TMEM16A and Myocardin Form a Positive Feedback Loop That Is Disrupted by KLF5 During Ang II–Induced Vascular Remodeling
TMEM16A and Myocardin Form a Positive Feedback Loop That Is Disrupted by KLF5 During Ang II–Induced Vascular Remodeling
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DOI：
10.1161/hypertensionaha.115.05280
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发表时间：
2015-08
期刊：
影响因子：
8.3
通讯作者：
Xinhua Zhang;Bin Zheng;Zhan Yang;M. He;L. Yue;Ruonan Zhang;Ming Zhang;Wei Zhang;Xuan Zhang-Xuan-Zh
中科院分区：
文献类型：
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作者：
Xinhua Zhang;Bin Zheng;Zhan Yang;M. He;L. Yue;Ruonan Zhang;Ming Zhang;Wei Zhang;Xuan Zhang-Xuan-Zh
TMEM16A蛋白是血管平滑肌细胞钙依赖的氯离子通道(CaCCs)的重要组成部分。最近的一项研究表明，TMEM16A抑制血管紧张素II诱导的大鼠基底动脉平滑肌细胞的增殖。然而，TMEM16A是否以及如何参与了以血管平滑肌细胞增殖为特征的血管重塑，目前仍不清楚。在这项研究中，进行了荧光素酶报告、Western blotting和qRT-PCR检测。结果提示，Myocardin通过与血清反应因子(SRF)在人主动脉平滑肌细胞(HASMCs)TMEM16A启动子上形成复合体来促进TMEM16A的表达。反过来，上调的TMEM16A促进肌钙蛋白和血管平滑肌细胞标志基因的表达，从而形成一个正反馈环，诱导细胞分化，抑制细胞增殖。血管紧张素II通过Krüppel样因子5(KLF5)抑制培养的HASMCs中TMEM16A的表达。此外，体内实验表明，血管紧张素II注入小鼠可显著减少TMEM16A的表达和血管重塑，而KLF5基因缺失(KLF5−/−)小鼠的血管紧张素II诱导的作用在很大程度上被逆转。KLF5与SRF竞争与Myocardin相互作用，从而限制Myocardin与SRF的结合以及Myocardin和SRF对TMEM16A启动子的协同激活。我们的研究表明，血管紧张素II诱导KLF5的表达，促进KLF5与肌钙蛋白的结合，破坏肌钙蛋白-SRF复合体，从而抑制TMEM16A的转录。阻断Myocardin和TMEM16A之间的正反馈环可能是治疗血管重塑的一种新方法。
The TMEM16A protein is an important component of Ca2+-dependent Cl− channels (CaCCs) in vascular smooth muscle cells. A recent study showed that TMEM16A inhibits angiotensin II–induced proliferation in rat basilar smooth muscle cells. However, whether and how TMEM16A is involved in vascular remodeling characterized by vascular smooth muscle cell proliferation remains largely unclear. In this study, luciferase reporter, Western blotting, and qRT-PCR assays were performed. The results suggested that myocardin promotes TMEM16A expression by forming a complex with serum response factor (SRF) on the TMEM16A promoter in human aortic smooth muscle cells (HASMCs). In turn, upregulated TMEM16A promotes expression of myocardin and vascular smooth muscle cell marker genes, thus forming a positive feedback loop that induces cell differentiation and inhibits cell proliferation. Angiotensin II inhibits TMEM16A expression via Krüppel-like factor 5 (KLF5) in cultured HASMCs. Moreover, in vivo experiments show that infusion of angiotensin II into mice causes a marked reduction in TMEM16A expression and vascular remodeling, and angiotensin II–induced effects are largely reversed in KLF5 null (KLF5−/−) mice. KLF5 competes with SRF to interact with myocardin, thereby limiting myocardin binding to SRF and the synergistic activation of the TMEM16A promoter by myocardin and SRF. Our studies demonstrated that angiotensin II induces KLF5 expression and facilitates KLF5 association with myocardin to disrupt the myocardin–SRF complex, subsequently leading to inhibition of TMEM16A transcription. Blocking the positive feedback loop between myocardin and TMEM16A may be a novel therapeutic approach for vascular remodeling.