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Bregestovski PD, Ponomareva DN. Photochromic Modulation of Cys-loop
Ligand-gated Ion Channels. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021020162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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2
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Jung JH, Kim SJ. Anxiolytic Action of Taurine via Intranasal Administration in Mice. Biomol Ther (Seoul) 2019; 27:450-456. [PMID: 30917626 PMCID: PMC6720536 DOI: 10.4062/biomolther.2018.218] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/20/2019] [Accepted: 02/20/2019] [Indexed: 02/02/2023] Open
Abstract
Taurine has a number of beneficial pharmacological actions in the brain such as anxiolytic and neuroprotective actions. We explored to test whether taurine could be transported to the central nervous system through the intranasal route. Following intranasal administration of taurine in mice, elevated plus maze test, activity cage test and rota rod test were carried out to verify taurine's effect on anxiety. For the characterization of potential mechanism of taurine's anti-anxiety action, mouse convulsion tests with strychnine, picrotoxin, yohimbine, and isoniazid were employed. A significant increase in the time spent in the open arms was observed when taurine was administered through the nasal route in the elevated plus maze test. In addition, vertical and horizontal activities of mice treated with taurine via intranasal route were considerably diminished. These results support the hypothesis that taurine can be transported to the brain through intranasal route, thereby inducing anti-anxiety activity. Taurine's anti-anxiety action may be mediated by the strychnine-sensitive glycine receptor as evidenced by the inhibition of strychnine-induced convulsion.
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Affiliation(s)
- Jung Hwa Jung
- Department of Pharmacology and Toxicology and Metabolic Diseases Research Laboratory, School of Dentistry, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Sung-Jin Kim
- Department of Pharmacology and Toxicology and Metabolic Diseases Research Laboratory, School of Dentistry, Kyung Hee University, Seoul 02447, Republic of Korea
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3
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Kumar R, Khandelwal N, Thachamvally R, Tripathi BN, Barua S, Kashyap SK, Maherchandani S, Kumar N. Role of MAPK/MNK1 signaling in virus replication. Virus Res 2018; 253:48-61. [PMID: 29864503 PMCID: PMC7114592 DOI: 10.1016/j.virusres.2018.05.028] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 04/16/2018] [Accepted: 05/31/2018] [Indexed: 12/23/2022]
Abstract
Viruses are known to exploit cellular signaling pathways. MAPK is a major cell signaling pathway activated by diverse group of viruses. MNK1 regulates both cap-dependent and IRES-mediated mRNA translation. This review discuss the role of MAPK, particularly the role of MNK1 in virus replication.
Viruses are obligate intracellular parasites; they heavily depend on the host cell machinery to effectively replicate and produce new progeny virus particles. Following viral infection, diverse cell signaling pathways are initiated by the cells, with the major goal of establishing an antiviral state. However, viruses have been shown to exploit cellular signaling pathways for their own effective replication. Genome-wide siRNA screens have also identified numerous host factors that either support (proviral) or inhibit (antiviral) virus replication. Some of the host factors might be dispensable for the host but may be critical for virus replication; therefore such cellular factors may serve as targets for development of antiviral therapeutics. Mitogen activated protein kinase (MAPK) is a major cell signaling pathway that is known to be activated by diverse group of viruses. MAPK interacting kinase 1 (MNK1) has been shown to regulate both cap-dependent and internal ribosomal entry sites (IRES)-mediated mRNA translation. In this review we have discuss the role of MAPK in virus replication, particularly the role of MNK1 in replication and translation of viral genome.
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Affiliation(s)
- Ram Kumar
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India; Department of Veterinary Microbiology and Biotechnology, Rajasthan University of Veterinary and Animal Sciences, Bikaner, Rajasthan 334001, India
| | - Nitin Khandelwal
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India
| | - Riyesh Thachamvally
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India
| | - Bhupendra Nath Tripathi
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India
| | - Sanjay Barua
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India
| | - Sudhir Kumar Kashyap
- Department of Veterinary Microbiology and Biotechnology, Rajasthan University of Veterinary and Animal Sciences, Bikaner, Rajasthan 334001, India
| | - Sunil Maherchandani
- Department of Veterinary Microbiology and Biotechnology, Rajasthan University of Veterinary and Animal Sciences, Bikaner, Rajasthan 334001, India
| | - Naveen Kumar
- Virology Laboratory, National Centre for Veterinary Type Cultures, ICAR-National Research Centre on Equines, Hisar, Haryana 125001, India.
