Interactions of Helicobacter pylori CagA with Host Factors

描述（由申请人提供）：幽门螺杆菌是一种革兰氏阴性、嗜微气的胃病原体，感染近50%的人口。它是唯一能够在胃中定植的病原体，与十二指肠溃疡和胃溃疡以及腺癌密切相关。这种细菌已被世界卫生组织列为1类致癌物。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中，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已被证明操纵许多宿主细胞功能，包括细胞骨架功能、细胞间粘附和细胞内信号转导。然而，近二十年来，CagA的功能一直是一个谜。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点结合的CagA的高分辨率晶体结构，已经确定了这种大型细胞毒素的稳定，可溶的亚结构域，并且已经确定了与这些相互作用的新宿主因子

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.