Cellular Functions of the Tumor Suppressor APC

描述（由申请人提供）：结肠癌肿瘤抑制因子Adenomatous polyposis coli （APC）是Wnt信号转导通路的重要负调节因子，在肌动蛋白和微管细胞骨架的调节中也起着重要作用。APC蛋白影响细胞骨架的确切机制尚未确定，可能有助于结肠癌的发展。我们开发了一个体内系统，利用果蝇合胞胚胎作为细胞骨架组织的模型来研究果蝇APC2的细胞骨架功能。在细胞周期中，皮质肌动蛋白的动态重排是由许多已知的肌动蛋白调节蛋白以及与中心体和微管的相互作用精心安排的。我们之前已经证明果蝇APC2在包括果蝇B-catenin同源物、Armadillo和a-catenin在内的合体细胞骨架的组织中起作用。我们对该系统中APC2的进一步研究表明，APC2在合胞胚胎中具有组织肌动蛋白结构的功能，并且该功能部分与果蝇formin同源结构域蛋白Diaphanous一起完成。该项目的总体目标包括定义APC2在armadilla -a-catenin复合体和透明复合体中的分子相互作用，并详细了解这些复合体如何使用生化分析、实时成像技术、肌动蛋白和微管组织和行为分析以及识别其他蛋白质伙伴和调节因子来组织肌动蛋白细胞骨架。这些发现不仅有助于我们对正常细胞过程的理解，而且有助于我们对细胞功能障碍和癌症的理解。

DESCRIPTION (provided by applicant): The colon cancer tumor suppressor Adenomatous polyposis coli (APC) acts as an essential negative regulator of the Wnt signal transduction pathway and also has fundamental roles in the regulation of the actin and microtubule cytoskeletons. The precise mechanisms by which APC proteins influence the cytoskeleton have not been defined and may contribute to the development of colon cancer. We have developed an in vivo system in which to study the cytoskeletal functions of Drosophila APC2 using the Drosophila syncytial embryo as a model for cytoskeletal organization. Here, dynamic rearrangements of cortical actin during the cell cycle are orchestrated by a number of known actin regulatory proteins and by interactions with centrosomes and microtubules. We have previously shown that Drosophila APC2 plays a role in organization of the syncytial cytoskeleton in a complex including the Drosophila B-catenin homolog, Armadillo, and a-catenin. Our continued study of APC2 in this system revealed that APC2 functions to organize actin structures in the syncytial embryo and that this function is carried out in part with a Drosophila formin homology domain protein Diaphanous. The overall goals of this project include defining the molecular interactions of APC2 within the Armadillo-a-catenin complex and the Diaphanous complex and to understand in detail how these complexes are functioning to organize the actin cytoskeleton using biochemical assays, live imaging techniques, analysis of actin and microtubule organization and behavior, and identification of other proteins partners and regulators. These findings will contribute not only to our appreciation of normal cell processes, but also to our understanding of cellular dysfunction and cancer.