Association of gephyrin with synaptic and extrasynaptic GABA a receptors varies during development in cultured hippocampal neurons

• Published in: Molecular and cellular neuroscience Vol. 23; no. 2; pp. 264 - 278
• Main Authors: Danglot, Lydia, Triller, Antoine, Bessis, Alain
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.06.2003
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/S1044-7431(03)00069-1

Several studies have reported extrasynaptic clusters of GABA a receptors in hippocampal neurons. Yet their functional relevance as well as their evolution in relation with gephyrin during synaptogenesis remain unknown. We have analyzed the expression pattern of the main proteins of the GABAergic synapses during synaptogenesis in cultured hippocampal neurons. We found that GABAergic terminals, characterized by VIAAT and GAD-65 expression, differentiated 3 to 7 days after the glutamatergic endings. At the postsynaptic side, the GABA aR- β3 subunit was first diffuse and then clustered when GABAergic terminals differentiated and gephyrin formed large clusters. Colocalization of these proteins was high and increased with development. At later stages, GABA aR β3 clusters colocalized with gephyrin at synaptic but also at extrasynaptic sites. GABA aR γ2 subunits were directly expressed as clusters which were first extrasynaptic and not associated with gephyrin. Subsequently, the GABA aR γ2 subunits associated with gephyrin at synaptic and/or extrasynaptic sites. Our data indicate that formation of GABA aR γ2 subunit clusters is gephyrin independent.