title: Interferon-gamma signals via an ERK1/2-ARF6 pathway to promote bacterial internalization by gut epithelia.
abstract: The barrier function of the epithelium lining the intestine is essential for health by preventing the free passage of colonic bacteria into the mucosa. Epithelia treated with interferon (IFN)-γ display increased bacteria transcytosis. Much is known of how IFNγ affects the tight junction and paracellular permeability, yet its role in modifying transcellular traffic of commensal bacteria remains poorly understood. Using immunoblotting, ELISA and immunolocalization, IFNγ was found to activate extracellular regulated kinase (ERK)1/2 in the human colon-like T84 epithelial cell line. Pharmacological inhibition of MEK/ERK1/2 signalling with U0126 significantly inhibited IFNγ-induced increases in the transcytosis of non-invasive Escherichia coli (strain HB101). IFNγ treatment enhanced epithelial internalization of E. coli, some of which subsequently escaped the enterocyte. Molecular analyses revealed that ERK1/2 inhibition prevented activation of the ADP-ribosylation factor (ARF)-6, a protein associated with endocytosis, and that siRNA knock-down of ARF6 expression reduced IFNγ-induced E. coli internalization into T84 cells. None of these interventions affected the drop in transepithelial resistance caused by IFNγ. Thus, increased transcellular passage may be a major component of IFNγ-induced increases in epithelial permeability, and ERK1/2 and ARF6 are presented as important molecules in IFNγ-evoked transcytosis of bacteria across gut epithelia.
authors.affiliation: Gastrointestinal Research Group, Department of Physiology & Pharmacology, The Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Calgary, Alberta, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Smyth
authors.forename: Catherine M
authors.initials: CM
authors.lastname: McKay
authors.forename: Brian D
authors.initials: BD
authors.lastname: Gulbransen
authors.forename: Van C
authors.initials: VC
authors.lastname: Phan
authors.forename: Arthur
authors.initials: A
authors.lastname: Wang
authors.forename: Derek M
authors.initials: DM
authors.lastname: McKay
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D017097:Electric Impedance; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism* / Q000382:microbiology; D004926:Escherichia coli / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology / Q000502:physiology*; D007413:Intestinal Mucosa / Q000166:cytology*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010539:Permeability; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors; D002070:Butadienes; D007371:Interferon-gamma; D020928:Mitogen-Activated Protein Kinases; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D051076:Proto-Oncogene Proteins c-fyn; C113580:U 0126; C494957:FYN protein, human; C000715348:ARF6 protein, human