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NTRK2 plays a role in the growth and the development of the central and the peripheral nervous systems using the regulation of neuron proliferation, migration, survival, differentiation, and synapse production. NTRK2 is a receptor for B-DNF and NT4. NTRK2 binds to neurotrophin-3 which regulates neuron survival through NTRK2. NTRK-2 activates numerous effectors such as SHC-1, SH2B-1, PLCG-1 and SH2B-2 that control overlapping signaling cascades.

Neurotrophic Receptor Tyrosine Kinase 3 (NTRK3)belongs to the receptor tyrosine kinases family and is a high affinity catalytic receptor of neurotrophin NT-3. NTRK3 mediates multiple effects of this neurotrophic factor, which includes neuronal differentiation and survival. NTRK3 inducesvarious pleiotorpic responses in malignant cells, including enhanced tumor cell invasiveness and chemotoxis.Increased NTRK3 expression was observed in neuroblastoma, medulloblastoma, and in neuroectodermal brain tumors.

All three VEGF receptors belong to the class III subfamily of receptor tyrosine kinases (RTKs) characterised by the seven immunoglobulin-like loops in the extracellular domain. The expression of VEGFR-1 to -3 is almost exclusively restricted to hematopoietic precursor cells, vascular and lymphatic endothelial cells and to the monocyte/macrophage lineage. They play key roles in vasculogenesis, hematopoiesis, angiogenesis and lymphangiogenesis. The FLT-4 cDNA encodes a 1298 amino acid (aa) residue precursor protein with a 23 aa residue signal peptide. Mature VEGFR-3/FLT-4 is composed of a 751 aa residue extracellular domain, a 22 aa transmembrane domain and a 482 aa residue cytoplasmic domain. Both VEGF family members VEGF-C and VEGF-D have been shown to bind and activate VEGFR-3/FLT-4. The Flt-4 gene is widely expressed in the early embryo but becomes restricted to the lymphatic endothelial a latter stages of development. It is important for lymphangiogenesis.

Serine/threonine-protein kinase 16 (STK16) is a membrane-associated protein kinase which phosphorylates on serine and threonine residues. STK16 is involved in secretory vesicle trafficking or intracellular signaling. Furthermore, the STK16 protein may have a role in regulating stromal-epithelial interactions which occur during ductal morphogenesis in the mammary gland. STK16 can autophosphorylate on Tyr residue; it is however unclear whether STK16 has tyrosine-protein kinase toward other proteins. STK16 may also be involved in TGF-beta signaling.

TSSK2 is a testis-specific serine/threonine-protein kinase required during spermatid development which phosphorylates TSKS at 'Ser-288' and SPAG16. TSSK2 takes part in the late stages of spermatogenesis, during the reconstruction of the cytoplasm. During spermatogenesis, TSSK2 is necessary for the transformation of a ring-shaped structure around the base of the flagellum originating from the chromatoid body.

TDP1 belongs to the phospholipase D family and contains two PLD phosphodiesterase domains. TDP1 is involved in repairing stalled topoisomerase I-DNA complexes by catalyzing the hydrolysis of the phosphodiester bond between the tyrosine residue of topoisomerase I and the 3-prime phosphate of DNA. TDP1 may also remove glycolate from single-stranded DNA containing 3-prime phosphoglycolate, suggesting a role in repair of free-radical mediated DNA double-strand breaks. Mutations in the TDP1 gene are linked to the disease spinocerebellar ataxia with axonal neuropathy (SCAN1).

The 14-3-3 family of proteins plays a key regulatory role in signal transduction, checkpoint control, apoptotic and nutrient-sensing pathways. 14-3-3 proteins are highly conserved and ubiquitously expressed. There are at least seven isoforms that have been identified in mammals. The 14-3-3gamma, a subtype of the 14-3-3 family of proteins, was thought to be brain and neuron-specific. It has been shown to interact with RAF1 and protein kinase C, proteins involved in various signal transduction pathways.

