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Wang S, Liu H, Lei K, Li G, Li J, Wei Y, Wang X, Liu R. Synthesis of 3,4-dihydroquinolin-2(1H)-one derivatives with anticonvulsant activity and their binding to the GABA A receptor. Bioorg Chem 2020; 103:104182. [PMID: 32890992 DOI: 10.1016/j.bioorg.2020.104182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/21/2020] [Accepted: 08/03/2020] [Indexed: 11/29/2022]
Abstract
In this study, a series of 3,4-dihydroquinolin-2(1H)-one derivatives were designed and synthesized using two experimental models, namely maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ), to test the anticonvulsant activity of the target compound in vivo (i.p. in Kunming mice). The neurotoxicity (NT) of the target compound was measured by the rotating rod method (i.p. in Kunming mice). Six compounds with potential activity were selected from the two experimental models to test the 50% effective dose (ED50). In vitro binding experiments with the GABAA receptor were also performed. The results of the pharmacological experiments showed that compound 7-((5-(pentylthio)-1,3,4-oxadiazol-2-yl)methoxy)-3,4-dihydroquinolin-2(1H)-one (5b) showed the best anticonvulsant activity (MES, ED50 = 10.1 mg/kg; scPTZ, ED50 = 9.3 mg/kg), which was superior to activities shown by carbamazepine and ethosuximide, and it also exhibited the most potent binding affinity to GABAA receptors (IC50 = 0.12 μM). The GABA content in Wistar rat brains (i.p.) was also investigated, and the results showed that compound 5b may have a certain effect on the GABA system, as it increased the GABA concentration in the brain of rats. Molecular docking was used to study the binding mode of compound 5b and the GABAA receptor. Compound 5b showed significant interactions with residues at the benzodiazepines binding site on the GABAA receptor. The physicochemical and pharmacokinetic properties of the target compounds were predicted using Discovery Studio 2019 and ChemBioDraw Ultra 14.0.
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Affiliation(s)
- Shiben Wang
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China.
| | - Hui Liu
- College of Life Sciences, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Kang Lei
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Guangyong Li
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Jun Li
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Yuyu Wei
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Xuekun Wang
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
| | - Renmin Liu
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong 252059, China
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Wang S, Liu H, Wang X, Lei K, Li G, Li J, Liu R, Quan Z. Synthesis of 1,3,4-oxadiazole derivatives with anticonvulsant activity and their binding to the GABA A receptor. Eur J Med Chem 2020; 206:112672. [PMID: 32798790 DOI: 10.1016/j.ejmech.2020.112672] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/16/2020] [Accepted: 07/16/2020] [Indexed: 02/03/2023]
Abstract
In this study, a series of 1,3,4-oxadiazole derivatives (5a-s, 10a-s, and 16a-d) were designed and synthesized using maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) models, to test the anticonvulsant activity of the target compounds in vivo. The neurotoxicity (NT) of the target compounds was measured using the rotating rod (ROT) method. Seven compounds with potential activity were selected to test the 50% effective dose (ED50) and 50% toxic dose (TD50). Pharmacological experiments revealed that 6-((5-(pentylthio)-1,3,4-oxadiazol-2-yl)methoxy)-3,4-dihydroquinolin-2(1H)-one (5b) showed the best anticonvulsant activity (MES, ED50 = 8.9 mg/kg; scPTZ, ED50 = 10.2 mg/kg), which was greater than the activities of carbamazepine and ethosuximide. Compound 5b exhibited the most potent binding affinity toward the GABAA receptor (IC50 = 0.11 μM) in the in vitro binding experiments. Compound 5b displayed significant anxiolytic activity at a low dose (1 mg/kg) in the elevated plus maze (EPM) test. The GABA content in rat brains was also investigated, and the results showed that compound 5b might have affected the GABA system. In our molecular docking experiment, compound 5b showed significant interactions with residues present at the benzodiazepine binding site on the GABAA receptor. The structure and physicochemical and pharmacokinetic properties of the target compound were predicted using Discovery Studio 2019 and ChemBioDraw Ultra 14.0. Finally we demonstrated that compound 5b mainly acted on GABAA receptor. Thus the present study has provided potential candidates for further investigation in epilepsy.
