Identification of O-glycosylated decapeptides within the MUC1 repeat domain as potential MHC class I (A2) binding epitopes.
The MUC1 glycoprotein is considered a tumor antigen due to its over expression and aberrant glycosylation in cancer tissues. The latter results in appearance of new antigenic tumor specific glycopeptides not found on normal glycoforms of the mucin. MUC1 glycopeptides can be presented by APCs on MHC class II molecules to activate glycopeptide specific helper T-cells. No study has yet reported presentation of MUC1 glycopeptides on MHC class I molecules as stimulators of cytotoxic T-cells. In this study we show that human immunoproteasomes and cathepsin-L can generate octa to undecameric glycopeptides from the MUC1 repeat domain in vitro. We identified glycosylated fragments of which the decameric glycopeptide SAP10 [SAPDT(GalNAc)RPAPG] containing a single sugar binds with comparable strength to the MHC class I allele HLA A*0201 as predicted high-score binding epitopes of the tandem repeat. The same sequence glycosylated with the disaccharide Gal-GalNAc does not bind. The glycan on SAP10 is predicted by molecular modeling to either protrude out or point into the MHC groove. SAPDTRPAPG peptide and the respective glycopeptide stimulated cytotoxic T-cells in vitro. Our findings suggest that MUC1 tandem repeat glycopeptides are capable of activating both helper and cytotoxic T-cells and thus represent good candidates for further development as vaccines.
Ninkovic
Tanja
T
Center of Biochemistry, Medical Faculty, and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany.
Kinarsky
Leo
L
Engelmann
Katja
K
Pisarev
Vladimir
V
Sherman
Simon
S
Finn
Olivera J
OJ
Hanisch
Franz-Georg
FG
D000595:Amino Acid Sequence; D056668:Cathepsin L / Q000378:metabolism; D000939:Epitopes; D006020:Glycopeptides / Q000276:immunology; D006031:Glycosylation; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D006801:Humans; D018396:Mucin-1 / Q000276:immunology* / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D014612:Vaccines
D000939:Epitopes; D006020:Glycopeptides; D015395:Histocompatibility Antigens Class I; D018396:Mucin-1; D010446:Peptide Fragments; D014612:Vaccines; D056668:Cathepsin L; D046988:Proteasome Endopeptidase Complex