1
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Ji W, Miao A, Liang K, Liu J, Qi Y, Zhou Y, Duan X, Sun J, Lai L, Wu JX. Substrate binding and inhibition mechanism of norepinephrine transporter. Nature 2024; 633:473-479. [PMID: 39143211 DOI: 10.1038/s41586-024-07810-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 07/10/2024] [Indexed: 08/16/2024]
Abstract
Norepinephrine transporter (NET; encoded by SLC6A2) reuptakes the majority of the released noradrenaline back to the presynaptic terminals, thereby affecting the synaptic noradrenaline level1. Genetic mutations and dysregulation of NET are associated with a spectrum of neurological conditions in humans, making NET an important therapeutic target1. However, the structure and mechanism of NET remain unclear. Here we provide cryogenic electron microscopy structures of the human NET (hNET) in three functional states-the apo state, and in states bound to the substrate meta-iodobenzylguanidine (MIBG) or the orthosteric inhibitor radafaxine. These structures were captured in an inward-facing conformation, with a tightly sealed extracellular gate and an open intracellular gate. The substrate MIBG binds at the centre of hNET. Radafaxine also occupies the substrate-binding site and might block the structural transition of hNET for inhibition. These structures provide insights into the mechanism of substrate recognition and orthosteric inhibition of hNET.
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Affiliation(s)
- Wenming Ji
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Anran Miao
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Kai Liang
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Jiameng Liu
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Yuhan Qi
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Yue Zhou
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China
| | - Xinli Duan
- Beijing Jingtai Technology, Beijing, P. R. China
| | - Jixue Sun
- Beijing Jingtai Technology, Beijing, P. R. China
| | - Lipeng Lai
- Beijing Jingtai Technology, Beijing, P. R. China
| | - Jing-Xiang Wu
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, P. R. China.
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2
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Bröer A, Hu Z, Kukułowicz J, Yadav A, Zhang T, Dai L, Bajda M, Yan R, Bröer S. Cryo-EM structure of ACE2-SIT1 in complex with tiagabine. J Biol Chem 2024; 300:107687. [PMID: 39159813 DOI: 10.1016/j.jbc.2024.107687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 08/03/2024] [Accepted: 08/07/2024] [Indexed: 08/21/2024] Open
Abstract
The pharmacology of amino acid transporters in the SLC6 family is poorly developed compared to that of the neurotransmitter transporters. To identify new inhibitors of the proline transporter SIT1 (SLC6A20), its expression in Xenopus laevis oocytes was optimized. Trafficking of SIT1 was augmented by co-expression of angiotensin-converting enzyme 2 (ACE2) in oocytes but there was no strict requirement for co-expression of ACE2. A pharmacophore-guided screen identified tiagabine as a potent non-competitive inhibitor of SIT1. To understand its binding mode, we determined the cryo-electron microscopy (cryo-EM) structure of ACE2-SIT1 bound with tiagabine. The inhibitor binds close to the orthosteric proline binding site, but due to its size extends into the cytosolic vestibule. This causes the transporter to adopt an inward-open conformation, in which the intracellular gate is blocked. This study provides the first structural insight into inhibition of SIT1 and generates tools for a better understanding of the ACE2-SIT1 complex. These findings may have significance for SARS-CoV-2 binding to its receptor ACE2 in human lung alveolar cells where SIT1 and ACE2 are functionally expressed.
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Affiliation(s)
- Angelika Bröer
- Research School of Biology, Australian National University, Canberra, Australia
| | - Ziwei Hu
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Jędrzej Kukułowicz
- Department of Physicochemical Drug Analysis, Faculty of Pharmacy, Jagiellonian University Medical College, Cracow, Poland
| | - Aditya Yadav
- Research School of Biology, Australian National University, Canberra, Australia
| | - Ting Zhang
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Lu Dai
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Marek Bajda
- Department of Physicochemical Drug Analysis, Faculty of Pharmacy, Jagiellonian University Medical College, Cracow, Poland
| | - Renhong Yan
- Department of Biochemistry, Key University Laboratory of Metabolism and Health of Guangdong, School of Medicine, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, Guangdong, China.
| | - Stefan Bröer
- Research School of Biology, Australian National University, Canberra, Australia.
