Mechanistic Dissection of Pheromone-Dependent Regulation of Group A Streptococcal

描述（由申请人提供）：A群链球菌（GAS）是一种能够局部和全身感染的病原体，已知在体外和体内生长过程中以时间模式分泌许多毒力因子，表明存在复杂的调节回路。分泌的半胱氨酸蛋白酶、SpeB的表达水平与疾病严重程度呈反比关系[1-3]。对于SpeB的表达，所谓的“独立”调节因子Rgg（也称为RopB）是必需的，但不是充分的。另外还需要一个未知的生长阶段相关因子，但仍然难以捉摸[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，其性质与一种小肽一致。此外，分析预测Rgg是一种肽结合转录因子，与其他群体感应系统的PlcR和PrgX具有结构同源性。要测试的总体假设是信息素调节Rgg的活性以控制speB的转录。这与rgg依赖通路响应环境变化的范式不同；相反，我们提供了令人信服的证据，证明GAS产生自己的动力来诱导speB。我们的初步结果表明，在GAS中发现的Rgg类似物确实对小肽信息素有反应，为我们的假设提供了令人信服的先例，并且是Rgg蛋白是群体感应效应物的第一个例子。我们的研究目标将是定义培养上清中存在的信号信息素，并表征其产生和被GAS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进行测试。证明GAS利用Rgg蛋白进行细胞间信号传导，将为未来开发干扰GAS和其他含Rgg生物细胞间信号传导的疗法提供基础。

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.