Abstract

GABA acts on GABA_A receptors to evoke both phasic inhibitory synaptic events and persistent, tonic currents. The γ2 subunit of the GABA_A receptor is involved in both phasic and tonic signaling in the hippocampus. Several mutations of this subunit are linked to human epileptic syndromes with febrile seizures, yet it is not clear how they perturb neuronal activity. Here, we examined the expression and functional impact of recombinant γ2 in hippocampal neurons. We show that the K289M mutation has no effect on membrane trafficking and synaptic aggregation of recombinant γ2, but accelerates the decay of synaptic currents. In contrast, the R43Q mutation primarily reduces surface expression of recombinant γ2. However, it has no dominant effect on synaptic currents but instead reduces tonic GABA currents, at least in part by reducing surface expression of the α5 subunit. Our data suggests that the phenotypic specificity of mutations affecting the GABA_A receptor γ2 gene may result from different actions specific to distinct modes of GABAergic signaling.