JNK/SAPK activation by platelet-derived growth factor in A431 cells requires both the phospholipase C-gamma and the phosphatidylinositol 3-kinase signaling pathways of the receptor.

Wild-type or mutant betaPDGF receptors were introduced into A431 cells that lack endogenous PDGF receptors. PDGF stimulates JNK1 activity in a dose- and time-dependent manner in cells expressing the wild-type receptor. A receptor mutant lacking all the binding sites for SHP-2, GAP, PI3K, and PLC-gamma fails to activate JNK1. Receptor mutants with no binding site for either SHP-2 or GAP can fully activate JNK1 but those which do not bind either PI3K or PLC-gamma are unable to induce JNK1 activation. PDGF-dependent JNK1 activation was reduced upon cell pretreatment with wortmannin or GF109203X and is completely abrogated by chronic PMA stimulation. Altogether, these results indicate that PDGF activates JNK1 through a pathway that involves both PI3K and PLC-gamma and subsequent activation of protein kinase C.
(Copyright 1999 Academic Press.)