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Cabral IB, de Lima Moreira CV, Rodrigues ACC, da Silva Moreira LK, Pereira JKA, Gomides CD, Lião LM, Machado LS, Vaz BG, da Cunha LC, de Oliveira Neto JR, da Silva-Júnior EF, de Aquino TM, da Silva Santos-Júnior PF, Silva ON, da Rocha FF, Costa EA, Menegatti R, Fajemiroye JO. Preclinical data on morpholine (3,5-di-tertbutyl-4-hydroxyphenyl) methanone induced anxiolysis. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2023; 396:2957-2975. [PMID: 37097335 DOI: 10.1007/s00210-023-02502-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 04/15/2023] [Indexed: 04/26/2023]
Abstract
Trimetozine is used to be indicated for the treatment of mental illnesses, particularly anxiety. The present study provides data on the pharmacological profile of trimetozine derivative morpholine (3,5-di-tert-butyl-4-hydroxyphenyl) methanone (LQFM289) which was designed from molecular hybridization of trimetozine lead compound and 2,6-di-tert-butyl-hydroxytoluene to develop new anxiolytic drugs. Here, we conduct molecular dynamics simulations, docking studies, receptor binding assays, and in silico ADMET profiling of LQFM289 before its behavioral and biochemical assessment in mice within the dose range of 5-20 mg/kg. The docking of LQFM289 showed strong interactions with the benzodiazepine binding sites and matched well with receptor binding data. With the ADMET profile of this trimetozine derivative that predicts a high intestinal absorption and permeability to blood-brain barrier without being inhibited by the permeability glycoprotein, the oral administration of LQFM289 10 mg/kg consistently induced anxiolytic-like behavior of the mice exposed to the open field and light-dark box apparatus without eliciting motor incoordination in the wire, rotarod, and chimney tests. A decrease in the wire and rotarod´s fall latency coupled with an increase in the chimney test´s climbing time and a decrease in the number of crossings in the open field apparatus at the dose of 20 mg/kg of this trimetozine derivative suggest sedative or motor coordination impairment at this highest dose. The attenuation of the anxiolytic-like effects of LQFM289 (10 mg/kg) by flumazenil pretreatment implicates the participation of benzodiazepine binding sites. The lowering of corticosterone and tumor necrosis factor alpha (cytokine) in LQFM289-treated mice at a single oral (acute) dose of 10 mg/kg suggests that the anxiolytic-like effect of this compound also involves the recruitment of non-benzodiazepine binding sites/GABAergic molecular machinery.
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Affiliation(s)
- Iara Barbosa Cabral
- Institute of Biological Science, Federal University of Goiás, CEP 74001-970, Goiânia, GO, Brazil
| | | | | | | | | | - Christian Dias Gomides
- Institute of Chemistry, Federal University of Goiás, Av. Esperança S/N, Campus Samambaia, Goiânia, GO, 74690-900, Brazil
| | - Luciano M Lião
- Institute of Chemistry, Federal University of Goiás, Av. Esperança S/N, Campus Samambaia, Goiânia, GO, 74690-900, Brazil
| | - Lucas S Machado
- Institute of Chemistry, Federal University of Goiás, Av. Esperança S/N, Campus Samambaia, Goiânia, GO, 74690-900, Brazil
| | - Boniek G Vaz
- Institute of Chemistry, Federal University of Goiás, Av. Esperança S/N, Campus Samambaia, Goiânia, GO, 74690-900, Brazil
| | - Luiz Carlos da Cunha
- Faculty of Pharmacy, Federal University of Goiás, PMB 131, CEP 74001-970, Goiânia, Brazil
| | | | - Edeildo Ferreira da Silva-Júnior
- Institute of Chemistry and Biotechnology, Federal University of Alagoas, Lourival Melo Mota Avenue, Alagoas, Maceió, 57072-900, Brazil
| | - Thiago Mendonça de Aquino
- Research Group in Therapeutic Strategies, Federal University of Alagoas, Lourival Melo Mota Avenue, Alagoas, Maceió, 57072-900, Brazil
| | | | - Osmar N Silva
- Evangelical University of Goias, UniEvangélica, Av. Universitária Km 3, 5 Cidade Universitária Anápolis, Goias, GO, 75083-515, Brazil
| | - Fábio Fagundes da Rocha
- Department of Physiological Sciences, Institute of Biology, Federal Rural University of Rio de Janeiro, Seropédica, RJ, Brazil
| | - Elson Alves Costa
- Institute of Biological Science, Federal University of Goiás, CEP 74001-970, Goiânia, GO, Brazil
| | - Ricardo Menegatti
- Faculty of Pharmacy, Federal University of Goiás, PMB 131, CEP 74001-970, Goiânia, Brazil
| | - James O Fajemiroye
- Institute of Biological Science, Federal University of Goiás, CEP 74001-970, Goiânia, GO, Brazil.
- Evangelical University of Goias, UniEvangélica, Av. Universitária Km 3, 5 Cidade Universitária Anápolis, Goias, GO, 75083-515, Brazil.
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Mohamad FH, Mohamad Jamali MA, Che Has AT. Structure-function Studies of GABA (A) Receptors and Related computer-aided Studies. J Mol Neurosci 2023; 73:804-817. [PMID: 37750966 DOI: 10.1007/s12031-023-02158-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 09/12/2023] [Indexed: 09/27/2023]
Abstract
The γ-aminobutyric acid type A receptor (GABA (A) receptor) is a membrane protein activated by the neurotransmitter GABA. Structurally, this major inhibitory neurotransmitter receptor in the human central nervous system is a pentamer that can be built from a selection of 19 subunits consisting of α(1,2,3,4,5 or 6), β (1,2 or 3), γ (1,2 or 3), ρ (1,2 or 3), and δ, π, θ, and ε. This creates several possible pentameric arrangements, which also influence the pharmacological and physiological properties of the receptor. The complexity and heterogeneity of the receptors are further increased by the addition of short and long splice variants in several subunits and the existence of multiple allosteric binding sites and expansive ligands that can bind to the receptors. Therefore, a comprehensive understanding of the structure and function of the receptors is required to gain novel insights into the consequences of receptor dysfunction and subsequent drug development studies. Notably, advancements in computational-aided studies have facilitated the elucidation of residual interactions and exploring energy binding, which may otherwise be challenging to investigate. In this review, we aim to summarize the current understanding of the structure and function of GABA (A) receptors obtained from advancements in computational-aided applications.
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Affiliation(s)
- Fatin H Mohamad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia
| | - Muhamad Arif Mohamad Jamali
- Faculty of Science and Technology, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800, Nilai, Negeri Sembilan, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, Kubang Kerian, 16150 Kota Bharu, Kelantan, Malaysia.
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Silva ON, Franco OL, Neves BJ, Morais ÁCB, De Oliveira Neto JR, da Cunha LC, Naves LM, Pedrino GR, Costa EA, Fajemiroye JO. Involvement of the gabaergic, serotonergic and glucocorticoid mechanism in the anxiolytic-like effect of mastoparan-L. Neuropeptides 2020; 81:102027. [PMID: 32059939 DOI: 10.1016/j.npep.2020.102027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 10/25/2022]
Abstract
Mastoparan-L (mast-L) is a cell-penetrating tetradecapeptide and stimulator of monoamine exocytosis. In the present study, we evaluated the anxiolytic-like effect of mast-L. Preliminary pharmacological tests were conducted to determine the most appropriate route of administration, extrapolate dose and detect potential toxic effects of this peptide. Oral and intracerebroventricular administration of mast-L (0.1, 0.3 or 0.9 mg.kg-1), diazepam (1 or 5 mg.kg-1), buspirone (10 mg.kg-1) or vehicle 10 mL.kg-1 was carried out prior to the exposure of mice to the anxiety models: open field, light-dark box and elevated plus-maze. To characterize the mechanism underlying the antianxiety-like effect of mast-L, pharmacological antagonism, blood plasma analysis, molecular docking, and receptor binding assays were performed. The absence of a neurotoxic sign, animal's death as well as lack of significant changes in the relative organ weight, hematological and biochemical parameters suggest that mast-L is relatively safe. The anxiolytic-like effect of mast-L was attenuated by flumazenil (antagonist of benzodiazepine binding site) and WAY100635 (selective antagonist of 5-HT1A receptors) pretreatments. Mast-L reduced plasma corticosterone and lowered the scoring function at GABAA -18.48 kcal/mol (Ki = 155 nM), 5-HT1A -22.39 kcal/mol (Ki = 130 nM), corticotropin-releasing factor receptor subtype 1 (CRF1) -11.95 kcal/mol (Ki = 299 nM) and glucocorticoid receptors (GR) -14.69 kcal/mol (Ki = 3552 nM). These data fit the binding affinity (Ki) and demonstrate the involvement of gabaergic, serotonergic and glucocorticoid mechanisms in the anxiolytic-like property of mast-L.
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Affiliation(s)
- Osmar N Silva
- Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília, DF, Brazil
| | - Octavio L Franco
- Centro de Análises Proteômicas e Bioquímicas, Universidade Católica de Brasília, Brasília, DF, Brazil
| | - Bruno J Neves
- Centro Universitário de Anápolis, UniEvangélica, Av. Universitária Km 3,5 Cidade Universitária Anápolis/GO 75083-515, Brazil
| | - Álice Cristina B Morais
- Centro Universitário de Anápolis, UniEvangélica, Av. Universitária Km 3,5 Cidade Universitária Anápolis/GO 75083-515, Brazil
| | - Jeronimo R De Oliveira Neto
- Núcleo de Estudos e Pesquisas Tóxico-Farmacológicas, Faculdade de Farmácia, Universidade Federal de Goiás, PMB 131, CEP 74001-970, Goiânia, Brazil
| | - Luiz Carlos da Cunha
- Núcleo de Estudos e Pesquisas Tóxico-Farmacológicas, Faculdade de Farmácia, Universidade Federal de Goiás, PMB 131, CEP 74001-970, Goiânia, Brazil
| | - Lara M Naves
- Instituto de Ciências Biológicas, Universidade Federal de Goiás, 74001-970, Goiânia, GO, Brazil
| | - Gustavo R Pedrino
- Instituto de Ciências Biológicas, Universidade Federal de Goiás, 74001-970, Goiânia, GO, Brazil
| | - Elson A Costa
- Instituto de Ciências Biológicas, Universidade Federal de Goiás, 74001-970, Goiânia, GO, Brazil
| | - James O Fajemiroye
- Centro Universitário de Anápolis, UniEvangélica, Av. Universitária Km 3,5 Cidade Universitária Anápolis/GO 75083-515, Brazil; Instituto de Ciências Biológicas, Universidade Federal de Goiás, 74001-970, Goiânia, GO, Brazil.
