title: 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.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Philadelphia, PA 19107, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Srinivasula
authors.forename: M
authors.initials: M
authors.lastname: Ahmad
authors.forename: T
authors.initials: T
authors.lastname: Fernandes-Alnemri
authors.forename: G
authors.initials: G
authors.lastname: Litwack
authors.forename: E S
authors.initials: ES
authors.lastname: Alnemri
mesh_terms: D017209:Apoptosis; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D015843:Serpins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014764:Viral Proteins; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D015843:Serpins; D014764:Viral Proteins; D019014:fas Receptor; C074641:interleukin-1beta-converting enzyme inhibitor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases