Journal
CIRCULATION RESEARCH
Volume 111, Issue 9, Pages 1137-1146Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/CIRCRESAHA.112.273755
Keywords
angiotensin II; TRPM7; phenotypic modulation; smooth muscle; calcium signaling; hyperplasia; ion channels; vascular smooth muscle
Funding
- National Natural Science Foundation of China [30900530]
- Science and Technology Planning Project of Guangdong Province China [2011B080701012]
- Doctoral Fund of Ministry of Education of China [20090171120055]
- Fundamental Research Funds for the Central Universities in China [11ykpy02]
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Rationale: 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. Objective: The present study was designed to explore whether the Ca2+-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. Methods and Results: 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 Mg2+-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 Ca2+-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. Conclusions: 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 Ca2+-influx-mediated activation of Pyk2-ERK1/2-Elk-1 pathway. (Circ Res. 2012;111:1137-1146.)
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