BIOCHEMISTRY AND REGULATION OF CADHERIN ACTIVITY

钙粘蛋白细胞粘附分子在细胞凋亡中起着重要作用。 实体组织的发育和维持。 钙粘蛋白的调节 在细胞表面的粘附活性是一个重要的机制， 控制组织形态发生。 钙粘蛋白胞质尾区， 相关的连环蛋白多肽和肌动蛋白细胞骨架是重要的 对于钙粘蛋白介导的粘附，但这些元素如何控制 细胞外嗜同性结合结构域的粘附活性不是 明白 拟议项目的总体目标是了解 它决定了钙粘蛋白细胞粘附蛋白如何组装形成 细胞表面的功能性粘附复合物以及它们的粘附 细胞表面的功能由细胞质因子调节。 的 制定了具体目标，以解决这些问题， 复杂性;首先定义基本的生物化学和同源结合 钙粘蛋白胞外结构域的性质，然后确定 寡聚化和细胞骨架锚定对钙粘蛋白的作用 粘附活性，最后分析其机制， 钙粘蛋白结合和细胞粘附的调节。 高分辨率三维结构的最新发现 N-末端钙粘蛋白胞外结构域（EC 1），表明 存在具有两个粘合界面的平行“链”二聚体， 为许多拟议的研究提供了框架。 C-钙粘蛋白 主要的粘附蛋白在非常早期的爪蟾胚胎，将是 本研究的主要主题。 我们过度表达并纯化了 毫克量的功能活性的可溶性细胞外结构域 C-cadherin。 这种蛋白质和它的突变形式将用于许多 所提出的实验。 具体目的是：1）分析 C-钙粘蛋白; 2）确定平行“链二聚体”的作用 C-受体结合特性和细胞粘附功能的相互作用 钙粘蛋白; 3）确定C- 钙粘蛋白有助于其嗜同性结合相互作用; 4）研究 细胞骨架锚定、寡聚化和连环蛋白结合的作用 控制C-钙粘蛋白在细胞表面的粘附功能; 5)研究粘合剂调节的潜在机制 C-钙粘蛋白在非洲爪蟾卵裂球和培养细胞中的功能; 6） 确定是否对E-钙粘蛋白的完整性的具体要求 非洲爪蟾外胚层的细胞外结构域是由其细胞外结构域决定的， 它的胞质尾。 从这些研究中获得的信息应该会提高我们对 钙粘蛋白在组织形态发生中的功能。 这些发现 将对理解粘合剂行为的变化产生影响 在肿瘤进展过程中， 人类先天性疾病

The cadherin cell adhesion molecules play very important roles in the development and maintenance of solid tissues. The regulation of cadherin adhesion activity at the cell surface is an important mechanism for controlling tissue morphogenesis. The cadherin cytoplasmic tail, the associated catenin polypeptides, and the actin cytoskeleton are important for cadherin-mediated adhesion, but how these elements control the adhesive activity of the extracellular homophilic binding domain is not understood. The overall goals of the proposed project are to understand the mechanisms that determine how cadherin cell adhesion proteins assemble to form a functional adhesive complex at the cell surface and how their adhesive functions at the cell surface are regulated by cytoplasmic factors. The specific aims are designed to address these issues at increasing levels of complexity; first to define the basic biochemical and homophilic-binding properties of cadherin extracellular domains, then to determine the contributions of oligomerization and cytoskeletal anchoring to cadherin adhesion activity, and finally to analyze the mechanisms underlying the regulation of cadherin binding and cell adhesion. Recent findings of the high resolution three dimensional structure of the N-terminal cadherin extracellular domain (EC1), demonstrating the existence of a parallel "strand" dimer with two adhesive interfaces, provide a framework for many of the proposed studies. C-cadherin, the major adhesion protein in the very early Xenopus embryo, will be the primary subject of this study. We have overexpressed and purified milligram amounts of a functionally active, soluble extracellular domain of C-cadherin. This protein and mutated forms of it will be used in many of the proposed experiments. The specific aims are to: 1) Analyze the homophilic binding properties of C-cadherin; 2) Determine the role of the parallel "strand dimer" interaction in the binding properties and cell adhesion functions of C- cadherin; 3) Determine which of the 5 extracellular cadherin domains of C- cadherin contribute to its homophilic binding interactions; 4) Investigate the roles of cytoskeletal anchoring, oligomerization, and catenin-binding in the control of the adhesive function of C-cadherin at the cell surface; 5) Investigate the mechanisms underlying the regulation of the adhesive function of C-cadherin in Xenopus blastomeres and cultured cells; 6) Determine whether the specific requirement for E-cadherin in the integrity of the ectoderm in Xenopus is determined by its extracellular domain or its cytoplasmic tail. The information gained from these studies should improve our understanding of the functions of the cadherins in tissue morphogenesis. The findings will have implications for understanding changes in the adhesive behavior of cells during tumor progression in morphogenetic defects associated with human congenital diseases.