A model system to study the tumor suppressor APC

描述(申请人提供)：上皮组织在许多癌症中受到影响。癌症是由正常细胞行为的改变引起的，通常是由于细胞间通讯的改变。细胞-细胞信号及其信号转导通路在正常胚胎发育和成体生理中起着基础性作用，影响着基因表达和细胞骨架等多个过程。为了了解疾病的过程，我们必须首先了解受影响的蛋白质的正常作用。我们关注的是肿瘤抑制因子APC。APC基因突变发生在70%的结肠癌中。在了解APC功能方面的一个关键突破来自于它与蛋白B-连环蛋白结合的发现。B-连环蛋白及其果蝇同源Armadillo(ARM)是Wnt信号转导途径中的关键效应者。这使得研究APC的科学家可以利用在模型生物中研究Wnt信号所获得的知识，并迅速产生一个模型，表明APC通过堆积靶向双连环蛋白/臂进行磷酸化和最终的蛋白水解性破坏来负调控Wnt信号。我们建立了一个模型系统来探索PAC的功能。我们利用果蝇，将经典遗传学和分子遗传学与细胞生物学和生物化学相结合，从而利用这个模型系统的速度及其与脊椎动物细胞生物学的协同作用。我们发现，果蝇APC2是胚胎表皮中Wnt信号的负调控因子。我们还发现，在有丝分裂过程中，APC2在调节肌动蛋白和微管细胞骨架之间的联系方面发挥了意想不到的作用。我们假设APC家族蛋白是连接信号转导和细胞骨架的几种不同蛋白质复合体的多功能成分。我们将验证这一假设，探索Fly APC2作为人类APC模型的功能。我们的具体目标是：1.确定APC2的缺失表型并评估APC与APC2之间的冗余性；2.确定单个蛋白结构域对APC功能的贡献，并利用这些信息测试APC2在破坏复合体中的功能模型；3.确定APC2的S在细胞骨架调控中的作用；4.使用遗传学和生化方法来确定APC2的新伙伴。

DESCRIPTION (provided by applicant): Epithelial tissues are affected in many cancers. Cancer results from alterations in normal cell behavior, often due to changes in cell-cell communication. Cell-cell signals and their signal transduction pathways play fundamental roles in normal embryonic development and adult physiology, influencing many processes including gene expression and the cytoskeleton. To understand the disease process, we must first understand the normal role of the proteins affected. We focus on the tumor suppressor APC. Mutations in APC occur in >70% of all colon cancers. A key breakthrough in understanding APC function came from the discovery that it binds to the protein B-catenin. B-catenin and its Drosophila homolog Armadillo (Arm) are key effectors in the Wnt signal transduction pathway. This allowed scientists studying APC to take advantage of the knowledge gained from studying Wnt signaling in model organisms, and rapidly led to a model suggesting that APC negatively regulates Wnt signaling by heaping target Bi-catenin/Arm for phosphorylation and ultimate proteolytic destruction. We established a model system to explore Pac's functions. We utilize the fruit fly Drosophila, combining classical and molecular genetics with cell biology and biochemistry, and thus capitalizing on the speed of this model system and its synergy with vertebrate cell biology. We found that Drosophila APC2 is a negative regulator of Wnt signaling in the embryonic epidermis. We also found an unexpected role for APC2 in regulating the link between the actin and microtubule cytoskeletons during mitosis. We hypothesize that APC family proteins are multi-functional components of several different protein complexes that link signal transduction and the cytoskeleton. We will test this hypothesis, exploring the functions of fly APC2 as a model for human APC. Our specific aims are to: 1. Define the null phenotype of APC2 and assess redundancy between APC and APC2, 2. Define the contribution of individual protein domains to APC function, and use this information to test models for APC2 function in the destruction complex, 3. Determine APC2's role in cytoskeletal regulation, and 4. Use genetic and biochemical approaches to define new partners for APC2.