CaMKII Regulation of Cardiac Ryanodine Receptors in Atrial Fibrillation

描述(申请人提供)：心脏兰尼定受体(RyR2)在心脏兴奋-收缩偶联过程中发挥核心作用。RyR2调控的变化 在各种心血管疾病中都很明显。RyR2的磷酸化状态在房颤(房颤)患者中的变化已被描述，但其潜在的异常机制仍不清楚。大量证据表明，RyR2通道由一个大分子复合体组成，其调节亚基包括蛋白激酶和磷酸酶。在人类心房组织和心肌细胞中的研究以及在敲入小鼠模型中的实验表明，RyR2磷酸化增加易导致心房异位和房颤的进展。我们的初步数据表明，RyR2结合蛋白磷酸酶(PPS)的变化可能是房颤患者RyR2磷酸化升高的基础，尽管目前对此知之甚少。该项目的长期目标是确定PPS调节正常心脏和房颤患者/小鼠RyR2活性的细胞/分子机制。目前的建议将检验与RyR2相关的PP调节亚基水平的变化导致肌浆网(SR)钙泄漏增加和房颤易感性的普遍假设。特殊目的(1)将使用生化和遗传学方法来剖析PPS在调节RyR2磷酸化中的作用。特殊目的(2)将利用遗传小鼠模型研究RyR2的PP调节对心房细胞SR钙处理的影响。特异性靶点(3)将确定RyR2的PP调节在心房颤动中的作用 在小鼠模型中进行活体实验。意义：RyR2介导的SR钙泄漏异常与房颤的增加有关，房颤是最常见的心律失常类型。将使用重组蛋白、遗传小鼠模型和人类心房活检在分子、细胞和体内水平上研究这种机制。预计这些多学科研究将为房颤患者RyR2钙释放通道失调的分子机制提供基础和新的见解。这些见解可能会指导未来抗心律失常药物治疗房颤的发展。

DESCRIPTION (provided by applicant): Cardiac ryanodine receptors (RyR2) play a central role in the process of excitation-contraction coupling in the heart. Alterations in RyR2 regulation are evident in a variety of cardiovascular diseases. Changes in the phosphorylation status of RyR2 have been described in patients with atrial fibrillation (AF), but the underlying abnormal mechanisms remain poorly understood. Considerable evidence suggests that RyR2 channels comprise a macromolecular complex with regulatory subunits including protein kinases and phosphatases. Studies in human atrial tissue and myocytes as well as experiments in knock-in mouse models have revealed that increased RyR2 phosphorylation predisposes to atrial ectopy and progression of AF. Our preliminary data suggest that alterations in the RyR2-bound protein phosphatases (PPs) might underlie elevated RyR2 phosphorylation in AF, although very little is currently known about this. The long-term goal of this project is to define the cellular/molecular mechanisms by which PPs regulate RyR2 activity in both normal hearts and in humans/mice with AF. The present proposal will test the general hypothesis that variation in levels of PP regulatory subunits associated with RyR2 contributes to enhanced sarcoplasmic reticulum (SR) Ca leak and vulnerability to AF. Specific aim (1) will use biochemical and genetic approaches to dissect the role of PPs in the regulation of RyR2 phosphorylation. Specific aim (2) will examine the effects of PP regulation of RyR2 on SR Ca handling in atrial cells using genetic mouse models. Specific aim (3) will determine the role of PP regulation of RyR2 in atrial fibrillation in vivo in mouse models. Significance: Abnormal RyR2-mediated SR Ca leak has been associated with increased propensity to AF, the most prevalent type of cardiac arrhythmia. The mechanisms will be studied at the molecular, cellular and in vivo level, using recombinant proteins, genetic mouse models and human atrial biopsies. It is anticipated that these multidisciplinary studies will provide fundamental and new insights into the molecular mechanisms by which the RyR2 calcium release channel becomes dysregulated in AF. These insights may guide future developments of anti-arrhythmic drugs for the treatment of AF.