title: Protection of epithelial barrier function by the Crohn's disease associated gene protein tyrosine phosphatase n2.
abstract: OBJECTIVE
  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 T(84) 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)-gamma increases PTPN2 expression and activity in IEC. Moreover, IFN-gamma-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-gamma-induced effects on PTPN2. Additionally, PTPN2 knockdown potentiates IFN-gamma-induced increases in epithelial permeability, accompanied by elevated expression of the pore-forming protein claudin-2.
  
  
  CONCLUSIONS
  PTPN2 is activated by IFN-gamma and limits IFN-gamma-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.
authors.affiliation: Division of Gastroenterology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0063, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Scharl
authors.forename: Gisela
authors.initials: G
authors.lastname: Paul
authors.forename: Achim
authors.initials: A
authors.lastname: Weber
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Jung
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Docherty
authors.forename: Martin
authors.initials: M
authors.lastname: Hausmann
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.forename: Kim E
authors.initials: KE
authors.lastname: Barrett
authors.forename: Declan F
authors.initials: DF
authors.lastname: McCole
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D001706:Biopsy; D015153:Blotting, Western; D016022:Case-Control Studies; D057167:Claudins; D003424:Crohn Disease / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D005260:Female; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D010539:Permeability; D010766:Phosphorylation; D011446:Prospective Studies; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013997:Time Factors
chemical_list: C491875:CLDN2 protein, human; D057167:Claudins; D008565:Membrane Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D007371:Interferon-gamma; D055372:AMP-Activated Protein Kinases; C516649:PTPN2 protein, human; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2