Identification of a ryanodine receptor in rat heart mitochondria.
Recent studies have shown that, in a wide variety of cells, mitochondria respond dynamically to physiological changes in cytosolic Ca(2+) concentrations ([Ca(2+)](c)). Mitochondrial Ca(2+) uptake occurs via a ruthenium red-sensitive calcium uniporter and a rapid mode of Ca(2+) uptake. Surprisingly, the molecular identity of these Ca(2+) transport proteins is still unknown. Using electron microscopy and Western blotting, we identified a ryanodine receptor in the inner mitochondrial membrane with a molecular mass of approximately 600 kDa in mitochondria isolated from the rat heart. [(3)H]Ryanodine binds to this mitochondrial ryanodine receptor with high affinity. This binding is modulated by Ca(2+) but not caffeine and is inhibited by Mg(2+) and ruthenium red in the assay medium. In the presence of ryanodine, Ca(2+) uptake into isolated heart mitochondria is suppressed. In addition, ryanodine inhibited mitochondrial swelling induced by Ca(2+) overload. This swelling effect was not observed when Ca(2+) was applied to the cytosolic fraction containing sarcoplasmic reticulum. These results are the first to identify a mitochondrial Ca(2+) transport protein that has characteristics similar to the ryanodine receptor. This mitochondrial ryanodine receptor is likely to play an essential role in the dynamic uptake of Ca(2+) into mitochondria during Ca(2+) oscillations.
Beutner
G
G
Department of Pharmacology and Physiology, University of Rochester, School of Medicine and Dentistry, Rochester, New York 14642, USA.
Sharma
V K
VK
Giovannucci
D R
DR
Yule
D I
DI
Sheu
S S
SS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D007425:Intracellular Membranes / Q000502:physiology / Q000648:ultrastructure; D007700:Kinetics; D016253:Microscopy, Immunoelectron; D008929:Mitochondria, Heart / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008933:Mitochondrial Swelling / Q000187:drug effects / Q000502:physiology; D008954:Models, Biological; D011869:Radioligand Assay; D051381:Rats; D012433:Ryanodine / Q000493:pharmacokinetics / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000032:analysis / Q000502:physiology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium