title: Mutational Analysis of the Putative High-Affinity Propofol Binding Site in Human β3 Homomeric GABAA Receptors.
abstract: Propofol is a sedative and anesthetic agent that can both activate GABA(A) receptors and potentiate receptor activation elicited by submaximal concentrations of the transmitter. A recent modeling study of the β3 homomeric GABA(A) receptor postulated a high-affinity propofol binding site in a hydrophobic pocket in the middle of a triangular cleft lined by the M1 and M2 membrane-spanning domains of one subunit and the M2 domain of the neighboring subunit. The goal of the present study was to gain functional evidence for the involvement of this pocket in the actions of propofol. Human β3 and α1β3 receptors were expressed in Xenopus oocytes, and the effects of substitutions of selected residues were probed on channel activation by propofol and pentobarbital. The data demonstrate the vital role of the β3(Y143), β3(F221), β3(Q224), and β3(T266) residues in the actions of propofol but not pentobarbital in β3 receptors. The effects of β3(Y143W) and β3(Q224W) on activation by propofol are likely steric because propofol analogs with less bulky ortho substituents activated both wild-type and mutant receptors. The T266W mutation removed activation by propofol in β3 homomeric receptors; however, this mutation alone or in combination with a homologous mutation (I271W) in the α1 subunit had almost no effect on activation properties in α1β3 heteromeric receptors. We hypothesize that heteromeric α1β3 receptors can be activated by propofol interactions with β3-β3, α1-β3, and β3-α1 interfaces, but the exact locations of the binding site and/or nature of interactions vary in different classes of interfaces.
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.).
authors.forename: Megan M
authors.initials: MM
authors.lastname: Eaton
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.).
authors.forename: Lily Q
authors.initials: LQ
authors.lastname: Cao
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.).
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.).
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Franks
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.).
authors.forename: Alex S
authors.initials: AS
authors.lastname: Evers
authors.affiliation: Department of Anesthesiology (M.M.E., L.Q.C., Z.C., A.S.E., G.A.) and the Taylor Family Institute for Innovative Psychiatric Research (Z.C., A.S.E., G.A.), Washington University School of Medicine, St. Louis, Missouri; and Department of Life Sciences, Imperial College London, South Kensington, United Kingdom (N.P.F.) akk@morpheus.wustl.edu.
authors.forename: Gustav
authors.initials: G
authors.lastname: Akk
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D004252:DNA Mutational Analysis / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D009154:Mutation / Q000235:genetics*; D015742:Propofol / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011963:Receptors, GABA-A / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C546273:GABRB3 protein, human; D011963:Receptors, GABA-A; D015742:Propofol