1
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Thompson MJ, Mansoub Bekarkhanechi F, Ananchenko A, Nury H, Baenziger JE. A release of local subunit conformational heterogeneity underlies gating in a muscle nicotinic acetylcholine receptor. Nat Commun 2024; 15:1803. [PMID: 38413583 PMCID: PMC10899235 DOI: 10.1038/s41467-024-46028-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 02/12/2024] [Indexed: 02/29/2024] Open
Abstract
Synaptic receptors respond to neurotransmitters by opening an ion channel across the post-synaptic membrane to elicit a cellular response. Here we use recent Torpedo acetylcholine receptor structures and functional measurements to delineate a key feature underlying allosteric communication between the agonist-binding extracellular and channel-gating transmembrane domains. Extensive mutagenesis at this inter-domain interface re-affirms a critical energetically coupled role for the principal α subunit β1-β2 and M2-M3 loops, with agonist binding re-positioning a key β1-β2 glutamate/valine to facilitate the outward motions of a conserved M2-M3 proline to open the channel gate. Notably, the analogous structures in non-α subunits adopt a locally active-like conformation in the apo state even though each L9' hydrophobic gate residue in each pore-lining M2 α-helix is closed. Agonist binding releases local conformational heterogeneity transitioning all five subunits into a conformationally symmetric open state. A release of conformational heterogeneity provides a framework for understanding allosteric communication in pentameric ligand-gated ion channels.
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Affiliation(s)
- Mackenzie J Thompson
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
| | | | - Anna Ananchenko
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON, K1H 8M5, Canada
| | - Hugues Nury
- Université Grenoble Alpes, CNRS, CEA, IBS, F-38000, Grenoble, France
| | - John E Baenziger
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON, K1H 8M5, Canada.
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2
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Chen Q, Li L, Xu L, Yang B, Huang Y, Qiao D, Yue X. Proteomic analysis discovers potential biomarkers of early traumatic axonal injury in the brainstem. Int J Legal Med 2024; 138:207-227. [PMID: 37338605 DOI: 10.1007/s00414-023-03039-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 06/01/2023] [Indexed: 06/21/2023]
Abstract
OBJECTIVE Application of Tandem Mass Tags (TMT)-based LC-MS/MS analysis to screen for differentially expressed proteins (DEPs) in traumatic axonal injury (TAI) of the brainstem and to predict potential biomarkers and key molecular mechanisms of brainstem TAI. METHODS A modified impact acceleration injury model was used to establish a brainstem TAI model in Sprague-Dawley rats, and the model was evaluated in terms of both functional changes (vital sign measurements) andstructural changes (HE staining, silver-plating staining and β-APP immunohistochemical staining). TMT combined with LC-MS/MS was used to analyse the DEPs in brainstem tissues from TAI and Sham groups. The biological functions of DEPs and potential molecular mechanisms in the hyperacute phase of TAI were analysed by bioinformatics techniques, and candidate biomarkers were validated using western blotting and immunohistochemistry on brainstem tissues from animal models and humans. RESULTS Based on the successful establishment of the brainstem TAI model in rats, TMT-based proteomics identified 65 DEPs, and bioinformatics analysis indicated that the hyperacute phase of TAI involves multiple stages of biological processes including inflammation, oxidative stress, energy metabolism, neuronal excitotoxicity and apoptosis. Three DEPs, CBR1, EPHX2 and CYP2U1, were selected as candidate biomarkers and all three proteins were found to be significantly expressed in brainstem tissue 30 min-7 days after TAI in both animal models and humans. CONCLUSION Using TMT combined with LC-MS/MS analysis for proteomic study of early TAI in rat brainstem, we report for the first time that CBR1, EPHX2 and CYP2U1 can be used as biomarkers of early TAI in brainstem by means of western blotting and immunohistochemical staining, compensating for the limitations of silver-plating staining and β-APP immunohistochemical staining, especially in the case of very short survival time after TAI (shorter than 30 min). A number of other proteins that also have a potential marker role are also presented, providing new insights into the molecular mechanisms, therapeutic targets and forensic identification of early TAI in brainstem.
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Affiliation(s)
- Qianling Chen
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Lingyue Li
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Luyao Xu
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Bin Yang
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Yuebing Huang
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China
| | - Dongfang Qiao
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China.
| | - Xia Yue
- Guangzhou Key Laboratory of Forensic Multi-Omics for Precision Identification, School of Forensic Medicine, Southern Medical University, Guangzhou, 510515, Guangdong, China.
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3
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Bondarenko V, Chen Q, Singewald K, Haloi N, Tillman TS, Howard RJ, Lindahl E, Xu Y, Tang P. Structural Elucidation of Ivermectin Binding to α7nAChR and the Induced Channel Desensitization. ACS Chem Neurosci 2023; 14:1156-1165. [PMID: 36821490 PMCID: PMC10020961 DOI: 10.1021/acschemneuro.2c00783] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
The α7 nicotinic acetylcholine receptor (α7nAChR) mediates signaling in the central nervous system and cholinergic anti-inflammatory pathways. Ivermectin is a positive allosteric modulator of a full-length α7nAChR and an agonist of the α7nAChR construct containing transmembrane (TMD) and intracellular (ICD) domains, but structural insights of the binding have not previously been determined. Here, combining nuclear magnetic resonance as a primary experimental tool with Rosetta comparative modeling and molecular dynamics simulations, we have revealed details of ivermectin binding to the α7nAChR TMD + ICD and corresponding structural changes in an ivermectin-induced desensitized state. Ivermectin binding was stabilized predominantly by hydrophobic interactions from interfacial residues between adjacent subunits near the extracellular end of the TMD, where the inter-subunit gap was substantially expanded in comparison to the apo structure. The ion-permeation pathway showed a profile distinctly different from the resting-state profile but similar to profiles of desensitized α7nAChR. The ICD also exhibited structural changes, including reorientation of the MX and h3 helices relative to the channel axis. The resulting structures of the α7nAChR TMD + ICD in complex with ivermectin provide opportunities for discovering new modulators of therapeutic potential and exploring the structural basis of cytoplasmic signaling under different α7nAChR functional states.
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Affiliation(s)
- Vasyl Bondarenko
- Department
of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Qiang Chen
- Department
of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Kevin Singewald
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Nandan Haloi
- Department
of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, SE-17121 Solna, Sweden
- Department
of Applied Physics, Swedish e-Science Research Center, KTH Royal Institute of Technology, PO Box 1031, SE-17121 Solna, Sweden
| | - Tommy S. Tillman
- Department
of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Rebecca J. Howard
- Department
of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, SE-17121 Solna, Sweden
- Department
of Applied Physics, Swedish e-Science Research Center, KTH Royal Institute of Technology, PO Box 1031, SE-17121 Solna, Sweden
| | - Erik Lindahl
- Department
of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, SE-17121 Solna, Sweden
- Department
of Applied Physics, Swedish e-Science Research Center, KTH Royal Institute of Technology, PO Box 1031, SE-17121 Solna, Sweden
| | - Yan Xu
- Department
of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department
of Pharmacology and Chemical Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department
of Structural Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department
of Physics and Astronomy, University of
Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Pei Tang
- Department
of Anesthesiology and Perioperative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department
of Pharmacology and Chemical Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- Department
of Computational and Systems Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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4
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Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models. J Mol Biol 2021; 433:167128. [PMID: 34224751 DOI: 10.1016/j.jmb.2021.167128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 02/06/2023]
Abstract
The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.
