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Gallagher CI, Frangos ZJ, Sheipouri D, Shimmon S, Duman MN, Jayakumar S, Cioffi CL, Rawling T, Vandenberg RJ. Novel Phenylene Lipids That Are Positive Allosteric Modulators of Glycine Receptors and Inhibitors of Glycine Transporter 2. ACS Chem Neurosci 2023; 14:2634-2647. [PMID: 37466545 DOI: 10.1021/acschemneuro.3c00167] [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] [Indexed: 07/20/2023] Open
Abstract
Chronic pain is a complex condition that remains resistant to current therapeutics. We previously synthesized a series of N-acyl amino acids (NAAAs) that inhibit the glycine transporter, GlyT2, some of which are also positive allosteric modulators of glycine receptors (GlyRs). In this study, we have synthesized a library of NAAAs that contain a phenylene ring within the acyl tail with the objective of improving efficacy at both GlyT2 and GlyRs and also identifying compounds that are efficacious as dual-acting modulators to enhance glycine neurotransmission. The most efficacious positive allosteric modulator of GlyRs was 2-[8-(2-octylphenyl)octanoylamino]acetic acid (8-8 OPGly) which potentiates the EC5 for glycine activation of GlyRα1 by 1500% with an EC50 of 664 nM. Phenylene-containing NAAAs with a lysine headgroup were the most potent inhibitors of GlyT2 with (2S)-6-amino-2-[8-(3-octylphenyl)octanoylamino]hexanoic acid (8-8 MPLys) inhibiting GlyT2 with an IC50 of 32 nM. The optimal modulator across both proteins was (2S)-6-amino-2-[8-(2-octylphenyl)octanoylamino]hexanoic acid (8-8 OPLys), which inhibits GlyT2 with an IC50 of 192 nM and potentiates GlyRs by up to 335% at 1 μM. When tested in a dual GlyT2/GlyRα1 expression system, 8-8 OPLys caused the greatest reductions in the EC50 for glycine. This suggests that the synergistic effects of a dual-acting modulator cause greater enhancements in glycinergic activity compared to single-target modulators and may provide an alternate approach to the development of new non-opioid analgesics for the treatment of chronic pain.
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Affiliation(s)
- Casey I Gallagher
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Zachary J Frangos
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Diba Sheipouri
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Meryem-Nur Duman
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Robert J Vandenberg
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
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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] [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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Gallagher CI, Ha DA, Harvey RJ, Vandenberg RJ. Positive Allosteric Modulators of Glycine Receptors and Their Potential Use in Pain Therapies. Pharmacol Rev 2022; 74:933-961. [PMID: 36779343 PMCID: PMC9553105 DOI: 10.1124/pharmrev.122.000583] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 04/26/2022] [Accepted: 05/13/2022] [Indexed: 11/22/2022] Open
Abstract
Glycine receptors are ligand-gated ion channels that mediate synaptic inhibition throughout the mammalian spinal cord, brainstem, and higher brain regions. They have recently emerged as promising targets for novel pain therapies due to their ability to produce antinociception by inhibiting nociceptive signals within the dorsal horn of the spinal cord. This has greatly enhanced the interest in developing positive allosteric modulators of glycine receptors. Several pharmaceutical companies and research facilities have attempted to identify new therapeutic leads by conducting large-scale screens of compound libraries, screening new derivatives from natural sources, or synthesizing novel compounds that mimic endogenous compounds with antinociceptive activity. Advances in structural techniques have also led to the publication of multiple high-resolution structures of the receptor, highlighting novel allosteric binding sites and providing additional information for previously identified binding sites. This has greatly enhanced our understanding of the functional properties of glycine receptors and expanded the structure activity relationships of novel pharmacophores. Despite this, glycine receptors are yet to be used as drug targets due to the difficulties in obtaining potent, selective modulators with favorable pharmacokinetic profiles that are devoid of side effects. This review presents a summary of the structural basis for how current compounds cause positive allosteric modulation of glycine receptors and discusses their therapeutic potential as analgesics. SIGNIFICANCE STATEMENT: Chronic pain is a major cause of disability, and in Western societies, this will only increase as the population ages. Despite the high level of prevalence and enormous socioeconomic burden incurred, treatment of chronic pain remains limited as it is often refractory to current analgesics, such as opioids. The National Institute for Drug Abuse has set finding effective, safe, nonaddictive strategies to manage chronic pain as their top priority. Positive allosteric modulators of glycine receptors may provide a therapeutic option.
