1
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Bhatt M, Gauthier-Manuel L, Lazzarin E, Zerlotti R, Ziegler C, Bazzone A, Stockner T, Bossi E. A comparative review on the well-studied GAT1 and the understudied BGT-1 in the brain. Front Physiol 2023; 14:1145973. [PMID: 37123280 PMCID: PMC10137170 DOI: 10.3389/fphys.2023.1145973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/30/2023] [Indexed: 05/02/2023] Open
Abstract
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system (CNS). Its homeostasis is maintained by neuronal and glial GABA transporters (GATs). The four GATs identified in humans are GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11), and betaine/GABA transporter-1 BGT-1 (SLC6A12) which are all members of the solute carrier 6 (SLC6) family of sodium-dependent transporters. While GAT1 has been investigated extensively, the other GABA transporters are less studied and their role in CNS is not clearly defined. Altered GABAergic neurotransmission is involved in different diseases, but the importance of the different transporters remained understudied and limits drug targeting. In this review, the well-studied GABA transporter GAT1 is compared with the less-studied BGT-1 with the aim to leverage the knowledge on GAT1 to shed new light on the open questions concerning BGT-1. The most recent knowledge on transporter structure, functions, expression, and localization is discussed along with their specific role as drug targets for neurological and neurodegenerative disorders. We review and discuss data on the binding sites for Na+, Cl-, substrates, and inhibitors by building on the recent cryo-EM structure of GAT1 to highlight specific molecular determinants of transporter functions. The role of the two proteins in GABA homeostasis is investigated by looking at the transport coupling mechanism, as well as structural and kinetic transport models. Furthermore, we review information on selective inhibitors together with the pharmacophore hypothesis of transporter substrates.
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Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
| | - Laure Gauthier-Manuel
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
| | - Rocco Zerlotti
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
- Nanion Technologies GmbH, Munich, Germany
| | - Christine Ziegler
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | | | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Waehringerstr, Vienna
- *Correspondence: Thomas Stockner, ; Elena Bossi,
| | - Elena Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
- Centre for Neuroscience—University of Insubria, Varese, Italy
- *Correspondence: Thomas Stockner, ; Elena Bossi,
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2
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Abstract
γ-Aminobutyric acid (GABA) transporter 1 (GAT1)1 regulates neuronal excitation of the central nervous system by clearing the synaptic cleft of the inhibitory neurotransmitter GABA upon its release from synaptic vesicles. Elevating the levels of GABA in the synaptic cleft, by inhibiting GABA reuptake transporters, is an established strategy to treat neurological disorders, such as epilepsy2. Here we determined the cryo-electron microscopy structure of full-length, wild-type human GAT1 in complex with its clinically used inhibitor tiagabine3, with an ordered part of only 60 kDa. Our structure reveals that tiagabine locks GAT1 in the inward-open conformation, by blocking the intracellular gate of the GABA release pathway, and thus suppresses neurotransmitter uptake. Our results provide insights into the mixed-type inhibition of GAT1 by tiagabine, which is an important anticonvulsant medication. Its pharmacodynamic profile, confirmed by our experimental data, suggests initial binding of tiagabine to the substrate-binding site in the outward-open conformation, whereas our structure presents the drug stalling the transporter in the inward-open conformation, consistent with a two-step mechanism of inhibition4. The presented structure of GAT1 gives crucial insights into the biology and pharmacology of this important neurotransmitter transporter and provides blueprints for the rational design of neuromodulators, as well as moving the boundaries of what is considered possible in single-particle cryo-electron microscopy of challenging membrane proteins.
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3
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Pukale DD, Farrag M, Gudneppanavar R, Baumann HJ, Konopka M, Shriver LP, Leipzig ND. Osmoregulatory Role of Betaine and Betaine/γ-Aminobutyric Acid Transporter 1 in Post-Traumatic Syringomyelia. ACS Chem Neurosci 2021; 12:3567-3578. [PMID: 34550670 DOI: 10.1021/acschemneuro.1c00056] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Syringomyelia (SM) is primarily characterized by the formation of a fluid-filled cyst that forms in the parenchyma of the spinal cord following injury or other pathology. Recent omics studies in animal models have identified dysregulation of solute carriers, channels, transporters, and small molecules associated with osmolyte regulation during syrinx formation/expansion in the spinal cord. However, their connections to syringomyelia etiology are poorly understood. In this study, the biological functions of the potent osmolyte betaine and its associated solute carrier betaine/γ-aminobutyric acid (GABA) transporter 1 (BGT1) were studied in SM. First, a rat post-traumatic SM model was used to demonstrate that the BGT1 was primarily expressed in astrocytes in the vicinity of syrinxes. In an in vitro system, we found that astrocytes uptake betaine through BGT1 to regulate cell size under hypertonic conditions. Treatment with BGT1 inhibitors, especially NNC 05-2090, demonstrated midhigh micromolar range potency in vitro that reversed the osmoprotective effects of betaine. Finally, the specificity of these BGT1 inhibitors in the CNS was demonstrated in vivo, suggesting feasibility for targeting betaine transport in SM. In summary, these data provide an enhanced understanding of the role of betaine and its associated solute carrier BGT1 in cell osmoregulation and implicates the active role of betaine and BGT1 in syringomyelia progression.
