Mitochondrial clustering induced by overexpression of the mitochondrial fusion protein Mfn2 causes mitochondrial dysfunction and cell death.
Mitochondria change their shapes dynamically mainly through fission and fusion. Dynamin-related GTPases have been shown to mediate remodeling of mitochondrial membranes during these processes. One of these GTPases, mitofusin, is anchored at the outer mitochondrial membrane and mediates fusion of the outer membrane. We found that overexpression of a mitofusin isoform, Mfn2, drastically changes mitochondrial morphology, forming mitochondrial clusters. High-resolution microscopic examination indicated that the mitochondrial clusters consisted of small fragmented mitochondria. Inhibiting mitochondrial fission prevented the cluster formation, supporting the notion that mitochondrial clusters are formed by fission-mediated mitochondrial fragmentation and aggregation. Mitochondrial clusters displayed a decreased inner membrane potential and mitochondrial function, suggesting a functional compromise of small fragmented mitochondria produced by Mfn2 overexpression; however, mitochondrial clusters still retained mitochondrial DNA. We found that cells containing clustered mitochondria lost cytochrome c from mitochondria and underwent caspase-mediated apoptosis. These results demonstrate that mitochondrial deformation impairs mitochondrial function, leading to apoptotic cell death and suggest the presence of an intricate form-function relationship in mitochondria.
Huang
Pinwei
P
Department of Pharmacology and Physiology, University of Rochester, School of Medicine and Dentistry, 601 Elmwood Avenue, P.O. Box 604, Rochester, NY 14642, USA.
Yu
Tianzheng
T
Yoon
Yisang
Y
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D008099:Liver / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism* / Q000648:ultrastructure*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats
D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D045304:Cytochromes c; D020558:GTP Phosphohydrolases; C489710:Mfn2 protein, rat; C519851:Dnm1l protein, rat; D034281:Dynamins