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Affiliation(s)
- Casey I Gallagher
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Damien A Ha
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Harvey
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Vandenberg
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
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Analysis of Binding Determinants for Different Classes of Competitive and Noncompetitive Inhibitors of Glycine Transporters. Int J Mol Sci 2022; 23:ijms23148050. [PMID: 35887394 PMCID: PMC9317360 DOI: 10.3390/ijms23148050] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 07/14/2022] [Accepted: 07/18/2022] [Indexed: 11/16/2022] Open
Abstract
Glycine transporters are interesting therapeutic targets as they play significant roles in glycinergic and glutamatergic systems. The search for new selective inhibitors of particular types of glycine transporters (GlyT-1 and GlyT-2) with beneficial kinetics is hampered by limited knowledge about the spatial structure of these proteins. In this study, a pool of homology models of GlyT-1 and GlyT-2 in different conformational states was constructed using the crystal structures of related transporters from the SLC6 family and the recently revealed structure of GlyT-1 in the inward-open state, in order to investigate their binding sites. The binding mode of the known GlyT-1 and GlyT-2 inhibitors was determined using molecular docking studies, molecular dynamics simulations, and MM-GBSA free energy calculations. The results of this study indicate that two amino acids, Gly373 and Leu476 in GlyT-1 and the corresponding Ser479 and Thr582 in GlyT-2, are mainly responsible for the selective binding of ligands within the S1 site. Apart from these, one pocket of the S2 site, which lies between TM3 and TM10, may also be important. Moreover, selective binding of noncompetitive GlyT-1 inhibitors in the intracellular release pathway is affected by hydrophobic interactions with Ile399, Met382, and Leu158. These results can be useful in the rational design of new glycine transporter inhibitors with desired selectivity and properties in the future.
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Vallianatou T, Bèchet NB, Correia MSP, Lundgaard I, Globisch D. Regional Brain Analysis of Modified Amino Acids and Dipeptides during the Sleep/Wake Cycle. Metabolites 2021; 12:metabo12010021. [PMID: 35050142 PMCID: PMC8780251 DOI: 10.3390/metabo12010021] [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: 12/07/2021] [Revised: 12/19/2021] [Accepted: 12/22/2021] [Indexed: 12/18/2022] Open
Abstract
Sleep is a state in which important restorative and anabolic processes occur. Understanding changes of these metabolic processes during the circadian rhythm in the brain is crucial to elucidate neurophysiological mechanisms important for sleep function. Investigation of amino acid modifications and dipeptides has recently emerged as a valuable approach in the metabolic profiling of the central nervous system. Nonetheless, very little is known about the effects of sleep on the brain levels of amino acid analogues. In the present study, we examined brain regional sleep-induced alterations selective for modified amino acids and dipeptides using Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) based metabolomics. Our approach enabled the detection and identification of numerous amino acid-containing metabolites in the cortex, the hippocampus, the midbrain, and the cerebellum. In particular, analogues of the aromatic amino acids phenylalanine, tyrosine and tryptophan were significantly altered during sleep in the investigated brain regions. Cortical levels of medium and long chain N-acyl glycines were higher during sleep. Regional specific changes were also detected, especially related to tyrosine analogues in the hippocampus and the cerebellum. Our findings demonstrate a strong correlation between circadian rhythms and amino acid metabolism specific for different brain regions that provide previously unknown insights in brain metabolism.
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Affiliation(s)
- Theodosia Vallianatou
- Science for Life Laboratory, Department of Chemistry-BMC, Uppsala University, Box 599, SE-75124 Uppsala, Sweden; (T.V.); (M.S.P.C.)
| | - Nicholas B. Bèchet
- Department of Experimental Medical Science, Lund University, SE-22362 Lund, Sweden; (N.B.B.); (I.L.)
- Wallenberg Centre for Molecular Medicine, Lund University, SE-22362 Lund, Sweden
| | - Mario S. P. Correia
- Science for Life Laboratory, Department of Chemistry-BMC, Uppsala University, Box 599, SE-75124 Uppsala, Sweden; (T.V.); (M.S.P.C.)
| | - Iben Lundgaard
- Department of Experimental Medical Science, Lund University, SE-22362 Lund, Sweden; (N.B.B.); (I.L.)