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4
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Gorini G, Adron Harris R, Dayne Mayfield R. Proteomic approaches and identification of novel therapeutic targets for alcoholism. Neuropsychopharmacology 2014; 39:104-30. [PMID: 23900301 PMCID: PMC3857647 DOI: 10.1038/npp.2013.182] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 01/01/2023]
Abstract
Recent studies have shown that gene regulation is far more complex than previously believed and does not completely explain changes at the protein level. Therefore, the direct study of the proteome, considerably different in both complexity and dynamicity to the genome/transcriptome, has provided unique insights to an increasing number of researchers. During the past decade, extraordinary advances in proteomic techniques have changed the way we can analyze the composition, regulation, and function of protein complexes and pathways underlying altered neurobiological conditions. When combined with complementary approaches, these advances provide the contextual information for decoding large data sets into meaningful biologically adaptive processes. Neuroproteomics offers potential breakthroughs in the field of alcohol research by leading to a deeper understanding of how alcohol globally affects protein structure, function, interactions, and networks. The wealth of information gained from these advances can help pinpoint relevant biomarkers for early diagnosis and improved prognosis of alcoholism and identify future pharmacological targets for the treatment of this addiction.
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Affiliation(s)
- Giorgio Gorini
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA
| | - R Dayne Mayfield
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, USA
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5
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Samways DSK. Applications for mass spectrometry in the study of ion channel structure and function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 806:237-61. [PMID: 24952185 DOI: 10.1007/978-3-319-06068-2_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Ion channels are intrinsic membrane proteins that form gated ion-permeable pores across biological membranes. Depending on the type, ion channels exhibit sensitivities to a diverse range of stimuli including changes in membrane potential, binding by diffusible ligands, changes in temperature and direct mechanical force. The purpose of these proteins is to facilitate the passive diffusion of ions down their respective electrochemical gradients into and out of the cell, and between intracellular compartments. In doing so, ion channels can affect transmembrane potentials and regulate the intracellular homeostasis of the important second messenger, Ca(2+). The ion channels of the plasma membrane are of particular clinical interest due to their regulation of cell excitability and cytosolic Ca(2+) levels, and the fact that they are most amenable to manipulation by exogenously applied drugs and toxins. A critical step in improving the pharmacopeia of chemicals available that influence the activity of ion channels is understanding how their three-dimensional structure imparts function. Here, progress has been slow relative to that for soluble protein structures in large part due to the limitations of applying conventional structure determination methods, such as X-ray crystallography, nuclear magnetic resonance imaging, and mass spectrometry, to membrane proteins. Although still an underutilized technique in the assessment of membrane protein structure, recent advances have pushed mass spectrometry to the fore as an important complementary approach to studying the structure and function of ion channels. In addition to revealing the subtle conformational changes in ion channel structure that accompany gating and permeation, mass spectrometry is already being used effectively for identifying tissue-specific posttranslational modifications and mRNA splice variants. Furthermore, the use of mass spectrometry for high-throughput proteomics analysis, which has proven so successful for soluble proteins, is already providing valuable insight into the functional interactions of ion channels within the context of the macromolecular-signaling complexes that they inhabit in vivo. In this chapter, the potential for mass spectrometry as a complementary approach to the study of ion channel structure and function will be reviewed with examples of its application.
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Affiliation(s)
- Damien S K Samways
- Department of Biology, Clarkson University, 8 Clarkson Avenue, Potsdam, NY, 13699, USA,
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6
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Cheng L, Cao D. Designing a thermo-switchable channel for nanofluidic controllable transportation. ACS NANO 2011; 5:1102-1108. [PMID: 21214172 DOI: 10.1021/nn102754g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Owing to the important roles of chemical gates in biological systems, the biomimetic design of artificial switchable nanodevices has been attracting tremendous interest. Here, we design a cylindrical thermo-sensitive channel, in which nanofliudic transport properties can be controlled by manipulating environmental temperature. The switchable channel is formed by a polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS)-like triblock copolymer brush whose conformation and phase behavior are dependent on temperature. With the increase of temperature, the designed channel exhibits "close→open→close" behavior, which can serve as a kind of excellent switchable nanodevice for nanofluidic controllable transportation.
