Apoptosis-inducing factor is involved in the regulation of caspase-independent neuronal cell death.
Caspase-independent death mechanisms have been shown to execute apoptosis in many types of neuronal injury. P53 has been identified as a key regulator of neuronal cell death after acute injury such as DNA damage, ischemia, and excitotoxicity. Here, we demonstrate that p53 can induce neuronal cell death via a caspase-mediated process activated by apoptotic activating factor-1 (Apaf1) and via a delayed onset caspase-independent mechanism. In contrast to wild-type cells, Apaf1-deficient neurons exhibit delayed DNA fragmentation and only peripheral chromatin condensation. More importantly, we demonstrate that apoptosis-inducing factor (AIF) is an important factor involved in the regulation of this caspase-independent neuronal cell death. Immunofluorescence studies demonstrate that AIF is released from the mitochondria by a mechanism distinct from that of cytochrome-c in neurons undergoing p53-mediated cell death. The Bcl-2 family regulates this release of AIF and subsequent caspase-independent cell death. In addition, we show that enforced expression of AIF can induce neuronal cell death in a Bax- and caspase-independent manner. Microinjection of neutralizing antibodies against AIF significantly decreased injury-induced neuronal cell death in Apaf1-deficient neurons, indicating its importance in caspase-independent apoptosis. Taken together, our results suggest that AIF may be an important therapeutic target for the treatment of neuronal injury.
Cregan
Sean P
SP
Ottawa Health Research Institute, Department of Neuroscience, University of Ottawa, Ontario, Canada, K1H 8M5.
Fortin
Andre
A
MacLaurin
Jason G
JG
Callaghan
Steven M
SM
Cecconi
Francesco
F
Yu
Seong-Woon
SW
Dawson
Ted M
TM
Dawson
Valina L
VL
Park
David S
DS
Kroemer
Guido
G
Slack
Ruth S
RS
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D051033:Apoptosis Inducing Factor; D053477:Apoptotic Protease-Activating Factor 1; D001921:Brain / Q000166:cytology / Q000196:embryology* / Q000201:enzymology; D002166:Camptothecin / Q000494:pharmacology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D005787:Gene Frequency / Q000502:physiology; D020287:In Situ Nick-End Labeling; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D019636:Neurodegenerative Diseases / Q000188:drug therapy / Q000201:enzymology* / Q000503:physiopathology; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein
D000906:Antibodies; C506593:Apaf1 protein, mouse; D051033:Apoptosis Inducing Factor; D053477:Apoptotic Protease-Activating Factor 1; C494827:Bax protein, mouse; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D005420:Flavoproteins; D008565:Membrane Proteins; C494830:AIFM1 protein, mouse; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D020169:Caspases; D002166:Camptothecin