title: Absence of SHIP-1 results in constitutive phosphorylation of tank-binding kinase 1 and enhanced TLR3-dependent IFN-beta production.
abstract: Autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, result from a loss of tolerance to self-antigens and immune-mediated injury precipitated by the overproduction of type I IFN and inflammatory cytokines. We have identified the inositol 5' phosphatase SHIP-1 as a negative regulator of TLR3-induced type I IFN production. SHIP-1-deficient macrophages display enhanced TLR-induced IFN-beta production, and overexpression of SHIP-1 negatively regulates the ability of TLR3 and its adaptor, Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta, to induce IFN-beta promoter activity, indicating that SHIP-1 negatively regulates TLR-induced IFN-beta production. Further dissection of the IFN-beta pathway implicates TANK-binding kinase 1 (TBK1) as the target for SHIP-1. Critically, in the absence of SHIP-1, TBK1 appears to be hyperphosphorylated both in unstimulated cells and following TLR3 stimulation. In addition, TBK1 appears to be constitutively associated with Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta and TNFR-associated factor 3 in SHIP-1 deficient cells, whereas in wild-type cells this association is inducible following TLR3 stimulation. In support of a role for SHIP-1 in regulating complex formation, confocal microscopy demonstrates that TBK1 distribution in the cell is significantly altered in SHIP-1-deficient cells, with more prominent endosomal staining observed, compared with wild-type controls. Taken together, our results point to SHIP-1 as a critical negative regulator of IFN-beta production downstream of TLR3 through the regulation of TBK1 localization and activity.
authors.affiliation: Molecular and Cellular Therapeutics, Royal College of Surgeons, Ireland Research Institute, Dublin 2, Ireland.
authors.forename: Joan Ní
authors.initials: JN
authors.lastname: Gabhann
authors.forename: Rowan
authors.initials: R
authors.lastname: Higgs
authors.forename: Kiva
authors.initials: K
authors.lastname: Brennan
authors.forename: Warren
authors.initials: W
authors.lastname: Thomas
authors.forename: Jacqueline E
authors.initials: JE
authors.lastname: Damen
authors.forename: Nadia
authors.initials: N
authors.lastname: Ben Larbi
authors.forename: Gerald
authors.initials: G
authors.lastname: Krystal
authors.forename: Caroline A
authors.initials: CA
authors.lastname: Jefferies
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D000077271:Imiquimod; D018836:Inflammation Mediators / Q000378:metabolism; D000072181:Inositol Polyphosphate 5-Phosphatases; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D016207:Cytokines; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D016328:NF-kappa B; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D016899:Interferon-beta; C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C000606430:INPP5D protein, human; C000606433:Inpp5d protein, mouse; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000077271:Imiquimod