Molecular and genetic analysis of the hielcobacter pylori virulence Factor CagA

描述（由申请人提供）：幽门螺杆菌感染了世界上一半以上的人口，并与胃炎、消化性溃疡疾病和胃癌等多种胃疾病有关。幽门螺杆菌致病性菌株含有cag致病性岛，该岛编码能够将细菌效应蛋白CagA转运到宿主细胞中的IV型分泌系统。在宿主细胞内，CagA与包括磷酸酶SHP-2在内的许多宿主蛋白结合。宿主细胞中由CagA激活的分子通路，无论是依赖还是独立于SHP-2，目前还不清楚。该项目的长期目标是确定宿主细胞内CagA分子活性导致宿主细胞信号转导中断、上皮完整性丧失并最终促进癌变的机制。我们建立了一个转基因果蝇模型来研究CagA在视网膜上皮中的活性，该模型既是SHP-2信号转导的模型，也是上皮组织的模型。CagA在该组织中的表达诱导发育缺陷，既模仿SHP-2的激活（过量光感受器的规范），又不同于SHP-2的激活（上皮和光感受器微绒毛的破坏）。在平行研究中，我们已经证明了CagA导致幽门螺杆菌感染的培养胃上皮细胞的微绒毛破坏。利用这两个互补的系统，我们建议实现以下具体目标：

DESCRIPTION (provided by applicant): Helicobacter pylori infects over half the world's population and is associated with a broad range of gastric maladies including gastritis, peptic ulcer disease, and gastric cancer. Pathogenic strains of H. pylori contain the cag pathogenicity island that encodes a type IV secretion system capable of translocating the bacterial effector protein CagA into host cells. Inside the host cell, CagA binds to a number of host proteins including the phosphatase SHP-2. The molecular pathways activated by CagA in host cells, both dependent and independent of SHP-2, are not well understood. The long-term goal of this project is to determine the mechanisms by which CagA's molecular activity within host cells leads to disruption of host cell signal transduction, loss of epithelial integrity, and ultimately the promotion of carcinogenesis. We have developed a transgenic Drosophila model to study CagA's activity in the retinal epithelium, which is both a model for SHP-2 signal transduction and for epithelial organization. CagA expression in this tissue induces developmental defects that both mimic activation of SHP-2 (specification of excess photoreceptors) and are distinct from SHP-2 activation (disruption of the epithelium and photoreceptor microvilli). In parallel studies we have demonstrated that CagA causes disruption of microvilli in H. pylori infected cultured gastric epithelial cells. Using these two complementary systems, we propose to address the following specific aims: 1. Test the hypothesis that CagA has SHP-2 independent activities in eukaryotic tissues. 2. Test the hypothesis that CagA disrupts epithelial cell microvilli independently of SHP-2 function. 3. Identify genes that mediate CagA function in eukaryotic cells. Stomach cancer is the second leading cause of cancer death worldwide. Over half of all stomach cancers are thought to be caused by infection with the bacterium H. pylori. During H. pylori infection the bacteria translocate a protein, CagA, into stomach cells, which causes changes in the cells that promote cancer. We propose to determine the molecular basis for CagA's effects on stomach cells as a ways to better understand, diagnose, and treat stomach cancer.