Catalytic domain of the Protein Tyrosine Kinase, Platelet Derived Growth Factor Receptor alpha
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. PDGFR alpha is a receptor PTK (RTK) containing an extracellular ligand-binding region with five immunoglobulin-like domains, a transmembrane segment, and an intracellular catalytic domain. The binding to its ligands, the PDGFs, leads to receptor dimerization, trans phosphorylation and activation, and intracellular signaling. PDGFR alpha forms homodimers or heterodimers with PDGFR beta, depending on the nature of the PDGF ligand. PDGF-AA, PDGF-AB, and PDGF-CC induce PDGFR alpha homodimerization. PDGFR signaling plays many roles in normal embryonic development and adult physiology. PDGFR alpha signaling is important in the formation of lung alveoli, intestinal villi, mesenchymal dermis, and hair follicles, as well as in the development of oligodendrocytes, retinal astrocytes, neural crest cells, and testicular cells. Aberrant PDGFR alpha expression is associated with some human cancers. Mutations in PDGFR alpha have been found within a subset of gastrointestinal stromal tumors (GISTs). An active fusion protein FIP1L1-PDGFR alpha, derived from interstitial deletion, is associated with idiopathic hypereosinophilic syndrome and chronic eosinophilic leukemia. The PDGFR alpha subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.