Cameron David R, Jiang Jhih-Hang, Kostoulias Xenia, Foxwell Daniel J, Peleg Anton Y
Department of Microbiology, Monash University, Melbourne, Australia.
Department of Infectious Diseases, Alfred Hospital and Monash University, Melbourne, Australia.
Sci Rep. 2016 Sep 7;6:30823. doi: 10.1038/srep30823.
The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the 'WalRK regulon' including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy.
耐甲氧西林金黄色葡萄球菌引起的感染治疗因对万古霉素具有中度耐药性的菌株(称为万古霉素中度敏感金黄色葡萄球菌,VISA)的出现而变得复杂。我们已经鉴定出一条由调控蛋白YycH和YycI介导的、参与VISA体内进化的分子途径。与它们在其他细菌物种中的功能不同,我们报道了这些辅助蛋白在双组分调节因子WalRK调控中的正向作用。yycH和yycI缺失突变体的转录谱分析显示,包括细胞壁水解酶基因atlA和sle1在内的“WalRK调控子”下调,功能自溶试验通过显示每个缺失菌株的自溶表型受损来支持这些数据。使用细菌双杂交试验,我们表明YycH和YycI相互作用,并且YycHI也与传感激酶WalK相互作用,形成三元蛋白复合物。与临床VISA菌株相关的YycH或YycI突变对YycHI/WalK复合物有有害影响,表明这种相互作用对WalRK的调控很重要。综上所述,我们描述了人类病原体金黄色葡萄球菌一种新的抗生素耐药策略,即体内选择YycHI突变导致WalRK激活减少、细胞壁周转受损并最终降低万古霉素疗效。