BIOCHEMISTRY AND REGULATION OF CADHERIN ACTIVITY

钙粘蛋白是一种嗜同性细胞粘附蛋白，对组织中细胞的组织化非常重要。钙粘蛋白粘附特异性有助于发育过程中的细胞识别和细胞分选。此外，细胞表面钙粘蛋白的生理调节在组织形态发生和稳态中起着非常重要的作用。事实上，上皮肿瘤中E-钙粘蛋白的这些调节机制的破坏有助于恶性和转移的状态。已经提出了几种钙粘蛋白调节机制的模型，但尚不清楚它们是否发生在真实的组织或生物体中。钙粘蛋白在细胞表面起同二聚体的作用，但二聚化及其组装成更高级粘附复合物的结构基础尚不清楚。此外，分子决定因素的嗜同性粘附键和钙粘蛋白特异性的性质仍然知之甚少。连环蛋白是将钙粘蛋白连接到肌动蛋白细胞骨架并控制细胞中钙粘蛋白功能的蛋白质。然而，最近的研究结果，也牵连的胞质尾区和蛋白质p120 ctn钙粘蛋白功能的质膜结构域。拟议的研究的总体目标是了解钙粘蛋白的亲同性粘附键的分子性质，钙粘蛋白介导的粘附调节的分子机制，以及如何使用这种调节机制来控制组织形态发生。主要目标是：1.使用缺失分析、功能测定和生物物理学方法的组合，确定可溶性钙粘蛋白细胞外片段的结构特性，这些结构特性是基本的嗜同性粘附结合机制和结合特异性的基础。2.分析p120 ctn和质膜区域在爪蟾胚胎和培养细胞中钙粘蛋白介导的粘附的基本机制和生理调节中的作用，并与catenin结合结构域和catenins进行比较。3.使用激活和构象特异性单克隆抗体来研究由内而外的信号传导如何控制钙粘蛋白胞外段的嗜同性粘附特性。4.询问钙粘蛋白介导的粘附的空间和时间调节如何有助于爪蟾胚胎组织的形态发生。这些研究的结果应该有助于提高我们对钙粘蛋白在胚胎发育和器官稳态过程中组织形态发生、肿瘤进展以及与先天性疾病相关的形态发生缺陷中的功能的理解。

Cadherins are homophilic cell adhesion proteins important for the organization of cells in tissues. Cadherin adhesion specificity contributes to cell recognition and cell sorting during development. Also, physiological regulation of cadherins at the cell surface plays very important roles in tissue morphogenesis and homeostasis. Indeed, disruption of these regulatory mechanisms for E-cadherin in epithelial tumors contributes to the state of malignancy and metastasis. Several models for the mechanism of cadherin regulation have been proposed, but it is not yet known whether they occur in real tissues or organisms. Cadherins function as homodimers at the cell surface, but the structural basis of dimerization and their assembly into higher order adhesive complexes is not understood. Also, the molecular determinants of the homophilic adhesive bond and the nature of cadherin specificity are still poorly understood. The catenins are proteins that link cadherins to the actin cytoskeleton and control cadherin function in the cell. Recent findings, however, also implicate the juxtamembrane domain of the cytoplasmic tail and the protein p120ctn in cadherin function. The overall objectives of the proposed research are to understand the molecular nature of the cadherin homophilic adhesive bond, the molecular mechanisms that underlie the regulation of cadherin-mediated adhesion, and how such regulatory mechanisms are used to control tissue morphogenesis. The major aims are: 1. Determine the structural properties of the soluble cadherin extracellular segments that underlie the basic homophilic adhesive binding mechanism and binding specificity, using a combination of deletion analysis, functional assays, and biophysical methods. 2. Analyze the roles of p120ctn and the juxtamembrane region compared to the catenin-binding domain and catenins in the basic mechanism and physiological regulation of cadherin-mediated adhesion in Xenopus embryos and cultured cells. 3. Use activating and conformation specific monoclonal antibodies to investigate how inside out signaling controls the homophilic adhesion properties of the cadherin extracellular segment. 4. Ask how spatial and temporal regulation of cadherin-mediated adhesion contributes to the morphogenesis of tissues in the Xenopus embryo. The results from these studies should help improve our understanding of the functions of the cadherins in tissue morphogenesis during embryogenesis and organ homeostasis, in tumor progression, and in morphogenetic defects associated with congenital diseases.