O-GlcNAc Transferase Regulates GABAergic Synapse Organization and Receptor Composition

Neural circuits must integrate metabolic information to maintain stable activity and appropriate behavioral responses. While metabolic regulation of excitatory synapses has been well studied, far less is known about how inhibitory synapses respond to changes in energy state. In this study, we show that O-GlcNAc transferase (OGT), a dynamic sensor of cellular nutrient flux, localizes to postsynaptic sites of the inhibitory synapses where it modulates synapse morphology and receptor composition. OGT over-expression reduced the size and intensity of vGAT and gephyrin puncta, whereas conditional OGT deletion produced a converse enlargement and redistribution of inhibitory scaffolds and vesicular proteins. Furthermore, OGT deletion accelerated inhibitory postsynaptic current decay kinetics and induced subunit-specific shifts in GABA _A receptor surface expression: β3 subunits decreased, whereas γ2 subunit total and surface levels increased. Together, these findings identify OGT as a metabolic regulator that modulates inhibitory synapse structure and signaling, providing a mechanistic link between energy state and GABAergic circuit function in health and disease.