telokin is expressed at very high levels in intestinal, urinary, and reproductive tract smooth muscle, at lower levels in vascular smooth muscle, and at undetectable levels in skeletal or cardiac muscle or nonmuscle tissues. Although telokin is strongly activated by myocardin and myocardin is highly expressed in vascular smooth muscle cells, there is relatively little expression of telokin in these cells. This suggests that an inhibitory factor must be attenuating the activity of the telokin promoter in vascular smooth
Telokin
2981922
for the myosin crossbridge, thus preventing contraction. When the muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic membrane and release calcium into the sarcoplasm. Some of this calcium attaches to troponin, which causes it to change shape, exposing binding sites for myosin (active sites) on the actin filaments. Myosin's binding to actin causes crossbridge formation, and contraction of the muscle begins. Troponin is found in both skeletal muscle and cardiac muscle, but the specific versions of troponin differ between types of muscle. The main difference is that the TnC subunit of troponin
Troponin
6421719
data to determine whether or not an individual is suffering from severe sarcopenia. Sarcopenia is also marked by a decrease in the circumference of distinct types of muscle fibers. Skeletal muscle has different fiber-types, which are characterized by expression of distinct myosin variants. During sarcopenia, there is a decrease in "type 2" fiber circumference (Type II), with little to no decrease in "type I" fiber circumference (Type I), and deinervated type 2 fibers are often converted to type 1 fibers by reinnervation by slow type 1 fiber motor nerves. Satellite cells are small mononuclear cells that abut the muscle fiber.
Sarcopenia
11217197
MYH9 Myosin-9 also known as myosin, heavy chain 9, non-muscle or non-muscle myosin heavy chain IIa (NMMHC-IIA) is a protein which in humans is encoded by the "MYH9" gene. Non-muscle myosin IIA (NM IIA) is expressed in most cells and tissues where it participates in a variety of processes requiring contractile force, such as cytokinesis, cell migration, polarization and adhesion, maintenance of cell shape, and signal transduction. Myosin IIs are motor proteins that are part of a superfamily composed of more than 30 classes. Class II myosins include muscle and non-muscle myosins that are organized as hexameric molecules consisting of
MYH9
11318007
isoforms in one given species, indicating early diverged functions of the muscle fiber type-specific isoforms as well as the conservation of functions for each muscle fiber type. Fast skeletal muscle TnI was first cloned from a skeletal muscle cDNA library. It is generally observed that fsTnI is exclusively expressed in fast twitch skeletal muscle fibers. More recent studies reported that subunits of fast skeletal muscle troponin (fsTnI, fsTnT, fsTnC) were expressed at significant levels in smooth muscle cells of mouse blood vessels, bladder and bronchi. Expression of fsTnI was also found in non-muscle cells, such as human corneal epithelial cells
TNNI2
2502821
bands composed mainly of a protein called actin, and darker A bands composed mainly of myosin. Cardiomyocytes contain T-tubules, pouches of membrane that run from the surface to the cell's interior which help to which improve the efficiency of contraction. The majority of these cells contain only one nucleus (although they may have as many as four), unlike skeletal muscle cells which typically contain many nuclei. Cardiac muscle cells contain many mitochondria which provide the energy needed for the cell in the form of adenosine triphosphate (ATP), making them highly resistant to fatigue. T-tubules are microscopic tubes that run from
Cardiac muscle
11318565
MYL2 Myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC-2) also known as the regulatory light chain of myosin (RLC) is a protein that in humans is encoded by the "MYL2" gene. This cardiac ventricular RLC isoform is distinct from that expressed in skeletal muscle (MYLPF), smooth muscle (MYL12B) and cardiac atrial muscle (MYL7). Ventricular myosin light chain-2 (MLC-2v) refers to the ventricular cardiac muscle form of myosin light chain 2 (Myl2). MLC-2v is a 19-KDa protein composed of 166 amino acids, that belongs to the EF-hand Ca binding superfamily. MLC-2v interacts with the neck/tail region of the muscle thick
MYL2
5629591
actin filaments anchor within the cell. T-tubules within the heart are closely associated with the intracellular calcium store known as the sarcoplasmic reticulum in specific regions referred to as terminal cisternae. The association of the T-tubule with a terminal cistern is known as a diad. In skeletal muscle cells, T-tubules are between 20 and 40 nm in diameter and are typically located either side of the myosin strip, at the junction of overlap between the A and I bands. T-tubules in skeletal muscle are associated with two terminal cisternae, known as a triad. The shape of the T-tubule system is
T-tubule
2483896
Sarcomere A sarcomere (Greek "sarx" "flesh", "meros" "part") is the basic unit of striated muscle tissue. It is the repeating unit between two Z lines. Skeletal muscles are composed of tubular muscle cells (myocytes called muscle fibers or myofibers) which are formed in a process known as myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes. Two of the important proteins are myosin,
Sarcomere
3981618
the thin filament protein tropomyosin and other notable proteins – caldesmon and calponin. Thus, smooth muscle contractions are initiated by the -activated phosphorylation of myosin rather than binding to the troponin complex that regulates myosin binding sites on actin like in skeletal and cardiac muscles. Termination of crossbridge cycling (and leaving the muscle in latch-state) occurs when myosin light chain phosphatase removes the phosphate groups from the myosin heads. Phosphorylation of the 20 kDa myosin light chains correlates well with the shortening velocity of smooth muscle. During this period, there is a rapid burst of energy utilization as measured by
