==Crystal structure of the extracellular domain of Kit in complex with stem cell factor (SCF)==

<StructureSection load='2e9w' size='340' side='right' caption='[[2e9w]], [[Resolution|resolution]] 3.50&Aring;' scene=''>

<table><tr><td colspan='2'>[[2e9w]] is a 4 chain structure with sequence from [http://en.wikipedia.org/wiki/Human Human]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2E9W OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2E9W FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=2e9w FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2e9w OCA], [http://pdbe.org/2e9w PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=2e9w RCSB], [http://www.ebi.ac.uk/pdbsum/2e9w PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=2e9w ProSAT]</span></td></tr>

== Disease ==

[[http://www.uniprot.org/uniprot/KIT_HUMAN KIT_HUMAN]] Defects in KIT are a cause of piebald trait (PBT) [MIM:[http://omim.org/entry/172800 172800]]; also known as piebaldism. PBT is an autosomal dominant genetic developmental abnormality of pigmentation characterized by congenital patches of white skin and hair that lack melanocytes.<ref>PMID:1376329</ref> <ref>PMID:1370874</ref> <ref>PMID:1717985</ref> <ref>PMID:7687267</ref> <ref>PMID:8680409</ref> <ref>PMID:9029028</ref> <ref>PMID:9450866</ref> <ref>PMID:9699740</ref> <ref>PMID:11074500</ref> Defects in KIT are a cause of gastrointestinal stromal tumor (GIST) [MIM:[http://omim.org/entry/606764 606764]].<ref>PMID:9029028</ref> <ref>PMID:9697690</ref> <ref>PMID:9438854</ref> <ref>PMID:11505412</ref> <ref>PMID:15824741</ref> Defects in KIT have been associated with testicular germ cell tumor (TGCT) [MIM:[http://omim.org/entry/273300 273300]]. A common solid malignancy in males. Germ cell tumors of the testis constitute 95% of all testicular neoplasms.<ref>PMID:9029028</ref> Defects in KIT are a cause of acute myelogenous leukemia (AML) [MIM:[http://omim.org/entry/601626 601626]]. AML is a malignant disease in which hematopoietic precursors are arrested in an early stage of development. Note=Somatic mutations that lead to constitutive activation of KIT are detected in AML patients. These mutations fall into two classes, the most common being in-frame internal tandem duplications of variable length in the juxtamembrane region that disrupt the normal regulation of the kinase activity. Likewise, point mutations in the kinase domain can result in a constitutively activated kinase.<ref>PMID:9029028</ref> [[http://www.uniprot.org/uniprot/SCF_HUMAN SCF_HUMAN]] Defects in KITLG are the cause of familial progressive hyperpigmentation (FPH) [MIM:[http://omim.org/entry/145250 145250]]; also called melanosis universalis hereditaria (MUH). FPH is an autosomal-dominantly inherited disorder characterized by hyperpigmented patches in the skin, present in early infancy and increasing in size and number with age.<ref>PMID:19375057</ref>

== Function ==

[[http://www.uniprot.org/uniprot/KIT_HUMAN KIT_HUMAN]] 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. Phosphorylates PIK3R1, PLCG1, SH2B2/APS and CBL. 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. 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. Promotes phosphorylation of PIK3R1, CBL, CRK (isoform Crk-II), LYN, MAPK1/ERK2 and/or MAPK3/ERK1, PLCG1, SRC and SHC1.<ref>PMID:7520444</ref> <ref>PMID:9528781</ref> <ref>PMID:10397721</ref> <ref>PMID:12444928</ref> <ref>PMID:12878163</ref> <ref>PMID:12511554</ref> <ref>PMID:17904548</ref> <ref>PMID:19265199</ref> <ref>PMID:21640708</ref> <ref>PMID:21135090</ref> [[http://www.uniprot.org/uniprot/SCF_HUMAN SCF_HUMAN]] Ligand for the receptor-type protein-tyrosine kinase KIT. 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. KITLG/SCF binding can activate several signaling pathways. Promotes phosphorylation of PIK3R1, the regulatory subunit of phosphatidylinositol 3-kinase, and subsequent activation of the kinase AKT1. KITLG/SCF and KIT also transmit signals via GRB2 and activation of RAS, RAF1 and the MAP kinases MAPK1/ERK2 and/or MAPK3/ERK1. KITLG/SCF and KIT promote activation of STAT family members STAT1, STAT3 and STAT5. KITLG/SCF and KIT promote activation of PLCG1, leading to the production of the cellular signaling molecules diacylglycerol and inositol 1,4,5-trisphosphate. KITLG/SCF acts synergistically with other cytokines, probably interleukins.

<div style="background-color:#fffaf0;">

== Publication Abstract from PubMed ==

Stem Cell Factor (SCF) initiates its multiple cellular responses by binding to the ectodomain of KIT, resulting in tyrosine kinase activation. We describe the crystal structure of the entire ectodomain of KIT before and after SCF stimulation. The structures show that KIT dimerization is driven by SCF binding whose sole role is to bring two KIT molecules together. Receptor dimerization is followed by conformational changes that enable lateral interactions between membrane proximal Ig-like domains D4 and D5 of two KIT molecules. Experiments with cultured cells show that KIT activation is compromised by point mutations in amino acids critical for D4-D4 interaction. Moreover, a variety of oncogenic mutations are mapped to the D5-D5 interface. Since key hallmarks of KIT structures, ligand-induced receptor dimerization, and the critical residues in the D4-D4 interface, are conserved in other receptors, the mechanism of KIT stimulation unveiled in this report may apply for other receptor activation.

Structural basis for activation of the receptor tyrosine kinase KIT by stem cell factor.,Yuzawa S, Opatowsky Y, Zhang Z, Mandiyan V, Lax I, Schlessinger J Cell. 2007 Jul 27;130(2):323-34. PMID:17662946<ref>PMID:17662946</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

</div>

<div class="pdbe-citations 2e9w" style="background-color:#fffaf0;"></div>

==See Also==

*[[SCF-KIT|SCF-KIT]]

*[[Tyrosine kinase|Tyrosine kinase]]

== References ==

<references/>

[[Category: Human]]

[[Category: Receptor protein-tyrosine kinase]]

[[Category: Zhang, Z]]

[[Category: Transferase-hormone complex]]