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3
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Nielsen JC, Salomon K, Kalenderoglou IE, Bargmeyer S, Pape T, Shahsavar A, Loland CJ. Structure of the human dopamine transporter in complex with cocaine. Nature 2024; 632:678-685. [PMID: 39112703 DOI: 10.1038/s41586-024-07804-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 07/09/2024] [Indexed: 08/16/2024]
Abstract
The dopamine transporter (DAT) is crucial for regulating dopamine signalling and is the prime mediator for the rewarding and addictive effects of cocaine1. As part of the neurotransmitter sodium symporter family, DAT uses the Na+ gradient across cell membranes to transport dopamine against its chemical gradient2. The transport mechanism involves both intra- and extracellular gates that control substrate access to a central site. However, the molecular intricacies of this process and the inhibitory mechanism of cocaine have remained unclear. Here, we present the molecular structure of human DAT in complex with cocaine at a resolution of 2.66 Å. Our findings reveal that DAT adopts the expected LeuT-fold, posing in an outward-open conformation with cocaine bound at the central (S1) site. Notably, while an Na+ occupies the second Na+ site (Na2), the Na1 site seems to be vacant, with the side chain of Asn82 occupying the presumed Na+ space. This structural insight elucidates the mechanism for the cocaine inhibition of human DAT and deepens our understanding of neurotransmitter transport. By shedding light on the molecular underpinnings of how cocaine acts, our study lays a foundation for the development of targeted medications to combat addiction.
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Affiliation(s)
- Jeppe C Nielsen
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristine Salomon
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Iris E Kalenderoglou
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sarah Bargmeyer
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tillmann Pape
- Structural Molecular Biology Group, Protein Structure & Function Program, Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Core Facility for Integrated Microscopy (CFIM), Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Azadeh Shahsavar
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Claus J Loland
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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4
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Tan J, Xiao Y, Kong F, Zhang X, Xu H, Zhu A, Liu Y, Lei J, Tian B, Yuan Y, Yan C. Molecular basis of human noradrenaline transporter reuptake and inhibition. Nature 2024; 632:921-929. [PMID: 39048818 DOI: 10.1038/s41586-024-07719-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 06/14/2024] [Indexed: 07/27/2024]
Abstract
Noradrenaline, also known as norepinephrine, has a wide range of activities and effects on most brain cell types1. Its reuptake from the synaptic cleft heavily relies on the noradrenaline transporter (NET) located in the presynaptic membrane2. Here we report the cryo-electron microscopy (cryo-EM) structures of the human NET in both its apo state and when bound to substrates or antidepressant drugs, with resolutions ranging from 2.5 Å to 3.5 Å. The two substrates, noradrenaline and dopamine, display a similar binding mode within the central substrate binding site (S1) and within a newly identified extracellular allosteric site (S2). Four distinct antidepressants, namely, atomoxetine, desipramine, bupropion and escitalopram, occupy the S1 site to obstruct substrate transport in distinct conformations. Moreover, a potassium ion was observed within sodium-binding site 1 in the structure of the NET bound to desipramine under the KCl condition. Complemented by structural-guided biochemical analyses, our studies reveal the mechanism of substrate recognition, the alternating access of NET, and elucidate the mode of action of the four antidepressants.
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Affiliation(s)
- Jiaxin Tan
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yuan Xiao
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Fang Kong
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xiaochun Zhang
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Hanwen Xu
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Angqi Zhu
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yiming Liu
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jianlin Lei
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Boxue Tian
- School of Pharmaceutical Sciences, Tsinghua University, Beijing, China
| | - Yafei Yuan
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China.
| | - Chuangye Yan
- Beijing Frontier Research Center for Biological Structure, State Key Laboratory of Membrane Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China.