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Affiliation(s)
- Shiben Wang
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China.
| | - Hui Liu
- College of Life Sciences, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Xuekun Wang
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Kang Lei
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Guangyong Li
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Jun Li
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Renmin Liu
- College of Pharmacy, Liaocheng University, Liaocheng, Shandong, 252059, China
| | - Zheshan Quan
- College of Pharmacy, Yanbian University, Yanji, Jilin, 133002, China
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Sahu M, Siddiqui N, Sharma V, Wakode S. 5,6-Dihydropyrimidine-1(2H)-carbothioamides: Synthesis, in vitro GABA-AT screening, anticonvulsant activity and molecular modelling study. Bioorg Chem 2018; 77:56-67. [PMID: 29331765 DOI: 10.1016/j.bioorg.2017.12.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 12/26/2017] [Accepted: 12/30/2017] [Indexed: 12/12/2022]
Abstract
Even after considerable advances in the field of epilepsy treatment, convulsions are inefficiently controlled by standard drug therapy. Herein, a series of pyrimidine-carbothioamide derivatives 4(a-t) was designed as anticonvulsant agents by doing some important structural modifications in well-known anticonvulsant drugs. Two classical animal models were used for the in vivo anticonvulsant screening, maximum electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ) models; followed by motor impairment study by rotarod method. The most active compound 4g effectively suppressed seizure effect in both the animal models with median doses of 15.6 mg/kg (MES ED50), 278.4 mg/kg (scPTZ ED50) and 534.4 mg/kg (TD50) with no sign of neurotoxicity. Furthermore, in vitro GABA-AT enzyme activity assay of 4g showed inhibitory potency (IC50) of 12.23 μM. The docking study also favored the animal studies.
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Affiliation(s)
- Meeta Sahu
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Education & Research (Formerly, Faculty of Pharmacy), Jamia Hamdard, New Delhi 110062, India
| | - Nadeem Siddiqui
- Department of Pharmaceutical Chemistry, School of Pharmaceutical Education & Research (Formerly, Faculty of Pharmacy), Jamia Hamdard, New Delhi 110062, India.
| | - Vidushi Sharma
- Department of Pharmaceutical Chemistry, Delhi Institute of Pharmaceutical Sciences and Research (DIPSAR), Mehrauli-Badarpur Road, Pushp Vihar, Sector-3, New Delhi 110017, India
| | - Sharad Wakode
- Department of Pharmaceutical Chemistry, Delhi Institute of Pharmaceutical Sciences and Research (DIPSAR), Mehrauli-Badarpur Road, Pushp Vihar, Sector-3, New Delhi 110017, India
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Yashin NV, Averina EB, Vasilenko DA, Grishin YK, Osolodkin DI, Palyulin VA, Kuznetsova TS, Zefirov NS. Synthesis of novel non-natural spiro[2.3]hexane amino acids, the conformationally restricted analogs of γ-aminobutyric acid. Russ Chem Bull 2017. [DOI: 10.1007/s11172-017-1912-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Naffaa MM, Hung S, Chebib M, Johnston GAR, Hanrahan JR. GABA-ρ receptors: distinctive functions and molecular pharmacology. Br J Pharmacol 2017; 174:1881-1894. [PMID: 28258627 DOI: 10.1111/bph.13768] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/26/2017] [Accepted: 03/01/2017] [Indexed: 01/14/2023] Open
Abstract
The homomeric GABA-ρ ligand-gated ion channels (also known as GABAC or GABAA -ρ receptors) are similar to heteromeric GABAA receptors in structure, function and mechanism of action. However, their distinctive pharmacological properties and distribution make them of special interest. This review focuses on GABA-ρ ion channel structure, ligand selectivity toward ρ receptors over heteromeric GABAA receptor sub-types and selectivity between different homomeric ρ sub-type receptors. Several GABA analogues show selectivity at homomeric GABA-ρ receptors over heteromeric GABAA receptors. More recently, some synthetic ligands have been found to show selectivity at receptors formed from one ρ subtype over others. The unique pharmacological profiles of these agents are discussed in this review. The classical binding site of GABA within the orthosteric site of GABA-ρ homomeric receptors is discussed in detail regarding the loops and residues that constitute the binding site. The ligand-residue interactions in this classical binding and those of mutant receptors are discussed. The structure and conformations of GABA are discussed in regard to its flexibility and molecular properties. Although the binding mode of GABA is difficult to predict, several interactions between GABA and the receptor assist in predicting its potential conformation and mode of action. The structure-activity relationships of GABA and structurally key ligands at ρ receptors are described and discussed.