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Affiliation(s)
- Dipak D. Pukale
- Department of Chemical, Biomolecular, and Corrosion Engineering, University of Akron, Akron, Ohio 44325, United States
| | - Mahmoud Farrag
- Integrated Biosciences Program, University of Akron, Akron, Ohio 44325, United States
| | | | - Hannah J. Baumann
- Department of Chemistry, University of Akron, Akron, Ohio 44325, United States
| | - Michael Konopka
- Department of Chemistry, University of Akron, Akron, Ohio 44325, United States
| | - Leah P. Shriver
- Integrated Biosciences Program, University of Akron, Akron, Ohio 44325, United States
- Department of Chemistry, University of Akron, Akron, Ohio 44325, United States
| | - Nic D. Leipzig
- Department of Chemical, Biomolecular, and Corrosion Engineering, University of Akron, Akron, Ohio 44325, United States
- Integrated Biosciences Program, University of Akron, Akron, Ohio 44325, United States
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4
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Kickinger S, Lie MEK, Suemasa A, Al-Khawaja A, Fujiwara K, Watanabe M, Wilhelmsen KS, Falk-Petersen CB, Frølund B, Shuto S, Ecker GF, Wellendorph P. Molecular Determinants and Pharmacological Analysis for a Class of Competitive Non-transported Bicyclic Inhibitors of the Betaine/GABA Transporter BGT1. Front Chem 2021; 9:736457. [PMID: 34595152 PMCID: PMC8476755 DOI: 10.3389/fchem.2021.736457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/30/2021] [Indexed: 11/17/2022] Open
Abstract
The betaine/GABA transporter 1 (BGT1) is a member of the GABA transporter (GAT) family with still elusive function, largely due to a lack of potent and selective tool compounds. Based on modeling, we here present the design, synthesis and pharmacological evaluation of five novel conformationally restricted cyclic GABA analogs related to the previously reported highly potent and selective BGT1 inhibitor (1S,2S,5R)-5-aminobicyclo[3.1.0]hexane-2-carboxylic acid (bicyclo-GABA). Using [3H]GABA radioligand uptake assays at the four human GATs recombinantly expressed in mammalian cell lines, we identified bicyclo-GABA and its N-methylated analog (2) as the most potent and selective BGT1 inhibitors. Additional pharmacological characterization in a fluorescence-based membrane potential assay showed that bicyclo-GABA and 2 are competitive inhibitors, not substrates, at BGT1, which was validated by a Schild analysis for bicyclo-GABA (pKB value of 6.4). To further elaborate on the selectivity profile both compounds were tested at recombinant α1β2γ2 GABAA receptors. Whereas bicyclo-GABA showed low micromolar agonistic activity, the N-methylated 2 was completely devoid of activity at GABAA receptors. To further reveal the binding mode of bicyclo-GABA and 2 binding hypotheses of the compounds were obtained from in silico-guided mutagenesis studies followed by pharmacological evaluation at selected BGT1 mutants. This identified the non-conserved BGT1 residues Q299 and E52 as the molecular determinants driving BGT1 activity and selectivity. The binding mode of bicyclo-GABA was further validated by the introduction of activity into the corresponding GAT3 mutant L314Q (38 times potency increase cf. wildtype). Altogether, our data reveal the molecular determinants for the activity of bicyclic GABA analogs, that despite their small size act as competitive inhibitors of BGT1. These compounds may serve as valuable tools to selectively and potently target BGT1 in order to decipher its elusive pharmacological role in the brain and periphery such as the liver and kidneys.
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Affiliation(s)
- Stefanie Kickinger
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Pharmaceutical Science, University of Vienna, Vienna, Austria
| | - Maria E K Lie
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Akihiro Suemasa
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Anas Al-Khawaja
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Koichi Fujiwara
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Mizuki Watanabe
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Kristine S Wilhelmsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina B Falk-Petersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Satoshi Shuto
- Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
| | - Gerhard F Ecker
- Department of Pharmaceutical Science, University of Vienna, Vienna, Austria
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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5
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Zaręba P, Sałat K, Höfner GC, Łątka K, Bajda M, Latacz G, Kotniewicz K, Rapacz A, Podkowa A, Maj M, Jóźwiak K, Filipek B, Wanner KT, Malawska B, Kulig K. Development of tricyclic N-benzyl-4-hydroxybutanamide derivatives as inhibitors of GABA transporters mGAT1-4 with anticonvulsant, antinociceptive, and antidepressant activity. Eur J Med Chem 2021; 221:113512. [PMID: 34015586 DOI: 10.1016/j.ejmech.2021.113512] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 04/20/2021] [Accepted: 04/22/2021] [Indexed: 01/04/2023]
Abstract
γ-Aminobutyric acid (GABA) neurotransmission has a significant impact on the proper functioning of the central nervous system. Numerous studies have indicated that inhibitors of the GABA transporters mGAT1-4 offer a promising strategy for the treatment of several neurological disorders, including epilepsy, neuropathic pain, and depression. Following our previous results, herein, we report the synthesis, biological evaluation, and structure-activity relationship studies supported by molecular docking and molecular dynamics of a new series of N-benzyl-4-hydroxybutanamide derivatives regarding their inhibitory potency toward mGAT1-4. This study allowed us to identify compound 23a (N-benzyl-4-hydroxybutanamide bearing a dibenzocycloheptatriene moiety), a nonselective GAT inhibitor with a slight preference toward mGAT4 (pIC50 = 5.02 ± 0.11), and compound 24e (4-hydroxy-N-[(4-methylphenyl)-methyl]butanamide bearing a dibenzocycloheptadiene moiety) with relatively high inhibitory activity toward mGAT2 (pIC50 = 5.34 ± 0.09). In a set of in vivo experiments, compound 24e successively showed predominant anticonvulsant activity and antinociception in the formalin model of tonic pain. In contrast, compound 23a showed significant antidepressant-like properties in mice. These results were consistent with the available literature data, which indicates that, apart from seizure control, GABAergic neurotransmission is also involved in the pathophysiology of several psychiatric diseases, however alternative mechanisms underlying this action cannot be excluded. Finally, it is worth noting that the selected compounds showed unimpaired locomotor skills that have been indicated to give reliable results in behavioral assays.
