title: Peptide anchor residue glycosylation: effect on class I major histocompatibility complex binding and cytotoxic T lymphocyte recognition.
abstract: This study extends our previous observation that glycopeptides bind to class I major histocompatibility complex (MHC) molecules and elicit carbohydrate-specific CTL responses. The Sendai virus nucleoprotein wild-type (WT) peptide (FAPGNYPAL) binds H-2Db using the P5-Asn as an anchor. The peptide K2 carrying a P5 serine substitution did not bind Db. Surprisingly, glycosylation of the serine (K2-O-GlcNAc) with N-acetylglucosamine (GlcNAc), a novel cytosolic O-linked glycosylation, partially restored peptide binding to Db. We argue that the N-acetyl group of GlcNAc may fulfil the hydrogen bonding requirements of the Db pocket which normally accomodates P5-Asn. Glycosylation of the P5-Asn residue itself abrogated binding similar to K2, probably for steric reasons. The peptide K2-O-GlcNAc readily elicited Db-restricted cytotoxic T lymphocytes (CTL), which did not cross-react with K2 or WT. However, all Db-restricted CTL raised against K2-O-GlcNAc cross-reacted strongly with another glycopeptide, K3-O-GlcNAc, where the GlcNAc substitution is on a neighboring P4-Ser. Furthermore, Db-restricted CTL clones raised against K2-O-GlcNAc or K3-O-GlcNAc displayed a striking TCR conservation. Our interpretation is that the carbohydrate of K2-O-GlcNAc not only mediates binding to Db, but also interacts with the TCR in such a way as to mimic K3-O-GlcNAc. This unusual example of molecular mimicry extends the known effects of peptide glycosylation from what we and others have previously reported: glycosylation may create a T cell neo-epitope, or, conversely, abrogate recognition. Alternatively, glycosylation may block peptide binding to MHC class I and finally, as reported here, restore binding, presumably through direct interaction of the carbohydrate with the MHC molecule.
authors.affiliation: Institute of Molecular Medicine, John Radcliffe Hospital, Oxford.
authors.forename: J S
authors.initials: JS
authors.lastname: Haurum
authors.forename: L
authors.initials: L
authors.lastname: Tan
authors.forename: G
authors.initials: G
authors.lastname: Arsequell
authors.forename: P
authors.initials: P
authors.lastname: Frodsham
authors.forename: A C
authors.initials: AC
authors.lastname: Lellouch
authors.forename: P A
authors.initials: PA
authors.lastname: Moss
authors.forename: R A
authors.initials: RA
authors.lastname: Dwek
authors.forename: A J
authors.initials: AJ
authors.lastname: McMichael
authors.forename: T
authors.initials: T
authors.lastname: Elliott
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D006020:Glycopeptides / Q000737:chemistry / Q000494:pharmacology; D006031:Glycosylation; D006183:H-2 Antigens / Q000737:chemistry* / Q000494:pharmacology*; D064532:Histocompatibility Antigen H-2D; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000276:immunology* / Q000494:pharmacology; D011485:Protein Binding / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D006020:Glycopeptides; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D064532:Histocompatibility Antigen H-2D; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D000117:Acetylglucosamine