- Wallenberg Centre for Molecular Medicine, Lund University, SE-22362 Lund, Sweden
| | - Daniel Globisch
- Science for Life Laboratory, Department of Chemistry-BMC, Uppsala University, Box 599, SE-75124 Uppsala, Sweden; (T.V.); (M.S.P.C.)
- Correspondence:
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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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7
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Inhibition of Glycine Re-Uptake: A Potential Approach for Treating Pain by Augmenting Glycine-Mediated Spinal Neurotransmission and Blunting Central Nociceptive Signaling. Biomolecules 2021; 11:biom11060864. [PMID: 34200954 PMCID: PMC8230656 DOI: 10.3390/biom11060864] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022] Open
Abstract
Among the myriad of cellular and molecular processes identified as contributing to pathological pain, disinhibition of spinal cord nociceptive signaling to higher cortical centers plays a critical role. Importantly, evidence suggests that impaired glycinergic neurotransmission develops in the dorsal horn of the spinal cord in inflammatory and neuropathic pain models and is a key maladaptive mechanism causing mechanical hyperalgesia and allodynia. Thus, it has been hypothesized that pharmacological agents capable of augmenting glycinergic tone within the dorsal horn may be able to blunt or block aberrant nociceptor signaling to the brain and serve as a novel class of analgesics for various pathological pain states. Indeed, drugs that enhance dysfunctional glycinergic transmission, and in particular inhibitors of the glycine transporters (GlyT1 and GlyT2), are generating widespread interest as a potential class of novel analgesics. The GlyTs are Na+/Cl−-dependent transporters of the solute carrier 6 (SLC6) family and it has been proposed that the inhibition of them presents a possible mechanism by which to increase spinal extracellular glycine concentrations and enhance GlyR-mediated inhibitory neurotransmission in the dorsal horn. Various inhibitors of both GlyT1 and GlyT2 have demonstrated broad analgesic efficacy in several preclinical models of acute and chronic pain, providing promise for the approach to deliver a first-in-class non-opioid analgesic with a mechanism of action differentiated from current standard of care. This review will highlight the therapeutic potential of GlyT inhibitors as a novel class of analgesics, present recent advances reported for the field, and discuss the key challenges associated with the development of a GlyT inhibitor into a safe and effective agent to treat pain.
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Pharmacological Evidence on Augmented Antiallodynia Following Systemic Co-Treatment with GlyT-1 and GlyT-2 Inhibitors in Rat Neuropathic Pain Model. Int J Mol Sci 2021; 22:ijms22052479. [PMID: 33804568 PMCID: PMC7957511 DOI: 10.3390/ijms22052479] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/19/2021] [Accepted: 02/25/2021] [Indexed: 12/16/2022] Open
Abstract
The limited effect of current medications on neuropathic pain (NP) has initiated large efforts to develop effective treatments. Animal studies showed that glycine transporter (GlyT) inhibitors are promising analgesics in NP, though concerns regarding adverse effects were raised. We aimed to study NFPS and Org-25543, GlyT-1 and GlyT-2 inhibitors, respectively and their combination in rat mononeuropathic pain evoked by partial sciatic nerve ligation. Cerebrospinal fluid (CSF) glycine content was also determined by capillary electrophoresis. Subcutaneous (s.c.) 4 mg/kg NFPS or Org-25543 showed analgesia following acute administration (30-60 min). Small doses of each compound failed to produce antiallodynia up to 180 min after the acute administration. However, NFPS (1 mg/kg) produced antiallodynia after four days of treatment. Co-treatment with subanalgesic doses of NFPS (1 mg/kg) and Org-25543 (2 mg/kg) produced analgesia at 60 min and thereafter meanwhile increased significantly the CSF glycine content. This combination alleviated NP without affecting motor function. Test compounds failed to activate G-proteins in spinal cord. To the best of our knowledge for the first time we demonstrated augmented analgesia by combining GlyT-1 and 2 inhibitors. Increased CSF glycine content supports involvement of glycinergic system. Combining selective GlyT inhibitors or developing non-selective GlyT inhibitors might have therapeutic value in NP.
