Integrin Function in Cardiac Remodeling

描述(申请人提供)：整合素是粘附性受体和信号分子。人们对它们在心脏中的作用知之甚少。21整合素是在心肌细胞和成纤维细胞中表达的主要的2整合素亚基，并与这些细胞类型中的几个1亚基配对。目前这项提议的总体假设是，心肌细胞和成纤维细胞整合素是心脏内信号和结构的关键组织者。了解这些细胞受体的功能将使我们更好地了解心脏在血流动力学或缺血应激后如何重塑。利用独特的小鼠模型和从中衍生出来的细胞，这项建议将集中于三个目标：1)确定心肌细胞中机械信号转导缺陷的机制(S)以及整合素和G蛋白偶联受体通路之间信号串扰的调节：专注于小窝和粘着斑蛋白。21整合素在心肌细胞中的表达减少会导致压力负荷下心脏和异丙肾上腺素刺激的心肌细胞下游信号的改变。我们将验证一种假设，即心肌细胞整合素的减少可以通过干扰多个亚细胞信号整合子-例如局灶性粘连和小凹-来改变机械和肾上腺素能信号，并且干扰的下游信号可能通过粘着斑激酶依赖和独立的途径发生。2)探讨心肌细胞整合素在短期缺血再灌流和心肌梗死后的作用。心肌细胞表面21个整合素的减少导致心脏在缺血/再灌流时的异常功能反应，而心肌细胞上整合素的过度表达提供了缺血保护。为了达到这个目的，我们将使用心肌细胞整合素表达减少或过表达的转基因小鼠模型来评估将整合素表达水平与心肌缺血功能障碍/保护联系起来的机制(S)。这里的工作将与目标3中的心脏成纤维细胞的研究联系在一起。我们假设整合素异源二聚体改变了膜的稳定性或心肌细胞的信号转导，从而改变了心脏对缺血或梗塞的反应。3)探讨21整合素在心肌纤维化和成纤维细胞功能中的作用：小鼠心脏发生纤维化，心肌细胞21整合素表达减少。这一目标将确定导致这种表型的机制(S)，特别是在病理性心脏(例如，心肌梗死后)，并研究心肌细胞与成纤维细胞的相互作用。这里要检验的假设是，肌细胞上整合素表达的改变会导致成纤维细胞的旁分泌效应，而成纤维细胞上整合素表达水平的改变将在功能上影响成纤维细胞，并潜在地影响成纤维细胞-肌成纤维细胞的转化。

DESCRIPTION (provided by applicant): Integrins are adhesive receptors and signaling molecules. Their role in the heart is poorly understood. 21 integrin is the dominant 2 integrin subunit expressed in cardiac myocytes and fibroblasts and partners with several 1 subunits in each of these cell types. The overall hypothesis of the current proposal is that cardiac myocyte and fibroblast integrins are critical organizers of signaling and structure within the heart. Knowledge of the function of these cellular receptors will allow us to establish a greater understanding of how the heart remodels following hemodynamic or ischemic stresses. Using unique mouse models and cells derived from them, this proposal will focus on three aims: 1) To determine the mechanism(s) for defective mechanical signaling and modulation of signaling crosstalk between integrin and G-protein coupled receptor pathways in the cardiac myocyte: focus on caveolae and focal adhesion proteins. Reduced 21 integrin expression in the cardiac myocyte leads to alterations in downstream signaling in heart subjected to pressure loading and in isolated myocytes stimulated with isoproterenol. We will test the hypothesis that reduction of myocyte integrins can alter mechanical and adrenergic signaling by disturbing multiple sub-cellular signaling integrators - e.g. focal adhesions and caveolae, and that disturbed downstream signaling may occur through both focal adhesion kinase dependent and independent pathways. 2) To evaluate the role of myocyte integrins in short-term ischemia / reperfusion and following myocardial infarction. Reduction of 21 integrins on the myocyte cell surface leads to abnormal functional responses of the heart subjected to ischemia / reperfusion while overexpression of integrins on the myocyte offers ischemic protection. In this aim the mechanism(s) which links integrin expression levels to myocardial ischemic dysfunction / protection will be evaluated using genetically manipulated mouse models where myocyte integrins are reduced or overexpressed. Work here will tie to studies of cardiac fibroblasts in aim 3. We hypothesize that integrin heterodimers modify membrane stability or myocyte signaling which alters responses of the heart to ischemia or infarction. 3) To assess the role of 21 integrins in cardiac fibrosis and fibroblast function: Fibrosis occurs in the murine heart with reduced myocyte expression of 21 integrin. This aim will determine the mechanism(s) which lead to this phenotype, particularly in the pathological heart (e.g. post-myocardial infarction) and study myocyte: fibroblast interactions. The hypotheses to be tested here will be that alteration of integrin expression on the myocyte leads to paracrine effects on the fibroblast and that altered 21 integrin expression levels on the fibroblast will functionally affect the fibroblast and potentially fibroblast- myofibroblast conversion.