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Affiliation(s)
- Paula Zaręba
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland.
| | - Kinga Sałat
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Georg C Höfner
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München Butenandtstr, 5-13, 81377, Munich, Germany
| | - Kamil Łątka
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Marek Bajda
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Gniewomir Latacz
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Krzysztof Kotniewicz
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Anna Rapacz
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Adrian Podkowa
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Maciej Maj
- Department of Biopharmacy, Medical University of Lublin, ul. W. Chodzki 4a, 20-093, Lublin, Poland
| | - Krzysztof Jóźwiak
- Department of Biopharmacy, Medical University of Lublin, ul. W. Chodzki 4a, 20-093, Lublin, Poland
| | - Barbara Filipek
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Klaus T Wanner
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München Butenandtstr, 5-13, 81377, Munich, Germany
| | - Barbara Malawska
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
| | - Katarzyna Kulig
- Faculty of Pharmacy, Jagiellonian University Medical College, 9 Medyczna St, 30-688, Kraków, Poland
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6
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Exploring the molecular determinants for subtype-selectivity of 2-amino-1,4,5,6-tetrahydropyrimidine-5-carboxylic acid analogs as betaine/GABA transporter 1 (BGT1) substrate-inhibitors. Sci Rep 2020; 10:12992. [PMID: 32747622 PMCID: PMC7400577 DOI: 10.1038/s41598-020-69908-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 07/17/2020] [Indexed: 12/13/2022] Open
Abstract
We have previously identified 2-amino-1,4,5,6-tetrahydropyrimidine-5-carboxylic acid (ATPCA) as the most potent substrate-inhibitor of the betaine/GABA transporter 1 (BGT1) (IC50 2.5 µM) reported to date. Herein, we characterize the binding mode of 20 novel analogs and propose the molecular determinants driving BGT1-selectivity. A series of N1-, exocyclic-N-, and C4-substituted analogs was synthesized and pharmacologically characterized in radioligand-based uptake assays at the four human GABA transporters (hGATs) recombinantly expressed in mammalian cells. Overall, the analogs retained subtype-selectivity for hBGT1, though with lower inhibitory activities (mid to high micromolar IC50 values) compared to ATPCA. Further characterization of five of these BGT1-active analogs in a fluorescence-based FMP assay revealed that the compounds are substrates for hBGT1, suggesting they interact with the orthosteric site of the transporter. In silico-guided mutagenesis experiments showed that the non-conserved residues Q299 and E52 in hBGT1 as well as the conformational flexibility of the compounds potentially contribute to the subtype-selectivity of ATPCA and its analogs. Overall, this study provides new insights into the molecular interactions governing the subtype-selectivity of BGT1 substrate-inhibitors. The findings may guide the rational design of BGT1-selective pharmacological tool compounds for future drug discovery.
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7
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El-Chami C, Foster AR, Johnson C, Clausen RP, Cornwell P, Haslam IS, Steward MC, Watson REB, Young HS, O'Neill CA. Organic osmolytes increase expression of specific tight junction proteins in skin and alter barrier function in keratinocytes. Br J Dermatol 2020; 184:482-494. [PMID: 32348549 DOI: 10.1111/bjd.19162] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND The epidermal barrier is important for water conservation, failure of which is evident in dry-skin conditions. Barrier function is fulfilled by the stratum corneum, tight junctions (TJs, which control extracellular water) and keratinocyte mechanisms, such as organic osmolyte transport, which regulate intracellular water homeostasis. Organic osmolyte transport by keratinocytes is largely unexplored and nothing is known regarding how cellular and extracellular mechanisms of water conservation may interact. OBJECTIVES We aimed to characterize osmolyte transporters in skin and keratinocytes, and, using transporter inhibitors, to investigate whether osmolytes can modify TJs. Such modification would suggest a possible link between intracellular and extracellular mechanisms of water regulation in skin. METHODS Immunostaining and quantitative polymerase chain reaction of organic osmolyte-treated organ-cultured skin were used to identify changes to organic osmolyte transporters, and TJ protein and gene expression. TJ functional assays were performed on organic osmolyte-treated primary human keratinocytes in culture. RESULTS Immunostaining demonstrated the expression of transporters for betaine, taurine and myo-inositol in transporter-specific patterns. Treatment of human skin with either betaine or taurine increased the expression of claudin-1, claudin-4 and occludin. Osmolyte transporter inhibition abolished this response. Betaine and taurine increased TJ function in primary human keratinocytes in vitro. CONCLUSIONS Treatment of skin with organic osmolytes modulates TJ structure and function, which could contribute to the epidermal barrier. This emphasizes a role for organic osmolytes beyond the maintenance of intracellular osmolarity. This could be harnessed to enhance topical therapies for diseases characterized by skin barrier dysfunction.
