Functional and Structural Links between Cadherin, Gamma-Secretase, and Notch

描述（由申请人提供）：钙粘蛋白介导的粘附和Notch信号通路是多细胞生物进化开始时发展的两个关键过程。第一个过程将大量细胞排列成高度组织化的组织。第二个决定了单个细胞的分化程序。虽然一些间接证据表明这两个过程有交叉，但它们相互依赖的程度和机制在很大程度上尚不清楚。我们的初步实验确定了钙粘蛋白介导的粘附和Notch信号传导之间的两个潜在的关键联系。其中一个链接是包含 E-钙粘蛋白和 γ-分泌酶的复合物，γ-分泌酶是产生 Notch 衍生信号的酶。这些蛋白质通过 p120-连环蛋白相互连接，p120-连环蛋白是基于钙粘蛋白的粘附的关键调节因子。在第二个复合物中，E-钙粘蛋白与 Notch 配体（Dll1 或 Jag2）相互作用。该提案解决了四个问题：（i）这两个复合物的详细结构是什么以及它们是如何组装的？ (ii) 钙粘蛋白在细胞表面动力学，特别是内吞作用中的作用是什么？ (iii) 它们在 Notch 信号传导中发挥什么作用？ (iv) 它们在角质形成细胞分化中的作用是什么？我们提出钙粘蛋白通过在细胞-细胞连接处和/或内吞结构内共聚集Notch信号成分来促进Notch信号转导。此外，钙粘蛋白驱动的这些簇的内吞作用可能会产生Notch构象的转变，从而启动Notch信号级联。该提议将揭示在正常稳态和炎症性皮肤病期间角质形成细胞的形态发生、增殖和分化程序的协调机制。

DESCRIPTION (provided by applicant): Cadherin-mediated adhesion and the Notch signaling pathway are two critical processes developed at the start of the evolution of multicellular organisms. The first process arranges numerous cells into highly organized tissues. The second determines the differentiation program of individual cells. While some circumstantial evidence suggests that the two processes intersect, the levels and mechanisms of their interdependency are largely unknown. Our preliminary experiments identified two potentially crucial links between cadherin- mediated adhesion and Notch signaling. One of these links is a complex containing E-cadherin and gamma- secretase, the enzyme that generates a Notch-derived signal. The proteins are interconnected via p120- catenin, a critical regulator of cadherin-based adhesion. In a second complex, E-cadherin interacts with Notch ligands, either Dll1 or Jag2. This proposal addresses four questions: (i) What are the detailed structures of both complexes and how are they assembled? (ii) What is the role of cadherin in their cell surface dynamics, and in their endocytosis in particular? (iii) What are their roles in Notch signaling? (iv) What are their roles in keratinocyte differentiation? We propose that cadherin facilitates Notch signal transduction by co-clustering Notch signaling components within cell-cell junctions and/or within the endocytic structures. Furthermore, cadherin-driven endocytosis of these clusters may generate the shift in Notch conformation, thereby initiating a Notch signaling cascade. This proposal will shed light on mechanisms coordinating morphogenetic, proliferation and differentiation programs of keratinocytes during normal homeostasis and inflammatory skin diseases.