PrsW Is Required for Colonization, Resistance to Antimicrobial Peptides, and Expression of Extracytoplasmic Function σ Factors in Clostridium difficile
PrsW Is Required for Colonization, Resistance to Antimicrobial Peptides, and Expression of Extracytoplasmic Function σ Factors in Clostridium difficile
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DOI：
10.1128/iai.00019-11
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发表时间：
2011-08-01
影响因子：
3.1
通讯作者：
Ellermeier, Craig D.
中科院分区：
文献类型：
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作者：
Ho, Theresa D.;Ellermeier, Craig D.
艰难梭菌是一种厌氧，革兰氏阳性，孢子形成，机会性病原体，是医院获得性感染性腹泻的最常见原因。在许多病原体中，应激反应机制是在宿主内生存所必需的。胞质外功能因子（Extracytoplasmic function， ECF）是信号转导系统的一个主要家族，它感知并响应细胞外应激。我们已经确定了三个艰难梭菌ECF sigma因子。这些ECF sigma因子CsfT、CsfU和CsfV诱导自身表达，并分别受到其同源抗sigma因子RsiT、RsiU和RsiV的负调控。暴露于抗菌肽杆菌肽和/或溶菌酶后，这些ECF sigma因子的表达水平增加。许多ECF sigma因子的表达受位点1和位点2蛋白酶控制，这些蛋白酶可切割抗sigma因子。使用重靶向的II组内含子，我们在prsW（假定的1位点蛋白酶）中产生了艰难梭菌突变。艰难梭菌prsW突变体显示CsfT和CsfU的表达水平下降，但CsfV的表达水平没有下降。当在异源宿主中表达时，艰难梭菌PrsW能够诱导RsiT的降解，但不能诱导RsiU的降解。当在艰难梭菌感染仓鼠模型中对prsW突变体与其等基因亲本进行竞争试验时，我们发现prsW突变体的毒力比野生型低30倍。在体外竞争实验中，prsW突变体对杆菌肽和溶菌酶的敏感性也明显高于野生型。综上所述，这些数据表明，PrsW可能调节艰难梭菌ECF sigma因子CsfT的激活，并控制艰难梭菌对宿主生存至关重要的抗菌肽的耐药性。
Clostridium difficile is an anaerobic, Gram-positive, spore-forming, opportunistic pathogen that is the most common cause of hospital-acquired infectious diarrhea. In numerous pathogens, stress response mechanisms are required for survival within the host. Extracytoplasmic function (ECF) sigma factors are a major family of signal transduction systems, which sense and respond to extracellular stresses. We have identified three C. difficile ECF sigma factors. These ECF sigma factors, CsfT, CsfU, and CsfV, induce their own expressions and are negatively regulated by their cognate anti-sigma factors, RsiT, RsiU, and RsiV, respectively. The levels of expression of these ECF sigma factors increase following exposure to the antimicrobial peptides bacitracin and/or lysozyme. The expressions of many ECF sigma factors are controlled by site 1 and site 2 proteases, which cleave anti-sigma factors. Using a retargeted group II intron, we generated a C. difficile mutation in prsW, a putative site 1 protease. The C. difficile prsW mutant exhibited decreased levels of expression of CsfT and CsfU but not of CsfV. When expressed in a heterologous host, C. difficile PrsW was able to induce the degradation of RsiT but not of RsiU. When the prsW mutant was tested in competition assays against its isogenic parent in the hamster model of C. difficile infection, we found that the prsW mutant was 30-fold less virulent than the wild type. The prsW mutant was also significantly more sensitive to bacitracin and lysozyme than the wild type in in vitro competition assays. Taken together, these data suggest that PrsW likely regulates the activation of the ECF sigma factor CsfT in C. difficile and controls the resistance of C. difficile to antimicrobial peptides that are important for survival in the host.