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9
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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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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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Wilson KA, Wang L, Lin YC, O'Mara ML. Investigating the lipid fingerprint of SLC6 neurotransmitter transporters: a comparison of dDAT, hDAT, hSERT, and GlyT2. BBA ADVANCES 2021; 1:100010. [PMID: 37082011 PMCID: PMC10074915 DOI: 10.1016/j.bbadva.2021.100010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The local lipid annulus, or "fingerprint", of four SLC6 transporters (dDAT, hDAT, hSERT, and GlyT2) embedded in a complex neuronal membrane were compared and characterised using molecular dynamics. Our analysis included the development of new tools to improve membrane leaflet detection and the analysis of leaflet-dependent properties. Overall, the lipid fingerprints of the four transporters are comprised of similar lipids when grouped by headgroup or tail saturation. The enrichment and depletion of specific lipids, including sites of cholesterol contacts, varies between transporters. The subtle differences in lipid fingerprints results in varying membrane biophysical properties near the transporter. Our results highlight that the lipid-fingerprint of SLC6 transporters in complex membranes is highly dependent on membrane composition. Our results further characterize how the presence and identity of membrane proteins affects the complex interplay of lipid-protein interactions, influencing the local lipid environment and membrane biophysical properties.
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12
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Sheipouri D, Gallagher CI, Shimmon S, Rawling T, Vandenberg RJ. A System for Assessing Dual Action Modulators of Glycine Transporters and Glycine Receptors. Biomolecules 2020; 10:E1618. [PMID: 33266066 PMCID: PMC7760315 DOI: 10.3390/biom10121618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 12/13/2022] Open
Abstract
Reduced inhibitory glycinergic neurotransmission is implicated in a number of neurological conditions such as neuropathic pain, schizophrenia, epilepsy and hyperekplexia. Restoring glycinergic signalling may be an effective method of treating these pathologies. Glycine transporters (GlyTs) control synaptic and extra-synaptic glycine concentrations and slowing the reuptake of glycine using specific GlyT inhibitors will increase glycine extracellular concentrations and increase glycine receptor (GlyR) activation. Glycinergic neurotransmission can also be improved through positive allosteric modulation (PAM) of GlyRs. Despite efforts to manipulate this synapse, no therapeutics currently target it. We propose that dual action modulators of both GlyTs and GlyRs may show greater therapeutic potential than those targeting individual proteins. To show this, we have characterized a co-expression system in Xenopus laevis oocytes consisting of GlyT1 or GlyT2 co-expressed with GlyRα1. We use two electrode voltage clamp recording techniques to measure the impact of GlyTs on GlyRs and the effects of modulators of these proteins. We show that increases in GlyT density in close proximity to GlyRs diminish receptor currents. Reductions in GlyR mediated currents are not observed when non-transportable GlyR agonists are applied or when Na+ is not available. GlyTs reduce glycine concentrations across different concentration ranges, corresponding with their ion-coupling stoichiometry, and full receptor currents can be restored when GlyTs are blocked with selective inhibitors. We show that partial inhibition of GlyT2 and modest GlyRα1 potentiation using a dual action compound, is as useful in restoring GlyR currents as a full and potent single target GlyT2 inhibitor or single target GlyRα1 PAM. The co-expression system developed in this study will provide a robust means for assessing the likely impact of GlyR PAMs and GlyT inhibitors on glycine neurotransmission.
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Affiliation(s)
- Diba Sheipouri
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
| | - Casey I. Gallagher
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (S.S.); (T.R.)
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (S.S.); (T.R.)
| | - Robert J. Vandenberg
- School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia; (D.S.); (C.I.G.)
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Niello M, Gradisch R, Loland CJ, Stockner T, Sitte HH. Allosteric Modulation of Neurotransmitter Transporters as a Therapeutic Strategy. Trends Pharmacol Sci 2020; 41:446-463. [PMID: 32471654 PMCID: PMC7610661 DOI: 10.1016/j.tips.2020.04.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
Neurotransmitter transporters (NTTs) are involved in the fine-tuning of brain neurotransmitter homeostasis. As such, they are implicated in a plethora of complex behaviors, including reward, movement, and cognition. During recent decades, compounds that modulate NTT functions have been developed. Some of them are in clinical use for the management of different neuropsychiatric conditions. The majority of these compounds have been found to selectively interact with the orthosteric site of NTTs. Recently, diverse allosteric sites have been described in a number of NTTs, modulating their function. A more complex NTT pharmacology may be useful in the development of novel therapeutics. Here, we summarize current knowledge on such modulatory allosteric sites, with specific focus on their pharmacological and therapeutic potential.