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Affiliation(s)
- C El-Chami
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
| | - A R Foster
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
| | - C Johnson
- School of Electrical and Electronic Engineering, Faculty of Science and Engineering, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
| | - R P Clausen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - P Cornwell
- TRI Princeton, 601 Prospect Avenue, Princeton, NJ, 08540, USA
| | - I S Haslam
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.,Department of Biological Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK
| | - M C Steward
- Division of Diabetes, Endocrinology and Gastroenterology, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
| | - R E B Watson
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.,NIHR Manchester Biomedical Research Centre, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - H S Young
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.,Department of Dermatology, Salford Royal NHS Foundation Trust, Manchester, UK
| | - C A O'Neill
- Centre for Dermatology Research, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
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8
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Łątka K, Jończyk J, Bajda M. Structure modeling of γ-aminobutyric acid transporters - Molecular basics of ligand selectivity. Int J Biol Macromol 2020; 158:S0141-8130(20)33135-4. [PMID: 32376252 DOI: 10.1016/j.ijbiomac.2020.04.263] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/28/2020] [Accepted: 04/29/2020] [Indexed: 11/15/2022]
Abstract
γ-Aminobutyric acid transporters are responsible for regulating the GABA level in the synaptic cleft. In this way, they affect GABA-ergic transmission which is important for the proper functioning of the central nervous system. The exact structure of GABA transporters is still unknown, which hinders the design of new, potent and selective inhibitors. For these reasons, we decided to create models of all types of human gamma-aminobutyric acid transporters. They were built based on crystal structures of related proteins from the SLC6 family using homology modeling methods. The reliability of the received models has been confirmed by a number of tools assessing the quality of protein models. To determine the ligand binding mode and indicate the amino acids responsible for selectivity, docking studies and molecular dynamics simulations were performed. The amino acids lining the bottom of the main binding site have a major impact on the selective ligand binding. In addition, an important element is the non-helical fragment of the transmembrane domain 10, and several amino acids within the vestibule of the transporters, which affect its volume. To check whether obtained models are suitable to distinguish active compounds from inactive ones, enrichment plots were prepared. Results suggest that our models may be useful in the search for new inhibitors of GABA transporters of the desired selectivity.
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Affiliation(s)
- Kamil Łątka
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland
| | - Jakub Jończyk
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland
| | - Marek Bajda
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland.
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9
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Łątka K, Jończyk J, Bajda M. γ-Aminobutyric acid transporters as relevant biological target: Their function, structure, inhibitors and role in the therapy of different diseases. Int J Biol Macromol 2020; 158:S0141-8130(20)32987-1. [PMID: 32360967 DOI: 10.1016/j.ijbiomac.2020.04.126] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 04/17/2020] [Accepted: 04/18/2020] [Indexed: 12/13/2022]
Abstract
γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the nervous system. It plays a crucial role in many physiological processes. Upon release from the presynaptic element, it is removed from the synaptic cleft by reuptake due to the action of GABA transporters (GATs). GATs belong to a large SLC6 protein family whose characteristic feature is sodium-dependent relocation of neurotransmitters through the cell membrane. GABA transporters are characterized in many contexts, but their spatial structure is not fully known. They are divided into four types, which differ in occurrence and role. Herein, the special attention was paid to these transporting proteins. This comprehensive review presents the current knowledge about GABA transporters. Their distribution in the body, physiological functions and possible utilization in the therapy of different diseases were fully discussed. The important structural features were described based on published data, including sequence analysis, mutagenesis studies, and comparison with known SLC6 transporters for leucine (LeuT), dopamine (DAT) and serotonin (SERT). Moreover, the most important inhibitors of GABA transporters of various basic scaffolds, diverse selectivity and potency were presented.
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Affiliation(s)
- Kamil Łątka
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland
| | - Jakub Jończyk
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland
| | - Marek Bajda
- Jagiellonian University Medical College, Faculty of Pharmacy, Department of Physicochemical Drug Analysis, 30-688 Cracow, Medyczna 9, Poland.
