Cadherin-catenin Mediated Contact Inhibition of Cell Growth

描述（由申请方提供）：接触抑制限制组织中的细胞生长，但高度受调控。它可以在发育、再生和伤口愈合期间在快速生长的组织中被克服。接触抑制在肿瘤细胞中经常丢失，使肿瘤生长远远超出其正常组织的限制。接触抑制的潜在机制知之甚少，但钙粘蛋白介导的细胞-细胞粘附被认为起着重要作用。我们已经表明，在细胞表面的E-钙粘蛋白蛋白之间的嗜同性粘合剂结合，与连环蛋白结合到他们的胞质结构域，直接介导接触抑制生长。我们已经发现钙粘蛋白-连环蛋白介导的接触抑制通过两个主要途径发生;生长因子受体信号传导的抑制，我们现在发现这是Src家族激酶（SFK）抑制的结果;我们的初步研究结果也涉及Hippo信号传导途径，特别是Hippo途径转录介质雅普的核定位。Hippo通路最初被发现是果蝇胚胎中器官大小的调节器，最近已被证明可调节哺乳动物细胞生长，接触抑制和肿瘤发展。我们还初步发现生长因子信号和SFK活性影响雅普在某些细胞中的核定位和功能，提示了Hippo通路调控的另一个重要机制。总体假设是E-钙粘蛋白-连环蛋白通过刺激Hippo信号传导途径和通过抑制src家族激酶（SFK）活性来调节生长的接触抑制，并且以这种方式，其用于协调或平衡生长抑制信号传导与生长因子受体的促有丝分裂信号传导。我们将首先研究E-cadherin-2-catenin介导的粘附、Hippo通路信号传导、SFK信号传导和表皮生长因子受体（EGFR）信号传导之间的功能和生理关系。我们将确定这些途径在细胞培养模型中相互调节的分子机制，然后在小鼠体内测试它们对肿瘤形成和正常组织发育的重要性。具体目标是：A.阐明E-cadherin-catenin复合物之间的同型结合通过Hippo途径调节信号传导的机制。B。确定EGFR和SFK信号如何调节Hippo通路转录激活因子雅普的核定位和功能，了解Hippo通路介导的生长抑制在EGFR和SFK调节促有丝分裂信号中的作用，阐明E-cadherin-catenin粘附复合物调节SFK活性的机制。C.评价E-cadherin-catenin介导的接触抑制和Hippo通路信号在小鼠体内乳腺和乳腺肿瘤发生中的作用，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进展。 公共卫生相关性：钙粘蛋白是一种蛋白质，它在组织中将细胞结合在一起，并与细胞内的一种称为β-连环蛋白的蛋白质一起工作。钙粘蛋白和连环蛋白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-细胞粘附和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粘附和通信功能，以实现细胞生长的接触抑制，这是一个调节正常组织发育并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.