Abnormal intracellular calcium release in heart failure

摘要 心力衰竭（HF）一直是医疗保健的主要挑战。改变的肌细胞钙（Ca）信号传导是一种 HF病理生理学的重要组成部分，在寻找新的有效疗法中具有重要意义。 尽管在阐明钙依赖性过程发生在快速的时间尺度上的进展， 其中Ca调节缓慢的心脏过程，包括对生理和病理的长期适应， 压力，仍然知之甚少。这一进展的关键障碍是由于我们对以下问题的认识不足： 心肌细胞生物学的基础方面，包括蛋白质合成、加工 和交付。由于缺乏探测和跟踪较慢/长寿命的技术工具， 活的心肌细胞中的分子过程。钙池操作性钙内流（SOCE），其中细胞内钙耗竭 钙库促使细胞外钙进入胞质溶胶，最近已成为一个重要组成部分， 心肌细胞Ca信号传导。SOCE由基质相互作用分子（STIM 1）介导， 感受肌浆网/内质网（SR/ER）Ca耗竭，与肌膜Ca相互作用并激活肌膜Ca- 释放激活通道蛋白（ORAI 1）。据报道，STIM 1在适应不良中起着关键作用。 肥厚然而，STIM 1促进肥大的机制及其在适应性细胞中的作用尚不清楚。 肥大（运动诱导）仍有待阐明。最近，我们发现SOCE及其分子 机器位于细胞与细胞的接触部位，即闰盘（ID）。根据初步结果， 我们提出了一个新的假设，即SOCE通过促进局部的 在ID处从专用的mRNA池合成蛋白质。事实上，正常心脏中的SOCE可能是最佳的 调节以实现适应性肥大反应的“金发区”，如由运动诱导的。与此相反， SOCE的病理性失调可能是有害的。具体来说，疾病中的SOCE过度活动可能 是适应不良性肥大的基础，从而导致诸如应激性心肌病（SCM）的现象。 在这项提案中，我们将使用尖端的细胞生理学和分子技术（包括超 分辨率显微镜，新的细胞报告系统）和新的遗传小鼠模型来测试这些 假设和确定关键的细胞微和纳米结构域，以及参与SOCE的分子步骤， 驱动肌细胞生长。我们还将研究是否有可能把目标对准国家社会经济合作机制的关键组成部分 （具体地，STIM 1 L，STIM 1的长剪接变体）介导适应不良性肥大。为此我们 提出以下具体目标：1）明确SOCE在适应性和适应不良性肥大中的作用。（二） 定义SOCE调节肥大的亚细胞和分子机制; 3）定义 SOCE在应激性肥厚性心脏病中的作用及机制这些研究将产生新的 深入了解生理和病理性肥大的机制，并为 新的机制为基础的治疗异常心脏结构和功能。

ABSTRACT Heart failure (HF) continuous to be a major health care challenge. Altered myocyte calcium (Ca) signaling is an essential part of the pathophysiology of HF and of critical relevance in the search for new effective therapies. Despite progress in the elucidation of Ca-dependent processes occurring on rapid time scales, mechanisms whereby Ca modulates slow cardiac processes, including long term adaptations to physiological and pathological stress, remain poorly understood. This critical barrier to progress is attributable to our poor understanding of foundational aspects of cardiomyocyte biology, including sites and mechanisms of protein synthesis, processing and delivery. This is compounded by the lack of technological tools for probing and tracking slower / long-lived molecular process in living myocytes. Store-operated Ca entry (SOCE), wherein depletion of intracellular Ca stores prompts extracellular Ca entry into the cytosol, has recently emerged as an important component of cardiomyocyte Ca signaling. SOCE is mediated by the stromal interaction molecule (STIM1), which, upon sensing sarco/endoplasmic reticulum (SR/ER) Ca depletion, interacts with and activates the sarcolemmal Ca- release activated channel protein (ORAI1). STIM1 has been reported to play a critical role in maladaptive hypertrophy. However, the mechanism whereby STIM1 contributes to hypertrophy and its role in adaptive hypertrophy (exercise-induced) remain to be elucidated. Recently, we discovered that SOCE and its molecular machinery are localized at the cell-to-cell contact sites, the intercalated discs (IDs). Based on preliminary results, we put forth a novel hypothesis that SOCE promotes myocyte longitudinal growth through facilitation of localized protein synthesis from a dedicated pool of mRNAs at the IDs. Indeed, SOCE in the normal heart may be optimally tuned to achieve a “Goldilocks zone” of adaptive hypertrophic response, as induced by exercise. In contrast, pathological dysregulation of SOCE may prove deleterious. Specifically, SOCE over-activity in disease may underlie maladaptive hypertrophy, thus leading to phenomena such as stress-induced cardiomyopathy (SCM). In this proposal, we will use cutting-edge cellular physiology and molecular techniques (including super- resolution microscopy, novel cellular reporter systems) and novel genetic mouse models to test these hypotheses and determine key cellular micro- and nanodomains, as well as molecular steps involved in SOCE- driven myocyte growth. We will also examine the possibility of targeting key components of the SOCE machinery (specifically, STIM1L, the long splice variant of STIM1) that mediate maladaptive hypertrophy. To this end, we propose the following specific aims: 1) Define the role of SOCE in adaptive and maladaptive hypertrophy. 2) Define subcellular and molecular mechanisms underlying modulation of hypertrophy by SOCE; and 3) Define the role and mechanism of SOCE in stress-induced hypertrophic cardiac disease. These studies will yield new insights into the mechanisms underlying physiological and pathological hypertrophy and provide a foundation for new mechanism-based therapies for abnormal cardiac structure and function.