A novel role of SLC26A3 in maintenance of intestinal epithelial barrier integrity.

The Down Regulated in Adenoma (DRA) encoded by SLC26A3, a key intestinal chloride anion exchanger, has recently been identified as a novel susceptibility gene for inflammatory bowel disease (IBD). However, the mechanisms underlying the increased susceptibility to inflammation induced by the loss of DRA remain elusive.Compromised barrier is a key event in IBD pathogenesis, the current studies were undertaken to elucidate the impact of DRA deficiency on epithelial barrier integrity and to define underlying mechanisms.WT and DRA KO mice and crypt-derived colonoids were used as models for intestinal epithelial response. Paracellular permeability was measured using FITC (Fluorescein Isothiocyanate)-dextran flux. Immunoblotting, immunofluorescence, immunohistochemistry and RNP-IP (Ribonucleoprotein Immunoprecipitation) assays were performed. Gut microbiome analysis was conducted to demonstrate the role of DRA deficiency on gut microbial communities.DRA KO mice exhibited an increased colonic paracellular permeability with significantly decreased levels of tight junction/adherens junction (TJ/AJ) proteins, including ZO-1, occludin and E-cadherin. A similar expression pattern of occludin and E-cadherin was observed in colonoids derived from DRA KO mice and shRNA-mediated DRA knock-down in Caco-2 cells. Microbial analysis showed gut dysbiosis in DRA KO mice. However, cohousing studies showed that dysbiosis only played a partial role in maintaining TJ protein expression. Furthermore, our results showed increased binding of RNA-binding protein CUGBP1 with occludin and E-cadherin genes in DRA KO mouse colon, suggesting post-transcriptional mechanisms play a key role in gut barrier dysfunction.Our studies demonstrate a novel role of DRA in maintaining the intestinal epithelial barrier function and potential implications of its dysregulation in IBD pathogenesis.

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