Reversible inhibition of the protein phosphatase 1 by hydrogen peroxide. Potential regulation of eIF2α phosphorylation in differentiated PC12 cells

Oxidative inactivation of protein tyrosine phosphatases and calcineurin is a well established mechanism; however, little information with regard to the effect of oxidants on PP1 and PP2A activity is available. Herein, we show that PP1 activity is inhibited by H2O2 treatment in differentiated PC12 cells both in vitro and in vivo experiments. Thiol-antioxidant N-acetyl-cysteine (NAC) and reduced glutathione (GSH), when added in vitro to lysates from H2O2-treated cells, reversed PP1 inhibition. H2O2 treatment increased eIF2α phosphorylated levels (eIF2αP) in a time- and dose-dependent fashion and promoted protein synthesis inhibition. Interestingly, NAC pretreatment protected cells from H2O2-induced PP1 inactivation and, consequently, it abolished increased H2O2-induced eIF2α phosphorylation and protein synthesis inhibition. In addition, PP1 inhibitor tautomycin prevented both NAC-induced PP1 reactivation and eIF2αP dephosphorylation in H2O2-treated cells. Taken together, our findings support a role for PP1 in eIF2α phosphorylation and oxidative stress-triggered translation down regulation.