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Affiliation(s)
- Lisheng Cheng
- Division of Molecular and Materials Simulation, Key Lab for Nanomaterials, Ministry of Education, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China
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7
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Gregory ML, Guzauskas GF, Edgar TS, Clarkson KB, Srivastava AK, Holden KR. A novel GLRA1 mutation associated with an atypical hyperekplexia phenotype. J Child Neurol 2008; 23:1433-8. [PMID: 19073849 DOI: 10.1177/0883073808320754] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hyperekplexia (MIM #149400) is a rare neurological disorder characterized by an exaggerated startle response, infantile hypertonia and hyperreflexia without spasticity, a hesitant gait that usually improves by 3 years of age, and nocturnal myoclonus. Familial hyperekplexia is usually autosomal dominant resulting from mutations in the inhibitory glycine receptor subunit alpha 1 (GLRA1) gene on chromosome 5q. We identified a 3-generation family with progressively severe phenotypes of hyperekplexia. All affected family members were found to be heterozygous for a novel arginine271proline mutation in GLRA1. Long-term follow-up of the affected members of the third generation, now aged 6 and 7 years, reveals enhanced startle responses and persistent hypertonia of the extremities without clonus or a catch, tight heel cords and abnormal toe-walking gait, and plantar flexor reflexes. The 7-year-old child recently reponded well to a benzodiazepine. Future studies are warranted to examine whether this new missense mutation is solely responsible for this atypical phenotype.
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Affiliation(s)
- Mary L Gregory
- J.C. Self Research Institute of Human Genetics, Greenwood Genetic Center, Greenwood, South Carolina, USA
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8
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Dresbach T, Nawrotzki R, Kremer T, Schumacher S, Quinones D, Kluska M, Kuhse J, Kirsch J. Molecular architecture of glycinergic synapses. Histochem Cell Biol 2008; 130:617-33. [DOI: 10.1007/s00418-008-0491-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2008] [Indexed: 10/21/2022]
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9
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Lobo IA, Harris RA, Trudell JR. Cross-linking of sites involved with alcohol action between transmembrane segments 1 and 3 of the glycine receptor following activation. J Neurochem 2007; 104:1649-62. [PMID: 18036150 DOI: 10.1111/j.1471-4159.2007.05090.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The glycine receptor is a member of the Cys-loop, ligand-gated ion channel family and is responsible for inhibition in the CNS. We examined the orientation of amino acids I229 in transmembrane 1 (TM1) and A288 in TM3, which are both critical for alcohol and volatile anesthetic action. We mutated these two amino acids to cysteines either singly or in double mutants and expressed the receptors in Xenopus laevis oocytes. We tested whether disulfide bonds could form between A288C in TM3 paired with M227C, Y228C, I229C, or S231C in TM1. Application of cross-linking (mercuric chloride) or oxidizing (iodine) agents had no significant effect on the glycine response of wild-type receptors or the single mutants. In contrast, the glycine response of the I229C/A288C double mutant was diminished after application of either mercuric chloride or iodine only in the presence of glycine, indicating that channel gating causes I229C and A288C to fluctuate to be within 6 A apart and form a disulfide bond. Molecular modeling was used to thread the glycine receptor sequence onto a nicotinic acetylcholine receptor template, further demonstrating that I229 and A288 are near-neighbors that can cross-link and providing evidence that these residues contribute to a single binding cavity.