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5
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Chatzigoulas A, Cournia Z. Rational design of allosteric modulators: Challenges and successes. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2021. [DOI: 10.1002/wcms.1529] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Alexios Chatzigoulas
- Biomedical Research Foundation Academy of Athens Athens Greece
- Department of Informatics and Telecommunications National and Kapodistrian University of Athens Athens Greece
| | - Zoe Cournia
- Biomedical Research Foundation Academy of Athens Athens Greece
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6
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Mechanisms of activation and desensitization of full-length glycine receptor in lipid nanodiscs. Nat Commun 2020; 11:3752. [PMID: 32719334 PMCID: PMC7385131 DOI: 10.1038/s41467-020-17364-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 06/25/2020] [Indexed: 12/31/2022] Open
Abstract
Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Glycine receptors (GlyRs) are key players in mediating fast inhibitory neurotransmission at these synapses. While previous high-resolution structures have provided insights into the molecular architecture of GlyR, several mechanistic questions pertaining to channel function are still unanswered. Here, we present Cryo-EM structures of the full-length GlyR protein complex reconstituted into lipid nanodiscs that are captured in the unliganded (closed), glycine-bound (open and desensitized), and allosteric modulator-bound conformations. A comparison of these states reveals global conformational changes underlying GlyR channel gating and modulation. The functional state assignments were validated by molecular dynamics simulations, and the observed permeation events are in agreement with the anion selectivity and conductance of GlyR. These studies provide the structural basis for gating, ion selectivity, and single-channel conductance properties of GlyR in a lipid environment. Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Here, authors present cryo-EM structures of the full-length glycine receptors (GlyRs) reconstituted into lipid nanodiscs in the unliganded, glycine-bound and allosteric modulator-bound conformations and reveal global conformational changes underlying GlyR channel gating and modulation.
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7
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Yao L, Wells M, Wu X, Xu Y, Zhang L, Xiong W. Membrane cholesterol dependence of cannabinoid modulation of glycine receptor. FASEB J 2020; 34:10920-10930. [PMID: 32608538 DOI: 10.1096/fj.201903093r] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 04/30/2020] [Accepted: 06/08/2020] [Indexed: 11/11/2022]
Abstract
Cannabinoids exert therapeutic effects on several diseases such as chronic pain and startle disease by targeting glycine receptors (GlyRs). Our previous studies have shown that cannabinoids target a serine residue at position 296 in the third transmembrane helix of the α1/α3 GlyR. This site is located on the outside of the ion channel protein at the lipid interface where the cholesterol concentrates. However, whether membrane cholesterol regulates cannabinoid-GlyR interaction remains unknown. Here, we show that GlyRs are closely associated with cholesterol/caveolin-rich domains at subcellular levels. Membrane cholesterol reduction significantly inhibits cannabinoid potentiation of glycine-activated currents in cultured spinal neurons and in HEK 293T cells expressing α1/α3 GlyRs. Such inhibition is fully rescued by cholesterol replenishment in a concentration-dependent manner. Molecular docking calculations further reveal that cholesterol regulates cannabinoid enhancement of GlyR function through both direct and indirect mechanisms. Taken together, these findings suggest that cholesterol is critical for the cannabinoid-GlyR interaction in the cell membrane.
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Affiliation(s)
- Lei Yao
- Institute on Aging and Brain Disorders, the First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China
| | - Marta Wells
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Xiongwu Wu
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Yan Xu
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Li Zhang
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Wei Xiong
- Institute on Aging and Brain Disorders, the First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China.,Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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8
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Pandhare A, Pirayesh E, Stuebler AG, Jansen M. Triple arginines as molecular determinants for pentameric assembly of the intracellular domain of 5-HT 3A receptors. J Gen Physiol 2019; 151:1135-1145. [PMID: 31409663 PMCID: PMC6719409 DOI: 10.1085/jgp.201912421] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/15/2019] [Indexed: 11/20/2022] Open
Abstract
Serotonin type 3A receptors are homopentameric ligand-gated ion channels that are thought to assemble via interactions involving the subunits’ extracellular and transmembrane domains. Pandhare et al. reveal that channel assembly is also determined by three arginine residues in the receptor’s intracellular domain. Serotonin type 3 receptors (5-HT3Rs) are cation-conducting pentameric ligand-gated ion channels and members of the Cys-loop superfamily in eukaryotes. 5-HT3Rs are found in the peripheral and central nervous system, and they are targets for drugs used to treat anxiety, drug dependence, and schizophrenia, as well as chemotherapy-induced and postoperative nausea and emesis. Decades of research of Cys-loop receptors have identified motifs in both the extracellular and transmembrane domains that mediate pentameric assembly. Those efforts have largely ignored the most diverse domain of these channels, the intracellular domain (ICD). Here we identify molecular determinants within the ICD of serotonin type 3A (5-HT3A) subunits for pentameric assembly by first identifying the segments contributing to pentamerization using deletion constructs of, and finally by making defined amino acid substitutions within, an isolated soluble ICD. Our work provides direct experimental evidence for the contribution of three intracellular arginines, previously implicated in governing the low conductance of 5-HT3ARs, in structural features such as pentameric assembly.
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Affiliation(s)
- Akash Pandhare
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Elham Pirayesh
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Antonia G Stuebler
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Michaela Jansen
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
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9
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Solution NMR Spectroscopy for the Determination of Structures of Membrane Proteins in a Lipid Environment. Methods Mol Biol 2019. [PMID: 31218634 DOI: 10.1007/978-1-4939-9512-7_24] [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: 08/07/2023]
Abstract
NMR spectroscopy has harnessed the recent technical advances to emerge as a competitive, elegant, and eminently viable technique for determining the solution structures of membrane proteins at the level of atomic resolution. Once a good level of cell-based or cell-free expression and purification of a suitably sized membrane protein has been achieved, then NMR offers a combination of several versatile strategies, for example choice of appropriate deuterated or nondeuterated detergents, temperature, and ionic strength; isotope labeling with 2H, 13C, 15N, with or without protonation of Ile (δ1), Leu, and Val methyl protons; combinatorial labeling or unlabeling of specific amino acids; TROSY based-, nonuniform sampling (NUS) based-, and other NMR experiments; measurement of residual dipolar couplings using stretched polyacrylamide gels or DNA nanotubes; spin labeling and paramagnetic relaxation enhancements (PRE). Strategic combinations of these advancements together with availability of highly sensitive cryogenically cooled-probes equipped high-field NMR spectrometers (up to 1 GHz 1H frequency) have allowed the perseverant investigator to successfully overcome several of the conventional pitfalls associated with the NMR technique and membrane proteins, viz., low sensitivity, poor sample stability, spectral crowding, and a limited number of NOEs and other constraints for structure calculations. This has resulted in an unprecedented growth in the number of successfully determined NMR structures of large and complex membrane proteins over the last two decades, and this technique now holds great promise for the structure determination of an ever larger body of membrane proteins.