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Kim M, Acharya S, Botanas CJ, Custodio RJ, Lee HJ, Sayson LV, Abiero A, Lee YS, Cheong JH, Kim KM, Kim HJ. Catalpol and Mannitol, Two Components of Rehmannia glutinosa, Exhibit Anticonvulsant Effects Probably via GABA A Receptor Regulation. Biomol Ther (Seoul) 2020; 28:137-144. [PMID: 31739380 PMCID: PMC7059811 DOI: 10.4062/biomolther.2019.130] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 09/17/2019] [Accepted: 10/02/2019] [Indexed: 12/25/2022] Open
Abstract
Epilepsy is a brain disorder that affects millions of people worldwide and is usually managed using currently available antiepileptic drugs, which result in adverse effects and are ineffective in approximately 20–25% of patients. Thus, there is growing interest in the development of new antiepileptic drugs with fewer side effects. In a previous study, we showed that a Rehmannia glutinosa (RG) water extract has protective effects against electroshock- and pentylenetetrazol (PTZ)-induced seizures, with fewer side effects. In this study, the objective was to identify the RG components that are responsible for its anticonvulsant effects. Initially, a number of RG components (aucubin, acteoside, catalpol, and mannitol) were screened, and the anticonvulsant effects of different doses of catalpol, mannitol, and their combination on electroshock- and chemically (PTZ or strychnine)-induced seizures in mice, were further assessed. Gamma-aminobutyric acid (GABA) receptor binding assay and electroencephalography (EEG) analysis were conducted to identify the potential underlying drug mechanism. Additionally, treated mice were tested using open-field and rotarod tests. Catalpol, mannitol, and their combination increased threshold against electroshock-induced seizures, and decreased the percentage of seizure responses induced by PTZ, a GABA antagonist. GABA receptor binding assay results revealed that catalpol and mannitol are associated with GABA receptor activity, and EEG analysis provided evidence that catalpol and mannitol have anticonvulsant effects against PTZ-induced seizures. In summary, our results indicate that catalpol and mannitol have anticonvulsant properties, and may mediate the protective effects of RG against seizures.
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Affiliation(s)
- Mikyung Kim
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Srijan Acharya
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Chrislean Jun Botanas
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Raly James Custodio
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Hyun Jun Lee
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Leandro Val Sayson
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Arvie Abiero
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Yong Soo Lee
- Department of Pharmacology, College of Pharmacy, Duksung Women's University, Seoul 01369, Republic of Korea
| | - Jae Hoon Cheong
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
| | - Kyeong-Man Kim
- Department of Pharmacology, College of Pharmacy, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Hee Jin Kim
- Uimyung Research Institute for Neuroscience, Department of Pharmacy, Sahmyook University, Seoul 01795, Republic of Korea
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Witkin JM, Li G, Golani LK, Xiong W, Smith JL, Ping X, Rashid F, Jahan R, Cerne R, Cook JM, Jin X. The Positive Allosteric Modulator of α2/3-Containing GABA A Receptors, KRM-II-81, Is Active in Pharmaco-Resistant Models of Epilepsy and Reduces Hyperexcitability after Traumatic Brain Injury. J Pharmacol Exp Ther 2020; 372:83-94. [PMID: 31694876 PMCID: PMC6927408 DOI: 10.1124/jpet.119.260968] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 10/17/2019] [Indexed: 12/14/2022] Open
Abstract
The imidizodiazepine, 5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3-yl)oxazole (KRM-II-81), is selective for α2/3-containing GABAA receptors. KRM-II-81 dampens seizure activity in rodent models with enhanced efficacy and reduced motor-impairment compared with diazepam. In the present study, KRM-II-81 was studied in assays designed to detect antiepileptics with improved chances of impacting pharmaco-resistant epilepsies. The potential for reducing neural hyperactivity weeks after traumatic brain injury was also studied. KRM-II-81 suppressed convulsions in corneal-kindled mice. Mice with kainate-induced mesial temporal lobe seizures exhibited spontaneous recurrent hippocampal paroxysmal discharges that were significantly reduced by KRM-II-81 (15 mg/kg, orally). KRM-II-81 also decreased convulsions in rats undergoing amygdala kindling in the presence of lamotrigine (lamotrigine-insensitive model) (ED50 = 19 mg/kg, i.p.). KRM-II-81 reduced focal and generalized seizures in a kainate-induced chronic epilepsy model in rats (20 mg/kg, i.p., three times per day). In mice with damage to the left cerebral cortex by controlled-cortical impact, enduring neuronal hyperactivity was dampened by KRM-II-81 (10 mg/kg, i.p.) as observed through in vivo two-photon imaging of layer II/III pyramidal neurons in GCaMP6-expressing transgenic mice. No notable side effects emerged up to doses of 300 mg/kg KRM-II-81. Molecular modeling studies were conducted: docking in the binding site of the α1β3γ2L GABAA receptor showed that replacing the C8 chlorine atom of alprazolam with the acetylene of KRM-II-81 led to loss of the key interaction with α1His102, providing a structural rationale for its low affinity for α1-containing GABAA receptors compared with benzodiazepines such as alprazolam. Overall, these findings predict that KRM-II-81 has improved therapeutic potential for epilepsy and post-traumatic epilepsy. SIGNIFICANCE STATEMENT: We describe the effects of a relatively new orally bioavailable small molecule in rodent models of pharmaco-resistant epilepsy and traumatic brain injury. KRM-II-81 is more potent and generally more efficacious than standard-of-care antiepileptics. In silico docking experiments begin to describe the structural basis for the relative lack of motor impairment induced by KRM-II-81. KRM-II-81 has unique structural and anticonvulsant effects, predicting its potential as an improved antiepileptic drug and novel therapy for post-traumatic epilepsy.
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Affiliation(s)
- Jeffrey M Witkin
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Guanguan Li
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Lalit K Golani
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Wenhui Xiong
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Jodi L Smith
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Xingjie Ping
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Farjana Rashid
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Rajwana Jahan
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Rok Cerne
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - James M Cook
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
| | - Xiaoming Jin
- Department of Neurologic Surgery, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., R.C., X.J.); Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin (J.M.W., G.L., L.K.G., F.R., R.J., J.M.C.); Department of Anatomy, Cell Biology, and Physiology, Indiana University School of Medicine, Indianapolis, Indiana (W.X., X.P., X.J.); and Laboratory of Antiepileptic Drug Discovery, St. Vincent's Hospital, Indianapolis, Indiana (J.L.S.)
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Influence of midazolam premedication on intraoperative EEG signatures in elderly patients. Clin Neurophysiol 2019; 130:1673-1681. [PMID: 31351371 DOI: 10.1016/j.clinph.2019.05.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 04/23/2019] [Accepted: 05/30/2019] [Indexed: 12/25/2022]
Abstract
OBJECTIVE To investigate the influence of midazolam premedication on the EEG-spectrum before and during general anesthesia in elderly patients. METHODS Patients aged ≥65 years, undergoing elective surgery were included in this prospective observational study. A continuous pre- and intraoperative frontal EEG was recorded in patients who received premedication with midazolam (Mid, n = 15) and patients who did not (noMid, n = 30). Absolute power within the delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (12-25 Hz) frequency-bands was analyzed in EEG-sections before (pre-induction), and after induction of anesthesia with propofol (post-induction), as well as during general anesthesia with either propofol or volatile-anesthetics (intra-operative). RESULTS Pre-induction, α-power of Mid patients was lower compared with noMid-patients (α-power: Mid: -10.75 dB vs. noMid: -9.20 dB; p = 0.036). After induction of anesthesia Mid-patients displayed a stronger increase of frontal α-power resulting in higher absolute α-power at post-induction state, (α-power: Mid -3.56 dB vs. noMid: -6.69 dB; p = 0.004), which remained higher intraoperatively (α-power: Mid: -2.12 dB vs. noMid: -6.10 dB; p = 0.024). CONCLUSION Midazolam premedication alters the intraoperative EEG-spectrum in elderly patients. SIGNIFICANCE This finding provides further evidence for the role of GABAergic activation in the induction of elevated, frontal α-power during general anesthesia. TRIAL REGISTRY NUMBER NCT02265263. 23 September 2014. Principal investigator: Prof. Dr. med. Claudia Spies. (https://clinicaltrials.gov/ct2/show/NCT02265263).
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Özdemir Z, Sari S, Karakurt A, Dalkara S. Synthesis, anticonvulsant screening, and molecular modeling studies of new arylalkylimidazole oxime ether derivatives. Drug Dev Res 2018; 80:269-280. [DOI: 10.1002/ddr.21491] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 10/02/2018] [Accepted: 10/22/2018] [Indexed: 01/23/2023]
Affiliation(s)
- Zeynep Özdemir
- Faculty of Pharmacy, Department of Pharmaceutical ChemistryInonu University Malatya Turkey
| | - Suat Sari
- Faculty of Pharmacy, Department of Pharmaceutical ChemistryHacettepe University Ankara Turkey
| | - Arzu Karakurt
- Faculty of Pharmacy, Department of Pharmaceutical ChemistryInonu University Malatya Turkey
| | - Sevim Dalkara
- Faculty of Pharmacy, Department of Pharmaceutical ChemistryHacettepe University Ankara Turkey
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Synthesis, anticonvulsant activity, and molecular modeling studies of novel 1-phenyl/1-(4-chlorophenyl)-2-(1H-triazol-1-yl)ethanol ester derivatives. Med Chem Res 2018. [DOI: 10.1007/s00044-018-2225-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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De N, Song CE, Ryu DH, Yoo EJ. Gold-catalyzed [5+2] cycloaddition of quinolinium zwitterions and allenamides as an efficient route to fused 1,4-diazepines. Chem Commun (Camb) 2018; 54:6911-6914. [PMID: 29845164 DOI: 10.1039/c8cc02570c] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herein, we demonstrate a new catalytic cycloaddition of quinolinium zwitterions involving a gold-bound allylic cation intermediate. This ligand-free higher-order cycloaddition efficiently affords a variety of fused 1,4-diazepine derivatives in a stereospecific manner at room temperature.
