Deciphering how bacterial pheromone signaling enhances Listeria virulence

 描述(申请人提供)：单核细胞增生性李斯特菌(Lm)是一种食源性兼性细胞内细菌病原体，是美国历史上一些最致命的受污染食品疫情的罪魁祸首。虽然健康人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 免疫功能受损的个人、孕妇、新生儿和老年人。在孕妇中，LM感染通常与脑膜炎、脑膜脑炎、脑脓肿、心脏感染、败血症或死产和流产有关。尽管接受抗生素治疗，但由LM感染引起的侵袭性疾病的死亡率从大约20%到高达66%或更高，存活的人通常会遭受衰弱的神经后遗症。迫切需要新的有效策略来成功治疗LM侵袭性感染，以限制疾病的严重程度和严重的感染后后遗症。此外，更广泛地了解使土壤腐生菌转变为病原菌的分子适应，可能有助于更好地评估环境中的疾病宿主。这项提议的重点是破译一种新的基于细菌多肽信息素的信号系统如何使土壤细菌能够过渡到哺乳动物细胞质中的生命。LM土壤到细胞质转变的核心是细菌能够感觉到自己在受感染宿主细胞的空泡中的位置，并表达促进空泡溶解和细菌逃逸到发生复制的细胞质中的基因产物。我们已经确定了一种细菌多肽信息素，它可以增强细菌从宿主空泡中逃逸，这是动物体内细菌毒力所必需的。这一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界限，并诱导液泡逃逸和细胞质复制所必需的基因产物的表达。这项建议将使用遗传、生化和体内方法的组合来从功能上破译pPplA肽信息素对细菌毒力的贡献。目标1将定义pPplA信号通路的表达模式和成分，目标2将确定pPplA增强细菌从宿主空泡中逃逸的机制。这项提议的最终目标将是阐明促进LM在宿主细胞内存活的分子途径，以及土壤中的居民转变为细胞入侵者。

 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.