EPITHELIAL MORPHOGENESIS IN DEVELOPMENT AND DISEASE

描述(申请人提供)：上皮由两极分化的细胞组成，其主要功能是建立一种屏障，保护身体免受环境的影响。上皮细胞具有很高的更新和损伤修复能力来维持这一屏障。不幸的是，上皮细胞也是与癌症有关的最常见的细胞类型。以钙粘附素为基础的黏附连接(AJ)介导了最初的上皮细胞与细胞间的黏附，使细胞聚集成极化的多细胞组织。然而，一旦形成AJ，就不是一成不变的。虽然对新生AJ的形成有很多了解，但AJ在已形成的上皮细胞中的维持和重塑通常是一个不太清楚的过程。Rho GTP酶是上皮细胞黏附、细胞形态和极化的重要调节因子。Rho GTP酶激活不同效应器以响应细胞黏附的能力被认为是它们功能多样性的原因，然而某些效应器是否可以被分配到特定的角色以及这些角色是什么，特别是在体内，尚不确定。哺乳动物中存在多个Rho GTP酶家族成员和效应器，这使得它们在体内的功能测定变得复杂。相比之下，果蝇只有一个Rho和CDC42成员，而且大多数效应器蛋白都有一个或几个成员，这使得分析更直接。在过去的三年里，我们一直在研究Rho GTP酶在果蝇上皮重塑和形态发生中的作用。我们的累积结果表明，在重塑的上皮细胞中，Rho1和Cdc42相互影响对方调节AJ重塑和细胞张力的活性，而在增殖的上皮细胞中，Cdc42极性复合体通过调节Rho1的活性来调节细胞凋亡诱导的代偿性增殖。现在，我们将确定调停Rho1和CDC42串扰的候选对象，并确定他们如何进行调解。我们将在果蝇或哺乳动物细胞系中使用果蝇遗传学和分子和细胞生物学方法。除了表面钙粘附素，胞浆蛋白也被招募来形成AJ。这些蛋白质将钙粘附素与调节细胞骨架或细胞存活/增殖的活动偶联。含有LIM结构域的Ajuba家族的接头或支架蛋白就是这样的蛋白质。与Rho GTP酶一样，在过去的3年里，由于重叠的组织表达和家族成员的功能冗余，我们在体内确定它们在哺乳动物上皮形态发生中的作用的努力一直是具有挑战性的。果蝇只有一个基因，djub。我们已经证明，djub是河马信号通路的一个组成部分，是一个必需的基因和一个新的上皮器官大小调节因子。我们现在将确定Ajuba Lim蛋白如何调节哺乳动物和果蝇中的河马信号通路，以影响上皮组织的生长。 与公共卫生相关：上皮细胞形成贴壁的细胞片(上皮)，其主要功能是建立一种屏障，保护身体免受环境的影响。上皮细胞具有很高的更新和损伤修复能力来维持这一屏障。不幸的是，上皮细胞也是与癌症有关的最常见的细胞类型。确切地说，上皮细胞如何聚集在一起形成上皮膜，以及这些动态结构如何不断重塑以保持其屏障功能，是成人发育和疾病(癌症、细菌感染、慢性炎症性疾病)的一个突出问题。我们已经用果蝇作为一个模型系统来确定上皮细胞的形成和重塑是如何调节的。我们发现，一系列分子信号开关，Rho GTP酶，在重塑上皮细胞和细胞形状方面具有独特和独特的功能。此外，我们还发现，一系列稳定上皮细胞黏附的蛋白质也调节上皮器官的生长或大小。这项建议是为了确定各种Rho GTP酶如何调节上皮细胞重构，特别是在体内，以及最终的上皮器官大小是如何确定的。

DESCRIPTION (provided by applicant): Epithelia are composed of polarized sheets of cells whose main function is to establish a barrier that protects the body from its environment. Epithelia have a high capacity for renewal and injury repair to maintain this barrier. Unfortunately, epithelial cells are also the most common cell type implicated in cancer. Cadherin-based adherens junctions (AJ) mediate initial epithelial cell-cell adhesion allowing cells to assemble into polarized multicellular tissues. Once formed AJ are not static, however. While much is known about nascent AJ formation the maintenance and remodeling of AJ in a formed epithelia is, in general, a less well-understood process. Rho GTPases are critical regulators of epithelial adhesion, cell shape, and polarization. The ability of Rho GTPases to activate different effectors, in response to cell adhesion, is believed to be responsible for their functional diversity, yet whether certain effectors can be assigned to specific roles and what those roles are, especially in vivo, are uncertain. The presence of multiple Rho GTPase family members and effectors in mammals complicates determination of their function in vivo. In contrast Drosophila have only one Rho and Cdc42 member and most effector proteins have one or few members, allowing for a more straightforward analysis. Over the past 3 years we have been studying the role of Rho GTPases in epithelial remodeling and morphogenesis in Drosophila. Our accumulated results indicate that in remodeling epithelia Rho1 and Cdc42 influence each other's activity to regulate AJ remodeling and cell tension, whereas in a proliferating epithelium the Cdc42 polarity complex regulates apoptosis induced compensatory proliferation by modulating Rho1 activity. We will now identify candidates mediating Rho1 and Cdc42 crosstalk and determine how they do so. We shall use both drosophila genetics and molecular and cellular biological approaches in drosophila or mammalian cell lines. In addition to surface cadherins, cytosolic proteins are recruited to forming AJ. These proteins couple cadherin adhesion to activities that modulate the cytoskeleton or cell survival/proliferation. The Ajuba family of LIM domain containing adapter or scaffolding proteins are such proteins. As with Rho GTPases, our efforts, over the past 3 years, determining their role in mammalian epithelial morphogenesis, in vivo, has been challenging due to overlapping tissue expression and functional redundancy of family members. Drosophila has a single gene, djub. We have shown that djub is an essential gene and a novel regulator of epithelial organ size as a component of the Hippo signaling pathway. We will now determine how Ajuba LIM proteins regulate the Hippo signaling pathway in mammals and drosophila, to influence epithelial tissue growth. PUBLIC HEALTH RELEVANCE: Epithelial cells form adherent sheets (Epithelia) of cells whose main function is to establish a barrier that protects the body from its environment. Epithelia have a high capacity for renewal and injury repair to maintain this barrier. Unfortunately, epithelial cells are also the most common cell type implicated in cancer. Precisely how epithelial cells come together to form epithelial sheets and how these dynamic structures constantly remodel so as to maintain their barrier function is an outstanding question in development and diseases of adults (cancer, bacterial infection, chronic inflammatory disease). We have used Drosophila as a model system to determine how epithelia formation and remodeling is regulated. We have found that a family of molecular signal switches, Rho GTPases, serves unique and distinct functions in remodeling epithelia and cell shape. Furthermore, we have found that a family of proteins that stabilizes epithelial cell adhesion also regulates epithelial organ growth or size. This proposal is to determine how the various Rho GTPases regulate epithelia remodeling, particularly in vivo and how ultimate epithelial organ size is determined.