title: AMP-18 facilitates assembly and stabilization of tight junctions to protect the colonic mucosal barrier.
abstract: BACKGROUND
  Inflammatory bowel disease (IBD) is characterized by an injured epithelium. Development of agents that could enhance mucosal healing is a major goal in IBD therapeutics. The 18-kDa antrum mucosal protein (AMP-18) and a 21-mer peptide derived from AMP-18 stimulate accumulation of tight junction (TJ) proteins in cultured epithelial cells and mouse colonic mucosa to protect the mucosal barrier, suggesting it might be a useful agent to treat IBD.
  
  
  METHODS
  We searched for molecular mechanisms by which AMP peptide or recombinant AMP-18 act on TJs in intact cell monolayers, or those disrupted by low-calcium medium. Roles of the p38 mitogen-activated protein kinase (MAPK) / heat shock protein (hsp)25 pathway and PKCζ were investigated by immunoblotting and confocal microscopy.
  
  
  RESULTS
  AMP peptide activated p38 MAPK, which subsequently phosphorylated hsp25. Accumulated phospho-hsp25 was associated with perijunctional actin. AMP-18 also induced rapid phosphorylation of PKCζ and its colocalization with perijunctional actin in Caco2/bbe cells, which was accompanied by translocation and formation of complexes of "polarity proteins" in the TJ-containing detergent-insoluble fraction. Treatment with AMP-18 also stimulated accumulation of ZO-1, ZO-2, and JAM-A in nascent TJs known to associate with the multimeric p-PKCζ/Par6/ Cdc42/ECT2·GTP/Par3 polarity protein complex.
  
  
  CONCLUSIONS
  AMP-18 facilitates translocation and assembly of multiple proteins into TJs and their association with and subsequent stabilization of the actin filament network. We speculate that improved barrier function induced by AMP-18 is mediated by enhanced TJ assembly. Thus, AMP-18 may provide a promising lead to develop agents effective in healing injured colonic epithelium in IBD.
authors.affiliation: Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Peili
authors.initials: P
authors.lastname: Chen
authors.forename: Sreedharan
authors.initials: S
authors.lastname: Kartha
authors.forename: Marc
authors.initials: M
authors.lastname: Bissonnette
authors.forename: John
authors.initials: J
authors.lastname: Hart
authors.forename: F Gary
authors.initials: FG
authors.lastname: Toback
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control*; D003106:Colon / Q000293:injuries / Q000378:metabolism / Q000473:pathology*; D016264:Dextran Sulfate / Q000633:toxicity; D019084:Fluorescent Antibody Technique, Indirect; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins; D006801:Humans; D007413:Intestinal Mucosa / Q000293:injuries / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018832:Molecular Chaperones; D010446:Peptide Fragments / Q000378:metabolism*; D036361:Peptide Hormones / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D019108:Tight Junctions / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D002118:Calcium; D016264:Dextran Sulfate; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010446:Peptide Fragments; D036361:Peptide Hormones; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D000099221:Protein Kinase C zeta; C477000:GKN1 protein, human; C057725:HSPB1 protein, human