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Stuebler AG, Jansen M. Mobility of Lower MA-Helices for Ion Conduction through Lateral Portals in 5-HT 3A Receptors. Biophys J 2020; 119:2593-2603. [PMID: 33157122 PMCID: PMC7822733 DOI: 10.1016/j.bpj.2020.10.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/19/2020] [Accepted: 10/27/2020] [Indexed: 01/22/2023] Open
Abstract
The intracellular domain of the serotonin type 3A receptor, a pentameric ligand-gated ion channel, is crucial for regulating conductance. Ion permeation through the extracellular vestibule and the transmembrane channel is well understood, whereas the specific ion conduction pathway through the intracellular domain is less clear. The intracellular domain starts with a short loop after the third transmembrane segment, followed by a short α-helical segment, a large unstructured loop, and finally, the membrane-associated MA-helix that continues into the last transmembrane segment. The MA-helices from all five subunits form the extension of the transmembrane ion channel and shape what has been described as a “closed vestibule,” with their lateral portals obstructed by loops and their cytosolic ends forming a tight hydrophobic constriction. The question remains whether the lateral portals or cytosolic constriction conduct ions upon channel opening. In our study, we used disulfide bond formation between pairs of engineered cysteines to probe the proximity and mobility of segments of the MA-helices most distal to the membrane bilayer. Our results indicate that the proximity and orientation for cysteine pairs at I409C/R410C, in close proximity to the lateral windows, and L402C/L403C, at the cytosolic ends of the MA-helices, are conducive for disulfide bond formation. Although conformational changes associated with gating promote cross-linking for I409C/R410C, which in turn decreases channel currents, cross-linking of L402C/L403C is functionally silent in macroscopic currents. These results support the hypothesis that concerted conformational changes open the lateral portals for ion conduction, rendering ion conduction through the vertical portal unlikely.
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Affiliation(s)
- 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, Texas
| | - 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, Texas.
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2
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Imaging of fluorescence anisotropy during photoswitching provides a simple readout for protein self-association. Nat Commun 2020; 11:21. [PMID: 31911590 PMCID: PMC6946710 DOI: 10.1038/s41467-019-13843-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 12/03/2019] [Indexed: 12/02/2022] Open
Abstract
Monitoring of protein oligomerization has benefited greatly from Förster Resonance Energy Transfer (FRET) measurements. Although donors and acceptors are typically fluorescent molecules with different spectra, homo-FRET can occur between fluorescent molecules of the same type if the emission spectrum overlaps with the absorption spectrum. Here, we describe homo-FRET measurements by monitoring anisotropy changes in photoswitchable fluorescent proteins while photoswitching to the off state. These offer the capability to estimate anisotropy in the same specimen during homo-FRET as well as non-FRET conditions. We demonstrate photoswitching anisotropy FRET (psAFRET) with a number of test chimeras and example oligomeric complexes inside living cells. We also present an equation derived from FRET and anisotropy equations which converts anisotropy changes into a factor we call delta r FRET (drFRET). This is analogous to an energy transfer efficiency and allows experiments performed on a given homo-FRET pair to be more easily compared across different optical configurations. Performing homo-FRET measurements in cells using a fluorescence microscope is challenging, especially when using high numerical aperture objective lenses. Here the authors present a method for improved homo-FRET measurements based on anisotropy changes in photoswitchable fluorescent proteins.
