Bidirectional Control of Synaptic GABA(A)R Clustering by Glutamate and Calcium

GABAergic synaptic transmission regulates brain function by establishing the appropriate excitation-inhibition (E/I) balance in neural circuits. The structure and function of GABAergic synapses are sensitive to destabilization by impinging neurotransmitters. However, signaling mechanisms that promote the restorative homeostatic stabilization of GABAergic synapses remain unknown. Here, by quantum dot single-particle tracking, we characterize a signaling pathway that promotes the stability of GABA(A) receptor (GABA(A)R) postsynaptic organization. Slow metabotropic glutamate receptor signaling activates IP(3) receptor-dependent calcium release and protein kinase C to promote GABA(A)R clustering and GABAergic transmission. This GABA(A)R stabilization pathway counteracts the rapid cluster dispersion caused by glutamate-driven NMDA receptor-dependent calcium influx and calcineurin dephosphorylation, including in conditions of pathological glutamate toxicity. These findings show that glutamate activates distinct receptors and spatiotemporal patterns of calcium signaling for opposing control of GABAergic synapses.