Bad overexpression sensitizes NIH/3T3 cells to undergo apoptosis which involves caspase activation and ERK inactivation

The effect of Bad overexpression on apoptosis was demonstrated by a mouse B ad transgene stably expressed in NIH/3T3 cells. The cells overexpressing Ba d treated with either serum starvation or ceramide showed apoptotic charact eristics evident at 18 and 8 h, respectively. Whether serum deprivation and ceramide utilize a common death pathway requires further investigation. Th e time for the first apoptosis detection was shortened to 2 h and was promi nent at 4 h, while above that time cells were maintained under serum-deplet ed conditions in the presence of ceramide (40 mu M). Further investigation revealed that the activity of caspase-3 (CPP32) was elevated after ceramide treatment in Bad-transfected cells compared to that of the cells without B ad transfection, indicating the involvement of caspase cascade. Furthermore , the Bad-transfected cells showed reduced phosphorylation of extracellular signal-regulated kinase (EBB). Taken together, we hypothesize that Bad-ove rexpressing NIH/3T3 cells in the presence of ceramide undergo apoptosis by activating caspase cascade. Simultaneously, the cell survival pathway was b locked possibly by inactivation of the MAPK pathway such as the down-regula tion of ERK. (C) 1999 Academic Press.