Na+ Channel mRNA Regulation in Heart Failure

项目摘要 人类心力衰竭(HF)与心脏钠通道电流减少有关。最近，我们 研究表明，心脏Na+通道(SCN5A)的下调可能导致心律失常的风险，而且 上调利率可以降低这种风险。此外，我们还发现，心脏SCN5A mRNA的减少 丰度反映在循环中的白细胞(WBC)中，它也表达SCN5A，并且a SCN5A的降低对合适的植入式心脏除颤器(ICD)治疗具有很高的预测性。这些数据 提示SCN5A调节对心力衰竭的心律失常风险具有重要意义。 在一定程度上，SCN5A的减少是由异常的mRNA剪接介导的。在本应用程序中，我们打算 探索心力衰竭时SCN5A基因丰度降低的全新机制。在初步数据中， 我们发现，Hur是一类与富含AU的元素结合的RNA稳定蛋白的成员，它被表达出来 并通过与SCN5A转录本结合来促进Na+通道mRNA的稳定。此外，HUR 在人类心力衰竭中似乎下调，可能是导致Na+通道和 心力衰竭患者发生心律失常的风险增加。 假设：我们认为HUR在HF中下调，这种下调有助于减少 Na+电流和心律失常风险增加，而Hur上调将减少Na+通道 心衰患者的下调调节和心律失常风险。 目的1：确定Hur对心肌细胞Na+电流的调节作用。 目的2：确定HUR活性下调的机制和程度 非缺血性心肌病及其与Na+通道基因、蛋白和电流的相关性。 目的3：确定HUR过表达在多大程度上能上调Na+通道mRNA，升高Na+ 通道电流，并降低缺血性和非缺血性心肌病的心律失常风险。

Project Summary Human heart failure (HF) has been associated with reduced cardiac sodium channel current. Recently, we have shown that downregulation of cardiac Na+ channels (SCN5A) can contribute to arrhythmic risk and that upregulation can mitigate that risk. Furthermore, we have shown that the reduction in cardiac SCN5A mRNA abundance is reflected in circulating white blood cells (WBCs), which also express SCN5A, and that a reduction in SCN5A is highly predictive of appropriate implanted cardiac defibrillator (ICD) therapy. These data suggest that SCN5A regulation is critical to arrhythmic risk in HF. In part, the reduction in SCN5A is mediated by abnormal mRNA splicing. In this application, we intend to explore an entirely novel mechanism by which SCN5A mRNA abundance is reduced in HF. In preliminary data, we show that HuR, a member of a class of RNA stabilizing proteins that bind to AU-rich elements, is expressed in the heart and contributes to Na+ channel mRNA stability by binding to SCN5A transcript. Furthermore, HuR appears to be downregulated in human HF, perhaps contributing to the downregulation of Na+ channel and increased arrhythmic risk seen in HF. Hypothesis: We propose that HuR is downregulated in HF, that this downregulation contributes to reduced Na+ current and increased arrhythmic risk, and that upregulation of HuR will reduce Na+ channel downregulation and arrhythmic risk in HF. Aim 1: Determine the extent to which HuR can regulate Na+ currents in cardiomyocytes. Aim 2: Determine the mechanism and extent to which HuR activity is downregulated in ischemic and nonischemic cardiomyopathy and the correlation with Na+ channel mRNA, protein, and current. Aim 3: Determine the extent to which overexpression of HuR can raise Na+ channel mRNA, raise Na+ channel current, and reduce arrhythmic risk in ischemic and nonischemic cardiomyopathy.