Functional characterization of the Ca(2+)-gated Ca2+ release channel of vascular smooth muscle sarcoplasmic reticulum.
The Ca(2+)-gated Ca2+ release channel of aortic sarcoplasmic reticulum (SR) was partially purified and reconstituted into planar lipid bilayers. Canine and porcine aorta microsomal protein fractions were solubilized in the detergent 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propane sulphonate (CHAPS) in the presence and absence of 3[H]-ryanodine and centrifuged through linear sucrose gradients. A single 3[H]-ryanodine receptor peak with an apparent sedimentation coefficient of 30 s was obtained. Upon reconstitution into planar lipid bilayers, the unlabelled 30 s protein fraction induced the formation of a Ca(2+)- and monovalent-ion-conducting channel (110 pS in 100 mM Ca2+, 360 pS in 250 mM K+). The channel was activated by micromolar Ca2+, modulated by millimolar adenosine triphosphate, Mg2+ and the Ca(2+)-releasing drug caffeine, and inhibited by micromolar ruthenium red. Micro- to millimolar concentrations of the plant alkaloid ryanodine induced a permanently closed state of the channel. Our results suggest that smooth muscle SR contains a Ca(2+)-gated Ca2+ release pathway, with properties similar to those observed for the skeletal and cardiac ryanodine receptor/Ca2+ release channel complexes.
Herrmann-Frank
A
A
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill 27599-7260.
Darling
E
E
Meissner
G
G
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000502:physiology; D004285:Dogs; D004553:Electric Conductivity / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects*; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000648:ultrastructure; D011122:Polyphosphates / Q000494:pharmacology; D012428:Ruthenium / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D013552:Swine
D015220:Calcium Channels; D011122:Polyphosphates; D002110:Caffeine; D012428:Ruthenium; D008274:Magnesium; C005692:triphosphoric acid; D002118:Calcium