Requirement of Cellular Prion Protein for Intestinal Barrier Function and Mislocalization in Patients With Inflammatory Bowel Disease

Abstract

Cell adhesion is one function regulated by cellular prion protein (PrP(c)), a ubiquitous, glycosylphosphatidylinositol-anchored glycoprotein. PrP(c) is located in cell-cell junctions and interacts with desmosome proteins in the intestinal epithelium. We investigated its role in intestinal barrier function. We analyzed permeability and structure of cell-cell junctions in intestine tissues from PrP(c) knockout (PrP(c-/-)) and wild-type mice. PrP(c) expression was knocked down in cultured human Caco-2/TC7 enterocytes using small hairpin RNAs. We analyzed colon samples from 24 patients with inflammatory bowel disease (IBD). Intestine tissues from PrP(c-/-) mice had greater paracellular permeability than from wild-type mice (105.9 ± 13.4 vs 59.6 ± 10.1 mg/mL fluorescein isothiocyanate-dextran flux; P < .05) and impaired intercellular junctions. PrP(c-/-) mice did not develop spontaneous disease but were more sensitive than wild-type mice to induction of colitis with dextran sulfate (32% mortality vs 4%, respectively; P = .0033). Such barrier defects were observed also in Caco-2/TC7 enterocytes following PrP(c) knockdown; the cells had increased paracellular permeability (1.5-fold over 48 hours; P < .001) and reduced transepithelial electrical resistance (281.1 ± 4.9 vs 370.6 ± 5.7 Ω.cm(2); P < .001). Monolayer shape and cell-cell junctions were altered in cultures of PrP(c) knockdown cells; levels of E-cadherin, desmoplakin, plakoglobin, claudin-4, occludin, zonula occludens 1, and tricellulin were decreased at cell contacts. Cell shape and junctions were restored on PrP(c) re-expression. Levels of PrP(c) were decreased at cell-cell junctions in colonic epithelia from patients with Crohn's disease or ulcerative colitis. PrP(c) regulates intestinal epithelial cell-cell junctions and barrier function. Its localization is altered in colonic epithelia from patients with IBD, supporting the concept that disrupted barrier function contributes to this disorder.