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Title: Relaxation of DNA supercoiling leads to increased invasion of epithelial cells and protein secretion by Campylobacter jejuni

Author
item SCANLAN, EOIN - University College Dublin
item ARDILL, LAURA - University College Dublin
item WHELAN, MATTHEW - University College - Ireland
item SHORTT, CLAIRE - University College Dublin
item Nally, Jarlath
item BOURKE, BILLY - University College Dublin
item O'CROININ, TADHG - University College Dublin

Submitted to: Molecular Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 2/6/2017
Citation: Scanlan, E., Ardill, L., Whelan, M., Shortt, C., Nally, J.E., Bourke, B., O'Croinin, T. 2017. Relaxation of DNA supercoiling leads to increased invasion of epithelial cells and protein secretion by Campylobacter jejuni. Molecular Microbiology. 104(1):92-104. doi: 10.1111/mmi.13614.

Interpretive Summary: Campylobacter jejuni infection is a leading cause of bacterial gastroenteritis. However, relatively little is known about the molecular mechanisms that this bacterium uses to cause infection. Of particular interest is how this bacterium attaches to, and invades, the host cells of the gut. In this study, the relaxed state of DNA supercoiling is shown to influence the ability of Campylobacter to attach to, and invade cells. Further, DNA supercoiling was also shown to regulate protein secretion. Collectively, these results provide new insights into how Campylobacter causes infection. The identification of such regulatory pathways that bacteria use to cause disease can be used to provide novel intervention strategies and treatments.

Technical Abstract: Invasion of intestinal epithelial cells by Campylobacter jejuni is a critical step during infection of the human intestine by this important human pathogen. In this study we investigated the role played by DNA supercoiling in the regulation of invasion of epithelial cells and the mechanism by which this could be mediated. A significant correlation between more relaxed DNA supercoiling and an increased ability of C. jejuni strains to penetrate human epithelial cells was demonstrated. Directly inducing relaxation of DNA supercoiling in C. jejuni was shown to significantly increase invasion of epithelial cells. Mutants in the fibronectin binding proteins CadF and FlpA still displayed an increased invasion after treatment with novobiocin suggesting these proteins were not essential for the observed phenotype. However, a large increase in protein secretion from multiple C. jejuni strains upon relaxation of DNA supercoiling was demonstrated. This increase in protein secretion was not mediated by outer membrane vesicles and appeared to be dependent on an intact flagellar structure. This study identifies relaxation of DNA supercoiling as playing a key role in enhancing C. jejuni pathogenesis during infection of the human intestine and identifies proteins present in a specific invasion associated secretome induced by relaxation of DNA supercoiling.