title: Neurotoxins from snake venoms and α-conotoxin ImI inhibit functionally active ionotropic γ-aminobutyric acid (GABA) receptors.
abstract: Ionotropic receptors of γ-aminobutyric acid (GABAAR) regulate neuronal inhibition and are targeted by benzodiazepines and general anesthetics. We show that a fluorescent derivative of α-cobratoxin (α-Ctx), belonging to the family of three-finger toxins from snake venoms, specifically stained the α1β3γ2 receptor; and at 10 μm α-Ctx completely blocked GABA-induced currents in this receptor expressed in Xenopus oocytes (IC50 = 236 nm) and less potently inhibited α1β2γ2 ≈ α2β2γ2 > α5β2γ2 > α2β3γ2 and α1β3δ GABAARs. The α1β3γ2 receptor was also inhibited by some other three-finger toxins, long α-neurotoxin Ls III and nonconventional toxin WTX. α-Conotoxin ImI displayed inhibitory activity as well. Electrophysiology experiments showed mixed competitive and noncompetitive α-Ctx action. Fluorescent α-Ctx, however, could be displaced by muscimol indicating that most of the α-Ctx-binding sites overlap with the orthosteric sites at the β/α subunit interface. Modeling and molecular dynamic studies indicated that α-Ctx or α-bungarotoxin seem to interact with GABAAR in a way similar to their interaction with the acetylcholine-binding protein or the ligand-binding domain of nicotinic receptors. This was supported by mutagenesis studies and experiments with α-conotoxin ImI and a chimeric Naja oxiana α-neurotoxin indicating that the major role in α-Ctx binding to GABAAR is played by the tip of its central loop II accommodating under loop C of the receptors.
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Denis S
authors.initials: DS
authors.lastname: Kudryavtsev
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Shelukhina
authors.affiliation: the Moscow Institute of Physics and Technology, Institutsky Per. 9, Dolgoprudny, Moscow Region 141700, Russia.
authors.forename: Lina V
authors.initials: LV
authors.lastname: Son
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Lucy O
authors.initials: LO
authors.lastname: Ojomoko
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Kryukova
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia, the Lomonosov Moscow State University, Moscow 119991, Russia, and.
authors.forename: Ekaterina N
authors.initials: EN
authors.lastname: Lyukmanova
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia, the Syneuro OOO, ul. Miklukho-Maklaya 16/10, Moscow 117997, Russia.
authors.forename: Maxim N
authors.initials: MN
authors.lastname: Zhmak
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia, the Lomonosov Moscow State University, Moscow 119991, Russia, and.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Dolgikh
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Ivanov
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Igor E
authors.initials: IE
authors.lastname: Kasheverov
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Vladislav G
authors.initials: VG
authors.lastname: Starkov
authors.affiliation: the Department of Molecular Neurosciences, Center for Brain Research, Medical University Vienna, A-1090 Vienna, Austria.
authors.forename: Joachim
authors.initials: J
authors.lastname: Ramerstorfer
authors.affiliation: the Department of Molecular Neurosciences, Center for Brain Research, Medical University Vienna, A-1090 Vienna, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Sieghart
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia.
authors.forename: Victor I
authors.initials: VI
authors.lastname: Tsetlin
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Street, Moscow 117997, Russia, utkin@mx.ibch.ru.
authors.forename: Yuri N
authors.identifier: http://orcid.org/0000-0002-4609-970X
authors.initials: YN
authors.lastname: Utkin
mesh_terms: D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D003039:Cobra Neurotoxin Proteins / Q000737:chemistry / Q000494:pharmacology; D020916:Conotoxins / Q000737:chemistry / Q000494:pharmacology; D017815:Elapidae; D051379:Mice; D056004:Molecular Dynamics Simulation; D017433:Protein Structure, Secondary; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D003039:Cobra Neurotoxin Proteins; D020916:Conotoxins; D011963:Receptors, GABA-A; C025154:alpha-cobratoxin
keywords: Cys-loop receptor; GABAA receptor; electrophysiology; fluorescence; molecular dynamics; molecular modeling; neurotoxin; snake venom; three finger toxin