Muscle contraction
20146464
Blebbistatin Blebbistatin is a myosin inhibitor mostly specific for myosin II. It is widely used in research to inhibit heart muscle myosin, non-muscle myosin II, and skeletal muscle myosin. Blebbistatin has been especially useful in optical mapping of the heart, and its recent use in cardiac muscle cell cultures has improved cell survival time. However, its adverse characteristics e.g. its cytotoxicity and blue-light instability or low solubility in water often make its application challenging. Recently its applicability was improved by chemical design and its derivatives overcome the limitations of blebbistatin. E.g. para-nitroblebbistatin and para-aminoblebbistatin are photostable, and they are neither
Blebbistatin
2503325
myocytes. This can occur through a simple lack of energy to fuel contraction, or through interference with the ability of Ca to stimulate actin and myosin to contract. Weakness Weakness or asthenia is a symptom of a number of different conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis. Muscle cells work by detecting a flow of electrical impulses from the
Weakness
2674966
Myosin Myosins () are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The term was originally used to describe a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue. Following the discovery by Pollard and Korn (1973) of enzymes with myosin-like function in "Acanthamoeba castellanii", a global range of divergent myosin genes have been discovered throughout the realm of eukaryotes. Although myosin was originally thought to be restricted
Myosin
11328818
binds the neck region of muscle myosin in adult atria. Two alternatively spliced transcript variants encoding the same protein have been found for this gene. Relative to ventricular essential light chain VLC-1, ALC-1 has an additional ~40 amino-acid N-terminal region that contains four to eleven residues that are critical for binding actin and modulating myosin kinetics. ALC-1 is expressed very early in skeletal muscle and cardiac muscle development; two E-boxes and CArG box in the "MYL4" promoter region regulate transcription. ALC-1 expression in cardiac ventricles decreases in early postnatal development, but is highly expressed in atria throughout all of adulthood.
MYL4
2674967
to muscle cells (hence "myo-"(s) + "-in"), there is no single "myosin"; rather it is a very large superfamily of genes whose protein products share the basic properties of actin binding, ATP hydrolysis (ATPase enzyme activity), and force transduction. Virtually all eukaryotic cells contain myosin isoforms. Some isoforms have specialized functions in certain cell types (such as muscle), while other isoforms are ubiquitous. The structure and function of myosin is globally conserved across species, to the extent that rabbit muscle myosin II will bind to actin from an amoeba. Most myosin molecules are composed of a head, neck, and tail
Myosin
2915114
Myocyte A myocyte (also known as a muscle cell) is the type of cell found in muscle tissue. Myocytes are long, tubular cells that develop from myoblasts to form muscles in a process known as myogenesis. There are various specialized forms of myocytes: cardiac, skeletal, and smooth muscle cells, with various properties. The striated cells of cardiac and skeletal muscles are referred to as muscle fibers. Cardiomyocytes are the muscle fibres that form the chambers of the heart, and have a single central nucleus. Skeletal muscle fibers help support and move the body and tend to have peripheral nuclei. Smooth
Myocyte
2674970
subunits. Similar filament-forming myosin proteins were found in cardiac muscle, smooth muscle, and nonmuscle cells. However, beginning in the 1970s, researchers began to discover new myosin genes in simple eukaryotes encoding proteins that acted as monomers and were therefore entitled Class I myosins. These new myosins were collectively termed "unconventional myosins" and have been found in many tissues other than muscle. These new superfamily members have been grouped according to phylogenetic relationships derived from a comparison of the amino acid sequences of their head domains, with each class being assigned a Roman numeral (see phylogenetic tree). The unconventional myosins also
Myosin
11328231
for normal cardiac function. MYL3 Myosin essential light chain (ELC), ventricular/cardiac isoform is a protein that in humans is encoded by the "MYL3" gene. This cardiac ventricular/slow skeletal ELC isoform is distinct from that expressed in fast skeletal muscle (MYL1) and cardiac atrial muscle (MYL4). Ventricular ELC is part of the myosin molecule and is important in modulating cardiac muscle contraction. Cardiac, ventricular ELC is 21.9 kDa and composed of 195 amino acids (See human MYL3 sequences features here). Cardiac ELC and the second light chain, regulatory light chain (RLC, MYL2), are non-covalently bound to IQXXXRGXXXR motifs in the 9
MYL3
11328228
MYL3 Myosin essential light chain (ELC), ventricular/cardiac isoform is a protein that in humans is encoded by the "MYL3" gene. This cardiac ventricular/slow skeletal ELC isoform is distinct from that expressed in fast skeletal muscle (MYL1) and cardiac atrial muscle (MYL4). Ventricular ELC is part of the myosin molecule and is important in modulating cardiac muscle contraction. Cardiac, ventricular ELC is 21.9 kDa and composed of 195 amino acids (See human MYL3 sequences features here). Cardiac ELC and the second light chain, regulatory light chain (RLC, MYL2), are non-covalently bound to IQXXXRGXXXR motifs in the 9 nm S1-S2 lever arm
MYL3
9788496
