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BAX-induced cell death may not require interleukin 1 beta-converting enzyme-like proteases
J Xiang1, D T Chao, S J Korsmeyer
1Department of Medicine and Pathology, Howard Hughes Medical Institute, Washington University, St. Louis, MO 63110, USA.
Summary
BAX protein triggers apoptosis through a common pathway involving specific proteases. However, BAX-induced cell death and mitochondrial dysfunction persist even when these proteases are inhibited, suggesting an alternative cell death mechanism.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis, or programmed cell death, is crucial for development and tissue homeostasis.
- The BAX protein is a key mediator of apoptosis, but the precise mechanisms downstream of its activation are not fully understood.
- Interleukin 1 beta-converting enzyme (ICE)-like proteases are known to play a role in apoptotic pathways.
Purpose of the Study:
- To investigate the role of ICE-like proteases in BAX-induced apoptosis.
- To determine whether BAX-induced cell death requires the activation of ICE-like proteases.
- To elucidate the downstream events of BAX activation, particularly concerning mitochondrial function.
Main Methods:
- Inducing apoptosis via BAX expression in the absence of other death stimuli.
- Utilizing the ICE-like protease inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk).
- Assessing the cleavage of substrates like poly(ADP ribose) polymerase and D4-GDI.
- Monitoring mitochondrial membrane potential, reactive oxygen species production, and DNA degradation.
Main Results:
- BAX expression alone was sufficient to initiate apoptosis, involving ICE-like protease activation and substrate cleavage.
- zVAD-fmk inhibited protease activity and FAS-induced death but did not prevent BAX-induced cell death.
- Inhibition of ICE-like proteases blocked substrate cleavage and DNA degradation following BAX induction.
- Key downstream events of BAX, including mitochondrial dysfunction and plasma membrane permeability changes, occurred independently of ICE-like proteases.
Conclusions:
- BAX-induced apoptosis involves ICE-like proteases for nuclear and cytosolic substrate cleavage and DNA degradation.
- However, BAX-mediated mitochondrial dysfunction and subsequent cell death do not appear to require the activity of known ICE-like proteases.
- This suggests that BAX may initiate cell death through pathways independent of the canonical ICE-like protease cascade.