Chemoenzymatic synthesis of derivatives of a T-cell-stimulating peptide which carry tumor-associated carbohydrate antigens
作者:Shaji K. George、Björn Holm、Celso A. Reis、Tilo Schwientek、Henrik Clausen、Jan Kihlberg
DOI:10.1039/b009567m
日期:——
The Tn (GalNAcα-Ser/Thr), T [Galβ(1→3)GalNAcα-Ser/Thr], sialyl-Tn [Neu5Acα(2→6)GalNAcα-Ser/Thr] and 2,3-sialyl-T [Neu5Acα(2→3)Galβ(1→3)GalNAcα-Ser/Thr] antigens are examples of tumor-associated carbohydrate antigens expressed by epithelial cancers. We now describe the preparation of 2-bromoethyl glycosides corresponding to the Tn and T antigens in one and five chemical steps (51 and 15% total yield), respectively, starting from N-acetylgalactosamine. The 2-bromoethyl Tn and T glycosides were used to alkylate a homocysteine residue incorporated in a peptide that is able to bind to class I MHC molecules on antigen-presenting cells. The two neoglycopeptides were then converted into glycopeptides which carry the sialyl-Tn and 2,3-sialyl-T antigens by using recombinant sialyltransferases. Interestingly, the sialyltransferases were able to sialylate the Tn and T carbohydrate moieties even though they were linked to the peptide backbone via a spacer instead of being attached to serine or threonine. The four glycopeptides will be used in studies directed towards inducing a carbohydrate-specific T cell response against the Tn, T, sialyl-Tn, and 2,3-sialyl-T antigens.
Tn (GalNAcα-Ser/Thr)、T [Galβ(1→3)GalNAcα-Ser/Thr]、唾液酸-Tn [Neu5Acα(2→6)GalNAcα-Ser/Thr] 和 2,3-唾液酸-T [ Neu5Acα(2→3)Galβ(1→3)GalNAcα-Ser/Thr]抗原是上皮癌表达的肿瘤相关糖抗原的例子。我们现在描述从 N-乙酰半乳糖胺开始,分别通过 1 个和 5 个化学步骤(总产率 51% 和 15%)制备对应于 Tn 和 T 抗原的 2-溴乙基糖苷。 2-溴乙基 Tn 和 T 糖苷用于烷基化肽中掺入的同型半胱氨酸残基,该肽能够与抗原呈递细胞上的 I 类 MHC 分子结合。然后通过使用重组唾液酸转移酶将这两种新糖肽转化为携带唾液酸-Tn和2,3-唾液酸-T抗原的糖肽。有趣的是,唾液酸转移酶能够唾液酸化 Tn 和 T 碳水化合物部分,即使它们通过间隔基连接到肽主链而不是连接到丝氨酸或苏氨酸。这四种糖肽将用于针对 Tn、T、唾液酸-Tn 和 2,3-唾液酸-T 抗原诱导碳水化合物特异性 T 细胞反应的研究。