In Search of GABA Receptor's Neurosteroid Binding Sites.

Neurosteroids (NS) are the main modulators of γ-aminobutyric acid type A receptors (GABARs), which are the ligand-gated channels target of the major inhibitory neurotransmitter in vertebrates. As a consequence of their ability to modify inhibitory functions in the brain, NS have high physiological and clinical relevance. Accumulated evidence has strongly suggested that NS binding sites were located in the GABAR transmembrane domain; however the specific localization of these sites has remained an enigma for decades. Fortunately, recent resolution of GABARs crystal structures, together with computational strategies applied to investigate the NS binding, has paved the way to rationalizing the molecular basis of NS modulation. This work reviews from a historical perspective the road followed for establishing the GABAR/NS binding mode, from their initial molecular modeling to the latest findings. Furthermore, a comparative analysis describing the NS binding is provided, plus a preliminary analysis of putative NS sites in other assemblies.