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 cellul ar signaling systems. Here we investigate the effects of reductants and H2O 2 on the signaling of epidermal growth factor (EGF) in cells. H2O2 induced the phosphorylation of the EGF receptor and the formation of a receptor com plex comprising Shc, Grb2, Sos, and the EGF receptor. Dimerization or oligo merization of the EGF receptor was not induced by H2O2. Protein tyrosine ph osphatase (PTP) assay showed that H2O2 suppressed dephosphorylation of the EGF receptor in cell lysates, suggesting that inactivation of PTP was invol ved in H2O2-induced activation of the EGF receptor. In contrast, the reduct ants N-acetyl-L-cysteine [Cys(Ac)] and dithiothreitol markedly suppressed E GF-induced dimerization and activation of the EGF receptor in cells. In acc ordance with suppression of the EGF receptor, Cys(Ac) suppressed EGF-induce d activation of Ras, phosphatidylinositol 3-kinase and mitogen-activated pr otein kinase. Dithiothreitol completely inhibited EGF binding and kinase ac tivation 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 effec t on low-affinity binding sites. Furthermore, Cys(Ac) did not suppress EGF- induced kinase activation or dimerization of the EGF receptor in vitro, ind icating that it suppressed the EGF receptor through a redox-sensitive cellu lar process or processes. Thus, the EGF receptor is regulated by redox thro ugh multiple steps including dephosphorylation by PTP, ligand binding, and a Cys(Ac)-sensitive cellular process or processes.