Division of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Massasoit Community College, Brockton, Massachusetts, USA.
Infect Immun. 2015 Nov;83(11):4362-72. doi: 10.1128/IAI.00723-15. Epub 2015 Aug 31.
We previously identified the protein Tet38 as a chromosomally encoded efflux pump of Staphylococcus aureus that confers resistance to tetracycline and certain unsaturated fatty acids. Tet38 also contributes to mouse skin colonization. In this study, we discovered a novel regulator of tet38, named tetracycline regulator 21 (TetR21), that bound specifically to the tet38 promoter and repressed pump expression. A ΔtetR21 mutant showed a 5-fold increase in tet38 transcripts and an 8-fold increase in resistance to tetracycline and fatty acids. The global regulator MgrA bound to the tetR21 promoter and indirectly repressed the expression of tet38. To further assess the full role of Tet38 in S. aureus adaptability, we tested its effect on host cell invasion using A549 (lung) and HMEC-1 (heart) cell lines. We used S. aureus RN6390, its Δtet38, ΔtetR21, and ΔmgrA mutants, and a Δtet38 ΔtetR21 double mutant. After 2 h of contact, the Δtet38 mutant was internalized in 6-fold-lower numbers than RN6390 in A549 and HMEC-1 cells, and the ΔtetR21 mutant was internalized in 2-fold-higher numbers than RN6390. A slight increase of 1.5-fold in internalization was found for the ΔmgrA mutant. The growth patterns of RN6390 and the ΔmgrA and ΔtetR21 mutants within A549 cells were similar, while no growth was observed for the Δtet38 mutant. These data indicate that the Tet38 efflux pump is regulated by TetR21 and contributes to the ability of S. aureus to internalize and replicate within epithelial cells.
我们之前发现蛋白质 Tet38 是金黄色葡萄球菌中一种染色体编码的外排泵，它赋予了金黄色葡萄球菌对四环素和某些不饱和脂肪酸的抗性。Tet38 还有助于金黄色葡萄球菌在小鼠皮肤中的定植。在这项研究中，我们发现了 Tet38 的一种新的调节因子，命名为四环素调节因子 21（TetR21），它特异性地结合到 tet38 启动子上并抑制泵的表达。ΔtetR21 突变体的 tet38 转录物增加了 5 倍，对四环素和脂肪酸的抗性增加了 8 倍。全局调节因子 MgrA 结合到 tetR21 启动子上，并间接抑制 tet38 的表达。为了进一步评估 Tet38 在金黄色葡萄球菌适应性中的全部作用，我们使用 A549（肺）和 HMEC-1（心脏）细胞系测试了它对宿主细胞侵袭的影响。我们使用了金黄色葡萄球菌 RN6390、其 Δtet38、ΔtetR21 和 ΔmgrA 突变体以及 Δtet38 ΔtetR21 双突变体。接触 2 小时后，与 RN6390 相比，Δtet38 突变体在 A549 和 HMEC-1 细胞中的内化数量减少了 6 倍，而 ΔtetR21 突变体的内化数量增加了 2 倍。ΔmgrA 突变体的内化数量略有增加，为 1.5 倍。RN6390 以及 ΔmgrA 和 ΔtetR21 突变体在 A549 细胞内的生长模式相似，而 Δtet38 突变体则没有生长。这些数据表明，Tet38 外排泵受 TetR21 调节，并有助于金黄色葡萄球菌内化和在上皮细胞内复制的能力。