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Affiliation(s)
- Moawiah M Naffaa
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Sandy Hung
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | | | - Jane R Hanrahan
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
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Druzhilovskiy DS, Rudik AV, Filimonov DA, Lagunin AA, Gloriozova TA, Poroikov VV. Online resources for the prediction of biological activity of organic compounds. Russ Chem Bull 2016. [DOI: 10.1007/s11172-016-1310-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Naffaa MM, Chebib M, Hibbs DE, Hanrahan JR. Comparison of templates for homology model of ρ1 GABA C receptors: More insights to the orthosteric binding site’s structure and functionality. J Mol Graph Model 2015; 62:43-55. [DOI: 10.1016/j.jmgm.2015.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/27/2015] [Accepted: 09/01/2015] [Indexed: 11/25/2022]
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Synthesis, biological evaluation and molecular docking studies of thiazole-based pyrrolidinones and isoindolinediones as anticonvulsant agents. Med Chem Res 2015. [DOI: 10.1007/s00044-015-1371-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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9
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Lees K, Musgaard M, Suwanmanee S, Buckingham SD, Biggin P, Sattelle D. Actions of agonists, fipronil and ivermectin on the predominant in vivo splice and edit variant (RDLbd, I/V) of the Drosophila GABA receptor expressed in Xenopus laevis oocytes. PLoS One 2014; 9:e97468. [PMID: 24823815 PMCID: PMC4019635 DOI: 10.1371/journal.pone.0097468] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 04/20/2014] [Indexed: 11/18/2022] Open
Abstract
Ionotropic GABA receptors are the targets for several classes of insecticides. One of the most widely-studied insect GABA receptors is RDL (resistance to dieldrin), originally isolated from Drosophila melanogaster. RDL undergoes alternative splicing and RNA editing, which influence the potency of GABA. Most work has focussed on minority isoforms. Here, we report the first characterisation of the predominant native splice variant and RNA edit, combining functional characterisation with molecular modelling of the agonist-binding region. The relative order of agonist potency is GABA> muscimol> TACA> β-alanine. The I/V edit does not alter the potency of GABA compared to RDLbd. Docking calculations suggest that these agonists bind and activate RDLbdI/V through a similar binding mode. TACA and β-alanine are predicted to bind with lower affinity than GABA, potentially explaining their lower potency, whereas the lower potency of muscimol and isoguvacine cannot be explained structurally from the docking calculations. The A301S (resistance to dieldrin) mutation reduced the potency of antagonists picrotoxin, fipronil and pyrafluprole but the I/V edit had no measurable effect. Ivermectin suppressed responses to GABA of RDLbdI/V, RDLbd and RDLbdI/VA301S. The dieldrin resistant variant also showed reduced sensitivity to Ivermectin. This study of a highly abundant insect GABA receptor isoform will help the design of new insecticides.
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Affiliation(s)
- Kristin Lees
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Maria Musgaard
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Siros Suwanmanee
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Steven David Buckingham
- Wolfson Institute for Biomedical Research, Department of Medicine, University College London, London, United Kingdom
| | - Philip Biggin
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - David Sattelle
- Wolfson Institute for Biomedical Research, Department of Medicine, University College London, London, United Kingdom
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γ-Amino butyric acid analogs as novel potent GABA-AT inhibitors: molecular docking, synthesis, and biological evaluation. Med Chem Res 2012. [DOI: 10.1007/s00044-012-0023-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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11
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Docking-based virtual screening of Schiff’s bases of GABA: a prospective to novel GABA-AT inhibitors. Med Chem Res 2011. [DOI: 10.1007/s00044-011-9843-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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12
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Martínez-Delgado G, Estrada-Mondragón A, Miledi R, Martínez-Torres A. An Update on GABAρ Receptors. Curr Neuropharmacol 2011; 8:422-33. [PMID: 21629448 PMCID: PMC3080597 DOI: 10.2174/157015910793358141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 04/08/2010] [Accepted: 06/21/2010] [Indexed: 01/29/2023] Open
Abstract
The present review discusses the functional and molecular diversity of GABAρ receptors. These receptors were originally described in the mammalian retina, and their functional role in the visual pathway has been recently elucidated; however new studies on their distribution in the brain and spinal cord have revealed that they are more spread than originally thought, and thus it will be important to determine their physiological contribution to the GABAergic transmission in other areas of the central nervous system. In addition, molecular modeling has revealed peculiar traits of these receptors that have impacted on the interpretations of the latest pharmacolgical and biophysical findings. Finally, sequencing of several vertebrate genomes has permitted a comparative analysis of the organization of the GABAρ genes.
