Probing the inhibitory neurosteroid binding site on the GABAA receptor (360G-Wellcome-099693_Z_12_Z)

Neurosteroids are naturally occurring potent modulators of type A GABA receptors in the brain. Although there are many neurosteroid metabolites, these can be characterised into two distinct classes - those that potentiate GABAA receptor function and those that inhibit. Previously we deduced where potentiating neurosteroids bind on the GABAA receptor, but the inhibitory neurosteroids remain unaffected if this site is disrupted. This concurs with the belief that such inhibitory neurosteroids bind to another discrete site onthe GABAA receptor. Its discovery will allow the function of the inhibitory neurosteroids to be explored in the brain. We will select a GABA receptor thatlacks sensitivity to inhibitory neurosteroids and use this structure in combination with GABAA receptor subunits to make chimeric and eventually pointmutated receptors to identify the inhibitory neurosteroid binding site. Once the site is found, we will disrupt its function and then observe the consequences for inhibitory synaptic and tonic inhibition. Overall, this studywill use structural, electrophysiological, imaging, pharmacological and molecular approaches with GABA receptors. This study will bring much need clarity to the role and importance of inhibitory neurosteroids in the brain.