title: MHC class I antigen processing of an adenovirus CTL epitope is linked to the levels of immunoproteasomes in infected cells.
abstract: Proteasomes are the major source for the generation of peptides bound by MHC class I molecules. To study the functional relevance of the IFN-gamma-inducible proteasome subunits low molecular mass protein 2 (LMP2), LMP7, and mouse embryonal cell (MEC) ligand 1 in Ag processing and concomitantly that of immunoproteasomes, we established the tetracycline-regulated mouse cell line MEC217, allowing the titrable formation of immunoproteasomes. Infection of MEC217 cells with Adenovirus type 5 (Ad5) and analysis of Ag presentation with Ad5-specific CTL showed that cells containing immunoproteasomes processed the viral early 1B protein (E1B)-derived epitope E1B192-200 with increased efficiency, thus allowing a faster detection of viral entry in induced cells. Importantly, optimal CTL activation was already achieved at submaximal immunosubunit expression. In contrast, digestion of E1B-polypeptide with purified proteasomes in vitro yielded E1B192-200 at quantities that were proportional to the relative contents of immunosubunits. Our data provide evidence that the IFN-gamma-inducible proteasome subunits, when present at relatively low levels as at initial stages of infection, already increase the efficiency of antigenic peptide generation and thereby enhance MHC class I Ag processing in infected cells.
authors.affiliation: Institute of Biochemistry, Charité, Humboldt University, Berlin, Germany.
authors.forename: A J
authors.initials: AJ
authors.lastname: Sijts
authors.forename: S
authors.initials: S
authors.lastname: Standera
authors.forename: R E
authors.initials: RE
authors.lastname: Toes
authors.forename: T
authors.initials: T
authors.lastname: Ruppert
authors.forename: N J
authors.initials: NJ
authors.lastname: Beekman
authors.forename: P A
authors.initials: PA
authors.lastname: van Veelen
authors.forename: F A
authors.initials: FA
authors.lastname: Ossendorp
authors.forename: C J
authors.initials: CJ
authors.lastname: Melief
authors.forename: P M
authors.initials: PM
authors.lastname: Kloetzel
mesh_terms: D000260:Adenoviruses, Human / Q000235:genetics / Q000276:immunology*; D000276:Adjuvants, Immunologic / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D004306:Dose-Response Relationship, Immunologic; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D018984:Epitopes, T-Lymphocyte / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D010452:Peptide Biosynthesis / Q000276:immunology; D046988:Proteasome Endopeptidase Complex; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000276:Adjuvants, Immunologic; D018984:Epitopes, T-Lymphocyte; D015395:Histocompatibility Antigens Class I; D009097:Multienzyme Complexes; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D013752:Tetracycline