Endoplasmic Reticulum Aminopeptidase Associated with Antigen Processing Defines the Composition and Structure of MHC Class I Peptide Repertoire in Normal and Virus-Infected Cells

• Published in: The Journal of immunology (1950) 2010-03, Vol.184 (6), p.3033-3042
• Main Authors: Blanchard, Nicolas, Kanaseki, Takayuki, Escobar, Hernando, Delebecque, Frederic, Nagarajan, Niranjana A, Reyes-Vargas, Eduardo, Crockett, David K, Raulet, David H, Delgado, Julio C, Shastri, Nilabh
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Amino Acid Sequence; Animals; Antigen Presentation - genetics; Antigen Presentation - immunology; CD8-Positive T-Lymphocytes - enzymology; CD8-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - virology; Endoplasmic Reticulum - enzymology; Endoplasmic Reticulum - immunology; Endoplasmic Reticulum - virology; Epitopes, T-Lymphocyte - chemistry; Epitopes, T-Lymphocyte - immunology; Epitopes, T-Lymphocyte - metabolism; H-2 Antigens - chemistry; H-2 Antigens - immunology; H-2 Antigens - metabolism; Histocompatibility Antigen H-2D; Hybridomas; Hydrolysis; Leucyl Aminopeptidase - deficiency; Leucyl Aminopeptidase - genetics; Leucyl Aminopeptidase - physiology; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Sequence Data; Muromegalovirus - immunology; Peptide Fragments - immunology; Peptide Fragments - metabolism; Protein Binding - genetics; Protein Binding - immunology; Tandem Mass Spectrometry; Viral Proteins - chemistry; Viral Proteins - immunology; Viral Proteins - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.0903712

The MHC class I (MHC-I) molecules ferry a cargo of peptides to the cell surface as potential ligands for CD8(+) cytotoxic T cells. For nearly 20 years, the cargo has been described as a collection of short 8-9 mer peptides, whose length and sequences were believed to be primarily determined by the peptide-binding groove of MHC-I molecules. Yet the mechanisms for producing peptides of such optimal length and composition have remained unclear. In this study, using mass spectrometry, we determined the amino acid sequences of a large number of naturally processed peptides in mice lacking the endoplasmic reticulum aminopeptidase associated with Ag processing (ERAAP). We find that ERAAP-deficiency changed the oeuvre and caused a marked increase in the length of peptides normally presented by MHC-I. Furthermore, we observed similar changes in the length of viral peptides recognized by CD8(+) T cells in mouse CMV-infected ERAAP-deficient mice. In these mice, a distinct CD8(+) T cell population was elicited with specificity for an N-terminally extended epitope. Thus, the characteristic length, as well as the composition of MHC-I peptide cargo, is determined not only by the MHC-I peptide-binding groove but also by ERAAP proteolysis in the endoplasmic reticulum.