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3
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Liu JJ, Hezghia A, Shaikh SR, Cenido JF, Stark RE, Mann JJ, Sublette ME. Regulation of monoamine transporters and receptors by lipid microdomains: implications for depression. Neuropsychopharmacology 2018; 43:2165-2179. [PMID: 30022062 PMCID: PMC6135777 DOI: 10.1038/s41386-018-0133-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 05/24/2018] [Accepted: 06/18/2018] [Indexed: 12/16/2022]
Abstract
Lipid microdomains ("rafts") are dynamic, nanoscale regions of the plasma membrane enriched in cholesterol and glycosphingolipids, that possess distinctive physicochemical properties including higher order than the surrounding membrane. Lipid microdomain integrity is thought to affect neurotransmitter signaling by regulating membrane-bound protein signaling. Among the proteins potentially affected are monoaminergic receptors and transporters. As dysfunction of monoaminergic neurotransmission is implicated in major depressive disorder and other neuropsychiatric conditions, interactions with lipid microdomains may be of clinical importance. This systematic review evaluates what is known about the molecular relationships of monoamine transporter and receptor regulation to lipid microdomains. The PubMed/MeSH database was searched for original studies published in English through August 2017 concerning relationships between lipid microdomains and serotonin, dopamine and norepinephrine transporters and receptors. Fifty-seven publications were identified and assessed. Strong evidence implicates lipid microdomains in the regulation of serotonin and norepinephrine transporters; serotonin 1A, 2A, 3A, and 7A receptors; and dopamine D1 and β2 adrenergic receptors. Results were conflicting or more complex regarding lipid microdomain associations with the dopamine transporter, D2, D3, and D5 receptors; and negative with respect to β1 adrenergic receptors. Indirect evidence suggests that antidepressants, lipid-lowering drugs, and polyunsaturated fatty acids may exert effects on depression and suicide by altering the lipid milieu, thereby affecting monoaminergic transporter and receptor signaling. The lipid composition of membrane subdomains is involved in localization and trafficking of specific monoaminergic receptors and transporters. Elucidating precise mechanisms whereby lipid microdomains modulate monoamine neurotransmission in clinical contexts can have critical implications for pharmacotherapeutic targeting.
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Affiliation(s)
- Joanne J Liu
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Chestnut Hill Hospital, Philadelphia, PA, USA
| | - Adrienne Hezghia
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, The State University of New York, Buffalo, NY, USA
| | - Saame Raza Shaikh
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Joshua F Cenido
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Department of Psychiatry, Charles R. Drew University of Medicine and Science, Los Angeles, CA, USA
| | - Ruth E Stark
- Department of Chemistry and Biochemistry and CUNY Institute for Macromolecular Assemblies, The City College of New York, New York, NY, USA
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, USA
| | - J John Mann
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
- Department of Radiology, Columbia University, New York, NY, USA
| | - M Elizabeth Sublette
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA.
- Department of Psychiatry, Columbia University, New York, NY, USA.
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Daray FM, Mann JJ, Sublette ME. How lipids may affect risk for suicidal behavior. J Psychiatr Res 2018; 104:16-23. [PMID: 29920417 PMCID: PMC6102068 DOI: 10.1016/j.jpsychires.2018.06.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 05/30/2018] [Accepted: 06/08/2018] [Indexed: 01/06/2023]
Abstract
Suicide and nonfatal suicidal behaviors are major causes of mortality and morbidity worldwide. Variability in rates of suicide and suicidal behaviors within and between countries has been attributed to population and individual risk factors, including economic status and cultural differences, both of which can have suicide risk effects mediated through a variety of factors, of which perhaps the least understood is the role of diet. We therefore review the scientific literature concerning two major dietary lipid classes, cholesterol and polyunsaturated fatty acids (PUFAs), that have been associated with higher risk of suicide attempts and suicide. We consider potential mechanistic intermediates including serotonin transporters and receptors, toll-like receptors (TLRs), nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and peroxisome proliferator activated receptors (PPARs). Based on this review, we describe a theoretical model linking cholesterol and PUFA status to suicide risk, taking into account the effects of cholesterol-lowering interventions on PUFA balance, membrane lipid microdomains (rafts) as a nexus of interaction between cholesterol and omega-3 PUFAs, and downstream effects on serotonergic neurotransmission and specific inflammatory pathways.
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Affiliation(s)
- Federico M. Daray
- Institute of Pharmacology. School of Medicine. University of Buenos Aires, Paraguay 2155, piso 9, Ciudad Autónoma de Buenos Aires, Argentina, C1121ABG
| | - J. John Mann
- Department of Psychiatry, Columbia University, 1051 Riverside Drive, New York, NY 10032,Division of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, 1051 Riverside Drive, Unit 42, New York, NY 10032,Department of Radiology, Columbia University, 622 West 168th St, New York, NY 10032
| | - M. Elizabeth Sublette
- Department of Psychiatry, Columbia University, 1051 Riverside Drive, New York, NY 10032,Division of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, 1051 Riverside Drive, Unit 42, New York, NY 10032,To whom correspondence should be addressed: New York State Psychiatric Institute, 1051 Riverside Drive, Unit 42, New York, NY 10032, Tel: 646 774-7514, Fax: 646 774-7589,
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Di Maio D, Chandramouli B, Brancato G. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel. PLoS One 2015; 10:e0140258. [PMID: 26465896 PMCID: PMC4605793 DOI: 10.1371/journal.pone.0140258] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/12/2015] [Indexed: 11/29/2022] Open
Abstract
Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested.
