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Oikawa M, Sugeno Y, Tukada H, Takasaki Y, Takamizawa S, Irie R. Four Stereoisomers of 2-Aminomethyl-1-cyclopropanecarboxylic Acid: Synthesis and Biological Evaluation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2019. [DOI: 10.1246/bcsj.20190168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Masato Oikawa
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
| | - Yuka Sugeno
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
| | - Hideyuki Tukada
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
| | - Yuichi Takasaki
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
| | - Satoshi Takamizawa
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
| | - Raku Irie
- Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan
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2
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Synthesis of Racemic 2‐(Aminomethyl)cyclopropane‐1,1‐dicarboxylic Acid as a New Constrained γ‐Amino Dicarboxylic Acid Bypassing Alkyl 3‐Aza‐2‐oxobicyclo[3.1.0]hexane‐1‐carboxylates. European J Org Chem 2019. [DOI: 10.1002/ejoc.201900542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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3
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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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4
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Effects of bilobalide, ginkgolide B and picrotoxinin on GABA A receptor modulation by structurally diverse positive modulators. Eur J Pharmacol 2017; 806:83-90. [PMID: 28416372 DOI: 10.1016/j.ejphar.2017.04.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 04/11/2017] [Accepted: 04/13/2017] [Indexed: 12/20/2022]
Abstract
Anxiolytics and anticonvulsants generally positively modulate the action of GABA, whereas many convulsants (including the chloride channel blocker picrotoxinin) negatively modulate the action of GABA on GABAA receptors. Like picrotoxinin, bilobalide and ginkgolide B, active constituents of Ginkgo biloba, have been shown to negatively modulate the action of GABA at α1β2γ2L GABAA receptors. However, unlike picrotoxinin, bilobalide and ginkgolide B are not known to cause convulsions. We have assessed the action of bilobalide, ginkgolide B and picrotoxinin on a range of GABAA modulators (etomidate, loreclezole, propofol, thiopentone sodium, diazepam, and allopregnanolone), using two-electrode voltage clamp electrophysiology at recombinant α1β2γ2L GABAA receptors expressed in Xenopus oocytes. The results indicate that bilobalide and ginkgolide B differ from picrotoxinin in their ability to inhibit the actions of a range of these structurally diverse GABAA positive modulators consistent with these modulators acting on a multiplicity of active sites associated with GABAA receptors. In the presence GABA, ginkgolide B was more potent than bilobalide in inhibiting the GABA-potentiating effect of propofol, equipotent against loreclezole and allopregnanolone, and less potent against etomidate, diazepam, and thiopentone sodium. This indicates that in comparison to picrotoxinin, bilobalide and ginkgolide B differ in their effects on the different modulators.
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5
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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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6
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GABA Australis, some reflections on the history of GABA receptor research in Australia. Pharmacol Res 2016; 116:32-38. [PMID: 28017666 DOI: 10.1016/j.phrs.2016.12.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 12/10/2016] [Accepted: 12/21/2016] [Indexed: 12/12/2022]
Abstract
Research on GABA receptors has a long history in Australia dating from 1958 with David Curtis and his colleagues in Canberra. This review traces many of the advances made in Australia guided by highly cited publications and some obscure ones. It covers the discovery of key chemicals with which to investigate GABA receptor function including bicuculline, muscimol, phaclofen, THIP and (+)-CAMP. Also described are findings relevant to the involvement of mutant GABA receptors in inherited epilepsy. The modulation of GABA receptors by a bewildering range of chemicals, especially by flavonoids and terpenoids, is discussed.
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7
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Ordóñez M, Cativiela C, Romero-Estudillo I. An update on the stereoselective synthesis of γ-amino acids. ACTA ACUST UNITED AC 2016. [DOI: 10.1016/j.tetasy.2016.08.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Ng CC, Duke RK, Hinton T, Johnston GA. GABAA receptor cysteinyl mutants and the ginkgo terpenoid lactones bilobalide and ginkgolides. Eur J Pharmacol 2016; 777:136-46. [DOI: 10.1016/j.ejphar.2016.03.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 03/02/2016] [Accepted: 03/02/2016] [Indexed: 10/22/2022]
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9
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Stockton KP, Greatrex BW. Synthesis of enantiopure cyclopropyl esters from (−)-levoglucosenone. Org Biomol Chem 2016; 14:7520-8. [DOI: 10.1039/c6ob00933f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Levoglucosenone was converted into the GABAC agonists (−)-TAMP, (+)-TAMP and an advanced intermediate used for the synthesis of the selective glutamate receptor antagonist PCCG-4.
