A model system to study the tumor suppressor APC

几个关键的信号转导通路在动物发育中起着关键作用，也是 在癌症中被不适当地激活。其中包括Wnt途径。它在人类癌症中的作用是 首次通过肿瘤抑制因子腺瘤性息肉病(APC)发现，在大多数 结肠癌。我们现在知道，APC是Wnt信号的关键负性调节因子。APC是一部分 针对关键的Wnt效应蛋白连环蛋白的多蛋白“破坏复合体”的研究 以及最终蛋白酶体的破坏。了解APC功能对以下两个方面都至关重要 了解Wnt信号如何影响正常发育以及它的不适当激活 会导致癌症。APC除了在Wnt调节中发挥作用外，还在细胞骨架中发挥作用 监管。不同的细胞骨架功能被归因于APC。其中一项建议是 通过对染色体分离的影响，在APC突变肿瘤的染色体不稳定性中的作用。 我们建立了一个模型系统来研究APC在Wnt信号和细胞骨架调节中的功能 在正常发育过程中，并模拟其失活如何导致癌症。我们用果蝇 果蝇，利用遗传、细胞生物学和生化工具的强大组合 在苍蝇中可用。哺乳动物和果蝇都有两个APC家族成员，它们都有一个共同的 蛋白质结构域的核心集合，但在N-末端和C-末端不同。在过去的资助期内，我们 解决了该领域的几个关键问题。首先，我们发现这两个飞行的APC家族 在许多组织中，成员在Wnt信号中起冗余作用，尽管它们的结构和功能不同 在细胞内定位方面存在显著差异。其次，我们产生了APC2的零等位基因。vbl.使用 存在APC1的零等位基因，这使得我们第一次能够同时创造组织和整体 两个APC家族成员的动物都为零，揭示了两个APC家族成员的APC功能的零表型 WNT和细胞骨架调节。我们还产生了一系列新的APC2等位基因； 这些发现表明，结肠肿瘤特有的截短的APC蛋白减少 支持WNT监管，但不是零，支持“恰到好处”的假设。他们还透露，这些 截短的蛋白质对细胞骨架有明显的负面影响，但对Wnt信号转导没有影响。 尽管对APC非常感兴趣，但关于其在销毁中所扮演的角色，关键问题仍然存在 复杂的细胞骨架调节。我们提出了三个具体目标，每个目标都涉及关键问题： 目的1：明确APC蛋白在破坏复合体中的作用机制(S)。 目标2：确定APC结构如何影响销毁的组装和活动 复合体，调节连环蛋白向E3连接酶的转移 目的3：探索APC家族蛋白调控细胞骨架计划的机制 在人的正常发育过程中，身体的细胞相互交流。 胚胎和成人组织中调节组织维护和修复伤口。更改后的 细胞通讯是包括结肠癌在内的几种常见癌症的基础，而细胞通讯缺失 细胞通讯障碍会导致某些形式的先天性骨畸形。我们有 开发了一个模型系统来探索肿瘤抑制因子APC如何正常调节 细胞通信和细胞行为，以便更好地了解哪里出了问题 在人类疾病中。

Several key signal transduction pathways play critical roles in animal development, and also are inappropriately activated in cancer. Among these is the Wnt pathway. Its role in human cancer was first identified through the tumor suppressor Adenomatous polyposis coli (APC), mutated in most colon cancers. We now know that APC is a critical negative regulator of Wnt signaling. APC is part of a multiprotein "destruction complex" targeting the key Wnt effector ¿catenin for phosphorylation and eventual proteasomal destruction. Understanding APC function is essential both to understanding how Wnt signaling shapes normal development and how its inappropriate activation contributes to cancer. In addition to its role in Wnt regulation, APC also plays roles in cytoskeletal regulation. Diverse cytoskeletal functions have been ascribed to APC. Among these is a proposed role in chromosome instability in APC mutant tumors, via effects on chromosome segregation. We established a model system to study APC function in Wnt signaling and cytoskeletal regulation during normal development and to model how its inactivation leads to cancer. We use the fruit fly Drosophila, making use of the powerful combination of genetic, cell biological and biochemical tools available in flies. Both mammals and Drosophila have two APC family members, which all share a core set of protein domains but which differ at their N- and C-termini. In the past funding period, we addressed several key questions in the field. First, we discovered that the two fly APC family members act redundantly in Wnt signaling in many tissues, despite their divergent structures and striking differences in intracellular localization. Second, we generated a null allele of APC2. Using existing null alleles of APC1, this allowed us to create, for the first time, both tissues and whole animals null for both APC family members, revealing the null phenotypes of APC function in both Wnt and cytoskeletal regulation. We also generated a series of new APC2 alleles; among other findings these revealed that the truncated APC proteins characteristic of colon tumors are reduced for Wnt regulation but not null, supporting the "just right" hypothesis. They also revealed that these truncated proteins have dominant negative effects on the cytoskeleton but not in Wnt signaling. Despite the great interest in APC, key questions remain regarding its roles in the destruction complex and cytoskeletal regulation. We propose 3 Specific Aims, each addressing key questions: Aim 1: Define the mechanism(s) of action of APC proteins in the destruction complex. Aim 2: Determine how APC structure influences the assembly and activity of the destruction complex and regulates ¿catenin transfer to the E3 ligase Aim 3: Explore mechanisms by which APC family proteins regulate the cytoskeleton Project Narrative The body's cells communicate with one another during normal development of an embryo, and in adult tissues to regulate tissue maintenance and repair wounds. Altered cell communication underlies several common cancers including colon cancer, while loss of cell communication causes some forms of congenital bone malformation. We have developed a model system to explore how the tumor suppressor APC normally regulates cell communication and cell behavior, to allow better understanding of what goes wrong in human disease.