Production of peptides and enzymatic assembly of glycopeptides:

MUC1, the prototypic human mucin, is a ubiquitous membrane-associated glycoprotein that is abundant on the apical cell-surfaces of epithelial tissue. Tumor cells over express and aberrantly glycosylate MUC1 creating unique addresses on such cells. MUC2 is a secreted form of mucin, which is exclusively expressed in the goblet cells lining the gastrointestinal mucosa. MUC2 is characterized by tandem and irregular repeat sequences rich in threonine and serine, which are sites of attachment of the oligosaccharide chains.  Our laboratory is focusing on the biosynthesis of such tumor markers with a view to using them as validated targets in our drug discovery program or as potential antigens in the preparation of cancer vaccines¹.   DNA aptamers have now been created in our laboratory to recognize mucin MUC1 glycoforms (Figure 1).

Figure 1 : Composite of phase contrast and confocal images of T47D human breast cancer cells overexpressing underglycosylated forms of the tumor-associated mucin MUC1.  A rhodamine-labeled aptamer (red) recognizing the Tn antigen (GalNAc MUC1) is internalized by cells and co-migrates with mucin MUC1 into endosomes (green) as well as other cellular compartments. Aptamer localization into endosomes gives rise to yellow-colored areas.