Table7.XLS

Leptospirosis is an emerging zoonotic disease with more than 1 million cases annually. Currently there is lack of evidence for signaling pathways involved during the infection process of Leptospira. In our comprehensive genomic analysis of 20 Leptospira spp. we identified seven pathogen-specific Two-Component System (TCS) proteins. Disruption of two these TCS genes in pathogenic Leptospira strain resulted in loss-of-virulence in a hamster model of leptospirosis. Corresponding genes lvrA and lvrB (leptospira virulence regulator) are juxtaposed in an operon and are predicted to encode a hybrid histidine kinase and a hybrid response regulator, respectively. Transcriptome analysis of lvr mutant strains with disruption of one (lvrB) or both genes (lvrA/B) revealed global transcriptional regulation of 850 differentially expressed genes. Phosphotransfer assays demonstrated that LvrA phosphorylates LvrB and predicted further signaling downstream to one or more DNA-binding response regulators, suggesting that it is a branched pathway. Phylogenetic analyses indicated that lvrA and lvrB evolved independently within different ecological lineages in Leptospira via gene duplication. This study uncovers a novel-signaling pathway that regulates virulence in pathogenic Leptospira (Lvr), providing a framework to understand the molecular bases of regulation in this life-threatening bacterium.

钩端螺旋体病（Leptospirosis）是一种新发人畜共患病，每年报告病例超100万例。目前学界对钩端螺旋体感染过程中涉及的信号通路仍缺乏充分研究证据。本研究对20种钩端螺旋体属（Leptospira spp.）菌株开展全面基因组分析，共鉴定出7种病原体特异性双组分系统（Two-Component System, TCS）蛋白。在致病性钩端螺旋体菌株中敲除其中2个TCS编码基因后，该菌株在钩端螺旋体病仓鼠感染模型中表现出毒力丧失表型。对应的基因lvrA与lvrB（钩端螺旋体毒力调节因子，leptospira virulence regulator）串联排布于同一操纵子中，分别编码杂合组氨酸激酶与杂合响应调节蛋白。对仅敲除lvrB或同时敲除lvrA、lvrB的突变菌株进行转录组分析，结果显示共有850个差异表达基因受到全局性转录调控。磷酸转移实验证实，LvrA可对LvrB进行磷酸化，并可进一步向下游的一个或多个DNA结合型响应调节蛋白传递信号，提示该通路为分支型信号通路。系统发育分析表明，lvrA与lvrB通过基因重复事件，在钩端螺旋体不同生态谱系中独立演化而来。本研究揭示了一条调控致病性钩端螺旋体毒力的全新信号通路（Lvr通路），为阐明这种致命细菌的调控分子机制提供了研究框架。