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10
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Analytical techniques for characterization of biological molecules - proteins and aptamers/oligonucleotides. Bioanalysis 2018; 11:103-117. [PMID: 30475073 DOI: 10.4155/bio-2018-0225] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
With the advent of the high-throughput technologies and exciting times for biology, the discipline of analytical methodology is experiencing a surge in the growth and the scope. Over the years, multitude of analytical techniques have evolved from a work-intensive, low sensitivity and high volume of reagent and sample consumption endeavor to automated, better selectivity, lower limit of quantification and cost-effective techniques for biological research. In this review, we give an overview of the currently available wide range of cell-based and noncell based and structural based analytical techniques, their principle and biological applications. The analytical techniques discussed in this paper includes surface plasmon resonance, electrophoresis, enzyme linked immunosorbent assay, Western blotting, flow cytometry, fluorescence activated cell sorting, mass spectrometry, nuclear magnetic resonance and x-ray crystallography.
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11
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Structural basis of neurosteroid anesthetic action on GABA A receptors. Nat Commun 2018; 9:3972. [PMID: 30266951 PMCID: PMC6162318 DOI: 10.1038/s41467-018-06361-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 08/28/2018] [Indexed: 12/05/2022] Open
Abstract
Type A γ-aminobutyric acid receptors (GABAARs) are inhibitory pentameric ligand-gated ion channels in the brain. Many anesthetics and neurosteroids act through binding to the GABAAR transmembrane domain (TMD), but the structural basis of their actions is not well understood and no resting-state GABAAR structure has been determined. Here, we report crystal structures of apo and the neurosteroid anesthetic alphaxalone-bound desensitized chimeric α1GABAAR (ELIC-α1GABAAR). The chimera retains the functional and pharmacological properties of GABAARs, including potentiation, activation and desensitization by alphaxalone. The apo-state structure reveals an unconventional activation gate at the intracellular end of the pore. The desensitized structure illustrates molecular determinants for alphaxalone binding to an inter-subunit TMD site. These structures suggest a plausible signaling pathway from alphaxalone binding at the bottom of the TMD to the channel gate in the pore-lining TM2 through the TM1–TM2 linker. The study provides a framework to discover new GABAAR modulators with therapeutic potential. The anesthetic alphaxalone binds γ-aminobutyric acid type A receptors (GABAARs) that play an important role in regulating sensory processes. Here the authors present the structures of a α1GABAAR chimera in the resting state and in an alphaxalone-bound desensitized state, which might facilitate the development of new GABAAR modulators.
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12
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Exploring conformational states and helical packings in the P2X receptor transmembrane domain by molecular dynamics simulation. J Biol Phys 2018; 44:331-344. [PMID: 29611030 DOI: 10.1007/s10867-018-9493-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 03/19/2018] [Indexed: 02/05/2023] Open
Abstract
The P2X receptor is a trimeric transmembrane protein that acts as an ATP-gated ion channel. Its transmembrane domain (TMD) contains only six helices and three of them, the M2 helices, line the ion conduction pathway. Here, using molecular dynamics simulation, I identify four conformational states of the TMD that are associated with four types of packing between M2 helices. Packing in the extracellular half of the M2 helix produces closed conformations, while packing in the intracellular half produces both open and closed conformations. State transition is observed and supports a mechanism where iris-like twisting of the M2 helices switches the location of helical packing between the extracellular and the intracellular halves of the helices. In addition, this twisting motion alters the position and orientation of residue side-chains relative to the pore and therefore influences the pore geometry and possibly ion permeation. Helical packing, on the other hand, may restrict the twisting motion and generate discrete conformational states.
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13
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Bondarenko V, Wells M, Xu Y, Tang P. Solution NMR Studies of Anesthetic Interactions with Ion Channels. Methods Enzymol 2018; 603:49-66. [PMID: 29673534 DOI: 10.1016/bs.mie.2018.01.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
NMR spectroscopy is one of the major tools to provide atomic resolution protein structural information. It has been used to elucidate the molecular details of interactions between anesthetics and ion channels, to identify anesthetic binding sites, and to characterize channel dynamics and changes introduced by anesthetics. In this chapter, we present solution NMR methods essential for investigating interactions between ion channels and general anesthetics, including both volatile and intravenous anesthetics. Case studies are provided with a focus on pentameric ligand-gated ion channels and the voltage-gated sodium channel NaChBac.
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Affiliation(s)
- Vasyl Bondarenko
- University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Marta Wells
- University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Yan Xu
- University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Pei Tang
- University of Pittsburgh School of Medicine, Pittsburgh, PA, United States.
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14
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Neumann J, Rose-Sperling D, Hellmich UA. Diverse relations between ABC transporters and lipids: An overview. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:605-618. [PMID: 27693344 DOI: 10.1016/j.bbamem.2016.09.023] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/24/2016] [Accepted: 09/26/2016] [Indexed: 12/19/2022]
Abstract
It was first discovered in 1992 that P-glycoprotein (Pgp, ABCB1), an ATP binding cassette (ABC) transporter, can transport phospholipids such as phosphatidylcholine, -ethanolamine and -serine as well as glucosylceramide and glycosphingolipids. Subsequently, many other ABC transporters were identified to act as lipid transporters. For substrate transport by ABC transporters, typically a classic, alternating access model with an ATP-dependent conformational switch between a high and a low affinity substrate binding site is evoked. Transport of small hydrophilic substrates can easily be imagined this way, as the molecule can in principle enter and exit the transporter in the same orientation. Lipids on the other hand need to undergo a 180° degree turn as they translocate from one membrane leaflet to the other. Lipids and lipidated molecules are highly diverse, so there may be various ways how to achieve their flipping and flopping. Nonetheless, an increase in biophysical, biochemical and structural data is beginning to shed some light on specific aspects of lipid transport by ABC transporters. In addition, there is now abundant evidence that lipids affect ABC transporter conformation, dynamics as well as transport and ATPase activity in general. In this review, we will discuss different ways in which lipids and ABC transporters interact and how lipid translocation may be achieved with a focus on the techniques used to investigate these processes. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Jennifer Neumann
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany
| | - Dania Rose-Sperling
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany
| | - Ute A Hellmich
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg University Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany.
