Division of Infectious Diseases, St John's Cardiovascular Research Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California, USA.
Antimicrob Agents Chemother. 2013 Aug;57(8):3875-82. doi: 10.1128/AAC.00412-13. Epub 2013 Jun 3.
Many host defense cationic antimicrobial peptides (HDPs) perturb the staphylococcal cell membrane (CM) and alter transmembrane potential (ΔΨ) as key parts of their lethal mechanism. Thus, a sense-response system for detecting and mediating adaptive responses to such stresses could impact organism survival; the Staphylococcus aureus LytSR two-component regulatory system (TCRS) may serve as such a ΔΨ sensor. One well-known target of this system is the lrgAB operon, which, along with the related cidABC operon, has been shown to be a regulator in the control of programmed cell death and lysis. We used an isogenic set of S. aureus strains: (i) UAMS-1, (ii) its isogenic ΔlytS and ΔlrgAB mutants, and (iii) plasmid-complemented ΔlytSR and ΔlrgAB mutants. The ΔlytS strain displayed significantly increased in vitro susceptibilities to all HDPs tested (neutrophil-derived human neutrophil peptide 1 [hNP-1], platelet-derived thrombin-induced platelet microbicidal proteins [tPMPs], and the tPMP-mimetic peptide RP-1), as well as to calcium-daptomycin (DAP), a cationic antimicrobial peptide (CAP). In contrast, the ΔlrgAB strain exhibited no significant changes in susceptibilities to these cationic peptides, indicating that although lytSR positively regulates transcription of lrgAB, increased HDP/CAP susceptibilities in the ΔlytS mutant were lrgAB independent. Further, parental UAMS-1 (but not the ΔlytS mutant) became more resistant to hNP-1 and DAP following pretreatment with carbonyl cyanide m-chlorophenylhydrazone (CCCP) (a CM-depolarizing agent). Of note, lytSR-dependent survival against CAP/HDP killing was not associated with changes in either surface positive charge, expression of mprF and dlt, or CM fluidity. The ΔlytS strain (but not the ΔlrgAB mutant) displayed a significant reduction in target tissue survival in an endocarditis model during DAP treatment. Collectively, these results suggest that the lytSR TCRS plays an important role in adaptive responses of S. aureus to CM-perturbing HDPs/CAPs, likely by functioning as a sense-response system for detecting subtle changes in ΔΨ.
许多宿主防御阳离子抗菌肽（HDPs）扰乱金黄色葡萄球菌细胞膜（CM）并改变跨膜电位（ΔΨ），这是其致死机制的关键部分。因此，一种用于检测和介导对这种应激的适应性反应的感应-反应系统可能会影响生物体的存活；金黄色葡萄球菌 LytSR 双组分调节系统（TCRS）可能就是这样的ΔΨ传感器。该系统的一个众所周知的靶标是 lrgAB 操纵子，该操纵子与相关的 cidABC 操纵子一起，已被证明是控制程序性细胞死亡和裂解的调节剂。我们使用了一组同源的金黄色葡萄球菌菌株：（i）UAMS-1，（ii）其同源的ΔlytS 和ΔlrgAB 突变体，以及（iii）质粒互补的ΔlytSR 和ΔlrgAB 突变体。ΔlytS 菌株对所有测试的 HDP（中性粒细胞衍生的人中性粒细胞肽 1 [hNP-1]、血小板衍生的凝血酶诱导的血小板杀菌蛋白 [tPMPs] 和 tPMP 模拟肽 RP-1）以及钙结合达托霉素（DAP）的体外敏感性显著增加，这是一种阳离子抗菌肽（CAP）。相比之下，ΔlrgAB 菌株对这些阳离子肽的敏感性没有明显变化，表明尽管 lytSR 正向调节 lrgAB 的转录，但在ΔlytS 突变体中增加的 HDP/CAP 敏感性与 lrgAB 无关。此外，亲本 UAMS-1（而不是ΔlytS 突变体）在用羰基氰化物 m-氯苯腙（CCCP）（一种 CM 去极化剂）预处理后对 hNP-1 和 DAP 的耐药性更高。值得注意的是，依赖 lytSR 的对 CAP/HDP 杀伤的存活与表面正电荷、mprF 和 dlt 的表达或 CM 流动性的变化无关。ΔlytS 菌株（而不是ΔlrgAB 突变体）在 DAP 治疗期间的心内膜炎模型中靶组织存活显著减少。总的来说，这些结果表明，lytSR TCRS 在金黄色葡萄球菌对 CM 扰乱的 HDP/CAP 的适应性反应中发挥重要作用，可能通过作为检测ΔΨ 细微变化的感应-反应系统发挥作用。