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Affiliation(s)
- Kieran P. Stockton
- School of Science and Technology
- University of New England
- Armidale
- Australia
| | - Ben W. Greatrex
- School of Science and Technology
- University of New England
- Armidale
- Australia
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10
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Rae C, Nasrallah FA, Balcar VJ, Rowlands BD, Johnston GAR, Hanrahan JR. Metabolomic Approaches to Defining the Role(s) of GABAρ Receptors in the Brain. J Neuroimmune Pharmacol 2015; 10:445-56. [PMID: 25577264 DOI: 10.1007/s11481-014-9579-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 12/26/2014] [Indexed: 10/24/2022]
Abstract
The inhibitory neurotransmitter γ-aminobutyric acid (GABA) acts through various types of receptors in the central nervous system. GABAρ receptors, defined by their characteristic pharmacology and presence of ρ subunits in the channel structure, are poorly understood and their role in the cortex is ill-defined. Here, we used a targeted pharmacological, NMR-based functional metabolomic approach in Guinea pig brain cortical tissue slices to identify a distinct role for these receptors. We compared metabolic fingerprints generated by a range of ligands active at GABAρ and included these in a principal components analysis with a library of other metabolic fingerprints obtained using ligands active at GABAA and GABAB, with inhibitors of GABA uptake and with compounds acting to inhibit enzymes active in the GABAergic system. This enabled us to generate a metabolic "footprint" of the GABAergic system which revealed classes of metabolic activity associated with GABAρ which are distinct from other GABA receptors. Antagonised GABAρ produce large metabolic effects at extrasynaptic sites suggesting they may be involved in tonic inhibition.
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Affiliation(s)
- Caroline Rae
- Neuroscience Research Australia, Barker St, Randwick, NSW, 2031, Australia,
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11
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Unsaturated Analogues of the Neurotransmitter GABA: trans-4-Aminocrotonic, cis-4-Aminocrotonic and 4-Aminotetrolic Acids. Neurochem Res 2015; 41:476-80. [DOI: 10.1007/s11064-015-1619-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
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12
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Absalom N, Yamamoto I, O'Hagan D, Hunter L, Chebib M. Probing the Mode of Neurotransmitter Binding to GABA Receptors Using Selectively Fluorinated GABA Analogues. Aust J Chem 2015. [DOI: 10.1071/ch14456] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Stereoselective fluorination is a useful technique for controlling the conformations of organic molecules. This concept has been exploited to create conformationally biased analogues of the neurotransmitter gamma-aminobutyric acid (GABA). Mono- and di-fluorinated GABA analogues are found to adopt different conformations, due to subtle stereoelectronic effects associated with the C–F bond. These conformationally biased GABA analogues exhibit different shape-dependent selectivity patterns towards GABAA, GABAB, and GABAC receptors, providing valuable information on the binding modes of the natural ligand at these medicinally important targets.
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Awada H, Robin S, Guillot R, Yazbeck O, Naoufal D, Jaber N, Hachem A, Aitken DJ. Practical Syntheses of Both Enantiomers of the Conformationally Restricted GABA Analoguecis-(2-Aminocyclobutyl)acetic Acid. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402676] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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14
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Sakai M, Tanaka K, Takamizawa S, Oikawa M. Enantiodivergent syntheses of (−)- and (+)-dysibetaine CPa and N-desmethyl analog. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.05.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Huang SH, Lewis TM, Lummis SC, Thompson AJ, Chebib M, Johnston GA, Duke RK. Mixed antagonistic effects of the ginkgolides at recombinant human ρ1 GABAC receptors. Neuropharmacology 2012; 63:1127-39. [PMID: 22828636 PMCID: PMC3465557 DOI: 10.1016/j.neuropharm.2012.06.067] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 06/18/2012] [Accepted: 06/24/2012] [Indexed: 11/26/2022]
Abstract
The diterpene lactones of Ginkgo biloba, ginkgolides A, B and C are antagonists at a range of Cys-loop receptors. This study examined the effects of the ginkgolides at recombinant human ρ(1) GABA(C) receptors expressed in Xenopus oocytes using two-electrode voltage clamp. The ginkgolides were moderately potent antagonists with IC(50)s in the μM range. At 10 μM, 30 μM and 100 μM, the ginkgolides caused rightward shifts of GABA dose-response curves and reduced maximal GABA responses, characteristic of noncompetitive antagonists, while the potencies showed a clear dependence on GABA concentration, indicating apparent competitive antagonism. This suggests that the ginkgolides exert a mixed-type antagonism at the ρ(1) GABA(C) receptors. The ginkgolides did not exhibit any obvious use-dependent inhibition. Fitting of the data to a number of kinetic schemes suggests an allosteric inhibition as a possible mechanism of action of the ginkgolides which accounts for their inhibition of the responses without channel block or use-dependent inhibition. Kinetic modelling predicts that the ginkgolides exhibit saturation of antagonism at high concentrations of GABA, but this was only partially observed for ginkgolide B. It also suggests that there may be different binding sites in the closed and open states of the receptor, with a higher affinity for the receptor in the closed state.
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Affiliation(s)
- Shelley H. Huang
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine, University of Sydney, Australia
| | - Trevor M. Lewis
- School of Medical Sciences, University of New South Wales, Australia
| | - Sarah C.R. Lummis
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Andrew J. Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, Australia
| | - Graham A.R. Johnston
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine, University of Sydney, Australia
| | - Rujee K. Duke
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine, University of Sydney, Australia
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16
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Yamamoto I, Jordan MJT, Gavande N, Doddareddy MR, Chebib M, Hunter L. The enantiomers of syn-2,3-difluoro-4-aminobutyric acid elicit opposite responses at the GABA(C) receptor. Chem Commun (Camb) 2011; 48:829-31. [PMID: 22143050 DOI: 10.1039/c1cc15816c] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The conformational behaviour and GABA receptor activity of the different stereoisomers of 2,3-difluoro-4-aminobutyric acid are described. Two enantiomeric GABA(C)-active ligands are identified, one of which is an agonist while the other is an antagonist. The results support an existing QSAR model of the bioactive geometry of GABA at GABA(C).
