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

BACKGROUND & AIMS: Cell adhesion is one function regulated by cellular prion protein (PrPc), a ubiquitous, glycosylphosphatidylinositol-anchored glycoprotein. PrPc is located in cell-cell junctions and interacts with desmosome proteins in the intestinal epithelium. We investigated its role in intestinal barrier function. METHODS: We analyzed permeability and structure of cell-cell junctions in intestine tissues from PrPc knockout (PrPc-/-) and wild-type mice. PrPc 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). RESULTS: Intestine tissues from PrPc-/- mice had greater paracellular permeability than from wildtype mice (105.9 +/- 13.4 vs 59.6 +/- 10.1 mg/mL fluorescein isothiocyanate-dextran flux; P < .05) and impaired intercellular junctions. PrPc-/- 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 PrPc 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 Omega.cm(2); P < .001). Monolayer shape and cell-cell junctions were altered in cultures of PrPc 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 PrPc re-expression. Levels of PrPc were decreased at cell-cell junctions in colonic epithelia from patients with Crohn's disease or ulcerative colitis. CONCLUSIONS: PrPc 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.