Ligand-Induced Homo-and Hetero-Dimerization of Platelet-Derived Growth Factor α- and β-Receptors in Intact Cells

Abstract

Porcine aortic endothelial cells expressing platelet-derived growth factor (PDGF) α- or β-receptors after transfection of the corresponding cDNAs, were used to investigate whether PDGF receptor dimerization occurs in intact cells after ligand binding. Using three different methods—covalent cross-linking of ¹²⁵I-labeled ligand, cross-linking of metabolically labeled cells after ligand-binding followed by immunoprecipitation, and immunoblotting of cells after ligand binding and cross-linking—it was demonstrated that α- as well as β-receptors form ligand-induced dimeric complexes. Dimerization correlated with induction of receptor kinase activity, measured as receptor autophosphorylation. Heterodimeric complexes could furthermore be induced by PDGF-AB, when added to a mixture of lysates from the α- and β-receptor expressing cell lines, or when added to human fibroblasts which express both receptor types.

Key Words:

• platelet-derived growth factor
• receptor
• dimerization
• cross-linking