Nonconfluent Cultures of Human Glioma (U138MG) Cells are More Susceptible to Oxidative Stress Than Confluent Cultures
This research was supported by NSF-RUI # 0843564.
System xc- is a plasma membrane transport system that is comprised of two proteins, xCT and 4F2HC. The transporter catalyzes the exchange of cystine and glutamate across the membrane glia and some neurons. Previous research in the Chase lab demonstrated that differences in basal transporter activity in confluent and nonconfluent cultured human glioma (U138MG) cells are a result of differential membrane localization of xCT. Specifically, we have demonstrated that a greater fraction of xCT is localized to the membrane in nonconfluent cultures than confluent cultures. However, there is no increase in xCT membrane expression in nonconfluent cultures following exposure of cells to hydrogen peroxide (H2O2), whereas confluent cultures exhibit an increase in the localization of xCT to the membrane following such an insult. We are currently exploring the functional implications of these findings. We hypothesized that the differences in membrane trafficking of System xc- in confluent and nonconfluent cultures would result in a difference in their susceptibility to H2O2 mediated damage. Using a trypan blue cell death assay, we demonstrated that confluent cultures were less susceptible to H2O2 mediated cell death in comparison to nonconfluent cell cultures (p <0.01). We are currently confirming these results using a MTT cell death assay. These data provide further evidence that the trafficking of System xc- plays an important role in the acute antioxidant defense pathway of glioma cells.