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Affiliation(s)
- Marco Niello
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ralph Gradisch
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Claus Juul Loland
- Laboratory for Membrane Protein Dynamics. Department of Neuroscience. University of Copenhagen, Copenhagen, Denmark
| | - Thomas Stockner
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Harald H Sitte
- Centre for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria; AddRess, Centre for Addiction Research and Science, Medical University of Vienna, Vienna, Austria.
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14
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Identification of N-acyl amino acids that are positive allosteric modulators of glycine receptors. Biochem Pharmacol 2020; 180:114117. [PMID: 32579961 DOI: 10.1016/j.bcp.2020.114117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 01/31/2023]
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission within the spinal cord and play a crucial role in nociceptive signalling. This makes them primary targets for the development of novel chronic pain therapies. Endogenous lipids have previously been shown to modulate glycine receptors and produce analgesia in pain models, however little is known about what chemical features mediate these effects. In this study, we characterised lipid modulation of GlyRs by screening a library of N-acyl amino acids across all receptor subtypes and determined chemical features crucial for their activity. Acyl-glycine's with a C18 carbon tail were found to produce the greatest potentiation, and require a cis double bond within the central region of the carbon tail (ω6 - ω9) to be active. At 1 µM, C18 ω6,9 glycine potentiated glycine induced currents in α3 and α3β receptors by over 50%, and α1, α2, α1β and α2β receptors by over 100%. C18 ω9 glycine (N-oleoyl glycine) significantly enhance glycine induced peak currents and cause a dose-dependent shift in the glycine concentration response. In the presence of 3 µM C18 ω9 glycine, the EC5o of glycine at the α1 receptor was reduced from 17 µM to 10 µM. This study has identified several acyl-amino acids which are positive allosteric modulators of GlyRs and make promising lead compounds for the development of novel chronic pain therapies.
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15
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Murray M, Roseblade A, Chen Y, Bourget K, Rawling T. Carbon Chain Length Modulates MDA‐MB‐231 Breast Cancer Cell Killing Mechanisms by Mitochondrially Targeted Aryl−Urea Fatty Acids. ChemMedChem 2020; 15:247-255. [DOI: 10.1002/cmdc.201900577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Indexed: 01/06/2023]
Affiliation(s)
- Michael Murray
- Discipline of Pharmacology School of Medical Sciences Faculty of Medicine and HealthUniversity of Sydney Camperdown, New South Wales 2006 Australia
| | - Ariane Roseblade
- School of Mathematical and Physical Sciences Faculty of ScienceUniversity of Technology Sydney Ultimo, New South Wales 2007 Australia
| | - Yongjuan Chen
- Discipline of Pharmacology School of Medical Sciences Faculty of Medicine and HealthUniversity of Sydney Camperdown, New South Wales 2006 Australia
| | - Kirsi Bourget
- Discipline of Pharmacology School of Medical Sciences Faculty of Medicine and HealthUniversity of Sydney Camperdown, New South Wales 2006 Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences Faculty of ScienceUniversity of Technology Sydney Ultimo, New South Wales 2007 Australia
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16
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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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17
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Bioenzymatic and Chemical Derivatization of Renewable Fatty Acids. Biomolecules 2019; 9:biom9100566. [PMID: 31590242 PMCID: PMC6843907 DOI: 10.3390/biom9100566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 10/01/2019] [Accepted: 10/02/2019] [Indexed: 11/17/2022] Open
Abstract
In addition to our previous efforts toward bioenzymatic and chemical transformations of ricinoleic acid and oleic acid to their corresponding α,ω-dicarboxylic acids via their ester intermediates driven in Escherichia coli cells, several efficient oxidation conditions were investigated and optimized for the conversion of ω-hydroxycarboxylic acids to α,ω-dicarboxylic acids. Pd/C-catalyzed oxidation using NaBH4 in a basic aqueous alcohol and Ni(II) salt-catalyzed oxidation using aqueous sodium hypochlorite were considered to be excellent as a hybrid reaction for three successive chemical reactions (hydrogenation, hydrolysis, and oxidation) and an eco-friendly, cost-effective, and practical approach, respectively. Omega-hydroxycarboxylic acids and ω-aminocarboxylic acid were also easily prepared as useful building blocks for plastics or bioactive compounds from the bioenzymatically driven ester intermediate. The scope of the developed synthetic methods can be utilized for large-scale synthesis and various derivatizations.
