霍乱弧菌外膜囊泡通过孔蛋白依赖摄取保护并将活性霍乱毒素递送至宿主细胞。

Outer Membrane Vesicles of Vibrio cholerae Protect and Deliver Active Cholera Toxin to Host Cells via Porin-Dependent Uptake.

机构信息

Institute of Molecular Biosciences, University of Graz, Graz, Austria.

BioTechMed Graz, Graz, Austria.

出版信息

mBio. 2021 Jun 29;12(3):e0053421. doi: 10.1128/mBio.00534-21. Epub 2021 May 26.

Abstract

Outer membrane vesicles (OMVs) are an emerging research field due to their multifactorial composition and involvement in interspecies and intraspecies communication. Recent studies indicate that vesicle release by Gram-negative bacterial pathogens is increased during colonization, as exemplified by the facultative human pathogen Vibrio cholerae upon oral ingestion by the host. In this study, we investigate the fate of OMVs produced by the Gram-negative facultative pathogen V. cholerae. We show that vesicles produced by the clinically relevant El Tor biotype are readily taken up by human intestinal cell lines. We identify outer membrane porins of V. cholerae, i.e., OmpU and OmpT, as the required surface effectors on OMVs for cellular uptake, and we pinpoint the uptake mechanism as caveolin-mediated endocytosis. Furthermore, we show that OMVs derived from V. cholerae grown under virulence-inducing conditions act as potent vehicles for delivery of bioactive cholera toxin to intestinal epithelial cells. In contrast to free cholera toxin secreted via the type II secretion system, OMV-associated cholera toxin is protected from degradation by intestinal proteases. Taken together, these data show that OMV-associated cholera toxin can sustain longer periods in the intestinal tract and preserve toxin effects, as indicated by a prolonged increase of cAMP levels in the intestinal tissue. Cholera is still a massive global health burden because it causes large outbreaks with millions of infections and thousands of deaths every year. Several studies have contributed to the knowledge of this pathogen, although key parts are still missing. We aim to broaden our understanding of Vibrio cholerae infections, virulence, and toxicity by drawing attention to the involvement of OMVs in these core processes. Upon host entry, V. cholerae increases secretion of OMVs, which can carry the main virulence factor, cholera toxin, to distant host intestinal cells. We show that specific outer membrane porins on the vesicle surface mediate endocytosis of the vesicles into intestinal cells. With protection by the vesicles, cholera toxin activity endures even in the presence of intestinal proteases. It is tempting to hypothesize that the extended half-life of vesicle-associated cholera toxin allows it to target host cells distant from the primary colonization sites.

摘要

外膜囊泡(OMVs)是一个新兴的研究领域,因为它们的多因素组成以及在种间和种内通讯中的作用。最近的研究表明,革兰氏阴性细菌病原体在定植过程中释放囊泡的数量增加,例如,当宿主经口摄入时,兼性人类病原体霍乱弧菌就是如此。在这项研究中,我们研究了革兰氏阴性兼性病原体霍乱弧菌产生的 OMVs 的命运。我们表明,临床相关的 El Tor 生物型产生的囊泡很容易被人肠细胞系摄取。我们确定霍乱弧菌的外膜孔蛋白,即 OmpU 和 OmpT,是 OMVs 细胞摄取所必需的表面效应蛋白,并确定摄取机制为小窝蛋白介导的内吞作用。此外,我们表明,在诱导毒力条件下生长的霍乱弧菌衍生的 OMVs 可作为生物活性霍乱毒素向肠上皮细胞递呈的有效载体。与通过 II 型分泌系统分泌的游离霍乱毒素不同,OMV 相关的霍乱毒素免受肠道蛋白酶的降解。总之,这些数据表明,与游离霍乱毒素相比,OMV 相关的霍乱毒素在肠道中能维持更长的时间,并保持毒素的作用,这表现为肠道组织中 cAMP 水平的延长增加。霍乱仍然是一个巨大的全球健康负担,因为它每年导致数百万人感染和数千人死亡的大规模暴发。尽管关键部分仍然缺失,但已有多项研究有助于了解这种病原体。我们旨在通过关注 OMVs 在这些核心过程中的参与,拓宽对霍乱弧菌感染、毒力和毒性的理解。当宿主进入时,霍乱弧菌增加 OMVs 的分泌,这些囊泡可以携带主要的毒力因子霍乱毒素,递呈到远离宿主肠道细胞的地方。我们表明,囊泡表面上的特定外膜孔蛋白介导了囊泡进入肠细胞的内吞作用。由于囊泡的保护,即使存在肠道蛋白酶,霍乱毒素的活性也能持续存在。我们可以假设,囊泡相关的霍乱毒素的半衰期延长,使其能够靶向远离定植部位的宿主细胞。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/680d/8262896/530ffe1208ef/mbio.00534-21-f001.jpg

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