Thymidine kinase 2 mitochondrial (TK2) is a member of the DCK/DGK family. TK2 is an enzyme, a phosphotransferase (a kinase): 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase. Thymidine kinase is found in most living cells. Thymidine kinase is present in 2 forms in mammalian cells, TK1 and TK2. Thymidine kinases have a central function in the synthesis of DNA and thus in cell division, since they are part of the exceptional reaction chain to introduce deoxythymidine into the DNA. TK2 is a deoxyribonucleoside kinase which specifically phosphorylates thymidine, deoxycytidine, and deoxyuridine. TK2 localizes to the mitochondria and is essential for mitochondrial DNA synthesis. TK2 gene defects are a cause of mitochondrial DNA depletion syndrome type 2 (MTDPS2).

KIT, also known as KIT Proto-Oncogene Receptor Tyrosine, is a cytokine receptor which is expressed not only in hematopoietic stem cells but likewise in other cell types. KIT binds to receptor tyrosine kinase type III, which is a stem cell factor, also named a "rigid factor" or "c-kit ligand". Once this receptor binds to stem cell factor (SCF), it forms a dimer which activates intrinsic tyrosine kinase activity, which sequentially phosphorylates & activates signaling molecules which breed signals in cells. This receptor protects vascular smooth muscle cells from apoptosis in addition to restoring cardiac function after myocardial infarction.

TIE-1 (tyrosine kinase with Ig and EGF homology domains 1) and TIE-2/Tek comprise a receptor tyrosine kinase (RTK) subfamily with unique structural characteristics: two immunoglobulin-like domains flanking three epidermal growth factor (EGF)-like domains and followed by three fibronectin type III-like repeats in the extracellular region and a split tyrosine kinase domain in the cytoplasmic region. These receptors are expressed primarily on endothelial and hematopoietic progenitor cells and play critical roles in angiogenesis, vasculogenesis and hematopoiesis. Human TIE-1 cDNA encodes a 1122 amino acid (aa) residue precursor protein with an 18 residue putative signal peptide, a 726 residue extracellular domain and a 353 residue cytoplasmic domain. Two ligands, angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2), which bind TIE-2 with high-affinity have been identified. Ang2 has been reported to act as an antagonist for Ang1. Mice engineered to overexpress Ang2 or to lack Ang1 or Tie-1 display similar angiogenic defects.

Endothelial cells express three different vascular endothelial growth factor (VEGF) receptors, belonging to the family of receptor tyrosine kinases (RTKs). They are named VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1), VEGFR-3 (Flt-4). Their expression is almost exclusively restricted to endothelial cells, but VEGFR-1 can also be found on monocytes, dendritic cells and on trophoblast cells. The flt-1 gene was first described in 1990. The receptor contains seven immunoglobulin-like extracellular domains, a single transmembrane region and an intracellular splited tyrosine kinase domain. Compared to VEGFR-2 the Flt-1 receptor has a higher affinity for VEGF but a weaker signaling activity. VEGFR-1 thus leads not to proliferation of endothelial cells, but mediates signals for differentiation. Interestingly a naturally occuring soluble variant of VEGFR-1 (sVEGFR-1) was found in HUVE supernatants in 1996, which is generated by alternative splicing of the flt-1 mRNA. The biological functions of sVEGFR-1 still are not clear, but it seems to be an endogenous regulator of angiogenesis, binding VEGF with the same affinity as the full-length receptor.

Protein tyrosine phosphatase mitochondrial 1 (PTPMT1) is a broadly expressed PTP membrane protein with high expression levels in pancreatic beta cells. The PTPMT1 protein is completely restricted to the matrix face of the inner membrane of the mitochondrion. PTPMT1 is responsible for dephosphorylating mitochondrial proteins and thus has a major role in the production of ATP. PTPMT1 exhibits a specific preference for the lipid signaling molecule phosphatidylinositol 5-phosphate as substrate.

