MprAB Regulates the espA Operon in Mycobacterium tuberculosis and Modulates ESX-1 Function and Host Cytokine Response
MprAB Regulates the espA Operon in Mycobacterium tuberculosis and Modulates ESX-1 Function and Host Cytokine Response
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MprAB 调节结核分枝杆菌中的 espA 操纵子并调节 ESX-1 功能和宿主细胞因子反应
DOI：
10.1128/jb.01067-12
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发表时间：
2013-01-01
影响因子：
3.2
通讯作者：
Howard, Susan T.
中科院分区：
文献类型：
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作者：
Pang, Xiuhua;Samten, Buka;Howard, Susan T.
ESX-1分泌系统输出免疫调节蛋白ESAT-6和其他在结核分枝杆菌发病机制中重要的蛋白质。ESX-1的组分和底物在几个位点编码，但编码基因的调控仅部分了解。在这项研究中，我们研究了MprAB双组分系统在调节ESX-1活性中的作用。我们确定MprAB直接调节espA基因簇，这是ESX-1功能所必需的位点。转录定位确定簇中的五个基因形成具有两个转录起始点的操纵子，并且在espA启动子中检测到几个MprA结合位点。表达分析和启动子构建表明，MprAB抑制espA操纵子。然而，与对照菌株相比，MprAB突变体Rv-D981分泌更低水平的EspA、ESAT-6和ESX-1底物EspB。在Rv-D981和对照菌株中，通常与ESAT-6共分泌的CFP 10的分泌相似，进一步证明突变体中的异常ESX-1活性。ESAT-6诱导促炎细胞因子，并且用Rv-D981感染的巨噬细胞引起较低水平的白细胞介素1β（IL-1β）和肿瘤坏死因子α（TNF-α），这与ESAT-6水平降低一致。这些发现表明，MprAB调节ESX-1功能，并揭示了MprAB在宿主-病原体相互作用中的新作用。
ABSTRACT The ESX-1 secretion system exports the immunomodulatory protein ESAT-6 and other proteins important in the pathogenesis of Mycobacterium tuberculosis. Components and substrates of ESX-1 are encoded at several loci, but the regulation of the encoding genes is only partially understood. In this study, we investigated the role of the MprAB two-component system in the regulation of ESX-1 activity. We determined that MprAB directly regulates the espA gene cluster, a locus necessary for ESX-1 function. Transcript mapping determined that the five genes in the cluster form an operon with two transcriptional start points, and several MprA binding sites were detected in the espA promoter. Expression analyses and promoter constructs indicated that MprAB represses the espA operon. However, the MprAB mutant Rv-D981 secreted lower levels of EspA, ESAT-6, and the ESX-1 substrate EspB than control strains. Secretion of CFP10, which is normally cosecreted with ESAT-6, was similar in Rv-D981 and control strains, further demonstrating aberrant ESX-1 activity in the mutant. ESAT-6 induces proinflammatory cytokines, and macrophages infected with Rv-D981 elicited lower levels of interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α), consistent with the reduced levels of ESAT-6. These findings indicate that MprAB modulates ESX-1 function and reveal a new role for MprAB in host-pathogen interactions.