Changes of phospholipase D activity during glutamate-induced cell death in PC12 cells

초록

Although recent studies have demonstrated glutamate toxicity on PC12 cell line, the intracellular signaling pathways involved in the apoptosis cell death are still poorly characterized. We examined the role of ceramide as a possible intracellular mediator of glutamate-mediated signaling pathways in PC12 cells. Exposure of PC12 cells to glutamate resulted in significant spingomyeline hydrolysis, which was accompanied by a progressive increase in endogenous levels of ceramide. The addition of exogenous C6-ceramide induced drastic morphological changes, including nuclear fragmentation and typical apoptotic DNA degradation. Both glutamate and C6-ceramide decreased phospholipase D (PLD) activity and diacylglycerol (DAG) levels in time- and dose-dependent manner. Treatment of phorbol 12-myristate 13-acetate (PMA), one of the indirect PLD activator, partially suppressed ceramide-induced apoptosis with showing of increased level of PLD activity. In addition, when we transfected PLD cDNA into PC12 cells, PLD was overexpressed exhibiting increased basal PLD activity and glutamate-induced cell death was suppressed. These results indicate that the glutamate/ceramide signaling pathway might play a role in PC12 cell death, and suggest that the PLD/DAG pathway might be cross-linked to the glutamate/ceramide pathway, based on the protective role of PLD /DAG against glutamate-induced cell death in PC12 cells.