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Myostatin (GDF-8), a member of the TGFbeta superfamily, is a potent and specific negative regulator of skeletal muscle mass. In serum, myostatin circulates as part of a latent complex containing myostatin propeptide and/or follistatin-related gene. The myostatin propeptide is known to bind and inhibit myostatin in vitro. This interaction is relevant in vivo, with a majority (>70%) of myostatin in serum bound to its propeptide. The myostatin propeptide is negative regulator of myostatin in vivo.

GDF8 is a member of the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. This group of proteins is characterized by a polybasic proteolytic processing site which is cleaved to produce a mature protein containing seven conserved cysteine residues. The members of this family are regulators of cell growth and differentiation in both embryonic and adult tissues. This gene is thought to encode a secreted protein which negatively regulates skeletal muscle growth.

GDF8 is a member of the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. This group of proteins is characterized by a polybasic proteolytic processing site which is cleaved to produce a mature protein containing seven conserved cysteine residues. The members of this family are regulators of cell growth and differentiation in both embryonic and adult tissues. This gene is thought to encode a secreted protein which negatively regulates skeletal muscle growth.

GDF8 is a member of the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. This group of proteins is characterized by a polybasic proteolytic processing site which is cleaved to produce a mature protein containing seven conserved cysteine residues. The members of this family are regulators of cell growth and differentiation in both embryonic and adult tissues. This gene is thought to encode a secreted protein which negatively regulates skeletal muscle growth.

Myostatin (GDF-8) is expressed uniquely in human skeletal muscle as a 12 kDa mature glycoprotein consisting of 113 amino acid residues and secreted into plasma. Myostatin is a member of the transforming growth factor ? superfamily of secreted growth and differentiation factors that is essential for proper regulation of skeletal muscle mass. Studies have shown that myostatin could play an important role in cardiac development and physiology.

GDF8 is a member of the bone morphogenetic protein (BMP) family and the TGF-beta superfamily. This group of proteins is characterized by a polybasic proteolytic processing site which is cleaved to produce a mature protein containing seven conserved cysteine residues. The members of this family are regulators of cell growth and differentiation in both embryonic and adult tissues. This gene is thought to encode a secreted protein which negatively regulates skeletal muscle growth.

Myozenin 1 (MYOZ1) is a member of the myozenin family. MYOZ1 is mostly expressed in the skeletal muscle. Members of the myozenin family act as calcineurin-interacting proteins which helps tether calcineurin to the sarcomere of cardiac and skeletal muscle. The myozenin family plays a significant role in modulation of calcineurin signaling.

Myosin is a hexameric ATPase cellular motor protein, which is composed of 2 heavy chains, 2 non-phosphorylatable alkali light chains, and 2 phosphorylatable regulatory light chains.
MYL1 gene encodes a myosin alkali light chain expressed in fast skeletal muscle. Two transcript variants have been identified for the MYL1 gene. In humans MYL1 is localized to chromosome 2q32.1-qter. The Myl1 locus encodes two alkali myosin light chains- Mlc1f and Mlc3f, from two promoters that are differentially regulated throughout development. The Mlc1f promoter is active in embryonic, fetal and adult fast skeletal muscle while the Mlc3f promoter is upregulated during fetal development and stays on in adult fast skeletal muscle.

Myosin regulatory light chains, including MRCL3, MYLPF and MYL9, regulate contraction in smooth muscle and non-muscle cells via phosphorylation by MLCK (myosin light chain kinase). Phosphorylation of myosin regulatory light chains, catalyzed by MLCK in the presence of calcium and calmodulin, increases the actin-activated myosin ATPase activity, thus regulating the contractile activity. MYLPF is vital for fast and slow skeletal muscle development.

Sclerostin (SOST) is a secreted glycoprotein with a C-terminal cysteine knot-like (CTCK) domain and sequence similarity to the DAN (differential screening-selected gene aberrative in neuroblastoma) family of bone morphogenetic protein antagonists. Sclerostin functions as a negative regulator of bone growth, by inhibiting bone formation. SOST is expressed mainly in the bone, cartilage, kidney, liver, bone marrow and primary osteoblasts differentiated for 21 days. SOST gene defects cause sclerosteosis and bone dysplasia.

Somatostatin (also known as growth hormone inhibiting hormone (GHIH) or somatotropin release-inhibiting hormone (SRIF) is a peptide hormone that regulates the endocrine systemand affects neurotransmission and cell proliferation via interaction with G-protein-coupled somatostatin receptors and inhibition of the release of numerous secondary hormones. Somatostatin has two active forms produced by alternative cleavage of a single preproprotein: one of 14 amino acids, the other of 28 amino acids.

Non muscle Myosins are required for cytokinesis at the end of cell division, when a contractile ring near the plasmalemma divides the cytoplasm of the daughter cells. They are involved in cytoplasmic streaming movements in tissues, and especially in activation of motile cells such as fibroblasts and macrophages. Activation of non-muscle myosin-II is achieved by phosphorylation of Ser33 in the motif KKRPQRATSN by a dedicated, Ca +2 Calmodulin regulated light chain kinase (MLCK).