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Affiliation(s)
- Nirupam De
- Department of Applied Chemistry, Kyung Hee University, Yongin, 17104, Korea
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10
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Sari S, Dalkara S, Kaynak FB, Reynisson J, Saraç S, Karakurt A. New Anti-Seizure (Arylalkyl)azole Derivatives: Synthesis,In VivoandIn SilicoStudies. Arch Pharm (Weinheim) 2017; 350. [DOI: 10.1002/ardp.201700043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/20/2017] [Accepted: 03/27/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Suat Sari
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry; Hacettepe University; Ankara Turkey
| | - Sevim Dalkara
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry; Hacettepe University; Ankara Turkey
| | - Filiz Betül Kaynak
- Faculty of Engineering, Department of Physics Engineering; Hacettepe University; Ankara Turkey
| | - Jóhannes Reynisson
- School of Chemical Sciences; University of Auckland; Auckland New Zealand
| | - Selma Saraç
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry; Hacettepe University; Ankara Turkey
| | - Arzu Karakurt
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry; Inonu University; Malatya Turkey
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11
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Sari S, Karakurt A, Uslu H, Kaynak FB, Çalış Ü, Dalkara S. New (arylalkyl)azole derivatives showing anticonvulsant effects could have VGSC and/or GABA AR affinity according to molecular modeling studies. Eur J Med Chem 2016; 124:407-416. [PMID: 27597416 DOI: 10.1016/j.ejmech.2016.08.032] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 07/11/2016] [Accepted: 08/14/2016] [Indexed: 01/06/2023]
Abstract
(Arylalkyl)azoles (AAAs) emerged as a novel class of antiepileptic agents with the invention of nafimidone and denzimol. Several AAA derivatives with potent anticonvulsant activities have been reported so far, however neurotoxicity was usually an issue. We prepared a set of ester derivatives of 1-(2-naphthyl)-2-(1H-1,2,4-triazol-1-yl)ethanone oxime and evaluated their anticonvulsant and neurotoxic effects in mice. Most of our compounds were protective against maximal electroshock (MES)- and/or subcutaneous metrazol (s.c. MET)-induced seizures whereas none of them showed neurotoxicity. Nafimidone and denzimol have an activity profile similar to that of phenytoin or carbamazepine, both of which are known to inhibit voltage-gated sodium channels (VGSCs) as well as to enhance γ-aminobutiric acid (GABA)-mediated response. In order to get insights into the effects of our compounds on VGSCs and A-type GABA receptors (GABAARs) we performed docking studies using homology model of Na+ channel inner pore and GABAAR as docking scaffolds. We found that our compounds bind VGSCs in similar ways as phenytoin, carbamazepine, and lamotrigine. They showed strong affinity to benzodiazepine (BZD) binding site and their binding interactions were mainly complied with the experimental data and the reported BZD binding model.
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Affiliation(s)
- Suat Sari
- Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06100, Ankara, Turkey
| | - Arzu Karakurt
- İnönü University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 44280, Malatya, Turkey.
| | - Harun Uslu
- İnönü University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 44280, Malatya, Turkey
| | - F Betül Kaynak
- Hacettepe University, Faculty of Engineering, Department of Physics Engineering, 06532, Ankara, Turkey
| | - Ünsal Çalış
- Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06100, Ankara, Turkey
| | - Sevim Dalkara
- Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06100, Ankara, Turkey
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12
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Dixon CL, Harrison NL, Lynch JW, Keramidas A. Zolpidem and eszopiclone prime α1β2γ2 GABAA receptors for longer duration of activity. Br J Pharmacol 2015; 172:3522-36. [PMID: 25817320 DOI: 10.1111/bph.13142] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/23/2015] [Accepted: 03/22/2015] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND AND PURPOSE GABAA receptors mediate neuronal inhibition in the brain. They are the primary targets for benzodiazepines, which are widely used to treat neurological disorders including anxiety, epilepsy and insomnia. The mechanism by which benzodiazepines enhance GABAA receptor activity has been extensively studied, but there is little mechanistic information on how non-benzodiazepine drugs that bind to the same site exert their effects. Eszopiclone and zolpidem are two non-benzodiazepine drugs for which no mechanism of action has yet been proposed, despite their clinical importance as sleeping aids. Here we investigate how both drugs enhance the activity of α1β2γ2 GABAA receptors. EXPERIMENTAL APPROACH We used rapid ligand application onto macropatches and single-channel kinetic analysis to assess rates of current deactivation. We also studied synaptic currents in primary neuronal cultures and in heterosynapses, whereby native GABAergic nerve terminals form synapses with HEK293 cells expressing α1β2γ2 GABAA receptors. Drug binding and modulation was quantified with the aid of an activation mechanism. KEY RESULTS At the single-channel level, the drugs prolonged the duration of receptor activation, with similar KD values of ∼80 nM. Channel activation was prolonged primarily by increasing the equilibrium constant between two connected shut states that precede channel opening. CONCLUSIONS AND IMPLICATIONS As the derived mechanism successfully simulated the effects of eszopiclone and zolpidem on ensemble currents, we propose it as the definitive mechanism accounting for the effects of both drugs. Importantly, eszopiclone and zolpidem enhanced GABAA receptor currents via a mechanism that differs from that proposed for benzodiazepines.
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Affiliation(s)
- Christine L Dixon
- Queensland Brain Institute, University of Queensland, Brisbane, Qld, Australia
| | - Neil L Harrison
- Department of Anesthesiology and Department of Pharmacology, Columbia University, New York, NY, USA
| | - Joseph W Lynch
- Queensland Brain Institute, University of Queensland, Brisbane, Qld, Australia.,School of Biomedical Sciences, University of Queensland, Brisbane, Qld, Australia
| | - Angelo Keramidas
- Queensland Brain Institute, University of Queensland, Brisbane, Qld, Australia.,Department of Anesthesiology and Department of Pharmacology, Columbia University, New York, NY, USA
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Beltrán González AN, Pomata PE, Goutman JD, Gasulla J, Chebib M, Calvo DJ. Benzodiazepine modulation of homomeric GABAAρ1 receptors: differential effects of diazepam and 4'-chlorodiazepam. Eur J Pharmacol 2014; 743:24-30. [PMID: 25246015 DOI: 10.1016/j.ejphar.2014.09.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/09/2014] [Accepted: 09/10/2014] [Indexed: 11/26/2022]
Abstract
GABA(A) receptors (GABA(A)Rs) are ligand-gated ion channels that mediate inhibitory neurotransmission in the central nervous system (CNS). They are members of the Cys-loop receptor family and display marked structural and functional heterogeneity. Many GABA(A)Rs receptor subtypes are allosterically modulated by benzodiazepines (BDZs), which are drugs extensively used as anxiolytics, sedative-hypnotics and anticonvulsants. One high-affinity site and at least three additional low-affinity sites for BDZ recognition have been identified in several heteromeric and homomeric variants of the GABA(A)Rs (e.g.: α1β2γ2, α1β2/3, β3, etc.). However, the modulation of homomeric GABA(A)ρRs by BDZs was not previously revealed, and these receptors, for a long a time, were assumed to be fully insensitive to the actions of these drugs. In the present study, human homomeric GABA(A)ρ1 receptors were expressed in Xenopus oocytes and GABA-evoked responses electrophysiologically recorded in the presence or absence of BDZs. GABA(A)ρ1 receptor-mediated responses were modulated by diazepam and 4'-chlorodiazepam in the micromolar range, in a concentration-dependent, voltage-independent and reversible manner. Diazepam produced potentiating effects on GABA-evoked Cl(-) currents and 4'-Cl diazepam induced biphasic effects depending on the GABA concentration, whereas Ro15-4513 and alprazolam were negative modulators. BDZ actions were insensitive to flumazenil. Other BDZs showed negligible activity at equivalent experimental conditions. Our results suggest that GABA(A)ρ1 receptor function can be selectively and differentially modulated by BDZs.
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Affiliation(s)
- Andrea N Beltrán González
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina
| | - Pablo E Pomata
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina
| | - Juan D Goutman
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina
| | - Javier Gasulla
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina
| | - Mary Chebib
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina
| | - Daniel J Calvo
- Laboratorio de Neurobiología Celular y Molecular, Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Ciudad Autónoma de Buenos Aires CP 1428, Argentina.
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Synthesis, anticonvulsant, sedative and anxiolytic activities of novel annulated pyrrolo[1,4]benzodiazepines. Int J Mol Sci 2014; 15:16500-10. [PMID: 25238414 PMCID: PMC4200843 DOI: 10.3390/ijms150916500] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 11/16/2022] Open
Abstract
Four new pentacyclic benzodiazepine derivatives (PBDTs 13–16) were synthesized by conventional thermal heating and microwave-assisted intramolecular cyclocondensation. Their anticonvulsant, sedative and anxiolytic activities were evaluated by drug-induced convulsion models, a pentobarbital-induced hypnotic model and an elevated plus maze in mice. PBDT 13, a triazolopyrrolo[2,1-c][1,4]benzodiazepin-8-one fused with a thiadiazolone ring, exhibited the best anticonvulsant, sedative and anxiolytic effects in our tests. There was no significant difference in potency between PBDT 13 and diazepam, and we proposed that the action mechanism of PBDT 13 could be similar to that of diazepam via benzodiazepine receptors.
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Middendorp SJ, Puthenkalam R, Baur R, Ernst M, Sigel E. Accelerated discovery of novel benzodiazepine ligands by experiment-guided virtual screening. ACS Chem Biol 2014; 9:1854-9. [PMID: 24960548 DOI: 10.1021/cb5001873] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
High throughput discovery of ligand scaffolds for target proteins can accelerate development of leads and drug candidates enormously. Here we describe an innovative workflow for the discovery of high affinity ligands for the benzodiazepine-binding site on the so far not crystallized mammalian GABAA receptors. The procedure includes chemical biology techniques that may be generally applied to other proteins. Prerequisites are a ligand that can be chemically modified with cysteine-reactive groups, knowledge of amino acid residues contributing to the drug-binding pocket, and crystal structures either of proteins homologous to the target protein or, better, of the target itself. Part of the protocol is virtual screening that without additional rounds of optimization in many cases results only in low affinity ligands, even when a target protein has been crystallized. Here we show how the integration of functional data into structure-based screening dramatically improves the performance of the virtual screening. Thus, lead compounds with 14 different scaffolds were identified on the basis of an updated structural model of the diazepam-bound state of the GABAA receptor. Some of these compounds show considerable preference for the α3β2γ2 GABAA receptor subtype.
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Affiliation(s)
- Simon J. Middendorp
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
| | - Roshan Puthenkalam
- Department
of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria
| | - Roland Baur
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
| | - Margot Ernst
- Department
of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria
| | - Erwin Sigel
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
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16
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Middendorp SJ, Hurni E, Schönberger M, Stein M, Pangerl M, Trauner D, Sigel E. Relative positioning of classical benzodiazepines to the γ2-subunit of GABAA receptors. ACS Chem Biol 2014; 9:1846-53. [PMID: 24918742 DOI: 10.1021/cb500186a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
GABAA receptors are the major inhibitory neurotransmitter receptors in the brain. Benzodiazepine exert their action via a high affinity-binding site at the α/γ subunit interface on some of these receptors. Diazepam has sedative, hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects. It acts by potentiating the current evoked by the agonist GABA. Understanding specific interaction of benzodiazepines in the binding pocket of different GABAA receptor isoforms might help to separate these divergent effects. As a first step, we characterized the interaction between diazepam and the major GABAA receptor isoform α1β2γ2. We mutated several amino acid residues on the γ2-subunit assumed to be located near or in the benzodiazepine binding pocket individually to cysteine and studied the interaction with three ligands that are modified with a cysteine-reactive isothiocyanate group (-NCS). When the reactive NCS group is in apposition to the cysteine residue this leads to a covalent reaction. In this way, three amino acid residues, γ2Tyr58, γ2Asn60, and γ2Val190 were located relative to classical benzodiazepines in their binding pocket on GABAA receptors.
