Molecular Basis of Cadherin Mediated Cell Adhesion

描述(由申请人提供)：钙粘附素从相对的细胞表面结合驱动有组织的多细胞结构的发展。然而，钙粘蛋白功能的物理基础，特别是19种经典(I型和II型)钙粘蛋白的不同结合特异性，以及唯一的GPI锚定的T-钙粘蛋白与它们协同发挥作用的作用，仍然知之甚少。该建议的目的是提供经典钙粘附素功能的分子、结构和能量观点，并将分子水平的结合特异性与细胞水平的粘附性特异性联系起来。在过去的资助期间，我们在以下问题上取得了重大进展：(A)通过解决完整的I型钙粘蛋白胞外区的第一晶体结构；(B)通过解决II型钙粘蛋白的第一晶体结构；(C)通过明确确立EC1钙粘蛋白胞外区的2-链交换作为经典钙粘蛋白结合特异性的主要结构机制的作用；(D)通过开发II型钙粘蛋白功能的体内测试；(E)通过表明单氢键可以决定I型钙粘蛋白之间的结合特异性；和(F)通过求解T-钙粘蛋白的第一晶体结构，表明这种非经典的钙粘附素通过一种新的机制发挥作用。这些进展为本提案的具体目标提供了很大的基础。我们将(目标1)确定经典钙粘附素和T-钙粘附素的结合亲和力，并(目标2)利用我们对钙粘附素的结构理解来设计和表征具有改变粘附性的钙粘附素突变体。这些研究将更好地理解钙粘附素结合亲和力和细胞黏附行为之间的关系，为观察到的脊椎动物发育过程中钙粘附素表达模式的功能含义提供新的线索。由于钙粘附素参与脊椎动物几乎所有多细胞结构的发育，其功能和功能障碍对人类健康具有广泛的影响。钙粘附素的突变是许多可遗传缺陷的根本原因。钙粘附素功能的丧失，允许肿瘤细胞在体内脱附并移动，被认为是某些形式的癌症转移的先决条件。我们提出的研究将产生对钙粘附素的全面的原子水平的理解，这将对理解与钙粘附素相关的遗传疾病至关重要，并可以为开发选择性抑制单个钙粘附素的小分子药物提供基础。

DESCRIPTION (provided by applicant): The binding of cadherins from apposing cell surfaces drives the development of organized multicellular structures. However, the physical basis for cadherin function, especially the differential binding specificities of the nineteen classical (type I and type II) cadherins, and the role of the unique GPI-anchored T-cadherin that functions in concert with them, remain poorly understood. The goals of this proposal are to provide a molecular, structural, and energetic view of classical cadherin function and to relate binding specificity at the molecular level to adhesive specificity at the cellular level. In the past funding period we made significant progress on these questions (a) by solving the first crystal structure of a complete type I cadherin ectodomain; (b) by solving the first crystal structures of type II cadherins; (c) by clearly establishing the role of 2-strand swapping in the EC1 cadherin ectodomain as the primary structural mechanism underlying classical cadherin binding specificity; (d) by developing in-vivo assays for type II cadherin function; (e) by showing that a single hydrogen bond can determine binding specificity between type I cadherins; and (f) by solving the first crystal structures of T-cadherin, showing that this non-classical cadherin functions by a novel mechanism. These advances provide much of the basis for the specific aims of the current proposal. We will (Aim 1) Determine binding affinities for an all-against-all matrix of classical cadherins and T-cadherin, and (Aim 2) employ our structural understanding of cadherins to design and characterize cadherin mutants with altered adhesive specificities. These studies will provide an improved understanding of the relationship between cadherin binding affinities and the adhesive behavior of cells, shedding new light on the functional implications of cadherin expression patterns observed in vertebrate development. Because cadherins are involved in the development of virtually all multicellular structures in vertebrate animals, their function and dysfunction have broad impact on human health. Mutations in cadherins are the underlying cause of many heritable defects. Loss of cadherin function, allowing tumor cells to de- adhere and become mobile in the body, is thought to be a prerequisite for metastasis of some forms of cancer. The research we propose will produce a comprehensive atomic-level understanding of cadherins that will be critical in understanding cadherin-related genetic disorders and can provide a basis for the development of small molecule drugs selective for inhibition of individual cadherins.