Mechanistic Dissection of Pheromone-Dependent Regulation of Group A Streptococcal

描述(申请人提供)：A组链球菌(GAS)，一种能够局部和系统感染的病原体，已知在体外和体内生长过程中以时间模式分泌大量毒力因子，表明存在复杂的调控电路。分泌的半胱氨酸蛋白酶、SpeB的表达水平与疾病的严重程度呈负相关[1-3]。对于SpeB的表达来说，所谓的“独立”调控因子RGG(也称为RopB)是必需的，但还不够。此外还需要一种未知的生长阶段依赖因子，但仍难以捉摸[4-6]。我们的初步数据表明，未知因素是一种细菌产生的信息素，其性质与小肽一致。此外，分析预测RGG是一个多肽结合的转录因子，与其他群体感应系统的PlcR和PRGX具有结构同源性。需要检验的总体假设是，信息素调节RGG的活性，以控制SpeB转录。这背离了依赖RGG的途径对环境变化做出反应的范式；相反，我们提供了令人信服的证据，证明气体产生自己的动力来诱导SPB。我们的初步结果表明，在GAS中发现的RGG Paralog确实对小肽信息素有反应，这为我们的假设提供了一个令人信服的先例，也是RGG蛋白是群体感应效应器的第一个例子。我们的研究目标将是确定存在于培养上清液中的信号信息素(S)，并表征其产生和被气体识别的机制。这些系统的遗传破坏将在局部和侵袭性感染模型中测试它们的贡献。GAS利用RGG蛋白进行细胞间信号传递的证明，将为未来旨在干扰GAS和其他含RGG生物的细胞间信号传递的治疗方法的开发提供基础。

DESCRIPTION (provided by applicant): Group A Streptococcus (GAS), a pathogen capable of both localized and systemic infection, is known to secrete numerous virulence factors in temporal patterns during growth in vitro and in vivo, indicating the presence of intricate regulatory circuits. An inverse relationship exists between expression levels of the secreted cysteine protease, SpeB, and severity of disease [1-3]. The so-called "stand-alone" regulator Rgg (also known as RopB) is required, but is not sufficient, for expression of SpeB. An unknown growth-phase-dependent factor is additionally required, but has remained elusive [4-6]. Our preliminary data demonstrate that the unknown factor is a bacterially-produced pheromone with properties consistent with a small peptide. Additionally, analysis predicts that Rgg is a peptide-binding transcription factor with structural homology to PlcR and PrgX of other quorum sensing systems. The overall hypothesis to be tested is that a pheromone modulates the activity of Rgg for the purpose of controlling speB transcription. This is a departure from the paradigm that the Rgg-dependent pathway responds to environmental changes; instead, we provide compelling evidence that GAS produces its own impetus to induce speB. Our preliminary results demonstrate that Rgg paralogs found in GAS are indeed responsive to small peptide pheromones, providing a convincing precedent for our hypothesis and are the first examples that Rgg proteins are quorum sensing effectors. The goal of our research will be to define the signaling pheromone(s) present in culture supernatants and characterize the mechanism for its production and recognition by GAS. Genetic disruption of these systems will be tested for their contributions in localized and invasive infection models. Demonstration that GAS utilizes Rgg proteins for cell-to-cell signaling will provide a foundation for future development of therapies designed to interfere with intercellular signaling in GAS and in other Rgg-containing organisms.