Lymphocyte activation induces rapid changes in nuclear and cytoplasmic glycoproteins.

A unique form of nucleoplasmic and cytoplasmic protein glycosylation, O-linked GlcNAc, (O-GlcNAc) is present on proteins ranging from those of yeast to man, including many chromatin proteins, transcription factors, nuclear pore proteins, and certain types of cytoskeletal proteins. In this report we have studied the effects of cellular activation on O-GlcNAc-modified proteins, using T lymphocytes as a model system. Results indicate that the apparent levels of O-GlcNAc on many nuclear proteins increases rapidly after lymphocyte activation, returning to control levels after a few hours. In contrast, the apparent levels of O-GlcNAc on a distinct population of cytosolic proteins decreases rapidly after cellular activation and also returns to control levels after a few hours. These data are consistent with the hypothesis that O-GlcNAc is a regulatory modification and suggest that O-GlcNAc modification may play an important role in the early stages of T-lymphocyte activation.