Department of Clinical Laboratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086, China.
Biochem Biophys Res Commun. 2010 Apr 16;394(4):955-61. doi: 10.1016/j.bbrc.2010.03.096. Epub 2010 Mar 20.
Capacitative calcium entry (CCE) refers to the influx of calcium through plasma membrane channels activated on depletion of endoplasmic sarcoplasmic/reticulum (ER/SR) Ca(2+) stores, which is performed mainly by the transient receptor potential (TRP) channels. TRP channels are expressed in cardiomyocytes. Calcium-sensing receptor (CaR) is also expressed in rat cardiac tissue and plays an important role in mediating cardiomyocyte apoptosis. However, there are no data regarding the link between CaR and TRP channels in rat heart. In this study, in rat neonatal myocytes, by Ca(2+) imaging, we found that the depletion of ER/SR Ca(2+) stores by thapsigargin (TG) elicited a transient rise in cytoplasmic Ca(2+) (Ca(2+)), followed by sustained increase depending on extracellular Ca(2+). But, TRP channels inhibitor (SKF96365), not L-type channels or the Na(+)/Ca(2+) exchanger inhibitors, inhibited Ca(2+) relatively high. Then, we found that the stimulation of CaR with its activator gadolinium chloride (GdCl(3)) or by an increased extracellular Ca(2+)(Ca(2+)) increased the concentration of intracelluar Ca(2+), whereas, the sustained elevation of Ca(2+) was reduced in the presence of SKF96365. Similarly, the duration of Ca(2+) increase was also shortened in the absence of extracellular Ca(2+). Western blot analysis showed that GdCl(3) increased the expression of TRPC6, which was reversed by SKF96365. Additionally, SKF96365 reduced cardiomyocyte apoptosis induced by GdCl(3). Our results suggested that CCE exhibited in rat neonatal myocytes and CaR activation induced Ca(2+)-permeable cationic channels TRPCs to gate the CCE, for which TRPC6 was one of the most likely candidates. TRPC6 channel was functionally coupled with CaR to enhance the cardiomyocyte apoptosis.
电容钙内流 (CCE) 是指内质网/肌浆网 (ER/SR) 钙库耗竭时通过质膜通道流入的钙，主要由瞬时受体电位 (TRP) 通道完成。TRP 通道在心肌细胞中表达。钙敏感受体 (CaR) 也在大鼠心脏组织中表达，并在介导心肌细胞凋亡中发挥重要作用。然而，关于大鼠心脏中 CaR 和 TRP 通道之间的联系尚无数据。在这项研究中，在大鼠新生心肌细胞中，通过钙成像，我们发现毒胡萝卜素 (TG) 耗尽 ER/SR 钙库会引起细胞质钙 (Ca(2+)) 的短暂上升，随后依赖于细胞外钙持续增加。但是，TRP 通道抑制剂 (SKF96365)，而不是 L 型通道或 Na(+)/Ca(2+) 交换抑制剂，相对抑制 Ca(2+) 较高。然后，我们发现用其激动剂钆氯化物 (GdCl(3)) 刺激 CaR 或增加细胞外 Ca(2+)(Ca(2+)) 增加细胞内 Ca(2+) 浓度，而在 SKF96365 存在下，持续升高的 Ca(2+) 减少。同样，在不存在细胞外 Ca(2+) 的情况下，Ca(2+) 增加的持续时间也缩短。Western blot 分析显示，GdCl(3) 增加了 TRPC6 的表达，而 SKF96365 则逆转了这一作用。此外，SKF96365 减少了 GdCl(3) 诱导的心肌细胞凋亡。我们的结果表明，在大鼠新生心肌细胞中存在 CCE，CaR 激活诱导 Ca(2+) 通透性阳离子通道 TRPC 门控 CCE，其中 TRPC6 是最有可能的候选者之一。TRPC6 通道与 CaR 功能偶联，增强心肌细胞凋亡。
