RmpA, a unique virulence regulator in emerging Klebsiella pneumoniae

描述(申请人提供)：肠杆菌科包括一系列人类、动物和植物病原体。人类肠道和肠道外感染是由密切相关的埃希氏菌、志贺氏菌、沙门氏菌和克雷伯氏菌的特定菌株引起的。虽然研究相对较少，但肺炎克雷伯菌是一种臭名昭著的医院病原体，导致抗生素耐药性的广泛传播。最近，肺炎克雷伯菌被确认为一种新出现的社区获得性化脓性肝感染的病因，称为KLA(肺炎克雷伯菌肝脓肿)。这种感染是由于表达HMV(高粘滞性)表型的特定克隆所致，这种表型是由于对胶囊成分或合成的未知修改造成的。衣壳是肺炎克雷伯菌感染所必需的致病因子，而HMV对KLA菌株的毒力起重要作用。HMV的表型取决于辅助调节因子RmpA，这是一种独特的蛋白质，可能与全球RCSB反应调节因子形成异二聚体。特征菌株在移动遗传元件上含有多个rmpA等位基因。与NIAID的相关性和该项目的长期目标是识别和了解肺炎克雷伯菌致病性和毒力的遗传决定因素。这项建议的目标是启动对肺炎克雷伯菌毒力株KLA的遗传和生化分析。本研究旨在确定RmpA及其相互作用调节因子在控制毒力因子(包括衣壳和HMV表型)中的功能。这项研究将与KLA研究的领先者、国立台湾大学医学院的王金镇教授合作进行。特定的AIMS将应用各种体内和体外方法来检验五个假说：(1a)重复的rmpA等位基因至少部分冗余；(1b)RmpA整合到RCSB调控网络中；(2)RmpA调控子包括那些直接参与囊膜合成和组装的毒力基因；(3a)RCSB-RmpA异源二聚体控制囊膜生物合成操纵子的表达；以及(3b)RmpA活性受磷酸化调节。拟议研究的影响包括：(I)鉴定和分析一种因产生抗生素耐药性而臭名昭著的新病原体的毒力因素；(Ii)提高对HMV独特表型及其受RmpA调节子控制的理解；以及(Iii)修改关于RCSB全球调控网络与辅助调节器相互作用的概念。 公共卫生相关性：肺炎克雷伯氏菌是一种臭名昭著的医院病原体，最近在其他健康的成年人中出现为化脓性肝脓肿的原因。高粘性囊膜是细胞表面的一层保护层，在这种病理过程中很重要。这项研究的公共卫生意义在于了解一种控制高粘性囊膜形成和成分的独特调节剂。

DESCRIPTION (provided by applicant): The family Enterobacteriaceae includes an array of human, animal and plant pathogens. Human intestinal and extraintestinal infections are caused by specific strains of the closely-related species Escherichia, Shigella, Salmonella and Klebsiella. Although relatively little-studied, Klebsiella pneumoniae nevertheless is a notorious nosocomial pathogen responsible for widespread dissemination of antibiotic resistance. Recently, K. pneumoniae has been identified as the cause of an emerging community-acquired pyogenic liver infection termed KLA (K. pneumoniae liver abscess). This infection is due to specific clones expressing the Hmv (hypermucoviscosity) phenotype, which results from unknown modifications of capsule composition or synthesis. Capsule is an essential pathogenicity factor for K. pneumoniae infections, and Hmv is important for virulence of KLA strains. The Hmv phenotype depends on the auxiliary regulator RmpA, a unique protein that likely forms heterodimers with the global RcsB response regulator. Characterized strains contain multiple rmpA alleles on mobile genetic elements. The relevance to NIAID, and the long-term objectives for this project, are to identify and understand genetic determinants for K. pneumoniae pathogenicity and virulence. The goal of this proposal is to initiate genetic and biochemical analysis in a virulent KLA strain of K. pneumoniae. Studies are designed to identify the functions of RmpA and interacting regulators in the control of virulence factors including capsule and the Hmv phenotype. Research will be in collaboration with a leader in the study of KLA, Prof. Jin-Town Wang at the National Taiwan University College of Medicine. Specific aims will apply a variety of in vivo and in vitro approaches to test five hypotheses: (1a) Duplicate rmpA alleles are at least partially redundant; (1b) RmpA is integrated into the RcsB regulatory network; (2) The RmpA regulon includes virulence genes beyond those involved directly in capsule synthesis and assembly; (3a) RcsB-RmpA heterodimers control capsule biosynthetic operon expression; and (3b) RmpA activity is modulated by phosphorylation. Impacts of the proposed research are: (i) identification and analysis of virulence factors in an emerging pathogen notorious for developing antibiotic resistance; (ii) improved understanding of the unique Hmv phenotype and its control by the RmpA regulon; and (iii) modified concepts regarding global RcsB regulatory network interactions with auxiliary regulators. PUBLIC HEALTH RELEVANCE: Klebsiella pneumoniae, a notorious nosocomial pathogen, has emerged recently as the cause of pyogenic liver abscess in otherwise healthy adults. Hypermucoviscous capsule, a protective layer surrounding the cell surface, is important for this pathology. The public health relevance of this research is to understand a unique regulator that controls hypermucoviscous capsule formation and composition.