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

FEBS Lett. 1994 Apr 18;343(1):85-8. doi: 10.1016/0014-5793(94)80612-8.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antigens / metabolism*
  • Cysteine Endopeptidases / chemistry
  • Cysteine Endopeptidases / metabolism*
  • Down-Regulation
  • Humans
  • Interferon-gamma / pharmacology*
  • Kidney / enzymology
  • Liver / enzymology
  • Molecular Sequence Data
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / metabolism*
  • Proteasome Endopeptidase Complex
  • Proteins / metabolism*
  • Sequence Homology, Amino Acid


  • Antigens
  • Multienzyme Complexes
  • Proteins
  • LMP-2 protein
  • Interferon-gamma
  • Cysteine Endopeptidases
  • LMP7 protein
  • PSMB5 protein, human
  • PSMB6 protein, human
  • Proteasome Endopeptidase Complex