Laboratory Microbial Pathogenesis, Fundació d'Investigació Sanitària de les Illes Balears (FISIB), Recinto Hospital Joan March, 07110, Bunyola, Spain.
Cell Microbiol. 2013 Jul;15(7):1212-33. doi: 10.1111/cmi.12110. Epub 2013 Feb 17.
The NF-κB transcriptional factor plays a key role governing the activation of immune responses. Klebsiella pneumoniae is an important cause of community-acquired and nosocomial pneumonia. Evidence indicates that K. pneumoniae infections are characterized by lacking an early inflammatory response. Recently, we have demonstrated that Klebsiella antagonizes the activation of NF-κB via the deubiquitinase CYLD. In this work, by applying a high-throughput siRNA gain-of-function screen interrogating the human kinome, we identified 17 kinases that when targeted by siRNA restored IL-1β-dependent NF-κB translocation in infected cells. Further characterization revealed that K. pneumoniae activates an EGF receptor (EGFR)-phosphatidylinositol 3-OH kinase (PI3K)-AKT-PAK4-ERK-GSK3β signalling pathway to attenuate the cytokine-dependent nuclear translocation of NF-κB. Our data also revealed that CYLD is a downstream effector of K. pneumoniae-induced EGFR-PI3K-AKT-PAK4-ERK-GSK3β signalling pathway. Our efforts to identify the bacterial factor(s)responsible for EGFR activation demonstrate that a capsule (CPS) mutant did not activate EGFR hence suggesting that CPS could mediate the activation of EGFR. Supporting this notion, purified CPS did activate EGFR as well as the EGFR-dependent PI3K-AKT-PAK4-ERK-GSK3β signalling pathway. CPS-mediated EGFR activation was dependent on a TLR4-MyD88-c-SRC-dependent pathway. Several promising drugs have been developed to antagonize this cascade. We propose that agents targeting this signalling pathway might provide selective alternatives for the management of K. pneumoniae pneumonias.
NF-κB 转录因子在调节免疫反应的激活中起着关键作用。肺炎克雷伯菌是社区获得性和医院获得性肺炎的重要原因。有证据表明，肺炎克雷伯菌感染的特点是缺乏早期炎症反应。最近，我们已经证明，肺炎克雷伯菌通过去泛素化酶 CYLD 拮抗 NF-κB 的激活。在这项工作中，我们应用高通量 siRNA 功能获得筛选技术，对人类激酶组进行了研究，鉴定出 17 种激酶，当这些激酶被 siRNA 靶向时，可恢复感染细胞中 IL-1β 依赖性 NF-κB 易位。进一步的表征揭示，肺炎克雷伯菌激活表皮生长因子受体（EGFR）-磷酸肌醇 3-激酶（PI3K）-AKT-PAK4-ERK-GSK3β 信号通路，以减弱细胞因子依赖性 NF-κB 的核易位。我们的数据还表明，CYLD 是肺炎克雷伯菌诱导的 EGFR-PI3K-AKT-PAK4-ERK-GSK3β 信号通路的下游效应物。我们在鉴定负责 EGFR 激活的细菌因子方面的努力表明，荚膜（CPS）突变体不能激活 EGFR，因此表明 CPS 可以介导 EGFR 的激活。支持这一观点，纯化的 CPS 确实激活了 EGFR 以及 EGFR 依赖性 PI3K-AKT-PAK4-ERK-GSK3β 信号通路。CPS 介导的 EGFR 激活依赖于 TLR4-MyD88-c-SRC 依赖性途径。已经开发了几种有前途的药物来拮抗这种级联反应。我们提出，针对该信号通路的药物可能为肺炎克雷伯菌肺炎的治疗提供选择性替代方案。
