Epidermal growth factor receptor is modulated by redox through multiple mechanisms. Effects of reductants and H₂O₂

The cellular redox state has been shown to play an essential role in cellular signaling systems. Here we investigate the effects of reductants and H₂O₂ on the signaling of epidermal growth factor (EGF) in cells, H₂O₂ induced the phosphorylation of the EGF receptor and the formation of a receptor complex comprising Shc, Grb2, Sos, and the EGF receptor. Dimerization or oligomerization of the EGF receptor was not induced by H₂O₂. Protein tyrosine phosphatase (PTP) assay showed that H₂O₂ suppressed dephosphorylation of the EGF receptor in cell lysates, suggesting that inactivation of PTP was involved in H₂O₂-induced activation of the EGF receptor. In contrast, the reductants N-acetyl-L-cysteine [Cys(Ac)] and dithiothreitol markedly suppressed EGF-induced dimerization and activation of the EGF receptor in cells. In accordance with suppression of the EGF receptor. Cys(Ac) suppressed EGF-induced activation of Ras, phosphatidylinositol 3-kinase and mitogen-activated protein kinase. Dithiothreitol completely inhibited EGF binding and kinase activation of the EGF receptor both in vitro and in vivo. In contrast, Cys(Ac) suppressed high- affinity EGF-binding sites on the cells, but had no effect on low-affinity binding sites. Furthermore. Cys (Ac) did not suppress EGF-induced kinase activation or dimerization of the EGF receptor in vitro, indicating that it suppressed the EGF receptor through a redox-sensitive cellular process or processes. Thus, the EGF receptor is regulated by redox through multiple steps including dephosphorylation by PTP, ligand binding, and a Cys(Ac)- sensitive cellular process or processes.