title: Deficiency in caspase-9 or caspase-3 induces compensatory caspase activation.
abstract: Dysregulation of apoptosis contributes to the pathogenesis of many human diseases. As effectors of the apoptotic machinery, caspases are considered potential therapeutic targets. Using an established in vivo model of Fas-mediated apoptosis, we demonstrate here that elimination of certain caspases was compensated in vivo by the activation of other caspases. Hepatocyte apoptosis and mouse death induced by the Fas agonistic antibody Jo2 required proapoptotic Bcl-2 family member Bid and used a Bid-mediated mitochondrial pathway of caspase activation; deficiency in caspases essential for this pathway, caspase-9 or caspase-3, unexpectedly resulted in rapid activation of alternate caspases after injection of Jo2, and therefore failed to protect mice against Jo2 toxicity. Moreover, both ultraviolet and gamma irradiation, two established inducers of the mitochondrial caspase-activation pathway, also elicited compensatory activation of caspases in cultured caspase-3(-/-) hepatocytes, indicating that the compensatory caspase activation was mediated through the mitochondria. Our findings provide direct experimental evidence for compensatory pathways of caspase activation. This issue should therefore be considered in developing caspase inhibitors for therapeutic applications.
authors.affiliation: Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Zheng
authors.forename: S
authors.initials: S
authors.lastname: Hunot
authors.forename: K
authors.initials: K
authors.lastname: Kuida
authors.forename: T
authors.initials: T
authors.lastname: Momoi
authors.forename: A
authors.initials: A
authors.lastname: Srinivasan
authors.forename: D W
authors.initials: DW
authors.lastname: Nicholson
authors.forename: Y
authors.initials: Y
authors.lastname: Lazebnik
authors.forename: R A
authors.initials: RA
authors.lastname: Flavell
mesh_terms: D000818:Animals; D000906:Antibodies / Q000633:toxicity; D017209:Apoptosis; D020170:Caspase 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006470:Hemorrhage / Q000473:pathology; D022781:Hepatocytes / Q000166:cytology / Q000201:enzymology / Q000502:physiology; D006801:Humans; D008099:Liver / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000502:physiology; D008930:Mitochondria, Liver / Q000502:physiology / Q000528:radiation effects; D019014:fas Receptor / Q000276:immunology / Q000502:physiology
chemical_list: D000906:Antibodies; D019014:fas Receptor; C505407:CASP3 protein, human; C506433:CASP9 protein, human; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D020170:Caspase 1