title: Calcium signal transmission between ryanodine receptors and mitochondria.
abstract: Control of energy metabolism by increases of mitochondrial matrix [Ca(2+)] ([Ca(2+)](m)) may represent a fundamental mechanism to meet the ATP demand imposed by heart contractions, but the machinery underlying propagation of [Ca(2+)] signals from ryanodine receptor Ca(2+) release channels (RyR) to the mitochondria remains elusive. Using permeabilized cardiac (H9c2) cells we investigated the cytosolic [Ca(2+)] ([Ca(2+)](c)) and [Ca(2+)](m) signals elicited by activation of RyR. Caffeine, Ca(2+), and ryanodine evoked [Ca(2+)](c) spikes that often appeared as frequency-modulated [Ca(2+)](c) oscillations in these permeabilized cells. Rapid increases in [Ca(2+)](m) and activation of the Ca(2+)-sensitive mitochondrial dehydrogenases were synchronized to the rising phase of the [Ca(2+)](c) spikes. The RyR-mediated elevations of global [Ca(2+)](c) were in the submicromolar range, but the rate of [Ca(2+)](m) increases was as large as it was in the presence of 30 microm global [Ca(2+)](c). Furthermore, RyR-dependent increases of [Ca(2+)](m) were relatively insensitive to buffering of [Ca(2+)](c) by EGTA. Therefore, RyR-driven rises of [Ca(2+)](m) appear to result from large and rapid increases of perimitochondrial [Ca(2+)]. The falling phase of [Ca(2+)](c) spikes was followed by a rapid decay of [Ca(2+)](m). CGP37157 slowed down relaxation of [Ca(2+)](m) spikes, whereas cyclosporin A had no effect, suggesting that activation of the mitochondrial Ca(2+) exchangers accounts for rapid reversal of the [Ca(2+)](m) response with little contribution from the permeability transition pore. Thus, rapid activation of Ca(2+) uptake sites and Ca(2+) exchangers evoked by RyR-mediated local [Ca(2+)](c) signals allow mitochondria to respond rapidly to single [Ca(2+)](c) spikes in cardiac cells.
authors.affiliation: Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: G
authors.initials: G
authors.lastname: Szalai
authors.forename: G
authors.initials: G
authors.lastname: Csordás
authors.forename: B M
authors.initials: BM
authors.lastname: Hantash
authors.forename: A P
authors.initials: AP
authors.lastname: Thomas
authors.forename: G
authors.initials: G
authors.lastname: Hajnóczky
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D020746:Calcium Channels, L-Type / Q000502:physiology; D002460:Cell Line; D002463:Cell Membrane Permeability; D002998:Clonazepam / Q000031:analogs & derivatives / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D008929:Mitochondria, Heart / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology; D009206:Myocardium / Q000166:cytology; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D015398:Signal Transduction; D013841:Thiazepines / Q000494:pharmacology; D014162:Transfection
chemical_list: D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel; D013841:Thiazepines; D009243:NAD; D012433:Ryanodine; D002110:Caffeine; D004533:Egtazic Acid; D009249:NADP; D002998:Clonazepam; C079032:CGP 37157; D002118:Calcium