1
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Chater RC, Quinn AS, Wilson K, Frangos ZJ, Sutton P, Jayakumar S, Cioffi CL, O'Mara ML, Vandenberg RJ. The efficacy of the analgesic GlyT2 inhibitor, ORG25543, is determined by two connected allosteric sites. J Neurochem 2023. [PMID: 38131125 DOI: 10.1111/jnc.16028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/23/2023] [Accepted: 11/28/2023] [Indexed: 12/23/2023]
Abstract
Glycine Transporter 2 (GlyT2) inhibitors have shown considerable potential as analgesics for the treatment of neuropathic pain but also display considerable side effects. One potential source of side effects is irreversible inhibition. In this study, we have characterized the mechanism of ORG25543 inhibition of GlyT2 by first considering three potential ligand binding sites on GlyT2-the substrate site, the vestibule allosteric site and the lipid allosteric site. The three sites were tested using a combination of molecular dynamics simulations and analysis of the inhibition of glycine transport of a series point mutated GlyT2 using electrophysiological methods. We demonstrate that the lipid allosteric site on GlyT2 is the most likely binding site for ORG25543. We also demonstrate that cholesterol derived from the cell membrane can form specific interactions with inhibitor-bound transporters to form an allosteric network of regulatory sites. These observations will guide the future design of GlyT2 inhibitors with the objective of minimising on-target side effects and improving the therapeutic window for the treatment of patients suffering from neuropathic pain.
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Affiliation(s)
- Ryan Cantwell Chater
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Ada S Quinn
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Katie Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Zachary J Frangos
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
| | - Patrick Sutton
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australian Capital Territory, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Queensland, Australia
| | - Robert J Vandenberg
- School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia
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2
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Frangos ZJ, Wilson KA, Aitken HM, Cantwell Chater R, Vandenberg RJ, O'Mara ML. Membrane cholesterol regulates inhibition and substrate transport by the glycine transporter, GlyT2. Life Sci Alliance 2023; 6:e202201708. [PMID: 36690444 PMCID: PMC9873984 DOI: 10.26508/lsa.202201708] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/25/2023] Open
Abstract
Membrane cholesterol binds to and modulates the function of various SLC6 neurotransmitter transporters, including stabilizing the outward-facing conformation of the dopamine and serotonin transporters. Here, we investigate how cholesterol binds to GlyT2 (SLC6A5), modulates glycine transport rate, and influences bioactive lipid inhibition of GlyT2. Bioactive lipid inhibitors are analgesics that bind to an allosteric site accessible from the extracellular solution when GlyT2 adopts an outward-facing conformation. Using molecular dynamics simulations, mutagenesis, and cholesterol depletion experiments, we show that bioactive lipid inhibition of glycine transport is modulated by the recruitment of membrane cholesterol to a binding site formed by transmembrane helices 1, 5, and 7. Recruitment involves cholesterol flipping from its membrane orientation, and insertion of the 3' hydroxyl group into the cholesterol binding cavity, close to the allosteric site. The synergy between cholesterol and allosteric inhibitors provides a novel mechanism of inhibition and a potential avenue for the development of potent GlyT2 inhibitors as alternative therapeutics for the treatment of neuropathic pain and therapeutics that target other SLC6 transporters.
