Activation of System xc­ Trafficking via an Akt­dependent Signal Transduction Pathway

System xc- is a heterodimeric plasma membrane transporter involved in the exchange of intracellular glutamate for extracellular cystine. As such, this transporter plays a critical role in the production of the antioxidant glutathione. Previous studies in our lab have demonstrated that there is an increase in cell surface expression within ten minutes of exposure to H2O2 in confluent U138MG human glioma cells. The study described herein sought to begin to characterize the mechanism by which H2O2 regulates the trafficking of xCT. We hypothesized that Akt signaling is necessary for H2O2­mediated trafficking of of xCT. A significant increase in Akt phosphorylation was observed in U138MG cells following ten­minute exposure to 3 mM H2O2 compared to vehicle­treated cells using western blot analysis. Treatment with the Akt inhibitor 10­ DEBC (2.5µM) for 30 minutes prior to and during H2O2 exposure resulted in a decrease in H2O2­induced phosphorylation of Akt at Ser473. Similar inhibition of Akt phosphorylation at Thr308 was observed following treatment of cells with 1.0µM API­2. Next, we used simultaneous treatment of cultured glioma cells with both inhibitors in the presence of H2O2 to determine if such treatment led to a reduction in the trafficking of xCT to the plasma membrane. Our preliminary data suggests that Akt activation is necessary for H2O2­induced trafficking xCT to the plasma membrane