title: Reduced immunoproteasome formation and accumulation of immunoproteasomal precursors in the brains of lymphocytic choriomeningitis virus-infected mice.
abstract: Tissue inflammation is accompanied by the cytokine-mediated replacement of constitutive proteasomes by immunoproteasomes that finally leads to an optimized generation of MHC class I restricted epitopes for Ag presentation. The brain is considered an immunoprivileged organ, where both the special anatomy as well as active tolerance mechanisms repress the development of inflammatory responses and help to prevent immunopathological damage. We analyzed the immunoproteasome expression in the brain after an infection with lymphocytic choriomeningitis virus (LCMV) and could show that LCMV-infection of mice leads to the transcriptional induction of inducible proteasome subunits in the brain. However, compared with other organs, i.p. and even intracranial infection with LCMV only led to a faint expression of mature immunoproteasome in the brain and resulted in the accumulation of immunoproteasomal precursors. By immunohistology, we could identify microglia-like cells as the main producers of immunoproteasome, whereas in astrocytes immunoproteasome expression was almost exclusively restricted to nuclei. Neither the immunoproteasome subunits low molecular mass polypeptide 2 nor multicatalytic endopeptidase complex-like-1 were detected in neurons or oligodendrocytes. In vitro studies of IFN-γ-stimulated primary astrocytes suggested that the observed accumulation of immunoproteasomal precursor complexes takes place in this cell population. Functionally, the lack of immunoproteasomes protracted and lowered the severity of LCMV-induced meningitis in LMP7(-/-) mice suggesting a contribution of immunoproteasomes in microglia to exacerbate immunopathological damage. We postulate a posttranslationally regulated mechanism that prevents abundant and inappropriate immunoproteasome assembly in the brain and may contribute to the protection of poorly regenerating cells of the CNS from immunopathological destruction.
authors.affiliation: Division of Immunology, Department of Biology, Constance University, Konstanz, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Kremer
authors.forename: Anja
authors.initials: A
authors.lastname: Henn
authors.forename: Cornelia
authors.initials: C
authors.lastname: Kolb
authors.forename: Michael
authors.initials: M
authors.lastname: Basler
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Moebius
authors.forename: Benoît
authors.initials: B
authors.lastname: Guillaume
authors.forename: Marcel
authors.initials: M
authors.lastname: Leist
authors.forename: Benoît J
authors.initials: BJ
authors.lastname: Van den Eynde
authors.forename: Marcus
authors.initials: M
authors.lastname: Groettrup
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000276:immunology / Q000378:metabolism; D015153:Blotting, Western; D001921:Brain / Q000276:immunology* / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000096:biosynthesis* / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D008216:Lymphocytic Choriomeningitis / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017628:Microglia / Q000276:immunology / Q000378:metabolism; D009474:Neurons / Q000276:immunology / Q000378:metabolism; D009836:Oligodendroglia / Q000276:immunology / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000096:biosynthesis* / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C071313:LMP-2 protein; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex