Mechanistic Dissection of Pheromone-Dependent Regulation of Group A Streptococcal

描述（由申请人提供）：A组链球菌（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期间以时间模式分泌多种毒力因子，表明存在复杂的调控回路。分泌型半胱氨酸蛋白酶SpeB的表达水平与疾病严重程度之间存在反比关系[1-3]。所谓的“独立”调节器Rgg（也称为RopB）对于SpeB的表达是必需的，但不是足够的。另外还需要一种未知的生长期依赖因子，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与小肽的属性一致。 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。待检验的总体假设是，信息素调节Rgg的活性以控制speB转录。这是一个从RGG依赖性途径响应环境变化的范式出发，相反，我们提供了令人信服的证据，GAS产生自己的动力来诱导speB。我们的初步结果表明，RGG旁系同源物中发现的气体确实是响应小肽信息素，为我们的假设提供了一个令人信服的先例，是第一个例子，RGG蛋白的群体感应效应。我们研究的目标是确定存在于培养上清液中的信号信息素，并表征其产生和GAS识别的机制。这些系统的遗传破坏将在局部和侵入性感染模型中进行测试。GAS利用Rgg蛋白进行细胞间信号传导的证明将为未来开发旨在干扰GAS和其他含Rgg生物体中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.