Organization and function of the interface between cadherin and the cytoskeleton

钙粘附素是一种多功能的黏附受体，参与动物发育和组织动态平衡。我们特别感兴趣的是钙粘附素在上皮细胞中所起的作用，上皮细胞是动物中发现的主要组织类型。钙粘附素在显著的接触点将细胞连接在一起，称为粘连连接。当钙粘附素功能不正常时，上皮细胞崩溃或形成异常形状，这对动物通常是致命的。钙粘附素只有在与细胞的细胞骨架相连时才能发挥作用。这种连接对于形成和保持附着连接是至关重要的。此外，黏附连接和细胞骨架必须合作来塑造和维持组织。钙粘附素与多种细胞质因子结合，包括α-连环蛋白，这是我们近年来研究的一种蛋白质，它是钙粘蛋白与细胞骨架之间的主要连接物。α-连环蛋白的丢失与钙粘蛋白的丢失会导致相同的缺陷，这一事实突显了钙粘蛋白与细胞角蛋白之间的联系的重要性。然而，钙粘蛋白/α-连环蛋白与肌动蛋白之间的界面非常复杂，因为不仅α-连环蛋白可以与细胞骨架的肌动蛋白细丝结合，而且还有几个结合伙伴可以与肌动蛋白结合。关于这个界面如何调节上皮细胞的发育和稳定性，还有很多需要了解。*我们最近发现了一种新的α-连环蛋白结合伙伴，称为GYDIN，它定位于果蝇(我们研究的实验模型)和哺乳动物细胞中的黏附连接，如一位合作者所展示的那样。Girdin可以直接与肌动蛋白结合。当Girdin丢失时，粘连连接处的肌动蛋白组织被破坏，上皮细胞出现异常形状。我们提出的工作的第一个目标是详细了解吉尔丁是如何与α-连环蛋白相互作用的，以及吉尔丁对黏附连接的功能和上皮细胞中肌动蛋白细胞骨架的组织有什么具体贡献。*在第二个目标中，我们将探索黏附连接和细胞骨架的第二个主要组成部分--微管之间的相互作用。微管的末端与黏附连接相连，这种联系被认为对黏附连接的形成和稳定性很重要，但对微管如何与黏附连接相互作用以及为什么这对正常的上皮发育很重要的详细了解是突出的。为了获得切入点并开发工具来研究这种联系，我们将探索一种名为PLEKHA7的因子在哺乳动物中的功能，以及CG34383在果蝇中的功能。在哺乳动物细胞培养中的研究表明，PLEKHA7将微管的末端连接到钙粘附素，而破坏这种连接会破坏粘连连接。对果蝇中CG34383的分析将给我们一个前所未有的机会来研究这种蛋白如何在整个动物的背景下对上皮发育做出贡献。**

Cadherins are multifunctional adhesion receptors involved in animal development and tissue homeostasis. We are particularly interested in the role cadherins play in epithelia, the major tissue type found in animals. Cadherins link cells together at prominent contact points called adherens junctions. When cadherins do not function normally, epithelia collapse or develop abnormal shapes, which is often lethal to the animal. Cadherins can only function when they are linked to the cytoskeleton of a cell. This linkage is crucial to form and maintain adherens junctions. Moreover, adherens junctions and the cytoskeleton have to cooperate to shape and maintain tissues. Cadherins bind to several cytoplasmic factors including α-Catenin, a protein that we have studied in recent years, and that is the major linker between cadherin and the cytoskeleton. The importance of the linkage between cadherin and the cytoskelton is highlighted by the fact that loss of α-Catenin causes the same defects as loss of cadherin. However, the interface between cadherin/α-Catenin and actin is very complex as not only α-Catenin can bind to the actin filaments of the cytoskeleton, but has also several binding partners that can bind to actin. Much remains to be learned about how this interface operates to regulate epithelial development and stability. ******We have recently identified a new α-Catenin binding partner called Girdin that localizes to adherens junctions in the fruit fly Drosophila, the experimental model that we study, and in mammalian cells as was shown by a collaborator. Girdin can directly bind to actin. When Girdin is lost, actin organization is disrupted at adherens junctions and epithelia adopt abnormal shapes. The first aim of our proposed work is to develop a detailed understanding of how Girdin interacts with α-Catenin and what specific contributions Girdin makes to the function of adherens junctions and the organization of the actin cytoskeleton in epithelial cells. ******In a second aim we will explore the interactions between adherens junctions and the second major component of the cytoskeleton, microtubules. The ends of microtubules are linked to adherens junctions, an association presumed to be important for adherens junction formation and stability, but a detailed understanding of exactly how microtubules interact with adherens junctions and why this is important for normal epithelial development is outstanding. In order to gain an entry point and develop tools to study this association we will explore the function of a factor called PLEKHA7 in mammals and CG34383 in Drosophila. Work in mammalian cell culture suggests that PLEKHA7 links the ends of microtubules to cadherin and that compromising this link disrupts adherens junctions. An analysis of CG34383 in Drosophila will give us the unprecedented opportunity to investigate how this protein contributes to epithelial development in the context of a whole animal. **