title: Bidirectional Ca2+-dependent control of mitochondrial dynamics by the Miro GTPase.
abstract: Calcium oscillations suppress mitochondrial movements along the microtubules to support on-demand distribution of mitochondria. To activate this mechanism, Ca(2+) targets a yet unidentified cytoplasmic factor that does not seem to be a microtubular motor or a kinase/phosphatase. Here, we have studied the dependence of mitochondrial dynamics on the Miro GTPases that reside in the mitochondria and contain two EF-hand Ca(2+)-binding domains, in H9c2 cells and primary neurons. At resting cytoplasmic [Ca(2+)] ([Ca(2+)](c)), movements of the mitochondria were enhanced by Miro overexpression irrespective of the presence of the EF-hands. The Ca(2+)-induced arrest of mitochondrial motility was also promoted by Miro overexpression and was suppressed when either the Miro were depleted or their EF-hand was mutated. Miro also enhanced the fusion state of the mitochondria at resting [Ca(2+)](c) but promoted mitochondrial fragmentation at high [Ca(2+)](c). These effects of Miro on mitochondrial morphology seem to involve Drp1 suppression and activation, respectively. In primary neurons, Miro also caused an increase in dendritic mitochondrial mass and enhanced mitochondrial calcium signaling. Thus, Miro proteins serve as a [Ca(2+)](c)-sensitive switch and bifunctional regulator for both the motility and fusion-fission dynamics of the mitochondria.
authors.affiliation: Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Masao
authors.initials: M
authors.lastname: Saotome
authors.forename: Dzhamilja
authors.initials: D
authors.lastname: Safiulina
authors.forename: György
authors.initials: G
authors.lastname: Szabadkai
authors.forename: Sudipto
authors.initials: S
authors.lastname: Das
authors.forename: Asa
authors.initials: A
authors.lastname: Fransson
authors.forename: Pontus
authors.initials: P
authors.lastname: Aspenstrom
authors.forename: Rosario
authors.initials: R
authors.lastname: Rizzuto
authors.forename: György
authors.initials: G
authors.lastname: Hajnóczky
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D003712:Dendrites / Q000235:genetics / Q000378:metabolism*; D034281:Dynamins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; C473124:RHOT1 protein, human; C473125:RHOT2 protein, human; D020741:rho GTP-Binding Proteins; C519851:Dnm1l protein, rat; D034281:Dynamins; D002118:Calcium