B.forsythus BsPA protein: role in virulence

描述：连翘拟杆菌是一种与牙周病发病机制有关的革兰氏阴性口腔厌氧菌。尽管对这种生物的毒力因子知之甚少，但根据我们最近的体外和体内研究，一种表面相关的98-kDa蛋白（BspA）被认为是一种毒力因子。BspA蛋白含有属于富亮氨酸重复基序家族（LRR）的同源序列，以及属于免疫球蛋白超家族（Ig-SF）的基序。在体外，BspA蛋白与细胞外基质成分纤维连接蛋白和纤维蛋白原结合，并与上皮细胞结合，诱导单核细胞释放促炎细胞因子。此外，在我们实验室构建的BspA表达缺陷的连翘突变体已被发现其与纤维连接蛋白、纤维蛋白原和上皮细胞结合的能力显著减弱。本文提出的研究将解决以下假设：lrr和IgSF结构域通过与特定细胞受体的结合对宿主细胞相互作用至关重要；BspA蛋白通过介导细菌定植和触发宿主细胞反应（如细胞因子和其他介质的释放）在发病过程中发挥重要作用。实验设计将包括：1)研究确定参与宿主细胞（上皮细胞和单核细胞）相互作用的特定BspA结构域（specific Aim 1a），并研究由BspA结合引起的细胞内信号传导事件（Aim 1b）；2)结合BspA蛋白的上皮受体（Aim 2a）和单核细胞受体（Aim 2b）的生化特性；3)通过牙周病小鼠模型（Aim 3a）和有牙周炎病史患者对BspA蛋白的宿主免疫应答来评估BspA蛋白在体内的作用（Aim 3b）。这一发现对于确定BspA蛋白的作用及其结构域在细菌发病机制中的潜在作用具有重要意义。从蛋白质组学的角度来看，这些研究对于确定其他细菌蛋白质中发现的LRR和igg样特征的作用也至关重要。从长远来看，了解bspa介导的连翘发病机制的基本机制将对制定牙周病的干预策略至关重要。

DESCRIPTION: Bacteroides forsythus is a Gram-negative oral anaerobe implicated in the development of periodontal disease pathogenesis. Although, very little is known about the virulence factors of this organism, based on our recent in vitro and in vivo studies, a surface-associated 98-kDa protein (BspA) has been suggested as a virulence factor. The BspA protein contains homologous sequences belonging to the leucine-rich repeat motif family (LRR), and to motifs belonging to the immunoglobulin superfamily (Ig-SF). In vitro, the BspA protein binds to extracellular matrix components fibronectin and fibrinogen, and to epithelial cells, and induces release of proinflammtory cytokines from monocytic cells. Further, a mutant of B. forsythus defective in BspA expression constructed in our laboratory has been found to be significantly attenuated in its ability to bind to fibronectin, fibrinogen, and epithelial cells. The studies proposed here will address the hypotheses that LRRs and IgSF domains are critical for host cell interactions via binding to specific cellular receptors, and that the BspA protein plays important roles in pathogenesis via mediating bacterial colonization and triggering of host cellular responses, such as release of cytokines and other mediators. The experimental design will include: 1) studies to determine the specific BspA-domains involved in host cell (epithelial and monocytic cells) interactions (Specific Aim 1a), and investigate intracellular signaling events resulting from BspA binding (Aim 1b); 2) biochemical characterization of epithelial (Aim 2a) and monocyte receptors (Aim 2b) that bind BspA protein; and 3) assessment of the in vivo role of BspA protein as judged by studies in a mouse model of periodontal disease (Aim 3a), and by evaluating the host immune response against the BspA protein in patients with a history of periodontitis (Aim 3b). The findings will be important in determining the roles of BspA protein, and the underlying contribution of its domains in bacterial pathogenesis. The studies will also be critical from a proteomic standpoint in defining the roles of LRR and Ig-like signatures found in other bacterial proteins in general. In the long term, understanding the basic mechanisms of the BspA-mediated pathogenesis of B. forsythus will be vital in developing intervention strategies against periodontal disease.