Protection of Epithelial Barrier Function by the Crohn's Disease Associated Gene Protein Tyrosine Phosphatase N2

Background & Aims

Protein tyrosine phosphatase N2 (PTPN2) has been identified as a Crohn's disease (CD) candidate gene. However, a role for PTPN2 in the pathogenesis of CD has not been identified. Increased permeability of the intestinal epithelium is believed to contribute prominently to CD. The aim of this study was to determine a possible role for PTPN2 in CD pathogenesis.

Methods

Intestinal epithelial cell (IEC) lines T84 and HT29cl.19a were used in all studies. Protein analysis was performed by Western blotting, and protein knockdown was induced by small interfering RNA. Primary samples were from control and CD patients.

Results

Here, we demonstrate increased PTPN2 expression in CD intestinal biopsy specimens and that the proinflammatory cytokine interferon (IFN)-γ increases PTPN2 expression and activity in IEC. Moreover, IFN-γ-induced STAT1 and STAT3 phosphorylation in IEC is enhanced by PTPN2 knockdown. The cellular energy sensor adenosine monophosphate-activated protein kinase partially regulates the IFN-γ-induced effects on PTPN2. Additionally, PTPN2 knockdown potentiates IFN-γ-induced increases in epithelial permeability, accompanied by elevated expression of the pore-forming protein claudin-2.

Conclusions

PTPN2 is activated by IFN-γ and limits IFN-γ-induced signalling and consequent barrier defects. These data suggest a functional role for PTPN2 in maintaining the intestinal epithelial barrier and in the pathophysiology of CD.

Abbreviations used in this paper: AICAR, 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside, AMPK, adenosine monophosphate-activated protein kinase, CC, compound C, CD, Crohn's disease, FITC, fluorescein isothiocyanate, IBD, inflammatory bowel disease, IEC, intestinal epithelial cells, IFN-γ, interferon γ, mRNA, messenger RNA, PTP, protein tyrosine phosphatase, PTPN2, protein tyrosine phosphatase N2, siRNA, small interfering RNA, SNP, single nucleotide polymorphism, STAT, signal transducer and activator of transcription, TC-PTP, T-cell protein tyrosine phosphatase, TER, transepithelial electrical resistance, TNF, tumor necrosis factor, UC, ulcerative colitis