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Affiliation(s)
- Gustavo Martínez-Delgado
- Instituto de Neurbiología, Departamento de Neurobiología Celular y Molecular, Laboratorio D15, Campus UNAM Juriquilla. Querétaro 76230, México
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Gavande N, Yamamoto I, Salam NK, Ai TH, Burden PM, Johnston GAR, Hanrahan JR, Chebib M. Novel Cyclic Phosphinic Acids as GABAC ρ Receptor Antagonists: Design, Synthesis, and Pharmacology. ACS Med Chem Lett 2011; 2:11-6. [PMID: 24900248 DOI: 10.1021/ml1001344] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 10/13/2010] [Indexed: 11/28/2022] Open
Abstract
Understanding the role of GABAC receptors in the central nervous system is limited due to a lack of specific ligands. Novel γ-aminobutyric acid (GABA) analogues based on 3-(aminomethyl)-1-oxo-1-hydroxy-phospholane 17 and 3-(guanido)-1-oxo-1-hydroxy-phospholane 19 were investigated to obtain selective GABAC receptor antagonists. A compound of high potency (19, K B = 10 μM) and selectivity (greater than 100 times at ρ1 GABAC receptors as compared to α1β2γ2L GABAA and GABAB(1b,2) receptors) was obtained. The cyclic phosphinic acids (17 and 19) are novel lead agents for developing into more potent and selective GABAC receptor antagonists with increased lipophilicity for future in vivo studies.
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Affiliation(s)
- Navnath Gavande
- Faculty of Pharmacy, The University of Sydney, NSW, Australia
| | - Izumi Yamamoto
- Faculty of Pharmacy, The University of Sydney, NSW, Australia
| | - Noeris K. Salam
- Schrodinger, Inc., 8910 University Center Lane, Suite 270, San Diego, California, United States
| | - Tu-Hoa Ai
- Adrien Albert Laboratory, Department of Pharmacology, The University of Sydney, NSW, Australia
| | - Peter M. Burden
- Adrien Albert Laboratory, Department of Pharmacology, The University of Sydney, NSW, Australia
| | - Graham A. R. Johnston
- Adrien Albert Laboratory, Department of Pharmacology, The University of Sydney, NSW, Australia
| | | | - Mary Chebib
- Faculty of Pharmacy, The University of Sydney, NSW, Australia
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Mohan S, Sheena A, Poulose N, Anilkumar G. Molecular dynamics simulation studies of GLUT4: substrate-free and substrate-induced dynamics and ATP-mediated glucose transport inhibition. PLoS One 2010; 5:e14217. [PMID: 21151967 PMCID: PMC2997047 DOI: 10.1371/journal.pone.0014217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 11/15/2010] [Indexed: 02/03/2023] Open
Abstract
Background Glucose transporter 4 (GLUT4) is an insulin facilitated glucose transporter that plays an important role in maintaining blood glucose homeostasis. GLUT4 is sequestered into intracellular vesicles in unstimulated cells and translocated to the plasma membrane by various stimuli. Understanding the structural details of GLUT4 will provide insights into the mechanism of glucose transport and its regulation. To date, a crystal structure for GLUT4 is not available. However, earlier work from our laboratory proposed a well validated homology model for GLUT4 based on the experimental data available on GLUT1 and the crystal structure data obtained from the glycerol 3-phosphate transporter. Methodology/Principal Findings In the present study, the dynamic behavior of GLUT4 in a membrane environment was analyzed using three forms of GLUT4 (apo, substrate and ATP-substrate bound states). Apo form simulation analysis revealed an extracellular open conformation of GLUT4 in the membrane favoring easy exofacial binding of substrate. Simulation studies with the substrate bound form proposed a stable state of GLUT4 with glucose, which can be a substrate-occluded state of the transporter. Principal component analysis suggested a clockwise movement for the domains in the apo form, whereas ATP substrate-bound form induced an anti-clockwise rotation. Simulation studies suggested distinct conformational changes for the GLUT4 domains in the ATP substrate-bound form and favor a constricted behavior for the transport channel. Various inter-domain hydrogen bonds and switching of a salt-bridge network from E345-R350-E409 to E345-R169-E409 contributed to this ATP-mediated channel constriction favoring substrate occlusion and prevention of its release into cytoplasm. These data are consistent with the biochemical studies, suggesting an inhibitory role for ATP in GLUT-mediated glucose transport. Conclusions/Significance In the absence of a crystal structure for any glucose transporter, this study provides mechanistic details of the conformational changes in GLUT4 induced by substrate and its regulator.