completely understood, it has been shown that it is closely associated with myosin as it is present in all skeletal and cardiac muscle from the earliest stages of muscle tissue formation. In Humans, myomesin is encoded by the genes MYOM1 and MYOM2. Myomesin Myomesin is an end line protein that is part of the M line. It is a protein found in the M-band of muscle sarcomeres in association with M-protein. It is found in both slow and fast muscle fibers while M-protein is only found in fast fibers. These proteins are thought to be involved in anchoring the thick
Myomesin
11430779
Stress fiber Stress fibers are contractile actin bundles found in non-muscle cells. They are composed of actin (microfilaments) and non-muscle myosin II (NMMII), and also contain various crosslinking proteins, such as α-actinin, to form a highly regulated actomyosin structure within non-muscle cells. Stress fibers have been shown to play an important role in cellular contractility, providing force for a number of functions such as cell adhesion, migration and morphogenesis. Stress fibers are primarily composed of actin and myosin. Actin is a ~43kDa globular protein, and can polymerize to form long filamentous structures.These filaments are made of two strands of actin
Stress fiber
11430765
Stress fiber Stress fibers are contractile actin bundles found in non-muscle cells. They are composed of actin (microfilaments) and non-muscle myosin II (NMMII), and also contain various crosslinking proteins, such as α-actinin, to form a highly regulated actomyosin structure within non-muscle cells. Stress fibers have been shown to play an important role in cellular contractility, providing force for a number of functions such as cell adhesion, migration and morphogenesis. Stress fibers are primarily composed of actin and myosin. Actin is a ~43kDa globular protein, and can polymerize to form long filamentous structures.These filaments are made of two strands of actin
Stress fiber
5311467
to be determined. There is some research indicating that satellite cells are negatively regulated by a protein called myostatin. Increased levels of myostatin up-regulate a cyclin-dependent kinase inhibitor called p21 and thereby inhibit the differentiation of satellite cells. Myosatellite cell Myosatellite cells or satellite cells are small multipotent cells with virtually no cytoplasm found in mature muscle. Satellite cells are precursors to skeletal muscle cells, able to give rise to satellite cells or differentiated skeletal muscle cells. They have the potential to provide additional myonuclei to their parent muscle fiber, or return to a quiescent state. More specifically, upon activation,
Myosatellite cell
5311454
Myosatellite cell Myosatellite cells or satellite cells are small multipotent cells with virtually no cytoplasm found in mature muscle. Satellite cells are precursors to skeletal muscle cells, able to give rise to satellite cells or differentiated skeletal muscle cells. They have the potential to provide additional myonuclei to their parent muscle fiber, or return to a quiescent state. More specifically, upon activation, satellite cells can re-enter the cell cycle to proliferate and differentiate into myoblasts. Myosatellite cells are located between the basement membrane and the sarcolemma of muscle fibers, and can lie in grooves either parallel or transversely to the
Myosatellite cell
13036776
skMLCK. An image depicting a similar complex (sdCen/skMLCK2) is shown under myosin light chain kinase. This binding to skMLCK increases the affinity of Ca2+ and ultimately leads to a sustained muscle action. Mutations in the "MYLK2" gene have been linked to midventricular hypertrophic cardiomyopathy. MYLK2 Myosin light chain kinase 2 also known as MYLK2 is an enzyme which in humans is encoded by the "MYLK2" gene. This gene encodes a myosin light chain kinase, a calcium / calmodulin dependent enzyme, that is exclusively expressed in adult skeletal muscle. The MYLK2 gene expresses skMLCK more prevalently in fast twitch muscle fibers
MYLK2
6332471
in the process of cell division. For example, non-muscle myosin II bipolar thick filaments provide the force of contraction needed to divide cell into two daughter cells during cytokinesis.In addition to myosin II, many other myosin types are responsible for variety of movement of non-muscle cells. For example, myosin is involved in intracellular organization and the protrusion of actin-rich structures at the cell surface. Myosin V is involved in vesicle and organelle transport. Myosin XI are involved in cytoplasmic streaming, wherein movement along microfilament networks in the cell allows organelles and cytoplasm to stream in a particular direction. Eighteen different
Motor protein
11232246
change must be undone to relax the muscle. When myosin phosphatase binds to myosin, it removes the phosphate group. Without the group, the myosin reverts to its original conformation, in which it cannot interact with the actin and hold the muscle tense, so the muscle relaxes. The muscle will remain in this relaxed position until myosin is phosphorylated by MLC kinase and undergoes a conformational change. Myosin phosphatase is made of three subunits. The catalytic subunit, PP1, is one of the more important Ser/Thr phosphatases in eukaryotic cells, as it plays a role in glycogen metabolism, intracellular transport, protein synthesis,
Myosin-light-chain phosphatase
12561031
muscles of vertebrates and the muscles of spiralians these cells derive from the ectodermal mesoderm rather than the endodermal mesoderm. Furthermore, Schmid and Seipel argue that since myogenesis does occur in cnidarians with the help of molecular regulatory elements found in the specification of muscles cells in bilaterians that there is evidence for a single origin for striated muscle. In contrast to this argument for a single origin of muscle cells, Steinmetz et al. argue that molecular markers such as the myosin II protein used to determine this single origin of striated muscle actually predate the formation of muscle cells.