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Affiliation(s)
- Ingrid A Lobo
- Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712-1065, USA
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10
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Speranskiy K, Cascio M, Kurnikova M. Homology modeling and molecular dynamics simulations of the glycine receptor ligand binding domain. Proteins 2007; 67:950-60. [PMID: 17357155 PMCID: PMC2873197 DOI: 10.1002/prot.21251] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present a homology based model of the ligand binding domain (LBD) of the homopentameric alpha1 glycine receptor (GlyR). The model is based on multiple sequence alignment with other members of the nicotinicoid ligand gated ion channel superfamily and two homologous acetylcholine binding proteins (AChBP) from the freshwater (Lymnaea stagnalis) and saltwater (Aplysia californica) snails with known high resolution structure. Using two template proteins with known structure to model three dimensional structure of a target protein is especially advantageous for sequences with low homology as in the case presented in this paper. The final model was cross-validated by critical evaluation of experimental and published mutagenesis, functional and other biochemical studies. In addition, a complex structure with strychnine antagonist in the putative binding site is proposed based on docking simulation using Autodock program. Molecular dynamics (MD) simulations with simulated annealing protocol are reported on the proposed LBD of GlyR, which is stable in 5 ns simulation in water, as well as for a deformed LBD structure modeled on the corresponding domain determined in low-resolution cryomicroscopy structure of the alpha subunit of the full-length acetylcholine receptor (AChR). Our simulations demonstrate that the beta-sandwich central core of the protein monomer is fairly rigid in the simulations and resistant to deformations in water.
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Affiliation(s)
- Kirill Speranskiy
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Michael Cascio
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15261
| | - Maria Kurnikova
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
- Correspondence to: Maria Kurnikova, Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213.
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11
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Worsfold O, Voelcker NH, Nishiya T. Biosensing using lipid bilayers suspended on porous silicon. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:7078-83. [PMID: 16863263 DOI: 10.1021/la060121y] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We demonstrate for the first time the formation of a fluid lipid bilayer membrane on mesoporous silicon substrates for bioapplications. Using fluorescence recovery after photobleaching, the diffusion coefficients for the bilayers supported on oxidized, amino-, and biotin-functionalized mesoporous silicon were determined. The biodetection of a single human umbilical vein endothelial cell was accomplished using confocal microscopy and exploiting Foerster resonance energy transfer effects after the incorporation of RGD covalently linked lipid soluble dyes, with fluorescence donor and acceptor components, within the fluid membrane. A signal response of greater than 100% was achieved via the clustering of RGD peptides binding with areas of high integrin density on the surface of a single cell. These results are a testament to the usefulness of such functional molecular assemblies, based on mobile receptors, mimicking the cell membrane in the development of a new generation of biosensors.
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Affiliation(s)
- Oliver Worsfold
- Frontier Research Division, Fujirebio Inc., 51 Komiya-cho, Hachioji-shi, Tokyo 192-0031, Japan.
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12
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Abstract
Inhibition in the mature central nervous system is mediated by activation of gamma-aminobutyric acid (GABA(A)) and glycine receptors. Both receptors belong to the same superfamily of ligand-gated ion channels and share common transmembrane topology and structural and functional features. Glycine receptors are pentameric ligand-gated anion channels composed of two different subunits, named alpha und beta, that assemble with a fixed stoichiometric ratio of two alpha to three beta subunits. Four genes encoding the alpha subunits exist, whereas only one gene encoding the beta subunit has been detected. Ligand binding occurs at the interface of alpha and beta subunits. The beta subunit, which is unable to form homo-oligomeric receptors, is responsible for assembly and channel properties. Moreover, this subunit carries a binding motif for the cytoplasmic protein gephyrin, which is believed to mediate synaptic clustering and anchoring at inhibitory synapses by interacting with the subsynaptic cytoskeleton. Synaptic gephyrin appears to restrict the mobility of glycine receptors diffusing in the plane of the plasma membrane, thereby generating dynamic plasma membrane domains contributing to the plasticity of inhibitory synapses. Glycine receptors are well established as playing important roles in controlling motor functions and sensory signaling in vision and audition and those in the dorsal horn of the spinal cord are now considered to be new targets for pain therapies. Like GABA(A) receptors, glycine receptors have been shown to be depolarizing during development. The functional meaning of the developmental switch from excitatory to inhibitory glycine receptor action remains to be elucidated.
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Affiliation(s)
- Joachim Kirsch
- Institute for Anatomy and Cell Biology, Department of Medical Cell Biology, University of Heidelberg, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany.