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5
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Li Y, Wang X, Meng Y, Hu T, Zhao J, Li R, Bai Q, Yuan P, Han J, Hao K, Wei Y, Qiu Y, Li N, Zhao Y. Dopamine reuptake and inhibitory mechanisms in human dopamine transporter. Nature 2024; 632:686-694. [PMID: 39112701 DOI: 10.1038/s41586-024-07796-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 07/05/2024] [Indexed: 08/16/2024]
Abstract
The dopamine transporter has a crucial role in regulation of dopaminergic neurotransmission by uptake of dopamine into neurons and contributes to the abuse potential of psychomotor stimulants1-3. Despite decades of study, the structure, substrate binding, conformational transitions and drug-binding poses of human dopamine transporter remain unknown. Here we report structures of the human dopamine transporter in its apo state, and in complex with the substrate dopamine, the attention deficit hyperactivity disorder drug methylphenidate, and the dopamine-uptake inhibitors GBR12909 and benztropine. The dopamine-bound structure in the occluded state precisely illustrates the binding position of dopamine and associated ions. The structures bound to drugs are captured in outward-facing or inward-facing states, illuminating distinct binding modes and conformational transitions during substrate transport. Unlike the outward-facing state, which is stabilized by cocaine, GBR12909 and benztropine stabilize the dopamine transporter in the inward-facing state, revealing previously unseen drug-binding poses and providing insights into how they counteract the effects of cocaine. This study establishes a framework for understanding the functioning of the human dopamine transporter and developing therapeutic interventions for dopamine transporter-related disorders and cocaine addiction.
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Affiliation(s)
- Yue Li
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Xianping Wang
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yufei Meng
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Tuo Hu
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jun Zhao
- Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, China
| | - Renjie Li
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qinru Bai
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Pu Yuan
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China
| | - Jun Han
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Kun Hao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yiqing Wei
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yunlong Qiu
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Na Li
- Heart Center and Beijing Key Laboratory of Hypertension, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China
| | - Yan Zhao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
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6
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Stary D, Bajda M. Structural Studies of the Taurine Transporter: A Potential Biological Target from the GABA Transporter Subfamily in Cancer Therapy. Int J Mol Sci 2024; 25:7339. [PMID: 39000444 PMCID: PMC11242302 DOI: 10.3390/ijms25137339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 06/28/2024] [Accepted: 07/02/2024] [Indexed: 07/16/2024] Open
Abstract
The taurine transporter (TauT, SLC6A6) is a member of the solute carrier 6 (SLC6) family, which plays multiple physiological roles. The SLC6 family is divided into four subfamilies: GABA (γ-aminobutyric acid), monoamine, glycine and neutral amino acid transporters. Proteins from the GABA group, including the taurine transporter, are primarily considered therapeutic targets for treating central nervous system disorders. However, recent studies have suggested that inhibitors of SLC6A6 could also serve as anticancer agents. Overexpression of TauT has been associated with the progression of colon and gastric cancer. The pool of known ligands of this transporter is limited and the exact spatial structure of taurine transporter remains unsolved. Understanding its structure could aid in the development of novel inhibitors. Therefore, we utilized homology modelling techniques to create models of TauT. Docking studies and molecular dynamics simulations were conducted to describe protein-ligand interactions. We compared the obtained information for TauT with literature data on other members of the GABA transporter group. Our in silico analysis allowed us to characterize the transporter structure and point out amino acids crucial for ligand binding: Glu406, Gly62 and Tyr138. The significance of selected residues was confirmed through structural studies of mutants. These results will aid in the development of novel taurine transporter inhibitors, which can be explored as anticancer agents.
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Affiliation(s)
- Dorota Stary
- Department of Physicochemical Drug Analysis, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, 30-688 Cracow, Poland
- Doctoral School of Medical and Health Sciences, Jagiellonian University Medical College, św. Łazarza 16, 31-530 Cracow, Poland
| | - Marek Bajda
- Department of Physicochemical Drug Analysis, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, 30-688 Cracow, Poland
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7
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Mortensen JS, Mikkelsen ANL, Wellendorph P. Ways of modulating GABA transporters to treat neurological disease. Expert Opin Ther Targets 2024; 28:529-543. [PMID: 39068514 DOI: 10.1080/14728222.2024.2383611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Accepted: 07/19/2024] [Indexed: 07/30/2024]
Abstract
INTRODUCTION The main inhibitory neurotransmitter in the central nervous system (CNS), γ-aminobutyric acid (GABA), is involved in a multitude of neurological and psychiatric disorders characterized by an imbalance in excitatory and inhibitory signaling. Regulation of extracellular levels of GABA is maintained by the four GABA transporters (GATs; GAT1, GAT2, GAT3, and BGT1), Na+/Cl--coupled transporters of the solute carrier 6 (SLC6) family. Despite mounting evidence for the involvement of the non-GAT1 GABA transporters in diseases, only GAT1 has successfully been translated into clinical practice via the drug tiagabine. AREAS COVERED In this review, all four GATs will be described in terms of their involvement in disease, and the most recent data on structure, function, expression, and localization discussed in relation to their potential role as drug targets. This includes an overview of various ways to modulate the GATs in relation to treatment of diseases caused by imbalances in the GABAergic system. EXPERT OPINION The recent publication of various GAT1 structures is an important milestone for future development of compounds targeting the GATs. Such information can provide much needed insight into mechanistic aspects of all GAT subtypes and be utilized to design improved ligands for this highly interesting drug target class.
