Molecular ordering of the Fas-apoptotic pathway: the Fas/APO-1 protease Mch5 is a CrmA-inhibitable protease that activates multiple Ced-3/ICE-like cysteine proteases.
The Fas/APO-1-receptor associated cysteine protease Mch5 (MACH/FLICE) is believed to be the enzyme responsible for activating a protease cascade after Fas-receptor ligation, leading to cell death. The Fas-apoptotic pathway is potently inhibited by the cowpox serpin CrmA, suggesting that Mch5 could be the target of this serpin. Bacterial expression of ... proMch5 generated a mature enzyme composed of two subunits, which are derived from the pre-cursor proenzyme by processing at Asp-227, Asp-233, Asp-391, and Asp-401. We demonstrate that recombinant Mch5 is able to process/activate all known ICE/Ced-3-like cysteine proteases and is potently inhibited by CrmA. This contrasts with the observation that Mch4, the second FADD-related cysteine protease that is also able to process/activate all known ICE/Ced-3-like cysteine proteases, is poorly inhibited by CrmA. These data suggest that Mch5 is the most upstream protease that receives the activation signal from the Fas-receptor to initiate the apoptotic protease cascade that leads to activation of ICE-like proteases (TX, ICE, and ICE-relIII), Ced-3-like proteases (CPP32, Mch2, Mch3, Mch4, and Mch6), and the ICH-1 protease. On the other hand, Mch4 could be a second upstream protease that is responsible for activation of the same protease cascade in CrmA-insensitive apoptotic pathways.
Mesh Terms:
Antigens, CD95, Apoptosis, Caspase 8, Caspase 9, Caspases, Cysteine Endopeptidases, Enzyme Activation, Escherichia coli, Gene Expression, Humans, Serpins, Signal Transduction, Viral Proteins
Antigens, CD95, Apoptosis, Caspase 8, Caspase 9, Caspases, Cysteine Endopeptidases, Enzyme Activation, Escherichia coli, Gene Expression, Humans, Serpins, Signal Transduction, Viral Proteins
Proc. Natl. Acad. Sci. U.S.A.
Date: Dec. 10, 1996
PubMed ID: 8962078
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