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Affiliation(s)
- Izumi Yamamoto
- Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia
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17
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Abstract
The inhibitory neurotransmitter, GABA, is a low-molecular-weight molecule that can achieve many low-energy conformations, which are recognized by GABA receptors and transporters. In this article, we assess the structure–activity relationship profiles of GABA analogs at the ionotropic ρ GABAC receptor. Such studies have significantly contributed to the design and development of potent and selective agonists and antagonists for this subclass of GABA receptors. With these tools in hand, the role of ρ GABAC receptors is slowly being realized. Of particular interest is the development of selective phosphinic acid analogs of GABA and their potential use in sleep disorders, inhibiting the development of myopia, and in improving learning and memory.
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18
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Conformationally restricted GABA analogs: from rigid carbocycles to cage hydrocarbons. Future Med Chem 2011; 3:223-41. [DOI: 10.4155/fmc.10.287] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
GABA was discovered to play an important role as the major inhibitory neurotransmitter in the adult mammalian CNS 60 years ago. The conformational flexibility of GABA is important for its biological function, as it has been found to bind to different receptors with different conformations. In an effort to increase the lipophilicity and to reduce conformational flexibility of GABA itself, a polycyclic or cage hydrocarbon framework can be introduced into the 3D structure of GABA in order to better control the binding. This article explores the available synthetic methods, properties and activity of carbocyclic (cyclopropanes, cyclobutanes and cyclohexanes) and cage (adamantane and others) hydrocarbons – analogs of GABA with conformationally rigid carbon skeletons.
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Aitken DJ, Drouin L, Goretta S, Guillot R, Ollivier J, Spiga M. Stereoselective preparation of β,γ-methano-GABA derivatives. Org Biomol Chem 2011; 9:7517-24. [DOI: 10.1039/c1ob06095c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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20
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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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Thommes K, Kiefer G, Scopelliti R, Severin K. Olefin Cyclopropanation by a Sequential Atom-Transfer Radical Addition and Dechlorination in the Presence of a Ruthenium Catalyst. Angew Chem Int Ed Engl 2009; 48:8115-9. [DOI: 10.1002/anie.200904278] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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22
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Thommes K, Kiefer G, Scopelliti R, Severin K. Olefin Cyclopropanation by a Sequential Atom-Transfer Radical Addition and Dechlorination in the Presence of a Ruthenium Catalyst. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200904278] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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23
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Synthesis and chromatographic resolution of conformationally constrained analogues of homotaurine. Tetrahedron 2009. [DOI: 10.1016/j.tet.2009.08.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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24
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Rae C, Nasrallah FA, Griffin JL, Balcar VJ. Now I know my ABC. A systems neurochemistry and functional metabolomic approach to understanding the GABAergic system. J Neurochem 2009; 109 Suppl 1:109-16. [DOI: 10.1111/j.1471-4159.2009.05803.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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25
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Chebib M, Gavande N, Wong KY, Park A, Premoli I, Mewett KN, Allan RD, Duke RK, Johnston GAR, Hanrahan JR. Guanidino Acids Act as ρ1 GABAC Receptor Antagonists. Neurochem Res 2009; 34:1704-11. [DOI: 10.1007/s11064-009-9968-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 03/30/2009] [Indexed: 11/24/2022]
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26
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Chebib M, Hinton T, Schmid KL, Brinkworth D, Qian H, Matos S, Kim HL, Abdel-Halim H, Kumar RJ, Johnston GAR, Hanrahan JR. Novel, potent, and selective GABAC antagonists inhibit myopia development and facilitate learning and memory. J Pharmacol Exp Ther 2008; 328:448-57. [PMID: 18984654 DOI: 10.1124/jpet.108.146464] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study reports pharmacological and physiological effects of cis- and trans-(3-aminocyclopentanyl)butylphosphinic acid (cis- and trans-3-ACPBPA). These compounds are conformationally restricted analogs of the orally active GABA(B/C) receptor antagonist (3-aminopropyl)-n-butylphosphinic acid (CGP36742 or SGS742). cis-[IC(50)(rho1) = 5.06 microM and IC(50)(rho2) = 11.08 microM; n = 4] and trans-3-ACPMPA [IC(50)(rho1) = 72.58 microM and IC(50)(rho2) = 189.7 microM; n = 4] seem competitive at GABA(C) receptors expressed in Xenopus laevis oocytes, having no effect as agonists (1 mM) but exerting weak antagonist (1 mM) effects on human GABA(A) and GABA(B) receptors. cis-3-ACPBPA was more potent and selective than the trans-compound, being more than 100 times more potent at GABA(C) than GABA(A) or GABA(B) receptors. cis-3-ACPBPA was further evaluated on dissociated rat retinal bipolar cells and dose-dependently inhibited the native GABA(C) receptor (IC(50) = 47 +/- 4.5 microM; n = 6). When applied to the eye as intravitreal injections, cis- and trans-3-ACPBPA prevented experimental myopia development and inhibited the associated vitreous chamber elongation, in a dose-dependent manner in the chick model. Doses only 10 times greater than required to inhibit recombinant GABA(C) receptors caused the antimyopia effects. Using intraperitoneal administration, cis- (30 mg/kg) and trans-3-ACPBPA (100 mg/kg) enhanced learning and memory in male Wistar rats; compared with vehicle there was a significant reduction in time for rats to find the platform in the Morris water maze task (p < 0.05; n = 10). As the physiological effects of cis- and trans-3-ACPBPA are similar to those reported for CGP36742, the memory and refractive effects of CGP36742 may be due in part to its GABA(C) activity.
