期刊
JOURNAL OF PHYSIOLOGY-LONDON
卷 560, 期 1, 页码 63-76出版社
WILEY
DOI: 10.1113/jphysiol.2004.064063
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Mitochondria play an important role in the homeostasis of intracellular Ca2+ and regulate its availability for exocytosis. Inhibitors of mitochondria Ca2+ uptake such as protonophore CCCP potentiate the secretory response to a depolarizing pulse of K+. Exposure of cells to agents that directly (cytochalasin D, latrunculin B) or indirectly (PMA) disrupt cortical F-actin networks also potentiate the secretory response to high K+. The effects of cytochalasin D and CCCP on secretion were additive whereas those of PMU and CCCP were not; this suggests different mechanisms for cytochalasin D and CCCP and a similar mechanism for PMA and CCCR. Mitochondria were the site of action of CCCP, because the potentiation of secretion by CCCP was observed even after depletion of Ca2+ from the endoplasmic reticulum. CCCP induced a small increase in the cytosolic Ca2+ concentration ([Ca2+](c)) that was not modified by the protein kinase C (PKC) inhibitor chelerythrine. Both CCCP and PMA induced cortical F-actin disassembly, an effect abolished by chelerythrine. In addition, rotenone and oligomycin A, two other mitochondrial inhibitors, also evoked cortical F-actin disassembly and potentiated secretion; again, these effects were blocked by chelerythrine. CCCP also enhanced the phosphorylation of PKC and myristoylated alanine-rich C kinase substance (MARCKS), and these were also inhibited by chelerythrine. The results suggest that the rapid sequestration of Ca2+ by mitochondria would protect the cell from an enhanced PKC activation and cortical F-actin disassembly, thereby limiting the magnitude of the secretory response.
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