Muscle
11232243
Myosin-light-chain phosphatase Myosin light-chain phosphatase, more commonly called myosin phosphatase (), is an enzyme (specifically a serine/threonine-specific protein phosphatase) that dephosphorylates the regulatory light chain of myosin II. This dephosphorylation reaction occurs in smooth muscle tissue and initiates the relaxation process of the muscle cells. Thus, myosin phosphatase undoes the muscle contraction process initiated by myosin light-chain kinase. The enzyme is composed of three subunits: the catalytic region (protein phosphatase 1, or PP1), the myosin binding subunit (MYPT1), and a third subunit (M20) of unknown function. The catalytic region uses two manganese ions as catalysts to dephosphorylate the light-chains on
Myosin-light-chain phosphatase
20146466
the organ level blebbistatin stops the contraction of skeletal muscle or heart muscle. Blebbistatin has also been found to stabilize the super relaxed state in the myofilaments, where myosin heads are in a helical order and interact with each other but not with actin. A number of physicochemical deficiencies hamper the use of blebbistatin as a chemical tool in particular applications. Upon blue light illumination, blebbistatin becomes inactive and phototoxic due to changes in the structure of the compound accompanied by the generation of ROS Blebbistatin is a relatively strong fluorophore, it absorbs around 430 nm and emits around 560
Blebbistatin
1451783
store roughly 100–120 grams of glycogen. In skeletal muscle, glycogen is found in a low concentration (1–2% of the muscle mass) and the skeletal muscle of an adult weighing 70 kg stores roughly 400 grams of glycogen. The amount of glycogen stored in the body—particularly within the muscles and liver—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells, white blood cells, and glial cells in the brain. The uterus also stores glycogen during pregnancy to nourish the embryo. Approximately 4
Glycogen
2345157
leads to the movement of tropomyosin, subsequently exposing the myosin-binding sites on actin. This allows for myosin and actin ATP-dependent cross-bridge cycling and shortening of the muscle. Muscle force is proportional to physiologic cross-sectional area (PCSA), and muscle velocity is proportional to muscle fiber length. The torque around a joint, however, is determined by a number of biomechanical parameters, including the distance between muscle insertions and pivot points, muscle size and Architectural gear ratio. Muscles are normally arranged in opposition so that when one group of muscles contracts, another group relaxes or lengthens. Antagonism in the transmission of nerve impulses
Skeletal muscle
1296305
on voltage-sensitive membrane channels, which are responsible for the functioning of animal nervous systems. Quite separately, he developed the mathematical equations for the operation of myosin "cross-bridges" that generate the sliding forces between actin and myosin filaments, which cause the contraction of skeletal muscles. These equations presented an entirely new paradigm for understanding muscle contraction, which has been extended to provide understanding of almost all of the movements produced by cells above the level of bacteria. Together with the Swiss physiologist Robert Stämpfli, he evidenced the existence of saltatory conduction in myelinated nerve fibres. Huxley, Alan Hodgkin and John Eccles
Andrew Huxley
3897195
has been shown that the substrate binding step (transaldimination) drives the catalytic reaction forward. AST is similar to alanine transaminase (ALT) in that both enzymes are associated with liver parenchymal cells. The difference is that ALT is found predominantly in the liver, with clinically negligible quantities found in the kidneys, heart, and skeletal muscle, while AST is found in the liver, heart (cardiac muscle), skeletal muscle, kidneys, brain, and red blood cells. As a result, ALT is a more specific indicator of liver inflammation than AST, as AST may be elevated also in diseases affecting other organs, such as myocardial
Aspartate transaminase
10082168
membrane. Three isoforms of CPT1 exist in mammalian tissues. The liver isoform (CPT1A or CPTI-L) is found throughout the body on the mitochondria of all cells except for skeletal muscle cells and brown adipose cells. The muscle isoform (CPT1B or CPTI-M) is highly expressed in heart and skeletal muscle cells and brown adipose cells. A third isoform, the brain isoform (CPT1C), was isolated in 2002. It is expressed predominantly in the brain and testes. Little is known about CPT1C. The exact structure of any of the CPT1 isoforms has not yet been determined, although a variety of "in silico" models
Carnitine palmitoyltransferase I
10493416
J. DMV, and Susan E. Hakola DMV. Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse Vol. II. Equistar Publication, Limited. Marysville, OH. Copyright 2000. Muscular system of the horse There are 3 types of muscle, all found within the equine: Skeletal muscle is made up of several muscle bundles, which in turn are made up of muscle fibers. Muscle fibers have bundles of myofibrils, which are all parallel to one another, and are able to contract due to actin and myosin. Muscle is covered by a fibrous tissue called fascia, to which other muscles can attach,
Muscular system of the horse
10493414
Muscular system of the horse There are 3 types of muscle, all found within the equine: Skeletal muscle is made up of several muscle bundles, which in turn are made up of muscle fibers. Muscle fibers have bundles of myofibrils, which are all parallel to one another, and are able to contract due to actin and myosin. Muscle is covered by a fibrous tissue called fascia, to which other muscles can attach, and muscles attach to bone via tendons. Tendons attach muscles and bone, and are classified as flexors (flex a joint) or extensors (extend a joint). However, some tendons
Muscular system of the horse
2674973
as a person with longer legs can move farther with each individual step. The velocity of a myosin motor depends upon the rate at which it passes through a complete kinetic cycle of ATP binding to the release of ADP. Myosin I, a ubiquitous cellular protein, functions as monomer and functions in vesicle transport. It has step size of 10 nm and has been implicated as being responsible for the adaptation response of the stereocilia in the inner ear. Myosin II (also known as conventional myosin) is the myosin type responsible for producing muscle contraction in muscle cells. In muscle