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15
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Labonne JDJ, Graves TD, Shen Y, Jones JR, Kong IK, Layman LC, Kim HG. A microdeletion at Xq22.2 implicates a glycine receptor GLRA4 involved in intellectual disability, behavioral problems and craniofacial anomalies. BMC Neurol 2016; 16:132. [PMID: 27506666 PMCID: PMC4979147 DOI: 10.1186/s12883-016-0642-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/20/2016] [Indexed: 12/03/2022] Open
Abstract
Background Among the 21 annotated genes at Xq22.2, PLP1 is the only known gene involved in Xq22.2 microdeletion and microduplication syndromes with intellectual disability. Using an atypical microdeletion, which does not encompass PLP1, we implicate a novel gene GLRA4 involved in intellectual disability, behavioral problems and craniofacial anomalies. Case presentation We report a female patient (DGDP084) with a de novo Xq22.2 microdeletion of at least 110 kb presenting with intellectual disability, motor delay, behavioral problems and craniofacial anomalies. While her phenotypic features such as cognitive impairment and motor delay show overlap with Pelizaeus-Merzbacher disease (PMD) caused by PLP1 mutations at Xq22.2, this gene is not included in our patient’s microdeletion and is not dysregulated by a position effect. Because the microdeletion encompasses only three genes, GLRA4, MORF4L2 and TCEAL1, we investigated their expression levels in various tissues by RT-qPCR and found that all three genes were highly expressed in whole human brain, fetal brain, cerebellum and hippocampus. When we examined the transcript levels of GLRA4, MORF4L2 as well as TCEAL1 in DGDP084′s family, however, only GLRA4 transcripts were reduced in the female patient compared to her healthy mother. This suggests that GLRA4 is the plausible candidate gene for cognitive impairment, behavioral problems and craniofacial anomalies observed in DGDP084. Importantly, glycine receptors mediate inhibitory synaptic transmission in the brain stem as well as the spinal cord, and are known to be involved in syndromic intellectual disability. Conclusion We hypothesize that GLRA4 is involved in intellectual disability, behavioral problems and craniofacial anomalies as the second gene identified for X-linked syndromic intellectual disability at Xq22.2. Additional point mutations or intragenic deletions of GLRA4 as well as functional studies are needed to further validate our hypothesis. Electronic supplementary material The online version of this article (doi:10.1186/s12883-016-0642-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jonathan D J Labonne
- Department of Obstetrics & Gynecology, Section of Reproductive Endocrinology, Infertility & Genetics, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA
| | - Tyler D Graves
- Department of Obstetrics & Gynecology, Section of Reproductive Endocrinology, Infertility & Genetics, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA
| | - Yiping Shen
- Department of Laboratory Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, 02115, USA
| | | | - Il-Keun Kong
- Department of Animal Science, Division of Applied Life Science (BK21plus), Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, Gyeongsangnam-do, South Korea
| | - Lawrence C Layman
- Department of Obstetrics & Gynecology, Section of Reproductive Endocrinology, Infertility & Genetics, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.,Neuroscience Program, Medical College of Georgia, Augusta University, Augusta, GA, 30912, USA
| | - Hyung-Goo Kim
- Department of Obstetrics & Gynecology, Section of Reproductive Endocrinology, Infertility & Genetics, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA. .,Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA, 30912, USA.
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16
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Burgos CF, Yévenes GE, Aguayo LG. Structure and Pharmacologic Modulation of Inhibitory Glycine Receptors. Mol Pharmacol 2016; 90:318-25. [PMID: 27401877 DOI: 10.1124/mol.116.105726] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 07/08/2016] [Indexed: 01/08/2023] Open
Abstract
Glycine receptors (GlyR) are inhibitory Cys-loop ion channels that contribute to the control of excitability along the central nervous system (CNS). GlyR are found in the spinal cord and brain stem, and more recently they were reported in higher regions of the CNS such as the hippocampus and nucleus accumbens. GlyR are involved in motor coordination, respiratory rhythms, pain transmission, and sensory processing, and they are targets for relevant physiologic and pharmacologic modulators. Several studies with protein crystallography and cryoelectron microscopy have shed light on the residues and mechanisms associated with the activation, blockade, and regulation of pentameric Cys-loop ion channels at the atomic level. Initial studies conducted on the extracellular domain of acetylcholine receptors, ion channels from prokaryote homologs-Erwinia chrysanthemi ligand-gated ion channel (ELIC), Gloeobacter violaceus ligand-gated ion channel (GLIC)-and crystallized eukaryotic receptors made it possible to define the overall structure and topology of the Cys-loop receptors. For example, the determination of pentameric GlyR structures bound to glycine and strychnine have contributed to visualizing the structural changes implicated in the transition between the open and closed states of the Cys-loop receptors. In this review, we summarize how the new information obtained in functional, mutagenesis, and structural studies have contributed to a better understanding of the function and regulation of GlyR.
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Affiliation(s)
- Carlos F Burgos
- Laboratory of Neurophysiology (C.F.B., L.G.A.), and Laboratory of Neuropharmacology (G.E.Y.), Department of Physiology, University of Concepción, Concepción, Chile
| | - Gonzalo E Yévenes
- Laboratory of Neurophysiology (C.F.B., L.G.A.), and Laboratory of Neuropharmacology (G.E.Y.), Department of Physiology, University of Concepción, Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology (C.F.B., L.G.A.), and Laboratory of Neuropharmacology (G.E.Y.), Department of Physiology, University of Concepción, Concepción, Chile
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17
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Acuña MA, Yévenes GE, Ralvenius WT, Benke D, Di Lio A, Lara CO, Muñoz B, Burgos CF, Moraga-Cid G, Corringer PJ, Zeilhofer HU. Phosphorylation state-dependent modulation of spinal glycine receptors alleviates inflammatory pain. J Clin Invest 2016; 126:2547-60. [PMID: 27270175 DOI: 10.1172/jci83817] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 04/14/2016] [Indexed: 01/10/2023] Open
Abstract
Diminished inhibitory neurotransmission in the superficial dorsal horn of the spinal cord is thought to contribute to chronic pain. In inflammatory pain, reductions in synaptic inhibition occur partially through prostaglandin E2- (PGE2-) and PKA-dependent phosphorylation of a specific subtype of glycine receptors (GlyRs) that contain α3 subunits. Here, we demonstrated that 2,6-di-tert-butylphenol (2,6-DTBP), a nonanesthetic propofol derivative, reverses inflammation-mediated disinhibition through a specific interaction with heteromeric αβGlyRs containing phosphorylated α3 subunits. We expressed mutant GlyRs in HEK293T cells, and electrophysiological analyses of these receptors showed that 2,6-DTBP interacted with a conserved phenylalanine residue in the membrane-associated stretch between transmembrane regions 3 and 4 of the GlyR α3 subunit. In native murine spinal cord tissue, 2,6-DTBP modulated synaptic, presumably αβ heteromeric, GlyRs only after priming with PGE2. This observation is consistent with results obtained from molecular modeling of the α-β subunit interface and suggests that in α3βGlyRs, the binding site is accessible to 2,6-DTBP only after PKA-dependent phosphorylation. In murine models of inflammatory pain, 2,6-DTBP reduced inflammatory hyperalgesia in an α3GlyR-dependent manner. Together, our data thus establish that selective potentiation of GlyR function is a promising strategy against chronic inflammatory pain and that, to our knowledge, 2,6-DTBP has a unique pharmacological profile that favors an interaction with GlyRs that have been primed by peripheral inflammation.
