title: Genetic ablation of caveolin-1 modifies Ca2+ spark coupling in murine arterial smooth muscle cells.
abstract: L-type, voltage-dependent calcium (Ca(2+)) channels, ryanodine-sensitive Ca(2+) release (RyR) channels, and large-conductance Ca(2+)-activated potassium (K(Ca)) channels comprise a functional unit that regulates smooth muscle contractility. Here, we investigated whether genetic ablation of caveolin-1 (cav-1), a caveolae protein, alters Ca(2+) spark to K(Ca) channel coupling and Ca(2+) spark regulation by voltage-dependent Ca(2+) channels in murine cerebral artery smooth muscle cells. Caveolae were abundant in the sarcolemma of control (cav-1(+/+)) cells but were not observed in cav-1-deficient (cav-1(-/-)) cells. Ca(2+) spark and transient K(Ca) current frequency were approximately twofold higher in cav-1(-/-) than in cav-1(+/+) cells. Although voltage-dependent Ca(2+) current density was similar in cav-1(+/+) and cav-1(-/-) cells, diltiazem and Cd(2+), voltage-dependent Ca(2+) channel blockers, reduced transient K(Ca) current frequency to approximately 55% of control in cav-1(+/+) cells but did not alter transient K(Ca) current frequency in cav-1(-/-) cells. Furthermore, although K(Ca) channel density was elevated in cav-1(-/-) cells, transient K(Ca) current amplitude was similar to that in cav-1(+/+) cells. Higher Ca(2+) spark frequency in cav-1(-/-) cells was not due to elevated intracellular Ca(2+) concentration, sarcoplasmic reticulum Ca(2+) load, or nitric oxide synthase activity. Similarly, Ca(2+) spark amplitude and spread, the percentage of Ca(2+) sparks that activated a transient K(Ca) current, the amplitude relationship between sparks and transient K(Ca) currents, and K(Ca) channel conductance and apparent Ca(2+) sensitivity were similar in cav-1(+/+) and cav-1(-/-) cells. In summary, cav-1 ablation elevates Ca(2+) spark and transient K(Ca) current frequency, attenuates the coupling relationship between voltage-dependent Ca(2+) channels and RyR channels that generate Ca(2+) sparks, and elevates K(Ca) channel density but does not alter transient K(Ca) current activation by Ca(2+) sparks. These findings indicate that cav-1 is required for physiological Ca(2+) spark and transient K(Ca) current regulation in cerebral artery smooth muscle cells.
authors.affiliation: Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Cheng
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Jaggar
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D002104:Cadmium / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D051242:Caveolin 1 / Q000235:genetics* / Q000502:physiology*; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D007211:Indoles / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D009131:Muscle, Smooth, Vascular / Q000502:physiology* / Q000648:ultrastructure; D032389:Myocytes, Smooth Muscle / Q000502:physiology* / Q000648:ultrastructure; D019335:Nitroarginine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology
chemical_list: D051242:Caveolin 1; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007211:Indoles; D019837:Ryanodine Receptor Calcium Release Channel; D002104:Cadmium; D019335:Nitroarginine; D001464:Barium; C048220:paxilline; D016257:Fura-2