Focal Area Infection Biology, Biozentrum, University of Basel, Basel, Switzerland.
Department of Biochemistry, University of Lausanne, Epalinges, Switzerland.
EMBO J. 2018 Mar 15;37(6). doi: 10.15252/embj.201798089. Epub 2018 Feb 19.
Pathogenic and commensal Gram-negative bacteria produce and release outer membrane vesicles (OMVs), which present several surface antigens and play an important role for bacterial pathogenesis. OMVs also modulate the host immune system, which makes them attractive as vaccine candidates. At the cellular level, OMVs are internalized by macrophages and deliver lipopolysaccharide (LPS) into the host cytosol, thus activating the caspase-11 non-canonical inflammasome. Here, we show that OMV-induced inflammasome activation requires TLR4-TRIF signaling, the production of type I interferons, and the action of guanylate-binding proteins (GBPs), both in macrophages and Mechanistically, we find that isoprenylated GBPs associate with the surface of OMVs or with transfected LPS, indicating that the key factor that determines GBP recruitment to the Gram-negative bacterial outer membranes is LPS itself. Our findings provide new insights into the mechanism by which GBPs target foreign surfaces and reveal a novel function for GBPs in controlling the intracellular detection of LPS derived from extracellular bacteria in the form of OMVs, thus extending their function as a hub between cell-autonomous immunity and innate immunity.
致病性和共生革兰氏阴性细菌会产生和释放外膜囊泡(OMV),这些囊泡携带多种表面抗原,在细菌发病机制中发挥重要作用。OMV 还能调节宿主的免疫系统,这使得它们成为有吸引力的疫苗候选物。在细胞水平上,OMV 被巨噬细胞内化,并将脂多糖(LPS)递送到宿主细胞质中,从而激活半胱天冬酶-11 非经典炎性小体。在这里,我们表明 OMV 诱导的炎性小体激活需要 TLR4-TRIF 信号转导、I 型干扰素的产生以及鸟苷酸结合蛋白(GBP)的作用,无论是在巨噬细胞中还是在转染的 LPS 中。从机制上讲,我们发现异戊烯化 GBP 与 OMV 的表面或转染的 LPS 结合,表明决定 GBP 招募革兰氏阴性细菌外膜的关键因素是 LPS 本身。我们的发现为 GBP 靶向外来表面的机制提供了新的见解,并揭示了 GBP 在控制以 OMV 形式从细胞外细菌中衍生的 LPS 的细胞内检测方面的新功能,从而扩展了它们作为细胞自主免疫和先天免疫之间的枢纽的功能。