CRITICAL ROLE OF CALCIUM-DEPENDENT EPIDERMAL GROWTH-FACTOR RECEPTOR TRANSACTIVATION IN PC12 CELL-MEMBRANE DEPOLARIZATION AND BRADYKININ SIGNALING

PC12 cells respond to a variety of external stimuli such as growth fac tors, neurotransmitters, and membrane depolarization by activating the Ras/mitogen-activated protein kinase pathway, Here we demonstrate tha t both depolarization-induced calcium influx and treatment with bradyk inin stimulate tyrosine phosphorylation of the epidermal growth factor receptor (EGFR). Using a tetracycline-controlled expression system in conjunction with a dominant-negative EGFR mutant, we demonstrate that depolarization and bradykinin triggered signals involve EG;FR functio n upstream of SHC and MAP kinase, Furthermore, bradykinin-stimulated E GFR transactivation is critically dependent on the presence of extrace llular calcium, and when triggered by ionophore treatment, calcium inf lux is already sufficient to induce EGFR tyrosine phosphorylation, Tak en together, our results establish calcium-dependent EGFR transactivat ion as a signaling mechanism mediating activation of the Ras/mitogen-a ctivated protein kinase pathway in neuronal cell types.