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13
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Abstract
Ligand-gated ion channels, or ionotropic receptors, constitute a group of membrane-bound proteins that regulate the flux of ions across the cell membrane. In the brain, ligand-gated ion channels mediate fast neurotransmission. They are crucial for normal brain function and involved in many diseases in the brain. Historically, natural products have been used extensively in biomedical studies and ultimately as drugs or leads for drug design. In studies of ligand-gated ion channels, natural products have been essential for the understanding of their structure and function. In the following a short survey of natural products and their use in studies of ligand-gated ion channels is given.
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Affiliation(s)
- Kristian Strømgaard
- Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, DK-2100 Copenhagen, Denmark.
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14
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Lobo IA, Harris RA. Sites of alcohol and volatile anesthetic action on glycine receptors. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 65:53-87. [PMID: 16140053 DOI: 10.1016/s0074-7742(04)65003-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- Ingrid A Lobo
- Institute for Cellular and Molecular Biology, Waggoner Center for Alcohol and Addiction Research, Section of Neurobiology, University of Texas at Austin, Austin, Texas 78712, USA
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15
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Inoue K, Ueno S, Yamada J, Fukuda A. Characterization of newly cloned variant of rat glycine receptor α1 subunit. Biochem Biophys Res Commun 2005; 327:300-5. [PMID: 15629462 DOI: 10.1016/j.bbrc.2004.12.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2004] [Indexed: 11/25/2022]
Abstract
Responses to glycine, a major inhibitory neurotransmitter within the nervous system, are mediated by glycine receptors (GlyRs). Here, we report the cloning and analysis of a novel splicing variant of the GlyRalpha1 subunit. This variant, named GlyRalpha1del, has a truncated cytoplasmic region between transmembrane domains (TM)3 and TM4, and compared to other variants, the truncation is contributed by a different acceptor site in exon 9. We transfected GlyRalpha1 or GlyRalpha1del into HEK293 cells, and then examined the glycine-activated currents using a whole-cell patch-clamp recording technique. Maximal currents and current-voltage relationships showed no clear difference between GlyRalpha1del and GlyRalpha1. Moreover, dose-response curves indicated that the EC50 values for glycine differed significantly between the two GlyRalpha1 derivatives, although their Hill coefficients were similar. When present with other isoforms, GlyRalpha1del might alter the response to glycine or to other agonists, as this variant expands the potential heterogeneity among glycine receptors.
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Affiliation(s)
- Koichi Inoue
- Department of Physiology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan.
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16
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Bertaccini EJ, Shapiro J, Brutlag DL, Trudell JR. Homology Modeling of a Human Glycine Alpha 1 Receptor Reveals a Plausible Anesthetic Binding Site. J Chem Inf Model 2004; 45:128-35. [PMID: 15667138 DOI: 10.1021/ci0497399] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The superfamily of ligand-gated ion channels (LGICs) has been implicated in anesthetic and alcohol responses. Mutations within glycine and GABA receptors have demonstrated that possible sites of anesthetic action exist within the transmembrane subunits of these receptors. The exact molecular arrangement of this transmembrane region remains at intermediate resolution with current experimental techniques. Homology modeling methods were therefore combined with experimental data to produce a more exact model of this region. A consensus from multiple bioinformatics techniques predicted the topology within the transmembrane domain of a glycine alpha one receptor (GlyRa1) to be alpha helical. This fold information was combined with sequence information using the SeqFold algorithm to search for modeling templates. Independently, the FoldMiner algorithm was used to search for templates that had structural folds similar to published coordinates of the homologous nAChR (1OED). Both SeqFold and Foldminer identified the same modeling template. The GlyRa1 sequence was aligned with this template using multiple scoring criteria. Refinement of the alignment closed gaps to produce agreement with labeling studies carried out on the homologous receptors of the superfamily. Structural assignment and refinement was achieved using Modeler. The final structure demonstrated a cavity within the core of a four-helix bundle. Residues known to be involved in modulating anesthetic potency converge on and line this cavity. This suggests that the binding sites for volatile anesthetics in the LGICs are the cavities formed within the core of transmembrane four-helix bundles.
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Affiliation(s)
- Edward J Bertaccini
- Department of Anesthesia, Stanford University School of Medicine, Stanford, California 94305-5117, USA.
