EPIDERMAL GROWTH-FACTOR RECEPTOR STIMULATION OF DIACYLGLYCEROL KINASE

The epidermal growth factor receptor (EGFR) activates formation of the phospholipid signal messenger phosphatidic acid (PA) on ligand bindin g. We explored the effects of chronic EGF stimulation on cellular PA i n NIH3T3 cells expressing intact EGFR a mutant EGFR (EGFRvIII). The pr esence of EGFRvIII increased PA levels to twice those induced by chron ic EGFR activation. Fatty acid methyl ester analysis revealed a marked increase in oleic acid containing PA. No apparent increase in phospho lipase D (PLD) activity was detected, and diacylglycerol (DAG) kinase assays demonstrated a marked preference for dioleoyl DAG in the presen ce of activated EGFR or EGFRvIII. Levels of PA which were lower than w ould be predicted by DAC; kinase activation are explained by increased phosphatidate phosphohydrolase activity, Specific inhibitors of EGFR kinase and DAG kinase suppressed DAG kinase activation and PA producti on by EGFRvIII. EGFR kinase activation by chronic exposure to ligand o r by deletional mutation stimulates formation of a specific form of si gnalling PA. (C) 1997 Academic Press.