Endothelial cells express three different vascular endothelial growth factor (VEGF) receptors, belonging to the family of receptor tyrosine kinases (RTKs). They are named VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1), VEGFR-3 (Flt-4). Their expression is almost exclusively restricted to endothelial cells, but VEGFR-1 can also be found on monocytes. All VEGF-receptors have seven immunoglobulin-like extracellular domains, a single transmembrane region and an intracellular split tyrosine kinase domain. VEGFR-2 has a lower affinity for VEGF than the Flt-1 receptor, but a higher signaling activity. Mitogenic activity in endothelial cells is mainly mediated by VEGFR-2 leading to their proliferation.
Differential splicing of the flt-1 gene leads to the formation of a secreted, soluble variant of VEGFR-1 (sVEGFR-1). No naturally occuring, secreted forms of VEGFR-2 have so far been reported. The binding of VEGF165 to VEGFR-2 is dependent on heparin.

Endothelial cells express three different vascular endothelial growth factor (VEGF) receptors, belonging to the family of receptor tyrosine kinases (RTKs). They are named VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1), VEGFR-3 (Flt-4). Their expression is almost exclusively restricted to endothelial cells, but VEGFR-1 can also be found on monocytes, dendritic cells and on trophoblast cells. The flt-1 gene was first described in 1990. The receptor contains seven immunoglobulin-like extracellular domains, a single transmembrane region and an intracellular splited tyrosine kinase domain. Compared to VEGFR-2 the Flt-1 receptor has a higher affinity for VEGF but a weaker signaling activity. VEGFR-1 thus leads not to proliferation of endothelial cells, but mediates signals for differentiation. Interestingly a naturally occuring soluble variant of VEGFR-1 (sVEGFR-1) was found in HUVE supernatants in 1996, which is generated by alternative splicing of the flt-1 mRNA. The biological functions of sVEGFR-1 still are not clear, but it seems to be an endogenous regulator of angiogenesis, binding VEGF with the same affinity as the full-length receptor.

Protein Tyrosine Phosphatase Receptor Type C, also known as PTPRC, which is a vital regulator of T- and B-cell antigen receptor signaling, is also a part of the protein tyrosine phosphatase (PTP) family. PTPs are signaling molecules which regulate a variety of cellular processes including differentiation, cell growth, mitosis, and oncogenic transformation. PTPRC contains an extracellular domain, a single transmembrane segment and 2 tandem intracytoplasmic catalytic domains, and therefore is classified as a receptor type PTP.

Protein Tyrosine Phosphatase Non Receptor Type-4, also known asPTPN4 belongs to the protein tyrosine phosphatase, PTP family. PTPs are identified as signaling molecules which regulate a variety of cellular processes as well as cell growth, differentiation, mitotic cycle, and oncogenic transformation. PTPN4 is broadly expressed non-receptor protein tyrosine phosphatase. In addition, PTPN4 interacts with glutamate receptor delta 2 & epsilon, and affects glutamate receptors signaling and/or in regulation of their activities through tyrosine dephosphorylation.

EFNA1 belongs to the ephrin (EPH) family. The EPH subfamily is the biggest group of receptor protein kinases and they take part in vital nervous system function and development.

Thymidine Kinase 1 (TK1) is a phosphotransferase (a kinase): 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase. TK1 is present in 2 forms in mammalian cells, TK1 and TK2. Thymidine kinases hold a main function in the synthesis of DNA and thus in cell division, as they are part of the distinctive reaction chain to introduce deoxythymidine (present in the body fluids as a result of degradation of DNA from food and from dead cells) into the DNA. Thymidine kinase is necessary for the action of many antiviral drugs. Thymidine kinase is used to select hybridoma cell lines in production of monoclonal antibodies.

