The bile salt sodium taurocholate induces Campylobacter jejuni outer membrane vesicle production and increases OMV-associated proteolytic activity

Abdi Elmi, Amber Dorey, Eleanor Watson, Heena Jagatia, Neil F. Inglis, Ozan Gundogdu, Mona Bajaj-Elliott, Brendan W. Wren, David George Emslie Smith, Nick Dorrell

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Abstract

Campylobacter jejuni, the leading cause of bacterial acute gastroenteritis worldwide, secretes an arsenal of virulence-associated proteins within outer membrane vesicles (OMVs). C. jejuni OMVs contain three serine proteases (HtrA, Cj0511 and Cj1365c) which cleave the intestinal epithelial cell (IEC) tight and adherens junction proteins occludin and E-cadherin, promoting enhanced C. jejuni adhesion to and invasion of IECs. C. jejuni OMVs also induce IECs innate immune responses. The bile salt sodium taurocholate (ST) is sensed as a host signal to co-ordinate the activation of virulence-associated genes in the enteric pathogen Vibrio cholerae. In this study, the effect of ST on C. jejuni OMVs was investigated. Physiological concentrations of ST do not have an inhibitory effect on C. jejuni growth until the early stationary phase. Co-culture of C. jejuni with 0.1% or 0.2% (w/v) ST stimulates OMV production, increasing both lipid and protein concentrations. C. jejuni ST-OMVs possess increased proteolytic activity and exhibit a different protein profile compared to OMVs isolated in the absence of ST. ST-OMVs exhibit enhanced cytotoxicity and immunogenicity to T84 IECs and enhanced killing of Galleria mellonella larvae. ST increases the level of mRNA transcripts of the OMVs-associated serine protease genes and the cdtABC operon that encodes the cytolethal distending toxin. Co-culture with ST significantly enhances the OMVs-induced cleavage of E-cadherin and occludin. C. jejuni OMVs also cleave the major endoplasmic reticulum (ER) chaperone protein BiP/GRP78 and this activity is associated with the Cj1365c protease. This data suggests that C. jejuni responds to the presence of physiological concentrations of the bile salt ST which increases OMV production and the synthesis of virulence-associated factors that are secreted within the OMVs. We propose that these events contribute to pathogenesis.

Original languageEnglish
Article numbere12814
JournalCellular Microbiology
Volume20
Issue number3
Early online date4 Dec 2017
DOIs
Publication statusPublished - Mar 2018

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    Elmi, A., Dorey, A., Watson, E., Jagatia, H., Inglis, N. F., Gundogdu, O., Bajaj-Elliott, M., Wren, B. W., Smith, D. G. E., & Dorrell, N. (2018). The bile salt sodium taurocholate induces Campylobacter jejuni outer membrane vesicle production and increases OMV-associated proteolytic activity. Cellular Microbiology, 20(3), [e12814]. https://doi.org/10.1111/cmi.12814