Codependent and Independent Effects of Nitric Oxide-Mediated Suppression of PhoPQ and Salmonella Pathogenicity Island 2 on Intracellular Salmonella enterica Serovar Typhimurium Survival
Codependent and Independent Effects of Nitric Oxide-Mediated Suppression of PhoPQ and Salmonella Pathogenicity Island 2 on Intracellular Salmonella enterica Serovar Typhimurium Survival
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DOI：
10.1128/iai.00759-09
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发表时间：
2009-11-01
影响因子：
3.1
通讯作者：
Vazquez-Torres, Andres
中科院分区：
文献类型：
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作者：
Bourret, Travis J.;Song, Miryoung;Vazquez-Torres, Andres
本研究表明，在单核吞噬细胞的先天反应中，肠沙门氏菌血清型鼠伤寒沙门氏菌PhoQ传感器激酶可降低由诱导型一氧化氮合酶（iNOS）产生的活性氮（RNS）的细胞毒性。这一观察结果与先天宿主反应中php激活基因在中度亚硝化应激中的表达模式一致。相反，γ干扰素（ifn - γ）激活的巨噬细胞在高no通量下合成的RNS抑制了phoP激活的lpxO、pagP和phoP基因转录。由于phop调控的沙门氏菌致病性岛2 （SPI2）基因也受到高阶RNS的抑制（39），我们研究了no介导的PhoPQ抑制是否为SPI2抑制的基础。我们的研究表明，在非活化的巨噬细胞中记录的SPI2 spiC基因表达的三分之一依赖于PhoQ。无论细菌的phoQ状态如何，ifn - γ引发的巨噬细胞中spiC的转录都以inos依赖的方式受到抑制。在ifn - γ处理的、缺乏inos的巨噬细胞中，spiC的转录恢复到非活化吞噬细胞中phoQ突变所维持的水平，这表明大多数no依赖性的spiC抑制是由于抑制了phopq非依赖性靶点。通过比较spiC、phoQ和spiC phoQ突变体的细胞内适应度，发现PhoPQ和SPI2对鼠伤寒沙门氏菌在先天亚硝化胁迫下的存活具有相互依赖和独立的影响。然而，大多数鼠伤寒沙门氏菌的细胞内存活是由PhoPQ双组分调节因子赋予的，并且SPI2 III型分泌系统被ifn - γ激活的巨噬细胞的高阶RNS抑制。
Here we show that the Salmonella enterica serovar Typhimurium PhoQ sensor kinase lessens the cytotoxicity of reactive nitrogen species (RNS) generated by inducible nitric oxide synthase (iNOS) in the innate response of mononuclear phagocytic cells. This observation is consistent with the expression patterns of PhoP-activated genes during moderate nitrosative stress in the innate host response. In contrast, RNS synthesized during high-NO fluxes of gamma interferon (IFN-gamma)-activated macrophages repress PhoP-activated lpxO, pagP, and phoP gene transcription. Because PhoP-regulated Salmonella pathogenicity island 2 (SPI2) genes are also repressed by high-order RNS (39), we investigated whether the NO-mediated inhibition of PhoPQ underlies the repression of SPI2. Our studies indicate that a third of the expression of the SPI2 spiC gene recorded in nonactivated macrophages depends on PhoQ. Transcription of spiC is repressed in IFN-gamma-primed macrophages in an iNOS-dependent manner, irrespective of the phoQ status of the bacteria. Transcription of spiC is restored in IFN-gamma-treated, iNOS-deficient macrophages to levels sustained by a phoQ mutant in nonactivated phagocytes, suggesting that most NO-dependent repression of spiC is due to the inhibition of PhoPQ-independent targets. Comparison of the intracellular fitness of spiC, phoQ, and spiC phoQ mutants revealed that PhoPQ and SPI2 have codependent and independent effects on S. Typhimurium survival during innate nitrosative stress. However, the intracellular survival of most S. Typhimurium bacteria is conferred by the PhoPQ two-component regulator, and the SPI2 type III secretion system is repressed by high-order RNS of IFN-gamma-activated macrophages.