title: Mitochondria take up Ca2+ in two steps dependently on store-operated Ca2+ entry in mast cells.
abstract: The ability of mitochondria to take up Ca2+ has important functional implications for modulation of cellular Ca2+ signaling. Mitochondrial Ca2+ uptake is stimulated by an increase in cytosolic Ca2+ concentration ([Ca2+]c). Here, we found that the increase in mitochondrial Ca2+ concentration ([Ca2+]m) occurs in two steps in a single antigen-activated mast cell in the presence of extracellular Ca2+ (1.0 mM). The two-step elevation of [Ca2+]m was also observed after adding thapsigargin, an inhibitor of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase. The proportion of mitochondria showing the two-step Ca2+ elevation dropped off in direct accord with decrease in extracellular Ca2+ concentration. The second step of the [Ca2+]m increase was suppressed significantly in the absence of extracellular Ca2+ and in knockdown cells of stromal interaction molecule 1 (STIM1), an essential molecule on endoplasmic reticulum (ER) membrane for store-operated Ca2+ entry, in the presence of extracellular Ca2+ (1.0 mM), while the first elevation was not affected in either case. The results indicate that mitochondria take up cytosolic Ca2+ in two steps; first and second uptakes are derived from the Ca2+ release from ER and the Ca2+ influx through store-operated Ca2+ channels, respectively. Additionally, rotenone and antimycin A, which are inhibitors of mitochondrial electron transport complex I and III, respectively, diminished mitochondrial Ca2+ uptake and significantly suppressed degranulation stimulated with antigen. The mitochondrial Ca2+ uptake may modulate mast cell function by regulating the [Ca2+]c.
authors.affiliation: School of Pharmacy, Aichi Gakuin University, Nagoya, Japan.
authors.forename: Marie
authors.initials: M
authors.lastname: Takekawa
authors.forename: Tadahide
authors.initials: T
authors.lastname: Furuno
authors.forename: Naohide
authors.initials: N
authors.lastname: Hirashima
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nakanishi
mesh_terms: D000818:Animals; D000941:Antigens / Q000378:metabolism; D000968:Antimycin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D015550:Cell Degranulation; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004579:Electron Transport; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008407:Mast Cells / Q000378:metabolism* / Q000502:physiology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D051381:Rats; D012402:Rotenone / Q000494:pharmacology; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D000941:Antigens; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D012402:Rotenone; D000968:Antimycin A; D019284:Thapsigargin; D002118:Calcium