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Dual Role for Astroglial Copper-Assisted Polyamine Metabolism during Intense Network Activity. Biomolecules 2021; 11:biom11040604. [PMID: 33921742 PMCID: PMC8073386 DOI: 10.3390/biom11040604] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 04/09/2021] [Accepted: 04/14/2021] [Indexed: 12/29/2022] Open
Abstract
Astrocytes serve essential roles in human brain function and diseases. Growing evidence indicates that astrocytes are central players of the feedback modulation of excitatory Glu signalling during epileptiform activity via Glu-GABA exchange. The underlying mechanism results in the increase of tonic inhibition by reverse operation of the astroglial GABA transporter, induced by Glu-Na+ symport. GABA, released from astrocytes, is synthesized from the polyamine (PA) putrescine and this process involves copper amino oxidase. Through this pathway, putrescine can be considered as an important source of inhibitory signaling that counterbalances epileptic discharges. Putrescine, however, is also a precursor for spermine that is known to enhance gap junction channel communication and, consequently, supports long-range Ca2+ signaling and contributes to spreading of excitatory activity through the astrocytic syncytium. Recently, we presented the possibility of neuron-glia redox coupling through copper (Cu+/Cu2+) signaling and oxidative putrescine catabolism. In the current work, we explore whether the Cu+/Cu2+ homeostasis is involved in astrocytic control on neuronal excitability by regulating PA catabolism. We provide supporting experimental data underlying this hypothesis. We show that the blockade of copper transporter (CTR1) by AgNO3 (3.6 µM) prevents GABA transporter-mediated tonic inhibitory currents, indicating causal relationship between copper (Cu+/Cu2+) uptake and the catabolism of putrescine to GABA in astrocytes. In addition, we show that MnCl2 (20 μM), an inhibitor of the divalent metal transporter DMT1, also prevents the astrocytic Glu-GABA exchange. Furthermore, we observed that facilitation of copper uptake by added CuCl2 (2 µM) boosts tonic inhibitory currents. These findings corroborate the hypothesis that modulation of neuron-glia coupling by copper uptake drives putrescine → GABA transformation, which leads to subsequent Glu-GABA exchange and tonic inhibition. Findings may in turn highlight the potential role of copper signaling in fine-tuning the activity of the tripartite synapse.
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Héja L, Simon Á, Szabó Z, Kardos J. Feedback adaptation of synaptic excitability via Glu:Na + symport driven astrocytic GABA and Gln release. Neuropharmacology 2019; 161:107629. [PMID: 31103619 DOI: 10.1016/j.neuropharm.2019.05.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 03/30/2019] [Accepted: 05/07/2019] [Indexed: 02/08/2023]
Abstract
Glutamatergic transmission composed of the arriving of action potential at the axon terminal, fast vesicular Glu release, postsynaptic Glu receptor activation, astrocytic Glu clearance and Glu→Gln shuttle is an abundantly investigated phenomenon. Despite its essential role, however, much less is known about the consequences of the mechanistic connotations of Glu:Na+ symport. Due to the coupled Na+ transport, Glu uptake results in significantly elevated intracellular astrocytic [Na+] that markedly alters the driving force of other Na+-coupled astrocytic transporters. The resulting GABA and Gln release by reverse transport through the respective GAT-3 and SNAT3 transporters help to re-establish the physiological Na+ homeostasis without ATP dissipation and consequently leads to enhanced tonic inhibition and replenishment of axonal glutamate pool. Here, we place this emerging astrocytic adjustment of synaptic excitability into the centre of future perspectives. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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Affiliation(s)
- László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, 1117, Budapest, Hungary
| | - Ágnes Simon
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, 1117, Budapest, Hungary
| | - Zsolt Szabó
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, 1117, Budapest, Hungary
| | - Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, 1117, Budapest, Hungary.
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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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Ma X, Lubin H, Ioja E, Kékesi O, Simon Á, Apáti Á, Orbán TI, Héja L, Kardos J, Markó IE. Straightforward and effective synthesis of γ-aminobutyric acid transporter subtype 2-selective acyl-substituted azaspiro[4.5]decanes. Bioorg Med Chem Lett 2015; 26:417-423. [PMID: 26706177 DOI: 10.1016/j.bmcl.2015.11.100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 11/26/2015] [Accepted: 11/27/2015] [Indexed: 10/22/2022]
Abstract
Supply of major metabolites such as γ-aminobutyric acid (GABA), β-alanine and taurine is an essential instrument that shapes signalling, proper cell functioning and survival in the brain and peripheral organs. This background motivates the synthesis of novel classes of compounds regulating their selective transport through various fluid-organ barriers via the low-affinity γ-aminobutyric acid (GABA) transporter subtype 2 (GAT2). Natural and synthetic spirocyclic compounds or therapeutics with a range of structures and biological activity are increasingly recognised in this regard. Based on pre-validated GABA transport activity, straightforward and efficient synthesis method was developed to provide an azaspiro[4.5]decane scaffold, holding a variety of charge, substituent and 3D constrain of spirocyclic amine. Investigation of the azaspiro[4.5]decane scaffold in cell lines expressing the four GABA transporter subtypes led to the discovery of a subclass of a GAT2-selective compounds with acyl-substituted azaspiro[4.5]decane core.