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Affiliation(s)
- Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
| | | | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- * E-mail:
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Blanc E, Wagner P, Plaisier F, Schmitt M, Durroux T, Bourguignon JJ, Partiseti M, Dupuis E, Bihel F. Design and validation of a homogeneous time-resolved fluorescence cell-based assay targeting the ligand-gated ion channel 5-HT3A. Anal Biochem 2015; 484:105-12. [PMID: 25998104 DOI: 10.1016/j.ab.2015.03.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 03/16/2015] [Accepted: 03/24/2015] [Indexed: 11/29/2022]
Abstract
Ligand-gated ion channels (LGICs) are considered as attractive protein targets in the search for new therapeutic agents. Nowadays, this strategy involves the capability to screen large chemical libraries. We present a new Tag-lite ligand binding assay targeting LGICs on living cells. This technology combines the use of suicide enzyme tags fused to channels of interest with homogeneous time-resolved fluorescence (HTRF) as the detection readout. Using the 5-HT3 receptor as system model, we showed that the pharmacology of the HALO-5HT3 receptor was identical to that of the native receptor. After validation of the assay by using 5-HT3 agonists and antagonists of reference, a pilot screen enabled us to identify azelastine, a well-known histamine H1 antagonist, as a potent 5-HT3 antagonist. This interesting result was confirmed with electrophysiological experiments. The method described here is easy to implement and could be applicable for other LGICs, opening new ways for the screening of chemical libraries.
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Affiliation(s)
- Emilie Blanc
- Cisbio Bioassays, 30200 Codolet, France; Institut de Génomique Fonctionnelle, Département de Pharmacologie Moléculaire, CNRS UMR 5203, INSERM U661, Université Montpellier I et II, 34094 Montpellier Cedex 5, France
| | - Patrick Wagner
- Laboratoire d'Innovation Thérapeutique, Faculté de Pharmacie, UMR 7200 CNRS/Université de Strasbourg, 67401 Illkirch, France
| | - Fabrice Plaisier
- Sanofi R&D, Research Center of Vitry/Alfortville, 94403 Vitry-sur-Seine, France
| | - Martine Schmitt
- Laboratoire d'Innovation Thérapeutique, Faculté de Pharmacie, UMR 7200 CNRS/Université de Strasbourg, 67401 Illkirch, France
| | - Thierry Durroux
- Institut de Génomique Fonctionnelle, Département de Pharmacologie Moléculaire, CNRS UMR 5203, INSERM U661, Université Montpellier I et II, 34094 Montpellier Cedex 5, France
| | - Jean-Jacques Bourguignon
- Laboratoire d'Innovation Thérapeutique, Faculté de Pharmacie, UMR 7200 CNRS/Université de Strasbourg, 67401 Illkirch, France
| | - Michel Partiseti
- Sanofi R&D, Research Center of Vitry/Alfortville, 94403 Vitry-sur-Seine, France
| | | | - Frederic Bihel
- Laboratoire d'Innovation Thérapeutique, Faculté de Pharmacie, UMR 7200 CNRS/Université de Strasbourg, 67401 Illkirch, France.
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Lochner M, Thompson AJ. A review of fluorescent ligands for studying 5-HT3 receptors. Neuropharmacology 2015; 98:31-40. [PMID: 25892507 DOI: 10.1016/j.neuropharm.2015.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 04/01/2015] [Accepted: 04/07/2015] [Indexed: 12/19/2022]
Abstract
The use of fluorescence is a valuable and increasingly accessible means of probing the pharmacology and physiology of cells and their receptors. To date, the use of fluorescence-based methods for 5-HT3 receptor research has been quite limited and, although a variety of approaches have been described, these are broadly distributed throughout the literature. In this review we condense these findings into a single, accessible source of reference with the hope of promoting the use of these valuable molecular probes. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'.
