Regulation of Calcium Homeostasis by MyomiRs in Heart Failure

描述（由申请人提供）：尽管对潜在机制的理解有所进展，但心力衰竭（HF）仍然是导致死亡的主要原因，这表明迫切需要开发新的非常规治疗策略。异常细胞内钙（Ca2+）处理已涉及的恶性心律失常的发病机制特征的心力衰竭（HF）。心脏兴奋-收缩（EC）偶联是通过Ca2+诱导的Ca2+释放（CICR）介导的，这是由肌浆网（SR） Ca2+敏感Ca2+通道控制的，也称为心脏ryanodine受体（RyR2）。MicroRNAs （miRs）是约22个核苷酸长的非蛋白编码rna，通过碱基配对相互作用识别其靶mrna，随后通过靶向这些mrna进行翻译抑制或降解来抑制基因表达。快速积累的证据表明，失调的miRs在心律失常和心衰等心脏发病机制中发挥着重要作用，这使它们成为新的有吸引力的治疗靶点。但是，为了更好地理解miR的功能，还需要做很多工作。我们的初步结果暗示了肌组织特异性的miRs家族，称为myomir，在心肌细胞中调节Ca2+处理。该提案的中心假设是，包括miR-208a， miR-208b和miR-499在内的肌密子通过调节参与Ca2+处理的大分子复合物的结构和功能，在调节Ca2+稳态中发挥关键作用。为了验证这一假设，我们开发了在体外和体内完整心脏中修改mirna表达的技术，以便使用电生理学和单光子激光扫描共聚焦显微镜检查它们对单心室肌细胞Ca2+循环的影响。具体来说，我们的目的是研究myomir通过RyR2s在心室肌细胞中介导的SR Ca2+释放调节的分子决定因素，并通过心力衰竭大鼠模型测试这些miRs的异常表达模式是否有助于心脏病特征的Ca2+依赖性心律失常。

DESCRIPTION (provided by applicant): Despite advances in the understanding of underlying mechanisms, heart failure (HF) remains the major cause of mortality, indicating the urgent need in the development of novel unconventional therapeutic strategies. Abnormal intracellular calcium (Ca2+) handling has been implicated in the pathogenesis of malignant arrhythmias characteristic of Heart Failure (HF). Cardiac excitation-contraction (EC) coupling is mediated through Ca2+-induced Ca2+ release (CICR), which is controlled by sarcoplasmic reticulum (SR) Ca2+-sensitive Ca2+ channels, also known as cardiac ryanodine receptors (RyR2). MicroRNAs (miRs) are ~22-nucleotide-long nonprotein-coding RNAs that recognize their target mRNAs by base pairing interactions and subsequently inhibit gene expression by targeting these mRNAs for translational repression or degradation. Rapidly accumulating evidence implicates dysregulated miRs in cardiac pathogenesis including arrhythmias and HF rendering them new attractive targets for therapy. However, much work must be done for better understanding of miR functions. Our preliminary results implicate a family of miRs specific to muscle tissue called myomiRs in regulation of Ca2+ handling in cardiomyocytes. The central hypothesis of this proposal is that myomiRs which include miR-208a, miR-208b and miR-499 play a critical role in regulating Ca2+ homeostasis by modulating the structure and function of macromolecular complexes involved in Ca2+ handling. In order to test this hypothesis we have developed techniques to modify the expression of miRNAs in vitro and in intact hearts in vivo in order to examine their effects on Ca2+ cycling in single ventricular myocytes using electrophysiology and single photon laser scanning confocal microscopy. Specifically we aim to investigate the molecular determinants of myomiR-mediated regulation of SR Ca2+ release through RyR2s in ventricular myocytes, and test whether aberrant expression patterns of these miRs contribute to Ca2+-dependent arrhythmias characteristic of cardiac disease using rat model of heart failure.