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Granzyme B-mediated apoptosis proceeds predominantly through a Bcl-2-inhibitable mitochondrial pathway
M J Pinkoski1, N J Waterhouse, J A Heibein
1Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
The Journal of Biological Chemistry
|March 30, 2001
Summary
Cytotoxic T lymphocytes use granzyme B to induce apoptosis. This study shows granzyme B triggers cell death mainly by releasing cytochrome c from mitochondria, a process Bcl-2 can inhibit.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Cytotoxic T lymphocytes (CTLs) are crucial for eliminating virus-infected and tumor cells.
- CTLs utilize cytotoxic granules containing perforin and granzyme B to induce target cell death.
- Granzyme B, a serine protease, activates apoptotic pathways but its precise mechanism remains unclear.
Purpose of the Study:
- To elucidate the primary mechanism of granzyme B-induced apoptosis.
- To investigate the role of mitochondrial pathways and Bcl-2 in granzyme B-mediated cell death.
Main Methods:
- Time-lapse confocal microscopy was employed to visualize cellular events in real-time.
- Analysis focused on the release of cytochrome c and activation of caspases and Bid.
Main Results:
- Mitochondrial cytochrome c release is identified as the principal pathway for granzyme B-induced apoptosis.
- Bcl-2 effectively inhibits granzyme B-mediated cell death by preventing mitochondrial involvement.
- Granzyme B efficiently cleaves and activates Bid, preceding caspase activation, and is more potent than caspases-3 or -8 in this regard.
Conclusions:
- Granzyme B induces apoptosis predominantly through the mitochondrial pathway, involving Bid cleavage and cytochrome c release.
- Bcl-2 acts as a key inhibitor of granzyme B-induced cell death by targeting mitochondrial integrity.
- Understanding this mechanism provides insights into immune surveillance and cancer therapy.