Role of αβ receptor heterodimer formation in β platelet-derived growth factor (PDGF) receptor activation by PDGF-AB

We investigated the ability of highly purified recombinant platelet-derived growth factor (PDGF) AB to interact with the products of α and β receptor genes expressed in cells independently or concurrently. Although PDGF-AB lacked any detectable ability to bind or activate β receptors in cells expressing only this receptor, efficient β receptor activation by this ligand was readily observed in cells coexpressing α platelet-derived growth factor receptors (αPDGFRs). β receptor activation induced by PDGF-AB was shown to be dependent upon in vivo physical association of this receptor with αPDGFRs. Moreover, cross-linking analysis established the existence of PDGF-AB-induced βPDGFR dimers in vivo. All of these findings argue that initial PDGF-AB interaction with the αPDGFR induces conformational changes in the ligand or receptor that facilitates efficient recruitment of βPDGFR by this PDGF isoform.