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10
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Lie MEK, Kickinger S, Skovgaard-Petersen J, Ecker GF, Clausen RP, Schousboe A, White HS, Wellendorph P. Pharmacological Characterization of a Betaine/GABA Transporter 1 (BGT1) Inhibitor Displaying an Unusual Biphasic Inhibition Profile and Anti-seizure Effects. Neurochem Res 2020; 45:1551-1565. [PMID: 32248400 PMCID: PMC7297817 DOI: 10.1007/s11064-020-03017-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/09/2020] [Accepted: 03/18/2020] [Indexed: 12/01/2022]
Abstract
Focal epileptic seizures can in some patients be managed by inhibiting γ-aminobutyric acid (GABA) uptake via the GABA transporter 1 (GAT1) using tiagabine (Gabitril®). Synergistic anti-seizure effects achieved by inhibition of both GAT1 and the betaine/GABA transporter (BGT1) by tiagabine and EF1502, compared to tiagabine alone, suggest BGT1 as a target in epilepsy. Yet, selective BGT1 inhibitors are needed for validation of this hypothesis. In that search, a series of BGT1 inhibitors typified by (1R,2S)-2-((4,4-bis(3-methylthiophen-2-yl)but-3-en-yl)(methyl)amino)cyclohexanecarboxylic acid (SBV2-114) was developed. A thorough pharmacological characterization of SBV2-114 using a cell-based [3H]GABA uptake assay at heterologously expressed BGT1, revealed an elusive biphasic inhibition profile with two IC50 values (4.7 and 556 μM). The biphasic profile was common for this structural class of compounds, including EF1502, and was confirmed in the MDCK II cell line endogenously expressing BGT1. The possibility of two binding sites for SBV2-114 at BGT1 was assessed by computational docking studies and examined by mutational studies. These investigations confirmed that the conserved residue Q299 in BGT1 is involved in, but not solely responsible for the biphasic inhibition profile of SBV2-114. Animal studies revealed anti-seizure effects of SBV2-114 in two mouse models, supporting a function of BGT1 in epilepsy. However, as SBV2-114 is apparent to be rather non-selective for BGT1, the translational relevance of this observation is unknown. Nevertheless, SBV2-114 constitutes a valuable tool compound to study the molecular mechanism of an emerging biphasic profile of BGT1-mediated GABA transport and the putative involvement of two binding sites for this class of compounds.
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Affiliation(s)
- Maria E K Lie
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Stefanie Kickinger
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | | | - Gerhard F Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Rasmus P Clausen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - H Steve White
- Department of Pharmacy, University of Washington, Washington, USA
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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Kickinger S, Hellsberg E, Frølund B, Schousboe A, Ecker GF, Wellendorph P. Structural and molecular aspects of betaine-GABA transporter 1 (BGT1) and its relation to brain function. Neuropharmacology 2019; 161:107644. [PMID: 31108110 DOI: 10.1016/j.neuropharm.2019.05.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 04/14/2019] [Accepted: 05/16/2019] [Indexed: 01/09/2023]
Abstract
ɣ-aminobutyric-acid (GABA) functions as the principal inhibitory neurotransmitter in the central nervous system. Imbalances in GABAergic neurotransmission are involved in the pathophysiology of various neurological diseases such as epilepsy, Alzheimer's disease and stroke. GABA transporters (GATs) facilitate the termination of GABAergic signaling by transporting GABA together with sodium and chloride from the synaptic cleft into presynaptic neurons and surrounding glial cells. Four different GATs have been identified that all belong to the solute carrier 6 (SLC6) transporter family: GAT1-3 (SLC6A1, SLC6A13, SLC6A11) and betaine/GABA transporter 1 (BGT1, SLC6A12). BGT1 has emerged as an interesting target for treating epilepsy due to animal studies that reported anticonvulsant effects for the GAT1/BGT1 selective inhibitor EF1502 and the BGT1 selective inhibitor RPC-425. However, the precise involvement of BGT1 in epilepsy remains elusive because of its controversial expression levels in the brain and the lack of highly selective and potent tool compounds. This review gathers the current structural and functional knowledge on BGT1 with emphasis on brain relevance, discusses all available compounds, and tries to shed light on the molecular determinants driving BGT1 selectivity. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- Stefanie Kickinger
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Eva Hellsberg
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Bente Frølund
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark
| | - Arne Schousboe
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark
| | - Gerhard F Ecker
- University of Vienna, Department of Pharmaceutical Chemistry, Althanstrasse 14, 1090, Vienna, Austria
| | - Petrine Wellendorph
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, 2 Universitetsparken, 2100, Copenhagen, Denmark.
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Zhang Y, Dong HT, Duan L, Niu L, Yuan GQ, Dai JQ, Hou BR, Pan YW. HDAC4 gene silencing alleviates epilepsy by inhibition of GABA in a rat model. Neuropsychiatr Dis Treat 2019; 15:405-416. [PMID: 30787615 PMCID: PMC6366349 DOI: 10.2147/ndt.s181669] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVES Despite the availability of effective antiepileptic drugs, epileptic patients still suffer from intractable seizures and adverse events. Better control of both seizures and fewer side effects is needed in order to enhance the patient's quality of life. We performed the present study with an attempt to explore the effect that HDAC4 gene silencing would have on epilepsy simulated by model rats. Furthermore, the study made additional analysis on the relativity of the HDAC4 gene in regard to its relationship with the gamma-aminobutyric acid (GABA) signaling pathway. MATERIALS AND METHODS Tremor rats were prepared in order to establish the epilepsy model. The rats would go on to be treated with si-HDAC4 in order to identify roles of the HDAC4 in levels of GABAARα1, GABAARα4, GAD65, GAT-1, and GAT-3. Finally, both electroencephalogram behavior and cognitive function of the rats following the treatment of si-HDAC4 were observed. RESULTS Levels of the GABAARα1 and GABAARα4 showed an evident increase, while GAD65, GAT-1, and GAT-3 displayed a decline in the epilepsy rats treated with the aforementioned si-HDAC4 when compared with the epilepsy rats. After injection of si-HDAC4, the epilepsy rats presented with a reduction in seizure degree, latency and duration of seizure, amount of scattered epileptic waves, and occurrence of epilepsy, with an improvement in their cognitive function. CONCLUSION The study highlighted the role that HDAC4 gene silencing played in easing the cases of epilepsy found in the model rats. This was shown to have occurred through the upregulation of both GABAARα1 and GABAARα4 levels, as well as in the downregulation of GAD65, GAT-1, and GAT-3 levels. The evidence provided shows that the HDAC4 gene is likely to present as a new objective in further experimentation in the treatment of epilepsy.