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Affiliation(s)
- Suma Mohan
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Aswathy Sheena
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Ninu Poulose
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
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Johnston GAR, Chebib M, Hanrahan JR, Mewett KN. Neurochemicals for the investigation of GABA(C) receptors. Neurochem Res 2010; 35:1970-7. [PMID: 20963487 DOI: 10.1007/s11064-010-0271-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2010] [Indexed: 01/23/2023]
Abstract
GABA(C) receptors are being investigated for their role in many aspects of nervous system function including memory, myopia, pain and sleep. There is evidence for functional GABA(C) receptors in many tissues such as retina, hippocampus, spinal cord, superior colliculus, pituitary and the gut. This review describes a variety of neurochemicals that have been shown to be useful in distinguishing GABA(C) receptors from other receptors for the major inhibitory neurotransmitter GABA. Some selective agonists (including (+)-CAMP and 5-methyl-IAA), competitive antagonists (such as TPMPA, (±)-cis-3-ACPBPA and aza-THIP), positive (allopregnanolone) and negative modulators (epipregnanolone, loreclezole) are described. Neurochemicals that may assist in distinguishing between homomeric ρ1 and ρ2 GABA(C) receptors (2-methyl-TACA and cyclothiazide) are also covered. Given their less widespread distribution, lower abundance and relative structural simplicity compared to GABA(A) and GABA(B) receptors, GABA(C) receptors are attractive drug targets.
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Affiliation(s)
- Graham A R Johnston
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology D06, The University of Sydney, Sydney, NSW 2006, Australia.
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17
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Palyulin VA, Radchenko EV, Osolodkin DE, Chupakhin VI, Zefirov NS. Ionotropic GABA receptors: modelling and design of selective ligands. J Cheminform 2010. [PMCID: PMC2867184 DOI: 10.1186/1758-2946-2-s1-p49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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18
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Adamian L, Gussin HA, Tseng YY, Muni NJ, Feng F, Qian H, Pepperberg DR, Liang J. Structural model of rho1 GABAC receptor based on evolutionary analysis: Testing of predicted protein-protein interactions involved in receptor assembly and function. Protein Sci 2010; 18:2371-83. [PMID: 19768800 DOI: 10.1002/pro.247] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The homopentameric rho1 GABA(C) receptor is a ligand-gated ion channel with a binding pocket for gamma-aminobutyric acid (GABA) at the interfaces of N-terminal extracellular domains. We combined evolutionary analysis, structural modeling, and experimental testing to study determinants of GABA(C) receptor assembly and channel gating. We estimated the posterior probability of selection pressure at amino acid residue sites measured as omega-values and built a comparative structural model, which identified several polar residues under strong selection pressure at the subunit interfaces that may form intersubunit hydrogen bonds or salt bridges. At three selected sites (R111, T151, and E55), mutations disrupting intersubunit interactions had strong effects on receptor folding, assembly, and function. We next examined the role of a predicted intersubunit salt bridge for residue pair R158-D204. The mutant R158D, where the positively charged residue is replaced by a negatively charged aspartate, yielded a partially degraded receptor and lacked membrane surface expression. The membrane surface expression was rescued by the double mutant R158D-D204R, where positive and negative charges are switched, although the mutant receptor was inactive. The single mutants R158A, D204R, and D204A exhibited diminished activities and altered kinetic profiles with fast recovery kinetics, suggesting that R158-D204 salt bridge perhaps stabilizes the open state of the GABA(C) receptor. Our results emphasize the functional importance of highly conserved polar residues at the protein-protein interfaces in GABA(C) rho1 receptors and demonstrate how the integration of computational and experimental approaches can aid discovery of functionally important interactions.
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Affiliation(s)
- Larisa Adamian
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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