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Affiliation(s)
- Mary Chebib
- Faculty of Pharmacy A15, The University of Sydney, Sydney, NSW 2006, Australia.
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Enantioselective actions of 4-amino-3-hydroxybutanoic acid and (3-amino-2-hydroxypropyl)methylphosphinic acid at recombinant GABAC receptors. Bioorg Med Chem Lett 2008; 18:402-4. [DOI: 10.1016/j.bmcl.2007.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Revised: 10/04/2007] [Accepted: 10/05/2007] [Indexed: 11/17/2022]
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28
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D'hooghe M, Vervisch K, Kimpe ND. Synthesis of 1-Arylmethyl-2-(2-cyanoethyl)aziridines and Their Rearrangement into Novel 2-(Aminomethyl)cyclopropanecarbonitriles. J Org Chem 2007; 72:7329-32. [PMID: 17705433 DOI: 10.1021/jo701302a] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1-Arylmethyl-2-(bromomethyl)aziridines were transformed into novel 2-(2-cyanoethyl)aziridines upon treatment with alpha-lithiated trimethylsilylacetonitrile in THF in an efficient and straightforward approach. The latter aziridines underwent ring opening by reaction with benzyl bromide in acetonitrile, affording 5-amino-4-bromopentanenitriles through a regiospecific ring opening of intermediate aziridinium salts by bromide. Further elaboration of these gamma-bromonitriles resulted in the synthesis of novel 2-[N,N-bis(arylmethyl)aminomethyl]cyclopropanecarbonitriles in high yields by means of a 1,3-cyclization protocol upon treatment with KOtBu in THF.
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Affiliation(s)
- Matthias D'hooghe
- Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
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Bröer S, Bröer A, Hansen JT, Bubb WA, Balcar VJ, Nasrallah FA, Garner B, Rae C. Alanine metabolism, transport, and cycling in the brain. J Neurochem 2007; 102:1758-1770. [PMID: 17504263 DOI: 10.1111/j.1471-4159.2007.04654.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Brain glutamate/glutamine cycling is incomplete without return of ammonia to glial cells. Previous studies suggest that alanine is an important carrier for ammonia transfer. In this study, we investigated alanine transport and metabolism in Guinea pig brain cortical tissue slices and prisms, in primary cultures of neurons and astrocytes, and in synaptosomes. Alanine uptake into astrocytes was largely mediated by system L isoform LAT2, whereas alanine uptake into neurons was mediated by Na(+)-dependent transporters with properties similar to system B(0) isoform B(0)AT2. To investigate the role of alanine transport in metabolism, its uptake was inhibited in cortical tissue slices under depolarizing conditions using the system L transport inhibitors 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid and cycloleucine (1-aminocyclopentanecarboxylic acid; cLeu). The results indicated that alanine cycling occurs subsequent to glutamate/glutamine cycling and that a significant proportion of cycling occurs via amino acid transport system L. Our results show that system L isoform LAT2 is critical for alanine uptake into astrocytes. However, alanine does not provide any significant carbon for energy or neurotransmitter metabolism under the conditions studied.
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Affiliation(s)
- Stefan Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Angelika Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Jonas T Hansen
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - William A Bubb
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Vladimir J Balcar
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Fatima A Nasrallah
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Brett Garner
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
| | - Caroline Rae
- School of Biochemistry and Molecular Biology, Australian National University, Acton, Canberra ACT, AustraliaSchool of Molecular and Microbial Biosciences, The University of Sydney, Sydney, New South Wales, AustraliaDepartment of Anatomy and Histology, The University of Sydney, Sydney, New South Wales, AustraliaPrince of Wales Medical Research Institute, Randwick, New South Wales, AustraliaSchool of Chemistry, The University of New South Wales, Sydney, New South Wales, Australia
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Chebib M, Hanrahan JR, Kumar RJ, Mewett KN, Morriss G, Wooller S, Johnston GAR. (3-Aminocyclopentyl)methylphosphinic acids: Novel GABAC receptor antagonists. Neuropharmacology 2007; 52:779-87. [PMID: 17098260 DOI: 10.1016/j.neuropharm.2006.09.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 08/28/2006] [Accepted: 09/25/2006] [Indexed: 12/30/2022]
Abstract
Our understanding of the role GABA(C) receptors play in the central nervous system is limited due to a lack of specific ligands. Here we describe the pharmacological effects of (+/-)-cis-3- and (+/-)-trans-3-(aminocyclopentyl)methylphosphinic acids ((+/-)-cis- and (+/-)-trans-3-ACPMPA) as novel ligands for the GABA(C) receptor showing little activity at GABA(A) or GABA(B) receptors. (+/-)-cis-3-ACPMPA has similar potency to (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) at human recombinant rho1 (K(B)=1.0+/-0.2microM) and rat rho3 (K(B)=5.4+/-0.8microM) but is 15 times more potent than TPMPA on human recombinant rho2 (K(B)=1.0+/-0.3microM) GABA(C) receptors expressed in Xenopus oocytes. (+/-)-cis- and (+/-)-trans-3-ACPMPA are novel lead compounds for developing into more potent and selective GABA(C) receptor antagonists with increased lipophilicity for in vivo studies.
