Cadherin-catenin Mediated Contact Inhibition of Cell Growth

描述(申请人提供)：接触抑制限制细胞在组织中的生长，但高度受制于调节。在发育、再生和伤口愈合过程中，可以在快速生长的组织中克服它。接触抑制经常在肿瘤细胞中消失，使肿瘤生长远远超出正常组织的限制。人们对接触抑制的机制知之甚少，但钙粘附素介导的细胞-细胞黏附被认为发挥了重要作用。我们已经证明，细胞表面E-钙粘附素蛋白之间的亲和性粘连结合，与其细胞质结构域结合的连环蛋白，直接介导接触性生长抑制。我们发现钙粘附素-连接素介导的接触抑制通过两条主要途径发生：生长因子受体信号的抑制，这是我们现在发现的抑制Src家族激酶(SFK)的结果；我们的初步发现还涉及河马信号途径，特别是河马途径转录调节因子YAP的核定位。河马途径最初是作为果蝇胚胎器官大小的调节器被发现的，最近被证明调节哺乳动物细胞的生长、接触抑制和肿瘤的发展。我们又有了一个新的初步发现，生长因子信号和SFK活性影响了YAP在某些细胞中的核定位和功能，提示了河马通路调节的另一个重要机制。总的假设是E-钙粘素-连环蛋白通过刺激河马信号通路和抑制src家族激酶(SFK)活性来调节接触性生长抑制，从而协调或平衡生长抑制信号和生长因子受体的有丝分裂信号。我们将首先研究E-钙粘蛋白-2-连环蛋白介导的黏附、Hippo途径信号、SFK信号和表皮生长因子受体(EGFR)信号之间的功能和生理关系。我们将在细胞培养模型中确定这些通路相互调节的分子机制，然后在体内测试它们对小鼠肿瘤形成和正常组织发育的重要性。其具体目的是：1.阐明E-钙粘附素-连环蛋白复合体之间的同亲结合调节河马信号通路的机制(S)。B.确定EGFR和SFK信号如何调节河马途径转录激活子YAP的核定位和功能，了解河马途径介导的生长抑制在EGFR和SFK调节有丝分裂信号中的作用，并阐明E-钙粘附素-连环蛋白黏附复合体调节SFK活性的机制(S)。C.评估E-钙粘素-连环蛋白介导的接触抑制和河马信号通路在小鼠乳腺和乳腺肿瘤体内发展中的作用，以及它们在受体酪氨酸激酶(RTK)和SFK信号通路驱动的肿瘤发生中的作用。这些研究的结果应该揭示接触抑制如何调节正常组织的发育，以及接触抑制的丧失如何导致肿瘤的形成和发展。 与公共健康相关：钙粘附素是一种在组织中将细胞结合在一起的蛋白质，并与细胞内一种名为β-连环蛋白的蛋白质协同工作。钙粘附素和连接素通过两种方式在组织发育和癌症中发挥重要作用：通过控制物理细胞与细胞之间的黏附，以及通过调节细胞内的细胞通讯过程。该项目中的研究将分析这两种蛋白质如何执行其黏附和通信功能，以实现对细胞生长的接触抑制，这是一个调节正常组织发育和抑制癌症生长的过程。

DESCRIPTION (provided by applicant): Contact inhibition limits cell growth in tissues, but is highly subject to regulation. It can be overcome in rapidly growing tissues during development, regeneration, and wound healing. Contact inhibition is frequently lost in tumor cells, allowing tumors to grow well beyond their normal tissue constraints. The mechanisms underlying contact inhibition are poorly understood, but cadherin-mediated cell-cell adhesion is thought to play an important role. We have shown that homophilic adhesive binding between E-cadherin proteins at the cell surface, in association with catenins bound to their cytoplasmic domains, directly mediate contact inhibition of growth. We've found that cadherin-catenin mediated contact inhibition occurs via two major pathways; inhibition of growth factor receptor signaling, which we now find results from inhibition of Src family kinases (SFKs); and our preliminary findings also implicate the Hippo signaling pathway, in particular the nuclear localization of the Hippo pathway transcriptional mediator YAP. The Hippo pathway was originally discovered as a regulator of organ size in Drosophila embryos, and recently has been shown to regulate mammalian cell growth, contact inhibition, and tumor development. We have made another novel preliminary finding that growth factor signaling and SFK activity affect YAP nuclear localization and function in some cells, suggesting another important mechanism of Hippo pathway regulation. The overall hypothesis is that E-cadherin-catenin regulates contact inhibition of growth both by stimulating the Hippo signaling pathway and by inhibiting src family kinase (SFK) activity, and in this way it serves to coordinate or balance growth inhibitory signaling with the mitogenic signaling by growth factor receptors. We will first investigate the functional and physiological relationships between E-cadherin-2-catenin mediate adhesion, Hippo pathway signaling, SFK signaling, and Epidermal Growth Factor Receptor (EGFR) signaling. We will determine the molecular mechanisms by which these pathways regulate each other in cell culture models and then test their importance in vivo for tumor formation and normal tissue development in mice. The specific aims are: A. Elucidate the mechanism(s) by which homophilic binding between E-cadherin-catenin complexes regulates signaling through the Hippo pathway. B. Determine how EGFR and SFK signaling regulate the nuclear localization and function of the Hippo pathway transcriptional activator YAP, understand the role of Hippo pathway-mediated growth inhibition in the regulation of mitogenic signaling by EGFR and SFKs, and elucidate the mechanism(s) of regulation SFK activity by E-cadherin-catenin adhesive complexes. C. Evaluate the roles of E-cadherin-catenin-mediated contact inhibition and Hippo pathway signaling in the development of mammary glands and mammary tumors in vivo in mice, and their roles in tumorigenesis driven by Receptor Tyrosine Kinase (RTK) and SFK signaling pathways. Findings from these studies should reveal how contact inhibition regulates normal tissue development and how the loss of contact inhibition leads to the formation and progression of tumors. PUBLIC HEALTH RELEVANCE: Cadherins are proteins that hold cells together in tissues and work in association with a protein inside the cell called beta-catenin. Cadherins and catenins play important roles in tissue development and cancer in two ways; by controlling physical cell-cell adhesion and by regulating cellular communication processes inside the cell. The studies in the project will analyze how these two proteins carry out their adhesion and communication functions to bring about contact inhibition of cell growth, a process that regulates normal tissue development and inhibits cancer growth.