Myosin
12560990
three types of muscle, skeletal or striated, cardiac, and smooth. Muscle action can be classified as being either voluntary or involuntary. Cardiac and smooth muscles contract without conscious thought and are termed involuntary, whereas the skeletal muscles contract upon command. Skeletal muscles in turn can be divided into fast and slow twitch fibers. Muscles are predominantly powered by the oxidation of fats and carbohydrates, but anaerobic chemical reactions are also used, particularly by fast twitch fibers. These chemical reactions produce adenosine triphosphate (ATP) molecules that are used to power the movement of the myosin heads. The term muscle is derived
Muscle
7345229
muscle cells. One possible candidate for this inhibitory factor is GATA-6 The increase in telokin expression correlated with an increase in the expression of several other smooth muscle-restricted proteins, including smooth muscle myosin and alpha-actin. Accumulates in individuals with asthma (at protein levels). Induced by tumor necrosis factor (TNF). Repressed by androgens (e.g. R1881). Telokin have two related functions in the C-terminal myosin-binding domain of smooth muscle myosin light chain kinase (MLCK). First, telokin stabilizes myosin filaments in the presence of ATP. Second, telokin can modulate the level of myosin light chain phosphorylation. In this latter role, multiple mechanisms have
Telokin
11307166
muscle. The approximate stoichiometry of cMyBP-C along the thick filament is 1 per 9-10 myosin molecules, or 37 cMyBP-C molecules per thick filament. In addition to myosin, cMyBP-C also binds titin and actin. The cMyBP-C isoform expressed in cardiac muscle differs from those expressed in slow and fast skeletal muscle (MYBPC1 and MYBPC2, respectively) by three features: (1) an additional immunoglobulin (Ig)-like domain on the N-terminus, (2) a linker region between the second and third Ig domains, and (3) an additional loop in the sixth Ig domain. cMyBP-C appears necessary for normal order, filament length and lattice spacing within the
Myosin binding protein C, cardiac
2674968
domain. Multiple myosin II molecules generate force in skeletal muscle through a power stroke mechanism fuelled by the energy released from ATP hydrolysis. The power stroke occurs at the release of phosphate from the myosin molecule after the ATP hydrolysis while myosin is tightly bound to actin. The effect of this release is a conformational change in the molecule that pulls against the actin. The release of the ADP molecule leads to the so-called rigor state of myosin. The binding of a new ATP molecule will release myosin from actin. ATP hydrolysis within the myosin will cause it to bind
Myosin
20814696
atoms (calcium ions); these channels are known as calcium-activated chloride channels. The mechanism for this calcium activation is unclear. Anoctamin proteins are also involved in maintaining the membrane that surrounds cells and repairing the membrane if damaged. The anoctamin-5 protein is most abundant in muscles used for movement (skeletal muscles). For the body to move normally, skeletal muscles must tense (contract) and relax in a coordinated way. The regulation of chloride flow within muscle cells plays a role in controlling muscle contraction and relaxation. The anoctamin-5 protein is also found in other cells including heart (cardiac) muscle cells and bone
ANO5
2345144
Skeletal muscle Skeletal muscle is one of three major muscle types, the others being cardiac muscle and smooth muscle. It is a form of striated muscle tissue, which is under the voluntary control of the somatic nervous system. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons. A skeletal muscle refers to multiple bundles (fascicles) of cells joined together called muscle fibers. The fibres and muscles are surrounded by connective tissue layers called fasciae. Muscle fibres, or muscle cells, are formed from the fusion of developmental myoblasts in a process known as myogenesis. Muscle
Skeletal muscle
20008746
into the cell. Secondly Ca indirectly activates proteins, called myofilaments, resulting in muscle contraction. The two main myofilaments in cardiac (and skeletal) muscle are actin and myosin. Ca binds to a protein called troponin, which is bound to the actin filament. This binding causes a shape change in the troponin which exposes areas on the actin, to which the head of the myosin filament binds. The binding of the myosin head to actin is known as a cross-bridge. A molecule, called adenosine triphosphate (ATP) which is produced by an intracellular structure called a mitochondrion, is then used, as a source
Cardiac excitation-contraction coupling
11323898
II subfamily of proteins, which also includes skeletal muscle, cardiac muscle and smooth muscle myosins. NM-IIB, and non-muscle myosins in general, are widely expressed in every tissue in humans. NM-IIB has many properties that are similar to those of smooth muscle myosins, such as the permissive nature of phosphorylation of the 20 kDa regulatory light chain for contraction. In skeletal muscle and cardiac muscle myosins, contraction is activated through thin filament proteins troponin and tropomyosin, whereas in NM-IIB and smooth muscle myosin, contraction initiates via regulatory light chain (MLC20) phosphorylation. Various functions of NM-IIB require the phosphorylation of the regulatory
MYH10
2047066
to another site on the actin filament a further distance (10–12 nm) away. They can then re-bind to the actin molecule and drag it along further. This process is called crossbridge cycling and is the same for all muscles (see muscle contraction). Unlike cardiac and skeletal muscle, smooth muscle does not contain the calcium-binding protein troponin. Contraction is initiated by a calcium-regulated phosphorylation of myosin, rather than a calcium-activated troponin system. Crossbridge cycling causes contraction of myosin and actin complexes, in turn causing increased tension along the entire chains of tensile structures, ultimately resulting in contraction of the entire smooth
