Cadherin-catenin Mediated Contact Inhibition of Cell Growth

描述（由申请人提供）：接触抑制限制细胞在组织中的生长，但高度受调节。它可以在快速生长的组织发育、再生和伤口愈合过程中被克服。肿瘤细胞经常失去接触抑制，使肿瘤生长远远超出其正常组织的限制。接触抑制的机制尚不清楚，但钙粘蛋白介导的细胞-细胞粘附被认为起重要作用。我们已经证明，细胞表面e -钙粘蛋白之间的亲同性黏附结合，以及与细胞质结构域结合的连环蛋白，直接介导了接触抑制生长。我们发现钙粘蛋白-连环蛋白介导的接触抑制通过两种主要途径发生；抑制生长因子受体信号，我们现在发现这是由于抑制Src家族激酶（SFKs）；我们的初步发现也暗示了Hippo信号通路，特别是Hippo通路转录介质YAP的核定位。Hippo通路最初被发现是果蝇胚胎器官大小的调节因子，最近被证明可以调节哺乳动物细胞生长、接触抑制和肿瘤发展。我们又有一个新的初步发现，生长因子信号和SFK活性影响某些细胞的YAP核定位和功能，提示Hippo通路调控的另一个重要机制。总的假设是，E-cadherin-catenin通过刺激Hippo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-cadherin-2-catenin介导的粘附、Hippo通路信号、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。具体目的是：A.阐明E-cadherin-catenin复合物之间的亲同性结合通过Hippo途径调节信号传导的机制。B.确定EGFR和SFK信号如何调控Hippo通路转录激活因子YAP的核定位和功能，了解Hippo通路介导的生长抑制在EGFR和SFK调控有丝分裂信号传导中的作用，阐明E-cadherin-catenin粘附复合物调控SFK活性的机制。C.评估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育中的作用，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。这些研究结果将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。

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.