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18
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Boulton S, Melacini G. Advances in NMR Methods To Map Allosteric Sites: From Models to Translation. Chem Rev 2016; 116:6267-304. [PMID: 27111288 DOI: 10.1021/acs.chemrev.5b00718] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The last five years have witnessed major developments in the understanding of the allosteric phenomenon, broadly defined as coupling between remote molecular sites. Such advances have been driven not only by new theoretical models and pharmacological applications of allostery, but also by progress in the experimental approaches designed to map allosteric sites and transitions. Among these techniques, NMR spectroscopy has played a major role given its unique near-atomic resolution and sensitivity to the dynamics that underlie allosteric couplings. Here, we highlight recent progress in the NMR methods tailored to investigate allostery with the goal of offering an overview of which NMR approaches are best suited for which allosterically relevant questions. The picture of the allosteric "NMR toolbox" is provided starting from one of the simplest models of allostery (i.e., the four-state thermodynamic cycle) and continuing to more complex multistate mechanisms. We also review how such an "NMR toolbox" has assisted the elucidation of the allosteric molecular basis for disease-related mutations and the discovery of novel leads for allosteric drugs. From this overview, it is clear that NMR plays a central role not only in experimentally validating transformative theories of allostery, but also in tapping the full translational potential of allosteric systems.
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Affiliation(s)
- Stephen Boulton
- Department of Chemistry and Chemical Biology Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main St. W., Hamilton L8S 4M1, Canada
| | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology Department of Biochemistry and Biomedical Sciences, McMaster University , 1280 Main St. W., Hamilton L8S 4M1, Canada
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19
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Pentameric quaternary structure of the intracellular domain of serotonin type 3A receptors. Sci Rep 2016; 6:23921. [PMID: 27045630 PMCID: PMC4820698 DOI: 10.1038/srep23921] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 03/15/2016] [Indexed: 01/02/2023] Open
Abstract
In spite of extensive efforts over decades an experimentally-derived structure of full-length eukaryotic pentameric ligand-gated ion channels (pLGICs) is still lacking. These pharmaceutically highly-relevant channels contain structurally well-conserved and characterized extracellular and transmembrane domains. The intracellular domain (ICD), however, has been orphaned in structural studies based on the consensus assumption of being largely disordered. In the present study, we demonstrate for the first time that the serotonin type 3A (5-HT3A) ICD assembles into stable pentamers in solution in the absence of the other two domains, thought to be the drivers for oligomerization. Additionally, the soluble 5-HT3A-ICD construct interacted with the protein RIC-3 (resistance to inhibitors of cholinesterase). The interaction provides evidence that the 5-HT3A-ICD is not only required but also sufficient for interaction with RIC-3. Our results suggest the ICD constitutes an oligomerization domain. This novel role significantly adds to its known contributions in receptor trafficking, targeting, and functional fine-tuning. The innate diversity of the ICDs with sizes ranging from 50 to 280 amino acids indicates new methodologies need to be developed to determine the structures of these domains. The use of soluble ICD proteins that we report in the present study constitutes a useful approach to address this gap.
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20
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Chowdhury L, Croft CJ, Goel S, Zaman N, Tai ACS, Walch EM, Smith K, Page A, Shea KM, Hall CD, Jishkariani D, Pillai GG, Hall AC. Differential Potency of 2,6-Dimethylcyclohexanol Isomers for Positive Modulation of GABAA Receptor Currents. J Pharmacol Exp Ther 2016; 357:570-9. [PMID: 27029583 DOI: 10.1124/jpet.115.228890] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 03/22/2016] [Indexed: 11/22/2022] Open
Abstract
GABAA receptors meet all of the pharmacological requirements necessary to be considered important targets for the action of general anesthetic agents in the mammalian brain. In the following patch-clamp study, the relative modulatory effects of 2,6-dimethylcyclohexanol diastereomers were investigated on human GABAA (α1β3γ2s) receptor currents stably expressed in human embryonic kidney cells. Cis,cis-, trans,trans-, and cis,trans-isomers were isolated from commercially available 2,6-dimethylcyclohexanol and were tested for positive modulation of submaximal GABA responses. For example, the addition of 30 μM cis,cis-isomer resulted in an approximately 2- to 3-fold enhancement of the EC20 GABA current. Coapplications of 30 μM 2,6-dimethylcyclohexanol isomers produced a range of positive enhancements of control GABA responses with a rank order for positive modulation: cis,cis > trans,trans ≥ mixture of isomers > > cis,trans-isomer. In molecular modeling studies, the three cyclohexanol isomers bound with the highest binding energies to a pocket within transmembrane helices M1 and M2 of the β3 subunit through hydrogen-bonding interactions with a glutamine at the 224 position and a tyrosine at the 220 position. The energies for binding to and hydrogen-bond lengths within this pocket corresponded with the relative potencies of the agents for positive modulation of GABAA receptor currents (cis,cis > trans,trans > cis,trans-2,6-dimethylcyclohexanol). In conclusion, the stereochemical configuration within the dimethylcyclohexanols is an important molecular feature in conferring positive modulation of GABAA receptor activity and for binding to the receptor, a consideration that needs to be taken into account when designing novel anesthetics with enhanced therapeutic indices.
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Affiliation(s)
- Luvana Chowdhury
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Celine J Croft
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Shikha Goel
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Naina Zaman
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Angela C-S Tai
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Erin M Walch
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Kelly Smith
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Alexandra Page
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Kevin M Shea
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - C Dennis Hall
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - D Jishkariani
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Girinath G Pillai
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
| | - Adam C Hall
- Neuroscience Program, Departments of Biological Sciences (L.C., C.J.C., S.G., N.Z., A.C.-S.T., E.M.W., A.C.H.) and Chemistry (K.S., A.P., K.M.S.), Smith College, Northampton, Massachusetts; Department of Chemistry, University of Florida, Gainesville, Florida (C.D.H., D.J., G.G.P.); and Department of Chemistry, University of Tartu, Ravila, Estonia (G.G.P.)
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21
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NMR of Membrane Proteins: Beyond Crystals. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 922:29-42. [DOI: 10.1007/978-3-319-35072-1_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Snijder HJA, Hakulinen J. Membrane Protein Production in E. coli for Applications in Drug Discovery. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 896:59-77. [PMID: 27165319 DOI: 10.1007/978-3-319-27216-0_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Producing high quality purified membrane proteins for structure-based drug design and biophysical assays compatible with typical timelines in drug discovery is a significant challenge. Escherichia coli has been an expression host of the utmost importance for soluble proteins and has applications for membrane proteins as well. However, membrane protein overexpression in E. coli may lead to toxicity and low yields of functional product. Here, we review the challenges encountered with heterologous overproduction of α-helical membrane proteins in E. coli and a range of strategies to overcome them. A detailed protocol is also provided for expression and screening of membrane proteins in E. coli using a His-specific fluorescent probe and fluorescent size-exclusion chromatography.
