Shandong Medicinal Biotechnology Center, Shandong Academy of Medical Sciences, Jinan, 250062, People's Republic of China.
State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100, People's Republic of China.
Curr Microbiol. 2018 Apr;75(4):401-409. doi: 10.1007/s00284-017-1394-8. Epub 2017 Nov 13.
Rv1057 is the only β-propeller protein in Mycobacterium tuberculosis, but its biological function is still unclear. In this study, we generated a deletion mutant of Rv1057 (D1057) in the virulent M. tuberculosis strain H37Rv and examined the characteristics of the mutant in vitro and in macrophages. We found that deletion of Rv1057 reduces secretion of the major virulence factor ESAT-6 and ESAT-6 stops in the cell envelope fraction during secretion, although ESAT-6 levels were similar in lysates of the mutant and control strains. In infected macrophages, Rv1057 deletion significantly reduced the secretion levels of cytokines IL-1β, IL-10, TNF-α, and INF-γ, but did not affect IL-4 and IL-8. D1057-infected macrophages also release less LDH and produce more nitric oxide (NO) than H37Rv- and D1057com (Rv1057 complemented strain of D1057com)-infected macrophages, indicating that D1057 has the decreased cytotoxicity compared to H37Rv or D1057com. In addition, the capacity of the Rv1057 deletion mutant to grow in macrophages was significantly lower than that of H37Rv and D1057com. Our findings support a role for Rv1057 in ESAT-6 secretion and in modulating the interactions between M. tuberculosis and macrophages.
Rv1057 是结核分枝杆菌中唯一的β-螺旋桨蛋白，但它的生物学功能仍不清楚。在本研究中，我们在毒力株 H37Rv 中构建了 Rv1057 的缺失突变体（D1057），并在体外和巨噬细胞中研究了突变体的特性。我们发现，Rv1057 的缺失减少了主要毒力因子 ESAT-6 的分泌，并且 ESAT-6 在分泌过程中停留在细胞包膜部分，尽管突变体和对照菌株的裂解物中 ESAT-6 水平相似。在感染的巨噬细胞中，Rv1057 的缺失显著降低了细胞因子 IL-1β、IL-10、TNF-α 和 INF-γ 的分泌水平，但不影响 IL-4 和 IL-8。与 H37Rv 和 D1057com（D1057 互补株）感染的巨噬细胞相比，D1057 感染的巨噬细胞释放的 LDH 更少，产生的一氧化氮（NO）更多，表明与 H37Rv 或 D1057com 相比，D1057 具有更低的细胞毒性。此外，Rv1057 缺失突变体在巨噬细胞中的生长能力明显低于 H37Rv 和 D1057com。我们的研究结果支持 Rv1057 在 ESAT-6 分泌和调节结核分枝杆菌与巨噬细胞相互作用中的作用。
