Signal integration and modulation by the Axin complex during Wnt/b-catenin signaling

在整个发育过程和成年时期，细胞接收到特定的信号，它们必须根据信号的强度精确地解释这些信号。Wnt家族的分泌蛋白就是这样一个信号。wnt通过增加转录因子-连环蛋白水平介导基因表达的精确变化。这个信号过多或过少都会导致图案缺陷和/或疾病。wnt通过阻断中枢通路调节剂（一种组装在支架蛋白轴蛋白周围的蛋白质复合物）的功能来诱导β -连环蛋白信号。多个可能相互冲突的输入在轴蛋白复合体内相互作用。在Wnt信号转导过程中，这些不同的输入是如何整合和动态控制的尚不清楚。本项目的重点是通过确定信号转导过程中轴蛋白复合物及其亚复合物的位置，建立Wnt/B-catenin信号转导的动态模型。然后将使用基因操作来确定这些发现的功能意义。目前Wnt/B-catenin通路的模型主要基于组织培养中的过表达和体外蛋白-蛋白相互作用的研究。这些发现对体内正常信号传导的功能意义尚不清楚。值得注意的是，在拟议的研究中，Wnt/B-catenin通路将在模式生物果蝇中进行分析，允许在正常细胞环境和生理条件下进行分析。此外，Axin蛋白复合物的实时可视化将建立Wnt信号的动态图像，这是以往研究中没有实现的。这些研究有望确定新的调控相互作用，并可能打开Wnt途径的药理干预。该项目将为一名研究生和两名本科生提供从事前沿研究的机会。此外，它将允许PI向K-12学生介绍基本发展和遗传学，并在当地学校推广以科学为基础的课程。

Throughout development and in the adult, cells receive specific signals that they must interpret precisely according to the signal's strength. Secreted proteins of the Wnt family represent one such signal. Wnts elicit precise changes in gene expression mediated by increased levels of the transcription factor Beta-catenin. Too much, or too little, of this signal leads to patterning defects and/or disease. Wnts induce a Beta-catenin signal by blocking the function of the central pathway regulator, a protein complex assembled around the scaffold protein Axin. Multiple, potentially conflicting, inputs interact within the Axin complex. How these different inputs are integrated and dynamically controlled during Wnt signal transduction remains unclear. The focus of this project is to establish a dynamic model of Wnt/B-catenin signaling by identifying the location of the Axin complex and its sub-complexes during signal transduction. Genetic manipulations will then be used to determine the functional significance of the findings.The current model of the Wnt/B-catenin pathway is based largely on studies using overexpression in tissue culture, and protein-protein interactions in vitro. The functional significance of these findings for normal signaling in vivo remains unclear. Significantly, in the proposed studies, the Wnt/B-catenin pathway will be analyzed in the model organism Drosophila, allowing its analysis in the normal cellular context and under physiological conditions. Additionally, visualization of the Axin protein complexes in real-time will establish a dynamic picture of Wnt signaling not achieved in previous studies. These studies are expected to identify novel regulatory interactions and may open the Wnt pathway to pharmacological intervention. This project will provide an opportunity for one graduate student, and two undergraduate students to engage in cutting edge research. In addition, it will allow the PI to introduce K-12 students to basic development and genetics and to promote a science-based curriculum in local schools.