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A novel Apaf-1-independent putative caspase-2 activation complex
Stuart H Read1, Belinda C Baliga, Paul G Ekert
1Hanson Institute, Adelaide, Australia 5000.
The Journal of Cell Biology
|December 4, 2002
Summary
Caspase-2 activation in stress-induced apoptosis is independent of the Apaf-1 apoptosome. This initiator caspase forms an active complex through spontaneous oligomerization, preceding cytochrome c release.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Caspase activation is crucial for apoptosis execution.
- The mitochondrial pathway, involving cytochrome c and Apaf-1, is central to stress-induced apoptosis.
- Recent findings suggest caspase-2 acts upstream of mitochondria in stress apoptosis.
Purpose of the Study:
- To investigate the mechanism of caspase-2 activation.
- To identify the protein complex involved in caspase-2 activation.
- To determine if caspase-2 activation is Apaf-1 dependent.
Main Methods:
- Gel filtration analysis of cell lysates.
- Substrate-binding assays.
- Studying protein complex formation.
Main Results:
- Caspase-2 spontaneously recruits to a large protein complex independent of cytochrome c and Apaf-1.
- Recruitment to this complex is sufficient for caspase-2 activation.
- Caspase-2 activation can occur without precursor processing, suggesting oligomerization.
Conclusions:
- Caspase-2 activation occurs via oligomerization within a distinct protein complex.
- This activation pathway is independent of the Apaf-1 apoptosome.
- Caspase-2 acts upstream of mitochondrial events in stress-mediated apoptosis.