RESUMO
During development, neural circuit formation requires the stabilization of active γ-aminobutyric acidmediated (GABAergic) synapses and the elimination of inactive ones. Here, we demonstrate that, although the activation of postsynaptic GABA type A receptors (GABAARs) and adenosine A2A receptors (A2ARs) stabilizes GABAergic synapses, only A2AR activation is sufficient. Both GABAAR- and A2AR-dependent signaling pathways act synergistically to produce adenosine 3',5'-monophosphate through the recruitment of the calciumcalmodulinadenylyl cyclase pathway. Protein kinase A, thus activated, phosphorylates gephyrin on serine residue 303, which is required for GABAAR stabilization. Finally, the stabilization of pre- and postsynaptic GABAergic elements involves the interaction between gephyrin and the synaptogenic membrane protein Slitrk3. We propose that A2ARs act as detectors of active GABAergic synapses releasing GABA, adenosine triphosphate, and adenosine to regulate their fate toward stabilization or elimination.
Assuntos
Adenosina/metabolismo , Hipocampo/crescimento & desenvolvimento , Neurônios/fisiologia , Receptor A2A de Adenosina/metabolismo , Transdução de Sinais , Sinapses/fisiologia , Ácido gama-Aminobutírico/metabolismo , Antagonistas do Receptor A2 de Adenosina , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , Cognição , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Hipocampo/metabolismo , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Proteínas do Tecido Nervoso , Fosforilação , Receptor A2A de Adenosina/genética , Receptores de GABA-A/metabolismoRESUMO
The K+-Cl- co-transporter KCC2 (SLC12A5) tunes the efficacy of GABAA receptor-mediated transmission by regulating the intraneuronal chloride concentration [Cl-]i. KCC2 undergoes activity-dependent regulation in both physiological and pathological conditions. The regulation of KCC2 by synaptic excitation is well documented; however, whether the transporter is regulated by synaptic inhibition is unknown. Here we report a mechanism of KCC2 regulation by GABAA receptor (GABAAR)-mediated transmission in mature hippocampal neurons. Enhancing GABAAR-mediated inhibition confines KCC2 to the plasma membrane, while antagonizing inhibition reduces KCC2 surface expression by increasing the lateral diffusion and endocytosis of the transporter. This mechanism utilizes Cl- as an intracellular secondary messenger and is dependent on phosphorylation of KCC2 at threonines 906 and 1007 by the Cl--sensing kinase WNK1. We propose this mechanism contributes to the homeostasis of synaptic inhibition by rapidly adjusting neuronal [Cl-]i to GABAAR activity.