title: Interferon-gamma induces internalization of epithelial tight junction proteins via a macropinocytosis-like process.
abstract: Increased epithelial permeability is observed in inflammatory states. However, the mechanism by which inflammatory mediators such as IFN-gamma increase epithelial permeability is unknown. We recently observed that IFN-gamma induces disassembly of tight junctions (TJ); in this study we asked whether such TJ disassembly is mediated by endocytosis of junctional proteins. The role of three major internalization pathways in disruption of TJ in IFN-gamma-treated intestinal epithelial cells was analyzed using selective inhibitors and markers of the pathways. No role for the clathrin- and caveolar-mediated endocytosis in the IFN-gamma-induced internalization of TJ proteins was observed. However, inhibitors of macropinocytosis blocked internalization of TJ proteins and junctional proteins colocalized with macropinocytosis markers, dextran and phosphatidylinositol-3,4,5-trisphosphate. Internalized TJ proteins were identified in early and recycling endosomes but not in late endosomes/lysosomes. These results for the first time suggest that IFN-gamma produces a leaky epithelial barrier by inducing macropinoytosis of TJ proteins.
authors.affiliation: Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bruewer
authors.forename: Markus
authors.initials: M
authors.lastname: Utech
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Ivanov
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hopkins
authors.forename: Charles A
authors.initials: CA
authors.lastname: Parkos
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
mesh_terms: D021941:Caveolae / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D022163:Clathrin-Coated Vesicles / Q000187:drug effects / Q000378:metabolism; D003911:Dextrans / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects*; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D004848:Epithelium / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007371:Interferon-gamma / Q000494:pharmacology*; D007422:Intestines / Q000648:ultrastructure; D008247:Lysosomes / Q000737:chemistry; D016253:Microscopy, Immunoelectron; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010873:Pinocytosis / Q000187:drug effects; D011506:Proteins / Q000032:analysis / Q000378:metabolism*; D019108:Tight Junctions / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D003911:Dextrans; D018129:Phosphatidylinositol Phosphates; D011506:Proteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D007371:Interferon-gamma