CD117

4U0I, 1PKG, 1T45, 1T46, 2E9W, 2EC8, 2VIF, 3G0E, 3G0F, 4HVS, 4K94, 4K9E, 4PGZ, 2IUH381516590ENSG00000157404ENSMUSG00000005672P10721P05532NM_000222NM_001093772NM_001122733NM_021099NP_000213NP_001087241NP_001116205NP_066922Mast/stem cell growth factor receptor (SCFR), also known as proto-oncogene c-Kit or tyrosine-protein kinase Kit or CD117, is a receptor tyrosine kinase protein that in humans is encoded by the KIT gene. Multiple transcript variants encoding different isoforms have been found for this gene.KIT was first described by the German biochemist Axel Ullrich in 1987 as the cellular homolog of the feline sarcoma viral oncogene v-kit.1pkg: Structure of a c-Kit Kinase Product Complex1t45: STRUCTURAL BASIS FOR THE AUTOINHIBITION AND STI-571 INHIBITION OF C-KIT TYROSINE KINASE1t46: STRUCTURAL BASIS FOR THE AUTOINHIBITION AND STI-571 INHIBITION OF C-KIT TYROSINE KINASE Mast/stem cell growth factor receptor (SCFR), also known as proto-oncogene c-Kit or tyrosine-protein kinase Kit or CD117, is a receptor tyrosine kinase protein that in humans is encoded by the KIT gene. Multiple transcript variants encoding different isoforms have been found for this gene.KIT was first described by the German biochemist Axel Ullrich in 1987 as the cellular homolog of the feline sarcoma viral oncogene v-kit. CD117 is a cytokine receptor expressed on the surface of hematopoietic stem cells as well as other cell types. Altered forms of this receptor may be associated with some types of cancer. CD117 is a receptor tyrosine kinase type III, which binds to stem cell factor (a substance that causes certain types of cells to grow), also known as 'steel factor' or 'c-kit ligand'. When this receptor binds to stem cell factor (SCF) it forms a dimer that activates its intrinsic tyrosine kinase activity, that in turn phosphorylates and activates signal transduction molecules that propagate the signal in the cell. After activation, the receptor is ubiquitinated to mark it for transport to a lysosome and eventual destruction. Signaling through CD117 plays a role in cell survival, proliferation, and differentiation. For instance, CD117 signaling is required for melanocyte survival, and it is also involved in haematopoiesis and gametogenesis. Like other members of the receptor tyrosine kinase III family, CD117 consists of an extracellular domain, a transmembrane domain, a juxtamembrane domain, and an intracellular tyrosine kinase domain. The extracellular domain is composed of five immunoglobulin-like domains, and the protein kinase domain is interrupted by a hydrophilic insert sequence of about 80 amino acids. The ligand stem cell factor binds via the second and third immmunoglobulin domains. Cluster of differentiation (CD) molecules are markers on the cell surface, as recognized by specific sets of antibodies, used to identify the cell type, stage of differentiation and activity of a cell. CD117 is an important cell surface marker used to identify certain types of hematopoietic (blood) progenitors in the bone marrow. To be specific, hematopoietic stem cells (HSC), multipotent progenitors (MPP), and common myeloid progenitors (CMP) express high levels of CD117. Common lymphoid progenitors (CLP) express low surface levels of CD117. CD117 also identifies the earliest thymocyte progenitors in the thymus—early T lineage progenitors (ETP/DN1) and DN2 thymocytes express high levels of c-Kit. It is also a marker for mouse prostate stem cells. In addition, mast cells, melanocytes in the skin, and interstitial cells of Cajal in the digestive tract express CD117. In humans, expression of c-kit in helper-like innate lymphoid cells (ILCs) which lack the expression of CRTH2 (CD294) is used to mark the ILC3 population. Hematopoietic progenitor cells are normally present in the blood at low levels. Mobilization is the process by which progenitors are made to migrate from the bone marrow into the bloodstream, thus increasing their numbers in the blood. Mobilization is used clinically as a source of hematopoietic stem cells for hematopoietic stem cell transplantation (HSCT). Signaling through CD117 has been implicated in mobilization. At the current time, G-CSF is the main drug used for mobilization; it indirectly activates CD117. Plerixafor (an antagonist of CXCR4-SDF1) in combination with G-CSF, is also being used for mobilization of hematopoietic progenitor cells. Direct CD117 agonists are currently being developed as mobilization agents. Activating mutations in this gene are associated with gastrointestinal stromal tumors, testicular seminoma, mast cell disease, melanoma, acute myeloid leukemia, while inactivating mutations are associated with the genetic defect piebaldism. CD117 is a proto-oncogene, meaning that overexpression or mutations of this protein can lead to cancer. Seminomas, a subtype of testicular germ cell tumors, frequently have activating mutations in exon 17 of CD117. In addition, the gene encoding CD117 is frequently overexpressed and amplified in this tumor type, most commonly occurring as a single gene amplicon. Mutations of CD117 have also been implicated in leukemia, a cancer of hematopoietic progenitors, melanoma, mast cell disease, and gastrointestinal stromal tumors (GISTs). The efficacy of imatinib (trade name Gleevec), a CD117 inhibitor, is determined by the mutation status of CD117: When the mutation has occurred in exon 11 (as is the case many times in GISTs), the tumors are responsive to imatinib. However, if the mutation occurs in exon 17 (as is often the case in seminomas and leukemias), the receptor is not inhibited by imatinib. In those cases other inhibitors such as dasatinib and nilotinib can be used. Researchers investigated the dynamic behavior of wild type and mutant D816H KIT receptor, and emphasized the extended A-loop (EAL) region (805-850) by conducting computational analysis. Their atomic investigation of mutant KIT receptor which emphasized on the EAL region provided a better insight into the understanding of the sunitinib resistance mechanism of the KIT receptor and could help to discover new therapeutics for KIT-based resistant tumor cells in GIST therapy. The preclinical agent, KTN0182A, is an anti-KIT, pyrrolobenzodiazepine (PBD)-containing antibody-drug conjugate which shows anti-tumor activity in vitro and in vivo against a range of tumor types.