TY - JOUR
T1 - Mitochondria fine-tune the slow Ca2+ transients induced by electrical stimulation of skeletal myotubes
AU - Eisner, Veronica
AU - Parra, Valentina
AU - Lavandero, Sergio
AU - Hidalgo, Cecilia
AU - Jaimovich, Enrique
N1 - Funding Information:
The authors thank Monica Silva for cell culture preparation and Martin Pavarotti for initial studies of mitochondria Ca 2+ transients. We also acknowledge Dr. Rosario Rizzuto, Dr. Gyorgy Szabadkai and Dr. Katiusia Bianchi for their orientation in mito-pericam measurements and mitochondria dynamics studies. This work was supported by FONDECYT/FONDAP (Fondo de Areas Prioritarias, Chile) Grant 15010006 (S.L, C.H and E.J), FONDECYT Postdoctoral Grant 3070043 (V.E) and FONDECYT 1080120 . V.P. is a recipient of a PhD fellowship from CONICYT, Chile. S.L is on a sabbatical leave at the University of Texas Southwestern Medical Center, Dallas, Texas, USA.
PY - 2010/12
Y1 - 2010/12
N2 - Mitochondria sense cytoplasmic Ca2+ signals in many cell types. In mammalian skeletal myotubes, depolarizing stimuli induce two independent cytoplasmic Ca2+ 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 Ca2+ signals has not been reported. We investigated here (a) the emergence of mitochondrial Ca2+ signals in response to electrical stimulation of myotubes, (b) the contribution of mitochondrial Ca2+ transients to ATP generation and (c) the influence of mitochondria as modulators of cytoplasmic and nuclear Ca2+ signals. Rhod2 and Fluo3 fluorescence determinations revealed composite Ca2+ signals associated to the mitochondrial compartment in electrically stimulated (400 pulses, 45Hz) skeletal myotubes. Similar Ca2+ signals were detected when using a mitochondria-targeted pericam. The fast mitochondrial Ca2+ rise induced by stimulation was inhibited by pre-incubation with ryanodine, whereas the phospholipase C inhibitor U73122 blocked the slow mitochondrial Ca2+ signal, showing that mitochondria sense the two cytoplasmic Ca2+ signal components. The fast but not the slow Ca2+ transient enhanced mitochondrial ATP production. Inhibition of the mitochondrial Ca2+ uniporter prevented the emergence of mitochondrial Ca2+ transients and significantly increased the magnitude of slow cytoplasmic Ca2+ signals after stimulation. Precluding mitochondrial Ca2+ extrusion with the Na+/Ca2+ exchanger inhibitor CGP37157 decreased mitochondrial potential, increased the magnitude of the slow cytoplasmic Ca2+ signal and decreased the rate of Ca2+ signal propagation from one nucleus to the next. Over expression of the mitochondrial fission protein Drp-1 decreased mitochondrial size and the slow Ca2+ transient in mitochondria, but enhanced cytoplasmic and nuclear slow transients. The present results indicate that mitochondria play a central role in the regulation of Ca2+ signals involved in gene expression in myotubes.
AB - Mitochondria sense cytoplasmic Ca2+ signals in many cell types. In mammalian skeletal myotubes, depolarizing stimuli induce two independent cytoplasmic Ca2+ 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 Ca2+ signals has not been reported. We investigated here (a) the emergence of mitochondrial Ca2+ signals in response to electrical stimulation of myotubes, (b) the contribution of mitochondrial Ca2+ transients to ATP generation and (c) the influence of mitochondria as modulators of cytoplasmic and nuclear Ca2+ signals. Rhod2 and Fluo3 fluorescence determinations revealed composite Ca2+ signals associated to the mitochondrial compartment in electrically stimulated (400 pulses, 45Hz) skeletal myotubes. Similar Ca2+ signals were detected when using a mitochondria-targeted pericam. The fast mitochondrial Ca2+ rise induced by stimulation was inhibited by pre-incubation with ryanodine, whereas the phospholipase C inhibitor U73122 blocked the slow mitochondrial Ca2+ signal, showing that mitochondria sense the two cytoplasmic Ca2+ signal components. The fast but not the slow Ca2+ transient enhanced mitochondrial ATP production. Inhibition of the mitochondrial Ca2+ uniporter prevented the emergence of mitochondrial Ca2+ transients and significantly increased the magnitude of slow cytoplasmic Ca2+ signals after stimulation. Precluding mitochondrial Ca2+ extrusion with the Na+/Ca2+ exchanger inhibitor CGP37157 decreased mitochondrial potential, increased the magnitude of the slow cytoplasmic Ca2+ signal and decreased the rate of Ca2+ signal propagation from one nucleus to the next. Over expression of the mitochondrial fission protein Drp-1 decreased mitochondrial size and the slow Ca2+ transient in mitochondria, but enhanced cytoplasmic and nuclear slow transients. The present results indicate that mitochondria play a central role in the regulation of Ca2+ signals involved in gene expression in myotubes.
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U2 - 10.1016/j.ceca.2010.11.001
DO - 10.1016/j.ceca.2010.11.001
M3 - Article
AN - SCOPUS:78649714687
SN - 0143-4160
VL - 48
SP - 358
EP - 370
JO - Cell Calcium
JF - Cell Calcium
IS - 6
ER -