Division of Infectious Diseases, Department of Pediatrics, McGovern Medical School, University of Texas Health Sciences Center at Houston, Houston, Texas, USA.
Division of Infectious Diseases, Department of Pediatrics, McGovern Medical School, University of Texas Health Sciences Center at Houston, Houston, Texas, USA
mBio. 2020 Sep 15;11(5):e01804-20. doi: 10.1128/mBio.01804-20.
LiaFSR is a gene regulatory system important for response to cell membrane stress in Gram-positive bacteria but is minimally studied in the important human pathogen group A (GAS). Using immunofluorescence and immunogold electron microscopy, we discovered that LiaF (a membrane-bound repressor protein) and LiaS (a sensor kinase) reside within the GAS membrane microdomain (ExPortal). Cell envelope stress induced by antimicrobials resulted in ExPortal disruption and activation of the LiaFSR system. The only human antimicrobial peptide whose presence resulted in ExPortal disruption and LiaFSR activation was the alpha-defensin human neutrophil peptide 1 (hNP-1). Elimination of membrane cardiolipin through targeted gene deletion resulted in loss of LiaS colocalization with the GAS ExPortal and activation of LiaFSR, whereas LiaF membrane localization was unaffected. Isogenic mutants lacking either LiaF or LiaS revealed a critical role of LiaF in ExPortal integrity. Thus, LiaF and LiaS colocalize with the GAS ExPortal by distinct mechanisms, further supporting codependence. These are the first data identifying a multicomponent signal system within the ExPortal, thereby providing new insight into bacterial intramembrane signaling in GAS that may serve as a paradigm for Gram-positive bacteria. Bacterial two-component systems sense and induce transcriptional changes in response to environmental stressors, including antimicrobials and human antimicrobial peptides. Since the stresses imposed by the host's defensive responses may act as markers of specific temporal stages of disease progression or host compartments, pathogens often coordinately regulate stress response programs with virulence factor expression. The mechanism by which bacteria recognize these stresses and subsequently induce transcriptional responses remains not well understood. In this study, we showed that LiaFSR senses cell envelope stress through colocalization of LiaF and LiaS with the group A (GAS) ExPortal and is activated in direct response to ExPortal disruption by antimicrobials or human antimicrobial peptides. Our studies shed new light on the sensing of cell envelope stress in Gram-positive bacteria and may contribute to the development of therapies targeting these processes.
LiaFSR 是革兰氏阳性菌中重要的细胞膜应激反应基因调控系统，但在 A 组链球菌（GAS）等重要的人类病原体中研究甚少。通过免疫荧光和免疫金电子显微镜，我们发现 LiaF（一种膜结合的阻遏蛋白）和 LiaS（一种传感器激酶）存在于 GAS 膜微区（ExPortal）中。抗生素引起的细胞包膜应激导致 ExPortal 破坏和 LiaFSR 系统的激活。唯一导致 ExPortal 破坏和 LiaFSR 激活的人类抗菌肽是α-防御素人中性粒细胞肽 1（hNP-1）。通过靶向基因缺失消除膜心磷脂导致 LiaS 与 GAS ExPortal 的共定位丧失和 LiaFSR 的激活，而 LiaF 的膜定位不受影响。缺乏 LiaF 或 LiaS 的同工酶突变体表明 LiaF 在 ExPortal 完整性中起着关键作用。因此，LiaF 和 LiaS 通过不同的机制与 GAS 的 ExPortal 共定位，进一步支持了它们的依赖性。这些是首次在 ExPortal 中鉴定出多组分信号系统的数据，从而为 GAS 中的细菌跨膜信号提供了新的见解，这可能成为革兰氏阳性菌的范例。细菌双组分系统通过感应和诱导转录变化来响应环境应激物，包括抗生素和人类抗菌肽。由于宿主防御反应施加的应激可能作为疾病进展特定时间阶段或宿主隔室的标志物，病原体通常协调调节应激反应程序与毒力因子表达。细菌识别这些应激并随后诱导转录反应的机制仍未得到很好的理解。在这项研究中，我们表明 LiaFSR 通过 LiaF 和 LiaS 与 GAS ExPortal 的共定位来感知细胞包膜应激，并通过抗生素或人类抗菌肽对 ExPortal 的破坏直接激活。我们的研究为革兰氏阳性菌中细胞包膜应激的感应提供了新的视角，并可能有助于开发针对这些过程的治疗方法。
