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Why the Structure but Not the Activity of the Immunoproteasome Subunit Low Molecular Mass Polypeptide 2 Rescues Antigen Presentation.
MedLine Citation:
PMID:  22772448     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
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 UTY(246-254) was dependent on LMP2. Treatment of male splenocytes with an LMP2-selective inhibitor did not reduce UTY(246-254) presentation, whereas silencing of β1 activity increased presentation of UTY(246-254). 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.
Authors:
Michael Basler; Christoph Lauer; Jacqueline Moebius; Reinhold Weber; Michael Przybylski; Alexei F Kisselev; Christopher Tsu; Marcus Groettrup
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-6
Journal Detail:
Title:  Journal of immunology (Baltimore, Md. : 1950)     Volume:  -     ISSN:  1550-6606     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-9     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985117R     Medline TA:  J Immunol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Biotechnology Institute Thurgau, Constance University, CH-8280 Kreuzlingen, Switzerland;
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