Mechanisms of Salmonella Invasion and Transmigration

沙门氏菌入侵和迁移的机制

• 批准号: 8039560
• 负责人: James E. Casanova
• 金额: $ 38.25万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-03-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8039560
• 关键词: Mechanisms; Salmonella; Invasion; Transmigration

DESCRIPTION (provided by applicant): Salmonella infect their animal hosts by entering into and traversing the intestinal epithelial barrier. Penetration of the epithelium is primarily achieved by direct invasion of host epithelial cells using a panel of effector molecules secreted through a Type III secretion apparatus. SipC, which forms part of the tip of this apparatus, has long cytoplasmic N- and C-termini, which nucleate the assembly of actin filament networks that are required for bacterial engulfment. Using a yeast two-hybrid screen, we identified a number of host proteins that interact selectively with the C-terminus of SipC. These include proteins that regulate actin assembly and dynamics, as well as proteins that mediate vesicular transport. We hypothesize that Salmonella uses SipC to nucleate the assembly of signaling and cytoskeletal machinery at sites of bacterial attachment to coordinate actin remodeling with the delivery of new membrane to form the nascent phagosome. This hypothesis will be explored in Specific Aim 1. Salmonella infection triggers the recruitment of inflammatory monocytes to the intestine, which have an important role in clearance of the infection. However, Salmonella can also use phagocytes as vehicles for their systemic dissemination, and the success or failure of the host response lies in the balance between these two processes. We are examining the role of Focal Adhesion Kinase (FAK) in the migration and function of monocytic cells. Using mice that conditionally lack FAK in cells of the myeloid lineage, we found that infiltration of inflammatory macrophages into the Peyer's patches and mesenteric lymph nodes is impaired in the absence of FAK, and that this surprisingly correlates with reduced bacterial colonization of all tissues examined. Conversely, neutrophil infiltration into the same tissues is enhanced, suggesting a differential regulation of macrophage and neutrophil recruitment to infected tissues. We hypothesize that inflammatory macrophages are necessary for bacterial survival in the tissue microenvironment, by providing a protective niche for bacterial replication and dissemination, and that in the absence of this niche bacteria are more efficiently killed by infiltrating neutrophils. This hypothesis will be tested in Specific Aim 2. Recent evidence indicates the existence of a novel population of lysozyme-expressing dendritic cells unique to the Peyer's patch, that are the first cells targeted by Salmonella upon transiting the intestinal epithelium. However nothing is known about the role of these cells in Salmonella infection. Characterization of these cells forms the basis for Specific Aim 3. Together, the results of these studies will provide significant new insight into the mechanisms used by Salmonella to infect their animal hosts, and the role of the innate immune response in combating the infection. The molecular details that emerge from these studies may provide new targets for next generation antibiotics or therapies for the prevention of Salmonellosis. PUBLIC HEALTH RELEVANCE: Infection with pathogenic Salmonella strains causes symptoms ranging from gastritis to potentially fatal systemic disease such as Typhoid Fever. The goals of this research are to define the host cell machinery that is subverted by Salmonella to enter the intestinal epithelium and spread systemically, and to characterize the innate immune responses to Salmonella infection.

描述（由申请人提供）：沙门氏菌通过进入和穿越肠上皮屏障来感染其动物宿主。上皮的渗透主要是通过使用通过III型分泌设备分泌的效应分子直接侵袭宿主上皮细胞来实现的。构成该设备尖端的一部分的SIPC具有长的细胞质N和C末端，它们是细菌吞噬所需的肌动蛋白丝网络的组装。使用酵母两杂交屏幕，我们确定了许多与SIPC的C端选择性相互作用的宿主蛋白。这些包括调节肌动蛋白组装和动力学的蛋白质，以及介导水泡转运的蛋白质。我们假设沙门氏菌使用SIPC在细菌附着的位点进行信号传导和细胞骨架机械的组装，以与递送新膜的一起坐标肌动蛋白重塑以形成新生的吞噬体。该假设将在特定的目标1中进行探讨。沙门氏菌感染会触发炎症单核细胞向肠的募集，这在清除感染中具有重要作用。但是，沙门氏菌还可以将吞噬细胞用作系统传播的车辆，而宿主反应的成功或失败在于这两个过程之间的平衡。我们正在研究焦点粘附激酶（FAK）在单核细胞迁移和功能中的作用。使用在髓样谱系细胞中有条件缺乏FAK的小鼠，我们发现炎症性巨噬细胞浸润到Peyer的斑块中，而在没有FAK的情况下会损害肠系膜和肠系膜淋巴结，并且在缺乏FAK的情况下，这与所检查的所有组织的细菌群体化的降低相关。相反，嗜中性粒细胞浸入相同的组织被增强，表明对感染组织的巨噬细胞和中性粒细胞募集的差异调节。我们假设炎症性巨噬细胞对于组织微环境中的细菌存活是必要的，它通过提供细菌复制和传播的保护性生态位，并且在没有这种小裂细菌的情况下，被浸润性中性粒细胞更有效地杀死。该假设将在特定的目标2中进行检验。最近的证据表明，存在于Peyer斑块所独有的表达溶菌酶的树突状细胞的新型人群，该细胞是沙门氏菌在转移肠上皮上皮时的第一个细胞。但是，这些细胞在沙门氏菌感染中的作用一无所知。这些细胞的表征构成了特定目标3的基础。共同，这些研究的结果将为沙门氏菌用来感染动物宿主的机制提供重大的新见解，以及先天免疫反应在对抗感染中的作用。这些研究中出现的分子细节可能为预防沙门氏菌病预防的下一代抗生素或疗法提供了新的靶标。 公共卫生相关性：致病性沙门氏菌菌株的感染会导致从胃炎到潜在致命的全身性疾病（如伤寒）的症状。这项研究的目标是定义沙门氏菌颠覆以进入肠上皮并系统地扩散的宿主细胞机制，并表征对沙门氏菌感染的先天免疫反应。