L-OPA1 regulates mitoflash biogenesis independently from membrane fusion.
Mitochondrial flashes mediated by optic atrophy 1 (OPA1) fusion protein are bioenergetic responses to stochastic drops in mitochondrial membrane potential (Δψm) whose origin is unclear. Using structurally distinct genetically encoded pH-sensitive probes, we confirm that flashes are matrix alkalinization transients, thereby establishing the pH nature of these events, which we renamed "mitopHlashes". Probes located in cristae or intermembrane space as verified by electron microscopy do not report pH changes during Δψmdrops or respiratory chain inhibition.Opa1ablation does not alter Δψmfluctuations but drastically decreases the efficiency of mitopHlash/Δψmcoupling, which is restored by re-expressing fusion-deficient OPA1K301Aand preserved in cells lacking the outer-membrane fusion proteins MFN1/2 or the OPA1 proteases OMA1 and YME1L, indicating that mitochondrial membrane fusion and OPA1 proteolytic processing are dispensable. pH/Δψmuncoupling occurs early during staurosporine-induced apoptosis and is mitigated by OPA1 overexpression, suggesting that OPA1 maintains mitopHlash competence during stress conditions. We propose that OPA1 stabilizes respiratory chain supercomplexes in a conformation that enables respiring mitochondria to compensate a drop in Δψmby an explosive matrix pH flash.
Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
Manon
M
Rosselin
Nestlé Institute of Health Sciences SA, EPFL Innovation Park, Lausanne, Switzerland.
Jaime
J
Santo-Domingo
Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
Flavien
F
Bermont
Department of Biology, University of Padova, Padova, Italy.
Marta
M
Giacomello
Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland nicolas.demaurex@unige.ch.
Nicolas
0000-0002-9933-6772
N
Demaurex
D017209:Apoptosis; D015374:Biosensing Techniques; D034281:Dynamins / Q000235:genetics / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008561:Membrane Fusion; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D063154:Mitochondrial Dynamics; D051336:Mitochondrial Membranes / Q000378:metabolism*; D059748:Proteolysis
D005047:Etoposide; D006861:Hydrogen Peroxide; D020558:GTP Phosphohydrolases; C415198:OPA1 protein, human; D034281:Dynamins
OPA1; bioenergetics; membrane fusion; mitoflash