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效应的机制尚不清楚。CM内的两个区域对于适当的机械转导似乎是关键的，它们是具有其驻留整联蛋白（ITG）的肋节和小窝，具有相关小窝蛋白（Cav）蛋白的烧瓶形膜内陷。我们和其他人已经开始显示CM ITGs和Cav蛋白在转导机械信号中的重要性，并且ITGs和Cav 3的表达减少和/或突变可以引起心肌病。ITGs和Cav-3在功能上如何相互作用，以及它们在CM中协调响应机械信号的机制是未知的。我们已经产生了<$1ITG CM特异性敲除（KO）（称为<$1cKO）、Cav-3 KO和CM特异性ITG和Cav-3转基因（Tg）小鼠模型。我们的初步数据显示，在成人CM中，ITG和Cav-3共定位和共免疫沉淀，并且当心脏受到增加的机械负荷的挑战时，CM中ITG和Cav-3蛋白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）ITG和Cav-3在CM机械转导所需的蛋白质的组织中具有协同特性，以及B）CM中这两种蛋白质的表达增加将保护受到HF增加的血液动力学负荷挑战的心脏。我们将使用功能丧失和获得方法以3个目标追求这一点：1）通过单独或组合使用Cav 3缺失和<$1ITG心肌细胞特异性敲除小鼠来确定<$1ITG和小窝蛋白-3在心肌的机械转导应答中的作用。我们将评估当ITGs、Cav-3或这两种蛋白从CM中丢失时，急性和慢性机械介导的信号是如何改变的，以及这些蛋白的丢失如何随着心脏肥大而改变重塑过程并向HF表型演变。2)定义直接心肌细胞ITG和Cav-3的合作机械信号的相互作用。将评估ITG和Cav 3与costameric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ITG或Cav 3相互作用的新型蛋白质，以及CM的小窝和非小窝生化组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，并延迟或保护心脏在肥大诱导时免于心力衰竭。这将使我们能够直接测试Cav 3和NTG在机械挑战心肌中的潜在治疗作用。临床意义：在大量患者中发现各种原因的HF，需要频繁的住院和门诊治疗。确定心功能不全的根本原因，重要的是，可能导致这种常见疾病的新疗法的研究是必不可少的，并将成为本提案的重点。

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.