부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ceca.2006.05.001 Byline: R. Malli (a), M. Frieden (b), M. Hunkova (a), M. Trenker (a), W.F. Graier (a) Keywords: Cameleon; Endoplasmic reticulum Ca.sup.2+ refilling; Membrane depolarization; Mitochondrial Ca.sup.2+; Pericam; Store-operated Ca.sup.2+ entry Abbreviations: BHQ, 2,5-di-tert-butylhydroquinone; [Ca.sup.2+].sub.cyto, free cytosolic Ca.sup.2+ concentration; [Ca.sup.2+].sub.er, free intraluminal ER Ca.sup.2+ concentration; [Ca.sup.2+].sub.mito, free mitochondrial Ca.sup.2+ concentration; SOCE, store-operated Ca.sup.2+ entry; ER, endoplasmic reticulum; IP.sub.3, inositol 1,4,5-triphosphate; NCX.sub.pm, plasma membrane Na.sup.+/Ca.sup.2+ exchanger; RP-mt, mitochondrial targeted ratiometric pericam; PMCA, plasma membrane-Ca.sup.2+ ATPase(s); SERCA, sarcoplasmic/endoplasmic reticulum Ca.sup.2+ pumps; vYC4er, ER-targeted venus cameleon 4 Abstract: In this study the relationship between the efficiency of endoplasmic reticulum (ER) Ca.sup.2+ refilling and the extent of Ca.sup.2+ entry was investigated in endothelial cells. ER and mitochondrial Ca.sup.2+ concentration were measured using genetically encoded Ca.sup.2+ sensors, while the amount of entering Ca.sup.2+ was controlled by varying either the extracellular Ca.sup.2+ or the electrical driving force for Ca.sup.2+ by changing the plasma membrane potential. In the absence of an agonist, ER Ca.sup.2+ replenishment was fully accomplished even if the Ca.sup.2+ concentration applied was reduced from 2 to 0.5mM. A similar strong efficiency of ER Ca.sup.2+ refilling was obtained under condition of plasma membrane depolarization. However, in the presence of histamine, ER Ca.sup.2+ refilling depended on mitochondrial Ca.sup.2+ transport and was more susceptible to membrane depolarization. Store-operated Ca.sup.2+ entry (SOCE), was strongly reduced under low Ca.sup.2+ and depolarizing conditions but increased if ER Ca.sup.2+ uptake was blocked or if ER Ca.sup.2+ was released continuously by IP.sub.3. A correlation of the kinetics of ER Ca.sup.2+ refilling with cytosolic Ca.sup.2+ signals revealed that termination of SOCE is a rapid event that is not delayed compared to ER refilling. Our data indicate that ER refilling occurs in priority to, and independently from the cytosolic Ca.sup.2+ elevation upon Ca.sup.2+ entry and that this important process is widely achieved even under conditions of diminished Ca.sup.2+ entry. Author Affiliation: (a) Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Molecular and Cellular Physiology Research Unit (MCPRU), Medical University Graz, Harrachgasse 21/III, A-8010 Graz, Austria (b) Department of Cell Physiology and Metabolism, University of Geneva, Medical Center, 1211 Geneva 4, Switzerland Article History: Accepted 1 May 2006