Immuno- and Constitutive Proteasome Crystal Structures Reveal Differences in Substrate and Inhibitor Specificity

Huber, E.M.; Basler, Michael; Schwab, Ricarda; Heinemeyer, Wolfgang; Kirk, Christopher J.; Groettrup, Marcus; Groll, M.

doi:10.1016/j.cell.2011.12.030

Cited by 438 publications

(686 citation statements)

References 68 publications

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“…As no class I molecules exist in the mouse and human that bind proteasome products with acidic C termini, LMP2 incorporation may have evolved to suppress the proteasomal caspase-like activity. This change in cleavage specificity is in perfect agreement with predictions based on the x-ray crystallographic structure of 20S proteasomes that anticipate that the S1 pocket of b1, which binds the C-terminal P1 residue of a peptide, contains a positively charged arginine as counter residue, which in b1i (LMP2) is replaced by a leucine, thus rendering the pocket more apolar and causing the observed loss of the caspase-like activity in immunoproteasomes (1,2).…”

Section: Discussionsupporting

confidence: 70%

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Why the Structure but Not the Activity of the Immunoproteasome Subunit Low Molecular Mass Polypeptide 2 Rescues Antigen Presentation

Basler

Lauer

Moebius

et al. 2012

The Journal of Immunology

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The proteasome is responsible for the generation of most epitopes presented on MHC class I molecules. Treatment of cells with IFN-γ leads to the replacement of the constitutive catalytic subunits β1, β2, and β5 by the inducible subunits low molecular mass polypeptide (LMP) 2 (β1i), multicatalytic endopeptidase complex-like-1 (β2i), and LMP7 (β5i), respectively. The incorporation of these subunits is required for the production of numerous MHC class I-restricted T cell epitopes. The structural features rather than the proteolytic activity of an immunoproteasome subunit are needed for the generation of some epitopes, but the underlying mechanisms have remained elusive. Experiments with LMP2-deficient splenocytes revealed that the generation of the male HY-derived CTL-epitope UTY246–254 was dependent on LMP2. Treatment of male splenocytes with an LMP2-selective inhibitor did not reduce UTY246–254 presentation, whereas silencing of β1 activity increased presentation of UTY246–254. In vitro degradation experiments showed that the caspase-like activity of β1 was responsible for the destruction of this CTL epitope, whereas it was preserved when LMP2 replaced β1. Moreover, inhibition of the β5 subunit rescued the presentation of the influenza matrix 58–66 epitope, thus suggesting that a similar mechanism can apply to the exchange of β5 by LMP7. Taken together, our data provide a rationale why the structural property of an immunoproteasome subunit rather than its activity is required for the generation of a CTL epitope.

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Section: Discussionsupporting

confidence: 70%

“…The proteasome is the major cytosolic endoprotease in eukaryotes consisting of a and b subunits that build a barrel-shaped complex of four rings with seven subunits each (called 20S proteasome) (1,2). The outer two rings consist of a subunits, the inner two rings of b subunits forming the central proteolytic chamber.…”

mentioning

confidence: 99%

Why the Structure but Not the Activity of the Immunoproteasome Subunit Low Molecular Mass Polypeptide 2 Rescues Antigen Presentation

Basler

Lauer

Moebius

et al. 2012

The Journal of Immunology

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“…The i-proteasome inhibitors are currently developed and tested. 51 Application of the PSMB8 selective inhibitor PR-957 in experimental arthritis or colitis could reduce cytokine production and attenuate disease activity. 10,14 On the other hand, the recently described mutations in PSMB8 15,[52][53][54] were all associated with decreased subunit activity and different inflammatory syndromes, suggesting that i-proteasome suppression may cause additional effects depending on dosage and cell type involved.…”

