CD140b is a cell surface tyrosine kinase receptor for members of the platelet-derived growth factor family. The identity of the growth factor bound to the receptor determines whether the functional receptor is a homodimer or heterodimer composed of both PDGFR-alpha and -beta. CD140b contains two immunoglobulin-like domains and a tyrosine kinase domain with a predicted molecular weight approximately 124 kD. CD140b is widely expressed on a variety of mesenchymal-derived cells and is preferentially expressed on some tumors such as medulloblastoma. Binding of B-chain containing PDGF molecules can stimulate cell proliferation. CD140b has been shown to interact with a number of kinases (including Raf-1, NCK1, FAK, Fyn, others) as well as adaptor molecules and signaling intermediates (Crk, Grb2, Grb4, RasGAP, SHP2, SHC1, others), and has also been shown to associate with integrin beta3 and nexin sorting molecules. CD140b has been implicated in several disease states including atherogenesis and oncogenesis. The PDGFRbeta is heavily phosphorylated on numerous tyrosine residues through both autophosphorylation and ligand-dependent processes.