Genetic and Cellular Basics of H. pylori pathogenesis

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， t感染，通常无症状，超过一半的世界人口。然而，15%的 受感染者会患上溃疡病或胃癌。我们的研究重点是一个单一的 细菌决定簇，CagA，一种由细菌分泌器转运到 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 ts存在与溃疡病和胃恶性肿瘤明显相关，其对宿主细胞的影响 生物学将其置于微生物发病机制和癌症生物学之间的关键位置。我们建议解决 三个基本问题涉及到如何在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？第二，什么是角色 CagA for H.幽门螺杆菌的生存与宿主细胞表面密切相关？最后，什么是在- 在动物模型中CagA递送到胃粘膜的体内后果？我们之前的研究 引导我们明确关注CagA蛋白和顶端的宿主蛋白的相互作用， 连接复合物是控制细胞极性的细胞结构域，提供细胞膜的屏障功能。 粘膜，并调节上皮细胞的分化、生长和伤口愈合能力。CagA也 触发一个或可能多个受体酪氨酸激酶信号通路。我们预测， 不是无关的功能，而是CagA篡夺了生长因子受体之间的内在联系， 信号传导和顶端连接。我们还假设H. pylori利用CagA修饰 宿主细胞表面用于定殖目的，将特定的宿主蛋白质募集到细菌的位点， 附着，破坏细胞极性，并打开上皮连接。我们提出了一种 CagA作用的假说，我们相信可以在体外和体内进行测试。我们已经开发 新的显微工具和实验上易于处理的极化细胞慢性感染模型， 培养以检查CagA-宿主细胞相互作用的细胞生物学。此外，我们还将使 广泛使用直接生化分离和转录分析来剖析CagA的作用 在分子水平上。最后，我们建议测试我们从精确的体外实验中收集到的观察结果。 在更复杂但更相关的动物宿主胃环境中进行分析。

H. pylori is a remarkable microorganism that is uniquely adapted for survival in the human stomach, t 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 ts 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.