Latino Studies at New York University

Ben Ovryn

Associate Professor
Department of Anatomy and Structural Biology
Albert Einstein College of Medicine

April 1, 2014

Tracking surface glycans on live cancer cells with single molecule sensitivity

A considerable body of literature describes the diffusive and anomalous dynamics of proteins and lipids in the plasma membrane of living cells, but less is known about the dynamics of cell-surface glycans.  We exploit a combination of bioorthogonal click chemistry and single molecule tracking to investigate the dynamics of N-linked sialic acid and O-linked GalNAc in live cells metabolically labeled with azide- or alkyne-containing monosaccharide precursors. By optimizing the conditions of fluorescent tagging, mediated by Cu(I)-catalyzed azide-alkyne cycloaddition, and controlled bleaching, a sufficiently low spatial density of fluorescently-labeled glycan molecules is achieved, enabling dynamic single-molecule tracking. Unprecedented spatial and temporal resolution of the movement of surface glycans has allowed us to characterize the variation of the mean square displacement and cumulative distribution function for N-linked sialic acid and O-linked glycans with a cell's metastatic potential. We interpret the observed anomalous diffusion as arising from damped Brownian motion under a confining harmonic potential rather than caused by transient immobilization due to spatial inhomogeneities on the plasma membrane.