title: Replacement of proteasome subunits X and Y by LMP7 and LMP2 induced by interferon-gamma for acquirement of the functional diversity responsible for antigen processing.
abstract: Proteasomes catalyze the non-lysosomal, ATP-dependent selective breakdown of ubiquitinated proteins and are thought to be responsible for MHC class I-restricted antigen presentation. Recently, we reported that gamma interferon (IFN-gamma) induced not only marked synthesis of the MHC-encoded proteasome subunits LMP2 and LMP7, but also almost complete loss of two unidentified proteasome subunits tentatively designated as X and Y in various human cells. Here, we show that subunit X is a new proteasomal subunit highly homologous to LMP7, and that subunit Y is identical to the LMP2-related proteasomal subunit delta. Thus, IFN-gamma appears to induce subunit replacements of X and Y by LMP7 and LMP2, respectively, producing 'immuno-proteasomes' with the functional diversity responsible for processing of endogenous antigens.
authors.affiliation: Department of Urology, School of Medicine, University of Tokushima, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Akiyama
authors.forename: S
authors.initials: S
authors.lastname: Kagawa
authors.forename: T
authors.initials: T
authors.lastname: Tamura
authors.forename: N
authors.initials: N
authors.lastname: Shimbara
authors.forename: M
authors.initials: M
authors.lastname: Takashina
authors.forename: P
authors.initials: P
authors.lastname: Kristensen
authors.forename: K B
authors.initials: KB
authors.lastname: Hendil
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: A
authors.initials: A
authors.lastname: Ichihara
mesh_terms: D000595:Amino Acid Sequence; D000941:Antigens / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015536:Down-Regulation; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D000941:Antigens; D009097:Multienzyme Complexes; D011506:Proteins; C071313:LMP-2 protein; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; C088874:PSMB5 protein, human; C088875:PSMB6 protein, human; D046988:Proteasome Endopeptidase Complex