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Affiliation(s)
- Mary Chebib
- Faculty of Pharmacy, Pharmacy Building A15, The University of Sydney, NSW 2006, Australia.
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Huang SH, Duke RK, Chebib M, Sasaki K, Wada K, Johnston GAR. Mixed antagonistic effects of bilobalide at ρ1 GABAC receptor. Neuroscience 2006; 137:607-17. [PMID: 16300902 DOI: 10.1016/j.neuroscience.2005.08.071] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Revised: 08/16/2005] [Accepted: 08/26/2005] [Indexed: 11/28/2022]
Abstract
Bilobalide was found to be a moderately potent antagonist with a weak use-dependent effect at recombinant human rho(1) GABA(C) receptors expressed in Xenopus oocytes using two-electrode voltage clamp methodology. Antagonism of bilobalide at homomeric rho(1) GABA(C) receptors appeared to be mixed. At low concentration, bilobalide (3 microM) caused a parallel right shift and surmountable GABA maximal response of the GABA dose-response curve characteristic of a competitive antagonist. At high concentrations, bilobalide (10-100 microM) caused nonparallel right shifts and reduced maximal GABA responses of GABA dose-response curves characteristic of a noncompetitive antagonist. The potency of bilobalide appears to be dependent on the concentrations of GABA and was more potent at lower GABA concentrations. The mechanism of action of bilobalide at rho(1) GABA(C) receptors appears to be similar to that of the chloride channel blocker picrotoxinin.
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Affiliation(s)
- S H Huang
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology D06, Faculty of Medicine, The University of Sydney, NSW 2006, Australia
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A quantitative structure–activity relationship investigation into agonist binding at GABAC receptors. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2005.07.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Crittenden DL, Park A, Qiu J, Silverman RB, Duke RK, Johnston GAR, Jordan MJT, Chebib M. Enantiomers of cis-constrained and flexible 2-substituted GABA analogues exert opposite effects at recombinant GABA(C) receptors. Bioorg Med Chem 2005; 14:447-55. [PMID: 16183289 DOI: 10.1016/j.bmc.2005.08.037] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 08/10/2005] [Accepted: 08/10/2005] [Indexed: 11/26/2022]
Abstract
The effects of the enantiomers of a number of flexible and cis-constrained GABA analogues were tested on GABA(C) receptors expressed in Xenopus laevis oocytes using two-electrode voltage-clamp electrophysiology. (1S,2R)-cis-2-Aminomethylcyclopropane-1-carboxylic acid ((+)-CAMP), a potent and full agonist at the rho1 (EC(50) approximately 40 microM, I(max) approximately 100%) and rho 2 (EC(50) approximately 17 microM, I(max) approximately 100%) receptor subtypes, was found to be a potent partial agonist at rho3 (EC(50) approximately 28 microM, I(max) approximately 70%). (1R,2S)-cis-2-Aminomethylcyclopropane-1-carboxylic acid ((-)-CAMP), a weak antagonist at human rho1 (IC(50) approximately 890 microM) and rho2 (IC(50) approximately 400 microM) receptor subtypes, was also found to be a moderately potent antagonist at rat rho3 (IC(50) approximately 180 microM). Similarly, (1R,4S)-4-aminocyclopent-2-ene-1-carboxylic acid ((+)-ACPECA) was a full agonist at rho1 (EC(50) approximately 135 microM, I(max) approximately 100%) and rho2 (EC(50) approximately 60 microM, I(max) approximately 100%), but only a partial agonist at rho3 (EC(50) approximately 112 microM, I(max) approximately 37%), while (1S,4R)-4-aminocyclopent-2-ene-1-carboxylic acid ((-)-ACPECA) was a weak antagonist at all three receptor subtypes (IC(50)>>300 microM). 4-Amino-(S)-2-methylbutanoic acid ((S)-2MeGABA) and 4-amino-(R)-2-methylbutanoic acid ((R)-2MeGABA) followed the same trend, with (S)-2MeGABA acting as a full agonist at the rho1 (EC(50) approximately 65 microM, I(max) approximately 100%), and rho2 (EC(50) approximately 20 microM, I(max) approximately 100%) receptor subtypes, and a partial agonist at rho3 (EC(50) approximately 25 microM, I(max) approximately 90%). (R)-2MeGABA, however, was a moderately potent antagonist at all three receptor subtypes (IC(50) approximately 16 microM at rho1, 125 microM at rho2 and 35 microM at rho3). On the basis of these expanded biological activity data and the solution-phase molecular structures obtained at the MP2/6-31+G* level of ab initio theory, a rationale is proposed for the genesis of this stereoselectivity effect.
