Four VirB6 Paralogs and VirB9 Are Expressed and Interact in Ehrlichia chaffeensis-Containing Vacuoles
Four VirB6 Paralogs and VirB9 Are Expressed and Interact in Ehrlichia chaffeensis-Containing Vacuoles
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DOI：
10.1128/jb.01031-08
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发表时间：
2009-01-01
影响因子：
3.2
通讯作者：
Rikihisa, Yasuko
中科院分区：
文献类型：
--
作者：
Bao, Weichao;Kumagai, Yumi;Rikihisa, Yasuko
IV型分泌系统是几种宿主细胞相关病原体中的重要毒力因子，因为它将各种细菌大分子递送至靶真核细胞。在液泡内病原体查菲埃里希体（Ehrlichia chaffeensis）中发现了与根癌农杆菌的几个virB基因和virD 4同源的基因，查菲埃里希体是人类单核细胞埃里希体病的蜱传病原体。特别是，尽管其基因组大小很小，E. chaffeensis有四个串联的virB 6旁系同源物（virB 6 -1、-2、-3和-4），它们比A大3- 10倍。根瘤菌virB 6.本研究首次阐明了较大的四重VirB 6旁系同源物在大肠杆菌中的蛋白表达和相互作用。chaffeensis。所有四种virB 6旁系同源物在THP-1人白血病和ISE 6蜱细胞培养物中共转录。在大肠杆菌中表达了4种VirB 6蛋白和VirB 9蛋白。Chaffeensis在THP-1细胞中的表达量与分离的E.含chaffeensis的液泡和无液泡E. chaffeensis。此外，还检测到一个80-kDa的VirB 6 -2片段，该片段在大肠杆菌中明显更普遍。含chaffeensis的液泡比无液泡E. chaffeensis。免疫共沉淀分析显示VirB 9与VirB 6 -1和VirB 6 -2相互作用; VirB 6 -4与VirB 6 -1、VirB 6 -2和VirB 6 -3相互作用; VirB 6 -2 80-kDa片段与VirB 6 -3和VirB 6 -4相互作用。通过far-Western blotting证实了VirB 9和VirB 6 -2的相互作用。结果表明，E. chaffeensis VirB 9、四重VirB 6蛋白和VirB 6 -2 80-kDa片段形成独特的分子亚组以在IV型分泌中协作。
The type IV secretion system is an important virulence factor in several host cell-associated pathogens, as it delivers various bacterial macromolecules to target eukaryotic cells. Genes homologous to several virB genes and virD4 of Agrobacterium tumefaciens are found in an intravacuolar pathogen Ehrlichia chaffeensis, the tick-borne causative agent of human monocytic ehrlichiosis. In particular, despite its small genome size, E. chaffeensis has four tandem virB6 paralogs (virB6-1, -2, -3, and -4) that are 3- to 10-fold larger than A. tumefaciens virB6. The present study for the first time illustrates the relevance of the larger quadruple VirB6 paralogs by demonstrating the protein expression and interaction in E. chaffeensis. All four virB6 paralogs were cotranscribed in THP-1 human leukemia and ISE6 tick cell cultures. The four VirB6 proteins and VirB9 were expressed by E. chaffeensis in THP-1 cells, and amounts of these five proteins were similar in isolated E. chaffeensis-containing vacuoles and vacuole-free E. chaffeensis. In addition, an 80-kDa fragment of VirB6-2 was detected, which was strikingly more prevalent in E. chaffeensis-containing vacuoles than in vacuole-free E. chaffeensis. Coimmunoprecipitation analysis revealed VirB9 interaction with VirB6-1 and VirB6-2; VirB6-4 interaction with VirB6-1, VirB6-2, and VirB6-3; and VirB6-2 80-kDa fragment interaction with VirB6-3 and VirB6-4. The interaction of VirB9 and VirB6-2 was confirmed by far-Western blotting. The results suggest that E. chaffeensis VirB9, the quadruple VirB6 proteins, and the VirB6-2 80-kDa fragment form a unique molecular subassembly to cooperate in type IV secretion.