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Affiliation(s)
- Zachary J Frangos
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Katie A Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
| | - Heather M Aitken
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
| | - Ryan Cantwell Chater
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Robert J Vandenberg
- Molecular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, Australia
- Australian Institute of Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia
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3
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Flux coupling, not specificity, shapes the transport and phylogeny of SLC6 glycine transporters. Proc Natl Acad Sci U S A 2022; 119:e2205874119. [PMID: 36191186 PMCID: PMC9564218 DOI: 10.1073/pnas.2205874119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
ATB[Formula: see text] (SLC6A14) is a member of the amino acid transporter branch of the SLC6 family along with GlyT1 (SLC6A9) and GlyT2 (SLC6A5), two glycine-specific transporters coupled to 2:1 and 3:1 Na[Formula: see text]:Cl[Formula: see text], respectively. In contrast, ATB[Formula: see text] exhibits broad substrate specificity for all neutral and cationic amino acids, and its ionic coupling remains unsettled. Using the reversal potential slope method, we demonstrate a 3:1:1 Na[Formula: see text]:Cl[Formula: see text]:Gly stoichiometry for ATB[Formula: see text] that is consistent with its 2.1 e/Gly charge coupling. Like GlyT2, ATB[Formula: see text] behaves as a unidirectional transporter with virtually no glycine efflux at negative potentials after uptake, except by heteroexchange as remarkably shown by leucine activation of NMDARs in Xenopus oocytes coexpressing both membrane proteins. Analysis and computational modeling of the charge movement of ATB[Formula: see text] reveal a higher affinity for sodium in the absence of substrate than GlyT2 and a gating mechanism that locks Na[Formula: see text] into the apo-transporter at depolarized potentials. A 3:1 Na[Formula: see text]:Cl[Formula: see text] stoichiometry justifies the concentrative transport properties of ATB[Formula: see text] and explains its trophic role in tumor growth, while rationalizing its phylogenetic proximity to GlyT2 despite their extreme divergence in specificity.
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4
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Chan MC, Selvam B, Young HJ, Procko E, Shukla D. The substrate import mechanism of the human serotonin transporter. Biophys J 2022; 121:715-730. [PMID: 35114149 PMCID: PMC8943754 DOI: 10.1016/j.bpj.2022.01.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/18/2021] [Accepted: 01/25/2022] [Indexed: 11/17/2022] Open
Abstract
The serotonin transporter (SERT) initiates the reuptake of extracellular serotonin in the synapse to terminate neurotransmission. The cryogenic electron microscopy structures of SERT bound to ibogaine and the physiological substrate serotonin resolved in different states have provided a glimpse of the functional conformations at atomistic resolution. However, the conformational dynamics and structural transitions to intermediate states are not fully understood. Furthermore, the molecular basis of how serotonin is recognized and transported remains unclear. In this study, we performed unbiased microsecond-long simulations of the human SERT to investigate the structural dynamics to various intermediate states and elucidated the complete substrate import pathway. Using Markov state models, we characterized a sequential order of conformational-driven ion-coupled substrate binding and transport events and calculated the free energy barriers of conformation transitions associated with the import mechanism. We find that the transition from the occluded to inward-facing state is the rate-limiting step for substrate import and that the substrate decreases the free energy barriers to achieve the inward-facing state. Our study provides insights on the molecular basis of dynamics-driven ion-substrate recognition and transport of SERT that can serve as a model for other closely related neurotransmitter transporters.
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Affiliation(s)
- Matthew C Chan
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Balaji Selvam
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Heather J Young
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Erik Procko
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois; Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Diwakar Shukla
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois; Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois; National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, Illinois; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois; NIH Center for Macromolecular Modeling and Bioinformatics, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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5
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Frangos ZJ, Cantwell Chater RP, Vandenberg RJ. Glycine Transporter 2: Mechanism and Allosteric Modulation. Front Mol Biosci 2021; 8:734427. [PMID: 34805268 PMCID: PMC8602798 DOI: 10.3389/fmolb.2021.734427] [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: 07/01/2021] [Accepted: 10/25/2021] [Indexed: 01/19/2023] Open
Abstract
Neurotransmitter sodium symporters (NSS) are a subfamily of SLC6 transporters responsible for regulating neurotransmitter signalling. They are a major target for psychoactive substances including antidepressants and drugs of abuse, prompting substantial research into their modulation and structure-function dynamics. Recently, a series of allosteric transport inhibitors have been identified, which may reduce side effect profiles, compared to orthosteric inhibitors. Allosteric inhibitors are also likely to provide different clearance kinetics compared to competitive inhibitors and potentially better clinical outcomes. Crystal structures and homology models have identified several allosteric modulatory sites on NSS including the vestibule allosteric site (VAS), lipid allosteric site (LAS) and cholesterol binding site (CHOL1). Whilst the architecture of eukaryotic NSS is generally well conserved there are differences in regions that form the VAS, LAS, and CHOL1. Here, we describe ligand-protein interactions that stabilize binding in each allosteric site and explore how differences between transporters could be exploited to generate NSS specific compounds with an emphasis on GlyT2 modulation.
