Interferon y Stimulation Modulates the Proteolytic Activity and Cleavage Site Preference of 20S Mouse Proteasomes

Boes, Bettina and Hengel, Hartmut and Ruppert, Thomas and Multhaupt, Gerd and Koszinowski, Ulrich H. and Kloetzel, Peter-M. (1994): Interferon y Stimulation Modulates the Proteolytic Activity and Cleavage Site Preference of 20S Mouse Proteasomes. In: The journal of experimental medicine, Vol. 179: pp. 901-909

Abstract

The proteasome is a 700-kD multisubunit enzyme complex with several proteolytically active sites. The enzyme complex is involved in both ubiquitin-dependent and -independent protein degradation and may contribute to the processing of antigens presented by major histocompatibility complex (MHC) class I molecules. Here we demonstrate that treatment of mouse fibroblast cells with 20 U interferon qr (IFN-y) for 3 d induces a change in the proteasome subunit composition and that the B-type subunit LMP2, which is encoded in the MHC class II region, is incorporated into the enzyme complex. This is paralleled by reduction of the homologous 6-subunit. IFN-3' stimulation results in a downregulation of the chymotrypsin-like Suc-LLVY-MCA peptide hydrolyzing activity of 20S proteasomes whereas the trypsin-like activity remains unaffected. When tested as a substrate a synthetic 25-mer polypeptide whose sequence covers the antigenic nonapeptide YPHFMPTNL of the MCMV pp89, 20S proteasomes of IFN-3'-induced cells exhibit altered chymotrypsin-like cleavage site preferences. In the absence of IFN-qr induction, the naturally processed nonamer peptide that is presented by MHC class.I molecules appears as a minor cleavage product. IFN-'y activation does not result in an increase of the final peptide but results in a different set of peptides. We hypothesize that these peptides represent precursor peptides that can be trimmed to final peptide size.

• Item Type: Article
• Collections: Medicine
• Subjects: 600 Technology > 610 Medicine and health