Stretch-Dependent Calcium Signaling in Heart

描述（由申请人提供）：PI已证明心脏中的Ca 2+火花在生理条件下发生在心脏舒张期和心脏收缩期。它们不仅是正常[Ca 2 +]i瞬变的基础，而且已被发现在介导细胞对应激和疾病的反应中至关重要，在从钙超载到肌营养不良症的心肌病的条件下促进收缩和运动功能障碍。最近，PI的工作表明，生理拉伸，如舒张期充盈过程中的肌细胞所经历的，显着改变了正常心室肌细胞中钙离子火花发生短暂。这种行为依赖于微管影响肌浆网（SR）的释放机制。尽管一年前的这一新发现很重要，但我们现在才开发出研究动态长度变化如何影响在不同条件下触发Ca 2+火花所需的其他工具。使用这些新的工具，我们观察到（在初步调查），拉伸依赖的变化，钙火花甚至比以前观察到的更大，似乎是由兰尼碱受体（RyR 2s）的敏感性的瞬时增加。额外的初步工作显示，令人惊讶的是，在来自对照小鼠的心脏细胞中，Ca 2+火花的这种瞬时增加是致炎性Ca 2+波以非常低的速率激活的基础，但在来自mdx小鼠（杜氏肌营养不良的鼠模型）的肌细胞中，PI和他的同事开发的工具将能够对心脏Ca 2+是如何影响心肌细胞的进行创新性的最先进的研究。通过生理拉伸来调节信号传导。拟议的工作旨在研究拉伸依赖的钙火花和钙波1。对照心室肌细胞; 2. RyR 2特性发生改变的心室肌细胞; 3.当微管被调制时，心室肌细胞; 4.来自肌营养不良蛋白缺失（mdx）小鼠的心室肌细胞。计划中的研究将首次揭示拉伸在心室肌细胞正常和病理性Ca 2+信号传导中的重要性。因此，这项工作不仅将提供关于正常细胞行为的基本新信息，而且还将提供关于肿瘤发生机制的基本新信息。此外，它将为各种心脏病（包括杜氏肌营养不良症）的新疗法奠定基础。 公共卫生相关性：心脏收缩和心律是由心脏细胞内的钙调节的。现在已知这种钙水平部分是由细胞长度的变化（这些变化也被称为“拉伸”）决定的，这是最近研究该提案的科学家发现的一个令人惊讶的结果。计划中的工作将检查细胞钙和功能的这种拉伸依赖性变化，并确定拉伸如何成为正常和缺陷心脏功能的基础。

DESCRIPTION (provided by applicant): Ca2+ sparks in heart have been shown by the PI to occur under physiological conditions during diastole and systole. They not only underlie the normal [Ca2+]i transient but have been found to be critically important in mediating the cellular response to stress and disease, contributing to contractile and arrhythmic dysfunction in conditions ranging from calcium overload to the cardiomyopathy of muscular dystrophy. Recently, work by the PI shows that physiologic stretch, such as that experienced by a myocyte during diastolic filling, dramatically alters Ca2+ spark occurrence transiently in normal cardiac ventricular myocytes. This behavior depends on microtubules affecting the release mechanisms of the sarcoplasmic reticulum (SR). Despite the importance of this new discovery one year ago, we have only now developed the additional tools needed to investigate how dynamic length changes can affect the triggering of Ca2+ sparks under diverse conditions. Using these new tools, we observe (in preliminary investigations) that stretch-dependent changes in Ca2+ sparks are even larger than previously observed and appear to arise from a transient increase in the sensitivity of ryanodine receptors (RyR2s). Additional preliminary work shows that, surprisingly, this transient increase in Ca2+ sparks underlies the activation of arrhythmogenic Ca2+ waves at a very low rate in heart cells from control mice, but at a much higher rate in myocytes from mdx mice, the murine model of Duchenne muscular dystrophy, or from control mice with excessive calcium in the SR. The tools developed by the PI and his colleagues will enable an innovative state-of-the-art investigation into how cardiac Ca2+ signaling is modulated by physiological stretch. The proposed work seeks to investigate stretch-dependent Ca2+ sparks and Ca2+ waves in 1. control ventricular myocytes; 2. ventricular myocytes in which RyR2 properties have been altered; 3. ventricular myocytes when microtubules are modulated; 4. ventricular myocytes from dystrophin null (mdx) mice. The planned research should reveal for the first time the importance of stretch in normal and pathological Ca2+ signaling of cardiac ventricular myocytes. The work will therefore provide not only fundamental new information on normal cellular behavior but also on mechanisms of arrhythmogenesis. Furthermore it will lay the foundation for novel therapies for diverse heart diseases including Duchenne muscular dystrophy. PUBLIC HEALTH RELEVANCE: Contraction and the heart rhythm are regulated by calcium inside of heart cells. This calcium level is now known to be set in part by changes in the cell length (these changes are also called "stretch"), a surprising result that was discovered recently by the scientists working on this proposal. The planned work will examine such stretch-dependent changes in cellular calcium and function and determine how stretch underlies normal and defective heart function.