Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
J Biol Chem. 2012 Jun 1;287(23):19199-206. doi: 10.1074/jbc.M112.341073. Epub 2012 Apr 2.
Stretch of the vascular wall is an important stimulus to maintain smooth muscle contractile differentiation that is known to depend on L-type calcium influx, Rho-activation, and actin polymerization. The role of microRNAs in this response was investigated using tamoxifen-inducible and smooth muscle-specific Dicer KO mice. In the absence of Dicer, which is required for microRNA maturation, smooth muscle microRNAs were completely ablated. Stretch-induced contractile differentiation and Rho-dependent cofilin-2 phosphorylation were dramatically reduced in Dicer KO vessels. On the other hand, acute stretch-sensitive growth signaling, which is independent of influx through L-type calcium channels, was not affected by Dicer KO. Contractile differentiation induced by the actin polymerizing agent jasplakinolide was not altered by deletion of Dicer, suggesting an effect upstream of actin polymerization. Basal and stretch-induced L-type calcium channel expressions were both decreased in Dicer KO portal veins, and inhibition of L-type channels in control vessels mimicked the effects of Dicer deletion. Furthermore, inhibition of miR-145, a highly expressed microRNA in smooth muscle, resulted in a similar reduction of L-type calcium channel expression. This was abolished by the Ca(2+)/calmodulin-dependent protein kinase II inhibitor KN93, suggesting that Ca(2+)/calmodulin-dependent protein kinase IIδ, a target of miR-145 and up-regulated in Dicer KO, plays a role in the regulation of L-type channel expression. These results show that microRNAs play a crucial role in stretch-induced contractile differentiation in the vascular wall in part via miR-145-dependent regulation of L-type calcium channels.
血管壁的伸展是维持平滑肌收缩分化的重要刺激因素，已知这种分化依赖于 L 型钙内流、Rho 激活和肌动蛋白聚合。本研究使用他莫昔芬诱导型和血管平滑肌特异性 Dicer KO 小鼠，探讨了 microRNAs 在这一反应中的作用。在缺乏 microRNA 成熟所必需的 Dicer 的情况下，平滑肌 microRNAs 完全被消除。在 Dicer KO 血管中，伸展诱导的收缩分化和 Rho 依赖性肌动蛋白结合蛋白 2 磷酸化明显减少。另一方面，急性伸展敏感的生长信号，独立于通过 L 型钙通道的内流，不受 Dicer KO 的影响。肌动蛋白聚合剂 jasplakinolide 诱导的收缩分化不受 Dicer 缺失的影响，表明其作用发生在肌动蛋白聚合的上游。基础状态和伸展诱导的 L 型钙通道表达在 Dicer KO 门静脉中均降低，而在对照血管中抑制 L 型通道模拟了 Dicer 缺失的作用。此外，高度表达于平滑肌的 microRNA-145 的抑制导致 L 型钙通道表达的类似减少，这一减少被 Ca(2+)/钙调蛋白依赖性蛋白激酶 II 抑制剂 KN93 所消除，表明 Ca(2+)/钙调蛋白依赖性蛋白激酶 IIδ是 miR-145 的靶标，在 Dicer KO 中上调，在 L 型通道表达的调节中起作用。这些结果表明，microRNAs 通过 miR-145 依赖性调节 L 型钙通道，在血管壁伸展诱导的收缩分化中发挥关键作用。
