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Inactivation of multiple targets by nitric oxide in CD95-triggered apoptosis
F Bernassola1, M V Catani, M Corazzari
1Biochemistry Laboratory, IDI-IRCCS, c/o Department of Experimental Medicine, University of Rome Tor Vergata, 00133 Rome, Italy.
Abstract:
Nitric oxide (NO) plays an important anti-apoptotic role by inactivating both upstream and downstream apoptotic molecules. We now report that exogenously supplied NO protected Jurkat T cells from anti-CD95-stimulated apoptosis. We have recently shown that nitrosation of the activator protein-1 (AP-1) transcriptional factor is crucial for NO-mediated inhibition of cell death triggered by etoposide or ceramide. Since the inhibition of apoptosis by NO has been reported to involve AP-1, we evaluated its involvement in in CD95-mediated cell death. Cross-linking of CD95 enhanced AP-1 DNA binding activity and AP-1-dependent CD95L transactivation, which were both significantly reduced by different NO-donors compounds. However, AP-1 induction does not seem to significantly contribute to anti-CD95-triggered apoptosis, as cell death could not be prevented by using the recombinant Fas-Fc fusion protein which inhibits the CD95/CD95L interaction. We observed that caspase 3-like activity was negatively modulated by several NO-donors in vitro and that titratable thiol groups of purified caspases 3, 7, and 9 decreased in the presence of NO-releasing compounds. In conclusion, we demonstrated that NO-mediated inhibition of other targets, possibly caspases, but not AP-1, is a crucial event responsible for protection against anti-CD95-stimulated apoptosis. Even though NO affects multiple molecular mechanisms, the relevant target for exerting the cellular effects, may vary among different models.
Insights
Nitric oxide (NO) protects Jurkat T cells from CD95-induced cell death by targeting molecules like caspases, not the AP-1 factor. This finding highlights NO's complex anti-apoptotic mechanisms.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Nitric oxide (NO) is known to inhibit apoptosis through various molecular mechanisms.
- Previous research indicated that NO-mediated cell death inhibition involves the activator protein-1 (AP-1) transcriptional factor.
Purpose of the Study:
- To investigate the role of AP-1 in nitric oxide-mediated protection against anti-CD95-stimulated apoptosis in Jurkat T cells.
- To identify the specific molecular targets of NO responsible for its anti-apoptotic effects in this context.
Main Methods:
- Jurkat T cells were treated with NO-donors and stimulated with anti-CD95 antibodies.
- AP-1 DNA binding activity and AP-1-dependent CD95L transactivation were assessed.
- Caspase activity and thiol group modification were measured in vitro.
Main Results:
- Exogenously supplied NO protected Jurkat T cells from anti-CD95-induced apoptosis.
- While NO donors reduced AP-1 DNA binding and CD95L transactivation, AP-1 did not appear to be the primary mediator of protection against CD95-triggered cell death.
- NO donors inhibited caspase 3-like activity and modified thiol groups in caspases 3, 7, and 9.
Conclusions:
- Nitric oxide confers protection against anti-CD95-stimulated apoptosis in Jurkat T cells.
- The anti-apoptotic effect of NO in this model is primarily mediated by targets other than AP-1, likely including caspases.
- The specific molecular targets of NO may vary depending on the cellular context and death-inducing stimulus.