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Affiliation(s)
- Martin Lochner
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
| | - Andrew J Thompson
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
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Liu JJ, Green P, John Mann J, Rapoport SI, Sublette ME. Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease. Brain Res 2015; 1597:220-46. [PMID: 25498862 PMCID: PMC4339314 DOI: 10.1016/j.brainres.2014.11.059] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/11/2014] [Accepted: 11/27/2014] [Indexed: 12/28/2022]
Abstract
Essential polyunsaturated fatty acids (PUFAs) have profound effects on brain development and function. Abnormalities of PUFA status have been implicated in neuropsychiatric diseases such as major depression, bipolar disorder, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder. Pathophysiologic mechanisms could involve not only suboptimal PUFA intake, but also metabolic and genetic abnormalities, defective hepatic metabolism, and problems with diffusion and transport. This article provides an overview of physiologic factors regulating PUFA utilization, highlighting their relevance to neuropsychiatric disease.
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Affiliation(s)
- Joanne J Liu
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA; New York Medical College, Valhalla, NY, USA
| | - Pnina Green
- Laboratory of Metabolic Research, Felsenstein Medical Research Center, Tel Aviv University, Petach Tikva, Israel
| | - J John Mann
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA; Department of Psychiatry, Columbia University, New York, NY, USA; Department of Radiology, Columbia University, New York, NY, USA
| | - Stanley I Rapoport
- Brain Physiology and Metabolism Section, Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, MD, USA
| | - M Elizabeth Sublette
- Department of Molecular Imaging & Neuropathology, New York State Psychiatric Institute, New York, NY, USA; Department of Psychiatry, Columbia University, New York, NY, USA.
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Kozuska JL, Paulsen IM, Belfield WJ, Martin IL, Cole DJ, Holt A, Dunn SMJ. Impact of intracellular domain flexibility upon properties of activated human 5-HT3 receptors. Br J Pharmacol 2014; 171:1617-28. [PMID: 24283776 PMCID: PMC3966743 DOI: 10.1111/bph.12536] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 09/09/2013] [Accepted: 09/14/2013] [Indexed: 12/20/2022] Open
Abstract
Background and Purpose It has been proposed that arginine residues lining the intracellular portals of the homomeric 5-HT3A receptor cause electrostatic repulsion of cation flow, accounting for a single-channel conductance substantially lower than that of the 5-HT3AB heteromer. However, comparison of receptor homology models for wild-type pentamers suggests that salt bridges in the intracellular domain of the homomer may impart structural rigidity, and we hypothesized that this rigidity could account for the low conductance. Experimental Approach Mutations were introduced into the portal region of the human 5-HT3A homopentamer, such that putative salt bridges were broken by neutralizing anionic partners. Single-channel and whole cell currents were measured in transfected tsA201 cells and in Xenopus oocytes respectively. Computational simulations of protein flexibility facilitated comparison of wild-type and mutant receptors. Key Results Single-channel conductance was increased substantially, often to wild-type heteromeric receptor values, in most 5-HT3A mutants. Conversely, introduction of arginine residues to the portal region of the heteromer, conjecturally creating salt bridges, decreased conductance. Gating kinetics varied significantly between different mutant receptors. EC50 values for whole-cell responses to 5-HT remained largely unchanged, but Hill coefficients for responses to 5-HT were usually significantly smaller in mutants. Computational simulations suggested increased flexibility throughout the protein structure as a consequence of mutations in the intracellular domain. Conclusions and Implications These data support a role for intracellular salt bridges in maintaining the quaternary structure of the 5-HT3 receptor and suggest a role for the intracellular domain in allosteric modulation of cooperativity and agonist efficacy. Linked Article This article is commented on by Vardy and Kenakin, pp. 1614–1616 of volume 171 issue 7. To view this commentary visit http://dx.doi.org/10.1111/bph.12550.
