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Bad overexpression sensitizes NIH/3T3 cells to undergo apoptosis which involves caspase activation and ERK
1Department of Microbiology, National Cheng Kung University Medical College, Tainan, Taiwan, Republic of China.
Abstract:
The effect of Bad overexpression on apoptosis was demonstrated by a mouse Bad transgene stably expressed in NIH/3T3 cells. The cells overexpressing Bad treated with either serum starvation or ceramide showed apoptotic characteristics evident at 18 and 8 h, respectively. Whether serum deprivation and ceramide utilize a common death pathway requires further investigation. The time for the first apoptosis detection was shortened to 2 h and was prominent at 4 h, while above that time cells were maintained under serum-depleted conditions in the presence of ceramide (40 microM). 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 Bad transfection, indicating the involvement of caspase cascade. Furthermore, the Bad-transfected cells showed reduced phosphorylation of extracellular signal-regulated kinase (ERK). Taken together, we hypothesize that Bad-overexpressing NIH/3T3 cells in the presence of ceramide undergo apoptosis by activating caspase cascade. Simultaneously, the cell survival pathway was blocked possibly by inactivation of the MAPK pathway such as the down-regulation of ERK.
Insights
Overexpressing the Bad gene in NIH/3T3 cells accelerates apoptosis, particularly when treated with ceramide. This suggests Bad protein activates caspase cascades and blocks survival pathways like ERK signaling.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Apoptosis, or programmed cell death, is a crucial biological process.
- The role of Bad, a pro-apoptotic protein, in regulating cell death pathways is of significant interest.
- Understanding how specific cellular conditions trigger apoptosis is vital for disease research.
Purpose of the Study:
- To investigate the effect of Bad gene overexpression on apoptosis in NIH/3T3 cells.
- To explore the potential involvement of caspase cascades and MAPK pathways in ceramide-induced apoptosis.
- To determine if Bad overexpression influences the kinetics and mechanisms of apoptosis.
Main Methods:
- Stable expression of a mouse Bad transgene in NIH/3T3 cells.
- Induction of apoptosis using serum starvation and ceramide treatment.
- Measurement of apoptotic characteristics, caspase-3 (CPP32) activity, and extracellular signal-regulated kinase (ERK) phosphorylation.
Main Results:
- Bad overexpression significantly shortened the time to apoptosis detection, especially under ceramide treatment.
- Ceramide treatment elevated caspase-3 activity in Bad-overexpressing cells, indicating caspase cascade activation.
- Bad-transfected cells exhibited reduced ERK phosphorylation, suggesting MAPK pathway inactivation.
Conclusions:
- Bad overexpression in NIH/3T3 cells promotes apoptosis, primarily through the activation of caspase cascades.
- Ceramide-induced apoptosis in Bad-overexpressing cells involves the blockage of cell survival pathways, potentially via ERK inactivation.
- These findings highlight the critical role of Bad in modulating apoptosis and cell survival signaling.