Mitochondria regulate Ca2+ wave initiation and inositol trisphosphate signal transduction in oligodendrocyte progenitors

• Published in: Journal of neurochemistry 2002-02, Vol.80 (3), p.405-415
• Main Authors: Haak, Laurel L., Grimaldi, Maurizio, Smaili, Soraya S., Russell, James T.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Anti-Bacterial Agents - pharmacology; Antimycin A - pharmacology; Biological and medical sciences; Calcium - metabolism; Calcium Signaling - drug effects; Calcium Signaling - physiology; calcium wave; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - pharmacology; Clonazepam - analogs & derivatives; Clonazepam - pharmacology; Fundamental and applied biological sciences. Psychology; gelsolin; Gelsolin - metabolism; Inositol 1,4,5-Trisphosphate - metabolism; inositol trisphosphate; Isolated neuron and nerve. Neuroglia; Membrane Potentials - drug effects; Membrane Potentials - physiology; Methacholine Chloride - pharmacology; mitochondria; Mitochondria - metabolism; Muscarinic Antagonists - pharmacology; oligodendrocyte progenitor; Oligodendroglia - metabolism; Phosphatidylinositol 4,5-Diphosphate - metabolism; PIP2; Rats; Stem Cells - metabolism; Thiazepines - pharmacology; Uncoupling Agents - pharmacology; Vertebrates: nervous system and sense organs
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1046/j.0022-3042.2001.00727.x

Mitochondria in oligodendrocyte progenitor cells (OPs) take up and release cytosolic Ca2+ during agonist‐evoked Ca2+ waves, but it is not clear whether or how they regulate Ca2+ signaling in OPs. We asked whether mitochondria play an active role during agonist‐evoked Ca2+ release from intracellular stores. Ca2+ puffs, wave initiation, and wave propagation were measured in fluo‐4 loaded OP processes using linescan confocal microscopy. Mitochondrial depolarization, measured by tetramethyl rhodamine ethyl ester (TMRE) fluorescence, accompanied Ca2+ puffs and waves. In addition, waves initiated only where mitochondria were localized. To determine whether energized mitochondria were necessary for wave generation, we blocked mitochondrial function with the electron transport chain inhibitor antimycin A (AA) in combination with oligomycin. AA decreased wave speed and puff probability. These effects were not due to global changes in ATP. We found that AA increased cytosolic Ca2+, markedly reduced agonist‐evoked inositol trisphosphate (IP3) production, and also enhanced phosphatidylinositol 4,5‐bisphosphate (PIP2) binding to the Ca2+ dependent protein gelsolin. Thus, the reduction in puff probability and wave speed after AA treatment may be explained by competition for PIP2 between phospholipase C and gelsolin. Energized mitochondria and low cytosolic Ca2+ concentration may be required to maintain PIP2, a substrate for IP3 signal transduction.