Cisplatin treatment induces extensive death of the proximal tubules in mice. We also demonstrated that treatment of immortalized mouse proximal tubule cells (TKPTS) with 25 microM cisplatin induces apoptotic death in vitro. Here, we demonstrate that members of the MAPKs such as ERK, JNK, and p38 are all activated after cisplatin treatment both in vivo and in vitro. Because MAPKs mediate cell survival and death, we studied their role in cisplatin-induced cell death in vitro. Apoptosis was confirmed by cell morphology, fluorescence-activated cell-sorting analysis, annexin V/propidium iodide binding, and caspase-3 activation in TKPTS cells. Inhibition of ERK, but not JNK or p38, abolished caspase-3 activation and apoptotic death, suggesting a prodeath role of ERK in cisplatin-induced injury. We also determined that cisplatin-induced ERK as well as caspase-3 activation are epidermal growth factor receptor (EGFR) and c-src dependent because inhibition of these genes inhibited ERK and caspase-3 activation and attenuated apoptotic death. These results suggest that caspase-3 mediates cisplatin-induced cell death in TKPTS cells via an EGFR/src/ERK-dependent pathway. We also suggest that the prodeath effect of ERK is injury type dependent because during oxidant injury, ERK supports survival rather than death in the same cells. We propose that injury-specific outcome diverges downstream from ERK in cisplatin- or H(2)O(2)-mediated cell survival and death.