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Abstract
1. The present review gives an overview of studies conducted on GABAC receptors over the past 10 years since the author started at the University of Sydney. It concentrates on the structure-activity relationship profiles of the receptor and how these studies were used to: (i) develop selective GABAC receptor ligands; and (ii) understand the impact of amino acid changes on GABAC receptor pharmacology and function. 2. Structure-activity relationship studies involving variations of both ligands and their receptor targets are vital to the discovery of drugs that interact selectively with particular native and mutant receptor subtypes. Such agents may be useful for treating anxiety, depression, epilepsy and memory related disorders, such as Alzheimer's disease.
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Affiliation(s)
- M Chebib
- Faculty of Pharmacy, University of Sydney, Sydney, New South Wales, Australia
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Carland JE, Moorhouse AJ, Barry PH, Johnston GAR, Chebib M. Charged Residues at the 2′ Position of Human GABAC ρ1 Receptors Invert Ion Selectivity and Influence Open State Probability. J Biol Chem 2004; 279:54153-60. [PMID: 15485818 DOI: 10.1074/jbc.m410625200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ability of members of the nicotinicoid superfamily of ligand-gated ion channels to selectively conduct anions or cations is critical to their function within the central nervous system. Recent work has demonstrated that residues at the intracellular end of the second transmembrane domain, between the -3' and 2' positions, form the ion selectivity filter of these receptors. In this study, the proline residue at the 2' position (Pro-2') at the intracellular end of the second transmembrane domain of the gamma-aminobutyric acid type C rho 1 subunit was mutated to glutamate (rho 1P2'E) and arginine (rho 1P2'R). Dilution potential experiments indicated that the charge selectivity of the rho 1P2'E receptor channels had been inverted, with the channels now becoming predominantly cation selective, indicating the ability of negatively charged residues at this 2' position to control charge selectivity. The mutation was also seen to have significantly decreased agonist potency and intrinsic efficacy. In contrast, the rho 1P2'R receptor channels were anion-selective but were now found to be constitutively open with high holding currents (inhibited by low gamma-aminobutyric acid doses and the competitive antagonist, 1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid alone) and increased agonist activity. Hill coefficients of both mutants were decreased, but competitive antagonist studies indicated that their binding sites were not significantly affected.
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Affiliation(s)
- Jane E Carland
- Faculty of Pharmacy, University of Sydney, New South Wales 2006, Australia
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Huang SH, Duke RK, Chebib M, Sasaki K, Wada K, Johnston GAR. Ginkgolides, diterpene trilactones of Ginkgo biloba, as antagonists at recombinant α1β2γ2L GABAA receptors. Eur J Pharmacol 2004; 494:131-8. [PMID: 15212966 DOI: 10.1016/j.ejphar.2004.04.051] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2003] [Revised: 03/17/2004] [Accepted: 04/30/2004] [Indexed: 11/17/2022]
Abstract
Ginkgolides A, B, and C are diterpene trilactones and active constituents of the 50:1 Ginkgo biloba leaf extract widely used in the symptomatic treatment of mild to moderate dementia. Using the two-electrode voltage clamp methodology, these ginkgolides were found to be moderately potent antagonists at recombinant human alpha(1)beta(2)gamma(2L) GABA(A) receptors expressed in Xenopus oocytes. Ginkgolides A, B, and C inhibited the direct action of gamma-aminobutyric acid (GABA) with K(i) values of 14.5+/-1.0, 12.7+/-1.7, and 16.3+/-2.4 microM respectively. Antagonism by these ginkgolides at alpha(1)beta(2)gamma(2L) GABA(A) receptors appears to be noncompetitive as indicated by the nonparallel right shift and reduced maximal GABA response in their GABA concentration-effect curves.
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Affiliation(s)
- Shelley H Huang
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology, Faculty of Medicine, The University of Sydney, Sydney, NSW 2006, Australia
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Duke RK, Chebib M, Hibbs DE, Mewett KN, Johnston GA. Synthesis and resolution of 2-methyl analogues of GABA. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.tetasy.2004.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Carland JE, Moore AM, Hanrahan JR, Mewett KN, Duke RK, Johnston GAR, Chebib M. Mutations of the 2' proline in the M2 domain of the human GABAC rho1 subunit alter agonist responses. Neuropharmacology 2004; 46:770-81. [PMID: 15033337 DOI: 10.1016/j.neuropharm.2003.11.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Revised: 11/11/2003] [Accepted: 11/25/2003] [Indexed: 10/26/2022]
Abstract
Mutations of the proline residue at the 2' position (P2') within the second transmembrane (M2) domain of the gamma-aminobutyric acid(C) (GABA(C)) rho1 subunit are known to produce receptors with altered pharmacology. In the present study, P2' was mutated to alanine (rho1P2'A), phenylalanine (rho1P2'F), glycine (rho1P2'G) and serine (rho1P2'S). Mutant receptors were characterized using a range of agonists, partial agonists and antagonists. rho1P2'A, rho1P2'G and rho1P2'S receptors were less susceptible than wild-type receptors to agonist activation. Most notably, the partial agonists, (+/-)-trans-2-(aminomethyl)cyclopropanoic acid ((+/-)-TAMP) and imidazole-4-acetic acid (I4AA) were converted to antagonists at rho1P2'G and rho1P2'S receptors and the partial agonist CACA acted as an antagonist at rho1P2'S receptors. In contrast, rho1P2'F receptors were more prone to activation by agonists. A correlation was observed between the pharmacological properties of the mutant receptors and the hydrophobicity of each residue. Unlike the agonists or partial agonists, the affinity of competitive antagonists, (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid (TPMPA) and 4,5,6,7-tetrahydroisoxazole[4,5-c]pyridine-3-ol (THIP), did not change significantly between wild-type and mutant receptors. Thus, the results suggest that the agonist/competitive antagonist binding site(s) were not significantly affected by the mutations, but that receptor activation properties altered such that the more hydrophobic the residue at the 2' position, the more prone the receptor is to agonist activation.
