Exploration of the role of the virulence factor ElrA during Enterococcus faecalis cell infection

Natalia Nunez,Julien Deschamps,Pascale Serror,Mustapha Si-Tahar,Thomas Baranek,Romain Briandet,Aurélie Derré-Bobillot,Yu Wei,Jean-Marie Herry,Cristel Archambaud,Stéphane Gaubert

doi:10.1038/s41598-018-20206-6

Abstract

Enterococcus faecalis, an organism generally not pathogenic for healthy humans, has the potential to cause disease in susceptible hosts. While it seems to be equipped to interact with and circumvent host immune defense, most of the molecular and cellular mechanisms underlying the enterococcal infectious process remain elusive. Here, we investigated the role of the Enterococcal Leucine Rich protein A (ElrA), an internalin-like protein of E. faecalis also known as a virulence factor. ElrA was previously shown to prevent adhesion to macrophages. We show that ElrA does not inhibit the basic phagocytic process, but is able to prevent sensing and migration of macrophages toward E. faecalis. Presence or absence of FHL2, a eukaryotic partner of ElrA, does not affect the ElrA-dependent mechanism preventing macrophage migration. However, we highlight a partial contribution of FHL2 in ElrA-mediated virulence in vivo. Our results indicate that ElrA plays at least a dual role of which anti-phagocytic activity may contribute to dissemination of extracellular E. faecalis during infection.

Highlights

Gram positive Enterococcus faecalis is a subdominant commensal of the gut microbiota
enterococcal leucine-rich protein A (ElrA) is an internalin-like protein implicated in prevention of macrophage adhesion and E. faecalis evasion from macrophage phagocytosis[9]
We ruled out the possibilities that electric repulsion between the bacterial and eukaryotic cell surface or that major structural changes in E. faecalis envelope are responsible for ElrA-dependent escape

Summary

Introduction

Gram positive Enterococcus faecalis is a subdominant commensal of the gut microbiota. The enterococcal leucine-rich protein A (ElrA), which belongs to the internalin family, is a surface virulence factor[5]. Since elrA expression is undetectable in vitro and elrB, elrC, elrD and elrE are required for ElrA stabilization, the native promoter of the operon has been exchanged by the constitutive aphA3 promoter (P+-elrA-E strain)[9]. FHL2 is formed of LIM domains involved in several protein-protein interactions and participates in a wide range of cellular processes including cellular transcription, signal transduction and cell survival or death[11]. Such broad roles for FHL2 opens up a wide spectrum of possibilities for FH2 contribution in E. faecalis virulence. We investigated whether disruption of FHL2, an ElrA partner, impacts on this process

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