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Affiliation(s)
- Zachary J Frangos
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Ryan P Cantwell Chater
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Robert J Vandenberg
- Transporter Biology Group, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
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6
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Fairweather SJ, Shah N, Brӧer S. Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 21:13-127. [PMID: 33052588 DOI: 10.1007/5584_2020_584] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.
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Affiliation(s)
- Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia. .,Resarch School of Chemistry, Australian National University, Canberra, ACT, Australia.
| | - Nishank Shah
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Brӧer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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7
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Wilson KA, Mostyn SN, Frangos ZJ, Shimmon S, Rawling T, Vandenberg RJ, O'Mara ML. The allosteric inhibition of glycine transporter 2 by bioactive lipid analgesics is controlled by penetration into a deep lipid cavity. J Biol Chem 2021; 296:100282. [PMID: 33450225 PMCID: PMC7949037 DOI: 10.1016/j.jbc.2021.100282] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 01/06/2021] [Accepted: 01/08/2021] [Indexed: 01/07/2023] Open
Abstract
The role of lipids in modulating membrane protein function is an emerging and rapidly growing area of research. The rational design of lipids that target membrane proteins for the treatment of pathological conditions is a novel extension in this field and provides a step forward in our understanding of membrane transporters. Bioactive lipids show considerable promise as analgesics for the treatment of chronic pain and bind to a high-affinity allosteric-binding site on the human glycine transporter 2 (GlyT2 or SLC6A5). Here, we use a combination of medicinal chemistry, electrophysiology, and computational modeling to develop a rational structure-activity relationship for lipid inhibitors and demonstrate the key role of the lipid tail interactions for GlyT2 inhibition. Specifically, we examine how lipid inhibitor head group stereochemistry, tail length, and double-bond position promote enhanced inhibition. Overall, the l-stereoisomer is generally a better inhibitor than the d-stereoisomer, longer tail length correlates with greater potency, and the position of the double bond influences the activity of the inhibitor. We propose that the binding of the lipid inhibitor deep into the allosteric-binding pocket is critical for inhibition. Furthermore, this provides insight into the mechanism of inhibition of GlyT2 and highlights how lipids can modulate the activity of membrane proteins by binding to cavities between helices. The principles identified in this work have broader implications for the development of a larger class of compounds that could target SLC6 transporters for disease treatment.
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Affiliation(s)
- Katie A Wilson
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT, Australia
| | - Shannon N Mostyn
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Zachary J Frangos
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, Australia
| | - Robert J Vandenberg
- Discipline of Pharmacology, School of Medical Sciences, University of Sydney, Sydney, NSW, Australia
| | - Megan L O'Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT, Australia.
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8
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Ackermann TM, Allmendinger L, Höfner G, Wanner KT. MS Binding Assays for Glycine Transporter 2 (GlyT2) Employing Org25543 as Reporter Ligand. ChemMedChem 2021; 16:199-215. [PMID: 32734692 PMCID: PMC7821181 DOI: 10.1002/cmdc.202000342] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 07/29/2020] [Indexed: 12/13/2022]
Abstract
This study describes the first binding assay for glycine transporter 2 (GlyT2) following the concept of MS Binding Assays. The selective GlyT2 inhibitor Org25543 was employed as a reporter ligand and it was quantified with a highly sensitive and rapid LC-ESI-MS/MS method. Binding of Org25543 at GlyT2 was characterized in kinetic and saturation experiments with an off-rate of 7.07×10-3 s-1 , an on-rate of 1.01×106 M-1 s-1 , and an equilibrium dissociation constant of 7.45 nM. Furthermore, the inhibitory constants of 19 GlyT ligands were determined in competition experiments. The validity of the GlyT2 affinities determined with the binding assay was examined by a comparison with published inhibitory potencies from various functional assays. With the capability for affinity determination towards GlyT2 the developed MS Binding Assays provide the first tool for affinity profiling of potential ligands and it represents a valuable new alternative to functional assays addressing GlyT2.