The epidermal growth factor receptor (EGF R) subfamily of receptor tyrosine kinases comprises four members: EGF R (also known as HER1, ErbB1 or ErbB), ErbB2 (Neu, HER-2), ErbB3 (HER-3), and ErbB4 (HER-4). All family members are type I transmembrane glycoprotein that has an extracellular domain which contains two cysteine-rich domains separated by a spacer region that is involved in ligand-binding, and a cytoplasmic domain which has a membrane-proximal tyrosine kinase domain and a C-terminal tail with multiple tyrosine autophosphorylation sites. The human EGF R gene encodes a 1210 amino acid (aa) residue precursor with a 24 aa putative signal peptide, a 621 aa extracellular domain, a 23 aa transmembrane domain, and a 542 aa cytoplasmic domain. EGF R has been shown to bind a subset of the EGF family ligands, including EGF, amphiregulin, TGF-a , betacellulin, epiregulin, heparin-binding EGF and neuregulin-2 in the absence of a co-receptor. Ligand binding induces EGF R homodimerization as well as heterdimerization with ErbB2, resulting in kinase activation, tyrosine phosphorylation and cell signaling. EGF R can also be recruited to form heterodimers with the ligand-activated ErbB3 or ErbB4. EGF R signaling has been shown to regulate multiple biological functions including cell proliferation, differentiation, motility and apoptosis. In addition, EGF R signaling has also been shown to play a role in carcinogenesis.

Mitogen-Activated Protein Kinase 6 (MAP2K6) is a part of the dual specificity protein kinase family. MAP2K6 phosphorylates and activates p38 MAP kinase in response to inflammatory cytokines or environmental stress. MAP2K6 is a vital component of the MAP kinase signal transduction pathway. MAP2K6 takes part in various cellular processes such as stress induced cell cycle arrest and apoptosis.

Fibroblast Growth Factors (FGFs) comprise a family of at least eighteen structurally realted proteins that are involved in a multitude of physiological and pathological cellular processes, including cell growth, differentation, angiogenesis, wound healing and tumorgenesis. The biological activities of the FGFs are mediated by a family if type I transmembrane tyrosine kinases which undergo dimerization and autophosphorylation after ligand binding. Four distinct genes encoding closely related FGF receptors, FGFR-1to -4 are known. Multiple forms of FGFR-1 to -3 are generated by alternative splicing of the mRNAs. A frequent splicing event involving FGFR-1 and -2 results in receptors containing all three Ig domains, referred to as the alpha isoform, or only IgII and IgIII, referred to as the ? isoform. Only the alpha isoform has been identified for FGFR-3 and FGFR-4. Additional splicing events for FGFR-1 to -3, involving the C-terminal half of the IgIII domain encoded by two mutually exclusive alternative exons, generate FGF receptors with alternative IgIII domains (IIIb and IIIc). A IIIa isoform which is a secreted FGF binding protein containing only the N-terminal half of the IgIII domain plus some intron sequences has also been reported for FGFR-1. Mutations in FGFR-1 to -3 have been found in patients with birth defects involving craniosynostosis.

Protein Tyrosine Phosphatase Type IVA Member 3 (PTP4A3) is a member of a small class of prenylated protein tyrosine phosphatases (PTPs) which remove phosphate modifications from tyrosine residues on proteins. PTP4A3 enhances cell proliferation, cell motility and invasive activity. PTP4A3 functions as a protein tyrosine phosphatase which stimulates progression from G1 into S phase during mitosis. PTP4A3 is mostly expressed in cardiomyocytes and skeletal muscle; it is also found in the pancreas.
PTP4A3 is always overexpressed in colon cancer metastasis. PTP4A3 is notably overexpressed in liver metastasis of colorectal cancer. High levels of PTP4A3 expression are linked to tumorigenesis and metastasis; therefore it is overexpressed in metastatic colorectal, ovarian, liver and skin cancers. PTP4A3 may be involved in the progression of cardiac hypertrophy by inhibiting intracellular calcium mobilization in response to angiotensin II. PTP4A3 is inhibited by sodium orthovanadate and peroxovanadium compounds.

PTPN6 is a member of the protein tyrosine phosphatase (PTP) family. PTPs are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, mitotic cycle, and oncogenic transformation. N-terminal part of this PTP contains two tandem Src homolog (SH2) domains, which act as protein phospho-tyrosine binding domains, and mediate the interaction of this PTP with its substrates. This PTP is expressed primarily in hematopoietic cells, and functions as an important regulator of multiple signaling pathways in hematopoietic cells. This PTP has been shown to interact with, and dephosphorylate a wide spectrum of phospho-proteins involved in hematopoietic cell signaling. Multiple alternatively spliced variants of this gene, which encode distinct isoforms, have been reported.