Cdc42 is a substrate for caspases and influences Fas-induced apoptosis.
Fas-mediated apoptosis results in the activation of caspases, which subsequently cleave cellular substrates that are essential for normal cell viability. In the present study, we show that the Ras-related GTP-binding protein Cdc42 is susceptible to caspase-catalyzed proteolysis in a number of cell lines, including NIH3T3 fibroblasts, human breast cancer cells (e.g. T47D), and COS-7 cells. Both caspase-3 and caspase-7 were able to catalyze the cleavage of Cdc42, whereas caspase-6 and caspase-8 were without effect. The susceptibility to the caspase-stimulated degradation is specific; although Rac can also serve as a caspase substrate, neither Rho nor Ras is degraded. Caspase sensitivity is conferred by a consensus sequence (DXXD) that lies immediately upstream of the Rho insert regions (residues 122-134) of Cdc42 and Rac. The removal of a stretch of residues (120) that includes the insert region or site-directed mutagenesis of either aspartic acid 118 or 121 within a constitutively active background (i.e. Cdc42(F28L)) as well as a wild-type Cdc42 background yields Cdc42 molecules that provide a marked protection against Fas ligand-induced apoptosis. Overall, these results are consistent with a model in which Cdc42 acts downstream of Fas, perhaps to influence the rate of apoptosis, with the ultimate caspase-mediated degradation of Cdc42 then allowing for a maximal apoptotic response.
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Department of Molecular Medicine, Veterinary Medical Center, Baker Laboratory, Cornell University, Ithaca, New York, 14853, USA.
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D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis; D001224:Aspartic Acid / Q000378:metabolism; D019556:COS Cells; D053178:Caspase 6; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000737:chemistry* / Q000378:metabolism*; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D053222:Fas Ligand Protein; D017353:Gene Deletion; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism*
C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D019014:fas Receptor; D001224:Aspartic Acid; C505514:CASP6 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505516:Casp6 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053178:Caspase 6; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D020764:cdc42 GTP-Binding Protein