Alpha-catenin function in cardiomyocyte adhesion and cytoskeletal organization

项目摘要 随着每一次心跳，连接心肌细胞的连接复合体必须传递机械信号， 收缩力，同时保持粘附稳态。心肌细胞是通过 闰盘（ICD），一种专门的连接，协调细胞信号，电和机械 运营ICD包括粘附连接（AJs）和连接肌动蛋白和肌动蛋白的桥粒。 中间丝细胞骨架，分别相邻的细胞。ICD功能需要多处粘连 细胞骨架蛋白和这些蛋白的突变与心肌病有关。但相对 关于如何调节粘附复合物以建立和维持心脏组织完整性知之甚少。 粘附连接的核心是钙粘蛋白-连环蛋白复合物，它与肌动蛋白连接。 细胞骨架通过α-连环蛋白。α-连环蛋白是一种多功能的机械反应性肌动蛋白结合蛋白， 定位于心肌细胞ICD。然而，α-连环蛋白在心肌细胞中的细胞-细胞粘附中的功能是不稳定的。 不太了解。我们在这个应用中的目标是确定机械和分子输入是如何 通过人心脏中表达的两种α-连环蛋白-α E（上皮）-连环蛋白和α T（睾丸）-连环蛋白转导。 连环蛋白-调节心肌细胞粘附。我们的理论基础是， 在心肌细胞AJs上的α-连环蛋白的表达将为心肌细胞AJs如何平衡提供基本的见解 机械和信号功能。我们假设aE-连环蛋白和aT-连环蛋白形成独特的钙粘蛋白， 连环蛋白复合物响应于细胞信号，作为ICD组装的机械检查点， 心肌组织在这个建议中，我们寻求：1）定义调节a-的变构机制- 在心肌细胞AJ处的连环蛋白配体结合; 2）确定配体募集至α-连环蛋白如何促进AJ 组装和细胞骨架附着; 3）确定外部机械线索如何调节AJ组织。 通过我们的研究获得的知识包括对α-连环蛋白如何 心肌细胞粘附的分子特性被调整;独特的分子复合物是如何构建的 沿着心肌细胞AJ建立和维持粘附;以及外部机械线索如何影响 心肌细胞AJ来驱动组织。这种全面的多尺度分析将开发新的工具 并获得有关心肌细胞中细胞粘附的分子机制的新知识。 了解心肌细胞中细胞粘附的基本机制对于确定 ICD蛋白的突变如何导致心脏病，并为发展新的治疗策略提供信息。 心肌病的治疗。

Project Summary With every heartbeat, the junctional complexes that couple cardiomyocytes must transmit the mechanical forces of contraction while maintaining adhesive homeostasis. Cardiomyocytes are linked end-to-end by the intercalated disc (ICD), a specialized junction that coordinates cell signaling, electrical and mechanical operations. The ICD comprises adherens junctions (AJs) and desmosomes that connect the actin and intermediate filament cytoskeletons, respectively, of adjoining cells. ICD function requires multiple adhesion and cytoskeletal proteins and mutations in these proteins are linked to cardiomyopathies. However, relatively little is known about how adhesion complexes are regulated to establish and maintain heart tissue integrity. The core of the adherens junction is the cadherin-catenin complex, which is connected to the actin cytoskeleton through a-catenin. a-Catenin is a multifunctional, mechanoresponsive actin-binding protein that localizes to the cardiomyocyte ICD. However, a-catenin functions in cell-cell adhesion in cardiomyocytes are poorly understood. Our objective in this application is to determine how mechanical and molecular inputs are transduced through the two a-catenins expressed in the human heart – aE(Epithelial)-catenin and aT(Testes)- catenin – to regulate cardiomyocyte adhesion. Our rationale is that defining the individual and collective roles of a-catenin at cardiomyocyte AJs will provide fundamental insight into how cardiomyocyte AJs balance mechanical and signaling functions. We hypothesize that aE-catenin and aT-catenin form unique cadherin- catenin complexes in response to cellular cues to function as mechanical checkpoints for ICD assembly and cardiomyocyte organization. In this proposal, we seek to: 1) define the allosteric mechanisms that regulate a- catenin ligand binding at the cardiomyocyte AJ; 2) determine how ligand recruitment to a-catenin promotes AJ assembly and cytoskeletal attachment; and 3) identify how external mechanical cues regulate AJ organization. Knowledge to be gained through our studies include a detailed, mechanistic understanding of how a-catenin molecular properties are tuned for adhesion in cardiomyocytes; how unique molecular complexes are built along the cardiomyocyte AJ to establish and maintain adhesion; and how external mechanical cues feed into the cardiomyocyte AJ to drive organization. This comprehensive, multiscale analysis will develop new tools and acquire new knowledge about the molecular mechanisms of cell adhesion in cardiomyocytes. Understanding the fundamental mechanisms of cell adhesion in cardiomyocytes is necessary for determining how mutations in ICD proteins lead to heart disease and inform the development of new strategies for the treatment of cardiomyopathies.