Immune Regulation by the Posttranslational Modification O-GlcNAc

The posttranslational modification of proteins by a single O-linked N-acetylglucosamine (O-GlcNAc) is an intracellular biochemical reaction which is ubiquitous in eukaryotic cells. Two enzymes regulate the process: O-linked Nacetylglucosaminyltransferase (OGT), which attaches O-GlcNAc to serine/threonine residues of proteins, and a a-Nacetylglucosaminidase (O-GlcNAcase), that removes the O-GlcNAc group. The serine or threonine targeted by OGlcNAc can occur at sites modified by other enzymes such as protein kinases. There have been many indications that OGlcNAc modifications are actively involved in the regulation of the immune system and recent results have begun to shed light on possible mechanisms. This review summarizes recent advances in the field of O-GlcNAc modification, with a special attention to its role in the activation of lymphocytes.