Cellular Functions of the Tumor Suppressor APC

描述(申请人提供)：结肠癌肿瘤抑制因子腺瘤性息肉病结肠(APC)是Wnt信号转导途径的重要负调控因子，也在肌动蛋白和微管细胞骨架的调节中发挥重要作用。APC蛋白影响细胞骨架的确切机制尚未确定，可能与结肠癌的发生有关。我们利用果蝇合胞胚胎作为细胞骨架组织的模型，建立了一个研究果蝇APC2细胞骨架功能的体内系统。在这里，细胞周期中皮质肌动蛋白的动态重排是由一些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来协调的。我们以前已经证明，果蝇APC2在包括果蝇B-连环蛋白同源物、Armadillo和a-连环蛋白的复合体中的合胞细胞骨架的组织中发挥作用。我们在这个系统中对APC2的继续研究揭示了APC2在合体胚胎中组织肌动蛋白结构的功能，并且这一功能部分是通过果蝇的Forin同源结构域蛋白透明地实现的。该项目的总体目标包括确定APC2在Armadillo-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是如何利用生化分析、实时成像技术、肌动蛋白和微管的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的。这些发现不仅有助于我们对正常细胞过程的理解，也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.