Molecular Pathogenesis of Protein Surplus Cardiomyopathy

描述（由申请人提供）：PI实验室的广泛长期目标是帮助确定各种心脏病进展为充血性心力衰竭（CHF）的潜在机制。本研究拟分别建立模拟人结蛋白相关心肌病和高血压性心脏病的动物模型。虽然DRC不是一种常见的心脏病，但了解其发病机制将有助于了解许多常见的心脏病，特别是那些心肌细胞中异常蛋白质产生增加的心脏病。DRC是结蛋白相关性肌病（DRM）的心脏组成部分，通常由基因突变引起。DRM或DRC的特征在于肌细胞中异常的蛋白质聚集，并且这种聚集似乎在DRC发病机制中起核心作用。值得注意的是，在由常见形式的心脏病引起的人CHF中也观察到淀粉样蛋白低聚物形式的异常蛋白质聚集。最近在压力超负荷小鼠心脏中也观察到细胞内蛋白质聚集和蛋白水解紊乱。因此，从研究DRC中获得的致病见解可能为了解常见心血管疾病导致CHF的分子发病机制提供关键信息。泛素-蛋白酶体系统（UPS）负责大多数细胞蛋白质的降解，从而在细胞内蛋白质质量控制和几乎所有细胞功能的调节中发挥不可或缺的作用。在上一个项目期间，我们已经成功地揭示了严重的蛋白酶体（PSM）的损害异常蛋白质聚集在DRC小鼠心脏。值得注意的是，在许多其他心脏疾病的动物模型中也观察到psm功能障碍，包括压力超负荷心肌病。它也与大多数原因的人类CHF有关。然而，psm功能障碍在心脏的病理生理意义几乎是未知的，将是非常重要的定义。因此，我们提出了一个总体假设，即PSM介导的蛋白水解不充分在DRC和压力超负荷心肌病中起着重要作用，具体目的如下：（1）确定围产期或成年期发作的心肌细胞限制性PSM抑制（CR-PSMI）是否足以诱导小鼠心肌病及其可逆性;（2）研究中、重度CR-PSMI对小鼠心肌细胞内真正正常和异常蛋白质的清除的影响，探讨PSM介导的蛋白质水解与心肌细胞自噬的功能关系;（3）明确psm功能不全在DRC发病机制中的必要性;（4）明确psm功能不全在压力超负荷性心脏重构和心力衰竭中的作用。公共卫生相关性：充血性心力衰竭是几乎所有心脏病的最终共同途径，也是美国医疗保健中最昂贵的单一诊断。这是一种高度致命和致残的综合症。尽管其临床管理取得了最新进展，但它仍然是美国的主要死亡原因。这项研究项目将有助于加深我们对各种心脏病发展为充血性心力衰竭的分子机制的理解，最终将有助于寻找新的措施来预防或更有效地治疗这种常见但危及生命的疾病。

DESCRIPTION (provided by applicant): The broad long term goal of the PI's laboratory is to help define the mechanisms underlying the progression of various heart diseases to congestive heart failure (CHF). In the present proposal animal models mimic human desmin-related cardiomyopathy (DRC) and hypertensive heart disease will be respectively investigated. Although DRC is not a common heart disease but understanding its pathogenesis will shed lights on many common forms of heart disease, especially those with increased production of abnormal proteins in cardiomyocytes. DRC is the cardiac component of desmin-related myopathy (DRM) which is often caused by genetic mutations. DRM or DRC is characterized by aberrant protein aggregation in muscle cells and this aggregation appears to play a central role in DRC pathogenesis. Notably, abnormal protein aggregation in the form of amyloid oligomers was also observed in human CHF resulting from common forms of heart disease. Intracellular protein aggregation and proteolytic disturbance are recently observed also in pressure overloaded mouse hearts. Hence, pathogenic insights gained from studying DRC may provide critical information for understanding molecular pathogenesis of CHF resulting from common cardiovascular disease. The ubiquitin- proteasome system (UPS) is responsible for the degradation of most cellular proteins and thereby plays indispensible roles in intracellular protein quality control and the regulation of virtually all cellular functions. In the previous project period, we have successfully unveiled severe proteasome (psm) impairment by abnormal protein aggregation in DRC mouse hearts. Notably, psm dysfunction is also observed in animal models of many other cardiac disorders, including pressure overload cardiomyopathy. It has also been implicated in human CHF of most causes. However, the pathophysiological significance of psm dysfunction in the heart is virtually unknown and will be extremely important to be defined. Accordingly, we propose to test an overall hypothesis that the inadequacy in psm-mediated proteolysis plays an essential role in DRC and in pressure overload cardiomyopathy, by pursuing the following 4 Specific Aims: (1) To determine the sufficiency of perinatal or adult onset cardiomyocyte-restricted psm inhibition (CR-PSMI) to induce cardiomyopathy and its reversibility in mice; (2) To investigate the impact of moderate and severe CR-PSMI on the removal of bona fide normal and abnormal proteins in the heart and investigate the functional relationship between psm- mediated proteolysis and autophagy in cardiomyocytes in mice; (3) To determine the necessity of psm functional insufficiency in the pathogenesis of DRC in mice; and (4) To determine the role of psm dysfunction in pressure overload cardiac remodeling and failure in mice. PUBLIC HEALTH RELEVANCE: Congestive heart failure is the final common pathway of virtually all heart disease and is the most expensive single diagnosis in US health care. It is a highly lethal and disabling syndrome. Despite recent advances in its clinical management, it remains the leading cause of death in the US. This research project will help deepen our understanding on the molecular mechanisms underlying the progression of various heart diseases to congestive heart failure, which will ultimately facilitate the search for new measures to prevent or more effectively treat this common and yet life-threatening disorder.