Establishment and Maintenance of Apical-Basal Polarity

描述（由申请人提供）：建立适当的细胞极性对于许多组织的结构和功能至关重要，极性丧失是癌细胞的标志。 几种已知的极性蛋白是肿瘤抑制因子，并且顶端极性蛋白的下调诱导上皮细胞向间质细胞的转变。极性蛋白在上皮组织从头组装过程中最初定位的机制在很大程度上是未知的。 为了理解极性的建立和维持，我们需要了解极性蛋白质网络之间的相互作用，它们的功能以及相互作用是如何调节的。细胞化果蝇胚胎提供了一个独特的系统，在其中研究上皮细胞极性的建立。我的目标是确定极性是如何建立和维持的，通过定义极性蛋白质的层次结构，它们之间的相互作用， 它们的功能。在目前的模型中，Par-3（苍蝇中的Bazooka）是蛋白质中最上游的蛋白质。 极性等级其顶端定位指导粘附连接和顶端蛋白的顶端定位。最近，Peifer实验室发现，afadin同源物Canoe和GTADRAP 1是Bazooka正确顶端定位所必需的。他们这样做的机制是未知的。我将产生cno突变体来确定卡诺如何将巴祖卡定位到顶端结构域。此外，我将使用FRET活胚胎，以确定是否Rap 1活性的空间和时间调节，我将确定哪些Rap 1 GEFs和下游效应调节细胞极性。最后，我将确定基底外侧蛋白质是重要的建立或维持顶端极性。我将通过检查每条线中顶端蛋白的运输和寻找蛋白质动力学的改变来定义它们的作用机制。组织是如何生长的，显然比最初的假设要复杂得多。虽然已经鉴定了许多极性蛋白，但许多极性蛋白在极性起始期间的功能尚未得到解决，并且极性蛋白网络内的相互作用尚未很好地建立。定义网络和阐明极性建立和维持的机制对于理解正确的发育是重要的，而且对于理解在上皮细胞到间质细胞的转变和癌细胞转移期间极性网络在何处或如何被破坏也是重要的。

DESCRIPTION (provided by applicant): The establishment of proper cell polarity is crucial for the structure and function of many tissues, and the loss of polarity is a hallmark of cancer cells. Several known polarity proteins are tumor suppressors, and down regulation of apical polarity proteins induces epithelial-to-mesencyhmal transition. The mechanisms by which polarity proteins are initially localized during de novo assembly of epithelial tissues are largely unknown. To understand polarity establishment and maintenance, we need to understand the interactions between the network of polarity proteins, their functions, and how the interactions are regulated. The cellularizing Drosophila embryo provides a unique system in which to study the establishment of epithelial cell polarity. My goal is to determine how polarity is established and maintained, by defining the hierarchy of polarity proteins, their interactions with each other, and their functions. In the current model, Par-3 (Bazooka in flies) is the most upstream protein in the polarity hierarchy. Its apical localization directs the apical localization of adherens junction an apical proteins. Recently, the Peifer lab found that the afadin homolog Canoe and the GTPase Rap1 are required for proper apical localization of Bazooka. The mechanism by which they do this is unknown. I will generate cno mutants to define how Canoe localizes Bazooka to the apical domain. Furthermore, I will use FRET on live embryos to determine if Rap1 activity is spatially and temporally regulated, and I will define which of Rap1 GEFs and downstream effectors regulate cell polarity. Finally, I will identify basolateral proteins that are important n establishing or maintaining apical polarity. I will define their mechanism of action by examining trafficking of apical proteins in each line and looking for alterations in protein dynamics. How tissues polarize is clearly more complex than originally hypothesized. Though many polarity proteins have been identified, the functions of many during the initiation of polarity have not been addressed, and the interactions within the network of polarity proteins are not well established. Defining the network and elucidating the mechanism of polarity establishment and maintenance is important to understand proper development, but also, to understand where or how the polarity network is disrupted during epithelial-to- mesencyhmal transitions and metastasis of cancer cells.