Cell-type specific labelling of O-linked glycoproteins in engineered K-562 cells

We report a strategy termed Bio-Orthogonal Cell line-specific Tagging of Glycoproteins (BOCTAG). Cells are equipped by transfection with an artificial biosynthetic pathway (mut-AGX1/NahK) that transforms an alkyne tagged sugar into the corresponding nucleotide-sugar. Only transfected cells incorporate the bioorthogonal sugar into glycoproteins in the presence of non-transfected cells. The incorporation of alkyne-sugar in glycoproteins allows the installation, by copper(I)-catalyzed reaction, of a biotinylated tag. Glycoproteins are enriched using Streptavidin, and on-bead digestion yielded a peptide fraction that is analysed by mass spectrometry.