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，定植在人类胃中。H.幽门螺杆菌感染与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，我们已经进行了详细的分析分泌H。幽门螺杆菌毒素（VacA）。螺杆pylori基因组包含三个与vacA有较远关系的基因，每个基因编码一个大小>250 kDa的蛋白质。与VacA类似，这些VacA样蛋白被预测由V型（自身转运途径）分泌。通过自身转运途径分泌的细菌蛋白通常在感染性疾病的发病机制中具有重要作用。与VacA相比，迄今为止对H. pylori VacA样蛋白。最近的研究表明，其中一种VacA样蛋白（FaaA）定位于鞭毛，并在H. pylori运动，另一种VacA样蛋白（ImaA）具有抗炎活性。假设条件：该提议的总体假设如下：（i）VacA样蛋白的转录响应于多种刺激而受到严格调控，从而允许以优化H的方式协调这些蛋白的表达。pylori在人胃中的定殖，和（ii）每种VacA样蛋白具有专门的功能，旨在增强H.幽门螺杆菌在胃中的定植。研究目标：这项工作的长期目标是了解H。pylori在人胃粘膜中的定植和持续存在，以了解H.幽门螺杆菌感染导致胃癌或消化性溃疡病的发展，并制定有效的策略，预防胃癌和消化性溃疡病。具体目标是：（i）确定faaA和imaA的调节机制;（ii）确定FaaA和ImaA在H.幽门螺杆菌在胃内定植;幽门螺杆菌诱导的胃疾病;和（iii）定义的机制，通过ImaA调节H。幽门诱导的炎症反应。研究方法：为了研究faaA和imaA表达的调控，我们将对这些基因的启动子区域进行深入研究，并确定负责观察到的基因表达调控的调控系统。我们将研究FaaA和ImaA在体内的作用，通过使用一个系统，允许这些蛋白质的诱导型启动子的控制下表达。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.