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18
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Al-Khrasani M, Mohammadzadeh A, Balogh M, Király K, Barsi S, Hajnal B, Köles L, Zádori ZS, Harsing LG. Glycine transporter inhibitors: A new avenue for managing neuropathic pain. Brain Res Bull 2019; 152:143-158. [PMID: 31302238 DOI: 10.1016/j.brainresbull.2019.07.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 06/27/2019] [Accepted: 07/08/2019] [Indexed: 12/12/2022]
Abstract
Interneurons operating with glycine neurotransmitter are involved in the regulation of pain transmission in the dorsal horn of the spinal cord. In addition to interneurons, glycine release also occurs from glial cells neighboring glutamatergic synapses in the spinal cord. Neuronal and glial release of glycine is controlled by glycine transporters (GlyTs). Inhibitors of the two isoforms of GlyTs, the astrocytic type-1 (GlyT-1) and the neuronal type-2 (GlyT-2), decrease pain sensation evoked by injuries of peripheral sensory neurons or inflammation. The function of dorsal horn glycinergic interneurons has been suggested to be reduced in neuropathic pain, which can be reversed by GlyT-2 inhibitors (Org-25543, ALX1393). Several lines of evidence also support that peripheral nerve damage or inflammation may shift glutamatergic neurochemical transmission from N-methyl-D aspartate (NMDA) NR1/NR2A receptor- to NR1/NR2B receptor-mediated events (subunit switch). This pathological overactivation of NR1/NR2B receptors can be reduced by GlyT-1 inhibitors (NFPS, Org-25935), which decrease excessive glycine release from astroglial cells or by selective antagonists of NR2B subunits (ifenprodil, Ro 25-6981). Although several experiments suggest that GlyT inhibitors may represent a novel strategy in the control of neuropathic pain, proving this concept in human beings is hampered by lack of clinically applicable GlyT inhibitors. We also suggest that drugs inhibiting both GlyT-1 and GlyT-2 non-selectively and reversibly, may favorably target neuropathic pain. In this paper we overview inhibitors of the two isoforms of GlyTs as well as the effects of these drugs in experimental models of neuropathic pain. In addition, the possible mechanisms of action of the GlyT inhibitors, i.e. how they affect the neurochemical and pain transmission in the spinal cord, are also discussed. The growing evidence for the possible therapeutic intervention of neuropathic pain by GlyT inhibitors further urges development of drugable compounds, which may beneficially restore impaired pain transmission in various neuropathic conditions.
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Affiliation(s)
- Mahmoud Al-Khrasani
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary.
| | - Amir Mohammadzadeh
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Mihály Balogh
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Kornél Király
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Szilvia Barsi
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Benjamin Hajnal
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - László Köles
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Zoltán S Zádori
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
| | - Laszlo G Harsing
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, Semmelweis University, Nagyvarad ter 4, P.O. Box 370, H-1445 Budapest, Hungary
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19
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Schumann-Gillett A, Blyth MT, O’Mara ML. Is protein structure enough? A review of the role of lipids in SLC6 transporter function. Neurosci Lett 2019; 700:64-69. [DOI: 10.1016/j.neulet.2018.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 05/09/2018] [Accepted: 05/11/2018] [Indexed: 12/17/2022]
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20
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Abstract
The endogenous lipids N-arachidonylglycine and oleoyl-l-carnitine are potential therapeutic leads in the treatment of chronic pain through their inhibition of the glycine transporter GlyT2. However, their mechanism of action is unknown. It has been hypothesized that these "bioactive" lipids either inhibit GlyT2 indirectly, by significantly perturbing the biophysical properties of the membrane, or directly, by binding directly to the transporter (either from a membrane-exposed or solvent-exposed binding site). Here, we used molecular dynamics simulations to study the effects of the lipids anandamide, N-arachidonylglycine, and oleoyl-l-carnitine on (a) the biophysical properties of the bilayer and (b) direct binding interactions with GlyT2. During the simulations, the biophysical properties of the bilayer itself, for example, the area per lipid, bilayer thickness, and order parameters, were not significantly altered by the presence or type of bioactive lipid, regardless of the presence of GlyT2. Our work, together with previous computational and experimental data, suggests that these acyl-inhibitors of GlyT2 inhibit the transporter by directly binding to it. However, these bioactive lipids bound to various parts of GlyT2 and did not prefer a single binding site during 4.5 μs of simulation. We postulate that the binding site is located at the solvent-exposed regions of GlyT2. Understanding the mechanism of action of these and related bioactive lipids is essential in effectively developing high-affinity GlyT2 inhibitors for the treatment of pain.
