Protection of Epithelial Barrier Function by the Crohn's Disease Associated Gene Protein Tyrosine Phosphatase N2
Received 11 August 2008; accepted 31 July 2009. published online 09 October 2009.
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.
⁎Division of Gastroenterology, University of California, San Diego, School of Medicine, La Jolla, California
‡Department of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
§Department of Pathology, Institute of Surgical Pathology, University Hospital Zurich, Zurich, Switzerland
Reprint requests Address requests for reprints to: Declan F. McCole, PhD, Division of Gastroenterology, School of Medicine, University of California, San Diego, 9500 Gilman Drive-0063, La Jolla, California 92093-0063. fax: (858) 534 3338
Conflicts of interest The authors disclose no conflicts.
FundingSupported by a Crohn's and Colitis Foundation of America Senior Research Award (to D.F.M.); a Jon I. Isenberg Award (to D.F.M.); grants from the German Research Foundation (DFG) (to M.S. and G.P.); NIH grant DK28305 (to K.E.B.); an unrestricted research gift from the Shape-Up Settlement fund (to K.E.B.); and by the University of California, San Diego, Digestive Diseases Research Development Center (DK080506).
ABSTRACT
Protection of Epithelial Barrier Function by the Crohn's Disease Associated Gene Protein Tyrosine Phosphatase N2