Differential Expression of N- and O-glycans on HeLa Cells-Revealed by Direct Fluorescent Glycan Labeling with Recombinant Sialyltransferases

Cells are covered with glycans. The expression and distribution of specific glycans on cell surface are important for various cellular functions. Imaging these glycans is essential to elucidate their biological roles. Here, utilizing enzymatic incorporation of fluorophore-conjugated sialic acids, dubbed as d irect f luorescent g lycan l abeling (DFGL), we report the imaging of N- and O-glycans and particularly tumor specific sialyl T antigen on HeLa cells. It is found that while Core-1 O-glycans are relatively evenly distributed on cells, the expression of N-glycans tend to be more peripheral. More interestingly, the expression of sialyl T antigen displays random and sporadic patterns. In technique side, DFGL allows convenient labeling or imaging of various glycans on intact glycoproteins or cell surfaces with variety of fluorescent dyes.