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 Streptococcus (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.

中文翻译：

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ExPortal和LiaFSR调节系统协调化脓链球菌对细胞膜应激的反应。

LiaFSR是一种基因调控系统，对革兰氏阳性细菌的细胞膜应激反应非常重要，但在重要的人类病原体A链球菌中进行的研究很少（加油站）。使用免疫荧光和免疫金电子显微镜，我们发现LiaF（膜结合阻遏蛋白）和LiaS（传感器激酶）位于GAS膜微区（ExPortal）中。抗生素诱导的细胞包膜应力导致ExPortal破坏和LiaFSR系统激活。其存在导致ExPortal破坏和LiaFSR激活的唯一人类抗菌肽是α-防御素人类嗜中性粒细胞肽1（hNP-1）。通过靶向基因删除消除膜心磷脂导致失去与GAS ExPortal共定位的LiaS和激活LiaFSR，而LiaF膜的定位不受影响。缺乏LiaF或LiaS的同基因突变体表明LiaF在ExPortal完整性中起着关键作用。从而，LiaF和LiaS通过不同的机制与GAS ExPortal共同定位，从而进一步支持了相互依赖性。这些是在ExPortal内识别多组分信号系统的第一批数据，从而提供了对GAS中细菌膜内信号传递的新见解，这些信号可以用作革兰氏阳性细菌的范例。