title: A third interferon-gamma-induced subunit exchange in the 20S proteasome.
abstract: The 20S proteasome is a protease complex of functional importance for antigen processing. Two of the 14 proteasome subunits, delta and MB1, can be replaced by the major histocompatibility complex (MHC)-encoded and interferon-gamma (IFN-gamma)-inducible subunits LMP2 and LMP7, respectively. LMP2 and LMP7 alter the cleavage site specificity of the 20S proteasome and are required for the efficient generation of T cell epitopes from a number of viral proteins and for optimal MHC class I cell surface expression. We compared the 20S proteasome subunit pattern from IFN-gamma-induced and non-induced mouse fibroblasts on two-dimensional gels and identified a third subunit exchange by microsequencing: the non-MHC-encoded subunit MECL-1 is induced by IFN-gamma and replaces a sofar barely characterized beta subunit designated 'MC14'. In analogy to LMP2 and LMP7, MECL-1 may be functional in MHC class I-restricted antigen presentation.
authors.affiliation: Institute for Biochemistry, Medical Faculty (Charité), Humboldt University, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Groettrup
authors.forename: R
authors.initials: R
authors.lastname: Kraft
authors.forename: S
authors.initials: S
authors.lastname: Kostka
authors.forename: S
authors.initials: S
authors.lastname: Standera
authors.forename: R
authors.initials: R
authors.lastname: Stohwasser
authors.forename: P M
authors.initials: PM
authors.lastname: Kloetzel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D007371:Interferon-gamma / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*; D011994:Recombinant Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D015395:Histocompatibility Antigens Class I; D009097:Multienzyme Complexes; D011506:Proteins; D011994:Recombinant Proteins; C071313:LMP-2 protein; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex; C490920:Psmb10 protein, mouse