Chemoenzymatic Synthesis of Glycopeptides to Explore the Role of Mucin 1 Glycosylation in Cell Adhesion

Posttranslational modifications affect protein biology in physiological and pathological conditions. Efficient methods for the preparation of peptides and proteins carrying defined, homogeneous modifications are fundamental tools for investigating these functions. In the case of Mucin 1 (MUC1) an altered glycosylation pattern is observed in carcinogenesis. To better understand the role of MUC1 glycosylation in interaction and adhesion of cancer cells, we prepared a panel of homogeneously O-glycosylated MUC1 peptides using a quantitative chemoenzymatic approach. Cell adhesion experiments with MCF-7 cancer cells on surfaces carrying up to 6 differently glycosylated MUC1 peptides demonstrated that different glycans significantly impact adhesion. This finding suggests a distinct role of MUC1 glycosylation patterns in cancer cell migration and/or invasion. To decipher the molecular mechanism for the observed adhesion we investigated conformation of the glycosylated MUC1 peptides by NMR. These experiments revealed only minor differences in peptide structure, therefore clearly relating the adhesion behaviour to the type and number of glycans linked to MUC1.