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Affiliation(s)
- Xiaofeng Ma
- Organic and Medicinal Chemistry Laboratories, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Hodney Lubin
- Organic and Medicinal Chemistry Laboratories, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Enikő Ioja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - Orsolya Kékesi
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - Ágnes Simon
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - Ágota Apáti
- Laboratory of Molecular Cell Biology, Institute of Enzimology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - Tamás I Orbán
- Biomembrane Research Group, Institute of Enzimology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary
| | - Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, H-1117 Budapest, Hungary.
| | - István E Markó
- Organic and Medicinal Chemistry Laboratories, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
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Abstract
We delineate perspectives for the design and discovery of antiepileptic drugs (AEDs) with fewer side effects by focusing on astroglial modulation of spatiotemporal seizure dynamics. It is now recognized that the major inhibitory neurotransmitter of the brain, γ-aminobutyric acid (GABA), can be released through the reversal of astroglial GABA transporters. Synaptic spillover and subsequent glutamate (Glu) uptake in neighboring astrocytes evoke replacement of extracellular Glu for GABA, driving neurons away from the seizure threshold. Attenuation of synaptic signaling by this negative feedback through the interplay of Glu and GABA transporters of adjacent astroglia can result in shortened seizures. By contrast, long-range activation of astroglia through gap junctions may promote recurrent seizures on the model of pharmacoresistant temporal lobe epilepsy. From their first detection to our current understanding, we identify various targets that shape both short- and long-range neuro-astroglia coupling, as these are manifest in epilepsy phenomena and in the associated research promotions of AED.
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Affiliation(s)
- Julianna Kardos
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
| | - Zsolt Szabó
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
| | - László Héja
- Functional Pharmacology Research Group, Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1117 Budapest, Hungary
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Simon Á, Bencsura Á, Héja L, Magyar C, Kardos J. Sodium-assisted formation of binding and traverse conformations of the substrate in a neurotransmitter sodium symporter model. Curr Drug Discov Technol 2015; 11:227-33. [PMID: 25138914 PMCID: PMC4443782 DOI: 10.2174/1570163811666140812110735] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 07/31/2014] [Accepted: 07/31/2014] [Indexed: 11/22/2022]
Abstract
Therapeutics designed to increase synaptic neurotransmitter levels by inhibiting neurotransmitter sodium symporters (NSSs) classify a strategic approach to treat brain disorders such as depression or epilepsy, however, the critical elementary steps that couple downhill flux of sodium to uphill transport of neurotransmitter are not distinguished as yet. Here we present modelling of NSS member neuronal GAT1 with the substrate γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter. GABA binding is simulated with the occluded conformation of GAT1 homodimer in an explicit lipid/water environment. Simulations performed in the 1-10 ns range of time elucidated persistent formation of halfextended minor and H-bridged major GABA conformations, referred to as binding and traverse conformations, respectively. The traverse GABA conformation was further stabilized by GAT1-bound Na(+)(1). We also observed Na(+)(1) translocation to GAT1-bound Cl(-) as well as the appearance of water molecules at GABA and GAT1-bound Na(+)(2), conjecturing causality. Scaling dynamics suggest that the traverse GABA conformation may be valid for developing substrate inhibitors with high efficacy. The potential for this finding is significant with impact not only in pharmacology but wherever understanding of the mechanism of neurotransmitter uptake is valuable.
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Affiliation(s)
| | | | | | | | - Julianna Kardos
- Institute of Molecular Pharmacology, Research Centre for Natural Sciences, PO Box 17, H-1525 Budapest, Hungary.
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Jurik A, Zdrazil B, Holy M, Stockner T, Sitte HH, Ecker GF. A binding mode hypothesis of tiagabine confirms liothyronine effect on γ-aminobutyric acid transporter 1 (GAT1). J Med Chem 2015; 58:2149-58. [PMID: 25679268 PMCID: PMC4360375 DOI: 10.1021/jm5015428] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
Elevating
GABA levels in the synaptic cleft by inhibiting its reuptake
carrier GAT1 is an established approach for the treatment of CNS disorders
like epilepsy. With the increasing availability of crystal structures
of transmembrane transporters, structure-based approaches to elucidate
the molecular basis of ligand–transporter interaction also
become feasible. Experimental data guided docking of derivatives of
the GAT1 inhibitor tiagabine into a protein homology model of GAT1
allowed derivation of a common binding mode for this class of inhibitors
that is able to account for the distinct structure–activity
relationship pattern of the data set. Translating essential binding
features into a pharmacophore model followed by in silico screening
of the DrugBank identified liothyronine as a drug potentially exerting
a similar effect on GAT1. Experimental testing further confirmed the
GAT1 inhibiting properties of this thyroid hormone.
