Recent Chemical Biology Approaches for Profiling Cell Surface Sialylation Status

Sialic acids (SAs) often exist as the terminal sugars of glycans of either glycoproteins or glycolipids on the cell surface and thus are directly involved in biological processes, such as cell-cell, cell-ligand, and cell-pathogen interactions. Cell surface SA expression levels and their linkages are collectively termed cell surface sialylation status, which represent varying cellular states and contribute to the overall functionality of a cell. Accordingly, systemic and specific profiling of the cell surface sialyation status is critical in deciphering the structures and functions of cell surface glycoconjugates and the molecular mechanisms of their underlying biological processes. In recent decades, several advanced chemical biology approaches have been developed to profile the cell surface sialyation status of both in vitro and in vivo samples, including metabolic labeling, direct chemical modification, and boronic acid coupling approaches. Various investigative technologies have also been explored for their unique competence, including fluorescent imaging, flow cytometry, Raman imaging, magnetic resonance imaging (MRI), and matrix-assisted laser desorption ionization imaging mass spectrometry. In particular, the sialylation status of a specific glycoprotein on the cell surface has been investigated. This review highlights the recent advancements in chemical biology approaches for profiling cell surface sialyation status. It is expected that this review will provide researchers different choices for both biological and biomedical research and applications.