title: A human mutation in Gabrg2 associated with generalized epilepsy alters the membrane dynamics of GABAA receptors.
abstract: Neuronal activity modulates the membrane diffusion of postsynaptic γ-aminobutyric acid (GABA)(A) receptors (GABA(A)Rs), thereby regulating the efficacy of GABAergic synapses. The K289M mutation in GABA(A)Rs subunit γ2 has been associated with the generalized epilepsy with febrile seizures plus (GEFS+) syndrome. This mutation accelerates receptor deactivation and therefore reduces inhibitory synaptic transmission. Yet, it is not clear why this mutation specifically promotes febrile seizures. We show that upon raising temperature both the number of GABA(A)Rs clusters and the frequency of miniature inhibitory postsynaptic currents decreased in neurons expressing the K289M mutant but not wild-type (WT) recombinant γ2. Single-particle tracking experiments revealed that raising temperature increases the membrane diffusion of synaptic GABA(A)Rs containing the K289M mutant but not WT recombinant γ2. This effect was mediated by enhanced neuronal activity as it was blocked by glutamate receptor antagonists and was mimicked by the convulsant 4-aminopyridine. Our data suggest the K289M mutation in γ2 confers GABA(A)Rs with enhanced sensitivity of their membrane diffusion to neuronal activity. Enhanced activity during hyperthermia may then trigger the escape of receptors from synapses and thereby further reduce the efficacy of GABAergic inhibition. Alteration of the membrane diffusion of neurotransmitter receptors therefore represents a new mechanism in human epilepsy.
authors: Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 839, 75005 Paris, France.
authors: Walid
authors: W
authors: Bouthour
authors: Félix
authors: F
authors: Leroy
authors: Charline
authors: C
authors: Emmanuelli
authors: Michèle
authors: M
authors: Carnaud
authors: Maxime
authors: M
authors: Dahan
authors: Jean Christophe
authors: JC
authors: Poncer
authors: Sabine
authors: S
authors: Lévi
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D006624:Hippocampus / Q000503:physiopathology*; D006801:Humans; D009154:Mutation; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission
chemical_list: C546279:GABRG2 protein, human; D011963:Receptors, GABA-A