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Affiliation(s)
- Simon J. Middendorp
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
| | - Evelyn Hurni
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
| | - Matthias Schönberger
- Department
of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, 81377 Munich, Germany
| | - Marco Stein
- Department
of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, 81377 Munich, Germany
| | - Michael Pangerl
- Department
of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, 81377 Munich, Germany
| | - Dirk Trauner
- Department
of Chemistry, Ludwig-Maximilians-Universität München and Center of Integrated Protein Science, 81377 Munich, Germany
| | - Erwin Sigel
- Institute
of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland
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17
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Evidence for the participation of peripheral α5 subunit-containing GABAA receptors in GABAA agonists-induced nociception in rats. Eur J Pharmacol 2014; 734:91-7. [DOI: 10.1016/j.ejphar.2014.03.051] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/11/2014] [Accepted: 03/22/2014] [Indexed: 11/17/2022]
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18
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Wallner M, Hanchar HJ, Olsen RW. Alcohol selectivity of β3-containing GABAA receptors: evidence for a unique extracellular alcohol/imidazobenzodiazepine Ro15-4513 binding site at the α+β- subunit interface in αβ3δ GABAA receptors. Neurochem Res 2014; 39:1118-26. [PMID: 24500446 DOI: 10.1007/s11064-014-1243-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/13/2014] [Accepted: 01/17/2014] [Indexed: 01/08/2023]
Abstract
GABAA receptors (GABARs) have long been the focus for acute alcohol actions with evidence for behaviorally relevant low millimolar alcohol actions on tonic GABA currents and extrasynaptic α4/6, δ, and β3 subunit-containing GABARs. Using recombinant expression in oocytes combined with two electrode voltage clamp, we show with chimeric β2/β3 subunits that differences in alcohol sensitivity among β subunits are determined by the extracellular N-terminal part of the protein. Furthermore, by using point mutations, we show that the β3 alcohol selectivity is determined by a single amino acid residue in the N-terminus that differs between GABAR β subunits (β3Y66, β2A66, β1S66). The β3Y66 residue is located in a region called "loop D" which in γ subunits contributes to the imidazobenzodiazepine (iBZ) binding site at the classical α+γ2- subunit interface. In structural homology models β3Y66 is the equivalent of γ2T81 which is one of three critical residues lining the benzodiazepine binding site in the γ2 subunit loop D, opposite to the "100H/R-site" benzodiazepine binding residue in GABAR α subunits. We have shown that the α6R100Q mutation at this site leads to increased alcohol-induced motor in-coordination in alcohol non-tolerant rats carrying the α6R100Q mutated allele. Based on the identification of these two amino acid residues α6R100 and β66 we propose a model in which β3 and δ containing GABA receptors contain a unique ethanol site at the α4/6+β3- subunit interface. This site is homologous to the classical benzodiazepine binding site and we propose that it not only binds ethanol at relevant concentrations (EC50-17 mM), but also has high affinity for a few selected benzodiazepine site ligands including alcohol antagonistic iBZs (Ro15-4513, RY023, RY024, RY80) which have in common a large moiety at the C7 position of the benzodiazepine ring. We suggest that large moieties at the C7-BZ ring compete with alcohol for its binding pocket at a α4/6+β3- EtOH/Ro15-4513 site. This model reconciles many years of alcohol research on GABARs and provides a plausible explanation for the competitive relationship between ethanol and iBZ alcohol antagonists in which bulky moieties at the C7 position compete with ethanol for its binding site. We conclude with a critical discussion to suggest that much of the controversy surrounding this issue might be due to fundamental species differences in alcohol and alcohol antagonist responses in rats and mice.
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Affiliation(s)
- M Wallner
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Room 23-338 CHS, Charles Young Drive South, Los Angeles, CA, 90095-1735, USA,
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Jensen ML, Wafford KA, Brown AR, Belelli D, Lambert JJ, Mirza NR. A study of subunit selectivity, mechanism and site of action of the delta selective compound 2 (DS2) at human recombinant and rodent native GABA(A) receptors. Br J Pharmacol 2013; 168:1118-32. [PMID: 23061935 DOI: 10.1111/bph.12001] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 07/18/2012] [Accepted: 08/23/2012] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND AND PURPOSE Most GABA(A) receptor subtypes comprise 2α, 2β and 1γ subunit, although for some isoforms, a δ replaces a γ-subunit. Extrasynaptic δ-GABA(A) receptors are important therapeutic targets, but there are few suitable pharmacological tools. We profiled DS2, the purported positive allosteric modulator (PAM) of δ-GABA(A) receptors to better understand subtype selectivity, mechanism/site of action and activity at native δ-GABA(A) receptors. EXPERIMENTAL APPROACH Subunit specificity of DS2 was determined using electrophysiological recordings of Xenopus laevis oocytes expressing human recombinant GABA(A) receptor isoforms. Effects of DS2 on GABA concentration-response curves were assessed to define mechanisms of action. Radioligand binding and electrophysiology utilising mutant receptors and pharmacology were used to define site of action. Using brain-slice electrophysiology, we assessed the influence of DS2 on thalamic inhibition in wild-type and δ(0/0) mice. KEY RESULTS Actions of DS2 were primarily determined by the δ-subunit but were additionally influenced by the α, but not the β, subunit (α4/6βxδ > α1βxδ >> γ2-GABA(A) receptors > α4β3). For δ-GABA(A) receptors, DS2 enhanced maximum responses to GABA, with minimal influence on GABA potency. (iii) DS2 did not act via the orthosteric, or known modulatory sites on GABA(A) receptors. (iv) DS2 enhanced tonic currents of thalamocortical neurones from wild-type but not δ(0/0) mice. CONCLUSIONS AND IMPLICATIONS DS2 is the first PAM selective for α4/6βxδ receptors, providing a novel tool to investigate extrasynaptic δ-GABA(A) receptors. The effects of DS2 are mediated by an unknown site leading to GABA(A) receptor isoform selectivity.
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The benzodiazepine diazepam potentiates responses of α1β2γ2L γ-aminobutyric acid type A receptors activated by either γ-aminobutyric acid or allosteric agonists. Anesthesiology 2013; 118:1417-25. [PMID: 23407108 DOI: 10.1097/aln.0b013e318289bcd3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The γ-aminobutyric acid (GABA) type A receptor is a target for several anesthetics, anticonvulsants, anxiolytics, and sedatives. Neurosteroids, barbiturates, and etomidate both potentiate responses to GABA and allosterically activate the receptor. We examined the ability of a benzodiazepine, diazepam, to potentiate responses to allosteric agonists. METHODS The GABA type A receptors were expressed in human embryonic kidney 293 cells and studied using whole-cell and single-channel patch clamp. The receptors were activated by the orthosteric agonist GABA and allosteric agonists pentobarbital, etomidate, and alfaxalone. RESULTS Diazepam is equally potent at enhancing responses to orthosteric and allosteric agonists. Diazepam EC50s were 25 ± 4, 26 ± 6, 33 ± 6, and 26 ± 3 nm for receptors activated by GABA, pentobarbital, etomidate, and alfaxalone, respectively (mean ± SD, 5-6 cells at each condition). Mutations to the benzodiazepine-binding site (α1(H101C), γ2(R144C), γ2(R197C)) reduced or removed potentiation for all agonists, and an inverse agonist at the benzodiazepine site reduced responses to all agonists. Single-channel data elicited by GABA demonstrate that in the presence of 1 μm diazepam the prevalence of the longest open-time component is increased from 13 ± 7 (mean ± SD, n = 5 patches) to 27 ± 8% (n = 3 patches) and the rate of channel closing is decreased from 129 ± 28 s(-1) to 47 ± 6 s(-1) (mean ± SD) CONCLUSIONS: We conclude that benzodiazepines do not act by enhancing affinity of the orthosteric site for GABA but rather by increasing channel gating efficacy. The results also demonstrate the presence of interactions between allosteric activators and potentiators, raising a possibility of effects on dosage requirements or changes in side effects.
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A unified model of the GABA(A) receptor comprising agonist and benzodiazepine binding sites. PLoS One 2013; 8:e52323. [PMID: 23308109 PMCID: PMC3538749 DOI: 10.1371/journal.pone.0052323] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 11/16/2012] [Indexed: 11/19/2022] Open
Abstract
We present a full-length α(1)β(2)γ(2) GABA receptor model optimized for agonists and benzodiazepine (BZD) allosteric modulators. We propose binding hypotheses for the agonists GABA, muscimol and THIP and for the allosteric modulator diazepam (DZP). The receptor model is primarily based on the glutamate-gated chloride channel (GluCl) from C. elegans and includes additional structural information from the prokaryotic ligand-gated ion channel ELIC in a few regions. Available mutational data of the binding sites are well explained by the model and the proposed ligand binding poses. We suggest a GABA binding mode similar to the binding mode of glutamate in the GluCl X-ray structure. Key interactions are predicted with residues α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and the backbone of β(2)S156. Muscimol is predicted to bind similarly, however, with minor differences rationalized with quantum mechanical energy calculations. Muscimol key interactions are predicted to be α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and β(2)F200. Furthermore, we argue that a water molecule could mediate further interactions between muscimol and the backbone of β(2)S156 and β(2)Y157. DZP is predicted to bind with interactions comparable to those of the agonists in the orthosteric site. The carbonyl group of DZP is predicted to interact with two threonines α(1)T206 and γ(2)T142, similar to the acidic moiety of GABA. The chlorine atom of DZP is placed near the important α(1)H101 and the N-methyl group near α(1)Y159, α(1)T206, and α(1)Y209. We present a binding mode of DZP in which the pending phenyl moiety of DZP is buried in the binding pocket and thus shielded from solvent exposure. Our full length GABA(A) receptor is made available as Model S1.
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Abstract
The GABA(A) receptors are the major inhibitory neurotransmitter receptors in mammalian brain. Each isoform consists of five homologous or identical subunits surrounding a central chloride ion-selective channel gated by GABA. How many isoforms of the receptor exist is far from clear. GABA(A) receptors located in the postsynaptic membrane mediate neuronal inhibition that occurs in the millisecond time range; those located in the extrasynaptic membrane respond to ambient GABA and confer long-term inhibition. GABA(A) receptors are responsive to a wide variety of drugs, e.g. benzodiazepines, which are often used for their sedative/hypnotic and anxiolytic effects.
