title: A threshold of transmembrane potential is required for mitochondrial dynamic balance mediated by DRP1 and OMA1.
abstract: As an organellar network, mitochondria dynamically regulate their organization via opposing fusion and fission pathways to maintain bioenergetic homeostasis and contribute to key cellular pathways. This dynamic balance is directly linked to bioenergetic function: loss of transmembrane potential across the inner membrane (Δψm) disrupts mitochondrial fission/fusion balance, causing fragmentation of the network. However, the level of Δψmrequired for mitochondrial dynamic balance, as well as the relative contributions of fission and fusion pathways, have remained unclear. To explore this, mitochondrial morphology and Δψmwere examined via confocal imaging and tetramethyl rhodamine ester (TMRE) flow cytometry, respectively, in cultured 143B osteosarcoma cells. When normalized to the TMRE value of untreated 143B cells as 100%, both genetic (mtDNA-depleted ρ0) and pharmacological [carbonyl cyanide m-chlorophenyl hydrazone (CCCP)-treated] cell models below 34% TMRE fluorescence were unable to maintain mitochondrial interconnection, correlating with loss of fusion-active long OPA1 isoforms (L-OPA1). Mechanistically, this threshold is maintained by mechanistic coordination of DRP1-mediated fission and OPA1-mediated fusion: cells lacking either DRP1 or the OMA1 metalloprotease were insensitive to loss of Δψm, instead maintaining an obligately fused morphology. Collectively, these findings demonstrate a mitochondrial 'tipping point' threshold mediated by the interaction of Δψmwith both DRP1 and OMA1; moreover, DRP1 appears to be required for effective OPA1 maintenance and processing, consistent with growing evidence for direct interaction of fission and fusion pathways. These results suggest that Δψmbelow threshold coordinately activates both DRP1-mediated fission and OMA1 cleavage of OPA1, collapsing mitochondrial dynamic balance, with major implications for a range of signaling pathways and cellular life/death events.
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Edith
authors.initials: E
authors.lastname: Jones
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Norma
authors.initials: N
authors.lastname: Gaytan
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Iraselia
authors.initials: I
authors.lastname: Garcia
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Herrera
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Manuel
authors.initials: M
authors.lastname: Ramos
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Divya
authors.initials: D
authors.lastname: Agarwala
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Maahrose
authors.initials: M
authors.lastname: Rana
authors.affiliation: Department of Biomedical Sciences, The University of Texas Rio Grande Valley, Edinburg, TX, 78539-2999, USA.
authors.forename: Wendy
authors.initials: W
authors.lastname: Innis-Whitehouse
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: Schuenzel
authors.affiliation: Department of Biology, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA. robert.gilkerson@utrgv.edu.|Department of Clinical Laboratory Sciences, The University of Texas Rio Grande Valley, 1201 West University Drive, Edinburg, TX, 78539-2999, USA. robert.gilkerson@utrgv.edu.
authors.forename: Robert
authors.identifier: 0000-0002-5725-6627
authors.initials: R
authors.lastname: Gilkerson
mesh_terms: D000818:Animals; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D045744:Cell Line, Tumor; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D045325:HCT116 Cells; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D045726:Metalloproteases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D063154:Mitochondrial Dynamics / Q000187:drug effects; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction
chemical_list: D004272:DNA, Mitochondrial; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D045726:Metalloproteases; C572960:OMA1 protein, mouse; D020558:GTP Phosphohydrolases; C110768:DNM1L protein, human; D034281:Dynamins
keywords: Oxidative phosphorylation; Proteolytic cleavage; Protonophore; S-OPA1; mtDNA