An unexpected signaling output for the tumor suppressor APC

摘要 这项建议确定了结肠腺瘤性息肉病(APC)的新功能，APC是一种肿瘤抑制因子和 Wnt信号的负调节因子。APC纯合缺失导致人类息肉病和结肠癌 早期胚胎中的缺失会导致模式生物中的多种发育表型，例如 果蝇、斑马鱼和老鼠。APC突变导致？-catenin积聚，从而激活Wnt靶标 C-myc和细胞周期蛋白D1等基因。然而，在卵巢癌早期腺瘤中不能检测到核连环蛋白。 患有生殖系APC突变的患者(家族性腺瘤性息肉病(FAP))，也不是发育中的肠道 这表明在APC下游还需要额外的效应器。我们发现 APC直接增强糖原合成酶激酶-3(GSK-3)的活性，提供了意想不到的 依赖于APC抑制多个下游目标的机制，包括营养传感器 MTOR(雷帕霉素的机械靶点)和？连环蛋白。APC突变降低GSK-3活性，从而 在不同的活体环境中激活mTORC1，包括FAP患者的腺瘤、肠腺瘤 在小鼠和APC突变的斑马鱼胚胎中。我们的总体假设是APC直接激活GSK-3 该信号基序调控多条通路，包括？连环蛋白和mTOR信号通路。 该模型揭示了APC的一个关键的新功能，提供了一种由以下因素引起的mTOR激活机制 APC突变，并提示APC和其他独立于 WNT/？-连环蛋白。在本提案的目标1中，我们将定位APC的GSK-3激活结构域。在目标2中，我们将 在包括FAP患者在内的体内，探讨APC对mTOR的调节机制。目标3探索了 令人惊讶的是，APC突变在3天内导致斑马鱼出现戏剧性的肿瘤表型 这需要mTOR激活。我们将在斑马鱼中使用分子和遗传方法来表征 这些肿瘤可作为一种高度可及的体内模型来探讨APC信号转导和肿瘤发生。

Summary This proposal identifies a new function for Adenomatous polyposis coli (APC), a tumor suppressor and negative regulator of Wnt signaling. Homozygous loss of APC causes polyposis and colon cancer in humans and deletion in early embryos causes multiple developmental phenotypes in model organisms such as Drosophila, zebrafish, and mouse. Apc mutations cause accumulation of ß-catenin, which activates Wnt target genes such as c-myc and cyclin D1. However, nuclear ß-catenin is not detectable in early adenomas of patients with germline APC mutations (familial adenomatous polyposis (FAP)) nor in the developing intestines of apc mutant zebrafish, suggesting that additional effectors are required downstream of APC. We find that APC directly enhances the activity of glycogen synthase kinase-3 (GSK-3), providing an unexpected mechanism for APC-dependent suppression of multiple downstream targets, including the nutrient sensor mTOR (mechanistic Target of Rapamycin) and ß-catenin. APC mutations reduce GSK-3 activity, thereby activating mTORC1 in diverse in vivo settings including adenomas from patients with FAP, intestinal adenomas in mice, and apc mutant zebrafish embryos. Our overall hypothesis is that APC directly activates GSK-3 and that this signaling motif regulates multiple pathways, including ß-catenin and mTOR signaling. This model reveals a critical, new function for APC, provides a mechanism for mTOR activation caused by APC mutations, and suggests a link between APC and other signaling pathways that are independent of Wnt/ß-catenin. In aim 1 of this proposal, we will map the GSK-3 activation domain of APC. In aim 2, we will explore the mechanism of mTOR regulation by APC in vivo, including FAP patients. Aim 3 explores the surprising observation that apc mutation causes a dramatic neoplastic phenotype in zebrafish within 3 days that requires mTOR activation. We will use molecular and genetic approaches in zebrafish to characterize these tumors as a highly accessible, in vivo model to explore APC signaling and tumorigenesis.