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Affiliation(s)
- Jonas S Mortensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Amalie N L Mikkelsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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8
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Bhatt M, Lazzarin E, Alberto-Silva AS, Domingo G, Zerlotti R, Gradisch R, Bazzone A, Sitte HH, Stockner T, Bossi E. Unveiling the crucial role of betaine: modulation of GABA homeostasis via SLC6A1 transporter (GAT1). Cell Mol Life Sci 2024; 81:269. [PMID: 38884791 PMCID: PMC11335192 DOI: 10.1007/s00018-024-05309-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/04/2024] [Accepted: 06/06/2024] [Indexed: 06/18/2024]
Abstract
Betaine is an endogenous osmolyte that exhibits therapeutic potential by mitigating various neurological disorders. However, the underlying cellular and molecular mechanisms responsible for its neuroprotective effects remain puzzling.In this study, we describe a possible mechanism behind the positive impact of betaine in preserving neurons from excitotoxicity. Here we demonstrate that betaine at low concentration modulates the GABA uptake by GAT1 (slc6a1), the predominant GABA transporter in the central nervous system. This modulation occurs through the temporal inhibition of the transporter, wherein prolonged occupancy by betaine impedes the swift transition of the transporter to the inward conformation. Importantly, the modulatory effect of betaine on GAT1 is reversible, as the blocking of GAT1 disappears with increased extracellular GABA. Using electrophysiology, mass spectroscopy, radiolabelled cellular assay, and molecular dynamics simulation we demonstrate that betaine has a dual role in GAT1: at mM concentration acts as a slow substrate, and at µM as a temporal blocker of GABA, when it is below its K0.5. Given this unique modulatory characteristic and lack of any harmful side effects, betaine emerges as a promising neuromodulator of the inhibitory pathways improving GABA homeostasis via GAT1, thereby conferring neuroprotection against excitotoxicity.
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Affiliation(s)
- Manan Bhatt
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy
| | - Erika Lazzarin
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Ana Sofia Alberto-Silva
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Guido Domingo
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy
| | - Rocco Zerlotti
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339, Munich, Germany
| | - Ralph Gradisch
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
| | - Andre Bazzone
- Nanion Technologies GmbH, Ganghoferstr. 70a, 80339, Munich, Germany
| | - Harald H Sitte
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
- Hourani Center for Applied Scientific Research, Al-Ahliyya Amman University, Amman, 19328, Jordan
- Center for Addiction Research and Science, Medical University of Vienna, 1090, Vienna, Austria
| | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Elena Bossi
- Department of Biotechnology and Life Science, Laboratory of Cellular and Molecular Physiology, University of Insubria, Via J. H. Dunant 3, 21100, Varese, Italy.
- Centre for Neuroscience, University of Insubria, 21100, Varese, Italy.