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Affiliation(s)
| | - Jonna Hakulinen
- Discovery Sciences, AstraZeneca R&D, SE-43183, Mölndal, Sweden
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23
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Burgos CF, Muñoz B, Guzman L, Aguayo LG. Ethanol effects on glycinergic transmission: From molecular pharmacology to behavior responses. Pharmacol Res 2015; 101:18-29. [PMID: 26158502 DOI: 10.1016/j.phrs.2015.07.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/01/2015] [Accepted: 07/01/2015] [Indexed: 10/23/2022]
Abstract
It is well accepted that ethanol is able to produce major health and economic problems associated to its abuse. Because of its intoxicating and addictive properties, it is necessary to analyze its effect in the central nervous system. However, we are only now learning about the mechanisms controlling the modification of important membrane proteins such as ligand-activated ion channels by ethanol. Furthermore, only recently are these effects being correlated to behavioral changes. Current studies show that the glycine receptor (GlyR) is a susceptible target for low concentrations of ethanol (5-40mM). GlyRs are relevant for the effects of ethanol because they are found in the spinal cord and brain stem where they primarily express the α1 subunit. More recently, the presence of GlyRs was described in higher regions, such as the hippocampus and nucleus accumbens, with a prevalence of α2/α3 subunits. Here, we review data on the following aspects of ethanol effects on GlyRs: (1) direct interaction of ethanol with amino acids in the extracellular or transmembrane domains, and indirect mechanisms through the activation of signal transduction pathways; (2) analysis of α2 and α3 subunits having different sensitivities to ethanol which allows the identification of structural requirements for ethanol modulation present in the intracellular domain and C-terminal region; (3) Genetically modified knock-in mice for α1 GlyRs that have an impaired interaction with G protein and demonstrate reduced ethanol sensitivity without changes in glycinergic transmission; and (4) GlyRs as potential therapeutic targets.
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Affiliation(s)
- Carlos F Burgos
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Braulio Muñoz
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile
| | - Leonardo Guzman
- Laboratory of Molecular Neurobiology, Department of Physiology, University of Concepción, Chile
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Chile.
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24
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Horani S, Stater EP, Corringer PJ, Trudell JR, Harris RA, Howard RJ. Ethanol Modulation is Quantitatively Determined by the Transmembrane Domain of Human α1 Glycine Receptors. Alcohol Clin Exp Res 2015; 39:962-8. [PMID: 25973519 DOI: 10.1111/acer.12735] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 03/25/2015] [Indexed: 11/30/2022]
Abstract
BACKGROUND Mutagenesis and labeling studies have identified amino acids from the human α1 glycine receptor (GlyR) extracellular, transmembrane (TM), and intracellular domains in mediating ethanol (EtOH) potentiation. However, limited high-resolution structural data for physiologically relevant receptors in this Cys-loop receptor superfamily have made pinpointing the critical amino acids difficult. Homologous ion channels from lower organisms provide conserved models for structural and functional properties of Cys-loop receptors. We previously demonstrated that a single amino acid variant of the Gloeobacter violaceus ligand-gated ion channel (GLIC) produced EtOH and anesthetic sensitivity similar to that of GlyRs and provided crystallographic evidence for EtOH binding to GLIC. METHODS We directly compared EtOH modulation of the α1 GlyR and GLIC to a chimera containing the TM domain from human α1 GlyRs and the ligand-binding domain of GLIC using 2-electrode voltage-clamp electrophysiology of receptors expressed in Xenopus laevis oocytes. RESULTS EtOH potentiated α1 GlyRs in a concentration-dependent manner in the presence of zinc-chelating agents, but did not potentiate GLIC at pharmacologically relevant concentrations. The GLIC/GlyR chimera recapitulated the EtOH potentiation of GlyRs, without apparent sensitivity to zinc chelation. For chimera expression in oocytes, it was essential to suppress leakage current by adding 50 μM picrotoxin to the media, a technique that may have applications in expression of other ion channels. CONCLUSIONS Our results are consistent with a TM mechanism of EtOH modulation in Cys-loop receptors. This work highlights the relevance of bacterial homologs as valuable model systems for studying ion channel function of human receptors and demonstrates the modularity of these channels across species.
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Affiliation(s)
- Suzzane Horani
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas
| | - Evan P Stater
- Chemistry Department , Skidmore College, Saratoga Springs, New York
| | - Pierre-Jean Corringer
- Channel-Receptor Research Group , Pasteur Institute, Bâtiment Fernbach, Paris, France
| | - James R Trudell
- Department of Anesthesia , Stanford University School of Medicine, Stanford, California
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas
| | - Rebecca J Howard
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas.,Chemistry Department , Skidmore College, Saratoga Springs, New York
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25
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Kinde MN, Chen Q, Lawless MJ, Mowrey DD, Xu J, Saxena S, Xu Y, Tang P. Conformational Changes Underlying Desensitization of the Pentameric Ligand-Gated Ion Channel ELIC. Structure 2015; 23:995-1004. [PMID: 25960405 DOI: 10.1016/j.str.2015.03.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 03/24/2015] [Accepted: 03/30/2015] [Indexed: 11/18/2022]
Abstract
Structural rearrangements underlying functional transitions of pentameric ligand-gated ion channels (pLGICs) are not fully understood. Using (19)F nuclear magnetic resonance and electron spin resonance spectroscopy, we found that ELIC, a pLGIC from Erwinia chrysanthemi, expanded the extracellular end and contracted the intracellular end of its pore during transition from the resting to an apparent desensitized state. Importantly, the contraction at the intracellular end of the pore likely forms a gate to restrict ion transport in the desensitized state. This gate differs from the hydrophobic gate present in the resting state. Conformational changes of the TM2-TM3 loop were limited to the N-terminal end. The TM4 helices and the TM3-TM4 loop appeared relatively insensitive to agonist-mediated structural rearrangement. These results indicate that conformational changes accompanying functional transitions are not uniform among different ELIC regions. This work also revealed the co-existence of multiple conformations for a given state and suggested asymmetric conformational arrangements in a homomeric pLGIC.
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Affiliation(s)
- Monica N Kinde
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Qiang Chen
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Matthew J Lawless
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - David D Mowrey
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Department of Computational & Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Jiawei Xu
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Yan Xu
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA; Department of Computational & Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA.
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26
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Talwar S, Lynch JW. Investigating ion channel conformational changes using voltage clamp fluorometry. Neuropharmacology 2015; 98:3-12. [PMID: 25839896 DOI: 10.1016/j.neuropharm.2015.03.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/12/2015] [Accepted: 03/17/2015] [Indexed: 11/26/2022]
Abstract
Ion channels are membrane proteins whose functions are governed by conformational changes. The widespread distribution of ion channels, coupled with their involvement in most physiological and pathological processes and their importance as therapeutic targets, renders the elucidation of these conformational mechanisms highly compelling from a drug discovery perspective. Thanks to recent advances in structural biology techniques, we now have high-resolution static molecular structures for members of the major ion channel families. However, major questions remain to be resolved about the conformational states that ion channels adopt during activation, drug modulation and desensitization. Patch-clamp electrophysiology has long been used to define ion channel conformational states based on functional criteria. It achieves this by monitoring conformational changes at the channel gate and cannot detect conformational changes occurring in regions distant from the gate. Voltage clamp fluorometry involves labelling cysteines introduced into domains of interest with environmentally sensitive fluorophores and inferring structural rearrangements from voltage or ligand-induced fluorescence changes. Ion channel currents are monitored simultaneously to verify the conformational status. By defining real time conformational changes in domains distant from the gate, this technique provides unexpected new insights into ion channel structure and function. This review aims to summarise the methodology and highlight recent innovative applications of this powerful technique. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'.
