title: Stress granule formation mediates the inhibition of colonic Hsp70 translation by interferon-gamma and tumor necrosis factor-alpha.
abstract: Mucosal inflammation, through cytokines such as interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), has many effects on the intestinal epithelium, including selective translational inhibition of the cytoprotective protein heat shock protein 70 (Hsp70). To further elucidate the mechanisms underlying this effect, we examined the role of stress granules in mediating the actions of these proinflammatory cytokines. Using conditionally immortalized young adult mouse colonic epithelial cells, we demonstrate that IFN-gamma and TNF-alpha, which upregulate eukaryotic initiation factor-alpha (eIF-2alpha) phosphorylation and reduce Hsp70 translation, significantly enhance stress granule formation in heat-shocked intestinal epithelial cells. The IFN-gamma and TNF-alpha effects in upregulation of stress granule formation and downregulation of Hsp70 were eIF-2alpha dependent, and the effect could be negated by blocking eIF-2alpha phosphorylation with use of an RNA-dependent protein kinase inhibitor. Correspondingly, IFN-gamma and TNF-alpha increased binding of cytoplasmic proteins to the 3'-untranslated region of Hsp70 mRNA, suggesting specific recruitment of Hsp70 to stress granules as the mechanism of IFN-gamma and TNF-alpha inhibition of Hsp70 translation. We thus report a novel linkage between inflammatory cytokine production, stress granule formation, and Hsp70 translation inhibition, providing additional insights into the response of intestinal epithelial cells to inflammatory stress.
authors.affiliation: The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Shien
authors.initials: S
authors.lastname: Hu
authors.forename: Erika C
authors.initials: EC
authors.lastname: Claud
authors.forename: Mark W
authors.initials: MW
authors.lastname: Musch
authors.forename: Eugene B
authors.initials: EB
authors.lastname: Chang
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D002461:Cell Line, Transformed; D003106:Colon / Q000166:cytology; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000502:physiology*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D007371:Interferon-gamma / Q000494:pharmacology*; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D000074019:T-Cell Intracellular Antigen-1; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors
chemical_list: D020413:3' Untranslated Regions; D015852:Eukaryotic Initiation Factor-2; D039561:Eukaryotic Initiation Factor-4E; D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D000074019:T-Cell Intracellular Antigen-1; C499367:Tia1 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D019892:eIF-2 Kinase