An Autotransporter Protein from Orientia tsutsugamushi Mediates Adherence to Nonphagocytic Host Cells
An Autotransporter Protein from Orientia tsutsugamushi Mediates Adherence to Nonphagocytic Host Cells
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DOI：
10.1128/iai.01239-10
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发表时间：
2011-04-01
影响因子：
3.1
通讯作者：
Kim, Ik-Sang
中科院分区：
文献类型：
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作者：
Ha, Na-Young;Cho, Nam-Hyuk;Kim, Ik-Sang
恙虫病东方体是一种细胞内专性病原体，其细胞黏附和侵袭机制尚不清楚。对两个恙虫病原虫基因组的生物信息学分析显示，存在一组编码自身转运蛋白的基因。在本研究中，我们鉴定了10个自体转运蛋白基因产物，并根据它们的序列相似性将它们分为五组(SCAA至SCAE)。SCAC组成员之间的序列同源性最高，表明细菌-宿主相互作用的功能保守。钩端螺旋体表面有SCAC的活性表达，并能诱导伤寒病人产生抗体反应。使用连接到重组SCAC或替代大肠杆菌表达系统的微球的实验表明，SCAC足以介导对非吞噬哺乳动物细胞的附着，但不能介导对其的侵袭。此外，用重组SCAC预孵育宿主细胞可显著抑制它们与恙虫病原虫的相互作用。最后，通过酵母双杂交筛选，纤维连接蛋白被鉴定为SCAC的潜在受体，并通过谷胱甘肽S转移酶下拉实验证实了这一点。综上所述，这些结果表明SCAC参与了恙虫病原虫与哺乳动物宿主细胞的相互作用，并提示SCAC可能在细菌致病中发挥关键作用。
Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular pathogen whose mechanism of cellular adhesion and invasion is poorly characterized. Bioinformatic analyses of two O. tsutsugamushi genomes revealed the presence of a group of genes that encode autotransporter proteins. In this study, we identified 10 autotransporter gene products and categorized them into five groups of orthologs (ScaA to ScaE) based on their sequence similarities. Sequence homology was highest between members of ScaC group, suggesting the functional conservation of bacterium-host interactions. ScaC was actively expressed on the surface of O. tsutsugamushi and induced antibody responses in scrub typhus patients. Experiments using microbeads conjugated to recombinant ScaC or a surrogate Escherichia coli expression system showed that ScaC was sufficient to mediate attachment to, but not invasion of, nonphagocytic mammalian cells. In addition, preincubation of host cells with recombinant ScaC significantly inhibited their interaction with O. tsutsugamushi. Finally, fibronectin was identified as a potential receptor for ScaC by using yeast two-hybrid screening, and this was confirmed using a glutathione S-transferase (GST) pulldown assay. Taken together, these results demonstrate that ScaC is involved in the interaction of O. tsutsugamushi with mammalian host cells and suggest that ScaC may play a critical role in bacterial pathogenesis.