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Affiliation(s)
- Jane E Carland
- Faculty of Pharmacy, A15, University of Sydney, Sydney, NSW 2006, Australia
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40
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Ionotropic GABA Receptors as Therapeutic Targets for Memory and Sleep Disorders. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2004. [DOI: 10.1016/s0065-7743(04)39002-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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41
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Rae C, Hare N, Bubb WA, McEwan SR, Bröer A, McQuillan JA, Balcar VJ, Conigrave AD, Bröer S. Inhibition of glutamine transport depletes glutamate and GABA neurotransmitter pools: further evidence for metabolic compartmentation. J Neurochem 2003; 85:503-14. [PMID: 12675927 DOI: 10.1046/j.1471-4159.2003.01713.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The role of glutamine and alanine transport in the recycling of neurotransmitter glutamate was investigated in Guinea pig brain cortical tissue slices and prisms, and in cultured neuroblastoma and astrocyte cell lines. The ability of exogenous (2 mm) glutamine to displace 13C label supplied as [3-13C]pyruvate, [2-13C]acetate, l-[3-13C]lactate, or d-[1-13C]glucose was investigated using NMR spectroscopy. Glutamine transport was inhibited in slices under quiescent or depolarising conditions using histidine, which shares most transport routes with glutamine, or 2-(methylamino)isobutyric acid (MeAIB), a specific inhibitor of the neuronal system A. Glutamine mainly entered a large, slow turnover pool, probably located in neurons, which did not interact with the glutamate/glutamine neurotransmitter cycle. This uptake was inhibited by MeAIB. When [1-13C]glucose was used as substrate, glutamate/glutamine cycle turnover was inhibited by histidine but not MeAIB, suggesting that neuronal system A may not play a prominent role in neurotransmitter cycling. When transport was blocked by histidine under depolarising conditions, neurotransmitter pools were depleted, showing that glutamine transport is essential for maintenance of glutamate, GABA and alanine pools. Alanine labelling and release were decreased by histidine, showing that alanine was released from neurons and returned to astrocytes. The resultant implications for metabolic compartmentation and regulation of metabolism by transport processes are discussed.
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Affiliation(s)
- Caroline Rae
- Discipline of Biochemistry, School of Molecular & Microbial Biosciences, The University of Sydney, New South Wales, Australia.
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Huang SH, Duke RK, Chebib M, Sasaki K, Wada K, Johnston GAR. Bilobalide, a sesquiterpene trilactone from Ginkgo biloba, is an antagonist at recombinant alpha1beta2gamma2L GABA(A) receptors. Eur J Pharmacol 2003; 464:1-8. [PMID: 12600688 DOI: 10.1016/s0014-2999(03)01344-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The sesquiterpene trilactone bilobalide is one of the active constituents of the 50:1 Ginkgo biloba leaf extract widely used to enhance memory and learning. Bilobalide was found to antagonise the direct action of gamma-aminobutyric acid (GABA) on recombinant alpha(1)beta(2)gamma(2L) GABA(A) receptors. The effect of bilobalide on the direct action of GABA at alpha(1)beta(2)gamma(2L) GABA(A) receptors expressed in Xenopus laevis oocytes using two-electrode voltage-clamp method was evaluated and compared with the effects of the classical GABA(A) receptor competitive antagonist bicuculline and noncompetitive antagonist picrotoxinin. Bilobalide (IC(50)=4.6+/-0.5 microM) was almost as potent as bicuculline and pictrotoxinin (IC(50)=2.0+/-0.1 and 2.4+/-0.5 microM, respectively) at alpha(1)beta(2)gamma(2L) GABA(A) receptors against 40 microM GABA (GABA EC(50)). While bilobalide and picrotoxinin were clearly noncompetitive antagonists, the potency of bilobalide decreased at high GABA concentrations suggesting a component of competitive antagonism.