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Affiliation(s)
- Yinian Zhang
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Hua-Teng Dong
- Department of Pediatric Neurology, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou 730050, People's Republic of China
| | - Lei Duan
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Liang Niu
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Guo-Qiang Yuan
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Jun-Qiang Dai
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Bo-Ru Hou
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
| | - Ya-Wen Pan
- Department of Neurosurgery and Laboratory of Neurosurgery, Lanzhou University Second Hospital, Lanzhou 730030, People's Republic of China, .,Institute of Neurology, Lanzhou University, Lanzhou 730030, People's Republic of China,
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Suemasa A, Watanabe M, Kobayashi T, Suzuki H, Fukuda H, Minami M, Shuto S. Design and synthesis of cyclopropane-based conformationally restricted GABA analogues as selective inhibitors for betaine/GABA transporter 1. Bioorg Med Chem Lett 2018; 28:3395-3399. [DOI: 10.1016/j.bmcl.2018.08.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 08/25/2018] [Accepted: 08/25/2018] [Indexed: 12/26/2022]
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14
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Hauke TJ, Wein T, Höfner G, Wanner KT. Novel Allosteric Ligands of γ-Aminobutyric Acid Transporter 1 (GAT1) by MS Based Screening of Pseudostatic Hydrazone Libraries. J Med Chem 2018; 61:10310-10332. [DOI: 10.1021/acs.jmedchem.8b01602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Tobias J. Hauke
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Thomas Wein
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Georg Höfner
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
| | - Klaus T. Wanner
- Department of Pharmacy—Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Munich, Germany
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Al-Khawaja A, Haugaard AS, Marek A, Löffler R, Thiesen L, Santiveri M, Damgaard M, Bundgaard C, Frølund B, Wellendorph P. Pharmacological Characterization of [ 3H]ATPCA as a Substrate for Studying the Functional Role of the Betaine/GABA Transporter 1 and the Creatine Transporter. ACS Chem Neurosci 2018; 9:545-554. [PMID: 29131576 DOI: 10.1021/acschemneuro.7b00351] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The betaine/γ-aminobutyric acid (GABA) transporter 1 (BGT1) is one of the four GABA transporters (GATs) involved in the termination of GABAergic neurotransmission. Although suggested to be implicated in seizure management, the exact functional importance of BGT1 in the brain is still elusive. This is partly owing to the lack of potent and selective pharmacological tool compounds that can be used to probe its function. We previously reported the identification of 2-amino-1,4,5,6-tetrahydropyrimidine-5-carboxylic acid (ATPCA), a selective substrate for BGT1 over GAT1/GAT3, but also an agonist for GABAA receptors. With the aim of providing new functional insight into BGT1, we here present the synthesis and pharmacological characterization of the tritiated analogue, [3H]ATPCA. Using traditional uptake assays at recombinant transporters expressed in cell lines, [3H]ATPCA displayed a striking selectivity for BGT1 among the four GATs ( Km and Vmax values of 21 μM and 3.6 nmol ATPCA/(min × mg protein), respectively), but was also found to be a substrate for the creatine transporter (CreaT). In experiments with mouse cortical cell cultures, we observed a Na+-dependent [3H]ATPCA uptake in neurons, but not in astrocytes. The neuronal uptake could be inhibited by GABA, ATPCA, and a noncompetitive BGT1-selective inhibitor, indicating functional BGT1 in neurons. In conclusion, we report [3H]ATPCA as a novel radioactive substrate for both BGT1 and CreaT. The dual activity of the radioligand makes it most suitable for use in recombinant studies.
