Alpha-catenin function in cardiomyocyte adhesion and cytoskeletal organization

 描述(申请人提供)：人类心脏每天跳动超过100,000次，收缩力量对连接心肌细胞形成功能性心肌的蛋白质复合体提出了独特的物理和调节要求。心肌细胞之间的机械耦合和化学通讯是通过一种特殊的粘连结构实现的，这种结构被称为间盘(ICD)。ICD包括分别将肌动蛋白和中间丝细胞骨架连接到质膜的黏附连接和桥粒。ICD的形成需要多种黏附和细胞骨架蛋白，这些蛋白的突变可导致心肌病。然而，关于这些黏附复合体是如何组装或调节以抵抗心肌细胞收缩和维持组织完整性的，人们知之甚少。确定蛋白质复合体在ICD中如何发挥作用以维持黏附平衡，对于了解心脏功能和疾病至关重要。粘着连接的核心是钙粘连蛋白-连环蛋白复合体，它通过α-连环蛋白与肌动蛋白细胞骨架相连。α-连环蛋白是一种多功能肌动蛋白结合蛋白，定位于心肌细胞内的胞浆内，α-连环蛋白功能缺失可导致心肌病。然而，α-连环蛋白在心肌细胞细胞间黏附中的作用还知之甚少。我们假设α-连环蛋白通过将肌动蛋白和中间丝偶联到ICD连接复合体来调节心肌细胞-细胞间的黏附。在这个提案中，我们试图1)确定肌动蛋白张力如何调节心肌细胞中的粘连连接组装和组织；2)确定αT-连环蛋白的分子特性如何调节粘连连接组织和与肌动肌球蛋白网络的连接；3)确定αT-连环蛋白如何与肌动蛋白和中间丝细胞骨架连接以调节心肌细胞的黏附。我们的工作将开发新的工具，获得关于心肌细胞细胞间黏附的分子机制的新知识，这反过来将为评估ICD蛋白突变对心脏病理生理的影响提供基础，并为开发治疗心肌疾病的新策略提供信息。

 DESCRIPTION (provided by applicant): The human heart beats upwards of 100,000 times a day, and contractile forces place unique physical and regulatory demands on the protein complexes that join cardiomyocytes together to form a functional heart muscle. Mechanical coupling and chemical communication between cardiomyocytes is accomplished through a specialized adhesive structure called the intercalated disc (ICD). The ICD comprises adherens junctions and desmosomes that connect the actin and intermediate filament cytoskeletons, respectively, to the plasma membrane. ICD formation requires multiple adhesion and cytoskeletal proteins, and mutations in these proteins can cause cardiomyopathies. However, little is known about how these adhesive complexes are assembled or regulated to withstand the forces of cardiomyocyte contraction and maintain tissue integrity. Determining how protein complexes function at the ICD to maintain adhesive homeostasis is critical for understanding heart function and disease. The core of the adherens junction is the cadherin-catenin complex, which is connected to the actin cytoskeleton through α-catenin. α-Catenin is multifunctional actin-binding protein that localizes to the ICD in cardiomyocytes, and loss of α-catenin function in mice causes cardiomyopathy. However, α-catenin functions in cell-cell adhesion in cardiomyocytes are poorly understood. We hypothesize that α-catenin regulates cardiomyocyte cell-cell adhesion by coupling actin and intermediate filaments to ICD junctional complexes. In this proposal, we seek to 1) define how actomyosin tension regulates adherens junction assembly and organization in cardiomyocytes; 2) identify how the molecular properties of αT-catenin, a largely uncharacterized α-catenin expressed in the heart, regulate adherens junction organization and linkage to the actomyosin network; and 3) determine how αT-catenin links to actin and intermediate filament cytoskeletons to regulate cardiomyocyte adhesion. Our work will develop new tools and acquire new knowledge about the molecular mechanisms of cell-cell adhesion in cardiomyocytes, which in turn will provide the foundation for assessing the impact of mutations in ICD proteins on cardiac pathophysiology and inform the development of new strategies for the treatment of cardiomyopathies.