Mitochondria fine-tune the slow Ca 2+ transients induced by electrical stimulation of skeletal myotubes

Eisner V.; Parra, V; Lavandero S.; Hidalgo C.; Jaimovich E.

Keywords: kinetics, stimulation, muscle, rat, size, membrane, overexpression, animals, expression, ion, rats, protein, cell, gene, ryanodine, proton, calcium, mitochondrion, synthase, transduction, regulation, sodium, newborn, tissue, compartmentalization, signal, drug, adenosine, pyrrole, article, mitochondrial, mammalia, dye, signaling, skeletal, controlled, fluorescent, animal, study, 1, 3, priority, nonhuman, journal, triphosphate, transporting, 2, 1h, 2,5, potential, Cells,, Cultured, Electric, (3, unclassified, electrostimulation, myotube, Mitochondria,, Fibers,, [[6, methoxyestra, 1,3,5(10), trien, 17beta, yl)amino]hexyl], dione, fluo, proetin, drp1, rhod

Abstract

Mitochondria sense cytoplasmic Ca 2+ signals in many cell types. In mammalian skeletal myotubes, depolarizing stimuli induce two independent cytoplasmic Ca 2+ signals: a fast signal associated with contraction and a slow signal that propagates to the nucleus and regulates gene expression. How mitochondria sense and possibly affect these cytoplasmic Ca 2+ signals has not been reported. We investigated here (a) the emergence of mitochondrial Ca 2+ signals in response to electrical stimulation of myotubes, (b) the contribution of mitochondrial Ca 2+ transients to ATP generation and (c) the influence of mitochondria as modulators of cytoplasmic and nuclear Ca 2+ signals. Rhod2 and Fluo3 fluorescence determinations revealed composite Ca 2+ signals associated to the mitochondrial compartment in electrically stimulated (400 pulses, 45Hz) skeletal myotubes. Similar Ca 2+ signals were detected when using a mitochondria-targeted pericam. The fast mitochondrial Ca 2+ rise induced by stimulation was inhibited by pre-incubation with ryanodine, whereas the phospholipase C inhibitor U73122 blocked the slow mitochondrial Ca 2+ signal, showing that mitochondria sense the two cytoplasmic Ca 2+ signal components. The fast but not the slow Ca 2+ transient enhanced mitochondrial ATP production. Inhibition of the mitochondrial Ca 2+ uniporter prevented the emergence of mitochondrial Ca 2+ transients and significantly increased the magnitude of slow cytoplasmic Ca 2+ signals after stimulation. Precluding mitochondrial Ca 2+ extrusion with the Na +/Ca 2+ exchanger inhibitor CGP37157 decreased mitochondrial potential, increased the magnitude of the slow cytoplasmic Ca 2+ signal and decreased the rate of Ca 2+ signal propagation from one nucleus to the next. Over expression of the mitochondrial fission protein Drp-1 decreased mitochondrial size and the slow Ca 2+ transient in mitochondria, but enhanced cytoplasmic and nuclear slow transients. The present results indicate that mitochondria play a central role in the regulation of Ca 2+ signals involved in gene expression in myotubes. © 2010 Elsevier Ltd.

Más información

Título de la Revista: CELL CALCIUM
Volumen: 48
Número: 6
Editorial: ELSEVIER SCI LTD
Fecha de publicación: 2010
Página de inicio: 358
Página final: 370
URL: http://www.scopus.com/inward/record.url?eid=2-s2.0-78649714687&partnerID=q2rCbXpz