A Novel ESX-1 Locus Reveals that Surface- Associated ESX-1 Substrates Mediate Virulence in Mycobacterium marinum
A Novel ESX-1 Locus Reveals that Surface- Associated ESX-1 Substrates Mediate Virulence in Mycobacterium marinum
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DOI：
10.1128/jb.01502-14
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发表时间：
2014-05-01
影响因子：
3.2
通讯作者：
Champion, Patricia A. DiGiuseppe
中科院分区：
文献类型：
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作者：
Kennedy, George M.;Hooley, Gwendolyn C.;Champion, Patricia A. DiGiuseppe
EsxA（ESAT-6）和EsxB（CFP-10）是分枝杆菌病原体中ESX-1系统输出的毒力因子。在结核分枝杆菌中ESX-1分泌的已建立模型海洋分枝杆菌中，ESX-1输出所需的基因位于差异延伸区1（RD 1）基因座。在本研究中，一个新的位点所需的ESX-1输出M。marinum在RD 1基因座外被鉴定。个核磁携带MMAR_1663和MMAR_1664基因之间的转座子插入的marinum菌株表现出光滑的菌落形态，缺乏ESX-1输出，是非溶血性的，并且毒力减弱。遗传互补揭示了细胞培养模型中菌落形态的恢复和毒力的部分恢复。然而，溶血和出口的ESX-1基板到细菌培养基中的体外免疫印迹和定量蛋白质组学测量没有恢复。我们发现，转座子插入菌株的遗传互补部分恢复了EsxA和EsxB易位到分枝杆菌细胞表面。我们的研究结果表明，出口的EsxA和EsxB的细胞表面，而不是分泌到细菌培养基中，与毒力在M。marinum。总之，这些发现不仅扩展了M中ESX-1分泌所需的已知遗传位点。marinum，但也提供了体外ESX-1输出和毒力之间观察到的差异的解释。
EsxA (ESAT-6) and EsxB (CFP-10) are virulence factors exported by the ESX-1 system in mycobacterial pathogens. In Mycobacterium marinum, an established model for ESX-1 secretion in Mycobacterium tuberculosis, genes required for ESX-1 export reside at the extended region of difference 1 (RD1) locus. In this study, a novel locus required for ESX-1 export in M. marinum was identified outside the RD1 locus. An M. marinum strain bearing a transposon-insertion between the MMAR_1663 and MMAR_1664 genes exhibited smooth-colony morphology, was deficient for ESX-1 export, was nonhemolytic, and was attenuated for virulence. Genetic complementation revealed a restoration of colony morphology and a partial restoration of virulence in cell culture models. Yet hemolysis and the export of ESX-1 substrates into the bacteriological medium in vitro as measured by both immunoblotting and quantitative proteomics were not restored. We show that genetic complementation of the transposon insertion strain partially restored the translocation of EsxA and EsxB to the mycobacterial cell surface. Our findings indicate that the export of EsxA and EsxB to the cell surface, rather than secretion into the bacteriological medium, correlates with virulence in M. marinum. Together, these findings not only expand the known genetic loci required for ESX-1 secretion in M. marinum but also provide an explanation for the observed disparity between in vitro ESX-1 export and virulence.