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Affiliation(s)
- Thomas M. Ackermann
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Lars Allmendinger
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Georg Höfner
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
| | - Klaus T. Wanner
- Department of Pharmacy, Center for Drug ResearchLudwig-Maximilians-Universität MunichButenandtstraße 781377MunichGermany
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9
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Marques BL, Oliveira-Lima OC, Carvalho GA, de Almeida Chiarelli R, Ribeiro RI, Parreira RC, da Madeira Freitas EM, Resende RR, Klempin F, Ulrich H, Gomez RS, Pinto MCX. Neurobiology of glycine transporters: From molecules to behavior. Neurosci Biobehav Rev 2020; 118:97-110. [PMID: 32712279 DOI: 10.1016/j.neubiorev.2020.07.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/07/2020] [Accepted: 07/17/2020] [Indexed: 12/16/2022]
Abstract
Glycine transporters (GlyTs) are Na+/Cl--dependent neurotransmitter transporters, responsible for l-glycine uptake into the central nervous system. GlyTs are members of the solute carrier family 6 (SLC6) and comprise glycine transporter type 1 (SLC6A9; GlyT1) and glycine transporter type 2 (SLC6A5; Glyt2). GlyT1 and GlyT2 are expressed on both astrocytes and neurons, but their expression pattern in brain tissue is foremost related to neurotransmission. GlyT2 is markedly expressed in brainstem, spinal cord and cerebellum, where it is responsible for glycine uptake into glycinergic and GABAergic terminals. GlyT1 is abundant in neocortex, thalamus and hippocampus, where it is expressed in astrocytes, and involved in glutamatergic neurotransmission. Consequently, inhibition of GlyT1 transporters can modulate glutamatergic neurotransmission through NMDA receptors, suggesting an alternative therapeutic strategy. In this review, we focus on recent progress in the understanding of GlyTs role in brain function and in various diseases, such as epilepsy, hyperekplexia, neuropathic pain, drug addiction, schizophrenia and stroke, as well as in neurodegenerative disorders.
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Affiliation(s)
- Bruno Lemes Marques
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Onésia Cristina Oliveira-Lima
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Gustavo Almeida Carvalho
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raphaela de Almeida Chiarelli
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raul Izidoro Ribeiro
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Ricardo Cambraia Parreira
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Elis Marra da Madeira Freitas
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Rodrigo Ribeiro Resende
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | | | - Henning Ulrich
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Renato Santiago Gomez
- Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Mauro Cunha Xavier Pinto
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil.
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10
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Baliova M, Jursky F. Phosphomimetic Mutation of Glycine Transporter GlyT1 C-Terminal PDZ Binding Motif Inhibits its Interactions with PSD95. J Mol Neurosci 2019; 70:488-493. [DOI: 10.1007/s12031-019-01435-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 11/04/2019] [Indexed: 12/11/2022]
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11
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Mostyn SN, Wilson KA, Schumann-Gillett A, Frangos ZJ, Shimmon S, Rawling T, Ryan RM, O'Mara ML, Vandenberg RJ. Identification of an allosteric binding site on the human glycine transporter, GlyT2, for bioactive lipid analgesics. eLife 2019; 8:e47150. [PMID: 31621581 PMCID: PMC6797481 DOI: 10.7554/elife.47150] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 09/30/2019] [Indexed: 01/01/2023] Open
Abstract
The treatment of chronic pain is poorly managed by current analgesics, and there is a need for new classes of drugs. We recently developed a series of bioactive lipids that inhibit the human glycine transporter GlyT2 (SLC6A5) and provide analgesia in animal models of pain. Here, we have used functional analysis of mutant transporters combined with molecular dynamics simulations of lipid-transporter interactions to understand how these bioactive lipids interact with GlyT2. This study identifies a novel extracellular allosteric modulator site formed by a crevice between transmembrane domains 5, 7, and 8, and extracellular loop 4 of GlyT2. Knowledge of this site could be exploited further in the development of drugs to treat pain, and to identify other allosteric modulators of the SLC6 family of transporters.
