Differential and Age Dependent Expression of Specific Sialoglycans on HeLa Cells -Revealed by Direct Fluorescent Glycan Labeling

Abstract Cells are covered with sialoglycans. The expression and distribution of specific sialoglycans on cell surface are important for various cellular functions. Imaging these glycans is essential to elucidate their biological roles. Here, utilizing enzymatic incorporation of orthogonal sialic acids, especially fluorophore-conjugated sialic acids, dubbed as direct fluorescent glycan labeling (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, N-glycans expression tend to be more peripheral. More interestingly, the expression of sialyl T antigen displays random and sporadic patterns that likely are age and stress dependent, suggesting that sialyl T antigen expression is not an immediate outcome of direct genetic mutation but rather arises from disordered post-translational machinery. In technique side, DFGL not only allows covalently labeling of sialoglycans on intact glycoproteins with variety of fluorescent dyes, but also allows imaging different sialoglycans simultaneously without cross staining. With the unprecedented convenience and specificity, we believe that technique like DFGL will transform the research on glycoscience.