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Affiliation(s)
- Erwin Sigel
- Institute of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Bern, Switzerland.
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Pentameric ligand-gated ion channel ELIC is activated by GABA and modulated by benzodiazepines. Proc Natl Acad Sci U S A 2012; 109:E3028-34. [PMID: 23035248 DOI: 10.1073/pnas.1208208109] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GABA(A) receptors are pentameric ligand-gated ion channels involved in fast inhibitory neurotransmission and are allosterically modulated by the anxiolytic, anticonvulsant, and sedative-hypnotic benzodiazepines. Here we show that the prokaryotic homolog ELIC also is activated by GABA and is modulated by benzodiazepines with effects comparable to those at GABA(A) receptors. Crystal structures reveal important features of GABA recognition and indicate that benzodiazepines, depending on their concentration, occupy two possible sites in ELIC. An intrasubunit site is adjacent to the GABA-recognition site but faces the channel vestibule. A second intersubunit site partially overlaps with the GABA site and likely corresponds to a low-affinity benzodiazepine-binding site in GABA(A) receptors that mediates inhibitory effects of the benzodiazepine flurazepam. Our study offers a structural view how GABA and benzodiazepines are recognized at a GABA-activated ion channel.
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Lemoine D, Jiang R, Taly A, Chataigneau T, Specht A, Grutter T. Ligand-gated ion channels: new insights into neurological disorders and ligand recognition. Chem Rev 2012; 112:6285-318. [PMID: 22988962 DOI: 10.1021/cr3000829] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Damien Lemoine
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 CNRS, Conception et Application de Molécules Bioactives, Faculté de Pharmacie, Université de Strasbourg , 67400 Illkirch, France
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25
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Lüscher BP, Baur R, Goeldner M, Sigel E. Influence of GABA(A) receptor α subunit isoforms on the benzodiazepine binding site. PLoS One 2012; 7:e42101. [PMID: 22848717 PMCID: PMC3407089 DOI: 10.1371/journal.pone.0042101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 07/02/2012] [Indexed: 11/20/2022] Open
Abstract
Classical benzodiazepines, such as diazepam, interact with αxβ2γ2 GABAA receptors, x = 1, 2, 3, 5 and modulate their function. Modulation of different receptor isoforms probably results in selective behavioural effects as sedation and anxiolysis. Knowledge of differences in the structure of the binding pocket in different receptor isoforms is of interest for the generation of isoform-specific ligands. We studied here the interaction of the covalently reacting diazepam analogue 3-NCS with α1S204Cβ2γ2, α1S205Cβ2γ2 and α1T206Cβ2γ2 and with receptors containing the homologous mutations in α2β2γ2, α3β2γ2, α5β1/2γ2 and α6β2γ2. The interaction was studied using radioactive ligand binding and at the functional level using electrophysiological techniques. Both strategies gave overlapping results. Our data allow conclusions about the relative apposition of α1S204Cβ2γ2, α1S205Cβ2γ2 and α1T206Cβ2γ2 and homologous positions in α2, α3, α5 and α6 with C-atom adjacent to the keto-group in diazepam. Together with similar data on the C-atom carrying Cl in diazepam, they indicate that the architecture of the binding site for benzodiazepines differs in each GABAA receptor isoform α1β2γ2, α2β2γ2, α3β2γ2, α5β1/2γ2 and α6β2γ2.
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Affiliation(s)
- Benjamin P. Lüscher
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Roland Baur
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Maurice Goeldner
- Laboratoire de Conception et Application de Molécules Bioactives, Unité Mixte de Recherche CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Erwin Sigel
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
- * E-mail:
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26
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Richter L, de Graaf C, Sieghart W, Varagic Z, Mörzinger M, de Esch IJP, Ecker GF, Ernst M. Diazepam-bound GABAA receptor models identify new benzodiazepine binding-site ligands. Nat Chem Biol 2012; 8:455-64. [PMID: 22446838 DOI: 10.1038/nchembio.917] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 02/02/2012] [Indexed: 11/09/2022]
Abstract
Benzodiazepines exert their anxiolytic, anticonvulsant, muscle-relaxant and sedative-hypnotic properties by allosterically enhancing the action of GABA at GABA(A) receptors via their benzodiazepine-binding site. Although these drugs have been used clinically since 1960, the molecular basis of this interaction is still not known. By using multiple homology models and an unbiased docking protocol, we identified a binding hypothesis for the diazepam-bound structure of the benzodiazepine site, which was confirmed by experimental evidence. Moreover, two independent virtual screening approaches based on this structure identified known benzodiazepine-site ligands from different structural classes and predicted potential new ligands for this site. Receptor-binding assays and electrophysiological studies on recombinant receptors confirmed these predictions and thus identified new chemotypes for the benzodiazepine-binding site. Our results support the validity of the diazepam-bound structure of the benzodiazepine-binding pocket, demonstrate its suitability for drug discovery and pave the way for structure-based drug design.
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Affiliation(s)
- Lars Richter
- Department of Medicinal Chemistry, University of Vienna, Vienna, Austria
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27
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Charon S, Taly A, Rodrigo J, Perret P, Goeldner M. Binding modes of noncompetitive GABA-channel blockers revisited using engineered affinity-labeling reactions combined with new docking studies. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:2803-2807. [PMID: 20839772 DOI: 10.1021/jf102468n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The binding modes of noncompetitive GABA(A)-channel blockers were re-examined taking into account the recent description of the 3D structure of prokaryotic pentameric ligand-gated ion channels, which provided access to new mammalian or insect GABA receptor models, emphasizing their transmembrane portion. Two putative binding modes were deciphered for this class of compounds, including the insecticide fipronil, located nearby either the intra- or the extracellular part of the membrane, respectively. These results are in full agreement with previously described affinity-labeling reactions performed with GABA(A) noncompetitive blockers (Perret et al. J. Biol. Chem.1999, 274, 25350-25354).
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Affiliation(s)
- Sébastien Charon
- Laboratoire de Chimie Bioorganique, CNRS-UMR 7199, Faculté de Pharmacie, Université de Strasbourg, Strasbourg, France
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28
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Morlock EV, Czajkowski C. Different residues in the GABAA receptor benzodiazepine binding pocket mediate benzodiazepine efficacy and binding. Mol Pharmacol 2011; 80:14-22. [PMID: 21447642 DOI: 10.1124/mol.110.069542] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Benzodiazepines (BZDs) exert their therapeutic actions by binding to the GABA(A) receptor (GABA(A)R) and allosterically modulating GABA-induced chloride currents (I(GABA)). A variety of ligands with divergent structures bind to the BZD site, and the structural mechanisms that couple their binding to potentiation of I(GABA) are not well understood. In this study, we measured the effects of individually mutating 22 residues throughout the BZD binding pocket on the abilities of eszopiclone, zolpidem, and flurazepam to potentiate I(GABA). Wild-type and mutant α(1)β(2)γ(2) GABA(A)Rs were expressed in Xenopus laevis oocytes and analyzed using a two-electrode voltage clamp. GABA EC(50), BZD EC(50), and BZD maximal potentiation were measured. These data, combined with previous radioligand binding data describing the mutations' effects on BZD apparent binding affinities (J Neurosci 28:3490-3499, 2008; J Med Chem 51:7243-7252, 2008), were used to distinguish residues within the BZD pocket that contribute to BZD efficacy and BZD binding. We identified six residues whose mutation altered BZD maximal potentiation of I(GABA) (BZD efficacy) without altering BZD binding apparent affinity, three residues whose mutation altered binding but had no effect on BZD efficacy, and four residues whose mutation affected both binding and efficacy. Moreover, depending on the BZD ligand, the effects of some mutations were different, indicating that the structural mechanisms underlying the ability of BZD ligands with divergent structures to potentiate I(GABA) are distinct.
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Affiliation(s)
- Elaine V Morlock
- University of Wisconsin at Madison, 601 Science Drive, Madison, WI 53711, USA
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29
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Abstract
Cys-loop receptors are membrane-spanning neurotransmitter-gated ion channels that are responsible for fast excitatory and inhibitory transmission in the peripheral and central nervous systems. The best studied members of the Cys-loop family are nACh, 5-HT3, GABAA and glycine receptors. All these receptors share a common structure of five subunits, pseudo-symmetrically arranged to form a rosette with a central ion-conducting pore. Some are cation selective (e.g. nACh and 5-HT3) and some are anion selective (e.g. GABAA and glycine). Each receptor has an extracellular domain (ECD) that contains the ligand-binding sites, a transmembrane domain (TMD) that allows ions to pass across the membrane, and an intracellular domain (ICD) that plays a role in channel conductance and receptor modulation. Cys-loop receptors are the targets for many currently used clinically relevant drugs (e.g. benzodiazepines and anaesthetics). Understanding the molecular mechanisms of these receptors could therefore provide the catalyst for further development in this field, as well as promoting the development of experimental techniques for other areas of neuroscience.In this review, we present our current understanding of Cys-loop receptor structure and function. The ECD has been extensively studied. Research in this area has been stimulated in recent years by the publication of high-resolution structures of nACh receptors and related proteins, which have permitted the creation of many Cys loop receptor homology models of this region. Here, using the 5-HT3 receptor as a typical member of the family, we describe how homology modelling and ligand docking can provide useful but not definitive information about ligand interactions. We briefly consider some of the many Cys-loop receptors modulators. We discuss the current understanding of the structure of the TMD, and how this links to the ECD to allow channel gating, and consider the roles of the ICD, whose structure is poorly understood. We also describe some of the current methods that are beginning to reveal the differences between different receptor states, and may ultimately show structural details of transitions between them.
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30
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Hanek AP, Lester HA, Dougherty DA. Photochemical proteolysis of an unstructured linker of the GABAAR extracellular domain prevents GABA but not pentobarbital activation. Mol Pharmacol 2010; 78:29-35. [PMID: 20363860 DOI: 10.1124/mol.109.059832] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The GABA type A receptor (GABA(A)R) is the major inhibitory receptor in the mammalian central nervous system and the target of numerous pharmaceuticals. The alpha-subunit of these pentameric Cys-loop neurotransmitter-gated ion channels contributes to the binding of both GABA and allosteric modulators such as the benzodiazepines, suggesting a role for this subunit in the conformational changes associated with activation of the receptor. Herein we use the nonsense suppression methodology to incorporate a photoactivatable unnatural amino acid and photochemically cleave the backbone of the alpha subunit of the alpha(1)beta(2) GABA(A)R in a linker region that is believed to span the subunit. Proteolytic cleavage impairs GABA but not pentobarbital activation, strongly suggesting that conformational changes involving this linker region are critical to the GABA activation pathway.