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Affiliation(s)
- Shannon N Mostyn
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Katie A Wilson
- Research School of Chemistry, College of ScienceThe Australian National UniversityCanberraAustralia
| | | | - Zachary J Frangos
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Susan Shimmon
- School of Mathematical and Physical SciencesUniversity of Technology SydneySydneyAustralia
| | - Tristan Rawling
- School of Mathematical and Physical SciencesUniversity of Technology SydneySydneyAustralia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
| | - Megan L O'Mara
- Research School of Chemistry, College of ScienceThe Australian National UniversityCanberraAustralia
| | - Robert J Vandenberg
- School of Medical Sciences, Faculty of Medicine and HealthUniversity of SydneySydneyAustralia
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12
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Fratev F, Miranda-Arango M, Lopez AB, Padilla E, Sirimulla S. Discovery of GlyT2 Inhibitors Using Structure-Based Pharmacophore Screening and Selectivity Studies by FEP+ Calculations. ACS Med Chem Lett 2019; 10:904-910. [PMID: 31223446 PMCID: PMC6580377 DOI: 10.1021/acsmedchemlett.9b00003] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 05/21/2019] [Indexed: 12/23/2022] Open
Abstract
In recent years, mammalian Glycine transporter 2 (GlyT2) has emerged as a promising target for the development of compounds against chronic pain states. In our current work, we discovered a new set of promising hits that inhibit the glycine transporter at nano- and micromolar activity and have excellent selectivity over GlyT1 (as shown by in vitro studies) using a newly designed virtual screening (VS) protocol that combines a structure-based pharmacophore and docking screens with a success rate of 75%. Furthermore, the free energy perturbation calculations and molecular dynamics (MD) studies revealed the GlyT2 amino acid residues critical for the binding and selectivity of both Glycine and our Hit1 compound. The FEP+ results well-matched with the available literature mutational data proving the quality of the generated GlyT2 structure. On the basis of these results, we propose that our hit compounds may lead to new chronic pain agents to address unmet and challenging clinical needs.
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Affiliation(s)
- Filip Fratev
- Department
of Pharmaceutical Sciences, School of Pharmacy, The University of Texas at El Paso, El Paso, Texas 79968, United States
- Micar21 Ltd., Persenk 34B, 1407 Sofia, Bulgaria
| | - Manuel Miranda-Arango
- Department
of Biological Sciences, The University of
Texas at El Paso, 500 West University Avenue, El Paso, Texas 79902, United States
| | - Ashley Bryan Lopez
- Department
of Biological Sciences, The University of
Texas at El Paso, 500 West University Avenue, El Paso, Texas 79902, United States
| | - Elvia Padilla
- Department
of Biological Sciences, The University of
Texas at El Paso, 500 West University Avenue, El Paso, Texas 79902, United States
| | - Suman Sirimulla
- Department
of Pharmaceutical Sciences, School of Pharmacy, The University of Texas at El Paso, El Paso, Texas 79968, United States
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13
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Benito-Muñoz C, Perona A, Abia D, Dos Santos HG, Núñez E, Aragón C, López-Corcuera B. Modification of a Putative Third Sodium Site in the Glycine Transporter GlyT2 Influences the Chloride Dependence of Substrate Transport. Front Mol Neurosci 2018; 11:347. [PMID: 30319354 PMCID: PMC6166138 DOI: 10.3389/fnmol.2018.00347] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 09/04/2018] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter removal from glycine-mediated synapses relies on two sodium-driven high-affinity plasma membrane GlyTs that control neurotransmitter availability. Mostly glial GlyT1 is the main regulator of glycine synaptic levels, whereas neuronal GlyT2 promotes the recycling of synaptic glycine and supplies neurotransmitter for presynaptic vesicle refilling. The GlyTs differ in sodium:glycine symport stoichiometry, showing GlyT1 a 2:1 and GlyT2 a 3:1 sodium:glycine coupling. Sodium binds to the GlyTs at two conserved Na+ sites: Na1 and Na2. The location of GlyT2 Na3 site remains unknown, although Glu650 has been involved in the coordination. Here, we have used comparative MD simulations of a GlyT2 model constructed by homology to the crystalized DAT from Drosophila melanogaster by placing the Na3 ion at two different locations. By combination of in silico and experimental