Local miRNA-Dependent Translational Control of GABAR Synthesis during Inhibitory Long-Term Potentiation.

Molecular mechanisms underlying plasticity at brain inhibitory synapses remain poorly characterized. Increased postsynaptic clustering of GABA receptors (GABARs) rapidly strengthens inhibition during inhibitory long-term potentiation (iLTP). However, it is unclear how synaptic GABAR clustering is maintained to sustain iLTP. Here, we identify a role for miR376c in regulating the translation of mRNAs encoding the synaptic α1 and γ2 GABAR subunits, GABRA1 and GABRG2, respectively. Following iLTP induction, transcriptional repression of miR376c is induced through a calcineurin-NFAT-HDAC signaling pathway and promotes increased translation and clustering of synaptic GABARs. This pathway is essential for the long-term expression of iLTP and is blocked by miR376c overexpression, specifically impairing inhibitory synaptic strength. Finally, we show that local de novo synthesis of synaptic GABARs occurs exclusively in dendrites and in a miR376c-dependent manner following iLTP. Together, this work describes a local post-transcriptional mechanism that regulates inhibitory synaptic plasticity via miRNA control of dendritic protein synthesis.