title: Oxidative modification of caspase-9 facilitates its activation via disulfide-mediated interaction with Apaf-1.
abstract: Intracellular reactive oxygen species (ROS) are known to regulate apoptosis. Activation of caspase-9, the initial caspase in the mitochondrial apoptotic cascade, is closely associated with ROS, but it is unclear whether ROS regulate caspase-9 via direct oxidative modification. The present study aims to elucidate the molecular mechanisms by which ROS mediate caspase-9 activation. Our results show that the cellular oxidative state facilitates caspase-9 activation. Hydrogen peroxide treatment causes the activation of caspase-9 and apoptosis, and promotes an interaction between caspase-9 and apoptotic protease-activating factor 1 (Apaf-1) via disulfide formation. In addition, in an in vitro mitochondria-free system, the thiol-oxidant diamide promotes auto-cleavage of caspase-9 and the caspase-9/Apaf-1 interaction by facilitating the formation of disulfide-linked complexes. Finally, a point mutation at C403 of caspase-9 impairs both H(2)O(2)-promoted caspase-9 activation and interaction with Apaf-1 through the abolition of disulfide formation. The association between cytochrome c and the C403S mutant is significantly weaker than that between cytochrome c and wild-type caspase-9, indicating that oxidative modification of caspase-9 contributes to apoptosome formation under oxidative stress. Taken together, oxidative modification of caspase-9 by ROS can mediate its interaction with Apaf-1, and can thus promote its auto-cleavage and activation. This mechanism may facilitate apoptosome formation and caspase-9 activation under oxidative stress.
authors.affiliation: Department of Cell Biology, Key Laboratory of the Education Ministry for Cell Differentiation and Apoptosis, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zuo
authors.forename: Binggang
authors.initials: B
authors.lastname: Xiang
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.forename: Xuxu
authors.initials: X
authors.lastname: Sun
authors.forename: Yumei
authors.initials: Y
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Cang
authors.forename: Jing
authors.initials: J
authors.lastname: Yi
mesh_terms: D019943:Amino Acid Substitution; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism*; D053453:Caspase 9 / Q000378:metabolism*; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D003958:Diamide / Q000494:pharmacology; D004220:Disulfides / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D050505:Mutant Proteins / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000494:pharmacology
chemical_list: D053477:Apoptotic Protease-Activating Factor 1; D004220:Disulfides; D050505:Mutant Proteins; D017382:Reactive Oxygen Species; D003958:Diamide; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D053453:Caspase 9