Human Hyperekplexic Mutations in Glycine Receptors Disinhibit the Brainstem by Hijacking GABAA Receptors.

Hyperekplexia disease is usually caused by naturally occurring point mutations in glycine receptors (GlyRs). However, the γ-aminobutyric acid type A receptor (GABAAR) seems to be also involved regarding the therapeutic basis for hyperekplexia using benzodiazepines, which target GABAARs but not GlyRs. Here, we show that the function of GABAARs was significantly impaired in the hypoglossal nucleus of hyperekplexic transgenic mice. Such impairment appeared to be mediated by interaction between GABAAR and mutant GlyR. The GABAAR dysfunction was caused only by mutant GlyR consisting of homomeric α1 subunits, which locate primarily at pre- and extra-synaptic sites. In addition, the rescue effects of diazepam were attenuated by Xli-093, which specifically blocked diazepam-induced potentiation on α5-containing GABAAR, a major form of pre- and extra-synaptic GABAAR in the brainstem. Thus, our results suggest that the pre- and extra-synaptic GABAARs could be a potential therapeutic target for hyperekplexia disease caused by GlyR mutations.