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Affiliation(s)
- Shelley H Huang
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology, Faculty of Medicine, University of Sydney, NSW 2006, Sydney, Australia
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Vien J, Duke RK, Mewett KN, Johnston GAR, Shingai R, Chebib M. trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA) and (+/-)-trans-2-aminomethylcyclopropanecarboxylic acid ((+/-)-TAMP) can differentiate rat rho3 from human rho1 and rho2 recombinant GABA(C) receptors. Br J Pharmacol 2002; 135:883-90. [PMID: 11861315 PMCID: PMC1573190 DOI: 10.1038/sj.bjp.0704432] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study investigated the effects of a number of GABA analogues on rat rho3 GABA(C) receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. 2. The potency order of agonists was muscimol (EC(50)=1.9 +/- 0.1 microM) (+)-trans-3-aminocyclopentanecarboxylic acids ((+)-TACP; EC(50)=2.7 +/- 0.9 microM) trans-4-aminocrotonic acid (TACA; EC(50)=3.8 +/-0.3 microM) GABA (EC(50)=4.0 +/- 0.3 microM) > thiomuscimol (EC(50)=24.8 +/- 2.6 microM) > (+/-)-cis-2-aminomethylcyclopropane-carboxylic acid ((+/-)-CAMP; EC(50)=52.6 +/-8.7 microM) > cis-4-aminocrotonic acid (CACA; EC(50)=139.4 +/- 5.2 microM). 3. The potency order of antagonists was (+/-)-trans-2-aminomethylcyclopropanecarboxylic acid ((+/-)-TAMP; K(B)=4.8+/-1.8 microM) (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA; K(B)=4.8 +/-0.8 microM) > (piperidin-4-yl)methylphosphinic acid (P4MPA; K(B)=10.2+/-2.3 microM) 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP; K(B)=10.2+/-0.3 microM) imidazole-4-acetic acid (I4AA; K(B)=12.6+/-2.7 microM) > 3-aminopropylphosphonic acid (3-APA; K(B)=35.8+/-13.5 microM). 4. trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA; 300 microM) had no effect as an agonist or an antagonist indicating that the C2 methyl substituent is sterically interacting with the ligand-binding site of rat rho3 GABA(C) receptors. 5. 2-MeTACA affects rho1 and rho2 but not rho3 GABA(C) receptors. In contrast, (plus minus)-TAMP is a partial agonist at rho1 and rho2 GABA(C) receptors, while at rat rho3 GABA(C) receptors it is an antagonist. Thus, 2-MeTACA and (+/-)-TAMP could be important pharmacological tools because they may functionally differentiate between rho1, rho2 and rho3 GABA(C) receptors in vitro.
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Affiliation(s)
- Jimmy Vien
- Department of Pharmacology, University of Sydney, NSW 2006, Australia
| | - Rujee K Duke
- Department of Pharmacology, University of Sydney, NSW 2006, Australia
| | - Kenneth N Mewett
- Department of Pharmacology, University of Sydney, NSW 2006, Australia
| | | | - Ryuzo Shingai
- Department of Welfare Engineering, Faculty of Engineering, Iwate University, Morioka, Japan
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, NSW 2006, Australia
- Author for correspondence:
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Chebib M, Duke RK, Allan RD, Johnston GA. The effects of cyclopentane and cyclopentene analogues of GABA at recombinant GABA(C) receptors. Eur J Pharmacol 2001; 430:185-92. [PMID: 11711030 DOI: 10.1016/s0014-2999(01)01390-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pharmacological effects of the enantiomers of cis-3-aminocyclopentanecarboxylic acids ((+)- and (-)-CACP), the enantiomers of trans-3-aminocyclopentanecarboxylic acids ((+)- and (-)-TACP), and the enantiomers of 4-aminocyclopent-1-ene-1-carboxylic acids ((+)- and (-)-4-ACPCA) were studied on human homomeric rho(1) and rho(2) GABA(C) receptors expressed in Xenopus oocytes using two-electrode voltage clamp methods. These compounds are conformationally restricted analogues of gamma-aminobutyric acid (GABA) held in a five-membered ring. (+)-TACP (EC(50) (rho(1))=2.7+/-0.2 microM; EC(50) (rho(2))=1.45+/-0.22 microM), (+)-CACP (EC(50) (rho(1))=26.1+/-1.1 microM; EC(50) (rho(2))=20.1+/-2.1 microM) and (-)-CACP (EC(50) (rho(1))=78.5+/-3.5 microM; EC(50) (rho(2))=63.8+/-23.3 microM) were moderately potent partial agonists at rho(1) and rho(2) GABA(C) receptors, while (-)-TACP (100 microM inhibited 56% and 62% of the current produced by 1 microM GABA at rho(1) and rho(2) receptors, respectively) was a weak partial agonist with low intrinsic activity at these receptors. In contrast, (+)-4-ACPCA (K(i) (rho(1))=6.0+/-0.1 microM; K(i) (rho(2))=4.7+/-0.3 microM) did not activate GABA(C) rho(1) and rho(2) receptors but potently inhibited the action of GABA at these receptors, while (-)-4-ACPCA had little effect as either an agonist or an antagonist. The affinity order at both GABA(C) rho(1) and rho(2) receptors was (+)-TACP>(+)-4-ACPCA >> (+)-CACP>(-)-CACP >> (-)-TACP >> (-)-4-ACPCA. This study shows that the cyclopentane and cyclopentene analogues of GABA affect GABA(C) receptors in a unique manner, defining a preferred stereochemical orientation of the amine and carboxylic acid groups when binding to GABA(C) receptors. This is exemplified by the partial agonist, (+)-TACP, and the antagonist, (+)-4-ACPCA.
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Affiliation(s)
- M Chebib
- Faculty of Pharmacy, Department of Pharmacology, The University of Sydney, NSW 2006, Sydney, Australia.
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