1. Fission and selective fusion govern mitochondrial segregation and elimination by autophagy.
- Author
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Twig G, Elorza A, Molina AJ, Mohamed H, Wikstrom JD, Walzer G, Stiles L, Haigh SE, Katz S, Las G, Alroy J, Wu M, Py BF, Yuan J, Deeney JT, Corkey BE, and Shirihai OS
- Subjects
- Animals, Autophagy genetics, Autophagy-Related Protein 5, Cell Line, GTP Phosphohydrolases genetics, GTP Phosphohydrolases metabolism, Genotype, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Insulin metabolism, Insulin Secretion, Insulin-Secreting Cells cytology, Insulin-Secreting Cells metabolism, Male, Membrane Potential, Mitochondrial physiology, Mice, Mice, Inbred C57BL, Microscopy, Confocal, Microtubule-Associated Proteins genetics, Microtubule-Associated Proteins physiology, Mitochondria metabolism, Mitochondrial Proteins genetics, Mitochondrial Proteins metabolism, Models, Biological, Mutation, Reactive Oxygen Species metabolism, Autophagy physiology, Mitochondria physiology, Mitochondrial Proteins physiology
- Abstract
Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative damage and development of diabetes. To determine the source and fate of depolarized mitochondria, individual mitochondria were photolabeled and tracked through fusion and fission. Mitochondria were found to go through frequent cycles of fusion and fission in a 'kiss and run' pattern. Fission events often generated uneven daughter units: one daughter exhibited increased membrane potential (delta psi(m)) and a high probability of subsequent fusion, while the other had decreased membrane potential and a reduced probability for a fusion event. Together, this pattern generated a subpopulation of non-fusing mitochondria that were found to have reduced delta psi(m) and decreased levels of the fusion protein OPA1. Inhibition of the fission machinery through DRP1(K38A) or FIS1 RNAi decreased mitochondrial autophagy and resulted in the accumulation of oxidized mitochondrial proteins, reduced respiration and impaired insulin secretion. Pulse chase and arrest of autophagy at the pre-proteolysis stage reveal that before autophagy mitochondria lose delta psi(m) and OPA1, and that overexpression of OPA1 decreases mitochondrial autophagy. Together, these findings suggest that fission followed by selective fusion segregates dysfunctional mitochondria and permits their removal by autophagy.
- Published
- 2008
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