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Affiliation(s)
| | - Megan L. O’Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT 2601, Australia
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21
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Mostyn SN, Rawling T, Mohammadi S, Shimmon S, Frangos ZJ, Sarker S, Yousuf A, Vetter I, Ryan RM, Christie MJ, Vandenberg RJ. Development of an N-Acyl Amino Acid That Selectively Inhibits the Glycine Transporter 2 To Produce Analgesia in a Rat Model of Chronic Pain. J Med Chem 2019; 62:2466-2484. [PMID: 30714733 DOI: 10.1021/acs.jmedchem.8b01775] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Inhibitors that target the glycine transporter 2, GlyT2, show promise as analgesics, but may be limited by their toxicity through complete or irreversible binding. Acyl-glycine inhibitors, however, are selective for GlyT2 and have been shown to provide analgesia in animal models of pain with minimal side effects, but are comparatively weak GlyT2 inhibitors. Here, we modify the simple acyl-glycine by synthesizing lipid analogues with a range of amino acid head groups in both l- and d-configurations, to produce nanomolar affinity, selective GlyT2 inhibitors. The potent inhibitor oleoyl-d-lysine (33) is also resistant to degradation in both human and rat plasma and liver microsomes, and is rapidly absorbed following an intraperitoneal injection to rats and readily crosses the blood-brain barrier. We demonstrate that 33 provides greater analgesia at lower doses, and does not possess the severe side effects of the very slowly reversible GlyT2 inhibitor, ORG25543 (2).
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Affiliation(s)
- Shannon N Mostyn
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, Faculty of Science , The University of Technology Sydney , Sydney , NSW 2007 , Australia
| | - Sarasa Mohammadi
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, Faculty of Science , The University of Technology Sydney , Sydney , NSW 2007 , Australia
| | - Zachary J Frangos
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Subhodeep Sarker
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Arsalan Yousuf
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Irina Vetter
- Institute for Molecular Bioscience & School of Pharmacy , The University of Queensland , Brisbane , Qld 4072 , Australia
| | - Renae M Ryan
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Macdonald J Christie
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
| | - Robert J Vandenberg
- Discipline of Pharmacology, School of Medical Sciences , University of Sydney , Sydney , NSW 2006 , Australia
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22
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Shang K, Wang Y, Lu Y, Pei Z, Pei Y. Dual-Targeted Supramolecular Vesicles Based on the Complex of Galactose Capped Pillar[5]Arene and Triphenylphosphonium Derivative for Drug Delivery. Isr J Chem 2018. [DOI: 10.1002/ijch.201800080] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Kun Shang
- Shaanxi Key Laboratory of Natural Products & Chemical Biology; College of Chemistry & Pharmacy; Northwest A&F University; Yangling, Shaanxi 712100 P.R. China
| | - Yang Wang
- Shaanxi Key Laboratory of Natural Products & Chemical Biology; College of Chemistry & Pharmacy; Northwest A&F University; Yangling, Shaanxi 712100 P.R. China
| | - Yuchao Lu
- Shaanxi Key Laboratory of Natural Products & Chemical Biology; College of Chemistry & Pharmacy; Northwest A&F University; Yangling, Shaanxi 712100 P.R. China
- Analysis Center of College of Science & Technology; Hebei Agricultural University; Huanghua, Hebei 061100 P.R. China
| | - Zhichao Pei
- Shaanxi Key Laboratory of Natural Products & Chemical Biology; College of Chemistry & Pharmacy; Northwest A&F University; Yangling, Shaanxi 712100 P.R. China
| | - Yuxin Pei
- Shaanxi Key Laboratory of Natural Products & Chemical Biology; College of Chemistry & Pharmacy; Northwest A&F University; Yangling, Shaanxi 712100 P.R. China
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23
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Winters BL, Rawling T, Vandenberg RJ, Christie MJ, Bhola RF, Imlach WL. Activity of novel lipid glycine transporter inhibitors on synaptic signalling in the dorsal horn of the spinal cord. Br J Pharmacol 2018; 175:2337-2347. [PMID: 29500820 DOI: 10.1111/bph.14189] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 02/03/2018] [Accepted: 02/06/2018] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Inhibitory neurotransmission plays an important role in controlling excitability within nociceptive circuits of the spinal cord dorsal horn. Loss of inhibitory signalling is thought to contribute to the development of pathological pain. Preclinical studies suggest that increasing inhibitory glycinergic signalling is a good therapeutic strategy for treating pain. One approach to increase synaptic glycine is to inhibit the activity of the glycine transporter 2 (GlyT2) on inhibitory nerve