Microbiome-Mediated Disruption of Mucin Glycosylation and Mechanisms of Protease Activated Receptor-Dependent Modulation of Mucin Gene Expression During Giardia spp. Infection
Date
2022-09-26
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Abstract
Disruption of the intestinal mucus gel barrier has a significant impact on intestinal health and homeostasis. Mucus barrier alterations have been associated with dysbiosis, increased intestinal permeability, and increased susceptibility to intestinal infection. Giardia duodenalis is a leading cause of diarrheal disease in humans and has been linked to development of post-infectious functional gastrointestinal disorders. Giardia infection is associated with intestinal barrier dysfunction and altered composition and function of the commensal microbiome, both of which are predicted to contribute to acute and chronic disease manifestations. This study reveals new mechanisms by which Giardia and its secreted cysteine proteases can modulate goblet cell activity and the properties of the intestinal mucus barrier. Alterations to the glycosylation of intestinal mucins and the expression of mucin and mucin-associated glycosyltransferase genes were found to be time-dependent, appearing as early as day 2 post-infection, and persisting in mice that had cleared the infection. Alterations to glycan abundance and glycosyltransferase gene expression were observed not only in the small intestine, at the site of parasite colonization, but also in the distal colon, where no trophozoites are present. Many of these alterations were microbiome-dependent and were recapitulated in mice transplanted with small intestinal bacteria collected from Giardia infected mice. Alterations were also similar between the mouse-specific isolate Giardia muris, and the zoonotic isolate Giardia duodenalis GS/M. In human cell cultures, alterations to mucin gene expression were found to be dependent both on Giardia cysteine protease activity and on protease-activated receptor-2 signaling. Isolate-dependent effects on mucin gene expression correlated both with cysteine protease activity levels and with the cleavage of PAR2. MUC2 mucin gene upregulation was dependent on intracellular calcium mobilization and on activation of the ERK1/2 mitogen activated protein kinase pathway, indicating that Giardia proteases can cleave PAR2 at a tethered ligand activation site. The present findings demonstrate novel mechanisms by which Giardia alters the intestinal mucus barrier, potentially facilitating pathogen translocation and contributing to acute, chronic, and post-infectious disease manifestations.
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Giardia, Mucus, Glycosylation, Muc2, Glycan, Protease, PAR2, Microbiome, Goblet Cell
Citation
Fekete, E. (2022). Microbiome-mediated disruption of mucin glycosylation and mechanisms of protease activated receptor-dependent modulation of mucin gene expression during Giardia spp. infection (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.