Abstract
NADH shuttles mediate the transfer of the reducing equivalents of cytosolic NADH into mitochondria. Increasing evidence has suggested that malate-aspartate shuttle (MAS), one of the two types of NADH shuttles, plays important roles in certain biological processes. Aralar/AGC1, a Ca(2+)-dependent aspartate-glutamate carrier on mitochondrial membrane, is a component of MAS. It has been reported that Aralar plays crucial roles in linking increased cytosolic Ca(2+) concentrations to enhanced mitochondrial energy metabolism of neurons under certain conditions, while the role of the carrier in cell survival remains unknown. In the current study, we tested our hypothesis that Aralar plays an important role in cell survival, using BV2 microglia as a cellular model. Our study showed that Aralar siRNA-produced decrease in the Aralar level led to a significant reduction of the cell survival. Our FACS-based Annexin V/7-AAD assays also showed that the Aralar siRNA treatment led to a significant increase in apoptosis of the cells. Moreover, the Aralar siRNA treatment led to both mitochondrial depolarization and decreases in the intracellular ATP level of the cells. Collectively, our study has provided the first evidence suggesting that Aralar plays a significant role in cell survival, at least for such cell types as BV2 microglia, possibly by producing mitochondrial depolarization. These observations have also provided novel information for understanding the roles of NADH shuttles in cell survival.