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Affiliation(s)
- Ariele P Hanek
- Division of Chemistry and Chemical Engineering, Division of Biology, California Institute of Technology, Pasadena, California, USA
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31
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Tan KR, Baur R, Charon S, Goeldner M, Sigel E. Relative positioning of diazepam in the benzodiazepine-binding-pocket of GABA receptors. J Neurochem 2009; 111:1264-73. [PMID: 19804380 DOI: 10.1111/j.1471-4159.2009.06419.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
GABA(A) receptors are the major inhibitory neurotransmitter receptors in the brain. Some of them are targets of benzodiazepines that are widely used in clinical practice for their sedative/hypnotic, anxiolytic, muscle relaxant and anticonvulsant effects. In order to rationally separate these different drug actions, we need to understand the interaction of such compounds with the benzodiazepine-binding pocket. With this aim, we mutated residues located in the benzodiazepine-binding site individually to cysteine. These mutated receptors were combined with benzodiazepine site ligands carrying a cysteine reactive group in a defined position. Proximal apposition of reaction partners will lead to a covalent reaction. We describe here such proximity-accelerated chemical coupling reactions of alpha(1)S205C and alpha(1)T206C with a diazepam derivative modified at the C-3 position with a reactive isothiocyanate group (-NCS). We also provide new data that identify alpha(1)H101C and alpha(1)N102C as exclusive sites of the reaction of a diazepam derivative where the -Cl atom is replaced by a -NCS group. Based on these observations we propose a relative positioning of diazepam within the benzodiazepine-binding site of alpha(1)beta(2)gamma(2) receptors.
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Affiliation(s)
- Kelly R Tan
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse, Switzerland
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32
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Law RJ, Lightstone FC. Gaba Receptor Insecticide Non-Competitive Antagonists May Bind at Allosteric Modulator Sites. Int J Neurosci 2009; 118:705-34. [DOI: 10.1080/00207450701750216] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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33
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Berezhnoy D, Gibbs TT, Farb DH. Docking of 1,4-benzodiazepines in the alpha1/gamma2 GABA(A) receptor modulator site. Mol Pharmacol 2009; 76:440-50. [PMID: 19483108 DOI: 10.1124/mol.109.054650] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Positive allosteric modulation of the GABA(A) receptor (GABA(A)R) via the benzodiazepine recognition site is the mechanism whereby diverse chemical classes of therapeutic agents act to reduce anxiety, induce and maintain sleep, reduce seizures, and induce conscious sedation. The binding of such therapeutic agents to this allosteric modulatory site increases the affinity of GABA for the agonist recognition site. A major unanswered question, however, relates to how positive allosteric modulators dock in the 1,4-benzodiazepine (BZD) recognition site. In the present study, the X-ray structure of an acetylcholine binding protein from the snail Lymnea stagnalis and the results from site-directed affinity-labeling studies were used as the basis for modeling of the BZD binding pocket at the alpha(1)/gamma(2) subunit interface. A tethered BZD was introduced into the binding pocket, and molecular simulations were carried out to yield a set of candidate orientations of the BZD ligand in the binding pocket. Candidate orientations were refined based on known structure-activity and stereospecificity characteristics of BZDs and the impact of the alpha(1)H101R mutation. Results favor a model in which the BZD molecule is oriented such that the C5-phenyl substituent extends approximately parallel to the plane of the membrane rather than parallel to the ion channel. Application of this computational modeling strategy, which integrates site-directed affinity labeling with structure-activity knowledge to create a molecular model of the docking of active ligands in the binding pocket, may provide a basis for the design of more selective GABA(A)R modulators with enhanced therapeutic potential.
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Affiliation(s)
- D Berezhnoy
- Laboratory of Molecular Neurobiology, Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA
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34
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Hanson SM, Morlock EV, Satyshur KA, Czajkowski C. Structural requirements for eszopiclone and zolpidem binding to the gamma-aminobutyric acid type-A (GABAA) receptor are different. J Med Chem 2009; 51:7243-52. [PMID: 18973287 DOI: 10.1021/jm800889m] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The sleep-aids zolpidem and eszopiclone exert their effects by binding to and modulating gamma-aminobutyric acid type-A receptors (GABA(A)Rs), but little is known about the structural requirements for their actions. We made 24 cysteine mutations in the benzodiazepine (BZD) binding site of alpha(1)beta(2)gamma(2) GABA(A)Rs and measured zolpidem, eszopiclone, and BZD-site antagonist binding. Mutations in gamma(2)loop D and alpha(1)loops A and B altered the affinity of all ligands tested, indicating that these loops are important for BZD pocket structural integrity. In contrast, gamma(2)loop E and alpha(1)loop C mutations differentially affected ligand affinity, suggesting that these loops are important for ligand selectivity. In agreement with our mutagenesis data, eszopiclone docking yielded a single model stabilized by several hydrogen bonds. Zolpidem docking yielded three equally populated orientations with few polar interactions, suggesting that unlike eszopiclone, zolpidem relies more on shape recognition of the binding pocket than on specific residue interactions and may explain why zolpidem is highly alpha(1)- and gamma(2)-subunit selective.
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Affiliation(s)
- Susan M Hanson
- Department of Physiology and Program in Molecular and Cellular Pharmacology, University of Wisconsin Madison, Madison, Wisconsin 53711, USA
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35
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Nehrenberg DL, Rodriguiz RM, Cyr M, Zhang X, Lauder JM, Gariépy JL, Wetsel WC. An anxiety-like phenotype in mice selectively bred for aggression. Behav Brain Res 2009; 201:179-91. [PMID: 19428632 DOI: 10.1016/j.bbr.2009.02.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Revised: 01/12/2009] [Accepted: 02/10/2009] [Indexed: 10/21/2022]
Abstract
Using selective bi-directional breeding procedures, two different lines of mice were developed. The NC900 line is highly reactive and attacks their social partners without provocation, whereas aggression in NC100 animals is uncommon in social environments. The enhanced reactivity of NC900 mice suggests that emotionality may have been selected with aggression. As certain forms of anxiety promote exaggerated defensive responses, we tested NC900 mice for the presence of an anxiety-like phenotype. In the open field, light-dark exploration, and zero maze tests, NC900 mice displayed anxiety-like responses. These animals were less responsive to the anxiolytic actions of diazepam in the zero maze than NC100 animals; diazepam also reduced the reactivity and attack behaviors of NC900 mice. The NC900 mice had reduced diazepam-sensitive GABA(A) receptor binding in brain regions associated with aggression and anxiety. Importantly, there was a selective reduction in levels of the GABA(A) receptor alpha(2) subunit protein in NC900 frontal cortex and amygdala; no changes in alpha(1) or gamma(2) subunit proteins were observed. These findings suggest that reductions in the alpha(2) subunit protein in selected brain regions may underlie the anxiety and aggressive phenotype of NC900 mice. Since anxiety and aggression are comorbid in certain psychiatric conditions, such as borderline personality and posttraumatic stress disorder, investigations with NC900 mice may provide new insights into basic mechanisms that underlie these and related psychiatric conditions.
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Affiliation(s)
- Derrick L Nehrenberg
- Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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36
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Treweek JB, Sun C, Mayorov AV, Qi L, Levy CL, Roberts AJ, Dickerson TJ, Janda KD. Prevention of drug-induced memory impairment by immunopharmacotherapy. J Med Chem 2008; 51:6866-75. [PMID: 18921991 DOI: 10.1021/jm800506v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One approach to treating drug abuse uses antidrug antibodies to immunize subjects against the illicit substance rather than administering therapeutics that target the specific CNS site of action. At present, passive vaccination has recognized efficacy in treating certain gross symptoms of drug misuse, namely, motor activation, self-administration, and overdose. However, the potential for antibodies to prevent drug-induced changes involving finer cognitive processes, such as benzodiazepine-associated amnesia, remains unexplored. To address this concept, a flunitrazepam hapten was synthesized and employed in the generation of a panel of high affinity monoclonal antibodies. Anti-flunitrazepam mAb RCA3A3 ( K d,app = 200 nM) was tested in a mouse model of passive immunization and subsequent mole-equivalent challenge with flunitrazepam. Not only was flunitrazepam-induced sedation prevented but immunization also conferred protection to memory consolidation as assessed through contextual and cued fear conditioning paradigms. These results provide evidence that immunopharmacotherapeutic blockade of drug intoxication also preserves complex cognitive function.
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Affiliation(s)
- Jennifer B Treweek
- Department of Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
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37
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Baur R, Tan KR, Lüscher BP, Gonthier A, Goeldner M, Sigel E. Covalent modification of GABAA receptor isoforms by a diazepam analogue provides evidence for a novel benzodiazepine binding site that prevents modulation by these drugs. J Neurochem 2008; 106:2353-63. [PMID: 18643789 DOI: 10.1111/j.1471-4159.2008.05574.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Classical benzodiazepines, for example diazepam, interact with alpha(x)beta(2)gamma(2) GABA(A) receptors, x = 1, 2, 3, 5. Little is known about effects of alpha subunits on the structure of the binding pocket. We studied here the interaction of the covalently reacting diazepam analog 7-Isothiocyanato-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one (NCS compound) with alpha(1)H101Cbeta(2)gamma(2) and with receptors containing the homologous mutation, alpha(2)H101Cbeta(2)gamma(2), alpha(3)H126Cbeta(2)gamma(2) and alpha(5)H105Cbeta(2)gamma(2). This comparison was extended to alpha(6)R100Cbeta(2)gamma(2) receptors as this mutation conveys to these receptors high affinity towards classical benzodiazepines. The interaction was studied at the ligand binding level and at the functional level using electrophysiological techniques. Results indicate that the geometry of alpha(6)R100Cbeta(2)gamma(2) enables best interaction with NCS compound, followed by alpha(3)H126Cbeta(2)gamma(2), alpha(1)H101Cbeta(2)gamma(2) and alpha(2)H101Cbeta(2)gamma(2), while alpha(5)H105Cbeta(2)gamma(2) receptors show little interaction. Our results allow conclusions about the relative apposition of alpha(1)H101 and homologous positions in alpha(2), alpha(3), alpha(5) and alpha(6) with the position occupied by -Cl in diazepam. During this study we found evidence for the presence of a novel site for benzodiazepines that prevents modulation of GABA(A) receptors via the classical benzodiazepine site. The novel site potentially contributes to the high degree of safety to some of these drugs. Our results indicate that this site may be located at the alpha/beta subunit interface pseudo-symmetrically to the site for classical benzodiazepines located at the alpha/gamma interface.
