Molecular Interactions: Oral Bacteria & Matrix Proteins

描述（由申请人提供）：放线菌是一种革兰氏阴性兼性厌氧细菌，定植于人类口腔和上呼吸道。这种细菌与局部侵袭性牙周炎（LAP）和成人牙周炎病例密切相关。这种病原体是其他严重感染的病原体，包括感染性心内膜炎、软组织脓肿、肺炎，并可能导致心血管疾病。牙周组织被认为是这些非口腔疾病的来源，但放线菌属细菌在口腔内定植并在组织中浸润和传播的趋向性知之甚少。病原体已经发展出多种策略来成功地在宿主组织中定植。这些病原体之间的一个共同主题是在严格或恶劣条件下通过粘附特定宿主大分子来启动感染的能力。这些分子包括由宿主细胞分泌的形成细胞外基质（ECM）的蛋白质。放线菌病见于牙周组织结缔组织，与感染组织中的胶原纤维密切相关。这种细菌还与ECM蛋白、胶原蛋白、纤维连接蛋白和层粘连蛋白结合。利用遗传学方法，我们首次鉴定出a .放线菌（a . actinomycetemcomitans）的胶原黏附素、Ema（胞外基质蛋白黏附素）a和多个参与调节ECM蛋白黏附素活性表达的基因。EmaA在结构上与YadA相关，YadA是肠致病性小肠结肠炎耶尔森菌的多用途ECM蛋白粘附素，并与细菌细胞表面附属物相关。这些EmaA结构被认为是胶原粘附的基础。为了阐明EmaA在细菌定植和致病性中的作用，我们建议：1)通过测定放线菌A.放线菌的胶原结合、亚细胞定位和表面结构组装来绘制EmaA的功能域；2)通过透射电镜研究与EmaA相关的表面结构及其在抵抗宿主先天免疫反应中的作用。3)确定放线菌表面结构组装所需的EmaA分子数。提出的研究的长期目标是鉴定和表征口腔和非口腔组织定植所需的细菌粘附素。这些粘附素可以作为未来药物开发的靶点，包括小分子药物或破坏宿主-病原体相互作用的疫苗。Lay声明：与宿主组织结合是所有传染病的初始阶段。了解细菌如何与宿主细胞或组织成分相互作用将有助于开发新的治疗方法，以防止疾病的发生或进展。

DESCRIPTION (provided by applicant): Actinobacillus actinomycetemcomitans is a Gram-negative, facultative anaerobic bacterium that colonizes the human oral cavity and the upper respiratory tract. This bacterium is strongly associated with localized aggressive periodontitis (LAP) and with cases of adult periodontitis. This pathogen is the causative agent for other serious infections including infectious endocarditis, soft tissue abscesses, pneumonia, and may contribute to cardiovascular disease. The periodontium is believed to be the source for these non-oral diseases, but little is known about the tropism used by A. actinomycetemcomitans to colonize the oral cavity and to infiltrate and disseminate in tissues. Pathogens have developed diverse strategies to be successful in colonization of host tissues. A common theme amongst these pathogens is the ability to initiate infection by adhesion to specific host macromolecules under stringent or hostile conditions. These molecules include proteins secreted by host cells that form the extracellular matrix (ECM). A. actinomycetemcomitans is found in the connective tissue of the periodontium and in close association with collagen fibers in infected tissues. The bacterium also binds to the ECM proteins, collagen, fibronectin and laminin. Using a genetic approach, we have identified the first A. actinomycetemcomitans collagen adhesin, Ema (extracellular matrix protein adhesin) A and multiple genes involved in regulating the expression of ECM protein adhesin activity. EmaA is structurally related to YadA, a multipurpose ECM protein adhesin of the enteropathogenic bacterium Yersinia enterocolitica, and is associated with bacterial cell surface appendages. These EmaA structures are proposed to be fundamental for collagen adhesion. To elucidate the role of EmaA in colonization and pathogenicity of the bacterium, we propose to 1) map the functional domains of EmaA by determining the collagen binding, subcellular localization, and assembly of surface structures in A. actinomycetemcomitans, 2) investigate the surface structures associated with EmaA by transmission electron microscopy and the role of these structures in resistance to the innate immune response of the host, and 3) determine the number of EmaA molecules required for the assembly of structures on the surface of A. actinomycetemcomitans. A long term goal of the proposed research is to identify and characterize bacterial adhesins that are required for the colonization of the oral cavity and non-oral tissues. These adhesins may serve as targets for future drug development involving small molecules or vaccines that disrupt host-pathogen interactions. Lay statement: Binding to host tissues is the initial phase of all infectious diseases. Understanding how bacteria interact with host cells or tissue constituents will aid in the development of novel therapeutics to prevent initiation or progression of the disease.