Mitochondrial release of apoptosis-inducing factor occurs downstream of cytochrome c release in response to several proapoptotic stimuli.
Mitochondrial outer membrane permeabilization by proapoptotic Bcl-2 family proteins, such as Bax, plays a crucial role in apoptosis induction. However, whether this only causes the intracytosolic release of inducers of caspase-dependent death, such as cytochrome c, or also of caspase-independent death, such as apoptosis-inducing factor (AIF) remains unknown. Here, we show that on isolated mitochondria, Bax causes the release of cytochrome c, but not of AIF, and the association of AIF with the mitochondrial inner membrane provides a simple explanation for its lack of release upon Bax-mediated outer membrane permeabilization. In cells overexpressing Bax or treated either with the Bax- or Bak-dependent proapoptotic drugs staurosporine or actinomycin D, or with hydrogen peroxide, caspase inhibitors did not affect the intracytosolic translocation of cytochrome c, but prevented that of AIF. These results provide a paradigm for mitochondria-dependent death pathways in which AIF cannot substitute for caspase executioners because its intracytosolic release occurs downstream of that of cytochrome c.
Arnoult
Damien
D
EMI-U 9922 Institut National de la Santé et de la Recherche Medicale (INSERM)/Université Paris 7, IFR02, AP-HP, CHU Bichat, 75018 Paris, France. ArnoultD@ninds.nih.gov
Parone
Philippe
P
Martinou
Jean-Claude
JC
Antonsson
Bruno
B
Estaquier
Jerome
J
Ameisen
Jean Claude
JC
D000818:Animals; D017209:Apoptosis; D051033:Apoptosis Inducing Factor; D015153:Blotting, Western; D061945:Caspase Inhibitors; D016923:Cell Death; D002460:Cell Line; D003574:Cytochrome c Group / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005420:Flavoproteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection; D051028:bcl-2-Associated X Protein
C494829:AIFM1 protein, human; C494831:Aifm1 protein, rat; D051033:Apoptosis Inducing Factor; C494826:BAX protein, human; C494828:Bax protein, rat; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D005420:Flavoproteins; D008565:Membrane Proteins; D011500:Protein Synthesis Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D003609:Dactinomycin; D006861:Hydrogen Peroxide; D003576:Electron Transport Complex IV