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Affiliation(s)
- J L Kozuska
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
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Carland JE, Cooper MA, Livesey MR, Hales TG, Peters JA, Lambert JJ. Mutagenic analysis of the intracellular portals of the human 5-HT3A receptor. J Biol Chem 2013; 288:31592-601. [PMID: 24030822 PMCID: PMC3814755 DOI: 10.1074/jbc.m113.503300] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 09/11/2013] [Indexed: 11/15/2022] Open
Abstract
Structural models of Cys-loop receptors based on homology with the Torpedo marmorata nicotinic acetylcholine receptor infer the existence of cytoplasmic portals within the conduction pathway framed by helical amphipathic regions (termed membrane-associated (MA) helices) of adjacent intracellular M3-M4 loops. Consistent with these models, two arginine residues (Arg(436) and Arg(440)) within the MA helix of 5-hydroxytryptamine type 3A (5-HT3A) receptors act singularly as rate-limiting determinants of single-channel conductance (γ). However, there is little conservation in primary amino acid sequences across the cytoplasmic loops of Cys-loop receptors, limiting confidence in the fidelity of this particular aspect of the 5-HT3A receptor model. We probed the majority of residues within the MA helix of the human 5-HT3A subunit using alanine- and arginine-scanning mutagenesis and the substituted cysteine accessibility method to determine their relative influences upon γ. Numerous residues, prominently those at the 435, 436, 439, and 440 positions, were found to markedly influence γ. This approach yielded a functional map of the 5-HT3A receptor portals, which agrees well with the homology model.
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MESH Headings
- Animals
- Cell Line
- Humans
- Models, Molecular
- Mutagenesis, Site-Directed
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Serotonin, 5-HT3/chemistry
- Receptors, Serotonin, 5-HT3/genetics
- Receptors, Serotonin, 5-HT3/metabolism
- Structural Homology, Protein
- Torpedo
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Affiliation(s)
- Jane E. Carland
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | - Michelle A. Cooper
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | - Matthew R. Livesey
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | - Tim G. Hales
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | - John A. Peters
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | - Jeremy J. Lambert
- From the Division of Neuroscience, Medical Research and Medical Education Institutes, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
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Zhang J, Xue F, Liu Y, Yang H, Wang X. The structural mechanism of the Cys-loop receptor desensitization. Mol Neurobiol 2013; 48:97-108. [PMID: 23397136 DOI: 10.1007/s12035-013-8420-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 01/30/2013] [Indexed: 11/25/2022]
Abstract
The cys-loop receptors are neurotransmitter-operated ion channels, which mediate fast synaptic transmission for communication between neurons. However, prolonged exposure to the neurotransmitter drives the receptor to a desensitization state, which plays an important role in shaping synaptic transmission. Much progress has been made through more than half a century's research since Katz and Thesleff first descried desensitization for muscle nicotinic acetylcholine receptor. In this review, we summarized recent research developments of receptor desensitization. Now, it has been identified that many parts of the receptor, such as the pore domain (including the hinge in the M2-M3 linker), the binding domain, the coupling region, and the intracellular domain, are all involved in the cys-loop receptor desensitization and that uncoupling between the amino-terminal domain and channel lining domain seems to play a central role in desensitization. This uncoupling is mainly governed by the balance between coupling strength and relative tightness of gating machinery and influenced by other parts of the receptor. Agonist binding induces conformational change to overcome the gating barrier to open the channel through the stressed coupling region, which is subsequently broken, causing receptor desensitization. With rapid advancement in structural biology of membrane receptors, final validation of this mechanism is expected to occur in the near future when the high-resolution structure of the desensitized state is available.
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Affiliation(s)
- Jianliang Zhang
- Beijing Institute of Brain Disorders, Capital Medical University, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Beijing Center of Neural Regeneration and Repair, Beijing Key Laboratory of Brain Major Disorders-State Key Lab Incubation Base, Beijing Neuroscience Disciplines, #10 Xitoutiao, Youanmenwai, Beijing, 100069, China.
