College of Veterinary Medicine, Henan Agricultural University, 450002 Zhengzhou, China.
Zhengzhou Animal Husbandry Bureau, 450052 Zhengzhou, China.
J Antimicrob Chemother. 2020 Oct 1;75(10):2780-2786. doi: 10.1093/jac/dkaa233.
The two-component signalling systems PmrAB and PhoPQ of Salmonella have been extensively studied with regard to colistin resistance. We previously showed that overexpressed CpxR could significantly increase the colistin susceptibility (16-fold compared with the WT strain) of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) through PmrAB and PhoPQ.
To identify the potential target genes of CpxR in PmrAB- and PhoPQ-related signalling pathways.
His6-CpxR was prokaryotically expressed and purified by Ni-NTA resin affinity chromatography. β-Galactosidase activity assays were conducted to investigate whether CpxR could regulate the promoters of colistin resistance-related genes (CRRGs). Electrophoretic mobility shift assays (EMSAs) were used to further detect His6-CpxR complexes with promoters of CRRGs.
We demonstrated for the first time (to the best of our knowledge) that CpxR and the AcrAB-TolC efflux pump have reciprocal effects on CRRG transcription. Additionally, CpxR could regulate the colistin susceptibility of Salmonella Typhimurium by binding directly to the promoters of phoPQ, pmrC, pmrH and pmrD at the CpxR box-like sequences or indirectly through other regulators including pmrAB and mgrB.
CpxR could regulate the colistin susceptibility of Salmonella Typhimurium by a multitarget mechanism.
沙门氏菌的双组分信号系统 PmrAB 和 PhoPQ 已被广泛研究，以了解其对粘菌素的耐药性。我们之前曾表明，过表达的 CpxR 可以通过 PmrAB 和 PhoPQ 显著增加鼠伤寒沙门氏菌（沙门氏菌）的粘菌素敏感性（与 WT 菌株相比增加 16 倍）。
确定 CpxR 在 PmrAB 和 PhoPQ 相关信号通路中的潜在靶基因。
通过 Ni-NTA 树脂亲和层析原核表达和纯化 His6-CpxR。β-半乳糖苷酶活性测定用于研究 CpxR 是否可以调节粘菌素耐药相关基因（CRRGs）的启动子。电泳迁移率变动分析（EMSA）用于进一步检测 His6-CpxR 与 CRRGs 启动子的复合物。
我们首次证明（据我们所知），CpxR 和 AcrAB-TolC 外排泵对 CRRG 转录具有相互作用。此外，CpxR 可以通过直接结合 CpxR 盒样序列上的 phoPQ、pmrC、pmrH 和 pmrD 启动子，或通过其他调节因子（包括 pmrAB 和 mgrB）间接调节沙门氏菌 Typhimurium 的粘菌素敏感性。
CpxR 可以通过多靶点机制调节沙门氏菌 Typhimurium 的粘菌素敏感性。