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Affiliation(s)
- Anas Al-Khawaja
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Anne S. Haugaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Ales Marek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam 542/2, 16610 Prague 6, Czech Republic
| | - Rebekka Löffler
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Louise Thiesen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mònica Santiveri
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Maria Damgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | | | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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16
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Jørgensen L, Al-Khawaja A, Kickinger S, Vogensen SB, Skovgaard-Petersen J, Rosenthal E, Borkar N, Löffler R, Madsen KK, Bräuner-Osborne H, Schousboe A, Ecker GF, Wellendorph P, Clausen RP. Structure–Activity Relationship, Pharmacological Characterization, and Molecular Modeling of Noncompetitive Inhibitors of the Betaine/γ-Aminobutyric Acid Transporter 1 (BGT1). J Med Chem 2017; 60:8834-8846. [DOI: 10.1021/acs.jmedchem.7b00924] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Lars Jørgensen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Anas Al-Khawaja
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Stefanie Kickinger
- Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Stine B. Vogensen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jonas Skovgaard-Petersen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Emil Rosenthal
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Nrupa Borkar
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rebekka Löffler
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Karsten K. Madsen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Gerhard F. Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Petrine Wellendorph
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rasmus P. Clausen
- Department of Drug
Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
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Wellendorph P, Jacobsen J, Skovgaard-Petersen J, Jurik A, Vogensen SB, Ecker G, Schousboe A, Krogsgaard-Larsen P, Clausen RP. γ-Aminobutyric Acid and Glycine Neurotransmitter Transporters. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2017. [DOI: 10.1002/9783527679430.ch4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Petrine Wellendorph
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Julie Jacobsen
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Jonas Skovgaard-Petersen
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Andreas Jurik
- University of Vienna; Department of Pharmaceutical Chemistry; Althanstrasse 14, A-1090 Vienna Austria
| | - Stine B. Vogensen
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Gerhard Ecker
- University of Vienna; Department of Pharmaceutical Chemistry; Althanstrasse 14, A-1090 Vienna Austria
| | - Arne Schousboe
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Povl Krogsgaard-Larsen
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
| | - Rasmus P. Clausen
- University of Copenhagen; Faculty of Health and Medical Sciences, Department of Drug Design and Pharmacology; Universitetsparken 2, DK-2100 Copenhagen Denmark
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18
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Damgaard M, Haugaard AS, Kickinger S, Al-Khawaja A, Lie MEK, Ecker GF, Clausen RP, Frølund B. Development of Non-GAT1-Selective Inhibitors: Challenges and Achievements. ADVANCES IN NEUROBIOLOGY 2017; 16:315-332. [DOI: 10.1007/978-3-319-55769-4_16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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Astrocytic GABA Transporters: Pharmacological Properties and Targets for Antiepileptic Drugs. ADVANCES IN NEUROBIOLOGY 2017; 16:283-296. [PMID: 28828616 DOI: 10.1007/978-3-319-55769-4_14] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Inactivation of GABA-mediated neurotransmission is achieved by high-affinity transporters located at both GABAergic neurons and the surrounding astrocytes. Early studies of the pharmacological properties of neuronal and glial GABA transporters suggested that different types of transporters might be expressed in the two cell types, and such a scenario was confirmed by the cloning of four distinctly different GABA transporters from a number of different species. These GABA-transport entities have been extensively characterized using a large number of GABA analogues of restricted conformation, and several of these compounds have been shown to exhibit pronounced anticonvulsant activity in a variety of animal seizure models. As proof of concept of the validity of this drug development approach, one GABA-transport inhibitor, tiagabine, has been developed as a clinically active antiepileptic drug. This review provides a detailed account of efforts to design new subtype-selective GABA-transport inhibitors aiming at identifying novel antiepileptic drug candidates.
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Glial GABA Transporters as Modulators of Inhibitory Signalling in Epilepsy and Stroke. ADVANCES IN NEUROBIOLOGY 2017; 16:137-167. [PMID: 28828609 DOI: 10.1007/978-3-319-55769-4_7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Imbalances in GABA-mediated tonic inhibition are involved in several pathophysiological conditions. A classical way of controlling tonic inhibition is through pharmacological intervention with extrasynaptic GABAA receptors that sense ambient GABA and mediate a persistent GABAergic conductance. An increase in tonic inhibition may, however, also be obtained indirectly by inhibiting glial GABA transporters (GATs). These are sodium-coupled membrane transport proteins that normally act to terminate GABA neurotransmitter action by taking up GABA into surrounding astrocytes. The aim of the review is to provide an overview of glial GATs in regulating tonic inhibition, especially in epilepsy and stroke. This entails a comprehensive summary of changes known to occur in GAT expression levels and signalling following epileptic and ischemic insults. Further, we discuss the accumulating pharmacological evidence for targeting GATs in these diseases.
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21
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Damgaard M, Al-Khawaja A, Vogensen SB, Jurik A, Sijm M, Lie MEK, Bæk MI, Rosenthal E, Jensen AA, Ecker GF, Frølund B, Wellendorph P, Clausen RP. Identification of the First Highly Subtype-Selective Inhibitor of Human GABA Transporter GAT3. ACS Chem Neurosci 2015; 6:1591-9. [PMID: 26154082 DOI: 10.1021/acschemneuro.5b00150] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Screening a library of small-molecule compounds using a cell line expressing human GABA transporter 3 (hGAT3) in a [(3)H]GABA uptake assay identified isatin derivatives as a new class of hGAT3 inhibitors. A subsequent structure-activity relationship (SAR) study led to the identification of hGAT3-selective inhibitors (i.e., compounds 20 and 34) that were superior to the reference hGAT3 inhibitor, (S)-SNAP-5114, in terms of potency (low micromolar IC50 values) and selectivity (>30-fold selective for hGAT3 over hGAT1/hGAT2/hBGT1). Further pharmacological characterization of compound 20 (5-(thiophen-2-yl)indoline-2,3-dione) revealed a noncompetitive mode of inhibition at hGAT3. This suggests that this compound class, which has no structural resemblance to GABA, has a binding site different from the substrate, GABA. This was supported by a molecular modeling study that suggested a unique binding site that matched the observed selectivity, inhibition kinetics, and SAR of the compound series. These compounds are the most potent GAT3 inhibitors reported to date that provide selectivity for GAT3 over other GABA transporter subtypes.
