Regulation of calcium sparks and spontaneous transient outward currents by RyR3 in arterial vascular smooth muscle cells.
Intracellular Ca(2+) levels control both contraction and relaxation in vascular smooth muscle cells (VSMCs). Ca(2+)-dependent relaxation is mediated by discretely localized Ca(2+) release events through ryanodine receptor (RyR) channels in the sarcoplasmic reticulum (SR). These local increases in Ca(2+) concentration, termed sparks, stimulate nearby Ca(2+)-activated K(+) (BK) channels causing BK currents (spontaneous transient outward currents or STOCs). STOCs are hyperpolarizing currents that oppose vasoconstriction. Several RyR isoforms are coexpressed in VSMCs; however, their role in Ca(2+) spark generation is unknown. To provide molecular information on RyR cluster function and assembly, we examined Ca(2+) sparks and STOCs in RyR3-deficient freshly isolated myocytes of resistance-sized cerebral arteries from knockout mice and compared them to Ca(2+) sparks in cells from wild-type mice. We used RT-PCR to identify RyR1, RyR2, and RyR3 mRNA in cerebral arteries. Ca(2+) sparks in RyR3-deficient cells were similar in peak amplitude (measured as F/F(0)), width at half-maximal amplitude, and duration compared with wild-type cell Ca(2+) sparks. However, the frequency of STOCs (between -60 mV and -20 mV) was significantly higher in RyR3-deficient cells than in wild-type cells. Ca(2+) sparks and STOCs in both RyR3-deficient and wild-type cells were inhibited by ryanodine (10 micromol/L), external Ca(2+) removal, and depletion of SR Ca(2+) stores by caffeine (1 mmol/L). Isolated, pressurized cerebral arteries of RyR3-deficient mice developed reduced myogenic tone. Our results suggest that RyR3 is part of the SR Ca(2+) spark release unit and plays a specific molecular role in the regulation of STOCs frequency in mouse cerebral artery VSMCs after decreased arterial tone.
Löhn
M
M
HELIOS Klinikum-Berlin, Franz Volhard Clinic and Max Delbrück Center for Molecular Medicine, Medical Faculty of the Charité, Humboldt University Berlin, Germany.
Jessner
W
W
Fürstenau
M
M
Wellner
M
M
Sorrentino
V
V
Haller
H
H
Luft
F C
FC
Gollasch
M
M
D000818:Animals; D001158:Arteries / Q000166:cytology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D002536:Cerebral Arteries / Q000166:cytology / Q000502:physiology; D004553:Electric Conductivity; D017136:Ion Transport; D051379:Mice; D018345:Mice, Knockout; D008955:Models, Cardiovascular; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000502:physiology*; D014661:Vasoconstriction
D024681:Potassium Channels, Calcium-Activated; D020033:Protein Isoforms; D012333:RNA, Messenger; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium