Hydrogen peroxide controls Akt activity via ubiquitination/degradation pathways.

Akt is a well-established protein that regulates cell growth, survival and anti-apoptotic mechanisms. In this study, we demonstrated that hydrogen peroxide (H2O2)-induced oxidative stress regulates the activity of the anti-apoptotic protein Akt via the ubiquitin-proteasome degradation system. H2O2 induced cytotoxicity in PC12 cells and decreased the cellular protein and phosphorylation levels of Akt in a concentration- and exposure time-dependent manner. This downregulation was blocked by the proteasome inhibitor MG132 and the Akt-specific inhibitor LY294002. In addition, an in vivo ubiquitination assay revealed that the degradation of Akt was mediated by the ubiquitin-mediated proteasome pathway and further demonstrated that this ubiquitination was dependent on the phosphorylation status of Akt. Furthermore, the exogenously overexpressed active form of Akt, but not its inactive form, induced resistance to H2O2-mediated cell death. These results suggested that H2O2-induced cytotoxicity was mediated by active Akt degradation.