Effect of rickettsial toxin VapC on its eukaryotic host.
Effect of rickettsial toxin VapC on its eukaryotic host.
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DOI：
10.1371/journal.pone.0026528
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Raoult D
中科院分区：
文献类型：
--
作者：
Audoly G;Vincentelli R;Edouard S;Georgiades K;Mediannikov O;Gimenez G;Socolovschi C;Mège JL;Cambillau C;Raoult D
立克次体是细胞内细菌，通常与节肢动物有关，可通过感染媒介传播给人类。立克次体可引起轻微至严重的人类疾病，当开始抗生素治疗时，皮质类固醇可能起保护作用。我们在几个立克次体基因组中鉴定了横向转移的毒素-抗毒素（TA）遗传元件，包括vapB/C，并表明它们在细菌和真核细胞中起作用。我们还建立了一种斑块测定法来监测随时间推移溶解斑块的形成，并证明氯霉素加速宿主细胞裂解含有vapB/ c的立克次体。暴露于抗生素后，感染细胞的全基因组表达、TUNEL和FISH检测显示宿主细胞早期凋亡，这与细菌vapB/C操纵子的过度转录和随后的细胞质VapC毒素释放有关。在大肠杆菌和酿酒酵母中表达或微注射到哺乳动物细胞中的VapC通过RNase活性产生毒性，地塞米松可以阻止其产生毒性。本研究首次提供了毒素-抗毒素成分在细菌宿主细胞中作为致病因子的生物学证据，证实了它们在细菌致病性中的作用的比较基因组证据。我们的研究结果表明，一些细菌感染的抗生素治疗后的早期死亡可以通过地塞米松的管理来预防。
Rickettsia are intracellular bacteria typically associated with arthropods that can be transmitted to humans by infected vectors. Rickettsia spp. can cause mild to severe human disease with a possible protection effect of corticosteroids when antibiotic treatments are initiated. We identified laterally transferred toxin-antitoxin (TA) genetic elements, including vapB/C, in several Rickettsia genomes and showed that they are functional in bacteria and eukaryotic cells. We also generated a plaque assay to monitor the formation of lytic plaques over time and demonstrated that chloramphenicol accelerates host cell lysis of vapB/C-containing Rickettsia. Whole-genome expression, TUNEL and FISH assays on the infected cells following exposure to the antibiotic revealed early apoptosis of host cells, which was linked to over-transcription of bacterial vapB/C operons and subsequent cytoplasmic VapC toxin release. VapC that is expressed in Escherichia coli and Saccharomyces cerevisiae or microinjected into mammalian cells is toxic through RNase activity and is prevented by dexamethasone. This study provides the first biological evidence that toxin–antitoxin elements act as pathogenic factors in bacterial host cells, confirming comparative genomic evidence of their role in bacterial pathogenicity. Our results suggest that early mortality following antibiotic treatment of some bacterial infections can be prevented by administration of dexamethasone.