Abstract
Colonization and disruption of the epithelium is a major infection mechanism of mucosal pathogens. The epithelium counteracts infection by exfoliating damaged cells while maintaining the mucosal barrier function. The sexually transmitted bacterium Neisseria gonorrhoeae (GC) infects the female reproductive tract primarily from the endocervix, causing gonorrhea. However, the mechanism by which GC overcome the mucosal barrier remains elusive. Using a new human tissue model, we demonstrate that GC can penetrate into the human endocervix by inducing the exfoliation of columnar epithelial cells. We found that GC colonization causes endocervical epithelial cells to shed. The shedding results from the disassembly of the apical junctions that seal the epithelial barrier. Apical junction disruption and epithelial exfoliation increase GC penetration into the endocervical epithelium without reducing bacterial adherence to and invasion into epithelial cells. Both epithelial exfoliation and junction disruption require the activation and accumulation of non-muscle myosin II (NMII) at the apical surface and GC adherent sites. GC inoculation activates NMII by elevating the levels of the cytoplasmic Ca2+ and NMII regulatory light chain phosphorylation. Piliation of GC promotes, but the expression of a GC opacity-associated protein variant, OpaH that binds to the host surface proteins CEACAMs, inhibits GC-induced NMII activation and reorganization and Ca2+ flux. The inhibitory effects of OpaH lead to reductions in junction disruption, epithelial exfoliation, and GC penetration. Therefore, GC phase variation can modulate infection in the human endocervix by manipulating the activity of NMII and epithelial exfoliation.
Highlights
Microbial pathogens establish infection at the mucosal surface by colonization, disruption, and penetration of the epithelium [1]
Tissue explants that were cultured with the mucosal side up and T84 cells that were polarized on transwells were inoculated apically with a GC strain, MS11 that express phase variable opacity-associate protein (Opa) and pili (MS11Pil+Opa+) at a MOI of ~10 for 6 or 24 h
There was no significant difference between the percentages of epithelial cells with penetrated MS11ΔOpa and MS11OpaC and between those with penetrated MS11Opa+ and MS11OpaH (Fig 3B). These results indicate that GC can penetrate into the subepithelium of the human endocervix in the tissue explant model, and the expression of carcinoembryonic antigen-related cell adhesion molecules (CEACAMs)-binding OpaH, which reduces GC-induced epithelial exfoliation, but not heparin sulfate proteoglycans (HSPG)-binding OpaC, which does not affect the exfoliation, inhibits GC penetration
Summary
Microbial pathogens establish infection at the mucosal surface by colonization, disruption, and penetration of the epithelium [1]. Different from multilayered squamous epithelial cells that are held together by adherent junctions, the monolayer epithelium is sealed by the apical junction, which prevents the entry of pathogens through the paracellular space (gate function) and maintains the polarity of the apical and basolateral surfaces (fence function) [4,5,6,7]. ZO1 and β-catenin link the apical junction to the actin cytoskeleton and signaling networks [7,8,9,10,11]. The actin cytoskeleton and non-muscle myosin II (NMII) form a supporting ring at the apical junction [12,13,14]. Over activation of the actomyosin ring can lead to the disassembly of the apical junction by inducing the endocytosis of junctional proteins [18, 19]
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