The mitochondrial inner membrane GTPase, optic atrophy 1 (Opa1), restores mitochondrial morphology and promotes neuronal survival following excitotoxicity.
Mitochondrial dynamics have been extensively studied in the context of classical cell death models involving Bax-mediated cytochrome c release. Excitotoxic neuronal loss is a non-classical death signaling pathway that occurs following overactivation of glutamate receptors independent of Bax activation. Presently, the role of mitochondrial dynamics in the regulation of excitotoxicity remains largely unknown. Here, we report that NMDA-induced excitotoxicity results in defects in mitochondrial morphology as evident by the presence of excessive fragmented mitochondria, cessation of mitochondrial fusion, and cristae dilation. Up-regulation of the mitochondrial inner membrane GTPase, Opa1, is able to restore mitochondrial morphology and protect neurons against excitotoxic injury. Opa1 functions downstream of the calcium-dependent protease, calpain. Inhibition of calpain activity by calpastatin, an endogenous calpain inhibitor, significantly rescued mitochondrial defects and maintained neuronal survival. Opa1 was required for calpastatin-mediated neuroprotection because the enhanced survival found following NMDA-induced toxicity was significantly reduced upon loss of Opa1. Our results define a mechanism whereby breakdown of the mitochondrial network mediated through loss of Opa1 function contributes to neuronal death following excitotoxic neuronal injury. These studies suggest Opa1 as a potential therapeutic target to promote neuronal survival following acute brain damage and neurodegenerative diseases.
Department of Cellular and Molecular Medicine, University of Ottawa Heart Institute, University of Ottawa, Ontario K1H 8M5, Canada.
Arezu
A
Jahani-Asl
Karine
K
Pilon-Larose
William
W
Xu
Jason G
JG
MacLaurin
David S
DS
Park
Heidi M
HM
McBride
Ruth S
RS
Slack
D000818:Animals; D001930:Brain Injuries / Q000235:genetics / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism*; D003603:Cytotoxins / Q000009:adverse effects / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000009:adverse effects / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D016202:N-Methylaspartate / Q000009:adverse effects / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D019636:Neurodegenerative Diseases / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*
D003603:Cytotoxins; D018690:Excitatory Amino Acid Agonists; D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; D016202:N-Methylaspartate; D020558:GTP Phosphohydrolases; C498809:Opa1 protein, mouse