"AbFrontier"

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Selenoprotein-P(SelP) is the major selenoprotein in human blood plasma and a transport protein which is carrying selenium to various extrahepatic tissues. Though its expression is detected in most tissues, highest amounts are produced by the liver, which secretes highly glycosylated SelP into plasma. Purification of human SelP yields two distinct isoforms with 61 and 55 kDa, differing in selenium content. SelP also has been shown to chelate heavy metals such as cadmium and mercury, and there are several evidences about its serum antioxidant capacity and protection against oxidative stress. Selenium deficiency predispose to several pathological condition such as cancer, coronary heart disease and liver necrosis although the biological function of SelP in various pathologic conditions has not been established.

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Cyclin-dependent kinase-5(CDK5) is a member of the cyclin-dependent kinase family of serine/threonine kinases. Its mRNA and protein are expressed in the kidneys, testes, and ovaries. And Its activity has been detected almost exclusively in brain extracts.
Similar to other Cdks, monomeric Cdk5 displays no enzymatic activity; however, Cdk5 is not activated by cyclins. Instead, Cdk5 activity requires association with one of two brain-specific regulatory subunits, called p35 and p39. These two activators regulate the spatial and temporal expression of active Cdk5, restricting its activity primarily to post-mitotic neurons.

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Catalase is a homotetrameric heme-containing enzyme present within the matrix of all peroxisomes. It carries out a dismutation reaction in which hydrogen peroxide is converted to water and oxygen. Human catalase has the last four amino acids (-KANL) at the extreme C-terminus for peroxisome targeting. The monomer of human catalase is 61.3 kD in molecular size. Catalase has been implicated as an important factor in inflammation, mutagenesis, prevention of apoptosis, and stimulation of a wide spectrum of tumors. Loss of catalase leads to the human genetic disease, acatalasemia, or Takahara’s disease (1).

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Platelet-derived growth factors (PDGFs) have been implicated in the control of cell proliferation, survival and migration. The PDGF family of growth factors consists of five different disulphide-linked dimers built up of four different polypeptide chains encoded by four different genes. Theses isoforms, PDGF-AA, PDGF-AB, PDGF-BB, PDGF-CC and PDGF-DD, act via two receptor tyrosine kinases, PDGF receptors α and β. Thus far, gene-targeting experiments have been attempted to create knockout mice deficient for PDGFR-α or PDGFR-β. Those mice, however, died either at the embryonic stage or several days after birth. Platelet-derived growth factor receptors, PDGFR-α and PDGFR-β, have five extracellular immunoglobulin-like domains and an intracellular tyrosine kinase domain. Upon binding a PDGF, the receptors form homo- and heterodimers. Dimerization of the receptors juxtaposes the intracellular part of the receptors, which allow phosphorylation in trans between the two receptors in the complex. These autophosphorylation provide docking sites for downstream signal transduction molecules. More than 10 different SH2–domain-containing molecules have been shown to bind to different autophosphorylation sites in the PDGF α- and β-receptors. There are signal transduction molecules with enzymatic activity, such as PI3-kinase, PLC-γ, Src, SHP-2, GAP, as well as adaptor molecules such as Grb2, Shc, Nck, Grb7 and Crk, and Stats. Each of the different partners recruited by the activated receptor initiates different signaling pathways, making possible a great variety of cellular response.

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Anti-PTPRM Mouse Monoclonal Antibody [clone: T5-AF1A8]

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Attractin is a serum glycoprotein of 175 kDa and found in both membrane-bound and secreted forms as a result of alternative splicing. Both the secreted and membrane-bound forms of attractin may be involved in the development and maintenance of the central nervous system. Membrane-bound attractin is a co-receptor for Agouti, antagonist of melanocortin-1 receptor. Secreted attractin, expressed by activated T lymphocytes and modulates interactions between T cells and monocytes/macrophages, was examined as a potential marker of immune activity. Attractin may be a component of a pathway for regulated protein turnover that also involves mahogunin, a wide-expressed E3 ubiquitin ligase found at particularly high levels in the brain. Attractin was considered as an extracellular target amenable for the development of obesity-regulating drugs, also.

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Vimentin is a member of the intermediate filament family of proteins found in various non-epithelial cells, especially mesenchymal cells. Vimentin is responsible for maintaining cell shape, integrity of the cytoplasm, and stabilizing cytoskeletal interactions. Vimentin plays a significant role in supporting and anchoring the position of the organelles in the cytosol. Although most intermediate filaments are stable structures, vimentin also has a dynamic nature which is important when offering flexibility to the cell.
Two monomers which have central α-helical domains, capped on each end by non-helical domains twist around each other to form a coiled-coil dimer. Two dimers then form a tetramer, which, in turn, form a sheet by interacting with other tetramers.
There are some reports related to the biochemical function of intermediate filament network. The intracellular movement of LDL-derived cholesterol from the lysosome to the site of esterification is a vimentin-dependent process. A role for vimentin in mechanotransduction of shear stress has also been suggested. The mechanical stress of fluid shear on endothelial cells seems to trigger MAPK signaling pathways and stimulates proliferation.

