Immunoproteasomes Largely Replace Constitutive Proteasomes During an Antiviral and Antibacterial Immune Response in the Liver

Abstract

The proteasome is critically involved in the production of MHC class I-restricted T cell epitopes. Proteasome activity and epitope production are altered by IFN-γ treatment, which leads to a gradual replacement of constitutive proteasomes by immunoproteasomes in vitro. However, a quantitative analysis of changes in the steady state subunit composition of proteasomes during an immune response against viruses or bacteria in vivo has not been reported. Here we show that the infection of mice with lymphocytic choriomeningitis virus or Listeria monocytogenes leads to an almost complete replacement of constitutive proteasomes by immunoproteasomes in the liver within 7 days. Proteasome replacements were markedly reduced in IFN-γ−/− mice, but were only slightly affected in IFN-αR−/− and perforin−/− mice. The proteasome regulator PA28α/β was up-regulated, whereas PA28γ was reduced in the liver of lymphocytic choriomeningitis virus-infected mice. Proteasome replacements in the liver strongly altered proteasome activity and were unexpected to this extent, since an in vivo half-life of 12 days had been previously assigned to constitutive proteasomes in the liver. Our results suggest that during the peak phase of viral and bacterial elimination the antiviral cytotoxic T lymphocyte response is directed mainly to immunoproteasome-dependent T cell epitopes, which would be a novel parameter for the design of vaccines.

The immune status of Kupffer cells profoundly influences their responses to infectiousPlasmodium berghei sporozoites

“…Challenge of c-spz-immune mice maintained IL-12 production by KC, while exposure of naive mice to infectious spz failed to induce IL-12 in KC and INF-c in IHMC. Inflammatory cytokines enhance proteosome activity and hence availability of peptides for export by class I [26]. The increased class I on c-spz-immune KC might reflect a rapid/efficient export of recycling class I molecules because we observed no increase in K b heavy chain mRNA.…”

No evidence for immunoproteasomes in chicken lymphoid organs and activated lymphocytes

“…Notably, for the whole blood 20S proteasome, the trypsin-like activity was nearly twice as high compared to the other proteasomes and proteolytic activities. The chymotrypsin-and caspase-like activities were similar between proteasomes from the brain, whole blood, bursa of Fabricius, spleen, or thymus, while the human 20S immunoproteasome purified from the T cell lymphoblastoid line LCL721-145 (Salter and Cresswell 1986), which was tested in parallel, showed a strongly reduced caspase-like activity as would be expected for the replacement of β1 with β1i (LMP2) (Khan et al 2001). In contrary, 20S constitutive proteasome from the β1i-and β5i-deficient T cell lymphoblastoid line LCL721-174 (Salter and Cresswell 1986) showed very high caspase-like cleavage activity.…”

“…In complete brain tissue of the mouse, only constitutive 20S proteasome is visible in Coomassie-stained 2D gels (Kremer et al 2010). In contrast to the chicken spleen, in the mouse spleen, about equal amounts of constitutive 20S proteasome and 20S immunoproteasome was found and the immunoproteasome subunits β1i (LMP2), β2i (MECL-1), and β5i (LMP7) were readily visible on Coomassie-stained 2D gels and easily distinguished from the constitutive subunits β1, β2, and β5 due to marked differences in molecular mass and/or isoelectric point (Groettrup et al 1996;Khan et al 2001;Kremer et al 2010). To identify the subunits of chicken 20S proteasome from the brain and spleen and to exclude that putative immunosubunits migrated equally as constitutive ones, 18 spots were excised from 2D gels and were analyzed by mass spectrometry.…”

Bioinformatic analysis of functional differences between the immunoproteasome and the constitutive proteasome

“…During an antiviral or antibacterial immune response, immunoproteasomes largely replace constitutive proteasomes (Khan et al 2001). This replacement has a positive effect on MHC class I restricted antigen presentation, as has been demonstrated in several systems (see, for example, Kuckelkorn et al 1995;Ehring et al 1996;Morel et al 2000;Sijts et al 2000b;Van Hall et al 2000;Chen et al 2001;Khan et al 2001;Schultz et al 2002). The immunoproteasomes are not absolutely necessary to generate immunogenic epitopes, but immunodominant epitopes are mainly generated by the immunoproteasomes .…”

“…Thus two forms of proteasome exist: the "immunoproteasome", which is expressed in cells stimulated by gamma interferon (IFN-g) or tumor necrosis factor alpha (TNF-a), and in primary and secondary lymphoid organs, and the "constitutive proteasome", which is expressed in healthy, normal tissues and in immune-privileged organs such as the brain (Dahlmann et al 2000;Noda et al 2000;Kuckelkorn et al 2002). During an antiviral or antibacterial immune response, immunoproteasomes largely replace constitutive proteasomes (Khan et al 2001). This replacement has a positive effect on MHC class I restricted antigen presentation, as has been demonstrated in several systems (see, for example, Kuckelkorn et al 1995;Ehring et al 1996;Morel et al 2000;Sijts et al 2000b;Van Hall et al 2000;Chen et al 2001;Khan et al 2001;Schultz et al 2002).…”