There are several proteolytic fragments or specific domains of proteins that act as inhibitors of angiogenesis. These include fragments of plasminogen such as Angiostatin protein kringles 1-4 and kringles 1-5, Endostatin, Restin, PEX, the N-terminal fragment of prolactin, and the Nterminally truncated platelet factor. Angiostatin is a proteolytic protein fragment of plasminogen that is comprised of the first 4 kringle regions. Angiostatin k1-4 prevents the growth of endothelial cells, and its systemic administration inhibits the growth of primary carcinomas in mice. Angiostatin Kringles 1-3 segment has a larger inhibitory activity than the Angiostatin kringles 1-4 fragment. The protease-activated angiostatin kringles 1-5 is the most potent plasminogen fragment with over 50 times larger endothelial cell specific inhibitory activity. Angiostatin kringles 1-5 systemic administration inhibits growth of fibrosarcoma and significantly reduces neovascularization.
Angiostatin is an angiogenesis inhibitor in mouse serum and urine. Angiostatin is a 38 kDa protein fragment of the plasminogen composed of the 1st 4 kringle domains of plasminogen. Angiostatin K1-4 is also named plasminogen kringles 1-4 and PK1-4.
Angiostatin protein is manufactured by the protelytic cleavage of plasminogen by a serine protease from several prostate carcinoma cell lines. The manufacturing of angiostatin by pancreatic cancer cells can be inhibited by TGF-beta 1 along with plasminogen activator inhibitor type-1 (PAI1).

Oncostatin M is a member of a cytokine family that includes leukemia-inhibitory factor, granulocyte colony-stimulating factor, and interleukin 6. This gene encodes a growth regulator which inhibits the proliferation of a number of tumor cell lines. It regulates cytokine production, including IL-6, G-CSF and GM-CSF from endothelial cells.

Myosin Binding Protein C, Cardiac (MYBPC3) is the cardiac isoform of myosin-binding protein C expressed exclusively in heart muscle. Myosin-binding protein C is a myosin-associated protein found in the cross-bridge-bearing zone (C region) of A bands in striated muscle. Regulatory phosphorylation of the cardiac isoform in vivo by cAMP-dependent protein kinase upon adrenergic stimulation may be associated with modulation of cardiac contraction. MYBPC3 gene mutations are one of the causes of familial hypertrophic cardiomyopathy. In vitro MYBPC3 binds MHC, F-actin and native thin filaments, and modifies the activity of actin-activated myosin ATPase. MYBPC3 may modulate muscle contraction or it may have a more structural role.

Follistatin is a single-chain gonadal protein that specifically inhibits follicle-stimulating hormone release. The single FST gene encodes two isoforms, FST317 and FST344 containing 317 and 344 amino acids respectively, resulting from alternative splicing of the precursor mRNA. In a study in which 37 candidate genes were tested for linkage and association with polycystic ovary syndrome (PCOS) or hyperandrogenemia in 150 families, evidence was found for linkage between PCOS and follistatin. Follistatin functions as an ACTV antagonist. specific inhibitor of the biosynthesis and secretion of pituitary follicle stimulating hormone (fsh).

Troponin I, (TNNI1) is a member of the troponin I family. Troponin complex has 3 subunits, TNNI1 known as the inhibitory Subunit which prevents the actin-myosin interactions and thus mediating striated muscle relaxation. TNNI1 combines with tropomyosin and regulates calcium sensitivity of striated muscles by structural modifications in actin-myosin complexes.

Troponin I, fast skeletal muscle (TNNI2), belongs to the troponin I gene family, and a part of the troponin complex including troponin T, troponin C and troponin I subunits. The troponin complex, along with tropomyosin, is responsible for the calcium-dependent regulation of striated muscle contraction. TNNI2 is also suppresses tumor growth in human ovarian carcinoma. Mutations in TNNI2 cause myopathy and distal arthrogryposis type 2B.

Troponin is a fundamental regulatory protein of striated muscle contraction, and together with tropomyosin, is positioned on the actin filament. Troponin has 3 subunits: TnI- the inhibitor of actomyosin ATPase; TnT- contains the binding site for tropomyosin; and TnC- the protein encoded by the TNNC1 gene. The binding of calcium to TnC stops the inhibitory action of TnI, consequently allowing the interaction of actin with myosin, the hydrolysis of ATP, and the generation of tension. Mutations in the TNNC1 gene are linked to cardiomyopathy dilated type 1Z.

Troponin-C2 (Troponin C, skeletal muscle) is the central regulatory antigen of striated muscle contraction, and modulates the Ca2+-activation characteristics of muscle fibers. Troponin-C2 has three subunits, Troponin I(Tn-1), Troponin T(Tn-T) and Troponin C(Tn-C). Tn-I subunit inhibits actomyosin ATPase and Tn-T subunit binds tropomyosin and Tn-C, while Tn-C subunit binds calcium and overcomes the inhibitory action of the troponin complex on actin filaments. Mutations in all components of this complex have been linked with skeletal muscle disease.

TNNT2 is the tropomyosin-binding subunit of the troponin complex, which is situated on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration. Mutations in TNNT2 gene are related with familial hypertrophic cardiomyopathy as well as with dilated cardiomyopathy. TNNT2 mutation takes part in hypertrophic cardiomyopathy.

Myosin is composed of 2 nonphosphorylatable alkali light chains, 2 heavy chains and 2 phosphorylatable regulatory light chains. MYL12B is a hexameric ATPase cellular motor protein which controls contraction in smooth muscle and non-muscle cells through phosphorylation by myosin light chain kinase (MLCK). Phosphorylation of myosin regulatory light chains catalyzed by MLCK in the presence of calcium and calmodulin, rises Actin-activated myosin ATPase activity, thus regulating contractile activity.

Follistatin is a single-chain gonadal protein that specifically inhibits follicle-stimulating hormone release. The single FST gene encodes two isoforms, FST317 and FST344 containing 317 and 344 amino acids respectively, resulting from alternative splicing of the precursor mRNA. In a study in which 37 candidate genes were tested for linkage and association with polycystic ovary syndrome (PCOS) or hyperandrogenemia in 150 families, evidence was found for linkage between PCOS and follistatin. Follistatin binds directly to activin and functions as an activin antagonist. specific inhibitor of the biosynthesis and secretion of pituitary follicle stimulating hormone (fsh).