Luo Xiaobin, Lin Huixian, Pan Zhengwei, Xiao Jiening, Zhang Yong, Lu Yanjie, Yang Baofeng, Wang Zhiguo
Research Center, Montreal Heart Institute, Montreal, PQ, Canada.
J Biol Chem. 2008 Jul 18;283(29):20045-52. doi: 10.1074/jbc.M801035200. Epub 2008 May 5.
Cardiac hypertrophy is characterized by electrical remolding with increased risk of arrhythmogenesis. Enhanced abnormal automaticity of ventricular cells contributes critically to hypertrophic arrhythmias. The pacemaker current I(f), carried by the hyperpolarization-activated channels encoded mainly by the HCN2 and HCN4 genes in the heart, plays an important role in determining cardiac automaticity. Their expressions reportedly increase in hypertrophic and failing hearts, contributing to arrhythmogenesis under these conditions. We performed a study on post-transcriptional regulation of expression of HCN2 and HCN4 genes by microRNAs. We experimentally established HCN2 as a target for repression by the muscle-specific microRNAs miR-1 and miR-133 and established HCN4 as a target for miR-1 only. We unraveled robust increases in HCN2 and HCN4 protein levels in a rat model of left ventricular hypertrophy and in angiotensin II-induced neonatal ventricular hypertrophy. The up-regulation of HCN2/HCN4 was accompanied by pronounced reduction of miR-1/miR-133 levels. Forced expression of miR-1/miR-133 by transfection prevented overexpression of HCN2/HCN4 in hypertrophic cardiomyocytes. The serum-responsive factor protein level was found significantly decreased in hypertrophic hearts, and silencing of this protein by RNA interference resulted in increased levels of miR-1/miR-133 and concomitant increases in HCN2 and HCN4 protein levels. We conclude that down-regulation of miR-1 and miR-133 expression contributes to re-expression of HCN2/HCN4 and thereby the electrical remodeling process in hypertrophic hearts. Our study also sheds new light on the cellular function and pathological role of miR-1/miR-133 in the heart.
心肌肥厚的特征是电重构，心律失常发生风险增加。心室细胞异常自律性增强是肥厚性心律失常的关键因素。心脏中主要由HCN2和HCN4基因编码的超极化激活通道所携带的起搏电流I(f)，在决定心脏自律性方面起重要作用。据报道，它们在肥厚和衰竭心脏中的表达增加，在这些情况下促成心律失常的发生。我们进行了一项关于微小RNA对HCN2和HCN4基因表达的转录后调控的研究。我们通过实验确定HCN2是肌肉特异性微小RNA miR-1和miR-133的抑制靶点，并且确定HCN4仅是miR-1的靶点。我们发现在左心室肥厚大鼠模型和血管紧张素II诱导的新生大鼠心室肥厚中，HCN2和HCN4蛋白水平显著升高。HCN2/HCN4的上调伴随着miR-1/miR-133水平的明显降低。通过转染强制表达miR-1/miR-133可防止肥厚性心肌细胞中HCN2/HCN4的过表达。在肥厚心脏中发现血清反应因子蛋白水平显著降低，通过RNA干扰使该蛋白沉默导致miR-1/miR-133水平升高以及HCN2和HCN4蛋白水平随之升高。我们得出结论，miR-1和miR-133表达下调促成HCN2/HCN4的重新表达，从而导致肥厚心脏中的电重构过程。我们的研究还为miR-1/miR-133在心脏中的细胞功能和病理作用提供了新的线索。
