Integrins and Caveolin Proteins in Cardiac Hypertrophy and Failure

描述（由申请人提供）：心肌细胞（CM）感知机械变化并将其转化为生化和功能作用的机制尚不清楚。CM内的两个区域对适当的机械转导似乎至关重要，它们是具有常驻整联素（ITGs）的costamere，以及具有相关Caveolin （Cav）蛋白的瓶状膜内陷。我们和其他人已经开始证明CM ITGs和Cav蛋白在机械信号转导中的重要性，并且ITGs和Cav3的表达减少和/或突变可引起心肌病。ITGs和Cav-3如何在功能上相互作用，以及它们的协调反应通过什么机制在CM中传递机械信号尚不清楚。我们已经建立了¿1 ITG cm特异性敲除（KO）（称为¿1cKO）， Cav-3KO和cm特异性ITG和Cav-3转基因（Tg）小鼠模型。我们的初步数据表明，ITG和Cav-3在成人CM中共定位和共免疫沉淀，当心脏受到机械负荷增加的挑战时，ITG和Cav-3蛋白在CM中的表达增加都可以保护心肌功能。基于这些数据，我们提出了我们的总体假设：A) ITGs和Cav-3在CM机械转导所需的蛋白质组织中具有协同特性；B) CM中这两种蛋白质的表达增加将保护心力衰竭引起的血流动力学负荷增加的心脏。我们将使用功能丧失和功能获得的方法来实现这一目标：1)通过单独或联合使用Cav3缺失和¿1 ITG心肌细胞特异性敲除小鼠，确定¿1 ITG和小室蛋白-3在心肌机械传导反应中的作用。我们将评估当ITGs、Cav-3或这两种蛋白质从CM中丢失时，急性和慢性机械介导的信号是如何改变的，以及这些蛋白质的丢失如何改变心脏肥大和向HF表型演变的重塑过程。2)明确指导心肌细胞ITG和Cav-3协同机械信号传导的相互作用。将评估ITGs和Cav3与海岸蛋白和细胞骨架蛋白之间的直接相互作用。然后，蛋白质组学将鉴定与ITGs或Cav3相互作用的新蛋白质，以及CM的空泡和非空泡生化部分中的蛋白质如何随着血流动力学挑战而变化。3)确定Cav-3和/或ITGs的Tg过表达如何改变机械反应，延迟或保护心脏免受肥厚诱导的心力衰竭。这将使我们能够直接测试Cav3和¿1 ITGs在机械损伤心肌中的潜在治疗作用。临床意义：各种原因的心衰患者较多，需要频繁的住院和门诊治疗。确定心功能障碍的根本原因，重要的是，研究可能导致这种常见疾病的新疗法，是必不可少的，这将是本提案的重点。

DESCRIPTION (provided by applicant): The mechanisms by which the cardiac myocyte (CM) senses mechanical changes and converts it to biochemical and functional effects, are poorly understood. Two areas within the CM that appear critical for proper mechanotransduction are the costamere with its resident integrins (ITGs), and caveolae, flask-shaped membrane invaginations with associated Caveolin (Cav) proteins. We and others have begun to show the importance of CM ITGs and Cav proteins in transducing mechanical signals, and that reduced expression and/ or mutation of ITGs and Cav3 can cause cardiomyopathies. How ¿1 ITGs and Cav-3 functionally interact and by what mechanisms their coordinated responses transduce mechanical signals in the CM are unknown. We have generated ¿1 ITG CM-specific knockout (KO) (termed ¿1cKO), Cav-3KO and CM-specific ITG and Cav-3 transgenic (Tg) mouse models. Our preliminary data shows that ¿1 ITG and Cav-3 co-localize and co-immunoprecipitate in the adult CM and that increased expression of ITGs and Cav-3 proteins in CMs can both preserve myocardial function when the heart is challenged with an increased mechanical load. Based on this data, we formulated our overall hypotheses that: A) ¿1 ITGs and Cav-3 have cooperative properties in organization of proteins required for CM mechanotransduction and B) that increased expression of both of these proteins in the CM will protect the heart challenged with an increased hemodynamic load from HF. We will pursue this with 3 aims using loss and gain of function approaches: 1) Determine roles of ¿1 ITGs and caveolin-3 in mechanotransductive responses of the myocardium by use of Cav3 null and ¿1 ITG cardiac myocyte specific knockout mice alone, or in combination. We will evaluate how acute and chronic mechanically mediated signals are altered when ITGs, Cav-3 or both proteins are lost from the CM and how loss of these proteins modifies the remodeling process as the heart hypertrophies and evolves towards a HF phenotype. 2) Define the interactions which direct cooperative mechanical signaling of cardiomyocyte ¿1 ITG and Cav-3. Direct interactions between ITGs and Cav3, with costameric and cytoskeletal proteins will be assessed. Proteomics will then identify novel proteins which interact with ITGs or Cav3, and how proteins in the caveolar and non-caveolar biochemical fraction of the CM change with hemodynamic challenge. 3) Determine how Tg overexpression of Cav-3 and/ or ¿¿1 ITGs alters mechanical responses, and delays or protects the heart from cardiac failure in the face of hypertrophic induction. This will allow us to directl test the potential therapeutic roles of Cav3 and ¿1 ITGs in the mechanically challenged myocardium. Clinical Significance: HF of varied causes is found in a large number of patients, necessitating frequent inpatient and outpatient care. Identification of root causes of cardiac dysfunction and importantly, studies which could lead to novel therapeutics of this common disease, are essential, and will be the focus of this proposal.