Type IV Protein Secretion in Helicobacter pylori

项目概要（摘要） 幽门螺杆菌是一种革兰氏阴性细菌，定植在人类胃中。H.幽门螺杆菌定植 胃会导致慢性胃粘膜炎症，是胃癌的一个重要危险因素， 十二指肠或胃溃疡。胃癌是全球癌症相关死亡的第三大原因， H.幽门螺杆菌已被世界卫生组织归类为I型致癌物。螺杆幽门螺杆菌CagA蛋白 通过IV型分泌系统（T4 SS）分泌，进入胃细胞，并引起细胞内 与恶性转化相关的信号传导。CagA和CagT 4SS的组分由以下编码： 基因位于一个被称为cag致病岛（派）的染色体区域内，它存在于一些H. pylori菌株而不是其他菌株。症状性胃十二指肠疾病（胃癌或消化性溃疡）的发病率 溃疡）在感染cag PAI阳性菌株的个体中高于感染cag的个体 PAI阴性菌株。对该菌的分子结构和蛋白质组成进行了研究。pylori Cag T4 SS差异 基本上与在其他细菌物种中发现的T4 SS的相应特征不同。总体长期 本研究的目的是更好地了解H.幽门螺杆菌病因 胃病。在上一个资助期间，我们分离了Cag的跨膜核心复合物， T4 SS含有cag派编码的5个蛋白，描述了该复合物的3个主要结构特征 （外膜帽，周质环和柄），并建立了部分模型的三个蛋白质的复合物。 本提案的目的是：i）建立五个Cag T4 SS核心复合体的完整结构模型 ii）定义CagY（预测跨越的核心复合物组分）的结构-功能关系 从内膜到外膜），阐明其在CagA募集和T4 SS活性中的作用; 和（iii）确定Cag T4 SS在体内的作用。方法将包括单粒子冷冻电子显微镜 T4 SS核心复合物的分析，H.幽门螺杆菌，细胞培养- CagT 4SS活性测定和H.幽门诱发胃癌这些研究将 为我们理解H.幽门螺杆菌感染可 导致胃癌和其他胃疾病。在更广泛的范围内，这些研究将增加我们的 了解细菌分泌系统和细菌毒力因子进入宿主细胞的传递， 以及微生物致癌的分子机制。

PROJECT SUMMARY (ABSTRACT) Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach. H. pylori colonization of the stomach results in chronic gastric mucosal inflammation and is a strong risk factor for gastric cancer and duodenal or gastric ulceration. Gastric cancer is the third leading cause of cancer-related death worldwide, and H. pylori has been classified as a type I carcinogen by the World Health Organization. The H. pylori CagA protein is secreted through a type IV secretion system (T4SS), enters gastric cells, and causes alterations in cellular signaling associated with malignant transformation. CagA and components of the Cag T4SS are encoded by genes within a chromosomal region known as the cag pathogenicity island (PAI), which is present in some H. pylori strains but not others. The incidence of symptomatic gastroduodenal disease (gastric cancer or peptic ulceration) is higher among individuals infected with cag PAI-positive strains than among those infected with cag PAI-negative strains. The molecular architecture and protein composition of the H. pylori Cag T4SS differ substantially from corresponding features of T4SSs found in other bacterial species. The overarching long-term goal of this research is to develop a better understanding of the molecular mechanisms by which H. pylori causes gastric disease. During the previous funding period, we isolated a transmembrane core complex of the Cag T4SS containing five proteins encoded by the cag PAI, described three main structural features of the complex (outer membrane cap, periplasmic ring and stalk), and built partial models of three proteins within the complex. The aims of the current proposal are i) to build a complete structural model of the five Cag T4SS core complex components; ii) to define structure-function relationships for CagY (a core complex component predicted to span from the inner membrane to the outer membrane), elucidating its role in CagA recruitment and T4SS activity; and (iii) to define actions of the Cag T4SS in vivo. Methods will include single particle cryo-electron microscopy analysis of the T4SS core complex, specialized techniques for genetic manipulation of H. pylori, cell culture- based assays of Cag T4SS activity, and an animal model of H. pylori-induced gastric cancer. These studies will provide important advances in our understanding of the molecular mechanisms by which H. pylori infection can lead to gastric cancer and other gastric diseases. On a broader scope, these studies will increase our understanding of bacterial secretion systems and the delivery of bacterial virulence factors into host cells, as well as molecular mechanisms underlying microbe-induced carcinogenesis.