title: Mitochondrial release of caspase-2 and -9 during the apoptotic process.
abstract: The barrier function of mitochondrial membranes is perturbed early during the apoptotic process. Here we show that the mitochondria contain a caspase-like enzymatic activity cleaving the caspase substrate Z-VAD.afc, in addition to three biological activities previously suggested to participate in the apoptotic process: (a) cytochrome c; (b) an apoptosis-inducing factor (AIF) which causes isolated nuclei to undergo apoptosis in vitro; and (c) a DNAse activity. All of these factors, which are biochemically distinct, are released upon opening of the permeability transition (PT) pore in a coordinate, Bcl-2-inhibitable fashion. Caspase inhibitors fully neutralize the Z-VAD.afc-cleaving activity, have a limited effect on the AIF activity, and have no effect at all on the DNase activities. Purification of proteins reacting with the biotinylated caspase substrate Z-VAD, immunodetection, and immunodepletion experiments reveal the presence of procaspase-2 and -9 in mitochondria. Upon induction of PT pore opening, these procaspases are released from purified mitochondria and become activated. Similarly, upon induction of apoptosis, both procaspases redistribute from the mitochondrion to the cytosol and are processed to generate enzymatically active caspases. This redistribution is inhibited by Bcl-2. Recombinant caspase-2 and -9 suffice to provoke full-blown apoptosis upon microinjection into cells. Altogether, these data suggest that caspase-2 and -9 zymogens are essentially localized in mitochondria and that the disruption of the outer mitochondrial membrane occurring early during apoptosis may be critical for their subcellular redistribution and activation.
authors.affiliation: Centre National de la Recherche Scientifique, UPR 420, F-94801 Villejuif, France.
authors.forename: S A
authors.initials: SA
authors.lastname: Susin
authors.forename: H K
authors.initials: HK
authors.lastname: Lorenzo
authors.forename: N
authors.initials: N
authors.lastname: Zamzami
authors.forename: I
authors.initials: I
authors.lastname: Marzo
authors.forename: C
authors.initials: C
authors.lastname: Brenner
authors.forename: N
authors.initials: N
authors.lastname: Larochette
authors.forename: M C
authors.initials: MC
authors.lastname: Prévost
authors.forename: P M
authors.initials: PM
authors.lastname: Alzari
authors.forename: G
authors.initials: G
authors.lastname: Kroemer
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051033:Apoptosis Inducing Factor; D053143:Caspase 2; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D005260:Female; D005420:Flavoproteins; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008845:Microinjections; D008928:Mitochondria / Q000201:enzymology*; D009687:Nuclear Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D004792:Enzyme Precursors; D005420:Flavoproteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; C494830:AIFM1 protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse; D053143:Caspase 2; D053453:Caspase 9; D020169:Caspases