Listeria monocytogenes Internalin B Activates Junctional Endocytosis to Accelerate Intestinal Invasion

Abstract

Listeria monocytogenes (Lm) uses InlA to invade the tips of the intestinal villi, a location at which cell extrusion generates a transient defect in epithelial polarity that exposes the receptor for InlA, E-cadherin, on the cell surface. As the dying cell is removed from the epithelium, the surrounding cells reorganize to form a multicellular junction (MCJ) that Lm exploits to find its basolateral receptor and invade. By examining individual infected villi using 3D-confocal imaging, we uncovered a novel role for the second major invasin, InlB, during invasion of the intestine. We infected mice intragastrically with isogenic strains of Lm that express or lack InlB and that have a modified InlA capable of binding murine E-cadherin and found that Lm lacking InlB invade the same number of villi but have decreased numbers of bacteria within each infected villus tip. We studied the mechanism of InlB action at the MCJs of polarized MDCK monolayers and find that InlB does not act as an adhesin, but instead accelerates bacterial internalization after attachment. InlB locally activates its receptor, c-Met, and increases endocytosis of junctional components, including E-cadherin. We show that MCJs are naturally more endocytic than other sites of the apical membrane, that endocytosis and Lm invasion of MCJs depends on functional dynamin, and that c-Met activation by soluble InlB or hepatocyte growth factor (HGF) increases MCJ endocytosis. Also, in vivo, InlB applied through the intestinal lumen increases endocytosis at the villus tips. Our findings demonstrate a two-step mechanism of synergy between Lm's invasins: InlA provides the specificity of Lm adhesion to MCJs at the villus tips and InlB locally activates c-Met to accelerate junctional endocytosis and bacterial invasion of the intestine.

The adherens junctions control susceptibility to Staphylococcus aureus α-toxin

“…It is increasingly appreciated, however, that microbial interactions with the host epithelium and cell-cell junctions are not restricted to mechanical disruption of barrier function (39,41). Mounting evidence illustrates that bacteria can actively modulate other important aspects of junction function, such as altering cell polarity (42)(43)(44) and intracellular signals emanating from the junctions (45)(46)(47). Our findings build importantly on these observations, revealing not only that S. aureus α-toxin does target the junctions but also that α-toxin acts through adherens junctions components to mediate its cytotoxicity.…”

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

“…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). It has thus been proposed that InlA provides specificity of adhesion to exposed E-cadherin at the tip of small intestine villi and InlB activates Met to accelerate junction endocytosis and bacterial invasion of enterocytes.…”

PI3-kinase activation is critical for host barrier permissiveness to Listeria monocytogenes

“…This suggests that, in models permissive to both InlA and InlB, InlB-requirement for Lm invasion of Peyer's patch There are apparently conflicting data regarding the role of InlB in the crossing of intestinal barrier: whereas we have repeatedly found no role for InlB in Lm crossing of the intestinal barrier in in vivo models permissive to both InlA-Ecad and InlB-c-Met interactions (Khelef et al, 2006;Disson et al, 2008), it has been reported by others that InlB accelerates invasion at villous tips in an experimental model using murinized InlA (Pentecost et al, 2010) and plays a role at the Peyer's patch level in WT mice (Chiba et al, 2011). Here, we have confirmed these results and revisited their interpretations in light of our new investigations: we compared the infection of murinized InlA (InlA m ) expressing Lm (Wollert et al, 2007) in WT mice (Pentecost et al, 2010) and the infection of WT Lm in KIE16P mice expressing humanized mEcad (Disson et al, 2008) at the villous tip level. Importantly, we have recently demonstrated that InlA m confers to Lm the ability to target both Ecad and Ncad, the latter being accessible on the luminal side of villous M cells (Tsai et al, 2013).…”

“…However, Pentecost et al (2010) have reported that InlB plays a role in invading the tip of intestinal villi in WT mice inoculated with Lm expressing a murinized version of InlA (Lm-InlA m ), which interacts with mEcad. Importantly, we have recently shown that Lm-InlA m not only invades cells expressing acc-Ecad, such as GCs, but also targets villous M cells, as a result of the spurious interaction of InlA m with N-cadherin (Ncad), which is luminally accessible at the apical pole of these cells (Tsai et al, 2013).…”