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PTEN acts as a phosphatase to dephosphorylate phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5)P3). The product of this enzymatic reaction is PtdIns(4,5)P2. This dephosphorylation is important because it results in inhibition of the AKT signaling pathway.
PTEN is a 403 amino acid protein, and a member of the large PTP (protein tyrosine phosphatase) family. PTEN crystal structure revealed that the N-terminal phosphatase domain is followed by a tightly associated C-terminal C2 domain. These two domains together form a minimal catalytic unit. The phosphatase domain contains the active site which carries out the enzymatic function of the protein, whilst the C2 domain allows PTEN to bind to the phospholipid membrane.
PTEN is one of the most commonly lost tumour suppressors in human cancer, and its deregulation is also implicated in several other diseases. Hereditary mutation of PTEN causes tumor-susceptibility diseases such as Cowden disease.

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IA-2 (insulinoma-associated protein 2, ICA512, PTPRN) is a member of the transmembrane protein tyrosine phosphatase (PTP) family located in secretory granules of neuroendocrine cells. The IA-2 protein is 979 amino acids in length and consists of a luminal domain, transmembrane domain, and cytoplasmic domain. Although a member of the PTP family, IA-2 lacks phosphatase activity with known substrates due to amino acid substitutions at critical sites in its PTP domain. Two paralog RPTPs, IA-2 and IA-2β were identified as major autoantigens in type-1 diabetes mellitus. On granule exocytosis, the IA-2 cytoplasmic domain is cleaved and the resulting cytosolic fragment moves into the nucleus where it enhances the levels of phosphorylated STAT5 and STAT3, thereby inducing insulin gene transcription and granule biogenesis. IA-2 signaling enhances pancreatic β–cell proliferation by regulating cyclins D through STATs.

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Fibronectin (FN) exists in two main forms: 1) as a soluble glycoprotein in blood plasma (plasma FN), and 2) as an insoluble glycoprotein in tissue extracellular matrices (cellular FN). Many different cell types synthesize fibronectin and secrete it as a disulfide-bonded dimer composed of 230–270 kDa subunits. FN is one of the largest multi-domain proteins that interact with a variety of macromolecules like heparin, collagen /gelatin, and fibrin. FN is involved in many cellular processes, including tissue repair, embryogenesis, blood clotting, and cell migration/ adhesion and so can be used as a therapeutic agent for wound healing. In addition, its age-dependent increase in plasma and tissues may be accompanied in pathological states, especially in tumor growth, by its proteolytic breakdown.

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The Smad family of proteins are functioning in the transmission of extracellular signals in the TGF-β signaling pathway. Binding of a TGF-β superfamily ligands to extracellular receptors triggers phosphorylation of Smad2 at a Serine-Serine-Methionine-Serine (SSMS) motif at its C-terminus. Phosphorylated Smad2 is then able to form a complex with Smad4. These complexes accumulate in the cell nucleus, where they are directly participating in the regulation of gene expression.
In mammals, eight Smad proteins have been identified to date. The Smad family of proteins can be divided into three functional groups: the receptor-activated Smads (R-Smads), common mediator Smads (Co-Smads), and the inhibitory Smads (I-Smads). The R-Smads are directly phosphorylated by the activated type I receptors on their C-terminal Ser-Ser-X-Ser (SSXS) motif and include Smad1, Smad2, Smad3, Smad5, and Smad8. Smad2 and Smad3 are phosphorylated in response to TGF-β and activin, whereas Smad1, Smad5, and Smad8 are phosphorylated in response to BMP (Bone Morphogenetic Protein). This C-terminal phosphorylation allows R-Smad binding to Co-Smad, Smad4, and translocation to the nucleus where they regulate TGF-β target genes. Smad6 and Smad7 belong to the I-Smad which bind to the type I receptor or Smad4 and block their interaction with R-Smads.

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Focal adhesion kinase subfamily consists of the non-receptor proline-rich protein tyrosine kinases (PTKs). Two members of the family are focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2). These two kinases have molecular mass between 110-125 kDa and are closely related in their structure. The presence of two proline-rich motifs within the C-terminal domains is conserved.
FAK is a nonreceptor and nonmembrane associated PTK which does not contain Src homology 2 (SH2) or SH3 protein interaction domains. The centrally located kinase domain of FAK is flanked by large N- and C-terminal noncatalytic domains.
FAK links integrin receptors to intracellular signaling pathways that are important for cell growth, survival, and migration. Integrin receptor engagement with ligands such as fibronectin can stimulate FAK autophosphorylation which enables FAK to function within a network of integrin-stimulated signaling pathways leading to the activation of targets such as the ERK and JNK/mitogen-activated protein kinase pathways. Recent study reveals that FAK is essential for angiogenesis in the embryo, functions in heart development and modulates the response of cardiomyocytes to pressure overload in adult mice.

