Deciphering how bacterial pheromone signaling enhances Listeria virulence

 描述（由申请人提供）：单核细胞增生李斯特菌（Lm）是一种食源性兼性胞内细菌病原体，是美国历史上一些最致命的污染食品爆发的原因。虽然健康个体的疾病通常仅限于胃肠炎，但严重的侵袭性疾病发生在易感人群中，包括 免疫受损个体、孕妇、新生儿和老年人。结核分枝杆菌感染通常与脑膜炎、脑膜脑炎、脑水肿、心脏感染、败血症或孕妇死胎和流产有关。尽管进行了抗生素治疗，但由Lm感染引起的侵袭性疾病的死亡率范围为约20%至高达66%或更高，并且存活的个体通常患有使人衰弱的神经系统后遗症。迫切需要成功治疗Lm侵袭性感染的新的有效策略来限制疾病的严重程度和严重的感染后后遗症。此外，更广泛地了解的分子适应，使Lm从土壤腐殖土转变为病原体可能有助于更好地评估疾病的环境水库。这项建议的重点是破译如何一种新的细菌肽信息素为基础的信号系统，使土壤细菌过渡到生活在哺乳动物胞质溶胶。Lm土壤到胞质溶胶转变的核心是细菌感知其在受感染宿主细胞的空泡内的位置并表达促进空泡裂解和细菌逃逸到发生复制的胞质溶胶中的基因产物的能力。我们已经确定了一种细菌肽信息素，增强Lm逃离宿主液泡，这是所需的细菌在动物中的毒力。该R21建议的工作假设是pPplA肽信息素使Lm能够感知液泡的空间范围并诱导液泡逃逸和胞质复制所需的基因产物的表达。该提议将使用遗传、生物化学和体内方法的组合来功能性地破译pPplA肽信息素对细菌毒力的贡献。目的1将定义pPplA信号通路的表达模式和组分，目的2将确定pPplA增强细菌从宿主液泡逃逸的机制。这项提案的最终目标将是阐明促进Lm在宿主细胞内生存和将土壤居民转化为细胞入侵者的分子途径。

 DESCRIPTION (provided by applicant): Listeria monocytogenes (Lm) is a food-borne facultative intracellular bacterial pathogen that has been responsible for some of the deadliest contaminated food outbreaks in U.S. history. While disease in healthy individuals is usually limited to gastroenteritis, serious invasive disease occurs in susceptible populations that include immunocompromised individuals, pregnant women, neonates, and the elderly. Lm infections are commonly associated with meningitis, meningoencephalitis, brain abscesses, cardiac infections, septicemia, or stillbirth and abortion in pregnant women. Invasive disease resulting from Lm infection has a mortality rate that ranges from approximately 20% to up to 66% or higher despite antibiotic treatment, and surviving individuals often suffer from debilitating neurological sequelae. New effective strategies for successful treatment of Lm invasive infections are urgently needed to limit the severity of disease and the serious post-infection sequelae. In addition, a broader understanding of the molecular adaptations that enable Lm to transition from soil saprophyte to pathogen may facilitate better assessment of environmental reservoirs of disease. The focus of this proposal is on deciphering how a novel bacterial peptide pheromone-based signaling system enables a soil bacterium to transition into life within the mammalian cytosol. Central to the Lm soil-to-cytosol transition is the ability of the bacterium to sense its location within the vacuoles of infected host cells and express gene products that promote vacuole lysis and bacterial escape into the cytosol where replication occurs. We have identified a bacterial peptide pheromone that enhances Lm escape from host vacuoles and which is required for bacterial virulence in animals. The working hypothesis of this R21 proposal is that the pPplA peptide pheromone enables Lm to sense the spatial confines of the vacuole and induce the expression of gene products necessary for vacuole escape and cytosolic replication. This proposal will use a combination of genetic, biochemical, and in vivo approaches to functionally decipher the contributions of the pPplA peptide pheromone to bacterial virulence. Aim 1 will define the expression patterns and components of the pPplA signaling pathway, and Aim 2 will determine the mechanism by which pPplA enhances bacterial escape from host vacuoles. The ultimate goal of this proposal will be to elucidate the molecular pathways that promote Lm survival within host cells and the transformation of a soil dweller into a cell invader.