Pharmacological study on recombinant human GABA-A receptor complex containing alpha5 (leucine155 to valine) combined with beta3gamma2s subunits.

AIM: To investigate the characterization of the pharmacology of recombinant human GABA-A receptor complex containing alpha5beta3gamma2s subunits, and clarify which amino acids are essential for binding affinity. METHODS: We constructed chimeric subunit of alpha5 (leucine mutated to valine in 155) by site-directed mutation, combined alpha5 or alpha5 (valine 155) with beta3gamma2s subunits by using the baculovirus-transfected Sf-9 insect cell expressing system. Fifteen commercially available effective compounds for the GABA binding recognition site were determined. RESULTS: We found that competitive antagonist SR95531 and inhibitor Thio-4-piol increased IC50 values about 3 folds in alpha5 (valine155) beta3gamma2s compare to alpha5 (leucine155) beta3gamma2s receptor subunit combinations; Other GABA-A receptor ligands have little difference. CONCLUSION: The amino acid residues in 155 is important for the binding affinity and efficacy of SR95531 and Thio-4-piol to GABA-A receptor combinations containing an alpha5 subunit.