Child & Family Research Institute, Department of Anaesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada.
PLoS One. 2013;8(2):e55333. doi: 10.1371/journal.pone.0055333. Epub 2013 Feb 7.
Agonist-stimulated smooth muscle Ca2+ waves regulate blood vessel tone and vasomotion. Previous studies employing cytoplasmic Ca2+ indicators revealed that these Ca2+ waves were stimulated by a combination of inositol 1,4,5-trisphosphate- and Ca2+ -induced Ca2+ release from the endo/sarcoplasmic reticulum. Herein, we present the first report of endothelin-1 stimulated waves of Ca2+ depletion from the sarcoplasmic reticulum of vascular smooth muscle cells using a calsequestrin-targeted Ca2+ indicator. Our findings confirm that these waves are due to regenerative Ca2+ -induced Ca2+ release by the receptors for inositol 1,4,5-trisphosphate. Our main new finding is a transient elevation in SR luminal Ca2+ concentration (Ca2+) both at the site of wave initiation, just before regenerative Ca2+ release commences, and at the advancing wave front, during propagation. This strongly suggests a role for Ca2+ in the activation of inositol 1,4,5-trisphosphate receptors during agonist-induced calcium waves. In addition, quantitative analysis of the gradual decrease in the velocity of the depletion wave, observed in the absence of external Ca2+, indicates continuity of the lumen of the sarcoplasmic reticulum network. Finally, our observation that the depletion wave was arrested by the nuclear envelope may have implications for selective Ca2+ signalling.
激动剂刺激的平滑肌 Ca2+波调节血管张力和血管运动。以前使用细胞质 Ca2+指示剂的研究表明，这些 Ca2+波是由肌浆网内/内质网中肌醇 1,4,5-三磷酸和 Ca2+诱导的 Ca2+释放的组合刺激的。在此，我们使用 calsequestrin 靶向 Ca2+指示剂报告了内皮素-1 刺激的血管平滑肌细胞肌浆网 Ca2+耗竭波的第一个报告。我们的研究结果证实，这些波是由于肌醇 1,4,5-三磷酸的受体引起的再生 Ca2+诱导的 Ca2+释放。我们的主要新发现是在波起始部位，即在开始再生 Ca2+释放之前，以及在波前传播期间，SR 腔 Ca2+浓度 (Ca2+)短暂升高。这强烈表明在激动剂诱导的钙波中，Ca2+在肌醇 1,4,5-三磷酸受体的激活中起作用。此外，在不存在外 Ca2+的情况下，对耗竭波速度逐渐降低的定量分析表明，肌浆网网络的腔是连续的。最后，我们观察到耗竭波被核膜阻止，这可能对选择性 Ca2+信号具有重要意义。
