Platelet-derived growth factor receptor beta (PDGFRB), also known as CD140b, together with the structurally homolog protein PDGFRA (CD140a) are members of the class III subfamily of receptor tyrosine kinases (RTK) that also includes the receptors for M-CSF, SCF, and Flt-3 ligand. All class III RTKs are characterized by the presence of five immunoglobulin-like domains in their extracellular region and a kinase domain in their intracellular region.
PDGF is a major serum mitogen that can exist as a homo or hetero-dimeric protein consisting of disulfide-linked PDGF-A and PDGF-B chains. The PDGF-AA, PDGF‑BB, and PDGF‑AB isoforms have been shown to bind to PDGFRA and PDGFRB with different affinities. PDGFRA binds all three PDGF isoforms with high affinity, whereas PDGFRB binds PDGF-BB only with high-affinity. PDGF binding induces receptor homo-and hetero-dimerization and signal transduction. The expression of PDGFRA and PDGFRB are independently regulated in various cell types. Recombinant soluble PDGFRB binds PDGF with high affinity and is potent PDGF antagonist.