terminals. These transporters are involved in regulating glycine concentrations and recycling glycine into presynaptic terminals. Inhibiting activity of GlyT2 increases synaptic glycine, which decreases excitability in nociceptive circuits and provides analgesia in neuropathic and inflammatory pain models. EXPERIMENTAL APPROACH We investigated the effects of reversible and irreversible GlyT2 inhibitors on inhibitory glycinergic and NMDA receptor-mediated excitatory neurotransmission in the rat dorsal horn. The effect of these drugs on synaptic signalling was determined using patch-clamp electrophysiology techniques to measure glycine- and NMDA-mediated postsynaptic currents in spinal cord slices in vitro. KEY RESULTS We compared activity of four compounds that increase glycinergic tone with a corresponding increase in evoked glycinergic postsynaptic currents. These compounds did not deplete synaptic glycine release over time. Interestingly, none of these compounds increased glycine-mediated excitatory signalling through NMDA receptors. The results suggest that these compounds preferentially inhibit GlyT2 over G1yT1 with no potentiation of the glycine receptor and without inducing spillover from inhibitory to excitatory synapses. CONCLUSIONS AND IMPLICATIONS GlyT2 inhibitors increase inhibitory neurotransmission in the dorsal horn and have potential as pain therapeutics. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
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Affiliation(s)
- Bryony L Winters
- Pain Management Research Institute, Kolling Institute of Medical Research, The University of Sydney, Royal North Shore Hospital, St Leonards, NSW, Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, Australia
| | - Robert J Vandenberg
- Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Macdonald J Christie
- Discipline of Pharmacology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Rebecca F Bhola
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Wendy L Imlach
- Department of Physiology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
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24
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Armbruster A, Neumann E, Kötter V, Hermanns H, Werdehausen R, Eulenburg V. The GlyT1 Inhibitor Bitopertin Ameliorates Allodynia and Hyperalgesia in Animal Models of Neuropathic and Inflammatory Pain. Front Mol Neurosci 2018; 10:438. [PMID: 29375301 PMCID: PMC5767717 DOI: 10.3389/fnmol.2017.00438] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 12/18/2017] [Indexed: 02/05/2023] Open
Abstract
Background: Chronic pain conditions are difficult to treat and the therapeutic outcome is frequently unsatisfactory. Changes in excitation/inhibition balance within the dorsal horn contribute to the establishment and persistence of chronic pain. Thus, facilitation of inhibitory neurotransmission is a promising approach to treat chronic pain pharmacologically. Glycine transporter 1 (GlyT1) plays an important role in regulating extracellular glycine concentrations. Aim of the present study therefore was to investigate whether the specific GlyT1 inhibitor bitopertin (RG1678; RO4917838) might constitute a novel treatment for chronic pain by facilitating glycinergic inhibition. Methods: Mechanical allodynia and thermal hyperalgesia were induced by chronic constriction injury of the sciatic nerve or carrageenan injections into the plantar surface of the hind paw in rodents. The effect of acute and long-term bitopertin application on the reaction threshold to mechanical and thermal stimuli was determined. General activity was determined in open field experiments. The glycine concentration in cerebrospinal fluid and blood was measured by HPLC. Results: Systemic application of bitopertin in chronic pain conditions lead to a significant increase of the reaction thresholds to mechanical and thermal stimuli in a time and dose-dependent manner. Long-term application of bitopertin effectuated stable beneficial effects over 4 weeks. Bitopertin did not alter reaction thresholds to stimuli in control animals and had no effect on general locomotor activity and anxiety but lead to an increased glycine concentration in cerebrospinal fluid. Conclusion: These findings suggest that inhibition of the GlyT1 by bitopertin represents a promising new approach for the treatment of chronic pain.
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Affiliation(s)
- Anja Armbruster
- Institute of Biochemistry, Emil-Fischer-Center, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Elena Neumann
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Valentin Kötter
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Henning Hermanns
- Department of Anesthesiology, Academic Medical Center, Amsterdam, Netherlands
| | - Robert Werdehausen
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Volker Eulenburg
- Institute of Biochemistry, Emil-Fischer-Center, University of Erlangen-Nuremberg, Erlangen, Germany
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