Lemos Virginia S, Poburko Damon, Liao Chiu-Hsiang, Cole William C, van Breemen Cornelis
Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada V6T 1Z1.
Biochem Biophys Res Commun. 2007 Jan 5;352(1):130-4. doi: 10.1016/j.bbrc.2006.10.160. Epub 2006 Nov 7.
Reversal of the Na+/Ca2+ -exchanger (NCX) has been shown to mediate Ca2+ influx during activation of G-protein linked receptors. Functional coupling between the reverse-mode NCX and the canonical transient receptor potential channels (TRPCs) has been proposed to mediate Ca2+ influx in HEK-293 cells overexpressing TRPC3. In this communication we present evidence for similar functional coupling of NCX to endogenously expressed TRPC6 in rat aorta smooth muscle cells. Selective inhibition of reverse-mode NCX with KB-R7943 and of non-selective cation-channels with SKF-96365 abolished Ca2+ influx in response to agonist stimulation (ATP). Expression of a dominant negative TRPC6 mutant also reduced the Ca2+ influx in proportion to its transfection efficiency. Calyculin A, which is known to disrupt the junctions of the plasma membrane and sarco/endoplasmic reticulum, increased global Na+ elevations and reduced stimulated Ca2+ influx. Together our data provide evidence that localized Na+ elevations are generated by TRPC6 and drive reversal of NCX to mediate Ca2+ influx.
钠钙交换体（NCX）的反向转运已被证明在G蛋白偶联受体激活过程中介导钙离子内流。有人提出反向模式的NCX与典型瞬时受体电位通道（TRPCs）之间的功能偶联可在过表达TRPC3的HEK-293细胞中介导钙离子内流。在本通讯中，我们提供了证据表明在大鼠主动脉平滑肌细胞中，NCX与内源性表达的TRPC6存在类似的功能偶联。用KB-R7943选择性抑制反向模式的NCX以及用SKF-96365抑制非选择性阳离子通道，可消除激动剂刺激（ATP）引起的钙离子内流。显性负性TRPC6突变体的表达也根据其转染效率成比例地降低了钙离子内流。已知可破坏质膜与肌浆网/内质网连接的Calyculin A增加了细胞内整体钠离子升高并减少了刺激引起的钙离子内流。我们的数据共同提供了证据，即TRPC6产生局部钠离子升高并驱动NCX的反向转运以介导钙离子内流。