Smooth muscle
10704124
subgroups: the single-unit (unitary) and multiunit smooth muscle. Within single-unit cells, the whole bundle or sheet contracts as a syncytium (i.e. a multinucleate mass of cytoplasm that is not separated into cells). Multiunit smooth muscle tissues innervate individual cells; as such, they allow for fine control and gradual responses, much like motor unit recruitment in skeletal muscle. Smooth muscle is found within the walls of blood vessels (such smooth muscle specifically being termed vascular smooth muscle) such as in the tunica media layer of large (aorta) and small arteries, arterioles and veins. Smooth muscle is also found in lymphatic vessels,
Muscle tissue
2483895
and myosin filaments themselves do not change length, but instead slide past each other. This is known as the sliding filament theory of muscle contraction. Myofibril A myofibril (also known as a muscle fibril) is a basic rod-like unit of a muscle cell. Muscles are composed of tubular cells called myocytes, known as muscle fibers in striated muscle, and these cells in turn contain many chains of myofibrils. They are created during embryonic development in a process known as myogenesis. Myofibrils are composed of long proteins including actin, myosin, and titin, and other proteins that hold them together. These proteins
Myofibril
13036775
MYLK2 Myosin light chain kinase 2 also known as MYLK2 is an enzyme which in humans is encoded by the "MYLK2" gene. This gene encodes a myosin light chain kinase, a calcium / calmodulin dependent enzyme, that is exclusively expressed in adult skeletal muscle. The MYLK2 gene expresses skMLCK more prevalently in fast twitch muscle fibers as compared to slow twitch muscle fibers. Calmodulin is composed of two terminal domains (N,C) each containing two E-F hand motifs that bind to Ca2+. Upon saturation of Ca2+, Calmodulin undergoes a conformation change allowing it to bind with a target protein such as
MYLK2
7628555
the somites. To form skeletal muscle in central body segments, PAX3-expressing cells detach from the dermomyotome and then Pax3 expression is turned off as Myf5 and MyoD1 expression is activated. To form other skeletal muscles, Pax3-expressing cells detach from the dermomyotome and migrate to more distant sites, such as the limbs and diaphragm. A subset of these Pax3-expressing dermomyotome-derived cells also serves as an ongoing progenitor pool for skeletal muscle growth during fetal development. During later developmental stages, myogenic precursors expressing Pax3 and/or Pax7 form satellite cells within the skeletal muscle, which contribute to postnatal muscle growth and muscle regeneration.
PAX3
12561043
Muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis. Muscle tissues are derived from the mesodermal layer of embryonic germ cells in a process known as myogenesis. There are
Muscle
12560989
Muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis. Muscle tissues are derived from the mesodermal layer of embryonic germ cells in a process known as myogenesis. There are
Muscle
2345146
perimysium, and enclosing each muscle fiber is a layer of connective tissue called the endomysium. Muscle fibres are the individual contractile units within muscle. A single muscle such as the biceps brachii contains many muscle fibres. Another group of cells, the myosatellite cells are found between the basement membrane and the sarcolemma of muscle fibers. These cells are normally quiescent but can be activated by exercise or pathology to provide additional myonuclei for muscle growth or repair. Individual muscle fibers are formed during development from the fusion of several undifferentiated immature cells known as myoblasts into long, cylindrical, multi-nucleated cells.
Skeletal muscle
2981925
vivo "and" in vitro". Individual subunits serve different functions: Smooth muscle does not have troponin. TnT is a tropomyosin-binding subunit which regulates the interaction of troponin complex with thin filaments; TnI inhibits ATP-ase activity of acto-myosin; TnC is a Ca-binding subunit, playing the main role in Ca dependent regulation of muscle contraction. TnT and TnI in cardiac muscle are presented by forms different from those in skeletal muscles. Two isoforms of TnI and two isoforms of TnT are expressed in human skeletal muscle tissue (skTnI and skTnT). Only one tissue-specific isoform of TnI is described for cardiac muscle tissue (cTnI),
Troponin
2047057
part of this reorganization consists of vimentin being phosphorylated at Ser by a p21 activated kinase, resulting in some disassembly of vimentin polymers. Also, the number of myosin filaments is dynamic between the relaxed and contracted state in some tissues as the ratio of actin to myosin changes, and the length and number of myosin filaments change. Smooth muscle cells have been observed contracting in a spiral corkscrew fashion, and contractile proteins have been observed organizing into zones of actin and myosin along the axis of the cell. Smooth muscle-containing tissue needs to be stretched often, so elasticity is an
Smooth muscle
6171729
MYH7 MYH7 is a gene encoding a myosin heavy chain beta (MHC-β) isoform (slow twitch) expressed primarily in the heart, but also in skeletal muscles (type I fibers). This isoform is distinct from the fast isoform of cardiac myosin heavy chain, MYH6, referred to as MHC-α. MHC-β is the major protein comprising the thick filament in cardiac muscle and plays a major role in cardiac muscle contraction. MHC-β is a 223 kDa protein composed of 1935 amino acids. MHC-β is a hexameric, asymmetric motor forming the bulk of the thick filament in cardiac muscle. MHC-β is composed of N-terminal globular
MYH7
11184641
family of small GTPases. Substrates for this enzyme include myogenin, the beta-subunit of the L-type calcium channels, and phospholemman. Although the specific function of this protein is unknown, it appears to play an important role in muscle, heart, and brain cells. This protein may be involved in communication within cells. It also appears to regulate the production and function of important structures inside muscle cells by interacting with other proteins. For example, myotonic dystrophy protein kinase has been shown to turn off (inhibit) part of a muscle protein called myosin phosphatase. Myosin phosphatase is an enzyme that plays a role