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17
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Saiz L, Klein ML. The transmembrane domain of the acetylcholine receptor: insights from simulations on synthetic peptide models. Biophys J 2004; 88:959-70. [PMID: 15556982 PMCID: PMC1305168 DOI: 10.1529/biophysj.104.049726] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have studied the structure and properties of a bundle of alpha-helical peptides embedded in a 1,2-dimyristoyl-3-phosphatidylcholine phospholipid bilayer by molecular dynamics simulations. The bundle of five transmembrane deltaM2 segments constitutes the model for the pore region of the nicotinic acetylcholine receptor, which is the neurotransmitter-gated ion-channel responsible for the fast propagation of electrical signals between cells at the nerve-muscle synapse. The deltaM2 segments were shown to oligomerize in biomembranes resulting in ion-channel activity with characteristics similar to the native protein, and the structure of the isolated peptides was studied in 1,2-dimyristoyl-3-phosphatidylcholine bilayers and micelles by NMR experiments (Opella, S. J., et al. 1999. Nat. Struct. Biol. 6:374-379). Our analyses indicate that the structure, helix tilt, and the overall shape of the channel are in good agreement with the NMR experiments and the proposed model for the channel, which we show is formed by rings of functional residues. The studied geometry resulted in a closed pore state, where the channel is partially dehydrated at the hydrophobic extracellular half and the extracellular mouth of the channel blocked by the hydrocarbon chains of Arg+ residues. The arginine amino acids form intermolecular salt-bridges with the C-terminus, which contribute as well to the bundle stabilization.
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Affiliation(s)
- Leonor Saiz
- Center for Molecular Modeling, Chemistry Department, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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18
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Abstract
The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning GlyR molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.
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Affiliation(s)
- Joseph W Lynch
- School of Biomedical Sciences, Univ. of Queensland, Brisbane QLD 4072, Australia.
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19
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Shi H, Tsang SY, Tse MK, Xu Z, Xue H. Recombinant extracellular domain of the three major subunits of GABAA receptor show comparable secondary structure and benzodiazepine binding properties. Protein Sci 2004; 12:2642-6. [PMID: 14573876 PMCID: PMC2366965 DOI: 10.1110/ps.03240203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The three most widely expressed subunits of the GABAA receptor are alpha(1), beta(2), and gamma(2) subunits, and the major isoform in the human brain is a pentameric receptor composed of 2alpha(1)2beta(2)1gamma(2). Previously, we overexpressed the extracellular domain Q28-R248 of GABAA receptor alpha(1) subunit. In the present study, the homologous extracellular domains Q25-G243 of GABAA receptor beta(2) subunit and Q40-G273 of gamma(2) subunit were also obtained through overexpression in Escherichia coli. Successful production of recombinant beta(2) and gamma(2) subunit receptor protein domains facilitates the comparison of structural and functional properties of the three subunits. To this end, the secondary structures of the three fragments were measured using CD spectroscopy and the beta-strand contents calculated to be >30%, indicating a beta-rich structure for all three fragments. In addition, the benzodiazepine (BZ)-binding affinity of the recombinant fragments were measured using fluorescence polarization to be 2.16 microM, 3.63 microM, and 1.34 microM for the alpha(1), beta(2), and gamma(2) subunit fragments, respectively, indicating that all three homomeric assemblies, including that of the beta(2) subunit, generally not associated with BZ binding, can bind BZ in the micromolar range. The finding that the BZ binding affinity of these recombinant domains was highest for the gamma(2) subunit and lowest for the beta(2) subunit is consistent with results from previous binding studies using hetero-oligomeric receptors. The present results exemplify the effective approach to characterize and compare the three major subunits of the GABAA receptor, for two of which the overexpression in E. coli is reported for the first time.