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12
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McKinnon NK, Bali M, Akabas MH. Length and amino acid sequence of peptides substituted for the 5-HT3A receptor M3M4 loop may affect channel expression and desensitization. PLoS One 2012; 7:e35563. [PMID: 22539982 PMCID: PMC3335078 DOI: 10.1371/journal.pone.0035563] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 03/20/2012] [Indexed: 11/18/2022] Open
Abstract
5-HT3A receptors are pentameric neurotransmitter-gated ion channels in the Cys-loop receptor family. Each subunit contains an extracellular domain, four transmembrane segments (M1, M2, M3, M4) and a 115 residue intracellular loop between M3 and M4. In contrast, the M3M4 loop in prokaryotic homologues is <15 residues. To investigate the limits of M3M4 loop length and composition on channel function we replaced the 5-HT3A M3M4 loop with two to seven alanine residues (5-HT3A-An = 2–7). Mutants were expressed in Xenopus laevis oocytes and characterized using two electrode voltage clamp recording. All mutants were functional. The 5-HT EC50's were at most 5-fold greater than wild-type (WT). The desensitization rate differed significantly among the mutants. Desensitization rates for 5-HT3A-A2, 5-HT3A-A4, 5-HT3A-A6, and 5-HT3A-A7 were similar to WT. In contrast, 5-HT3A-A3 and 5-HT3A-A5 had desensitization rates at least an order of magnitude faster than WT. The one Ala loop construct, 5-HT3A-A1, entered a non-functional state from which it did not recover after the first 5-HT application. These results suggest that the large M3M4 loop of eukaryotic Cys-loop channels is not required for receptor assembly or function. However, loop length and amino acid composition can effect channel expression and desensitization. We infer that the cytoplasmic ends of the M3 and M4 segments may undergo conformational changes during channel gating and desensitization and/or the loop may influence the position and mobility of these segments as they undergo gating-induced conformational changes. Altering structure or conformational mobility of the cytoplasmic ends of M3 and M4 may be the basis by which phosphorylation or protein binding to the cytoplasmic loop alters channel function.
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Affiliation(s)
- Nicole K. McKinnon
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, United States of America
| | - Moez Bali
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, United States of America
| | - Myles H. Akabas
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, United States of America
- Departments of Neuroscience and Medicine, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York, United States of America
- * E-mail:
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Goyal R, Salahudeen AA, Jansen M. Engineering a prokaryotic Cys-loop receptor with a third functional domain. J Biol Chem 2011; 286:34635-42. [PMID: 21844195 DOI: 10.1074/jbc.m111.269647] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Prokaryotic members of the Cys-loop receptor ligand-gated ion channel superfamily were recently identified. Previously, Cys-loop receptors were only known from multicellular organisms (metazoans). Contrary to the metazoan Cys-loop receptors, the prokaryotic ones consist of an extracellular (ECD) and a transmembrane domain (TMD), lacking the large intracellular domain (ICD) present in metazoa (between transmembrane segments M3 and M4). Using a chimera approach, we added the 115-amino acid ICD from mammalian serotonin type 3A receptors (5-HT(3A)) to the prokaryotic proton-activated Gloeobacter violaceus ligand-gated ion channel (GLIC). We created 12 GLIC-5-HT(3A)-ICD chimeras by replacing a variable number of amino acids in the short GLIC M3M4 linker with the entire 5-HT(3A)-ICD. Two-electrode voltage clamp recordings after expression in Xenopus laevis oocytes showed that only two chimeras were functional and produced currents upon acidification. The pH(50) was comparable with wild-type GLIC. 5-HT(3A) receptor expression can be inhibited by the chaperone protein RIC-3. We have shown previously that the 5-HT(3A)-ICD is required for the attenuation of 5-HT-induced currents when RIC-3 is co-expressed with 5-HT(3A) receptors in X. laevis oocytes. Expression of both functional 5-HT(3A) chimeras was inhibited by RIC-3 co-expression, indicating appropriate folding of the 5-HT(3A)-ICD in the chimeras. Our results indicate that the ICD can be considered a separate domain that can be removed from or added to the ECD and TMD while maintaining the overall structure and function of the ECD and TMD.
