PDGF R beta is a transmembrane receptor tyrosine kinase (RTK) that primarily binds to the PDGF-BB isoform of the growth factor. Ligand binding induces receptor homodimerization or heterodimerization with PDGF R alpha followed by autophosphorylation and signal transduction. PDGF receptor signaling is attenuated by SHP-2 phosphatase activity and by receptor endocytosis and lysosomal degradation. The expression of the alpha and beta receptors is independently regulated in various cell types. A soluble splice variant of PDGF R beta binds PDGF with high affinity and functions as a potent PDGF antagonist.