Platelet-derived growth factor AB heterodimer interchain interactions influence secretion as well as receptor binding and activation

Abstract

Platelet-derived growth factor (PDGF) is a disulfide-linked dimer comprised of two related polypeptide chains. To investigate the effects of an inactivating lesion introduced into one chain of the nascent PDGF dimer, approaches were developed to optimize synthesis, assembly, secretion, and purification of heterodimers between normal PDGF A and wild-type or mutant PDGF B. PDGF AB heterodimers were released into culture fluids less efficiently than PDGF AA, but to a greater degree than the cell-associated PDGF BB. These results suggest that interactions between two chains influence PDGF secretion. Analysis of heterodimers between PDGF A and disabled PDGF B mutants on cells that express either alpha or beta PDGFRs demonstrated that the impaired biologic activity of the mutant PDGF B chain was ameliorated with respect to binding and triggering of alpha PDGFRs. In cells that expressed both receptor types, heterodimers of mutant PDGF B and wild-type PDGF A gained substantially in their ability to recruit and trigger alpha, but not beta, PDGFRs. Partial rescue of impaired PDGF B mutant chain function by dimer formation with a wild-type PDGF A chain implies that interchain interactions markedly affect PDGFR binding and activation.

Regulation of Ets function by protein–protein interactions

“…Transformation activity or cancer progression has been linked with the alteration of the Pointed domain. Substitution of the Pointed domains of ERG and Fli1 by EWS in the chimeric EWS-ERG and EWS-Fli1 results in strong transforming factor (Bailly et al, 1994;May et al, 1993). This may be in part due to ability of EWS-Fli1, but not Fli1, to interact with human RNA polymerase II (hsRPB7).…”