O-linked β-N-acetylglucosamine modification (O-GlcNAc)

O-GlcNAcylation is a dynamic and reversible post-translational modification characterized by the attachment of a single N-acetylglucosamine (GlcNAc) moiety to serine or threonine residues of nuclear and cytoplasmic proteins. Unlike classical glycosylation, it occurs exclusively in the nucleocytoplasmic compartment and does not involve the formation of complex glycan chains. The process is tightly regulated by a single pair of enzymes: O-GlcNAc transferase (OGT), which adds the sugar, and O-GlcNAcase (OGA), which removes it. O-GlcNAcylation serves as a critical nutrient and stress sensor, with its levels directly influenced by the flux of the hexosamine biosynthetic pathway and the availability of UDP-GlcNAc. It plays a fundamental role in regulating diverse cellular processes, including signal transduction, transcription, and proteostasis, often through reciprocal crosstalk with protein phosphorylation. Dysregulation of O-GlcNAc levels is strongly associated with chronic diseases such as type 2 diabetes, cancer, and neurodegenerative disorders like Alzheimer's disease. In Alzheimer's, increased O-GlcNAcylation of the Tau protein is thought to be neuroprotective by inhibiting its hyperphosphorylation and subsequent aggregation. Therapeutic development primarily targets the regulatory enzymes, with OGA inhibitors currently being investigated in clinical trials for their potential to treat tauopathies. Challenges in targeting this system include the widespread nature of the modification and the potential for systemic toxicity, particularly with OGT inhibition.

Other names

O-GlcNAcylationO-GlcNAc modificationNucleocytoplasmic glycosylationO-linked N-acetylglucosaminylation

Inhibition of O-GlcNAcase (OGA) to increase O-GlcNAc levels or inhibition of O-GlcNAc transferase (OGT) to decrease O-GlcNAc levels.