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Affiliation(s)
- Roland Baur
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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38
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Ci S, Ren T, Su Z. Investigating the putative binding-mode of GABA and diazepam within GABA A receptor using molecular modeling. Protein J 2008; 27:71-8. [PMID: 17805947 DOI: 10.1007/s10930-007-9109-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The three-dimensional structure of the GABA A receptor that included the ligand/agonist binding site was constructed and validated by using molecular modeling technology. Moreover, the putative binding-mode of GABA and diazepam with GABAA receptor were investigated by means of docking studies. Based on an rmsd-tolerance of 1.0 angstroms, the docking of GABA to alpha1/beta2 interface resulted in three multi-member conformational clusters and model 2 was supported by homologous sequence alignment data and experimental evidence. On the other hand, the docking of diazepam to alpha1/gamma2 interface revealed five multi-member conformational clusters in the binding site and model 1 seemed to represent the correct orientation of diazepam in the binding site.
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Affiliation(s)
- Suqin Ci
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, P.R. China
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39
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Vijayan RSK, Ghoshal N. Structural basis for ligand recognition at the benzodiazepine binding site of GABAA alpha 3 receptor, and pharmacophore-based virtual screening approach. J Mol Graph Model 2008; 27:286-98. [PMID: 18565775 DOI: 10.1016/j.jmgm.2008.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 04/29/2008] [Accepted: 05/05/2008] [Indexed: 11/16/2022]
Abstract
Given the heterogeneity of GABA(A) receptor, the pharmacological significance of identifying subtype selective modulators is increasingly being recognized. Thus, drugs selective for GABA(A) alpha(3) receptors are expected to display fewer side effects than the drugs presently in clinical use. Hence we carried out 3D QSAR (three-dimensional quantitative structure-activity relationship) studies on a series of novel GABA(A) alpha(3) subtype selective modulators to gain more insight into subtype affinity. To identify the 3D functional attributes required for subtype selectivity, a chemical feature-based pharmacophore, primarily based on selective ligands representing diverse structural classes was generated. The obtained pseudo receptor model of the benzodiazepine binding site revealed a binding mode akin to "Message-Address" concept. Scaffold hopping was carried out across multi-conformational May Bridge database for the identification of novel chemotypes. Further a focused data reduction approach was employed to choose a subset of enriched compounds based on "Drug likeness" and "Similarity-based" methods. These results taken together could provide impetus for rational design and optimization of more selective and high affinity leads with a potential to have decreased adverse effects.
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Affiliation(s)
- R S K Vijayan
- Structural Biology and Bioinformatics Division, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India
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40
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Baur R, Sigel E. Replacement of histidine in position 105 in the α5subunit by cysteine stimulates zolpidem sensitivity of α5β2γ2GABAAreceptors. J Neurochem 2007; 103:2556-64. [DOI: 10.1111/j.1471-4159.2007.04982.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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41
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Tan KR, Baur R, Gonthier A, Goeldner M, Sigel E. Two neighboring residues of loop A of the alpha1 subunit point towards the benzodiazepine binding site of GABAA receptors. FEBS Lett 2007; 581:4718-22. [PMID: 17854801 DOI: 10.1016/j.febslet.2007.08.068] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 08/13/2007] [Accepted: 08/29/2007] [Indexed: 11/20/2022]
Abstract
Benzodiazepines are widely used drugs exerting sedative, anxiolytic, muscle relaxant, and anticonvulsant effects by acting through specific high affinity binding sites on some GABA(A) receptors. It is important to understand how these ligands are positioned in this binding site. We are especially interested here in the conformation of loop A of the alpha(1)beta(2)gamma(2) GABA(A) receptor containing a key residue for the interaction of benzodiazepines: alpha(1)H101. We describe a direct interaction of alpha(1)N102 with a diazepam- and an imidazobenzodiazepine-derivative. Our observations help to better understand the conformation of this region of the benzodiazepine pocket in GABA(A) receptor.
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Affiliation(s)
- Kelly R Tan
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
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Tan KR, Gonthier A, Baur R, Ernst M, Goeldner M, Sigel E. Proximity-accelerated Chemical Coupling Reaction in the Benzodiazepine-binding Site of γ-Aminobutyric Acid Type A Receptors. J Biol Chem 2007; 282:26316-25. [PMID: 17626010 DOI: 10.1074/jbc.m702153200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Benzodiazepines are widely used drugs. They exert sedative/hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects and act through a specific high affinity binding site on the major inhibitory neurotransmitter receptor, the gamma-aminobutyric acid type A (GABA(A)) receptor. Ligands of the benzodiazepine-binding site are classified into three groups depending on their mode of action: positive and negative allosteric modulators and antagonists. To rationally design ligands of the benzodiazepine site in different isoforms of the GABA(A) receptor, we need to understand the relative positioning and overlap of modulators of different allosteric properties. To solve these questions, we used a proximity-accelerated irreversible chemical coupling reaction. GABA(A) receptor residues thought to reside in the benzodiazepine-binding site were individually mutated to cysteine and combined with a cysteine-reactive benzodiazepine site ligand. Direct apposition of reaction partners is expected to lead to a covalent reaction. We describe here such a reaction of predominantly alpha(1)H101C and also three other mutants (alpha(1)G157C, alpha(1)V202C, and alpha(1)V211C) with an Imid-NCS derivative in which a reactive isothiocyanate group (-NCS) replaces the azide group (-N(3)) in the partial negative allosteric modulator Ro15-4513. Our results show four contact points of imidazobenzodiazepines with the receptor, alpha(1)H101C being shared by classical benzodiazepines. Taken together with previous data, a similar orientation of these ligands within the benzodiazepine-binding pocket may be proposed.
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Affiliation(s)
- Kelly R Tan
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, Bern CH-3012, Switzerland
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Ci SQ, Ren TR, Ma CX, Su ZG. Modeling of αk/γ2 (k=1, 2, 3 and 5) interface of GABAA receptor and docking studies with zolpidem: Implications for selectivity. J Mol Graph Model 2007; 26:537-45. [PMID: 17451983 DOI: 10.1016/j.jmgm.2007.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Revised: 03/18/2007] [Accepted: 03/18/2007] [Indexed: 11/28/2022]
Abstract
The three-dimensional models of the alphak/gamma2 (k=1, 2, 3 and 5) interface of GABA(A) receptors, which included the agonist-binding site, were constructed and validated by molecular modeling technology. To investigate the mechanism of alpha subunit selectivity of zolpidem, docking calculations were used to illustrate the potential binding modes of zolpidem with different alpha subtypes. The results revealed that there were three reasons resulting in the distinct binding affinity of zolpidem to different alpha subtype. Firstly, the number of hydrogen bonds of agonist-receptor complex would determine the magnitude of binding affinity. Secondly, the His residue in loop A of alpha subunit was indicated as a key role of benzodiazepine binding. Thirdly, the side chain of Glu in loop C reduced the affinity of zolpidem to those receptors containing alpha2, alpha3 or alpha5 subunits.
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Affiliation(s)
- Su-Qin Ci
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, China
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44
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Mokrab Y, Bavro VN, Mizuguchi K, Todorov NP, Martin IL, Dunn SMJ, Chan SL, Chau PL. Exploring ligand recognition and ion flow in comparative models of the human GABA type A receptor. J Mol Graph Model 2007; 26:760-74. [PMID: 17544304 DOI: 10.1016/j.jmgm.2007.04.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 04/29/2007] [Indexed: 11/25/2022]
Abstract
We present two comparative models of the GABA(A) receptor. Model 1 is based on the 4-A resolution structure of the nicotinic acetylcholine receptor from Torpedo marmorata and represents the unliganded receptor. Two agonists, GABA and muscimol, two benzodiazepines, flunitrazepam and alprazolam, together with the general anaesthetic halothane, have been docked to this model. The ion flow is also explored in model 1 by evaluating the interaction energy of a chloride ion as it traverses the extracellular, transmembrane and intracellular domains of the protein. Model 2 differs from model 1 only in the extracellular domain and represents the liganded receptor. Comparison between the two models not only allows us to explore commonalities and differences with comparative models of the nicotinic acetylcholine receptor, but also suggests possible protein sub-domain interactions with the GABA(A) receptor not previously addressed.
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Affiliation(s)
- Younes Mokrab
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom
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Olsen RW, Hanchar HJ, Meera P, Wallner M. GABAA receptor subtypes: the "one glass of wine" receptors. Alcohol 2007; 41:201-9. [PMID: 17591543 PMCID: PMC2852584 DOI: 10.1016/j.alcohol.2007.04.006] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 04/13/2007] [Accepted: 04/16/2007] [Indexed: 11/28/2022]
Abstract
This review discusses evidence for and apparent controversy about, gamma-aminobutyric acid type A (GABAA) receptor (GABAAR) subtypes that mediate alcohol effects experienced during social drinking. GABAARs that contain the beta3 and delta subunits were shown to be enhanced by alcohol concentrations that mirror the concentration dependence of alcohol responses in humans. A mutation (alpha6R100Q) previously found in alcohol nontolerant rats in the cerebellar GABAAR alpha6 subunit is sufficient for increased alcohol-induced ataxia in rats homozygous for this mutation (alpha6-100QQ) and further increases alcohol sensitivity of tonic GABA currents (mediated by alpha6betadelta receptors) in cerebellar granule cells of alpha6-100QQ rats and in recombinant alpha6R100Qbeta3delta receptors. This provided the first direct evidence that these types of receptors mediate behavioral effects of ethanol. Furthermore, the behavioral alcohol antagonist Ro15-4513 specifically reverses ethanol enhancement on alpha4/6beta3delta receptors. Unexpectedly, native and recombinant alpha4/6beta3delta receptors bind the behavioral alcohol antagonist Ro15-4513 with high affinity and this binding is competitive with EtOH, suggesting a specific and mutually exclusive (competitive) ethanol/Ro15-4513 site, which explains the puzzling activity of Ro15-4513 as a behavioral alcohol antagonist. Our conclusion from these findings is that alcohol/Ro15-4513-sensitive GABAAR subtypes are important alcohol targets and that alcohol at relevant concentrations is more specific than previously thought. In this review, we discuss technical difficulties in expressing recombinant delta subunit-containing receptors in oocytes and mammalian cells that may have contributed to negative results and confusion. Not only because we have reproduced detailed positive results numerous times, and we and many others have built extensively on basic findings, but also because we explain and combine many previously puzzling results into a coherent and highly plausible paradigm on how alcohol exerts an important part of its action in the brain, we are confident about our findings and conclusions. However, many important open questions remain to be answered.
