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Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation
Published on: August 21, 2017
Proteasome and peptidase function in MHC-class-I-mediated antigen presentation.
Peter Michael Kloetzel1, Ferry Ossendorp
1Institut für Biochemie, Charité-Medizinische Fakultät der Humboldt Universität zu Berlin, Monbijoustrasse 2, 10117 Berlin, Germany. p-m.Kloetzel@charite.de
Current Opinion in Immunology
|January 22, 2004
Summary
The proteasome system generates MHC-class-I peptides, but cytosolic aminopeptidases can hinder or aid this process. Tripeptidyl peptidase II (TPPII) may also generate specific MHC class I epitopes.
Area of Science:
- Immunology
- Proteostasis
- Molecular Biology
Background:
- MHC class I peptide generation is primarily driven by the proteasome.
- Interferon-gamma (IFN-gamma) modulates proteasome function by inducing immunoproteasome and PA28 synthesis.
- Defective ribosomal products are a significant source for proteasome-mediated antigen processing, yet antigen presentation remains inefficient.
Purpose of the Study:
- To investigate the role of cytosolic aminopeptidases in MHC class I antigen processing.
- To understand how enzymes like bleomycin hydrolase (BH), puromycin-sensitive aminopeptidase (PSA), thimet oligoendopeptidase (TOP), leucine aminopeptidase (LAP), and endoplasmic reticulum aminopeptidase 1 (ERAP 1) affect epitope liberation.
- To explore the potential involvement of tripeptidyl peptidase II (TPPII) in generating MHC class I epitopes.
Main Methods:
- Analysis of proteasome-dependent antigen processing pathways.
- Investigating the impact of immunoproteasomes and PA28 on epitope generation.
- Characterizing the activities of various cytosolic aminopeptidases on peptide precursors.
- Assessing the role of TPPII in MHC class I epitope formation.
Main Results:
- Cytosolic aminopeptidases can either degrade epitopes/precursors or trim them to the correct size for MHC class I binding.
- ERAP 1 and LAP enhance antigen presentation by processing epitope precursors.
- TPPII, with its exo- and endo-proteolytic activities, is implicated in generating a distinct set of MHC class I epitopes.
Conclusions:
- The efficiency of MHC class I antigen presentation is finely tuned by a balance of proteasomal activity and the actions of multiple aminopeptidases.
- Specific aminopeptidases play crucial roles in either diminishing or enhancing the pool of peptides available for MHC class I presentation.
- TPPII represents a novel player in antigen processing, potentially contributing unique epitopes to the MHC class I pathway.
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