PI Signaling Role in Epithelial/Mesenchymal Transition

描述（由申请人提供）：上皮癌进展的标志是上皮细胞向间质细胞转化（EMT）。在EMT中，细胞-细胞粘附受体E-cadherin从质膜丢失并在溶酶体中降解，其表达下调。这一事件的结果是针对？连环蛋白进入细胞核，在那里它激活刺激增殖的基因的转录。所产生的间充质细胞是迁移性的，并且具有迁移到脉管系统和淋巴中的潜力，从而引发转移。我们已经发现了一个磷酸肌醇信号通路，调节上皮细胞中E-钙粘蛋白的运输，降解和组装成粘附连接。同样的途径刺激活性？-连环蛋白转录。 磷酸肌醇信号通路产生第二信使，靶向过多的效应物。我们研究了控制大多数生物功能的PI4，5P2的时空生成。PI4，5P2由磷脂酰肌醇磷酸激酶（PIPK）合成。我们的证据支持PIPKI的关键作用？通过PIPKI？之间的一系列有序相互作用调节上皮细胞-细胞接触，E-钙粘蛋白，？-连环蛋白和贩运组分。生长因子信号传导和酪氨酸激酶Src调节这些相互作用。 假设和意义：PIPKI？控制基于钙粘蛋白的粘附连接的形成、稳定和溶解。此外，PIPKI？联系并刺激？catenin的核转位和转录活性。所有这些事件都是由PI4，5P2的产生及其对效应物的调节来调节的。这些功能的地方PIPKI？与癌症进展相关的EMT中心。这些功能受到一系列翻译后事件的调节，这些事件驱动正常上皮形态发生或EMT，导致迁移和侵袭增加。以下重点目标将评估这一假设 (1)我们将研究PIPKI的作用？在钙粘蛋白的内吞作用中。重点关注PIPKI？调节的基础和生长因子刺激的E-钙粘蛋白内吞作用。翻译后修饰的E-cadherin和PIPKI的作用？将被定义。 (2)描述PIPKI的作用？EGFR和E-钙粘蛋白的溶酶体破坏中的亚型。新发现的PIPKI？剪接同种型将E-钙粘蛋白分类用于在溶酶体中降解。所涉及的机制和因素将被定义为控制EMT的信号通路的重点。 (3)PIPKI？监管？将揭示连环蛋白转录活性。激活？- PIPKI的catenin？会被整合到已知的激活途径中连环蛋白的作用 上皮来源的癌症占所有人类癌症的至少80%，并且通常是最难治愈的。上皮癌危及生命的方面是转移，这一过程取决于上皮细胞组织的丧失，这一过程由E-钙粘蛋白受体控制。E-钙粘蛋白将上皮细胞保持在一起并抑制生长和转移。当E-钙粘蛋白丢失时，上皮癌可以自由转移或迁移到不同的器官。我们已经发现了一种信号通路，它既调节E-钙粘蛋白将细胞结合在一起的能力，也调节上皮癌中E-钙粘蛋白的丢失。

DESCRIPTION (provided by applicant): A hallmark of epithelial cancer progression is the epithelia to mesenchymal transition (EMT). In EMT the cell-cell adhesion receptor E-cadherin is lost from the plasma membrane and degraded in the lysosome and its expression is down regulated. This event results in the targeting of ?-catenin to the nucleus where it activates the transcription of genes that stimulate proliferation. The resulting mesenchymal cells are migratory and have the potential to migrate into the vasculature and lymph, initiating metastasis. We have discovered a phosphoinositide signaling pathway that regulates E-cadherin trafficking, degradation and assembly into adherens junctions in epithelial cells. The same pathway stimulates the activity of ?-catenin transcription. Phosphoinositide signaling pathways generate second messengers that target a plethora of effectors. We study the spatial and temporal generation of PI4,5P2 that controls most biological function. PI4,5P2 is synthesized by the phosphatidylinositol phosphate kinases (PIPK). Our evidence supports a key role for the PIPKI? in regulation of epithelial cell-cell contacts by an ordered set of interactions between PIPKI?, E- cadherin, ?-catenin, and trafficking components. Growth factor signaling and the tyrosine kinase Src regulate these interactions. Hypothesis and significance: PIPKI? controls the formation, stabilization and dissolution of cadherin based adherens junctions. In addition, PIPKI? associates with and stimulates ?-catenin's translocation to the nucleus and transcriptional activity. All of these events are regulated by the generation of PI4,5P2 and its regulation of effectors. These functions place PIPKI? at the center of EMT associated with cancer progression. These functions are regulated by a set of posttranslational events that drive either normal epithelial morphogenesis, or EMT, that results in increased migration and invasion. The following focused aims will assess this hypothesis (1) We will investigate the role of PIPKI? in the endocytosis of cadherins. The focus will be on the basal and growth factor stimulated E-cadherin endocytosis regulated by PIPKI?. The role of posttranslation modifications of E-cadherin and PIPKI? will be defined. (2) Delineate the role of PIPKI? isoforms in the lysosomal destruction of EGFR and E-cadherin. A newly discovered PIPKI? splice isoform sorts E-cadherin for degradation in the lysosome. The mechanism and factors involved will be defined with an emphasis on signaling pathways that control EMT. (3) PIPKI? regulation of ?-catenin transcriptional activity will be revealed. The activation of ?-catenin by PIPKI? will be integrated into pathways that are known to activate ?-catenin upon EMT. PUBLIC HEALTH RELEVANCE: Cancers of epithelial origin represent at least 80% of all human cancers and are often the most difficult to cure. The life threatening aspect of epithelial cancer is metastasis and this process is dependent upon the loss of epithelial cell organization a process that is controlled by the E-cadherin receptor. E-cadherin holds epithelial cells together and suppresses growth and metastasis. When E-cadherin is lost epithelial cancers are free to metastasize or migrate to different organs. We have discovered a signaling pathway that regulates both E-cadherin's ability to hold cells together and also the loss of E-cadherin from epithelial cancers.