Abstract
The exact mechanism by which Entamoeba histolytica disrupts the human colonic epithelium and invades the mucosa has yet to be clearly elucidated. E. histolytica produces a diverse array of putative virulent factors such as glycosidase, cysteine proteinases and amebapore that can modulate and/or disrupt epithelial barrier functions. However, it is currently thought that E. histolytica produces numerous other molecules and strategies to disrupt colonic mucosal defenses. In this study, we document a putative mechanism whereby the parasite alters the integrity of human epithelium by expressing a cognate tight junction protein of the host. We detected this protein as “occludin-like” as revealed by immunoblotting and immunoprecipitation studies and visualization by confocal microscopy using antibodies highly specific for human occludin. We propose that E. histolytica occludin-like protein might displace mucosal epithelial occludin-occludin tight junction interactions resulting in epithelial disruption analogous to sub mucosal human dendritic cells sampling luminal contents. These results indicate that E. histolytica occludin is a putative virulent component that can play a role in the pathogenesis of intestinal amebiasis.
Highlights
Entamoeba histolytica is a protozoan parasite that colonizes the mucus barrier in the colon and can lead to amebiasis [1]
In this study we demonstrate the presence of a 55 kDa ‘‘occludin-like’’ protein in E. histolytica that can disrupt trans epithelial resistance (TER) in human colonic epithelial cells
Higher molecular weight bands were not observed in E. histolytica, suggesting that the protein may have a different pattern of phosphorylation or may be a distinct protein that only shares partial sequence similarity with that of occludin
Summary
Entamoeba histolytica is a protozoan parasite that colonizes the mucus barrier in the colon and can lead to amebiasis [1]. Many of the defined virulence factors disrupt colonic mucosal barrier integrity, tight junction proteins that result in diarrhea or more serious amebic dysentery [6]. The TJ is composed of a mosaic of proteins that form a semi-permeable paracellular diffusion barrier [7] These dynamic junctions consist of 40 different proteins that include occludin, claudins, zona occludens, junctional adhesion molecules (JAMS) and the coxsackievirus and adenovirus receptor (CAR) [7]. In a recent study [8], we demonstrated that prostaglandin E2 secreted by E. histolytica disrupted TJ by selectively affecting one of its components, claudin-4. This change increased paracellular permeability, leading to a leaky gut [8]. The exact mechanism how the parasite does this is unknown
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