data obtained by biochemical and electrophysiological analysis of GlyTs mutants, we provide evidences suggesting the GlyT2 third sodium ion is held by Glu-250 and Glu-650, within a region with robust allosteric properties involved in cation-specific sensitivity. Substitution of Glu650 in GlyT2 by the corresponding methionine in GlyT1 reduced the charge-to-flux ratio to the level of GlyT1 without producing transport uncoupling. Chloride dependence of glycine transport was almost abolished in this GlyT2 mutant but simultaneous substitution of Glu250 and Glu650 by neutral amino acids rescued chloride sensitivity, suggesting that protonation/deprotonation of Glu250 substitutes chloride function. The differential behavior of equivalent GlyT1 mutations sustains a GlyT2-specific allosteric coupling between the putative Na3 site and the chloride site.
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Affiliation(s)
- Cristina Benito-Muñoz
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Almudena Perona
- Smartligs, Parque Científico de Madrid, Campus de Cantoblanco, Madrid, Spain
| | - David Abia
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Helena G Dos Santos
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Enrique Núñez
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Beatriz López-Corcuera
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
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14
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López-Corcuera B, Arribas-González E, Aragón C. Hyperekplexia-associated mutations in the neuronal glycine transporter 2. Neurochem Int 2018; 123:95-100. [PMID: 29859229 DOI: 10.1016/j.neuint.2018.05.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 05/26/2018] [Accepted: 05/29/2018] [Indexed: 12/20/2022]
Abstract
Hyperekplexia or startle disease is a dysfunction of inhibitory glycinergic neurotransmission characterized by an exaggerated startle in response to trivial tactile or acoustic stimuli. Although rare, this disorder can have serious consequences, including sudden infant death. One of the most frequent causes of hyperekplexia are mutations in the SLC6A5 gene, encoding the neuronal glycine transporter 2 (GlyT2), a key component of inhibitory glycinergic presynapses involved in synaptic glycine recycling though sodium and chloride-dependent co-transport. Most GlyT2 mutations detected so far are recessive, but two dominant missense mutations have been described. The detailed analysis of these mutations has revealed structural cues on the quaternary structure of GlyT2, and opens the possibility that novel selective pharmacochaperones have potential therapeutic effects in hyperekplexia.
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Affiliation(s)
- Beatriz López-Corcuera
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain.
| | - Esther Arribas-González
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain
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15
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Carland JE, Thomas M, Mostyn SN, Subramanian N, O’Mara ML, Ryan RM, Vandenberg RJ. Molecular Determinants for Substrate Interactions with the Glycine Transporter GlyT2. ACS Chem Neurosci 2018; 9:603-614. [PMID: 29120604 DOI: 10.1021/acschemneuro.7b00407] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Transporters in the SLC6 family play key roles in regulating neurotransmission and are the targets for a wide range of therapeutics. Important insights into the transport mechanisms and the specificity of drug interactions of SLC6 transporters have been obtained from the crystal structures of a bacterial homologue of the family, LeuTAa, and more recently the Drosophila dopamine transporter and the human serotonin transporter. However, there is disputed evidence that the bacterial leucine transporter, LeuTAa, contains two substrate binding sites that work cooperatively in the mechanism of transport, with the binding of a second substrate being required for the release of the substrate from the primary site. An alternate proposal is that there may be low affinity binding sites that serve to direct the flow of substrates to the primary site. We have used a combination of molecular dynamics simulations of substrate interactions with a homology model of GlyT2, together with radiolabeled amino acid uptake assays and electrophysiological analysis of wild-type and mutant transporters, to provide evidence that substrate selectivity of GlyT2 is determined entirely by the primary substrate binding site and, furthermore, if a secondary site exists then it is a low affinity nonselective amino acid binding site.
