Pathogenesis of Helicobacter pylori infection

描述(由申请人提供)： 幽门螺杆菌是一种革兰氏阴性细菌，在人的胃中定居。幽门螺杆菌感染与患远端胃癌和消化性溃疡疾病的风险增加有关。在以前的研究中，我们已经对一种分泌型幽门螺杆菌毒素(VacA)进行了详细的分析。幽门螺杆菌基因组包含三个与VacA有远亲关系的基因，每个基因编码一个250 kDa的蛋白质。与VacA相似，这些VacA样蛋白预计由V型(自动转运蛋白途径)分泌。由自身转运蛋白途径分泌的细菌蛋白通常在传染病的发病机制中发挥重要作用。与已经被详细研究的VacA相反，到目前为止，对Hp VacA样蛋白的研究很少。最近的研究表明，一种VacA样蛋白(FAAA)定位于鞭毛并在幽门螺杆菌的运动中起作用，另一种VacA样蛋白(ImaA)具有抗炎活性。假设：这一提议的主要假设如下：(I)VacA样蛋白的转录受到严格调控，以响应多种刺激，从而允许以一种优化幽门螺杆菌在人胃中定植的方式协调表达这些蛋白，以及(Ii)每种VacA样蛋白都具有专门的功能，旨在增强幽门螺杆菌在胃的定植。研究目的：本研究的长期目标是了解幽门螺杆菌在人胃粘膜中定植和存活的分子机制，了解幽门螺杆菌感染导致胃癌或消化性溃疡疾病发生的分子机制，并开发有效的预防胃癌和消化性溃疡疾病的策略。具体目标是：(1)明确FAAA和IMAA的调控机制；(2)明确FAAA和IMAA在幽门螺杆菌定植和幽门螺杆菌引起的胃病中的作用；(3)确定IMAA调节幽门螺杆菌诱导的炎症反应的机制。方法：为了研究FAAA和imaA的表达调控，我们将对这些基因的启动子区域进行深入的研究，并确定负责所观察到的基因表达调控的调控系统。我们将通过使用一个允许在可诱导启动子控制下表达这些蛋白的系统来研究FAAA和ImaA在体内的作用。最后，我们将使用多种方法来研究ImaA的存在或不存在如何影响多种表型，包括CAG IV型分泌系统的组装。

DESCRIPTION (provided by applicant): Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach. H. pylori infection is associated with an increased risk of cancer of the distal stomach and peptic ulcer disease. In previous studies, we have conducted detailed analyses of a secreted H. pylori toxin (VacA). The H. pylori genome contains three genes that are distantly related to vacA, and each encodes a protein >250 kDa in size. Similar to VacA, these VacA-like proteins are predicted to be secreted by a type V (autotransporter pathway). Bacterial proteins that are secreted by autotransporter pathways typically have important roles in the pathogenesis of infectious diseases. In contrast to VacA, which has been studied in great detail, thus far there has been very little study of H. pylori VacA-like proteins. Recent studies provide evidence that one of the VacA-like proteins (FaaA) localizes to flagella and has a role in H. pylori motility, and another VacA-like protein (ImaA) has anti-inflammatory activity. Hypotheses: The overarching hypotheses of this proposal are as follows: (i) the transcription of VacA-like proteins is tightly regulated in response to multiple stimuli, thereby allowing orchestrated expression of these in a manner that optimizes H. pylori colonization of the human stomach, and (ii) each of the VacA-like proteins has a specialized function designed to enhance H. pylori colonization of the stomach. Study Objectives: The long-term goals of this work are to understand the molecular mechanisms that allow H. pylori to colonize and persist in the human gastric mucosa, to understand the molecular mechanisms by which H. pylori infection leads to the development of gastric cancer or peptic ulcer disease, and to develop effective strategies for the prevention of gastric cancer and peptic ulcer disease. The specific objectives are (i) to define the mechanisms by which faaA and imaA are regulated; (ii) to define the roles of FaaA and ImaA in H. pylori colonization of the stomach and H. pylori-induced gastric disease; and (iii) to define mechanisms by which ImaA modulates H. pylori-induced inflammatory responses. Methods: To investigate the regulation of faaA and imaA expression, we will undertake in-depth studies of the promoter regions of these genes and identify regulatory systems that are responsible for the observed regulation of gene expression. We will investigate the roles of FaaA and ImaA in vivo through use of a system that allows expression of these proteins under control of an inducible promoter. Finally, we will use multiple approaches to investigate how the presence or absence of ImaA influences multiple phenotypes, including assembly of the cag type IV secretion system.