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Affiliation(s)
- Raman Goyal
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
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14
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Bader AN, Hoetzl S, Hofman EG, Voortman J, van Bergen en Henegouwen PMP, van Meer G, Gerritsen HC. Homo‐FRET Imaging as a Tool to Quantify Protein and Lipid Clustering. Chemphyschem 2010; 12:475-83. [DOI: 10.1002/cphc.201000801] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Indexed: 11/11/2022]
Affiliation(s)
- Arjen N. Bader
- Department of Molecular Biophysics, Universiteit Utrecht, Princetonplein 1, 3584 CC Utrecht (The Netherlands), Fax: (+31) 30 253 2706
| | - Sandra Hoetzl
- Department of Membrane Enzymology, Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht (The Netherlands)
| | - Erik G. Hofman
- Department of Cellular Dynamics, Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht (The Netherlands)
| | - Jarno Voortman
- Department of Cellular Dynamics, Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht (The Netherlands)
| | | | - Gerrit van Meer
- Department of Membrane Enzymology, Universiteit Utrecht, Padualaan 8, 3584 CH Utrecht (The Netherlands)
| | - Hans C. Gerritsen
- Department of Molecular Biophysics, Universiteit Utrecht, Princetonplein 1, 3584 CC Utrecht (The Netherlands), Fax: (+31) 30 253 2706
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15
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Guignet EG, Segura JM, Hovius R, Vogel H. Repetitive Reversible Labeling of Proteins at Polyhistidine Sequences for Single-Molecule Imaging in Live Cells. Chemphyschem 2007; 8:1221-7. [PMID: 17436349 DOI: 10.1002/cphc.200700065] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sensitive live-cell fluorescence microscopy and single-molecule imaging are severely limited by rapid photobleaching of fluorescent probes. Herein, we show how to circumvent this problem using a novel, generic labeling strategy. Small nickel-nitrilotriacetate fluorescent probes are reversibly bound to oligohistidine sequences of exposed proteins on cell surfaces, permitting selective observation of the proteins by fluorescence microscopy. Photobleached probes are removed by washing and replaced by new fluorophores, thus enabling repetitive acquisition of single-molecule trajectories on the same cell and allowing variation of experimental conditions between acquisitions. This method offers free choice of fluorophores while being minimally perturbing. The strength of the method is demonstrated by labeling engineered polyhistidine sequences of the serotonin-gated 5-HT(3) receptor on the surface of live mammalian cells. Single-molecule microscopy reveals pronounced heterogeneous mobility patterns of the 5-HT(3) receptor. After activating the receptor with serotonin, the number of immobile receptors increases substantially, which might be important for receptor regulation at synapses.
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Affiliation(s)
- Emmanuel G Guignet
- Laboratory of Physical Chemistry of Polymers and Membranes, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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16
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Grandl J, Sakr E, Kotzyba-Hibert F, Krieger F, Bertrand S, Bertrand D, Vogel H, Goeldner M, Hovius R. Fluorescent Epibatidine Agonists for Neuronal and Muscle-Type Nicotinic Acetylcholine Receptors. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604807] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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17
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Grandl J, Sakr E, Kotzyba-Hibert F, Krieger F, Bertrand S, Bertrand D, Vogel H, Goeldner M, Hovius R. Fluorescent Epibatidine Agonists for Neuronal and Muscle-Type Nicotinic Acetylcholine Receptors. Angew Chem Int Ed Engl 2007; 46:3505-8. [PMID: 17385777 DOI: 10.1002/anie.200604807] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Jörg Grandl
- Laboratoire de Chimie Physique des Polymères et Membranes, Ecole Polytechniques Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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18
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Peters JA, Carland JE, Cooper MA, Livesey MR, Deeb TZ, Hales TG, Lambert JJ. Novel structural determinants of single-channel conductance in nicotinic acetylcholine and 5-hydroxytryptamine type-3 receptors. Biochem Soc Trans 2007; 34:882-6. [PMID: 17052220 DOI: 10.1042/bst0340882] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Nicotinic ACh (acetylcholine) and 5-HT3 (5-hydroxytryptamine type-3) receptors are cation-selective ion channels of the Cys-loop transmitter-gated ion channel superfamily. Numerous lines of evidence indicate that the channel lining domain of such receptors is formed by the alpha-helical M2 domain (second transmembrane domain) contributed by each of five subunits present within the receptor complex. Specific amino acid residues within the M2 domain have accordingly been demonstrated to influence both single-channel conductance (gamma) and ion selectivity. However, it is now clear from work performed on the homomeric 5-HT3A receptor, heteromeric 5-HT3A/5-HT3B receptor and 5-HT3A/5-HT3B receptor subunit chimaeric constructs that an additional major determinant of gamma resides within a cytoplasmic domain of the receptor termed the MA-stretch (membrane-associated stretch). The MA-stretch, within the M3-M4 loop, is not traditionally thought to be implicated in ion permeation and selection. Here, we describe how such observations extend to a representative neuronal nicotinic ACh receptor composed of alpha4 and beta2 subunits and, by inference, probably other members of the Cys-loop family. In addition, we will attempt to interpret our results within the context of a recently developed atomic scale model of the nicotinic ACh receptor of Torpedo marmorata (marbled electric ray).
