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Postsynaptic clustering of major GABAA receptor subtypes requires the γ2 subunit and gephyrin

Abstract

Most fast inhibitory neurotransmission in the brain is mediated by GABAA receptors, which are mainly postsynaptic and consist of diverse α and ß subunits together with the γ2 subunit. Although the γ2 subunit is not necessary for receptor assembly and translocation to the cell surface, we show here that it is required for clustering of major postsynaptic GABAA receptor subtypes. Loss of GABAA receptor clusters in mice deficient in the γ2 subunit, and in cultured cortical neurons from these mice, is paralleled by loss of the synaptic clustering molecule gephyrin and synaptic GABAergic function. Conversely, inhibiting gephyrin expression causes loss of GABAA receptor clusters. The γ2 subunit and gephyrin are thus interdependent components of the same synaptic complex that is critical for postsynaptic clustering of abundant subtypes of GABAA receptors in vivo.

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Figure 1: Loss of clustered GABAA receptors containing the γ2 or the α2 subunit in γ2–/– cortical neurons.
Figure 2: Loss of clustered GABAA receptors containing the α1 subunit in cultured γ2–/– cortical neurons (20 DIV).
Figure 3: Quantification of GABAA receptor and gephyrin clusters and functional deficit in γ2–/– neurons.
Figure 4: Unaltered α1 and α2 mRNA and protein levels in cortical neurons cultured from γ2+/+, γ2–/+ and γ2–/– embryos (20 DIV).
Figure 5: Colocalization of gephyrin and GABAA receptor subunit immunoreactivity and loss of gephyrin staining in γ2–/– neurons.
Figure 6: Loss of punctate GABAA receptor subunit immunoreactivity upon antisense inhibition of gephyrin expression.
Figure 7: Loss of clustered α2-subunit-containing GABAA receptors and gephyrin in the cerebral cortex of the γ2–/– brain (P14).
Figure 8: Loss of clustered α1-subunit-containing GABAA receptors and gephyrin in the cerebellum of the γ2–/– brain (P14).

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Acknowledgements

We are grateful to J. Kirsch for providing mAb 7A, to P. J. Mitchell for the MTF-1 plasmid template and to U. Rudolph for the plasmid containing the α1 subunit gene fragment. The GAD-selective antibody GAD-6 developed by D. I. Gottlieb was obtained from Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the University of Iowa, Iowa City, Iowa. We are grateful to S. Balsiger and G. Reyes for technical assistance, D. Benke for advice, T. Bächi and M. Höchli for help with confocal laser microscopy and to H. Mohler for his support and comments on the manuscript. This work was supported by grants from the Swiss National Science Foundation (#31-39702.93, 31-52631.97) to B. L.

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Correspondence to Bernhard Lüscher.

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Essrich, C., Lorez, M., Benson, J. et al. Postsynaptic clustering of major GABAA receptor subtypes requires the γ2 subunit and gephyrin. Nat Neurosci 1, 563–571 (1998). https://doi.org/10.1038/2798

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