title: Single channel characterization of the mitochondrial ryanodine receptor in heart mitoplasts.
abstract: Heart mitochondria utilize multiple Ca(2+) transport mechanisms. Among them, the mitochondrial ryanodine receptor provides a fast Ca(2+) uptake pathway across the inner membrane to control "excitation and metabolism coupling." In the present study, we identified a novel ryanodine-sensitive channel in the native inner membrane of heart mitochondria and characterized its pharmacological and biophysical properties by directly patch clamping mitoplasts. Four distinct channel conductances of ∼100, ∼225, ∼700, and ∼1,000 picosiemens (pS) in symmetrical 150 mm CsCl were observed. The 225 pS cation-selective channel exhibited multiple subconductance states and was blocked by high concentrations of ryanodine and ruthenium red, known inhibitors of ryanodine receptors. Ryanodine exhibited a concentration-dependent modulation of this channel, with low concentrations stabilizing a subconductance state and high concentrations abolishing activity. The 100, 700, and 1,000 pS conductances exhibited different channel characteristics and were not inhibited by ryanodine. Taken together, these findings identified a novel 225 pS channel as the native mitochondrial ryanodine receptor channel activity in heart mitoplasts with biophysical and pharmacological properties that distinguish it from previously identified mitochondrial ion channels.
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA.
authors.forename: Shin-Young
authors.initials: SY
authors.lastname: Ryu
authors.forename: Gisela
authors.initials: G
authors.lastname: Beutner
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Kinnally
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dirksen
authors.forename: Shey-Shing
authors.initials: SS
authors.lastname: Sheu
mesh_terms: D000818:Animals; D001703:Biophysics / Q000379:methods; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002412:Cations; D002586:Cesium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004594:Electrophysiology / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D008929:Mitochondria, Heart / Q000378:metabolism*; D008954:Models, Biological; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D002412:Cations; D002712:Chlorides; D019837:Ryanodine Receptor Calcium Release Channel; D002586:Cesium; C028019:cesium chloride; D002118:Calcium