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Affiliation(s)
| | | | | | - Andreas Jurik
- Department
of Pharmaceutical Chemistry, University of Vienna, Althanstrasse
14, A-1090 Vienna, Austria
| | | | | | | | | | | | - Gerhard F. Ecker
- Department
of Pharmaceutical Chemistry, University of Vienna, Althanstrasse
14, A-1090 Vienna, Austria
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Schmitt S, Höfner G, Wanner KT. Application of MS Transport Assays to the Four Human γ-Aminobutyric Acid Transporters. ChemMedChem 2015. [DOI: 10.1002/cmdc.201500254] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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The effect of GABA transporter 1 (GAT1) inhibitor, tiagabine, on scopolamine-induced memory impairments in mice. Pharmacol Rep 2015; 67:1155-62. [PMID: 26481535 DOI: 10.1016/j.pharep.2015.04.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 12/31/2022]
Abstract
BACKGROUND GABAergic neurotransmission is involved in long-term potentiation, a neurophysiological basis for learning and memory. On the other hand, GABA-enhancing drugs may impair memory and learning in humans and animals. The present study aims at investigating the effect of GAT1 inhibitor tiagabine on memory and learning. METHODS Albino Swiss (CD-1) and C57BL/6J mice were used in the passive avoidance (PA), Morris water maze (MWM) and radial arm water maze (RAWM) tasks. Scopolamine (1mg/kg ip) was applied to induce cognitive deficits. RESULTS In the retention trial of PA scopolamine reduced step-through latency as compared to vehicle-treated mice, and pretreatment with tiagabine did not have any influence on this effect. In MWM the results obtained for vehicle-treated mice, scopolamine-treated group and combined scopolamine+tiagabine-treated mice revealed variable learning abilities in these groups. Tiagabine did not impair learning in the acquisition trial. In RAWM on day 1 scopolamine-treated group made nearly two-fold more errors than vehicle-treated mice and mice that received combined scopolamine and tiagabine. Learning abilities in the latter group were similar to those of vehicle-treated mice in the corresponding trial block on day 1, except for the last trial block, during which tiagabine+scopolamine-injected mice made more errors than control mice and the scopolamine-treated group. In all groups a complete reversal of memory deficits was observed in the last trial block of day 2. CONCLUSIONS The lack of negative influence of tiagabine on cognitive functions in animals with scopolamine-induced memory impairments may be relevant for patients treated with this drug.
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Schmitt S, Höfner G, Wanner KT. MS Transport Assays for γ-Aminobutyric Acid Transporters—An Efficient Alternative for Radiometric Assays. Anal Chem 2014; 86:7575-83. [DOI: 10.1021/ac501366r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Sebastian Schmitt
- Department of Pharmacy—Center
for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstraße
7, 81377 München, Germany
| | - Georg Höfner
- Department of Pharmacy—Center
for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstraße
7, 81377 München, Germany
| | - Klaus T. Wanner
- Department of Pharmacy—Center
for Drug Research, Ludwig-Maximilians-Universität München, Butenandtstraße
7, 81377 München, Germany
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25
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Pharmacological identification of a guanidine-containing β-alanine analogue with low micromolar potency and selectivity for the betaine/GABA transporter 1 (BGT1). Neurochem Res 2014; 39:1988-96. [PMID: 24852577 DOI: 10.1007/s11064-014-1336-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/08/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
Abstract
The γ-aminobutyric acid (GABA) transporters (GATs) are key membrane transporter proteins involved in the termination of GABAergic signaling at synapses in the mammalian brain and proposed drug targets in neurological disorders such as epilepsy. To date, four different GAT subtypes have been identified: GAT1, GAT2, GAT3 and the betaine/GABA transporter 1 (BGT1). Owing to the lack of potent and subtype selective inhibitors of the non-GAT1 GABA transporters, the physiological role and therapeutic potential of these transporters remain to be fully understood. Based on bioisosteric replacement of the amino group in β-alanine or GABA, a series of compounds was generated, and their pharmacological activity assessed at human GAT subtypes. Using a cell-based [(3)H]GABA uptake assay, several selective inhibitors at human BGT1 were identified. The guanidine-containing compound 9 (2-amino-1,4,5,6-tetrahydropyrimidine-5-carboxylic acid hydrochloride) displayed more than 250 times greater potency than the parent compound β-alanine at BGT1 and is thus the most potent inhibitor reported to date for this subtype (IC50 value of 2.5 µM). In addition, compound 9 displayed about 400, 16 and 40 times lower inhibitory potency at GAT1, GAT2 and GAT3, respectively. Compound 9 was shown to be a substrate for BGT1 and to have an overall similar pharmacological profile at the mouse orthologue. Compound 9 constitutes an interesting pharmacological tool for specifically investigating the cellular pharmacology of BGT1 and is the first small-molecule substrate identified with such a high selectivity for BGT1 over the three other GAT subtypes.
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Hiramatsu M. [Functional role for GABA transporters in the CNS]. Nihon Yakurigaku Zasshi 2014; 143:187-192. [PMID: 24717607 DOI: 10.1254/fpj.143.187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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Schousboe A, Madsen KK, Barker-Haliski ML, White HS. The GABA Synapse as a Target for Antiepileptic Drugs: A Historical Overview Focused on GABA Transporters. Neurochem Res 2014; 39:1980-7. [DOI: 10.1007/s11064-014-1263-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 01/18/2023]
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