Inter-kingdom signaling by A. actinomycetemcomitans

描述(申请人提供)：牙周炎是一种广泛且昂贵的疾病，主要表现在口腔，但也与系统性疾病有关，如动脉粥样硬化和类风湿性关节炎。尽管有几种生物已经被 伴生放线菌被鉴定为牙周病原体，与侵袭性牙周炎密切相关。我们以前的工作表明群体感应对于伴随放线菌的毒力是必不可少的，我们发现QseBC双组分系统是群体感应途径的关键组成部分。我们的新结果表明，QseBC可能与宿主产生的儿茶酚胺激素相互作用，因此，QseBC可能既介导细胞密度依赖的信号转导，也可能介导跨王国信号转导。这项应用重点研究了这两个组分系统与儿茶酚胺激素的相互作用机制，并可能在调节伴生放线菌对铁的吸收方面发挥作用。目标1将确定儿茶酚胺激素和铁是否代表激活QseBC的信号，并确定结合所需的QSec传感器的功能基序。在QseBC激活时受到调控的基因也将使用基因组微阵列进行识别。目的2将研究编码肠动蛋白受体和转运蛋白的操纵子，并确定该受体是否与儿茶酚胺-铁复合体相互作用。肠结肠素受体对毒力的贡献也将通过牙周炎的小鼠模型来检验。我们还表明，QseBC可能通过两个铁响应毒素-抗毒素(TA)系统的活性与细胞应激反应偶联。这一调控网络将在目标3中进行研究，以确定应激蛋白水解酶的表达是否在铁限制条件下被诱导，以及这些蛋白水解酶是否通过降解不稳定的抗毒素来激活TA毒素。TA毒素激活对放线菌伴生放线菌QseBC表达和毒力的影响也将被测定。这项研究的总体目标是更好地了解基本的QseBC双组分系统激活的功能结果，以及通过QseBC的信号如何有助于毒力。

DESCRIPTION (provided by applicant): Periodontitis is a widespread and costly disease that is primarily manifest in the oral cavity but is also associated with systemic dieases such as atherosclerosis and rheumatoid arthritis. Although several organisms have been identified as periodontal pathogens, A. actinomycetemcomitans has been strongly associated with aggressive forms of periodontitis. Our prior work showed that quorum sensing is essential for A. actinomycetemcomitans virulence and we identified the QseBC two component system as a critical component of the quorum sensing pathway. Our new results suggest that QseBC may interact with catecholamine hormones produced by the host and thus, QseBC may mediate both cell density dependent signaling and inter-kingdom signaling. This application focuses on the mechanisms of interaction of the two component system with catecholamine hormones and is potential role in regulating iron uptake by A. actinomycetemcomitans. Aim 1 will determine if catecholamine hormones and iron represent signals that activate QseBC and identify functional motifs of the QseC sensor that are required for binding. The genes that are regulated upon activation of QseBC will also be identifed using genomic microarrays. Aim 2 will study an operon encoding a putative enterobactin receptor and transporter and determine if this receptor interacts with catecholamine-iron complexes. The contribution of the enterobactin receptor to virulence will also be examined using a mouse model of periodontitis. We have also shown that QseBC may be coupled to the cell stress response through the activity of two iron responsive toxin-antitoxin (TA) systems. This regulatory network will be studied in Aim 3 to determine if the expression of stress proteases is induced under iron limiting conditions and whether these proteases activate the TA toxins by degrading the labile antitoxin. The effect of TA toxin activation on the expression of QseBC and virulence of A. actinomycetemcomitans will also be determined. The overall goal of this study is to better understand the functional outcomes of activation of the essential QseBC two component system and how signaling through QseBC contributes to virulence.