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Vimentin is a member of the intermediate filament family of proteins found in various non-epithelial cells, especially mesenchymal cells. Vimentin is responsible for maintaining cell shape, integrity of the cytoplasm, and stabilizing cytoskeletal interactions. Vimentin plays a significant role in supporting and anchoring the position of the organelles in the cytosol. Although most intermediate filaments are stable structures, vimentin also has a dynamic nature which is important when offering flexibility to the cell.
Two monomers which have central α-helical domains, capped on each end by non-helical domains twist around each other to form a coiled-coil dimer. Two dimers then form a tetramer, which, in turn, form a sheet by interacting with other tetramers.
There are some reports related to the biochemical function of intermediate filament network. The intracellular movement of LDL-derived cholesterol from the lysosome to the site of esterification is a vimentin-dependent process. A role for vimentin in mechanotransduction of shear stress has also been suggested. The mechanical stress of fluid shear on endothelial cells seems to trigger MAPK signaling pathways and stimulates proliferation.

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Protein kinase C (PKC) is a family of serine-threonine kinases that regulate a broad spectrum of cellular functions. The family is composed of nine genes that express structurally related phospholipid-dependent kinases with distinct means of regulation and tissue distribution. Based on their structures and sensitivities to Ca2+ and diacylglycerol (DAG), they have been classified into conventional PKCs (alpha, beta, and gamma), novel PKCs (Delta, Epsilon, Eta, and IPA), and atypical PKCs (Zeta and Lambda/Iota). PKC Gamma is a member of the cPKC subfamily which is activated by Ca2+ and diacylglycerol in the presence of phosphatidylserine. Physiologically, PKC Gamma is activated by a mechanism coupled with receptor-mediated breakdown of inositol phospholipid as other cPKC isotypes. PKC Gamma is expressed solely in the brain and spinal cord and its localization is restricted to neurons. Within the brain, PKC Gamma is the most abundant in the cerebellum, hippocampus and cerebral cortex, where the existence of neuronal plasticity has been demonstrated.

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The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase of the ErbB (also known as HER) family in which four members have been identified: EGFR (ErbB1), HER2/Neu (ErbB2), HER3 (ErbB3), and HER4 (ErbB4). All four erbB receptors are composed of an extracellular ligand-binding region consisting of glycosylated domains, a transmembrane domain containing a single hydrophobic anchor sequence, an intracellular region containing the catalytic tyrosine kinase domain, and a carboxyl-terminal region containing several tyrosine residues that become phosphorylated after receptor activation.
The epidermal growth factor receptor (EGFR) signaling pathway is one of the most important pathways that regulate growth, survival, proliferation, and differentiation in mammalian cells. EGFR and other members of the erbB family form either homodimers or heterodimers upon ligand binding, resulting in conformational changes that allow activation of protein kinases and transphosphorylation of key tyrosine residues within the carboxyl-terminal domain. After the induction of tyrosine phosphorylation, some signaling pathways appear to start with the recognition of the C-terminal phosphotyrosines by appropriate adaptor or signaling molecules. The aberrant activation of the EGFR leads to enhanced proliferation and other tumor-promoting activities. Several mechanisms lead to aberrant receptor activation, including receptor overexpression, gene amplification, activating mutations, overexpression of receptor ligands, and/or loss of their negative regulatory mechanisms.
The epidermal growth factor receptor (EGFR) has been extensively investigated as a target for anti-neoplastic therapy. Anti-EGFR antibodies that interfere with ligand-dependent receptor activation have shown clinical activity in a variety of solid tumors.

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Peroxiredoxin (Prx) is a growing peroxidase family, whose mammalian members have been known to connect with cell proliferation, differentiation, and apoptosis.
Many isoforms (about 50 proteins), collected in accordance to the amino acid sequence homology, particularly amino-terminal region containing active site cysteine residue, and the thiol-specific antioxidant activity, distribute throughout all the kingdoms. Among them, mammalian Prx consists of 6 different members grouped into typical 2-Cys, atypical 2-Cys Prx, and 1-Cys Prx. Except Prx VI belonging to 1-Cys Prx subgroup, the other five 2-Cys Prx isotypes have the thioredoxin-dependent peroxidase (TPx) activity utilizing thioredoxin, thioredoxin reductase, and NADPH as a reducing system. Mammalian Prxs are 20 – 30 kilodalton in molecular size and vary in subcellular localization: Prx I, II, and VI in cytosol, Prx III in mitochondria, Prx IV in ER and secretion, Prx V showing complicated distribution including peroxisome, mitochondria and cytosol (1).