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Affiliation(s)
- Sahil Talwar
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joseph W Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia; School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
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27
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Wells MM, Tillman TS, Mowrey DD, Sun T, Xu Y, Tang P. Ensemble-based virtual screening for cannabinoid-like potentiators of the human glycine receptor α1 for the treatment of pain. J Med Chem 2015; 58:2958-2966. [PMID: 25790278 DOI: 10.1021/jm501873p] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The human glycine receptors (hGlyRs) are chloride-selective ion channels that mediate inhibitory neurotransmission in the brain stem and spinal cord. They are also targets for compounds of potential use in analgesic therapies. Here, we develop a strategy to discover analgesic drugs via structure-based virtual screening based on the recently published NMR structure of the hGlyR-α1 transmembrane domain (PDB ID: 2M6I ) and the critical role of residue S296 in hGlyR-α1 potentiation by Δ(9)-tetrahydrocannabinol (THC). We screened 1549 FDA-approved drugs in the DrugBank database on an ensemble of 180 hGlyR-α1 structures generated from molecular dynamics simulations of the NMR structure of the hGlyR-α1 transmembrane domain in different lipid environments. Thirteen hit compounds from the screening were selected for functional validation in Xenopus laevis oocytes expressing hGlyR-α1. Only one compound showed no potentiation effects; seven potentiated hGlyR-α1 at a level greater than THC at 1 μM. Our virtual screening protocol is generally applicable to drug targets with lipid-facing binding sites.
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Affiliation(s)
- Marta M Wells
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Tommy S Tillman
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - David D Mowrey
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Tianmo Sun
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Yan Xu
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261.,Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh, Pittsburgh, PA 15261.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15261.,Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261
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28
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Allosteric and hyperekplexic mutant phenotypes investigated on an α1 glycine receptor transmembrane structure. Proc Natl Acad Sci U S A 2015; 112:2865-70. [PMID: 25730860 DOI: 10.1073/pnas.1417864112] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The glycine receptor (GlyR) is a pentameric ligand-gated ion channel (pLGIC) mediating inhibitory transmission in the nervous system. Its transmembrane domain (TMD) is the target of allosteric modulators such as general anesthetics and ethanol and is a major locus for hyperekplexic congenital mutations altering the allosteric transitions of activation or desensitization. We previously showed that the TMD of the human α1GlyR could be fused to the extracellular domain of GLIC, a bacterial pLGIC, to form a functional chimera called Lily. Here, we overexpress Lily in Schneider 2 insect cells and solve its structure by X-ray crystallography at 3.5 Å resolution. The TMD of the α1GlyR adopts a closed-channel conformation involving a single ring of hydrophobic residues at the center of the pore. Electrophysiological recordings show that the phenotypes of key allosteric mutations of the α1GlyR, scattered all along the pore, are qualitatively preserved in this chimera, including those that confer decreased sensitivity to agonists, constitutive activity, decreased activation kinetics, or increased desensitization kinetics. Combined structural and functional data indicate a pore-opening mechanism for the α1GlyR, suggesting a structural explanation for the effect of some key hyperekplexic allosteric mutations. The first X-ray structure of the TMD of the α1GlyR solved here using GLIC as a scaffold paves the way for mechanistic investigation and design of allosteric modulators of a human receptor.
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29
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Yu R, Hurdiss E, Greiner T, Lape R, Sivilotti L, Biggin PC. Agonist and antagonist binding in human glycine receptors. Biochemistry 2014; 53:6041-51. [PMID: 25184435 DOI: 10.1021/bi500815f] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The human glycine receptor (hGlyR) is an anion-permeable ligand-gated channel that is part of a larger superfamily of receptors called the Cys-loop family. hGlyRs are particularly amenable to single-channel recordings, thus making them a model experimental system for understanding the Cys-loop receptor family in general. Understanding the relationship between agonist binding and efficacy in Cys-loop receptors should improve our future prospects for making specific agonists or antagonists. However, at present, there is no high-resolution structure for the complete hGlyR, and thus, modeling is needed to provide a physical framework on which to interpret single-channel data. The structure of the glutamate-gated chloride channel from Caenorhabditis elegans shows a much higher level of sequence identity to human hGlyR than previous templates such as AChBP or the bacterial channels, GLIC and ELIC. Thus, we constructed a model of the hGlyR and validated it against previously reported mutagenesis data. We used molecular dynamics to refine the model and to explore binding of both an agonist (glycine) and an antagonist (strychnine). The model shows excellent agreement with previous data but also suggests some unique features: (i) a water molecule that forms part of the binding site and allows us to account for some previous results that were difficult to reconcile, (ii) an interaction of the glycine agonist with S129, and (iii) an effect from E211, both of which we confirmed with new site-directed mutagenesis and patch clamp recordings. Finally, examination of the simulations suggests that strychnine binding induces movement to a conformational state distinct from the glycine-bound or apo state, not only within the ligand-binding domain but also in the transmembrane domain.
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Affiliation(s)
- Rilei Yu
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford , South Parks Road, Oxford OX1 3QU, United Kingdom
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30
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Crystallographic studies of pharmacological sites in pentameric ligand-gated ion channels. Biochim Biophys Acta Gen Subj 2014; 1850:511-23. [PMID: 24836522 DOI: 10.1016/j.bbagen.2014.05.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 12/18/2022]
Abstract
BACKGROUND Pentameric ligand-gated ion channels (pLGICs) mediate fast chemical transmission of nerve signals in the central and peripheral nervous system. On the functional side, these molecules respond to the binding of a neurotransmitter (glycine, GABA, acetylcholine or 5HT3) in the extracellular domain (ECD) by opening their ionotropic pore in the transmembrane domain (TMD). The response to the neurotransmitter binding can be modulated by several chemical compounds acting at topographically distinct sites, as documented by a large body of literature. Notably, these receptors are the target of several classes of world-wide prescribed drugs, including general anesthetics, smoking cessation aids, anxiolytics, anticonvulsants, muscle relaxants, hypnotics and anti-emetics. On the structural side recent progress has been made on the crystallization of pLGICs in its different allosteric states, especially pLGICs of bacterial origin. Therefore, structure-function relationships can now be discussed at the atomic level for pLGICs. SCOPE OF REVIEW This review focuses on the crystallographic structure of complexes of pLGICs with a number of ligands of pharmacological interest. First, we review structural data on two key functional aspects of these receptors: the agonist-induced activation and ion transport itself. The molecular understanding of both these functional aspects is important, as they are those that most pharmacological compounds target. Next, we describe modulation sites that have recently been documented by X-ray crystallography. Finally, we propose a simple geometric classification of all these pharmacological sites in pLGICs, based on icosahedrons. MAJOR CONCLUSIONS This review illustrates the wealth of structural insight gained by comparing all available structures of members of the pLGIC family to rationalize the pharmacology of structurally diverse drugs acting at topographically distinct sites. It will be highlighted how sites that had been described earlier using biochemical techniques can be rationalized using structural data. Surprisingly, the use of icosahedral symmetry allows to link together several modulation sites, in a way that was totally unanticipated. GENERAL SIGNIFICANCE Overall, understanding the interplay between the different modulation sites at the structural level should help the design of future drugs targeting pLGICs. This article is part of a Special Issue entitled structural biochemistry and biophysics of membrane proteins.