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Affiliation(s)
- Haifeng Shi
- Department of Biochemistry and Cooperative Center for Soluble Receptor Biology, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
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Strømgaard A, Jensen AA, Strømgaard K. Site-Specific Incorporation of Unnatural Amino Acids into Proteins. Chembiochem 2004; 5:909-16. [PMID: 15239046 DOI: 10.1002/cbic.200400060] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Anne Strømgaard
- Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
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Filippova N, Wotring VE, Weiss DS. Evidence that the TM1-TM2 Loop Contributes to the ρ1 GABA Receptor Pore. J Biol Chem 2004; 279:20906-14. [PMID: 15007065 DOI: 10.1074/jbc.m401012200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Considerable evidence indicates the second transmembrane domain (TM2) of the gamma-aminobutyric acid (GABA) receptor lines the integral ion pore. To further delineate the structures that constitute the ion pore and selectivity filter of the rho1 GABA receptor, we used the substituted cysteine accessibility method with charged reagents to identify anion- and cation-accessible surfaces. Twenty-one consecutive residues were mutated to cysteine, one at a time, in the presumed intracellular end of the first transmembrane domain (TM1; Ala(271)-Met(276)), the entire linker connecting TM1 to TM2 (Leu(277)-Arg(287)), and the presumed intracellular end of TM2 (Ala(288)-Ala(291)). Positively (MTSEA(+)) and negatively (pCMBS(-)) charged sulfhydryl reagents, as well as Cd(2+), were added extracellularly to test accessibility of the engineered cysteines. Four of the mutants, all at the intracellular end of TM2 (R287C, V289C, P290C, A291C), were accessible to positively charged reagents, whereas seven mutants (A271C, T272C, L277C, W279C, V280C, P290C, A291C) were functionally modified by negatively charged pCMBS(-). These seven modified residues were at the intracellular end of TM2, in the TM1-TM2 linker, and at the intracellular end of TM1. In nearly all cases (excluding P290C), the rate and the degree of modification were state-dependent, with greater accessibility in the presence of agonist. Select cysteine mutants were combined with a point mutation (A291E) that converted the pore from chloride- to non-selective. In this case, positively charged reagents could modify residues in the TM1-TM2 linker (Leu(277) and Val(280)), supporting the notion that the modifying reagents were reaching their target through the pore. Taken together, our results suggest that, up to its intracellular end, the TM2 domain is not charge selective. In addition, we propose that the TM1-TM2 linker and the intracellular end of TM1 are along the pathway of the permeating ion. These findings may lend new insights into the structure of the GABA receptor pore.
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Affiliation(s)
- Natalia Filippova
- Department of Neurobiology, University of Alabama at Birmingham School of Medicine, 1719 Sixth Avenue South, CIRC410, Birmingham, AL 35294, USA
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Cascio M. Structure and Function of the Glycine Receptor and Related Nicotinicoid Receptors. J Biol Chem 2004; 279:19383-6. [PMID: 15023997 DOI: 10.1074/jbc.r300035200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Michael Cascio
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Ivic L, Sands TTJ, Fishkin N, Nakanishi K, Kriegstein AR, Strømgaard K. Terpene Trilactones from Ginkgo biloba Are Antagonists of Cortical Glycine and GABAA Receptors. J Biol Chem 2003; 278:49279-85. [PMID: 14504293 DOI: 10.1074/jbc.m304034200] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glycine and gamma-aminobutyric acid, type A (GABA(A)) receptors are members of the ligand-gated ion channel superfamily that mediate inhibitory synaptic transmission in the adult central nervous system. During development, the activation of these receptors leads to membrane depolarization. Ligands for the two receptors have important implications both in disease therapy and as pharmacological tools. Terpene trilactones (ginkgolides and bilobalide) are unique constituents of Ginkgo biloba extracts that have various effects on the central nervous system. We have investigated the relative potency of these compounds on glycine and GABA(A) receptors. We find that most of the ginkgolides are selective and potent antagonists of the glycine receptor. Bilobalide, the single major component in G. biloba extracts, also reduces glycine-induced currents, although to a lesser extent. Both ginkgolides and bilobalide inhibit GABA(A) receptors, with bilobalide demonstrating a more potent effect. Additionally, we provide evidence that open channels are required for glycine receptor inhibition by ginkgolides. Finally, we employ molecular modeling to elucidate the similarities and differences in the structure of the terpene trilactones to account for the pharmacological properties of these compounds and demonstrate a striking similarity between ginkgolides and picrotoxinin, a GABA(A) and recombinant glycine alpha-homomeric receptor antagonist.
