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Tumor suppressor p53 mediates apoptotic cell death triggered by cyclosporin A
Beata Pyrzynska1, Manuel Serrano, Carlos Martínez-A
1Laboratory of Transcription Regulation, Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
Abstract:
The tumor suppressor p53 can induce growth arrest and cell death via apoptosis in response to a number of cellular stresses. We have shown previously that the immunosuppressant cyclosporin A (CsA) induces programmed cell death with typical features of apoptosis in rat glioma cells. We report that CsA treatment results in increased level of the p53 tumor suppressor, its nuclear accumulation, and transcriptional activation of p53-dependent genes. The increase of p53 correlates with the elevation of p21(Waf1) and Bax protein expression. The increased level of Bax protein was accompanied with changes in its subcellular localization and association with mitochondria. Importantly, we demonstrate that glioma cells stably transfected with a mutant p53 (p53Val135) fail to increase p21 and Bax protein levels and are less sensitive to CsA-induced apoptosis. Furthermore, primary fibroblasts from p53-/- knockout mice are significantly more resistant to CsA-induced apoptosis compared with their corresponding counterparts containing functional p53. Together, our results suggest that the apoptotic program activated by CsA can be mediated by activation of p53 tumor suppressor and potentiation of its ability to initiate apoptosis.
Insights
Cyclosporin A (CsA) triggers apoptosis in glioma cells by increasing the tumor suppressor p53. This p53 activation leads to elevated p21 and Bax, crucial for CsA-induced cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The tumor suppressor p53 is a key regulator of cellular responses to stress, including apoptosis.
- Cyclosporin A (CsA), an immunosuppressant, has been previously shown to induce apoptosis in rat glioma cells.
Purpose of the Study:
- To investigate the role of the p53 tumor suppressor in CsA-induced apoptosis in glioma cells.
- To elucidate the molecular mechanisms by which CsA triggers programmed cell death.
Main Methods:
- Western blotting to assess protein levels (p53, p21, Bax).
- Immunofluorescence for nuclear accumulation of p53.
- Apoptosis assays in CsA-treated glioma cells and p53-deficient cells.
- Transfection with mutant p53 (p53Val135) and use of p53-/- knockout mouse fibroblasts.
Main Results:
- CsA treatment increased p53 levels, nuclear accumulation, and transcriptional activity of p53-dependent genes.
- Elevated p53 correlated with increased p21(Waf1) and Bax protein expression, with Bax showing altered mitochondrial localization.
- Glioma cells with mutant p53 and p53-/- fibroblasts exhibited reduced sensitivity to CsA-induced apoptosis.
- CsA treatment led to increased p21 and Bax protein levels in wild-type cells but not in mutant p53 cells.
Conclusions:
- CsA-induced apoptosis in glioma cells is mediated by the activation of the p53 tumor suppressor pathway.
- p53 activation potentiates the apoptotic response to CsA, involving p21 and Bax.
- The findings highlight p53 as a critical mediator in CsA-induced programmed cell death.