Listeria monocytogenes Invades the Epithelial Junctions at Sites of Cell Extrusion

Abstract

Listeria monocytogenes causes invasive disease by crossing the intestinal epithelial barrier. This process depends on the interaction between the bacterial surface protein Internalin A and the host protein E-cadherin, located below the epithelial tight junctions at the lateral cell-to-cell contacts. We used polarized MDCK cells as a model epithelium to determine how L. monocytogenes breaches the tight junctions to gain access to this basolateral receptor protein. We determined that L. monocytogenes does not actively disrupt the tight junctions, but finds E-cadherin at a morphologically distinct subset of intercellular junctions. We identified these sites as naturally occurring regions where single senescent cells are expelled and detached from the epithelium by extrusion. The surrounding cells reorganize to form a multicellular junction that maintains epithelial continuity. We found that E-cadherin is transiently exposed to the lumenal surface at multicellular junctions during and after cell extrusion, and that L. monocytogenes takes advantage of junctional remodeling to adhere to and subsequently invade the epithelium. In intact epithelial monolayers, an anti-E-cadherin antibody specifically decorates multicellular junctions and blocks L. monocytogenes adhesion. Furthermore, an L. monocytogenes mutant in the Internalin A gene is completely deficient in attachment to the epithelial apical surface and is unable to invade. We hypothesized that L. monocytogenes utilizes analogous extrusion sites for epithelial invasion in vivo. By infecting rabbit ileal loops, we found that the junctions at the cell extrusion zone of villus tips are the specific target for L. monocytogenes adhesion and invasion. Thus, L. monocytogenes exploits the dynamic nature of epithelial renewal and junctional remodeling to breach the intestinal barrier.

Entry of Listeria monocytogenes in Mammalian Epithelial Cells: An Updated View

“…Using rabbit ligated ileal loops and Madin-Darby canine kidney (MCDK) cells as a polarized epithelium model, it has been proposed that L. monocytogenes does not disrupt the enterocyte tight junctions to gain access to E-cadherin, but instead interacts with exposed E-cadherin at sites where apoptotic cells are expelled and detached from the epithelium by extrusion, suggesting that L. monocytogenes exploits the dynamic nature of epithelial renewal and junctional remodeling in small intestinal villi to breach this barrier (Fig. 3) (Pentecost et al 2006). Of note, infection of wild-type mice intragastrically with a L. monocytogenes strain expressing a modified InlA that binds murine Ecadherin suggested that InlB also participates in bacterial internalization at small intestine villi; experiments in MDCK cells suggest that InlB does not act as an adhesin but rather accelerates bacterial internalization by promoting endocytosis of junctional components (Pentecost et al 2010).…”

Concepts and Mechanisms: Crossing Host Barriers

“…The way by which L. monocytogenes gets access to the adherens junction protein Ecadherin and the mechanism by which bacteria cross the intestinal barrier were not known until recently. It had been proposed that L. monocytogenes access to E-cadherin may be facilitated when extruding epithelial cells detach from the tips of intestinal microvilli, thereby exposing Ecadherin to the luminal side of the intestine (Pentecost et al 2006). This was shown in vitro and correlated with a colocalization of bacteria with extruding cells in rabbit ileal loop in vivo.…”

LAP, an alcohol acetaldehyde dehydrogenase enzyme in Listeria, promotes bacterial adhesion to enterocyte-like Caco-2 cells only in pathogenic species

“…) Sabet et al, 2008). Although cellular mechanisms of infection are becoming more clear (Hamon et al, 2006), we still have much to learn about the intestinal (Gahan & Hill, 2005;Pentecost et al, 2006), utero-placental (Bakardjiev et al, 2006;Lecuit et al, 2004) and neurological phases of infection (Drevets & Bronze, 2008).…”