Role of glycolytically generated ATP for CaMKII-mediated regulation of intracellular Ca2+ signaling in bovine vascular endothelial cells |
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Authors: | Aromolaran Ademuyiwa S Zima Aleksey V Blatter Lothar A |
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Institution: | Dept. of Physiology, Loyola University Chicago, 2160 S. First Ave., Maywood, IL 60153, USA. |
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Abstract: | The role of glycolytically generated ATP in Ca2+/calmodulin-dependent kinase II (CaMKII)-mediated regulation of intracellular Ca2+ signaling was examined in cultured calf pulmonary artery endothelial (CPAE) cells. Exposure of cells (extracellular Ca2+ concentration = 2 mM) to glycolytic inhibitors 2-deoxy-D-glucose (2-DG), pyruvate (pyr) + -hydroxybutyrate (-HB), or iodoacetic acid (IAA) caused an increase of intracellular Ca2+ concentration (Ca2+]i). CaMKII inhibitors (KN-93, W-7) triggered a similar increase of Ca2+]i. The rise of Ca2+]i was characterized by a transient spike followed by a small sustained plateau of elevated Ca2+]i. In the absence of extracellular Ca2+ 2-DG caused an increase in Ca2+]i, suggesting that inhibition of glycolysis directly triggered release of Ca2+ from intracellular endoplasmic reticulum (ER) Ca2+ stores. The inositol-1,4,5-trisphosphate receptor (IP3R) inhibitor 2-aminoethoxydiphenyl borate abolished the KN-93- and 2-DG-induced Ca2+ response. Ca2+ release was initiated in peripheral cytoplasmic processes from which activation propagated as a Ca2+]i wave toward the central region of the cell. Focal application of 2-DG resulted in spatially confined elevations of Ca2+]i. Propagating Ca2+]i waves were preceded by Ca2+]i oscillations and small, highly localized elevations of Ca2+]i (Ca2+ puffs). Inhibition of glycolysis with 2-DG reduced the KN-93-induced Ca2+ response, and vice versa during inhibition of CaMKII 2-DG-induced Ca2+ release was attenuated. Similar results were obtained with pyr + -HB and W-7. Furthermore, 2-DG and IAA caused a rapid increase of intracellular Mg2+ concentration, indicating a concomitant drop of cellular ATP levels. In conclusion, CaMKII exerts a profound inhibition of ER Ca2+ release in CPAE cells, which is mediated by glycolytically generated ATP, possibly through ATP-dependent phosphorylation of the IP3R. Ca2+/calmodulin-dependent kinase II; glycolysis; calcium regulation |
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