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Affiliation(s)
- Andreas Jurik
- University of Vienna , Department of Pharmaceutical Chemistry, Division of Drug Design and Medicinal Chemistry, Althanstraße 14, 1090 Vienna, Austria
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Lin HJ, Huang YC, Lin JM, Liao WL, Wu JY, Chen CH, Chou YC, Chen LA, Lin CJ, Tsai FJ. Novel susceptibility genes associated with diabetic cataract in a Taiwanese population. Ophthalmic Genet 2012; 34:35-42. [PMID: 23137000 DOI: 10.3109/13816810.2012.736590] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE To identify genetic variants that predispose to type 2 diabetes (T2D) with cataract. PATIENTS AND METHODS Genome-wide association study (GWAS) of T2D patients with cataract, as graded by Lens Opacities Classification System (LOCS). A total of 109 T2D patients with cataract score equal to or above 10 designated as the study group, 649 T2D patients with cataract score equal to or below 3 as the control group. Single nucleotide polymorphisms (SNPs) with p-values < 10(-5) were considered to be putatively associated with the diabetic cataract. RESULTS Fifteen SNPs were found to be putatively associated with diabetic cataract. These variants were located near the following genes: PPARD, CCDC102A, GBA3, NEDD9, GABRR1/2, RPS6KA2, tcag7.1163, TAC1, GALNTL1 and KIAA1671. We defined haplotype 1 to haplotype 4 from the alternative alleles of related polymorphisms. Distribution of haplotype 2 on chromosome 4 and haplotype 4 on chromosome 7 revealed significant differences (OR = 1.86 and 1.69, respectively; 95% confidence interval were 1.26-2.76 and 1.23-2.31, respectively). CONCLUSIONS The 15 loci coded on chromosomes 4, 6, 7, 14, 16 and 22 were associated with diabetic cataract. Gene functions are either with mechanisms of regulating blood sugar or formation of cataract. High linkage disequilibrium appeared on chromosome 4p15.31 and chromosome 7q21.3.
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Affiliation(s)
- Hui-Ju Lin
- Department of Medical Research, China Medical University Hospital, Taichung, Taiwan
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Inhibitory action of antidepressants on mouse Betaine/GABA transporter (BGT1) heterologously expressed in cell cultures. Int J Mol Sci 2012; 13:2578-2589. [PMID: 22489112 PMCID: PMC3317675 DOI: 10.3390/ijms13032578] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 01/28/2012] [Accepted: 02/17/2012] [Indexed: 11/23/2022] Open
Abstract
Betaine/γ-aminobutyric acid (GABA) transporter (BGT1, SLC6A12) is a member of the Na+- and Cl−-dependent neurotransmitter transporter gene family with a homology to the GABA transporters (GATs), GAT1 (SLC6A1), GAT2 (SLC6A13) and GAT3 (SLC6A11) (HUGO nomenclature). Since antidepressants have been reported to inhibit GABA uptake, we examined those effects on mouse BGT1 (mBGT1) in comparison with other mouse GAT (mGAT) subtypes in the heterologously expressed cell cultures. All antidepressants tested here inhibited the [3H]GABA uptake through mBGT1 and mGATs in a rank order of potency with mBGT1 > mGAT1-3. Kinetic analyses for maprotilline, mianserine and trimipramine revealed that they inhibited mBGT1 and mGAT1 noncompetitively, except that mianserine competitively inhibited mBGT1. These results provided a clue to investigate the structure-function relationship of mBGT1 using antidepressants as a tool, leading to the identification of potential candidates for selective and specific inhibitors of mBGT1.
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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 586] [Impact Index Per Article: 45.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Abstract
Since it was first reported approximately 40 years ago that putative amino acid neurotransmitters, including GABA, would likely be inactivated by synaptic high-affinity transporters, there has been an exponential increase in interest in delineating the pharmacological characteristics of these transporters. During the 1980s and 1990s a large series of publications was devoted to a detailed characterization of neuronal and astroglial GABA transporters demonstrating important differences between these, a notion that turned out to be of relevance for the development of anticonvulsants targeting GABA transporters. The cloning era, leading to the identification of four proteins capable of transporting GABA across plasma membranes, has further boosted this research. Ultimately the clinically active antiepileptic drug, tiagabine, was developed and it was established that its mechanism of action involved inhibition of the GABA transporter-1 (GAT1). Current and future research is directed towards a better understanding of how extrasynaptic GABA receptors may be regulated via manipulation of extrasynaptic GABA levels, possibly involving extrasynaptic GABA transporters, most likely non-GAT1 transporters.
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