Catalytic domain of the Protein Tyrosine Kinase, Platelet Derived Growth Factor Receptor beta
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. PDGFR beta 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 beta forms homodimers or heterodimers with PDGFR alpha, depending on the nature of the PDGF ligand. PDGF-BB and PDGF-DD induce PDGFR beta homodimerization. PDGFR signaling plays many roles in normal embryonic development and adult physiology. PDGFR beta signaling leads to a variety of cellular effects including the stimulation of cell growth and chemotaxis, as well as the inhibition of apoptosis and GAP junctional communication. It is critical in normal angiogenesis as it is involved in the recruitment of pericytes and smooth muscle cells essential for vessel stability. Aberrant PDGFR beta expression is associated with some human cancers. The continuously-active fusion proteins of PDGFR beta with COL1A1 and TEL are associated with dermatofibrosarcoma protuberans (DFSP) and a subset of chronic myelomonocytic leukemia (CMML), respectively. The PDGFR beta 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.