Myotonin-protein kinase
11353665
is a major contractile protein that converts chemical energy into mechanical energy through the hydrolysis of ATP. Class II Myosins are hexameric proteins composed of a pair of myosin heavy chains (MYH) and two pairs of nonidentical light chains. Myosin heavy chains are encoded by a multigene family. In mammals, at least ten different myosin heavy chain (MYH) isoforms have been described from striated, smooth, but rarely in non-muscle cells. These isoforms show expression that is spatially and temporally regulated during development. MYH1 Myosin-1, also known as 'striated muscle myosin heavy chain 1', is a protein that in humans is
MYH1
11232244
myosin, which causes a conformational change in the myosin and relaxes the muscle. The enzyme is highly conserved and is found in all organisms’ smooth muscle tissue. While it is known that myosin phosphatase is regulated by rho-associated protein kinases, there is current debate about whether other molecules, such as arachidonic acid and cAMP, also regulate the enzyme. Smooth muscle tissue is mostly made of actin and myosin, two proteins that interact together to produce muscle contraction and relaxation. Myosin II, also known as conventional myosin, has two heavy chains that consist of the head and tail domains and four
Myosin-light-chain phosphatase
9373183
the binding sites covered by the troponin-tropomyosin complex on the actin myofilament and allowing the myosin cross-bridges to connect with the actin. Triad (anatomy) In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally. (This property holds because T tubules run perpendicular to the longitudinal axis of the muscle fiber.) In mammals, triads are typically located at the A-I junction; that is, the
Triad (anatomy)
11141397
CLCN1 Chloride channel protein, skeletal muscle (CLCN1) is a protein that in humans is encoded by the "CLCN1" gene. Mutations in this protein cause congenital myotonia. CLCN1 is critical for the normal function of skeletal muscle cells. For the body to move normally, skeletal muscles must tense (contract) and relax in a coordinated way. Muscle contraction and relaxation are controlled by the flow of ions into and out of muscle cells. CLCN1 forms an ion channel that controls the flow of negatively charged chloride ions into these cells. The main function of this channel is to stabilize the cells' electrical
CLCN1
8974341
Actinin Actinin is a microfilament protein. α-Actinin is necessary for the attachment of actin filaments to the Z-lines in skeletal muscle cells, and to the dense bodies in smooth muscle cells. The functional protein is an anti-parallel dimer, which cross-links the thin filaments in adjacent sarcomeres, and therefore coordinates contractions between sarcomeres in the horizontal axis. The non-sarcomeric α-actinins, encoded by ACTN1 and ACTN4, are widely expressed. ACTN2 expression is found in both cardiac and skeletal muscle, whereas ACTN3 is limited to the latter. Both ends of the rod-shaped α-actinin dimer contain actin-binding domains. Mutations in ACTN4 can cause the
Actinin
8974342
kidney disease focal segmental glomerulosclerosis (FSGS). Actinin Actinin is a microfilament protein. α-Actinin is necessary for the attachment of actin filaments to the Z-lines in skeletal muscle cells, and to the dense bodies in smooth muscle cells. The functional protein is an anti-parallel dimer, which cross-links the thin filaments in adjacent sarcomeres, and therefore coordinates contractions between sarcomeres in the horizontal axis. The non-sarcomeric α-actinins, encoded by ACTN1 and ACTN4, are widely expressed. ACTN2 expression is found in both cardiac and skeletal muscle, whereas ACTN3 is limited to the latter. Both ends of the rod-shaped α-actinin dimer contain actin-binding domains.
Actinin
1349362
isoforms generates the forces in the cell that lead to signaling of early commitment markers. Nonmuscle myosin IIa generates the least force increasing to non-muscle myosin IIc. There are also factors in the cell that inhibit non-muscle myosin II, such as blebbistatin. This makes the cell effectively blind to the surrounding matrix. Researchers have obtained some success in inducing stem cell-like properties in HEK 239 cells by providing a soft matrix without the use of diffusing factors. The stem-cell properties appear to be linked to tension in the cells' actin network. One identified mechanism for matrix-induced differentiation is tension-induced proteins,
Cellular differentiation
11280558
Actinin alpha 3 Alpha-actinin-3, also known as alpha-actinin skeletal muscle isoform 3 or F-actin cross-linking protein, is a protein that in humans is encoded by the "ACTN3" gene. Alpha-actinin is an actin-binding protein with multiple roles in different cell types. This gene expression is limited to skeletal muscle. It is localized to the Z-disc and analogous dense bodies, where it helps to anchor the myofibrillar actin filaments. Skeletal muscle is composed of long cylindrical cells called muscle fibers. There are two types of muscle fibers, slow twitch or muscle contraction (type I) and fast twitch (type II). Slow twitch fibers
Actinin alpha 3
9737684
and pulmonary embolus. Troponin I Troponin I is a cardiac and skeletal muscle protein useful in the laboratory diagnosis of heart attack. It occurs in different plasma concentration but the same circumstances as troponin T - either test can be performed for confirmation of cardiac muscle damage and laboratories usually offer one test or the other. Troponin I is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place. Because of it, myosin cannot bind actin in relaxed muscle. When calcium binds to the troponin C it causes
Troponin I
9737680
Troponin I Troponin I is a cardiac and skeletal muscle protein useful in the laboratory diagnosis of heart attack. It occurs in different plasma concentration but the same circumstances as troponin T - either test can be performed for confirmation of cardiac muscle damage and laboratories usually offer one test or the other. Troponin I is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place. Because of it, myosin cannot bind actin in relaxed muscle. When calcium binds to the troponin C it causes conformational changes which
