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Immunology of a cancer mucin: Proteasomal processing and presentation of human MUC1 tandem repeat glycopeptides
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ninkovic, Tanja |
| Copyright Year | 2006 |
| Abstract | MUC1 is a human transmembrane and secreted glycoprotein expressed in numerous epithelial tissues; in breast cancer tissues MUC1 is aberrantly glycosylated and a soluble form in the sera of cancer patients� triggers weak immune responses. The stimulation of cellular immune responses toward tumor-associated MUC1 glycoprotein is a primary goal in immunotherapeutic anti-cancer strategies. For an effective activation of tumor-MUC1 specific T-cell repertoires the extracellular MUC1 antigen should be presented by host dendritic cells in a MHC-dependent way. The generation of MHC class I epitopes is mainly performed by immunoproteasomes of dendritic cells. We performed in vitro studies to address the questions whether glycosylated MUC1 peptides are cleaved by IPs, and in which way the position and structure of O-linked glycans control the site specificity of peptide cleavage. In our work S|A|P (N-terminal) and G|S|T (C-terminal) were identified as the major processing sites within the non-glycosylated MUC1. These sequences are parts of the MUC1 tandem repeat sequence (HGVTSAPDTRPAPGSTAPPA) which can be O-glycosylated on Thr and Ser residues. Glycosylation of the substrate in the close proximity of processing sites significantly reduced processing efficiency. Proteasomes were not able to digest glycopeptides carrying the Sialyl Gal-GalNAc glycan, often found in the tumor associated form on MUC1 glycoprotein. The best processed glycopeptide carried glycosylation on Thr of the central DTR motif, distant from major processing regions. The highest amount of glycosylated fragments with a potential to bind to the MHC class I groove was found in the digest of glycopeptides with glycosylation of Thr within the central DTR motif. Furthermore, the peptide SAPDTRPAPG glycosylated with GalNAc on Thr was identified in a cellular assay as an epitope with high affinity for the human HLA-A0201 allele. To confirm the processing pattern of MUC1 tandem repeat sequence obtained in vitro, cross-presentation of the MUC1 peptide on dendritic cells was performed, and eluted peptides from cell-derived exosomes corresponded to sequences found in vitro. These results indicate that design of a MUC1 glycopeptide based cancer vaccine should include glycopeptides with GalNAc on Thr of DTR motif, because of their efficient degradation by immunoproteasome, production of high amount of glycosylated 8- to 11-mers and potential generation of MHC class I binding SAPDTRPAPG-GalNAc epitope. For future work, immunisation of the MUC1 transgenic mice with DTR glycosylated peptides is in progress. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://kups.ub.uni-koeln.de/2073/1/Tanja_doktorat_za_stampanje.pdf |
| Alternate Webpage(s) | http://www.uni-koeln.de/med-fak/biochemie/dissertation/diss/tanja_ninkovic.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
