H₂O₂-induced transactivation of EGF receptor requires Src and mediates ERK1/2, but not Akt, activation in renal cells

Although oxidative stress activates epidermal growth factor receptor (EGFR), ERK1/2, and Akt in a number of cell types, the mechanisms by which oxidative stress activates these kinases are not well defined in renal epithelial cells. Exposure of primary cultures of rabbit renal proximal tubular cells to hydrogen peroxide (H₂O₂) stimulated Src, EGFR, ERK1/2, and Akt activation in a time-dependent manner as determined by the phosphorylation of each protein. The Src inhibitor PP1 completely blocked EGFR, ERK1/2, and Akt phosphorylation following H₂O₂ exposure. In contrast, blockade of the EGFR by AG1478 inhibited phosphorylation of ERK1/2 but not Src or Akt phosphorylation following H₂O₂ exposure. Exogenous EGF stimulated EGFR, ERK1/2, and Akt activation and the EGFR inhibitor blocked phorphorylation of ERK1/2 and Akt. The presence of PP1, but not AG1478, significantly accelerated H₂O₂-induced cell death. These results suggest that Src mediates H₂O ₂-induced EGFR transactivation. H₂O₂- and EGF-induced ERK1/2 activation is mediated by EGFR, whereas Akt is activated by Src independent of EGFR following H₂O₂ exposure. Src-mediated EGFR transactivation contributes to a survival response following oxidative injury.