Chen_2023_Cells_13_

GABA(A) receptors are the major inhibitory receptors in the brain. They are hetero-pentamers with a composition of predominantly two alpha, two beta, and one gamma or delta subunit. Of the six alpha subunit genes, the alpha5 subunit displays a limited spatial expression pattern and is known to mediate both phasic and tonic inhibition. In this study, using immunoaffinity-based proteomics, we identified the alpha5 subunit containing receptor complexes in the hippocampus and olfactory bulb. The alpha1-alpha5 interaction was identified in both brain regions, albeit with significantly different stoichiometries. In line with this, reverse IPs using anti-alpha1 antibodies showed the alpha5-alpha1 co-occurrence and validated the quantitative difference. In addition, we showed that the association of Neuroligin 2 with alpha1-containing receptors was much higher in the olfactory bulb than in the hippocampus, which was confirmed using blue native gel electrophoresis and quantitative mass spectrometry. Finally, immunocytochemical staining revealed a co-localization of alpha1 and alpha5 subunits in the post-synaptic puncta in the hippocampus.