Section: Discussionmentioning

confidence: 99%

Therapeutic Potential of Immunoproteasome Inhibition in Duchenne Muscular Dystrophy

et al. 2016

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Duchenne muscular dystrophy is an inherited fatal genetic disease characterized by mutations in dystrophin gene, causing membrane fragility leading to myofiber necrosis and inflammatory cell recruitment in dystrophic muscles. The resulting environment enriched in proinflammatory cytokines, like IFN-γ and TNF-α, determines the transformation of myofiber constitutive proteasome into the immunoproteasome, a multisubunit complex involved in the activation of cell-mediate immunity. This event has a fundamental role in producing peptides for antigen presentation by MHC class I, for the immune response and also for cytokine production and T-cell differentiation. Here, we characterized for the first time the presence of T-lymphocytes activated against revertant dystrophin epitopes, in the animal model of Duchenne muscular dystrophy, the mdx mice. Moreover, we specifically blocked i-proteasome subunit LMP7, which was up-regulated in dystrophic skeletal muscles, and we demonstrated the rescue of the dystrophin expression and the amelioration of the dystrophic phenotype. The i-proteasome blocking lowered myofiber MHC class I expression and self-antigen presentation to T cells, thus reducing the specific antidystrophin T cell response, the muscular cell infiltrate, and proinflammatory cytokine production, together with muscle force recovery. We suggest that i-proteasome inhibition should be considered as new promising therapeutic approach for Duchenne muscular dystrophy pathology.

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“…1a). There is no available sequence for chicken β1 in the database; therefore, we first blasted murine β1 versus the chicken ESTs database (PubMed) and identified the cDNA sequence BX933198.1, which has all highly conserved amino acids typical for the catalytically active subunit β1 (Huber et al 2012). By MS analysis, β5 was identified as hypothetical protein RCJMB04 14i9 (Swiss-Prot database), which is 100 % identical to proteasome subunit alpha type-5 [Gallus gallus] ( N C B I R e f e r e n ce S eq u e n c e : N P 0 0 10 2 6 5 7 8 .1 ; refseq protein database).…”

Section: Identification Of Chicken Proteasome Subunits In Different Omentioning

confidence: 99%

“…The main form of proteasome is the so-called 26S proteasome comprised of the cylindric 20S core particle, responsible for the proteolytic activity, capped by the 19S regulator. The 20S proteasome is barrel-shaped and consists of 28 subunits with masses of 20-30 kDa arranged in four rings each comprising seven subunits (Huber et al 2012). The two outer rings of the cylinder are called the α rings containing subunits α1-7 and the two internal β rings contain subunits β1-7.…”

Section: Introductionmentioning

confidence: 99%

No evidence for immunoproteasomes in chicken lymphoid organs and activated lymphocytes

Erath

Groettrup

2014

Immunogenetics

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The proteasome is the main protein-degrading machine within the cell, producing ligands for MHC class I molecules. It is a cylindrical multicatalytic protease complex, and the catalytic activity is mediated by the three subunits β1, β2, and β5 which possess caspase-, trypsin-, and chymotrypsin-like activities, respectively. By stimulation with interferon (IFN)-γ the replacement of these subunits by β1i, β2i, and β5i is induced leading to formation of immunoproteasomes with altered proteolytic and antigen processing properties. The genes coding for these immunosubunits are restricted to jawed vertebrates but have so far not been found in the genomes of birds, e.g., chicken, turkey, quail, black grouse and zebra finch. However, the chicken genome sequences are not completely assigned; therefore, we investigated the presence of immunoproteasome on protein level. 20S proteasome was purified from the chicken brain, blood, spleen, and bursa of Fabricius, followed by separation via two-dimensional (2D) gel electrophoresis. We analyzed the protein spots derived from the spleen and brain by mass spectrometry and could identify all 14 proteasomal subunits, but there were no differences detectable in the spot patterns. Moreover, we stimulated the chicken spleen cells with phorbol 12-myristate 13-acetate (PMA) and ionomycin aiming at the induction of immunoproteasome, but in spite of the induction of proliferation and IFN-γ, no evidence for immunoproteasome formation in chicken could be obtained. This result was substantiated by the finding that 20S proteasomes isolated from immune and non-immune tissues showed very similar peptidolytic activities. Taken together, our results indicate that chicken lack immunoproteasomes also on protein level.

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Immuno- and Constitutive Proteasome Crystal Structures Reveal Differences in Substrate and Inhibitor Specificity

Cited by 438 publications

References 68 publications

Why the Structure but Not the Activity of the Immunoproteasome Subunit Low Molecular Mass Polypeptide 2 Rescues Antigen Presentation

Why the Structure but Not the Activity of the Immunoproteasome Subunit Low Molecular Mass Polypeptide 2 Rescues Antigen Presentation

Therapeutic Potential of Immunoproteasome Inhibition in Duchenne Muscular Dystrophy

No evidence for immunoproteasomes in chicken lymphoid organs and activated lymphocytes

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