Carlsson Katrin E, Liu Junfa, Edqvist Petra J, Francis Matthew S
Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
Infect Immun. 2007 Sep;75(9):4386-99. doi: 10.1128/IAI.01450-06. Epub 2007 Jul 9.
The extracytoplasmic-stress-responsive CpxRA two-component signal transduction pathway allows bacteria to adapt to growth in extreme environments. It controls the production of periplasmic protein folding and degradation factors, which aids in the biogenesis of multicomponent virulence determinants that span the bacterial envelope. This is true of the Yersinia pseudotuberculosis Ysc-Yop type III secretion system. However, despite using a second-site suppressor mutation to restore Yop effector secretion by yersiniae defective in the CpxA sensor kinase, these bacteria poorly translocated Yops into target eukaryotic cells. Investigation of this phenotype herein revealed that the expression of genes which encode several surface-located adhesins is also influenced by the Cpx pathway. In particular, the expression and surface localization of invasin, an adhesin that engages beta1-integrins on the eukaryotic cell surface, are severely restricted by the removal of CpxA. This reduces bacterial association with eukaryotic cells, which could be suppressed by the ectopic production of CpxA, invasin, or RovA, a positive activator of inv expression. In turn, these infected eukaryotic cells then became susceptible to intoxication by translocated Yop effectors. In contrast, bacteria harboring an in-frame deletion of cpxR, which encodes the cognate response regulator, displayed an enhanced ability to interact with cell monolayers, as well as elevated inv and rovA transcription. This phenotype could be drastically suppressed by providing a wild-type copy of cpxR in trans. We propose a mechanism of inv regulation influenced by the direct negative effects of phosphorylated CpxR on inv and rovA transcription. In this fashion, sensing of extracytoplasmic stress by CpxAR contributes to productive Yersinia sp.-eukaryotic cell interactions.
胞外应激反应性CpxRA双组分信号转导途径使细菌能够适应在极端环境中生长。它控制周质蛋白折叠和降解因子的产生,这有助于跨越细菌包膜的多组分毒力决定簇的生物合成。耶尔森氏菌假结核耶尔森氏菌的Ysc-Yop III型分泌系统就是如此。然而,尽管使用了第二位点抑制突变来恢复CpxA传感器激酶缺陷的耶尔森氏菌的Yop效应器分泌,但这些细菌将Yops转运到靶真核细胞中的效率很低。本文对这种表型的研究表明,编码几种表面定位黏附素的基因表达也受Cpx途径影响。特别是,侵袭素(一种与真核细胞表面β1整合素结合的黏附素)的表达和表面定位因去除CpxA而受到严重限制。这减少了细菌与真核细胞的结合,而通过异位产生CpxA、侵袭素或Inv表达的正激活剂RovA可以抑制这种结合。反过来,这些被感染的真核细胞随后变得容易受到转运的Yop效应器的毒害。相反,携带编码同源反应调节因子CpxR的框内缺失的细菌与细胞单层相互作用的能力增强,同时Inv和RovA转录水平升高。通过反式提供野生型CpxR拷贝,这种表型可以被显著抑制。我们提出了一种由磷酸化CpxR对Inv和RovA转录的直接负面影响所影响的Inv调控机制。通过这种方式,CpxAR对胞外应激的感知有助于耶尔森氏菌与真核细胞的有效相互作用。