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31
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Mowrey DD, Kinde MN, Xu Y, Tang P. Atomistic insights into human Cys-loop receptors by solution NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:307-14. [PMID: 24680782 DOI: 10.1016/j.bbamem.2014.03.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 03/12/2014] [Accepted: 03/20/2014] [Indexed: 12/13/2022]
Abstract
Cys-loop receptors are pentameric ligand-gated ion channels (pLGICs) mediating fast neurotransmission in the central and peripheral nervous systems. They are important targets for many currently used clinical drugs, such as general anesthetics, and for allosteric modulators with potential therapeutic applications. Here, we provide an overview of advances in the use of solution NMR in structural and dynamic characterization of ion channels, particularly human Cys-loop receptors. We present challenges to overcome and realistic solutions for achieving high-resolution structural information for this family of receptors. We discuss how subtle structural differences among homologous channels define unique channel pharmacological properties and advocate the necessity to determine high-resolution structures for individual receptor subtypes. Finally, we describe drug binding to the TMDs of Cys-loop receptors identified by solution NMR and the associated dynamics changes relevant to channel functions.
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Affiliation(s)
- David D Mowrey
- Department of Anesthesiology, University of Pittsburgh School of Medicine, USA; Department of Computational & Systems Biology, University of Pittsburgh School of Medicine, USA
| | - Monica N Kinde
- Department of Anesthesiology, University of Pittsburgh School of Medicine, USA
| | - Yan Xu
- Department of Anesthesiology, University of Pittsburgh School of Medicine, USA; Department of Structural Biology, University of Pittsburgh School of Medicine, USA; Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, USA.
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, USA; Department of Computational & Systems Biology, University of Pittsburgh School of Medicine, USA; Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, USA.
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32
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Bondarenko V, Targowska-Duda KM, Jozwiak K, Tang P, Arias HR. Molecular interactions between mecamylamine enantiomers and the transmembrane domain of the human α4β2 nicotinic receptor. Biochemistry 2014; 53:908-18. [PMID: 24437521 PMCID: PMC3971955 DOI: 10.1021/bi400969x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
To characterize the binding sites of mecamylamine enantiomers on the transmembrane domain (TMD) of human (h) (α4)3(β2)2 and (α4)2(β2)3 nicotinic acetylcholine receptors (AChRs), we used nuclear magnetic resonance (NMR), molecular docking, and radioligand binding approaches. The interactions of (S)-(+)- and (R)-(-)-mecamylamine with several residues, determined by high-resolution NMR, within the hα4β2-TMD indicate different modes of binding at several luminal (L) and nonluminal (NL) sites. In general, the residues sensitive to each mecamylamine enantiomer are similar at both receptor stoichiometries. However, some differences were observed. The molecular docking experiments were crucial for delineating the location and orientation of each enantiomer in its binding site. In the (α4)2(β2)3-TMD, (S)-(+)-mecamylamine interacts with the L1 (i.e., between positions -3' and -5') and L2 (i.e., between positions 16' and 20') sites, whereas the β2-intersubunit (i.e., cytoplasmic end of two β2-TMDs) and α4/β2-intersubunit (i.e., cytoplasmic end of α4-TM1 and β2-TM3) sites are shared by both enantiomers. In the (α4)3(β2)2-TMD, both enantiomers bind with different orientations to the L1' (closer to ring 2') and α4-intrasubunit (i.e., at the cytoplasmic ends of α4-TM1 and α4-TM2) sites, but only (R)-(-)-mecamylamine interacts with the L2' (i.e., closer to ring 20') and α4-TM3-intrasubunit sites. Our findings are important because they provide, for the first time, a structural understanding of the allosteric modulation elicited by mecamylamine enantiomers at each hα4β2 stoichiometry. This advancement could be beneficial for the development of novel therapies for the treatment of several neurological disorders.
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Affiliation(s)
- Vasyl Bondarenko
- Department of Anesthesiology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15213, United States
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33
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Velisetty P, Chalamalasetti SV, Chakrapani S. Structural basis for allosteric coupling at the membrane-protein interface in Gloeobacter violaceus ligand-gated ion channel (GLIC). J Biol Chem 2013; 289:3013-25. [PMID: 24338475 DOI: 10.1074/jbc.m113.523050] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ligand binding at the extracellular domain of pentameric ligand-gated ion channels initiates a relay of conformational changes that culminates at the gate within the transmembrane domain. The interface between the two domains is a key structural entity that governs gating. Molecular events in signal transduction at the interface are poorly defined because of its intrinsically dynamic nature combined with functional modulation by membrane lipid and water vestibules. Here we used electron paramagnetic resonance spectroscopy to delineate protein motions underlying Gloeobacter violaceus ligand-gated ion channel gating in a membrane environment and report the interface conformation in the closed and the desensitized states. Extensive intrasubunit interactions were observed in the closed state that are weakened upon desensitization and replaced by newer intersubunit contacts. Gating involves major rearrangements of the interfacial loops, accompanied by reorganization of the protein-lipid-water interface. These structural changes may serve as targets for modulation of gating by lipids, alcohols, and amphipathic drug molecules.
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Affiliation(s)
- Phanindra Velisetty
- From the Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4970
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34
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Mowrey DD, Liu Q, Bondarenko V, Chen Q, Seyoum E, Xu Y, Wu J, Tang P. Insights into distinct modulation of α7 and α7β2 nicotinic acetylcholine receptors by the volatile anesthetic isoflurane. J Biol Chem 2013; 288:35793-800. [PMID: 24194515 PMCID: PMC3861630 DOI: 10.1074/jbc.m113.508333] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/16/2013] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are targets of general anesthetics, but functional sensitivity to anesthetic inhibition varies dramatically among different subtypes of nAChRs. Potential causes underlying different functional responses to anesthetics remain elusive. Here we show that in contrast to the α7 nAChR, the α7β2 nAChR is highly susceptible to inhibition by the volatile anesthetic isoflurane in electrophysiology measurements. Isoflurane-binding sites in β2 and α7 were found at the extracellular and intracellular end of their respective transmembrane domains using NMR. Functional relevance of the identified β2 site was validated via point mutations and subsequent functional measurements. Consistent with their functional responses to isoflurane, β2 but not α7 showed pronounced dynamics changes, particularly for the channel gate residue Leu-249(9'). These results suggest that anesthetic binding alone is not sufficient to generate functional impact; only those sites that can modulate channel dynamics upon anesthetic binding will produce functional effects.
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Affiliation(s)
- David D. Mowrey
- From the Departments of Anesthesiology
- Computational and Systems Biology, and
| | - Qiang Liu
- the Division of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013
| | | | | | | | - Yan Xu
- From the Departments of Anesthesiology
- Structural Biology
- Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
| | - Jie Wu
- the Division of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013
| | - Pei Tang
- From the Departments of Anesthesiology
- Computational and Systems Biology, and
- Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260 and
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