Signal pathway in salt-activated expression of the Salmonella pathogenicity island 1 type III secretion system in Salmonella enterica serovar typhimurium
Signal pathway in salt-activated expression of the Salmonella pathogenicity island 1 type III secretion system in Salmonella enterica serovar typhimurium
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DOI：
10.1128/jb.01957-07
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Aizawa, Shin-Ichi
中科院分区：
文献类型：
--
作者：
Mizusaki, Hideaki;Takaya, Akiko;Aizawa, Shin-Ichi
鼠伤寒沙门氏菌通过III型分泌系统（T3 SS）分泌称为Sip蛋白或Sips的入侵毒力因子进入其宿主。在没有寄主的情况下，S. enterica诱导响应蔗糖或简单盐如NaCl的Sip分泌。我们通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）监测蛋白质分泌，通过电子显微镜组装针状复合物，并通过定量逆转录酶PCR（实时PCR）转录毒力调节基因，分析了诱导宿主非依赖性Sip分泌。SDS-PAGE显示，添加蔗糖或简单的盐，如NaCl，生长培养基诱导Sip分泌，而不改变鞭毛蛋白的分泌，这需要一个独特的T3 SS。电子显微镜证实，分泌的Sips的量增加组装针复合物的数量增加。实时PCR显示，添加蔗糖或NaCl增强了hiLA、hilC和hilD的转录，这些基因编码沙门氏菌毒力的已知调节因子。然而，上位性分析牵连HilD和HilA，但不是HilC，在直接途径从盐刺激的Sip分泌反应。进一步的分析表明，BarA/SirA双组分信号转导途径，而不是双组分传感器激酶EnvZ，直接激活hilD和hilA转录，从而响应蔗糖或NaCl的Sip分泌。最后，实时PCR显示盐不影响BarA/SirA依赖的csrB和csrC基因的转录。提出了一个模型的主要途径，其中蔗糖或盐信号，以提高毒力基因的表达。
Salmonella enterica serovar Typhimurium secretes virulence factors for invasion called Sip proteins or Sips into its hosts through a type III secretion system (T3SS). In the absence of a host, S. enterica induces Sip secretion in response to sucrose or simple salts, such as NaCl. We analyzed induction of host-independent Sip secretion by monitoring protein secretion by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), assembly of needle complexes by electron microscopy, and transcription of virulence regulatory genes by quantitative reverse transcriptase PCR (real-time PCR). SDS-PAGE showed that addition of sucrose or simple salts, such as NaCl, to the growth medium induced Sip secretion without altering flagellar protein secretion, which requires a distinct T3SS. Electron microscopy confirmed that the amount of secreted Sips increased as the number of assembled needle complexes increased. Real-time PCR revealed that added sucrose or NaCl enhanced transcription of hiLA, hilC, and hilD, which encode known regulators of Salmonella virulence. However, epistasis analysis implicated HilD and HilA, but not HilC, in the direct pathway from the salt stimulus to the Sip secretion response. Further analyses showed that the BarA/SirA two-component signal transduction pathway, but not the two-component sensor kinase EnvZ, directly activated hilD and hilA transcription and thus Sip secretion in response to either sucrose or NaCl. Finally, real-time PCR showed that salt does not influence transcription of the BarA/SirA-dependent csrB and csrC genes. A model is proposed for the major pathway in which sucrose or salt signals to enhance virulence gene expression.