title: Endoplasmic reticulum stress regulates the innate immunity critical transcription factor IRF3.
abstract: IFN regulatory factor 3 (IRF3) regulates early type I IFNs and other genes involved in innate immunity. We have previously shown that cells undergoing an endoplasmic reticulum (ER) stress response called the unfolded protein response produce synergistically augmented IFN-β when stimulated with pattern recognition receptor agonists such as LPS. Concomitant ER stress and LPS stimulation resulted in greater recruitment of the IRF3 transcription factor to ifnb1 gene regulatory elements. In this study, we used murine cells to demonstrate that both oxygen-glucose deprivation and pharmacologic unfolded protein response inducers trigger phosphorylation and nuclear translocation of IRF3, even in the absence of exogenous LPS. Different ER stressors used distinct mechanisms to activate IRF3: IRF3 phosphorylation due to calcium-mobilizing ER stress (thapsigargin treatment, oxygen-glucose deprivation) critically depended upon stimulator of IFN gene, an ER-resident nucleic acid-responsive molecule. However, calcium mobilization alone by ionomycin was insufficient for IRF3 phosphorylation. In contrast, other forms of ER stress (e.g., tunicamycin treatment) promote IRF3 phosphorylation independently of stimulator of IFN gene and TANK-binding kinase 1. Rather, IRF3 activation by tunicamycin and 2-deoxyglucose was inhibited by 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, a serine protease inhibitor that blocks activating transcription factor 6 processing. Interfering with ER stress-induced IRF3 activation abrogated IFN-β synergy. Together, these data suggest ER stress primes cells to respond to innate immune stimuli by activating the IRF3 transcription factor. Our results also suggest certain types of ER stress accomplish IRF3 phosphorylation by co-opting existing innate immune pathogen response pathways. These data have implications for diseases involving ER stress and type I IFN.
authors.affiliation: Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53792, USA.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Zeng
authors.forename: Austin
authors.initials: A
authors.lastname: Tian
authors.forename: Ashley
authors.initials: A
authors.lastname: Bomkamp
authors.forename: Daniel
authors.initials: D
authors.lastname: Rivera
authors.forename: Delia
authors.initials: D
authors.lastname: Gutman
authors.forename: Glen N
authors.initials: GN
authors.lastname: Barber
authors.forename: Julie K
authors.initials: JK
authors.lastname: Olson
authors.forename: Judith A
authors.initials: JA
authors.lastname: Smith
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000276:immunology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000276:immunology*; D007113:Immunity, Innate / Q000187:drug effects; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D007783:Lactones / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000502:physiology; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation / Q000187:drug effects / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D012717:Sesquiterpenes / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects / Q000276:immunology; D000099197:STING Protein
chemical_list: D050838:Interferon Regulatory Factor-3; D007783:Lactones; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D017346:Protein Serine-Threonine Kinases; D012717:Sesquiterpenes; C494233:Irf3 protein, mouse; C530855:Sting1 protein, mouse; D000099197:STING Protein; C046319:thapsigargicin; C498588:Tbk1 protein, mouse