Allele-selective effect of PA28 in MHC class I antigen processing

Taketoshi Yamano, Hidetoshi Sugahara, Shusaku Mizukami, Shigeo Murata, Tomoki Chiba, Keiji Tanaka, Katsuyuki Yui, Heiichiro Udono

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


PA28 is an IFN-γ-inducible proteasome activator and its genetic ablation causes complete loss of processing of certain Ags, but not all of them. The reason why this occurs and how PA28 influences the formation of peptide repertoires for MHC class I molecules remains unknown. In this study, we show the allele-specific role of PA28 in Ag processing. Retrovirus-transduced overexpression of PA28α decreased expression of Kd (D d) while it increased Kb and Ld on the cell surface. By contrast, overexpression of PA28αΔC5, a mutant carrying a deletion of its five C-terminal residues and capable of attenuating the activity of endogenous PA28, produced the opposite effect on expression of those MHC class I molecules. Moreover, knockdown of both PA28α and β by small-interfering RNA profoundly augmented expression of Kd and Dd, but not of Ld, on the cell surface. Finally, we found that PA28-associated proteasome preferentially digested within epitopic sequences of Kd, although correct C-terminal flankings were removed, which in turn hampered production of Kd ligands. Our results indicate that whereas PA28 negatively influences processing of Kd (Dd) ligands, thereby, down-regulating Ag presentation by those MHC class I molecules, it also efficiently produces Kb (Ld) epitopes, leading to up-regulation of the MHC molecules.

Original languageEnglish
Pages (from-to)1655-1664
Number of pages10
JournalJournal of Immunology
Issue number3
Publication statusPublished - Aug 1 2008
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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