BIOCHEMISTRY AND REGULATION OF CADHERIN ACTIVITY

钙粘附素是一种亲水性细胞黏附蛋白，对组织中的细胞组织很重要。在发育过程中，钙粘附素的粘附性有助于细胞识别和细胞分选。此外，细胞表面钙粘附素的生理调节在组织形态发生和动态平衡中也起着非常重要的作用。事实上，上皮性肿瘤中E-钙粘附素的这些调节机制的破坏导致了恶性肿瘤和转移的状态。已经提出了几种钙粘附素调节机制的模型，但尚不清楚它们是否存在于真实的组织或生物体中。钙粘附素在细胞表面作为同源二聚体发挥作用，但二聚化的结构基础及其组装成更高阶的粘附性复合体的结构基础尚不清楚。此外，高亲性粘附键的分子决定因素和钙粘附素特异性的本质仍然知之甚少。连环蛋白是连接钙粘蛋白和肌动蛋白细胞骨架并控制细胞内钙粘蛋白功能的蛋白质。然而，最近的发现也表明，细胞质尾部的膜旁区域和蛋白p120ctn参与了钙粘附素的功能。这项研究的总体目标是了解钙粘蛋白亲水性粘附键的分子性质，调节钙粘附素介导的粘附性的分子机制，以及如何利用这种调节机制来控制组织的形态发生。主要目的是：1.采用缺失分析、功能分析和生物物理方法相结合的方法，确定构成基本同亲结合机制和结合特异性的可溶性钙粘蛋白胞外片段的结构特性。2.分析p120ctn和膜旁区域与连接素结合区和连接素在非洲爪哇胚胎和培养细胞钙粘附素介导的黏附的基本机制和生理调节中的作用。3.使用活化的和构象特异性的单抗研究Inside Out信号如何控制钙粘蛋白胞外片段的亲和性黏附特性。4.询问钙粘附素介导的黏附的空间和时间调节如何促进非洲爪哇胚胎组织的形态发生。这些研究的结果将有助于我们更好地理解钙粘附素在胚胎发育和器官动态平衡过程中的组织形态发生、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。

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.