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Involvement of caspase-4(-like) protease in Fas-mediated apoptotic pathway
S Kamada1, M Washida, J Hasegawa
1Department of Medical Genetics, Biomedical Research Center, Osaka University Medical School, Suita, Japan.
Abstract:
Proteases of the caspase family, especially caspase-1 (ICE)(-like), caspase-3 (CPP32/Yama/apopain)(-like) and caspase-8 (MACH/FLICE/Mch5) proteases, are implicated in Fas (APO-1/CD95)-mediated apoptosis. Here, we show that the caspase-4 (TX/ICH-2/ICE(rel)II)(-like) protease, another member of the caspase family, is also involved in Fas-mediated apoptosis, based upon the observations: (i) caspase-4 is processed in response to an agonistic anti-Fas antibody treatment, (ii) overexpression of a mutant caspase-4 with active site mutations in both p20 and p10 subunits delays Fas-mediated apoptosis, (iii) microinjected anti-caspase-4 antibodies inhibit Fas-mediated apoptosis. Together with our observations that the mutant caspase-4 inhibits the Fas-mediated activation of caspase-3(-like) proteases and purified caspase-4 cleaves pro-caspase-3 to generate a subunit of active form, these results suggest that Fas-mediated apoptosis is driven by a caspase cascade in which the caspase-4(-like) protease transmits a death signal from caspase-8 to caspase-3(-like) proteases probably through directly cleaving pro-caspase-3(-like) proteases.
Insights
Caspase-4 protease plays a crucial role in Fas-mediated apoptosis by transmitting death signals. This finding reveals a new caspase cascade pathway involved in programmed cell death.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- Caspase proteases are key regulators of apoptosis.
- Caspase-1, -3, and -8 are known to be involved in Fas-mediated apoptosis.
Purpose of the Study:
- To investigate the role of caspase-4 in Fas-mediated apoptosis.
- To elucidate the mechanism by which caspase-4 participates in the apoptotic pathway.
Main Methods:
- Western blotting to detect caspase-4 processing.
- Overexpression of a catalytically inactive caspase-4 mutant.
- Microinjection of anti-caspase-4 antibodies.
- Assays for caspase-3 activation and cleavage.
Main Results:
- Caspase-4 undergoes processing upon stimulation with an anti-Fas antibody.
- Overexpression of a dominant-negative caspase-4 mutant inhibits Fas-mediated apoptosis.
- Anti-caspase-4 antibodies block Fas-induced apoptosis.
- Caspase-4 directly cleaves pro-caspase-3 and inhibits caspase-3 activation.
Conclusions:
- Caspase-4 is a critical component of the Fas-mediated apoptotic pathway.
- Caspase-4 acts downstream of caspase-8 and upstream of caspase-3 in a caspase cascade.
- Caspase-4 transmits the apoptotic signal by cleaving and activating caspase-3.