title: A role for the proteasome regulator PA28alpha in antigen presentation.
abstract: Cytotoxic T cells recognize viral proteins as peptide fragments which are produced in the cytosol and transported on major histocompatibility complex (MHC) class I proteins to the cell surface. Viral peptides that meet the stringent binding characteristics of class I proteins are generated by the 20S proteasome. The interferon (IFN)-gamma-inducible activator of the 20S proteasome, PA28, strongly influences the proteasomal cleavage pattern in vitro. This led us to investigate whether changes in cellular levels of PA28 affect the efficiency of viral antigen processing. A mouse fibroblast line expressing the murine cytomegalovirus pp89 protein was transfected with either the human or murine gene encoding the PA28alpha subunit, which is sufficient to activate the peptide-hydrolysing activity of the 20S proteasome in vitro. Here we report that enhanced expression of PA28alpha at a level similar to that obtained after IFN-gamma induction resulted in a marked enhancement of recognition by pp89-specific cytotoxic T cells; the presentation of influenza nucleoprotein was also significantly improved. These results demonstrate a fundamental in vivo function for PA28alpha in antigen processing.
authors.affiliation: Institute for Biochemistry, Medical Faculty (Charité), Humboldt University, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Groettrup
authors.forename: A
authors.initials: A
authors.lastname: Soza
authors.forename: M
authors.initials: M
authors.lastname: Eggers
authors.forename: L
authors.initials: L
authors.lastname: Kuehn
authors.forename: T P
authors.initials: TP
authors.lastname: Dick
authors.forename: H
authors.initials: H
authors.lastname: Schild
authors.forename: H G
authors.initials: HG
authors.lastname: Rammensee
authors.forename: U H
authors.initials: UH
authors.lastname: Koszinowski
authors.forename: P M
authors.initials: PM
authors.lastname: Kloetzel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology / Q000502:physiology*; D001324:Autoantigens; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000502:physiology*; D003587:Cytomegalovirus / Q000276:immunology; D017931:DNA Primers; D004789:Enzyme Activation; D005434:Flow Cytometry; D006183:H-2 Antigens / Q000276:immunology; D064532:Histocompatibility Antigen H-2D; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000276:immunology; D009980:Influenza A virus / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000502:physiology*; D009124:Muscle Proteins; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014162:Transfection
chemical_list: D001324:Autoantigens; D017931:DNA Primers; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; D017874:Immediate-Early Proteins; C099558:Ki antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; C085047:PSME1 protein, human; D011506:Proteins; D011994:Recombinant Proteins; C052612:cytomegalovirus immediate early phosphoprotein pp89; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C486213:Psme1 protein, mouse