Troponin I
11354846
TRIM63 E3 ubiquitin-protein ligase TRIM63 is an enzyme that in humans is encoded by the "TRIM63" gene. The protein encoded by the Trim63 gene is also called MuRF1. MuRF1 is the name most commonly used in the literature, and it stands for "Muscle RING Finger 1." Structurally, there are two closely related MuRFs, MuRF2 and MuRF3. These also have TRIM codes: MuRF2 is TRIM55; MuRF3 is TRIM54. Trim63/MuRF1 has been shown to be an E3 ubiquitin ligase. It's major substrate is Myosin Heavy Chain. MuRF1 is upregulated during skeletal muscle atrophy - and thus the degradation of myosin heavy chain,
TRIM63
7345224
Telokin Telokin (also known as kinase-related protein or KRP) is an abundant protein found in smooth-muscle. It is identical to the C-terminus of myosin light-chain kinase. Telokin may play a role in the stabilization of unphosphorylated smooth-muscle myosin filaments. Because of its origin as the C-terminal end of smooth muscle myosin light chain kinase, it is called "telokin" (from a combination of the Greek telos, "end" and kinase). Telokin's systematic name is ATP:[myosin light chain] O-phosphotransferase and its recommended name is myosin-light-chain. (). The gene "MYLK", a muscle member of the immunoglobulin gene superfamily, encodes myosin light chain kinase which
Telokin
5331481
spermatocytes is described as the 'Stem Cell Renewal Theory'" . This article is the first one in which nests of cells dividing in an adult organ are designated as "stem cells". Leblond and his colleagues also found evidence for the presence of occasional adult stem cells even in tissues which are composed almost entirely of non-dividing cells. In skeletal muscle, the muscle fibers had been shown to exhibit an age-related increase in the number of nuclei. His studies showed that muscle satellite cells could be considered to be adult stem cells in muscle fibers. From the studies of Leblond and
Charles Philippe Leblond
2915075
skeletal muscle fibers form by the fusion of thousands of individual muscle cells. The multinucleated (symplastic) arrangement is important in pathologic states such as myopathy, where focal necrosis (death) of a portion of a skeletal muscle fibers does not result in necrosis of the adjacent sections of that same skeletal muscle fiber, because those adjacent sections have their own nuclear material. Thus, myopathy is usually associated with such "segmental necrosis", but with some of the surviving segments being functionally cut off from their nerve supply via loss of continuity with the neuromuscular junction. The syncytium of cardiac muscle is important
Syncytium
11323667
in the sarcomeric thin filaments of cardiac and skeletal muscles: troponin C, troponin T, tropomyosin and actin. When cytosolic Ca is low, TnI binds the thin filament to block the myosin binding sites on actin. The rise of cytosolic Ca results in binding to the N-terminal domain of troponin C and induces conformational changes in troponin C and the troponin complex, which releases the inhibition of myosin-actin interaction and activates myosin ATPase and cross bridge cycling to generate myosin power strokes and muscle contraction. To date, no high resolution structure of ssTnI has been solved. As homologous proteins, ssTnI, fast
TNNI1
10299099
Therefore, growth of adult cardiac cells is commonly characterized by hypertrophy and an increased content of contractile proteins. However, studies have shown NRG-1 promotes myocardial regeneration through hyperplasia, and prevents hypertrophy surrounding infarcted areas. The cMLCK protein is an important regulator of sarcomere assembly through activation of the myosin regulatory light chain, as well as playing a role in heart contractility. In contrast to smooth and skeletal muscle MLCKs, cMLCK expression is restricted to cardiac myocytes. Overexpression of cMLCK increases cell contractility. Treatment of cardiac myocytes with rhNRG-1 significantly upregulated cMLCK expression or activity??? in CHF rat models, together with
Neuregulin 1
11778354
target in human, Calmodulin and Myosin light-chain kinase 2 found in skeletal and cardiac muscle. Pharmacologically, it decreases the sympathetic stimulation on cardiac muscle predominantly through partial depletion of catecholamine via competitive inhibition of reuptake by storage granule, which lead to further depletion due to spontaneous leakage as a result of disturbance of equilibrium. This depletion mechanism is similar to reserpine because both agents target the same site on storage granule, however prenylamine shows a high affinity for cardiac tissue while reserpine is more selective toward brain tissue. Prenylamine also slows cardiac metabolism via calcium transport delay by blockade of
Prenylamine
2483892
7:1 ratio of thin to thick filaments. Along the long axis of the muscle cells in subsarcolemmal locations, free myofilaments become aligned and aggregate into hexagonally packed arrays. These aggregates form regardless of the presence of Z band or M band material. Aggregation occurs spontaneously because the tertiary structures of actin and myosin monomers contain all the "information" with the ionic strength and ATP concentration of the cell to aggregate into the filaments. The myosin heads form cross bridges with the actin myofilaments; this is where they carry out a 'rowing' action along the actin. When the muscle fibre is
Myofibril
11389033
on how TRIM32 induces differentiation involve the ubiquitination of the transcription factor c-Myc and the binding of Argonaute-1 (Ago-1). The binding of Ago-1 induces activity of miRNAs, particularly Let-7a, which has been shown to play a role in regulating proliferation and neuronal differentiation. TRIM32 is expressed in skeletal muscle, where it interacts with myosin and may ubiquitinate actin (it has been shown to do so in vitro). No difference has been observed between wild-type and LHMD2H-mutated TRIM32 in terms of actin or myosin binding, however, and thus the mechanism which causes the muscular dystrophy, LGMD2H, is still unknown. Additionally, TRIM32
TRIM32