Fission and selective fusion govern mitochondrial segregation and elimination by autophagy.
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.
Twig
Gilad
G
Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA.
Elorza
Alvaro
A
Molina
Anthony J A
AJ
Mohamed
Hibo
H
Wikstrom
Jakob D
JD
Walzer
Gil
G
Stiles
Linsey
L
Haigh
Sarah E
SE
Katz
Steve
S
Las
Guy
G
Alroy
Joseph
J
Wu
Min
M
Py
Bénédicte F
BF
Yuan
Junying
J
Deeney
Jude T
JT
Corkey
Barbara E
BE
Shirihai
Orian S
OS
D000818:Animals; D001343:Autophagy / Q000235:genetics / Q000502:physiology*; D000071187:Autophagy-Related Protein 5; D002460:Cell Line; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D017382:Reactive Oxygen Species / Q000378:metabolism
C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D007328:Insulin; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; D049452:Green Fluorescent Proteins; D020558:GTP Phosphohydrolases; C498809:Opa1 protein, mouse