Hoo Regina, Lam Jian Hang, Huot Ludovic, Pant Aakanksha, Li Rui, Hot David, Alonso Sylvie
Department of Microbiology, Immunology Programme, Yong Loo Lin School of Medicine, National University of Singapore, Centre for Life Science #03-05, 28 Medical Drive, Singapore 117597, Singapore.
Transcriptomics and Applied Genomics, Institut Pasteur de Lille, Centre for Infection and Immunity of Lille (CIIL), U1019, UMR8204, 1 rue du Professeur Calmette, F-59019 Lille, France.
PLoS One. 2014 Dec 12;9(12):e115243. doi: 10.1371/journal.pone.0115243. eCollection 2014.
Polysaccharide (PS) capsules are important virulence determinants for many bacterial pathogens. Bordetella pertussis, the agent of whooping cough, produces a surface associated microcapsule but its role in pertussis pathogenesis remained unknown. Here we showed that the B. pertussis capsule locus is expressed in vivo in murine lungs and that absence of the membrane-associated protein KpsT, involved in the transport of the PS polymers across the envelope, but not the surface-exposed PS capsule itself, affects drastically B. pertussis colonization efficacy in mice. Microarray analysis revealed that absence of KpsT in B. pertussis resulted in global down-regulation of gene expression including key virulence genes regulated by BvgA/S, the master two-component system. Using a BvgS phase-locked mutant, we demonstrated a functional link between KpsT and BvgA/S-mediated signal transduction. Whereas pull-down assays do not support physical interaction between BvgS sensor and any of the capsule locus encoded proteins, absence of KpsT impaired BvgS oligomerization, necessary for BvgS function. Furthermore, complementation studies indicated that instead of KpsT alone, the entire PS capsule transport machinery spanning the cell envelope likely plays a role in BvgS-mediated signal transduction. Our work thus provides the first experimental evidence of a role for a virulence-repressed gene in pertussis pathogenesis.
多糖（PS）荚膜是许多细菌病原体重要的毒力决定因素。百日咳博德特氏菌是百日咳的病原体，可产生一种与表面相关的微荚膜，但其在百日咳发病机制中的作用尚不清楚。在此，我们发现百日咳博德特氏菌的荚膜基因座在小鼠肺部的体内环境中表达，并且参与PS聚合物跨包膜转运的膜相关蛋白KpsT的缺失，而非表面暴露的PS荚膜本身的缺失，会极大地影响百日咳博德特氏菌在小鼠体内的定殖效率。微阵列分析显示，百日咳博德特氏菌中KpsT的缺失导致包括由主要双组分系统BvgA/S调控的关键毒力基因在内的基因表达全面下调。利用BvgS锁相突变体，我们证明了KpsT与BvgA/S介导的信号转导之间存在功能联系。虽然下拉实验不支持BvgS传感器与任何荚膜基因座编码蛋白之间存在物理相互作用，但KpsT的缺失会损害BvgS寡聚化，而这是BvgS发挥功能所必需的。此外，互补研究表明，跨越细胞膜的整个PS荚膜转运机制而非单独的KpsT可能在BvgS介导的信号转导中发挥作用。因此，我们的工作首次提供了实验证据，证明一个毒力抑制基因在百日咳发病机制中发挥作用。
