Department of Pharmacology, Zhongshan School of Medicine, Sun Yat-Sen University, 74 Zhongshan 2nd Rd, Guangzhou, China 510080.
Circ Res. 2012 Oct 12;111(9):1137-46. doi: 10.1161/CIRCRESAHA.112.273755. Epub 2012 Aug 14.
Angiotensin II (Ang II) has pleiotropic effects on vascular smooth muscle cells (VSMCs). It has been demonstrated to promote the proliferative phenotype of VSMCs in mouse ascending aorta, but the underlying mechanisms remain incompletely understood.
The present study was designed to explore whether the Ca(2+)-permeable transient receptor potential melastatin 7 (TRPM7) channel is involved in Ang II-induced phenotype switching of ascending aortic VSMCs and to dissect the molecular mechanisms by which TRPM7 modulates VSMC phenotype.
As revealed by current recording, Ang II infusion increased TRPM7 whole-cell currents in ascending aortic VSMCs. The increase in TRPM7 currents was found to result from enhanced expression of TRPM7 protein rather than elevated single-channel activity (open probability and slope conductance) and/or reduced Mg(2+)-mediated channel block. Mechanistically, Ang II elevated TRPM7 expression via Ang II type 1 receptor-mediated ERK1/2 signaling. As indicated by the expression levels of VSMC differentiation marker genes, phenotypic switching of ascending aorta occurred during Ang II infusion. Meanwhile, ERK1/2-Elk-1 signaling pathway known to suppress VSMC differentiation was activated in Ang II-infused ascending aorta. Knockdown of TRPM7 with small interfering RNA established a causative role of TRPM7 in Ang II-induced phenotypic change and promotion of cell proliferation. Moreover, TRPM7 was shown to be required for Pyk2-ERK1/2-Elk-1 pathway activation by Ang II, which potentiated TRPM7 channel function and thus activated the Ca(2+)-sensitive kinase Pyk2. Finally, TRPM7 knockdown attenuated Ang II-induced displacement of myocardin from SM22 promoter, but the effects could be reversed by expression of constitutively active c-Src.
Our data establish that upregulation of TRPM7 channels by Ang II contributes to the development of the proliferative phenotype of ascending aortic VSMCs, and TRPM7 channel suppresses VSMC gene expression via Ca(2+) influx-mediated activation of Pyk2-ERK1/2-Elk-1 pathway.
血管紧张素 II（Ang II）对血管平滑肌细胞（VSMCs）具有多种作用。已证实它可促进小鼠升主动脉 VSMCs 的增殖表型，但潜在机制尚不完全清楚。
本研究旨在探讨钙通透性瞬时受体电位 melastatin 7（TRPM7）通道是否参与 Ang II 诱导的升主动脉 VSMCs 表型转换，并剖析 TRPM7 调节 VSMC 表型的分子机制。
通过电流记录发现，Ang II 输注增加了升主动脉 VSMCs 中的 TRPM7 全细胞电流。发现 TRPM7 电流的增加是由于 TRPM7 蛋白表达增强所致，而不是由于单个通道活性（开放概率和斜率电导）升高和/或 Mg2+ 介导的通道阻断减少所致。在机制上，Ang II 通过 Ang II 型 1 受体介导的 ERK1/2 信号转导来增加 TRPM7 的表达。如 Ang II 输注期间 VSMC 分化标记基因的表达水平所示，升主动脉发生表型转换。同时，已知抑制 VSMC 分化的 ERK1/2-Elk-1 信号通路在 Ang II 输注的升主动脉中被激活。用小干扰 RNA 敲低 TRPM7 建立了 TRPM7 在 Ang II 诱导的表型变化和促进细胞增殖中的因果作用。此外，TRPM7 被证明是 Ang II 激活 Pyk2-ERK1/2-Elk-1 通路所必需的，该通路增强了 TRPM7 通道的功能，从而激活了 Ca2+ 敏感激酶 Pyk2。最后，TRPM7 敲低减弱了 Ang II 诱导的肌球蛋白重链从 SM22 启动子的位移，但该作用可通过表达组成型激活的 c-Src 逆转。
我们的数据表明，Ang II 上调 TRPM7 通道有助于升主动脉 VSMCs 增殖表型的发展，并且 TRPM7 通道通过 Ca2+ 内流介导的 Pyk2-ERK1/2-Elk-1 通路的激活抑制 VSMC 基因表达。
