Mechanisms directing adherens junctions and actin network interactions

 描述（由申请人提供）：细胞迁移和细胞-细胞粘附之间的平衡在发育过程中至关重要，并在疾病状态（如转移性癌症）中发生改变。细胞在发育过程中迁移到特定部位，当与其他细胞接触时;它们变得静止并分化成组织。因此，强的细胞-细胞粘附对于维持组织完整性是必要的。细胞-细胞粘附的变化在细胞更新或伤口愈合期间重新启动细胞迁移，或允许转移细胞分散到远处器官。细胞-细胞粘附复合物（adherens junctions）的形成和稳定对于后生动物的发育、器官形成和组织稳态是必不可少的，并且对于某些病理生理条件（如伤口愈合）也是必需的。相反，粘附连接的丧失是癌症的标志，导致不受限制的细胞增殖和转移。细胞-细胞粘附连接需要在浆细胞膜上正确组装多蛋白复合物。在这里，单跨膜钙粘蛋白受体的钙结合胞外域之间的同型相互作用允许相邻细胞相互结合。它们的胞质尾区与β-连环蛋白的相互作用，β-连环蛋白又与α-连环蛋白结合，似乎通过抑制板状足的产生来指导粘附连接的形成。然而，在没有张力的情况下，这种三元钙粘蛋白/β-连环蛋白/α-连环蛋白复合物不会直接结合到肌动蛋白网络，而肌动蛋白网络是稳定这些连接和组织稳态所必需的。在GM 094483资助的前3年，我们确定了二聚体全长人α-连环蛋白和黏着斑蛋白结合的α-连环蛋白的晶体结构，这些结构以及我们的生化和生物学研究确定了黏着斑蛋白-α-连环蛋白相互作用在粘附连接形成和稳定中的作用。通过从晶体结构和3D重建到生物化学，然后到生物学，拟议的研究将定义粘附连接如何稳定并控制肌动蛋白细胞骨架的组织。总的来说，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、迁移和细胞粘附的影响的理解。重要的是，我们的多学科研究也将为了解这些控制在肿瘤进展过程中如何丢失奠定基础，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.