Interactions of Helicobacter pylori CagA with Host Factors

描述(申请人提供)：幽门螺杆菌是一种革兰氏阴性、嗜氧微氧胃病原体，感染近50%的人类人口。它是唯一能够定植于胃的病原体，并与十二指肠和胃溃疡以及腺癌密切相关。该细菌已被世界卫生组织列为第一类致癌物质。幽门螺杆菌的CagA细胞毒素通过IV型分泌系统转运到宿主细胞内，与许多细胞蛋白相互作用，增加毒力，并与癌症风险增加有关。CagA具有多种宿主细胞功能，包括细胞骨架功能、细胞间黏附和细胞内信号转导等。然而，近二十年来，CagA的功能在很大程度上仍然是一个谜。我们实验室的初步数据正在改变这种情况。我们已经确定了与宿主靶标结合的CagA的高分辨晶体结构，已经确定了这种大细胞毒素的稳定的、可溶的亚区，并已经确定了与这些毒素相互作用的新的宿主因子 子域。这项申请建议对这些已识别的亚域及其与宿主因子的相互作用进行生化、结构和感染生物学研究。具体目标是(1)鉴定CagA功能亚区，生化和结构表征CagA-宿主因子的相互作用。预期结果包括获得CagA宿主因子相互作用的详细晶体结构，这些相互作用的性质和作用的生化特征 在调节宿主细胞生物学中的相互作用。这些数据将极大地增强我们对毒力以及幽门螺杆菌驱动的致癌作用的理解。 公共卫生相关性：世界上每两个人中就有一个感染幽门螺杆菌，并与胃癌有关。幽门螺杆菌将CagA蛋白注射到胃细胞中，从而解除了感染细胞的许多功能。我们建议分离CagA与人类蛋白质的相互作用，并在分子水平上对它们进行成像，以了解CagA是如何发挥作用的。这样的理解将是揭开CagA介导的毒力和对人类癌症的贡献的第一步。

DESCRIPTION (provided by applicant): Helicobacter pylori is a Gram negative, microaerophilic gastric pathogen that infects nearly 50% of the human population. It is the sole pathogen able to colonize the stomach, and has been closely linked to duodenal and gastric ulcers and adenocarcinomas. The bacterium has been listed as a Group 1 carcinogen by the World Health Organization. The CagA cytotoxin of H. pylori is translocated into host cells by a Type IV Secretion System, interacts with many cellular proteins, increases virulence, and is associated with an increased risk of cancer. CagA has been shown to manipulate many host cellular functions, including cytoskeletal function, cell- to-cell adhesion, and intracellular signl transduction. However, how CagA functions has remained mostly a mystery for nearly two decades. Preliminary data from our laboratory is changing this situation. We have determined high-resolution crystal structures of CagA bound to host targets, have identified stable, soluble subdomains of this large cytotoxin, and have identified novel host factors that interact with these subdomains. This application proposes to perform biochemical, structural, and infection biological studies of these identified subdomains and their interactions with host factors. The specific aims are (1) to identify, biochemically and structurally characterize the CagA functional subdomains, and (2) to identify, biochemically and structurally characterize the CagA-host factor interactions. Expected outcomes include obtaining detailed crystal structures of CagA host factor interactions, biochemical characterization of the nature of these interactions, and the role of the interactions in modulating host cell biology. Such data will greatly enhance our understanding of virulence, as well as Helicobacter driven carcinogenesis. PUBLIC HEALTH RELEVANCE: The bacterium Helicobacter pylori infects one out of every two people in the world, and is linked to stomach cancer. Helicobacter pylori injects the CagA protein into stomach cells, which deregulates many functions of the infected cell. We propose to isolate the interactions CagA makes with human proteins, and image them at the molecular level to understand how CagA functions. Such an understanding will be the first step in unraveling CagA mediated-virulence and contributions to human cancers.