Human Cardiomyopathy and HSP60

描述(由申请者提供)：近500万美国人患有心力衰竭，每年有40万新诊断病例。大多数治疗的目的是阻止心力衰竭的螺旋式下降，但尽管人们积极尝试剖析其潜在机制，但仍有许多事情需要了解。热休克蛋白(HSP)是一个普遍存在的内源性保护性蛋白家族，在物种间具有高度的序列保守性。以前，我们观察到保护心脏的HSP60，通常是线粒体和胞浆蛋白，在衰竭的人心脏中异常定位于质膜。我们已经确定，大鼠心肌细胞的急性缺氧性损伤促使胞浆HSP60移位到质膜上。在正常心脏中，胞浆中的HSP60与促凋亡的Bax形成复合体，而HSP60的减少将促进心肌细胞的凋亡。我们的中心假设是HSP60的膜定位介导了心肌细胞的损伤和细胞死亡。我们特别假设细胞应激/损伤导致胞浆HSP60的磷酸化/肉豆蔻酸化，导致HSP60移位到质膜，我们将从三个特定的目的来解决这一假说：1.确定应激条件下HSP60移位到质膜的机制。确定HSP60的修饰是导致损伤后细胞定位改变的原因，并精确定位所观察到的修饰所涉及的信号通路。2.应激状态下热休克蛋白60的膜定位功能--应激状态下热休克蛋白60从细胞质转位到质膜。我们假设热休克蛋白60在膜上的存在对心脏有害，并将通过表达在心肌细胞中定位改变的突变热休克蛋白60来验证这一点。我们还将确定与HSP60相互作用的膜蛋白。3.确定HSP60/Bax相互作用的机制--HSP60和Bax在胞浆中形成复合体。我们推测，HSP60和Bax之间的这种相互作用对于防止细胞凋亡是重要的。这种相互作用的潜在调节机制尚不清楚，将在计划中的实验中确定。在计划的工作中，我们将研究HSP60功能的一个新方面--它在应激/损伤下从胞浆到质膜的移位，以及这种移位对心肌细胞功能和活力的影响。关键问题是HSP60向质膜的移动是否是损伤的原因还是结果。这些实验将有助于描述HSP60膜的运动是否单独会导致细胞死亡，以及阻止运动是否会阻止细胞死亡。这项研究的长期目标是进一步了解心力衰竭进展的机制。

DESCRIPTION (provided by applicant): Nearly 5 million Americans have heart failure, with 400,000 new cases diagnosed annually. Most treatment is aimed at stemming the downward spiral of heart failure, but despite vigorous attempts to dissect the underlying mechanisms, much remains to be understood. The heat shock proteins (HSP) are a ubiquitous family of endogenous, protective proteins with high sequence conservation across species. Previously, we observed that the cardioprotective HSP60, normally a mitochondrial and cytosolic protein, is abnormally localized in the plasma membrane in the failing human heart. We have determined that acute hypoxic injury in rat cardiac myocytes precipitates translocation of cytosolic HSP60 to the plasma membrane. Cytosolic HSP60 complexes with the pro-apoptotic bax in the normal heart, and reduction in HSP60 will precipitate myocyte apoptosis. Our central hypothesis is that membrane localization of HSP60 mediates cardiac myocyte damage and cell death. We specifically hypothesize that cellular stress/injury causes phosphorylation/myristoylation of cytosolic HSP60 resulting in HSP60 translocating to the plasma membrane, We will address this hypothesis with three Specific Aims: 1. Determine the Mechanism of Translocation of HSP60 to the Plasma Membrane with Stress. Identify modifications of HSP60 that account for change in cellular localization with injury, and pinpoint signaling pathways involved in the observed modifications. 2. Determine the Function of Membrane Localization of HSP60 with Stress - HSP60 translocates from the cytoplasm to the plasma membrane with stress. We hypothesize that the presence of HSP60 in the membrane is detrimental to the heart, and will test this by expressing mutated HSP60 with altered localization in myocytes. We will also identify membrane proteins that interact with HSP60. 3. Define the Mechanism of the HSP60/bax Interaction - HSP60 and bax form a complex in the cytosol. We postulate that this interaction between HSP60 and bax is important for preventing apoptosis. The underlying mechanism of regulation of this interaction is unknown, and will be identified in the planned experiments. In the planned work, we will study a novel aspect of HSP60 function - its translocation with stress/injury from the cytosol to the plasma membrane, and the effect of this migration on cardiac cell function and viability. The key issue is whether the movement of HSP60 to the plasma membrane is a cause vs. a consequence of injury. These experiments will help delineate whether movement of HSP60 the membrane alone will precipitate cell death, and whether preventing movement will prevent cell death. The long-term goal of this research initiative is to further understand the mechanisms underlying heart failure's progression.