Genetic and Cellular Basics of H. pylori pathogenesis

描述（由申请人提供）：H。幽门螺杆菌是一种独特地适合于在人胃中存活的显著微生物。它通常无症状地感染世界上一半以上的人口。然而，15%的感染者会发展为溃疡病或胃癌。我们提出的研究集中在一个单一的细菌决定簇，CagA，一个效应蛋白易位的细菌分泌装置到胃上皮细胞。CagA可以说是这种微生物最重要的毒力决定因素，因为它的存在与溃疡病和胃恶性肿瘤明显相关，并且它对宿主细胞生物学的影响使其处于微生物发病机制和癌症生物学之间的关键位置。我们提出了三个基本问题，涉及到如何在最初的遭遇之间的H。幽门螺杆菌CagA蛋白对微生物有利而对宿主有害。首先，CagA干扰宿主上皮细胞生物学的分子机制是什么？第二，CagA对H.幽门螺杆菌的生存与宿主细胞表面密切相关？最后，在动物模型中，CagA递送到胃粘膜的体内后果是什么？我们以前的研究指导我们明确关注CagA蛋白和顶端连接复合物的宿主蛋白的相互作用，顶端连接复合物是控制细胞极性的细胞结构域，提供粘膜的屏障功能，并调节上皮细胞的分化，生长和伤口愈合能力。CagA还触发一个或可能多个受体酪氨酸激酶信号通路。我们预测，这些不是不相关的功能，而是CagA篡夺生长因子受体信号传导和顶端连接之间的内在联系。我们还假设H.幽门螺杆菌利用CagA修饰宿主细胞表面以用于定殖目的，将特异性宿主蛋白质募集到细菌附着位点，破坏细胞极性，并打开上皮连接。我们提出了一个假设，我们相信可以在体外和体内进行测试的CagA行动。我们已经开发了新的显微镜工具和实验上易于处理的模型，慢性感染的极化细胞培养研究细胞生物学的CagA-宿主细胞相互作用。此外，我们还将广泛利用直接生化分离和转录分析，在分子水平上剖析CagA的作用。最后，我们建议测试的意见，我们已经从精确的体外分析中收集到的更复杂，但更相关的环境中的胃在动物宿主。

DESCRIPTION (provided by applicant): H. pylori is a remarkable microorganism that is uniquely adapted for survival in the human stomach. It infects, usually asymptomatically, over one half of the world's human population. However 15% of those infected will develop ulcer disease or gastric cancer. Our proposed research focuses on a single bacterial determinant, CagA, an effector protein translocated by a bacterial secretory apparatus into gastric epithelial cells. CagA is arguably the most important virulence determinant of this microbe, since its presence is clearly correlated with ulcer disease and gastric malignancy, and its effects on host cell biology place it at the crux between microbial pathogenesis and cancer biology. We propose to address three fundamental questions related to how the initial encounter between the H. pylori CagA protein works to the advantage of the microorganism and to the detriment of the host. First, what are the molecular mechanisms by which CagA perturbs host epithelial cell biology? Second, what is the role of CagA for H. pylori survival in close association with the host cell surface? And finally, what are the in vivo consequences of CagA delivery to the gastric mucosa in an animal model? Our previous research directs us to a clear focus on the interaction of the CagA protein and the host proteins of the apical junctional complex, a domain of the cell that controls cell polarity, provides the barrier function of the mucosa, and regulates the differentiation, growth and wound healing capacities of epithelia. CagA also triggers one, or possibly more, receptor tyrosine kinase signaling pathways. We predict that these are not unrelated functions, but rather that CagA usurps an intrinsic link between growth factor receptor signaling and the apical junctions. We have also hypothesized that H. pylori utilizes CagA to modify the host cell surface for colonization purposes, recruiting specific host proteins to the sites of bacterial attachment, disrupting cell polarity, and opening the epithelial junctions. We have proposed a hypothesis of CagA action that we believe can be tested both in-vitro and in-vivo. We have developed novel microscopic tools and an experimentally tractable model of chronic infection of polarized cells in culture to examine the cell biology of the CagA-host cell interaction. Moreover, we will also make extensive use of direct biochemical fractionation and transcriptional analysis to dissect the role of CagA at a molecular level. Finally we propose testing the observations we have gathered from precise in-vitro analysis in the more complex, but more relevant environment of the stomach in an animal host.