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Background
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SCF-R/c-kit, also known as KIT, is a tyrosine-protein kinase that acts as cell-surface receptor for the cytokine KITLG/SCF and plays an essential role in the regulation of cell survival and proliferation, hematopoiesis, stem cell maintenance, gametogenesis, mast cell development, migration and function, and in melanogenesis. In response to KITLG/SCF binding, KIT can activate several signaling pathways. KIT phosphorylates PIK3R1, PLCG1, SH2B2/APS and CBL. KIT also activates the AKT1 signaling pathway by phosphorylation of PIK3R1, the regulatory subunit of phosphatidylinositol 3-kinase. Activated KIT also transmits signals via GRB2 and activation of RAS, RAF1 and the MAP kinases MAPK1/ERK2 and/or MAPK3/ERK1. The protein promotes activation of STAT family members STAT1, STAT3, STAT5A and STAT5B. Activation of PLCG1 leads to the production of the cellular signaling molecules diacylglycerol and inositol-1,4,5-trisphosphate. KIT signaling is modulated by protein phosphatases, and by rapid internalization and degradation of the receptor. Activated KIT promotes phosphorylation of the protein phosphatases PTPN6/SHP-1 and PTPRU, and of the transcription factors STAT1, STAT3, STAT5A and STAT5B. KIT promotes phosphorylation of PIK3R1, CBL, CRK (isoform Crk-II), LYN, MAPK1/ERK2 and/or MAPK3/ERK1, PLCG1, SRC and SHC1. Activity is down-regulated by PRKCA-mediated phosphorylation on serine residues. SCF R/c-kit is inhibited by imatinib/STI- 571 and sunitinib, these compounds maintain the kinase in an inactive conformation. In the absence of bound KITLG/SCF, KIT is a monomer and is a homodimer in the presence of bound KITLG/SCF, forming a heterotetramer with two KITLG/SCF molecules. KIT is widely expressed and detected in the hematopoietic system, the gastrointestinal system, in melanocytes and in germ cells. KIT is up-regulated by cis-retinoic acid in neuroblastoma cell lines and ubiquitinated by SOCS6. KIT is rapidly ubiquitinated after auto-phosphorylation induced by KITLG/SCF binding, leading to internalization and degradation. KITLG/SCF binding enhances auto-phosphorylation. Defects in KIT can lead to a variety of diseases, which include, but are not limited, to the following: Piebald trait (PBT), gastrointestinal stromal tumor (GIST), testicular tumors, acute myelogenous leukemia. Source: Entrez Gene, Swiss-Prot
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Pathways
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RTK Signaling, Fc-epsilon Receptor Signaling Pathway, EGFR Signaling Pathway, Neurotrophin Signaling Pathway, Sensory Perception of Sound, Stem Cell Maintenance, Production of Molecular Mediator of Immune Response, Regulation of long-term Neuronal Synaptic Plasticity
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