title: pH dependence of MHC class I-restricted peptide presentation.
abstract: The function of MHC class I molecules is to bind and present antigenic peptides to cytotoxic T cells. Here, we report that class I-restricted peptide presentation is strongly pH dependent. The presentation of some peptides was enhanced at acidic pH, whereas the presentation of others was inhibited. Biochemical peptide-MHC class I binding assays demonstrated that peptide-MHC class I complexes are more stable at neutral pH than at acidic pH. We suggest that acid-dependent peptide dissociation can generate empty class I molecules and that the resulting binding potential can be exploited by a subset of peptide-MHC class I combinations, in some cases leading to considerable peptide exchange. We further speculate that the relative instability of peptide-class I complexes under acidic conditions may affect the outcome of class I-restricted Ag presentation, as less stably associated peptides may dissociate from class I during passage of the acidic trans-Golgi network, and therefore may not be presented. Finally, our results may in part explain how endocytosed proteins can be presented by MHC class I molecules to cytotoxic T cells.
authors.affiliation: Institute for Medical Microbiology and Immunology, Copenhagen, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Stryhn
authors.forename: L O
authors.initials: LO
authors.lastname: Pedersen
authors.forename: T
authors.initials: T
authors.lastname: Romme
authors.forename: A C
authors.initials: AC
authors.lastname: Olsen
authors.forename: M H
authors.initials: MH
authors.lastname: Nissen
authors.forename: C J
authors.initials: CJ
authors.lastname: Thorpe
authors.forename: S
authors.initials: S
authors.lastname: Buus
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000502:physiology*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006825:Hybridomas; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology* / Q000378:metabolism; D011485:Protein Binding; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014407:Tumor Cells, Cultured
chemical_list: D015395:Histocompatibility Antigens Class I; D010455:Peptides