Identification of the putative binding pocket of valerenic acid on GABAA receptors using docking studies and site-directed mutagenesis.

ABSTRACT: BACKGROUND AND PURPOSE:?2/3-subunit-selective modulation of GABAA receptors by valerenic acid (VA) is determined by the presence of transmembrane residue ?2/3N265. Currently, it is not known whether ?2/3N265 is part of VA's binding pocket or is involved in the transduction pathway of VA's action. The aim of this study was to clarify the localization of VA's binding pocket on GABAA receptors. EXPERIMENTAL APPROACH:Docking and a structure-based three-dimensional pharmacophore were employed to identify candidate amino acid residues that are likely to interact with VA. Selected amino acid residues were mutated, and VA-induced modulation of the resulting GABAA receptors expressed in Xenopus oocytes was analysed. KEY RESULTS:A binding pocket for VA at the ?(+) /?(-) interface encompassing amino acid ?3N265 was predicted. Mutational analysis of suggested amino acid residues revealed a complete loss of VA's activity on ?3M286W channels as well as significantly decreased efficacy and potency of VA on ?3N265S and ?3F289S receptors. In addition, reduced efficacy of VA-induced IGABA enhancement was also observed for ?1M235W, ?3R269A and ?3M286A constructs. CONCLUSIONS AND IMPLICATIONS:Our data suggest that amino acid residues ?3N265, ?3F289, ?3M286, ?3R269 in the ?3 subunit, at or near the etomidate/propofol binding site(s), form part of a VA binding pocket. The identification of the binding pocket for VA is essential for elucidating its pharmacological effects and might also help to develop new selective GABAA receptor ligands.

SUBMITTER: Luger D 

PROVIDER: S-EPMC4988470 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature