Mechanisms directing adherens junctions and actin network interactions

 描述(由申请人提供)：细胞迁移和细胞间黏附之间的平衡在发育过程中至关重要，在转移性癌症等疾病状态下会发生变化。细胞在发育过程中与其他细胞接触时会迁移到特定的位置；它们会变得静止，并分化成组织。因此，强大的细胞间黏附对于维持组织的完整性是必要的。细胞间黏附的变化在细胞周转或伤口愈合过程中重新启动细胞迁移，或者允许转移的细胞分散到远处的器官。细胞-细胞黏附复合体(黏附连接)的形成和稳定对后生动物的发育、器官发生和组织动态平衡是必不可少的，也是一些病理生理条件，如伤口愈合所必需的。相比之下，黏附连接的丧失是癌症的一个标志，导致细胞不受限制地增殖和转移。细胞-细胞黏附连接需要在质细胞膜上适当地组装多蛋白复合体。在这里，单个跨膜通过钙粘附素受体的钙结合外区之间的同型相互作用允许相邻细胞相互结合。它们的细胞质尾部结构域与β-连环蛋白的相互作用，进而与α-连环蛋白结合，似乎通过抑制板孔的产生来指导粘连连接的形成。然而，在没有张力的情况下，这种三元钙粘素/β-连环蛋白/α-连环蛋白复合体不会直接与肌动蛋白网络结合，而肌动蛋白网络是稳定这些连接和组织动态平衡所必需的。在GM094483资助的头三年中，我们测定了全长人α-连环蛋白二聚体的晶体结构和与纽蛋白结合的α-连环蛋白的晶体结构，这些结构和我们的生化和生物学研究确定了纽蛋白-α-连环蛋白相互作用在粘连连接形成和稳定中的作用。通过从晶体结构和3D重建转向生物化学，然后再到生物学，拟议的研究将定义附着连接是如何稳定的，并控制肌动蛋白细胞骨架的组织。总之，我们提出的研究将显著增加我们对α-连环蛋白单体-二聚体转变及其对膜动力学、迁移和细胞黏附的影响的理解。重要的是，我们的多学科研究也将为了解这些控制如何在肿瘤进展过程中丢失奠定基础，并可能为治疗干预提供新的途径。

 DESCRIPTION (provided by applicant): The balance between cell migration and cell-cell adhesion is crucial during development and is altered in disease states such as metastatic cancers. Cells migrate during development to specific sites when upon contact with other cells; they become stationary and differentiate into tissues. Thus, strong cell-cell adhesion is necessary in maintaining tissue integrity. Changes in cell-cell adhesion reinitiate cell migration during cell turnover or wound healing or allow metastatic cells to scatter to distant organs. The formation and stabilization of cell-cell adhesion complexes (adherens junctions) is essential for metazoan development, organogenesis, and tissue homeostasis, and it also necessary for some pathophysiological conditions, such as wound healing. In contrast, loss of adherens junctions is a hallmark of cancer, leading to unrestricted cell proliferation and metastasis. Cell-cell adherens junctions require the proper assembly of multi-protein complexes at the plasma cell membrane. Here, homotypic interactions between the calcium-binding ectodomains of single transmembrane pass cadherin receptors allow neighboring cells to bind to one another. The interactions of their cytoplasmic tail domains with β-catenin, which in turn binds to α-catenin, appear to direct the formation of adherens junctions, by inhibiting the production of lamellopodia. However, without tension, this ternary cadherin/β-catenin/α-catenin complex does not bind directly to the actin network, which is necessary for stabilizing these junctions and for tissue homeostasis. In the first 3 years of funding by GM094483, we determined the crystal structure of dimeric full-length human α-catenin and of vinculin-bound α-catenin, and these structures and our biochemical and biological studies defined the roles of the vinculin-α-catenin interaction in the formation and stabilization of adherens junctions. By moving from crystal structures and 3D reconstructions to biochemistry and then to biology, the proposed studies will define how adherens junctions are stabilized and control the organization of the actin cytoskeleton. Collectively, our proposed studies will significantly increase our understanding of α-catenin monomer-dimer transitions and their effects on membrane dynamics, migration, and cell adhesion. Importantly, our multi-disciplinary studies will also lay the foundation for understanding how these controls are lost during tumor progression and may suggest new avenues for therapeutic intervention.