PROFILING LIGANDS FOR SELECTIVE ACTION ON Α6 – CONTAINING GABA-A RECEPTORS

The GABA-A receptors, key mediators of inhibitory neurotransmission in the central nervous system, consist of diverse pentameric assemblies derived from 19 possible subunits. This structural variability results in over a million theoretical receptor combinations, with the α6-containing subtypes being particularly interesting due to restricted expression in the cerebellum—a brain region implicated in motor coordination. Consequently, the α6 subunit is investigated as a promising target for conditions such as essential tremor and tic-disorders. Therefore, the substances that selectively modulate α6-containing GABA-A receptors are of great interest for therapeutic development, and their activity is being studied in preclinical models for aforementioned conditions. Novel ligands, (referred to as JOHE compounds) identified through pharmacophore modeling and virtual screening, showed selectivity for α6- over α1-containing GABA-A receptors. To characterize the binding site suspected for providing selectivity, mutational studies were conducted, introducing targeted amino acid substitutions into the binding site of α6 subunit. Using two-electrode voltage clamp (TEVC) recordings, modulation by JOHEs was measured. The mutations in the candidate binding site had a strong impact on the efficacy of the modulation, providing evidence that the selectivity of JOHEs towards the α6-containing GABA-A receptor is mediated by mutated amino acids. This finding offers a valuable insight for developing novel selective drugs targeting cerebellar GABA-A receptor subtypes.