Center of Biochemistry, Medical Faculty, and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany.
Mol Immunol. 2009 Nov;47(1):131-40. doi: 10.1016/j.molimm.2008.09.032. Epub 2008 Nov 12.
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.
黏蛋白 1（MUC1）糖蛋白因其在癌症组织中的过度表达和异常糖基化而被认为是一种肿瘤抗原。后者导致出现新的抗原性肿瘤特异性糖肽，这些糖肽在黏蛋白的正常糖型中不存在。MUC1 糖肽可由 APC 在 MHC II 类分子上呈递，以激活糖肽特异性辅助性 T 细胞。目前尚无研究报道 MUC1 糖肽作为细胞毒性 T 细胞的刺激物在 MHC I 类分子上的呈递。在这项研究中，我们表明人类免疫蛋白酶体和组织蛋白酶-L 可以在体外从 MUC1 重复结构域生成 8 至 11 聚体糖肽。我们鉴定了糖基化片段，其中包含单个糖的 10 聚体糖肽 SAP10 [SAPDT(GalNAc)RPAPG]与 MHC I 等位基因 HLA A*0201 的结合强度相当，与串联重复的预测高评分结合表位相当。用二糖 Gal-GalNAc 糖基化的相同序列不结合。SAP10 上的聚糖通过分子建模预测要么向外突出，要么指向 MHC 槽。SAPDTRPAPG 肽及其相应的糖肽在体外刺激细胞毒性 T 细胞。我们的研究结果表明，MUC1 串联重复糖肽能够激活辅助性 T 细胞和细胞毒性 T 细胞，因此是作为疫苗进一步开发的良好候选物。