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9
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Wei Y, Li R, Meng Y, Hu T, Zhao J, Gao Y, Bai Q, Li N, Zhao Y. Transport mechanism and pharmacology of the human GlyT1. Cell 2024; 187:1719-1732.e14. [PMID: 38513663 DOI: 10.1016/j.cell.2024.02.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/09/2023] [Accepted: 02/21/2024] [Indexed: 03/23/2024]
Abstract
The glycine transporter 1 (GlyT1) plays a crucial role in the regulation of both inhibitory and excitatory neurotransmission by removing glycine from the synaptic cleft. Given its close association with glutamate/glycine co-activated NMDA receptors (NMDARs), GlyT1 has emerged as a central target for the treatment of schizophrenia, which is often linked to hypofunctional NMDARs. Here, we report the cryo-EM structures of GlyT1 bound with substrate glycine and drugs ALX-5407, SSR504734, and PF-03463275. These structures, captured at three fundamental states of the transport cycle-outward-facing, occluded, and inward-facing-enable us to illustrate a comprehensive blueprint of the conformational change associated with glycine reuptake. Additionally, we identified three specific pockets accommodating drugs, providing clear insights into the structural basis of their inhibitory mechanism and selectivity. Collectively, these structures offer significant insights into the transport mechanism and recognition of substrate and anti-schizophrenia drugs, thus providing a platform to design small molecules to treat schizophrenia.
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Affiliation(s)
- Yiqing Wei
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Renjie Li
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yufei Meng
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tuo Hu
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jun Zhao
- Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences at Weifang, Weifang, Shandong 261000, China
| | - Yiwei Gao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qinru Bai
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Na Li
- Heart Center and Beijing Key Laboratory of Hypertension, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Yan Zhao
- Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
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10
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Drew D, Boudker O. Ion and lipid orchestration of secondary active transport. Nature 2024; 626:963-974. [PMID: 38418916 DOI: 10.1038/s41586-024-07062-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 01/12/2024] [Indexed: 03/02/2024]
Abstract
Transporting small molecules across cell membranes is an essential process in cell physiology. Many structurally diverse, secondary active transporters harness transmembrane electrochemical gradients of ions to power the uptake or efflux of nutrients, signalling molecules, drugs and other ions across cell membranes. Transporters reside in lipid bilayers on the interface between two aqueous compartments, where they are energized and regulated by symported, antiported and allosteric ions on both sides of the membrane and the membrane bilayer itself. Here we outline the mechanisms by which transporters couple ion and solute fluxes and discuss how structural and mechanistic variations enable them to meet specific physiological needs and adapt to environmental conditions. We then consider how general bilayer properties and specific lipid binding modulate transporter activity. Together, ion gradients and lipid properties ensure the effective transport, regulation and distribution of small molecules across cell membranes.
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Affiliation(s)
- David Drew
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
| | - Olga Boudker
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, Weill Cornell Medicine, New York, NY, USA.
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11
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Clarke A, Farr CV, El-Kasaby A, Szöllősi D, Freissmuth M, Sucic S, Stockner T. Probing binding and occlusion of substrate in the human creatine transporter-1 by computation and mutagenesis. Protein Sci 2024; 33:e4842. [PMID: 38032325 PMCID: PMC10751730 DOI: 10.1002/pro.4842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 12/01/2023]
Abstract
In chordates, energy buffering is achieved in part through phosphocreatine, which requires cellular uptake of creatine by the membrane-embedded creatine transporter (CRT1/SLC6A8). Mutations in human slc6a8 lead to creatine transporter deficiency syndrome, for which there is only limited treatment. Here, we used a combined homology modeling, molecular dynamics, and experimental approach to generate a structural model of CRT1. Our observations support the following conclusions: contrary to previous proposals, C144, a key residue in the substrate binding site, is not present in a charged state. Similarly, the side chain D458 must be present in a protonated form to maintain the structural integrity of CRT1. Finally, we identified that the interaction chain Y148-creatine-Na+ is essential to the process of occlusion, which occurs via a "hold-and-pull" mechanism. The model should be useful to study the impact of disease-associated point mutations on the folding of CRT1 and identify approaches which correct folding-deficient mutants.
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Affiliation(s)
- Amy Clarke
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Clemens V Farr
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Daniel Szöllősi
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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12
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Shahsavar A, Wellendorph P. GABA transport cycle: beyond a GAT feeling. Nat Struct Mol Biol 2023:10.1038/s41594-023-01032-5. [PMID: 37400656 DOI: 10.1038/s41594-023-01032-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023]
Affiliation(s)
- Azadeh Shahsavar
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Petrine Wellendorph
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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