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Affiliation(s)
- Jane E. Carland
- Discipline of Pharmacology, School of Medical Sciences, Molecular Biosciences Building, University of Sydney, Sydney, NSW 2006, Australia
| | - Michael Thomas
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
| | - Shannon N. Mostyn
- Discipline of Pharmacology, School of Medical Sciences, Molecular Biosciences Building, University of Sydney, Sydney, NSW 2006, Australia
| | - Nandhitha Subramanian
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
| | - Megan L. O’Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
| | - Renae M. Ryan
- Discipline of Pharmacology, School of Medical Sciences, Molecular Biosciences Building, University of Sydney, Sydney, NSW 2006, Australia
| | - Robert J. Vandenberg
- Discipline of Pharmacology, School of Medical Sciences, Molecular Biosciences Building, University of Sydney, Sydney, NSW 2006, Australia
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16
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Abstract
Glycine, besides exerting essential metabolic functions, is an important inhibitory neurotransmitter in caudal areas of the central nervous system and also a positive neuromodulator at excitatory glutamate-mediated synapses. Glial cells provide metabolic support to neurons and modulate synaptic activity. Six transporters belonging to three solute carrier families (SLC6, SLC38, and SLC7) are capable of transporting glycine across the glial plasma membrane. The unique glial glycine-selective transporter GlyT1 (SLC6) is the main regulator of synaptic glycine concentrations, assisted by the neuronal GlyT2. The five additional glycine transporters ATB0,+, SNAT1, SNAT2, SNAT5, and LAT2 display broad amino acid specificity and have differential contributions to glial glycine transport. Glial glycine transporters are divergent in sequence but share a similar architecture displaying the 5 + 5 inverted fold originally characterized in the leucine transporter LeuT. The availability of protein crystals solved at high resolution for prokaryotic and, more recently, eukaryotic homologues of this superfamily has advanced significantly our understanding of the mechanism of glycine transport.
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17
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Glycinergic transmission: glycine transporter GlyT2 in neuronal pathologies. Neuronal Signal 2016; 1:NS20160009. [PMID: 32714574 PMCID: PMC7377260 DOI: 10.1042/ns20160009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/04/2016] [Accepted: 11/09/2016] [Indexed: 11/17/2022] Open
Abstract
Glycinergic neurons are major contributors to the regulation of neuronal excitability, mainly in caudal areas of the nervous system. These neurons control fluxes of sensory information between the periphery and the CNS and diverse motor activities like locomotion, respiration or vocalization. The phenotype of a glycinergic neuron is determined by the expression of at least two proteins: GlyT2, a plasma membrane transporter of glycine, and VIAAT, a vesicular transporter shared by glycine and GABA. In this article, we review recent advances in understanding the role of GlyT2 in the pathophysiology of inhibitory glycinergic neurotransmission. GlyT2 mutations are associated to decreased glycinergic function that results in a rare movement disease termed hyperekplexia (HPX) or startle disease. In addition, glycinergic neurons control pain transmission in the dorsal spinal cord and their function is reduced in chronic pain states. A moderate inhibition of GlyT2 may potentiate glycinergic inhibition and constitutes an attractive target for pharmacological intervention against these devastating conditions.
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18
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Subramanian N, Scopelliti AJ, Carland JE, Ryan RM, O'Mara ML, Vandenberg RJ. Correction: Identification of a 3rd Na+ Binding Site of the Glycine Transporter, GlyT2. PLoS One 2016; 11:e0159896. [PMID: 27434127 PMCID: PMC4951049 DOI: 10.1371/journal.pone.0159896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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