Extended O-GlcNAc on HLA Class-I-Bound Peptides.
We report unexpected mass spectrometric observations of glycosylated human leukocyte antigen (HLA) class I-bound peptides. Complemented by molecular modeling, in vitro enzymatic assays, and oxonium ion patterns, we propose that the observed O-linked glycans carrying up to five monosaccharides are extended O-GlcNAc's rather than GalNAc-initiated O-glycans. A cytosolic O-GlcNAc modification is normally terminal and does not extend to produce a polysaccharide, but O-GlcNAc on an HLA peptide presents a special case because the loaded HLA class I complex traffics through the endoplasmic reticulum and Golgi apparatus on its way to the cell membrane and is hence exposed to glycosyltransferases. We also report for the first time natural HLA class I presentation of O- and N-linked glycopeptides derived from membrane proteins. HLA class I peptides with centrally located oligosaccharides have been shown to be immunogenic and may thus be important targets for immune surveillance.
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.|Netherlands Proteomics Centre, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Fabio
F
Marino
Protein Metrics Inc., San Carlos, CA 94070.
Marshall
M
Bern
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.|Netherlands Proteomics Centre, Padualaan 8, 3584 CH Utrecht, The Netherlands.|Institute for Translational Vaccinology, Bilthoven, Netherlands.
Geert P M
GPM
Mommen
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.|Netherlands Proteomics Centre, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Aneika C
AC
Leney
Centre for Infectious Disease Control, National Institute for Public Health and the Environment, The Netherlands.
Jacqueline A M
JAM
van Gaans-van den Brink
Computational Structural Biology, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Alexandre M J J
AMJJ
Bonvin
Protein Metrics Inc., San Carlos, CA 94070.
Christopher
C
Becker
Centre for Infectious Disease Control, National Institute for Public Health and the Environment, The Netherlands.
Cécile A C M
CACM
van Els
Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.|Netherlands Proteomics Centre, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Albert J R
AJR
Heck
D000117:Acetylglucosamine / Q000737:chemistry*; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism
D015395:Histocompatibility Antigens Class I; D010455:Peptides; D000117:Acetylglucosamine