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Affiliation(s)
- Richard W. Olsen
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095
- To whom correspondence should be addressed at: Department of Molecular and Medical Pharmacology, Geffen School of Medicine at the University of California Los Angeles, Room 23-120 CHS, Charles Young Drive South, Los Angeles, CA 90095-1735, ;
| | - Harry J. Hanchar
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095
| | - Pratap Meera
- Department of Neurobiology; University of California, Los Angeles, CA 90095
| | - Martin Wallner
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA 90095
- To whom correspondence should be addressed at: Department of Molecular and Medical Pharmacology, Geffen School of Medicine at the University of California Los Angeles, Room 23-120 CHS, Charles Young Drive South, Los Angeles, CA 90095-1735, ;
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Stilwell GE, Saraswati S, Littleton JT, Chouinard SW. Development of aDrosophilaseizure model forin vivohigh-throughput drug screening. Eur J Neurosci 2006; 24:2211-22. [PMID: 17074045 DOI: 10.1111/j.1460-9568.2006.05075.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An important application of model organisms in neurological research has been to identify and characterise therapeutic approaches for epilepsy, a recurrent seizure disorder that affects > 1% of the human population. Proconvulsant-treated rodent models have been widely used for antiepileptic drug discovery and development, but are not suitable for high-throughput screening. To generate a genetically tractable model that would be suitable for large-scale, high-throughput screening for antiepileptic drug candidates, we characterized a Drosophila chemical treatment model using the GABA(A) receptor antagonist picrotoxin. This proconvulsant, delivered to Drosophila larvae via simple feeding methods suitable for automated screening, generated robust generalised seizures with lethality occurring at doses between 0.3 and 0.5 mg/mL. Electrophysiological analysis of CNS motor neuron output in picrotoxin-treated larvae revealed generalised seizures within minutes of drug exposure. At subthreshold doses for seizure induction, picrotoxin produced an increased frequency of motor neuron action potential bursting, indicating that CNS GABAergic transmission regulates patterned activity. Mutants in the Drosophila Rdl GABA(A) receptor are resistant to picrotoxin, confirming that seizure induction occurs via a conserved GABA(A) receptor pathway. To validate the usefulness of this model for in vivo drug screening, we identified several classes of neuroactive antiepileptic compounds in a pilot screen, including phenytoin and nifedipine, which can rescue the seizures and lethal neurotoxicity induced by picrotoxin. The well-defined actions of picrotoxin in Drosophila and the ease with which compounds can be assayed for antiseizure activity makes this genetically tractable model attractive for high-throughput in vivo screens to identify novel anticonvulsants and seizure susceptibility loci.
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Wallner M, Hanchar HJ, Olsen RW. Low dose acute alcohol effects on GABA A receptor subtypes. Pharmacol Ther 2006; 112:513-28. [PMID: 16814864 PMCID: PMC2847605 DOI: 10.1016/j.pharmthera.2006.05.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 05/15/2006] [Indexed: 12/23/2022]
Abstract
GABA(A) receptors (GABA(A)Rs) are the main inhibitory neurotransmitter receptors and have long been implicated in mediating at least part of the acute actions of ethanol. For example, ethanol and GABAergic drugs including barbiturates and benzodiazepines share many pharmacological properties. Besides the prototypical synaptic GABA(A)R subtypes, nonsynaptic GABA(A)Rs have recently emerged as important regulators of neuronal excitability. While high doses (> or =100 mM) of ethanol have been reported to enhance activity of most GABA(A)R subtypes, most abundant synaptic GABA(A)Rs are essentially insensitive to ethanol concentrations that occur during social ethanol consumption (< 30 mM). However, extrasynaptic delta and beta3 subunit-containing GABA(A)Rs, associated in the brain with alpha4 or alpha6 subunits, are sensitive to low millimolar ethanol concentrations, as produced by drinking half a glass of wine. Additionally, we found that a mutation in the cerebellar alpha6 subunit (alpha6R100Q), initially reported in rats selectively bred for increased alcohol sensitivity, is sufficient to produce increased alcohol-induced motor impairment and further increases of alcohol sensitivity in recombinant alpha6beta3delta receptors. Furthermore, the behavioral alcohol antagonist Ro15-4513 blocks the low dose alcohol enhancement on alpha4/6/beta3delta receptors, without reducing GABA-induced currents. In binding assays alpha4beta3delta GABA(A)Rs bind [(3)H]Ro15-4513 with high affinity, and this binding is inhibited, in an apparently competitive fashion, by low ethanol concentrations, as well as analogs of Ro15-4513 that are active to antagonize ethanol or Ro15-4513's block of ethanol. We conclude that most low to moderate dose alcohol effects are mediated by alcohol actions on alcohol/Ro15-4513 binding sites on GABA(A)R subtypes.
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Affiliation(s)
| | | | - Richard W. Olsen
- Corresponding author. Tel.: +1 310 825 5093; fax: +1 310 267 2003. (R.W. Olsen)
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Sakiyama Y, Saito M, Inoue O. Acute treatment with pentobarbital alters the kinetics of in vivo receptor binding in the mouse brain. Nucl Med Biol 2006; 33:535-41. [PMID: 16720246 DOI: 10.1016/j.nucmedbio.2006.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 02/03/2006] [Accepted: 02/08/2006] [Indexed: 11/15/2022]
Abstract
The effect of pentobarbital, a sedative-hypnotic barbiturate, on the in vivo binding of benzodiazepine receptors in the mouse brain was investigated. Dose-related changes in the apparent binding of [3H]Ro15-1788 ([3H]flumazenil) in the cerebral cortex, cerebellum and pons-medulla were observed by pretreatment with pentobarbital. For quantification of the kinetic properties of the in vivo binding of [3H]Ro15-1788, time courses of radioactivity following its injection were examined, and kinetic analysis was performed using the compartment model. The time courses of radioactivity following injection of [3H]Ro15-1788 with 3 mg/kg Ro15-1788 were used as input function. In all regions studied, rate constants between input compartment and specific binding compartment were significantly decreased by pentobarbital. However, no significant alterations in the binding potential (BP=K3/K4) of benzodiazepine receptors by pentobarbital were observed in any of the regions. A saturation experiment indicated that the decrease in the input rate constant (K3), which includes both the association rate constant (k(on)) and the number of binding sites available (B(max)), was mainly due to decrease in k(on). These results suggest that apparent increases in binding at 20 min after tracer injection were due to the decrease in the association and dissociation rates of binding in vivo.
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Affiliation(s)
- Yojiro Sakiyama
- Division of Clinical Research, National Institute of Radiological Sciences, Inage-ku, Chibashi 263-8555, Japan.
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Hanchar HJ, Chutsrinopkun P, Meera P, Supavilai P, Sieghart W, Wallner M, Olsen RW. Ethanol potently and competitively inhibits binding of the alcohol antagonist Ro15-4513 to alpha4/6beta3delta GABAA receptors. Proc Natl Acad Sci U S A 2006; 103:8546-51. [PMID: 16581914 PMCID: PMC1482528 DOI: 10.1073/pnas.0509903103] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although GABA(A) receptors have long been implicated in mediating ethanol (EtOH) actions, receptors containing the "nonsynaptic" delta subunit only recently have been shown to be uniquely sensitive to EtOH. Here, we show that delta subunit-containing receptors bind the imidazo-benzodiazepines (BZs) flumazenil and Ro15-4513 with high affinity (K(d) < 10 nM), contrary to the widely held belief that these receptors are insensitive to BZs. In immunopurified native cerebellar and recombinant delta subunit-containing receptors, binding of the alcohol antagonist [(3)H]Ro15-4513 is inhibited by low concentrations of EtOH (K(i) approximately 8 mM). Also, Ro15-4513 binding is inhibited by BZ-site ligands that have been shown to reverse the behavioral alcohol antagonism of Ro15-4513 (i.e., flumazenil, beta-carbolinecarboxylate ethyl ester (beta-CCE), and N-methyl-beta-carboline-3-carboxamide (FG7142), but not including any classical BZ agonists like diazepam). Experiments that were designed to distinguish between a competitive and allosteric mechanism suggest that EtOH and Ro15-4513 occupy a mutually exclusive binding site. The fact that only Ro15-4513, but not flumazenil, can inhibit the EtOH effect, and that Ro15-4513 differs from flumazenil by only a single group in the molecule (an azido group at the C7 position of the BZ ring) suggest that this azido group in Ro15-4513 might be the area that overlaps with the alcohol-binding site. Our findings, combined with previous observations that Ro15-4513 is a behavioral alcohol antagonist, suggest that many of the behavioral effects of EtOH at relevant physiological concentrations are mediated by EtOH/Ro15-4513-sensitive GABA(A) receptors.
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Affiliation(s)
| | - Panida Chutsrinopkun
- Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok 10 400, Thailand; and
| | - Pratap Meera
- Neurobiology, University of California, Los Angeles, CA 90095
| | - Porntip Supavilai
- Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok 10 400, Thailand; and
| | - Werner Sieghart
- Center for Brain Research, Division of Biochemistry and Molecular Biology and Section of Biochemical Psychiatry, Medical University of Vienna, A-1090 Vienna, Austria
| | - Martin Wallner
- Departments of *Molecular and Medical Pharmacology and
- To whom correspondence may be addressed at:
Department of Molecular and Medical Pharmacology, University of California, Room 23-120 CHS, Charles Young Drive South, Los Angeles, CA 90095-1735. E-mail:
or
| | - Richard W. Olsen
- Departments of *Molecular and Medical Pharmacology and
- To whom correspondence may be addressed at:
Department of Molecular and Medical Pharmacology, University of California, Room 23-120 CHS, Charles Young Drive South, Los Angeles, CA 90095-1735. E-mail:
or
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50
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Thompson AJ, Chau PL, Chan SL, Lummis SCR. Unbinding pathways of an agonist and an antagonist from the 5-HT3 receptor. Biophys J 2006; 90:1979-91. [PMID: 16387779 PMCID: PMC1386777 DOI: 10.1529/biophysj.105.069385] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2005] [Accepted: 11/09/2005] [Indexed: 11/18/2022] Open
Abstract
The binding sites of 5-HT3 and other Cys-loop receptors have been extensively studied, but there are no data on the entry and exit routes of ligands for these sites. Here we have used molecular dynamics simulations to predict the pathway for agonists and antagonists exiting from the 5-HT3 receptor binding site. The data suggest that the unbinding pathway follows a tunnel at the interface of two subunits, which is approximately 8 A long and terminates approximately 20 A above the membrane. The exit routes for an agonist (5-HT) and an antagonist (granisetron) were similar, with trajectories toward the membrane and outward from the ligand binding site. 5-HT appears to form many hydrogen bonds with residues in the unbinding pathway, and experiments show that mutating these residues significantly affects function. The location of the pathway is also supported by docking studies of granisetron, which show a potential binding site for granisetron on the unbinding route. We propose that leaving the binding pocket along this tunnel places the ligands close to the membrane and prevents their immediate reentry into the binding pocket. We anticipate similar exit pathways for other members of the Cys-loop receptor family.
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Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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