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Caspase activity is required for commitment to Fas-mediated apoptosis
1Department of Biological Sciences, Keele University, Staffordshire, UK.
Abstract:
Recognition of the widespread importance of apoptosis has been one of the most significant changes in the biomedical sciences in the past decade. The molecular processes controlling and executing cell death through apoptosis are, however, still poorly understood. The ICE (Interleukin-1beta Converting Enzyme) family-recently named the caspases for cysteine aspartate-specific proteases-plays a central role in apoptosis and may well constitute part of the conserved core mechanism of the process. Potentially, these proteases may be of great significance, both in the pathology associated with failure of apoptosis and also as targets for therapeutic intervention where apoptosis occurs inappropriately, e.g. in degenerative disease and AIDS. However, this is only likely if caspase activity is required before commitment to mammalian cell death. Here, we have used both peptide inhibitors and crmA transfection to inhibit these proteases in intact cells. Our experiments show that selective inhibition of some caspases protects human T cells (Jurkat and CEM-C7) from Fas-induced apoptosis, dramatically increasing their survival (up to 320-fold) in a colony-forming assay. This suggests that dysfunction of some, but not all, caspases could indeed play a crucial part in the development of some cancers and autoimmune disease, and also that these proteases could be appropriate molecular targets for preventing apoptosis in degenerative disease.
Insights
Inhibiting certain caspases (cysteine aspartate-specific proteases) protected human T cells from apoptosis, suggesting their role in diseases and potential as therapeutic targets.
Area of Science:
- Biomedical Sciences
- Cell Biology
- Molecular Biology
Background:
- Apoptosis (programmed cell death) is crucial in biology but its mechanisms are not fully understood.
- The Interleukin-1beta Converting Enzyme (ICE) family, now known as caspases, are key proteases involved in apoptosis.
- Caspase dysfunction is implicated in diseases where apoptosis fails or occurs inappropriately.
Purpose of the Study:
- To investigate the role of caspases in mammalian cell death.
- To determine if inhibiting caspases can prevent apoptosis in human T cells.
- To assess the therapeutic potential of targeting caspases.
Main Methods:
- Used peptide inhibitors and crmA transfection to inhibit caspases in intact human T cells (Jurkat and CEM-C7).
- Assessed cell survival using a colony-forming assay after Fas-induced apoptosis.
- Examined the effect of selective caspase inhibition on apoptosis.
Main Results:
- Selective inhibition of specific caspases significantly protected human T cells from Fas-induced apoptosis.
- Cell survival increased dramatically (up to 320-fold) in treated cells.
- This indicates that caspase activity is required for commitment to cell death.
Conclusions:
- Caspase activity is essential for Fas-induced apoptosis in human T cells.
- Dysfunction of certain caspases may contribute to cancer and autoimmune diseases.
- Caspases represent promising molecular targets for therapeutic intervention in degenerative diseases and conditions involving inappropriate apoptosis.