Protein-Specific Imaging of O-GlcNAcylation in Single Cells.

Thousands of intracellular proteins are post-translationally modified with O-GlcNAc, and O-GlcNAcylation impacts the function of modified proteins and mediates diverse biological processes. However, the ubiquity of this important glycosylation makes it highly challenging to probe the O-GlcNAcylation state of a specific protein at the cellular level. Herein, we report the development of a FLIM-FRET-based strategy, which exploits the spatial proximity of the O-GlcNAc moiety and the attaching protein, for protein-specific imaging of O-GlcNAcylation in single cells. We demonstrated this strategy by imaging the O-GlcNAcylation state of tau and β-catenin inside the cells. Furthermore, the changes in tau O-GlcNAcylation were monitored when the overall cellular O-GlcNAc was pharmacologically altered by using the OGT and OGA inhibitors. We envision that the FLIM-FRET strategy will be broadly applicable to probe the O-GlcNAcylation state of various proteins in the cells.