PLATELET-DERIVED GROWTH-FACTOR (PDGF)-AB-MEDIATED PHOSPHORYLATION OF PDGF BETA-RECEPTORS

Platelet-derived growth factor (PDGF) stimulates the proliferation of Balb/c-3T3 fibroblasts through binding and subsequent activation of PD GF receptors. Activation of the PDGF receptors has been proposed to in volve receptor dimerization. PDGF-AB has been shown to bind PDGF alpha and beta receptor subunits to form PDGF alpha beta and alpha alpha re ceptor dimers. In this paper we demonstrate that, following the down-r egulation of PDGF alpha receptors, the binding of PDGF-AB to beta rece ptors occurred at 37 degrees C but not at 4 degrees C. PDGF-AB stimula ted the phosphorylation of PDGF beta receptor monomers in cells deplet ed of PDGF alpha receptors by prior exposure to PDGF-AA.