Establishment and Maintenance of Apical-Basal Polarity

描述(申请人提供)：建立适当的细胞极性对许多组织的结构和功能至关重要，而极性的丧失是癌细胞的标志。 一些已知的极性蛋白是肿瘤抑制因子，顶端极性蛋白的下调可诱导上皮细胞向间充质细胞的转变。在上皮组织从头组装过程中，极性蛋白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。果蝇胚胎的细胞化为研究上皮细胞极性的建立提供了独特的系统。我的目标是通过定义极性蛋白质的层次结构，它们彼此之间的相互作用，以及 它们的功能。在目前的模型中，PAR-3(苍蝇中的Bazooka)是 极性层次。它的顶端定位指导着黏附连接和顶端蛋白的顶端定位.最近，Peifer实验室发现Fafadin同源物Canoe和GTPase Rap1是正确定位Bazooka顶端所必需的。他们是如何做到这一点的还不得而知。我将产生CNO突变体来定义独木舟如何将Bazooka定位到顶端区域。此外，我将在活胚胎上使用FRET来确定Rap1的活性是否在空间和时间上受到调节，我将定义哪些Rap1 GEF和下游效应器调节细胞极性。最后，我将确定在建立或维持顶端极性方面很重要的基侧蛋白。我将通过检查顶端蛋白在每一行中的运输并寻找蛋白质动力学的变化来定义它们的作用机制。组织如何极化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质，但许多蛋白质在极性启动过程中的功能还没有得到解决，而且极性蛋白质网络中的相互作用也没有很好地建立起来。定义网络并阐明极性建立和维持的机制对于了解癌细胞的正常发育很重要，而且对于了解癌细胞在上皮到间膜的转变和转移过程中极性网络在哪里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.