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Affiliation(s)
- J A Peters
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, The University of Dundee, Dundee DD1 9SY, UK.
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Hu XQ, Sun H, Peoples RW, Hong R, Zhang L. An interaction involving an arginine residue in the cytoplasmic domain of the 5-HT3A receptor contributes to receptor desensitization mechanism. J Biol Chem 2006; 281:21781-21788. [PMID: 16754678 DOI: 10.1074/jbc.m600676200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A large cytoplasmic domain accounts for approximately one-third of the entire protein of one superfamily of ligand-gated membrane ion channels, which includes nicotinic acetylcholine (nACh), gamma-aminobutyric acid type A (GABA(A)), serotonin type 3 (5-HT3), and glycine receptors. Desensitization is one functional feature shared by these receptors. Because most molecular studies of receptor desensitization have focused on the agonist binding and channel pore domains, relatively little is known about the role of the large cytoplasmic domain (LCD) in this process. To address this issue, we sequentially deleted segments of the LCD of the 5-HT3A receptor and examined the function of the mutant receptors. Deletion of a small segment that contains three amino acid residues (425-427) significantly slowed the desensitization kinetics of the 5-HT3A receptor. Both deletion and point mutation of arginine 427 altered desensitization kinetics in a manner similar to that of the (425-427) deletion without significantly changing the apparent agonist affinity. The extent of receptor desensitization was positively correlated with the polarity of the amino acid residue at 427: the desensitization accelerates with increasing polarity. Whereas the R427L mutation produced the slowest desensitization, it did not significantly alter single channel conductance of 5-HT3A receptor. Thus, the arginine 427 residue in the LCD contributes to 5-HT3A receptor desensitization, possibly through forming an electrostatic interaction with its neighboring residues. Because the polarity of the amino acid residue at 427 is highly conserved, such a desensitization mechanism may occur in other members of the Cys-loop family of ligand-gated ion channels.
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Affiliation(s)
- Xiang-Qun Hu
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-8115
| | - Hui Sun
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-8115
| | - Robert W Peoples
- Department of Biomedical Sciences, College of Health Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881
| | - Ren Hong
- Department of Biomedical Sciences, College of Health Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881
| | - Li Zhang
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-8115.
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Meyer BH, Martinez KL, Segura JM, Pascoal P, Hovius R, George N, Johnsson K, Vogel H. Covalent labeling of cell-surface proteins for in-vivo FRET studies. FEBS Lett 2006; 580:1654-8. [PMID: 16497304 DOI: 10.1016/j.febslet.2006.02.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 01/11/2006] [Accepted: 02/06/2006] [Indexed: 10/25/2022]
Abstract
Fluorescence resonance energy transfer (FRET) is a powerful technique to reveal interactions between membrane proteins in live cells. Fluorescence labeling for FRET is typically performed by fusion with fluorescent proteins (FP) with the drawbacks of a limited choice of fluorophores, an arduous control of donor-acceptor ratio and high background fluorescence arising from intracellular FPs. Here we show that these shortcomings can be overcome by using the acyl carrier protein labeling technique. FRET revealed interactions between cell-surface neurokinin-1 receptors simultaneously labeled with a controlled ratio of donors and acceptors. Moreover, using FRET the specific binding of fluorescent agonists could be monitored.
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Affiliation(s)
- Bruno H Meyer
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Science et Ingénierie Chimiques, CH-1015 Lausanne, Switzerland
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