Ryanodine Receptor Channels in Heart Failure

描述（由申请方提供）：细胞内Ca的异常处理已被确定为心力衰竭（HF）的主要原因，心力衰竭是美国的主要死亡原因。尽管付出了巨大的努力，HF相关的Ca信号改变的确切机制仍然知之甚少。该建议的总体目标是确定肌浆网（SR）钙释放通道/ryanodine受体（RyR）在HF中的作用。在心肌中，RyR通过Ca诱导的Ca释放（CICR）机制被胞质Ca激活。最近在我们的实验室获得的数据表明，除了胞质Ca，RyR也控制的SR内的Ca在管腔网站。腔钙传感器调节SR钙释放的存在对我们理解正常和病变心肌细胞内钙信号具有深远的意义。例如，通过将RyR通道的功能活性与SR的负载状态联系起来，管腔Ca传感器在RyR改变的情况下稳定Ca释放。因此，任何影响RyR特性的因素都可以通过SR Ca负荷的变化和伴随的RyR通道活性的管腔Ca依赖性变化来补偿。我们的初步数据表明，这种反馈机制可能在HF中受到损害，可能导致SR Ca释放功能的慢性抑制。在本提案中，我们将解决以下问题：1）在HF中，RyR的内在门控特性（即细胞溶质和管腔Ca的调节）是否改变？2)这些改变的确切分子机制是什么？以及3）所提出的RyR的变化如何促成HF中的异常Ca循环？为此，将利用重建系统中的单通道方法和分离的心室肌细胞和整个跳动心脏中的荧光钙成像技术，使用几种成熟的HF动物模型，在多个水平上确定RyR特性与HF之间的关系。这项研究的结果将提高我们对HF中钙处理改变的机制和作用的理解。

DESCRIPTION (provided by applicant): Abnormal handling of intracellular Ca has been identified as a major cause of heart failure (HF), a leading cause of death in the US. Despite intense effort, the precise mechanisms underlying the HF-related alterations of Ca signaling remain poorly understood. The overall goal of this proposal is to define the role of alterations of the sarcoplasmic reticulum (SR) Ca release channel/ryanodine receptor (RyR) in HF. In cardiac muscle, RyRs are activated by cytosolic Ca via the mechanism of Ca-induced Ca release (CICR). Data obtained recently in our laboratory shows that in addition to cytosolic Ca, RyRs are also controlled by Ca inside the SR at luminal sites. The presence of a luminal Ca sensor regulating release of SR Ca has profound implications for our understanding of intracellular Ca signaling in normal and diseased myocardium. For example, by linking the functional activity of RyR channels to the loading state of SR, the luminal Ca sensor stabilizes Ca release in the face of alterations of RyRs. Consequently, any factors affecting the properties of RyRs are compensated by changes in SR Ca load and concomitant luminal Ca-dependent changes in RyR channel activity. Our preliminary data suggest that this feedback mechanism might be compromised in HF, potentially leading to chronic depression of SR Ca release function. In the present proposal we will address the following questions: 1) Are the intrinsic gating properties of RyRs (i.e. regulation by cytosolic and luminal Ca) altered in HF? 2) What are the precise molecular mechanisms of these alterations? And 3) How do the proposed changes in RyRs contribute to abnormal Ca cycling in HF? To this end, single channel approaches in a reconstitution system and fluorescent calcium imaging techniques in isolated ventricular myocytes and whole beating hearts will be utilized to determine relationships between RyR properties and HF at multiple levels, using several well-established animal models of HF. The results of this study will improve our understanding of the mechanisms and role of altered Ca handling in HF.