title: Neurosteroid analogues. 17. Inverted binding orientations of androsterone enantiomers at the steroid potentiation site on γ-aminobutyric acid type A receptors.
abstract: The enantiomer pair androsterone and ent-androsterone are positive allosteric modulators of γ-aminobutyric acid (GABA) type A receptors. Each enantiomer was shown to bind at the same receptor site. Binding orientations of the enantiomers at this site were deduced using enantiomer pairs containing OBn substituents at either C-7 or C-11. 11β-OBn-substituted steroids and 7α-OBn-substituted ent-steroids potently displace [(35)S]-tert-butylbicyclophosphorothionate, augment GABA currents, and anesthetize tadpoles. In contrast, 7β-OBn-substituted steroids and 11α-OBn-substituted ent-steroids have diminished actions. The results suggest that the binding orientations of the active analogues are inverted relative to each other with the 7α- and 11β-substituents similarly located on the edges of the molecules not in contact with the receptor surface. Analogue potentiation of the GABA current was abrogated by an α(1) subunit Q241L mutation, indicating that the active analogues act at the same sites in α(1)β(2)γ(2L) receptors previously associated with positive neurosteroid modulation.
authors.affiliation: Department of Developmental Biology, Washington University, St. Louis School of Medicine, St. Louis, Missouri 63110, United States.
authors.forename: Kathiresan
authors.initials: K
authors.lastname: Krishnan
authors.forename: Brad D
authors.initials: BD
authors.lastname: Manion
authors.forename: Amanda
authors.initials: A
authors.lastname: Taylor
authors.forename: John
authors.initials: J
authors.lastname: Bracamontes
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Steinbach
authors.forename: David E
authors.initials: DE
authors.lastname: Reichert
authors.forename: Alex S
authors.initials: AS
authors.lastname: Evers
authors.forename: Charles F
authors.initials: CF
authors.lastname: Zorumski
authors.forename: Steven
authors.initials: S
authors.lastname: Mennerick
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Covey
mesh_terms: D000495:Allosteric Site; D000738:Androsterone / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D007814:Larva / Q000187:drug effects / Q000502:physiology; D008958:Models, Molecular; D018377:Neurotransmitter Agents / Q000737:chemistry* / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D011869:Radioligand Assay; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism*; D012018:Reflex / Q000187:drug effects; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014982:Xenopus laevis / Q000502:physiology
chemical_list: D018377:Neurotransmitter Agents; D011963:Receptors, GABA-A; D000738:Androsterone