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的 收缩的力量，同时保持粘合剂的动态平衡。心肌细胞由端到端的 间盘(ICD)，一种协调细胞信号的特殊连接，电气和机械 行动。ICD由连接肌动蛋白和肌动蛋白的黏附连接(AJ)和桥粒组成 相邻细胞的中间丝细胞骨架。ICD功能需要多重粘接 细胞骨架蛋白和这些蛋白的突变与心肌病有关。然而，相对来说， 关于黏附复合体如何调节以建立和维持心脏组织的完整性，人们知之甚少。 粘着连接的核心是钙粘附素-连环蛋白复合体，它与肌动蛋白相连。 通过a-连环蛋白的细胞骨架。A-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细胞间黏附中的作用是 人们对此知之甚少。我们在这一应用中的目标是确定机械和分子输入是如何 通过人类心脏中表达的两种a-连环蛋白-AE(上皮型)-连环素和(睾丸)-连环素-进行转导 连环蛋白--调节心肌细胞黏附。我们的理论基础是定义个人和集体的角色 α-连环蛋白在心肌细胞AJs中的表达将为了解心肌细胞AJs如何平衡提供基础 机械和信号功能。我们推测AE-连环蛋白和AT-连环蛋白形成独特的钙粘连蛋白- 连环蛋白复合体响应细胞提示发挥ICD组装和机械检查点的作用 心肌细胞组织。在这项建议中，我们寻求：1)定义调节- 连环蛋白配体与心肌细胞AJ的结合；2)决定a-连环蛋白的配基募集如何促进AJ 装配和细胞骨架附着；以及3)确定外部机械信号如何调节AJ组织。 通过我们的研究将获得的知识包括详细的、机械地理解a-连锁素是如何 心肌细胞黏附的分子特性被调整；独特的分子复合体是如何构建的 沿心肌细胞AJ建立和维持黏附；以及外部机械信号如何进入 心肌细胞AJ来驱动组织。这一全面、多尺度的分析将开发新的工具 并获得有关心肌细胞黏附的分子机制的新知识。 了解心肌细胞黏附的基本机制是确定 ICD蛋白突变如何导致心脏病，并为开发治疗心脏病的新策略提供信息 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.