Oxidative stress response genes in Mycobacterium tuberculosis:: role of ahpC in resistance to peroxynitrite and stage-specific survival in macrophages
Oxidative stress response genes in Mycobacterium tuberculosis:: role of ahpC in resistance to peroxynitrite and stage-specific survival in macrophages
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DOI：
10.1099/00221287-148-10-3139
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发表时间：
2002-10-01
期刊：
影响因子：
2.8
通讯作者：
Timmins, GS
中科院分区：
文献类型：
--
作者：
Master, SS;Springer, B;Timmins, GS
结核分枝杆菌ahpC基因编码分枝杆菌烷基过氧化氢还原酶的同源基因，经历了一个不寻常的调控周期。AhpC的水平在作为曝气培养物生长的毒力菌株中的表达沉默阶段和静态杆菌中的表达激活阶段之间交替变化，这些阶段的表达沉默是由于所有结核杆菌菌株的调节加氧酶功能的自然丧失，而在静止的杆菌中的表达激活的机制尚不明确。目前尚不清楚这种控制抗氧化因子表达的非正统调控周期的原因。在这项工作中，结核分枝杆菌H37Rv和耻垢分枝杆菌MC(2)155ahpC基因敲除突变株对活性氮中间体，特别是活性氮和氧的高活性组合产物过氧亚硝酸盐的敏感性，以及对静止和激活的巨噬细胞杀菌机制的敏感性进行了测试。结核分枝杆菌ahpC：：Km(R)和污垢分枝杆菌ahpC：：Km(R)均表现出对过氧亚硝酸盐的敏感性增加。相比之下，结核分枝杆菌中ahpC的失活并不会单独导致对NO供体的敏感性增加。结核分枝杆菌ahpC：：Km(R)在未经刺激的巨噬细胞中也显示出存活率降低，但在IFNGamma激活时不再检测到这种影响。这些研究确定了ahpC在涉及过亚硝酸根的抗氧化防御中的特定作用，以及巨噬细胞中最可能的额外杀灭机制，调节周期可能有助于在休眠期间走出静止阶段(潜伏感染)或在传播到新宿主时存活。
The Mycobacterium tuberculosis ahpC gene, encoding the mycobacterial orthologue of alkylhydroperoxide reductase, undergoes an unusual regulatory cycle. The levels of AhpC alternate between stages of expression silencing in virulent strains grown as aerated cultures, secondary to a natural loss of the regulatory oxyR function in all strains of the tubercle bacillus, and expression activation in static bacilli by a yet undefined mechanism. The reasons for this unorthodox regulatory cycle controlling expression of an antioxidant factor are currently not known. In this work, M. tuberculosis H37Rv and Mycobacterium smegmatis mc(2)155 ahpC knockout mutants were tested for sensitivity to reactive nitrogen intermediates, in particular peroxynitrite, a highly reactive combinatorial product of reactive nitrogen and oxygen species, and sensitivity to bactericidal mechanisms in resting and activated macrophages. Both M. tuberculosis ahpC::Km(r) and M. smegmatis ahpC:: Km(r) showed increased susceptibility to peroxynitrite. In contrast, inactivation of ahpC in M. tuberculosis did not cause increased sensitivity to donors of NO alone. M. tuberculosis ahpC:: Km(r) also showed decreased survival in unstimulated macrophages, but the effect was no longer detectable upon IFNgamma activation. These studies establish a specific role for ahpC in antioxidant defences involving peroxynitrite and most likely additional cidal mechanisms in macrophages, with the regulatory cycle likely contributing to survival upon coming out of the stationary phase during dormancy (latent infection) or upon transmission to a new host.