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Affiliation(s)
- Lidija Ivic
- Department of Neurology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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Cascio M. Glycine receptors: lessons on topology and structural effects of the lipid bilayer. Biopolymers 2003; 66:359-68. [PMID: 12539264 DOI: 10.1002/bip.10314] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The members of the superfamily of nicotinicoid receptors, sometimes referred to as the ligand-gated ion channel superfamily (LGICS), are essential mediators in the propagation of electrical signals between cells at neuronal and neuromuscular synapses. Given the significant sequence and proposed topological similarities between family members, the structural architecture of any one of these neuroreceptors is believed to be archetypic for the family of ligand-gated channels. We have focused our biophysical studies on the glycine receptor (GlyR) since homomeric expression of just the alpha1 chain of the receptor is sufficient to reconstitute native-like activity when expressed in heterologous cells, and we have successfully overexpressed and purified relatively large quantities of this receptor. Our CD data suggests that the historical four transmembrane helix topology model for nicotinicoid receptors may be erroneous. Proteolytic studies as well as chemical modification studies coupled with mass spectroscopy (MS) have provided additional evidence that this model may be inappropriate. While we suggest a novel topological model for the superfamily of nicotinicoid receptors, the absence of high resolution data for the transmembrane regions of these ion channels precludes further refinement of this model. In addition, we observe structural changes in the recombinant alpha1 GlyR as a function of bilayer composition, suggesting that these receptors may be dynamically modulated by cellular control over the properties of the plasma membrane.
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Affiliation(s)
- Michael Cascio
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Leite JF, Gribble B, Randolph N, Cascio M. In vitro interaction of the glycine receptor with the leptin receptor. Physiol Behav 2002; 77:565-9. [PMID: 12527000 DOI: 10.1016/s0031-9384(02)00912-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The coordination and regulation of electrical signals across excitable cells is a complex, dynamic phenomenon requiring, in part, the interaction of ion channels with cellular constituents. The intracellular loops or domains of many ion channel subunits have been shown to specifically bind other cellular components that act in receptor targeting, localization, regulation, or modulation of function. In this report we describe experiments in which the large intracellular loop of the alpha1 subunit of the glycine receptor (GlyR) was used as "bait" to search a human brain library for proteins that may interact with this receptor. The GlyR is the major inhibitory ligand-gated ion channel in the spinal cord and lower brainstem, and is a member of the nicotinicoid superfamily of receptors. These in vitro studies identified the leptin receptor as a potential binding partner for GlyR, and this interaction was confirmed in binding studies that used the cytoplasmic loop of the GlyR as an affinity ligand for homogenized tissue from rat spinal cords and lower brainstem. Mass spectrometric analyses of eluants showed that the leptin receptor was specifically extracted from the homogenized and solubilized tissue. The long form of the leptin receptor is expressed in the hypothalamus (as is the GlyR) and among its other functions, it quickly evokes a satiation response upon binding leptin. Our in vitro results suggest that this rapid initial response may be mediated through direct interaction of the leptin receptor with GlyR or a related nicotinicoid family member homolog.
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Affiliation(s)
- John F Leite
- Department of Molecular Genetics, University of Pittsburgh School of Medicine, 15261, Pittsburgh, PA, USA
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Spencer RH, Rees DC. The alpha-helix and the organization and gating of channels. ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE 2002; 31:207-33. [PMID: 11988468 DOI: 10.1146/annurev.biophys.31.082901.134329] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The structures of an increasing number of channels and other alpha-helical membrane proteins have been determined recently, including the KcsA potassium channel, the MscL mechanosensitive channel, and the AQP1 and GlpF members of the aquaporin family. In this chapter, the orientation and packing characteristics of bilayer-spanning helices are surveyed in integral membrane proteins. In the case of channels, alpha-helices create the sealed barrier that separates the hydrocarbon region of the bilayer from the permeation pathway for solutes. The helices surrounding the permeation pathway tend to be rather steeply tilted relative to the membrane normal and are consistently arranged in a right-handed bundle. The helical framework further provides a supporting scaffold for nonmembrane-spanning structures associated with channel selectivity. Although structural details remain scarce, the conformational changes associated with gating transitions between closed and open states of channels are reviewed, emphasizing the potential roles of helix-helix interactions in this process.
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Affiliation(s)
- Robert H Spencer
- Department of Pharmacology, Merck Research Laboratories, West Point, PA 19486.
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