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O'Connor EC, Kambara K, Bertrand D. Advancements in the use of xenopus oocytes for modelling neurological disease for novel drug discovery. Expert Opin Drug Discov 2024; 19:173-187. [PMID: 37850233 DOI: 10.1080/17460441.2023.2270902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 10/11/2023] [Indexed: 10/19/2023]
Abstract
INTRODUCTION Introduced about 50 years ago, the model of Xenopus oocytes for the expression of recombinant proteins has gained a broad spectrum of applications. The authors herein review the benefits brought from using this model system, with a focus on modeling neurological disease mechanisms and application to drug discovery. AREAS COVERED Using multiple examples spanning from ligand gated ion channels to transporters, this review presents, in the light of the latest publications, the benefits offered from using Xenopus oocytes. Studies range from the characterization of gene mutations to the discovery of novel treatments for disorders of the central nervous system (CNS). EXPERT OPINION Development of new drugs targeting CNS disorders has been marked by failures in the translation from preclinical to clinical studies. As progress in genetics and molecular biology highlights large functional differences arising from a single to a few amino acid exchanges, the need for drug screening and functional testing against human proteins is increasing. The use of Xenopus oocytes to enable precise modeling and characterization of clinically relevant genetic variants constitutes a powerful model system that can be used to inform various aspects of CNS drug discovery and development.
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Affiliation(s)
- Eoin C O'Connor
- Roche Pharma Research and Early Development, Neuroscience & Rare Diseases, Roche Innovation Center Basel, Basel, Switzerland
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Sastre D, Fedida D. Voltage Clamp Fluorometry: Illuminating the Dynamics of Ion Channels. Methods Mol Biol 2024; 2796:119-138. [PMID: 38856899 DOI: 10.1007/978-1-0716-3818-7_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Ion channels comprise one of the largest targets for drug development and treatment and have been a subject of enduring fascination since first discovered in the 1950s. Over the past decades, thousands of publications have explored the cellular biology and molecular physiology of these proteins, and many channel structures have been determined since the late 1990s. Trying to connect the dots between ion channel function and structure, voltage clamp fluorometry (VCF) emerges as a powerful tool because it allows monitoring of the conformational rearrangements underlying the different functional states of the channel. This technique represents an elegant harmonization of molecular biology, electrophysiology, and fluorescence. In the following chapter, we will provide a concise guide to performing VCF on Xenopus laevis oocytes using the two-electrode voltage clamp (TEVC) modality. This is the most widely used configuration on Xenopus oocytes for its relative simplicity and demonstrated success in a number of different ion channels utilizing a variety of attached labels.
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Affiliation(s)
- Daniel Sastre
- Faculty of Medicine, Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
| | - David Fedida
- Faculty of Medicine, Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada.
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Bhatt M, Di Iacovo A, Romanazzi T, Roseti C, Cinquetti R, Bossi E. The "www" of Xenopus laevis Oocytes: The Why, When, What of Xenopus laevis Oocytes in Membrane Transporters Research. MEMBRANES 2022; 12:membranes12100927. [PMID: 36295686 PMCID: PMC9610376 DOI: 10.3390/membranes12100927] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 05/16/2023]
Abstract
After 50 years, the heterologous expression of proteins in Xenopus laevis oocytes is still essential in many research fields. New approaches and revised protocols, but also classical methods, such as the two-electrode voltage clamp, are applied in studying membrane transporters. New and old methods for investigating the activity and the expression of Solute Carriers (SLC) are reviewed, and the kinds of experiment that are still useful to perform with this kind of cell are reported. Xenopus laevis oocytes at the full-grown stage have a highly efficient biosynthetic apparatus that correctly targets functional proteins at the defined compartment. This small protein factory can produce, fold, and localize almost any kind of wild-type or recombinant protein; some tricks are required to obtain high expression and to verify the functionality. The methodologies examined here are mainly related to research in the field of membrane transporters. This work is certainly not exhaustive; it has been carried out to be helpful to researchers who want to quickly find suggestions and detailed indications when investigating the functionality and expression of the different members of the solute carrier families.
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Affiliation(s)
- Manan Bhatt
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Angela Di Iacovo
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Tiziana Romanazzi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Cristina Roseti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
| | - Raffaella Cinquetti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
| | - Elena Bossi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
- Correspondence:
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Schmalzing G, Markwardt F. Established Protocols for cRNA Expression and Voltage-Clamp Characterization of the P2X7 Receptor in Xenopus laevis Oocytes. Methods Mol Biol 2022; 2510:157-192. [PMID: 35776325 DOI: 10.1007/978-1-0716-2384-8_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
P2X7 receptors (P2X7Rs) are fast ATP4--gated ion channels that, like other members of the P2X receptor family, function as homotrimers. A high-resolution cryo-EM structure of the full-length rat P2X7R is available. Using voltage-clamp experiments in Xenopus laevis oocytes, even the earliest steps of P2X7R activation can be quantitatively recorded in the millisecond range. Site-directed mutagenesis combined with voltage-clamp recordings can reveal residues and domains of the P2X7R involved in ATP4- binding, gating (i.e., opening and closing of the channel pore) and ion selectivity. We present here proven voltage-clamp protocols that take into account requirements that are important at the levels of cDNA and vector sequences, cRNA synthesis, and Xenopus laevis oocyte isolation for reliable results.
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Affiliation(s)
- Günther Schmalzing
- Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany
| | - Fritz Markwardt
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany.
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Oliver Dolly J, Henley JM, Stephenson FA. Eric A. Barnard FRS (1927-2018). J Neurochem 2018. [DOI: 10.1111/jnc.14584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- J. Oliver Dolly
- International Centre for Neurotherapeutics; Dublin City University; Dublin Ireland
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Abdelmassih SA, Cochrane E, Forrester SG. Evaluating the longevity of surgically extracted Xenopus laevis oocytes for the study of nematode ligand-gated ion channels. INVERTEBRATE NEUROSCIENCE 2017; 18:1. [PMID: 29185074 DOI: 10.1007/s10158-017-0205-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 11/18/2017] [Indexed: 11/26/2022]
Abstract
Xenopus laevis oocytes have been extensively used as a heterologous expression system for the study of ion channels. While used successfully worldwide as tool for expressing and characterizing ion channels from a wide range of species, the limited longevity of oocytes once removed from the animal can pose significant challenges. In this study, we evaluate a simple and useful method that extends the longevity of Xenopus oocytes after removal from the animal and quantitatively assessed the reliability of the electrophysiological date obtained. The receptor used for this study was the UNC-49 receptor originally isolated from the sheep parasite, Haemonchus contortus. Overall, we found that immediate storage of the ovary in supplemented ND96 storage buffer at 4 °C could extend their use for up to 17 days with almost 80% providing reliable electrophysiological data. This means that a single extraction can provide at least 3 weeks of experiments. In addition, we examined 24-day-old oocytes (week 4) extracted from a single frog and also obtained reliable data using the same approach. However, 50% of these oocytes were usable for full dose-response experiments. Overall, we did find that this method has the potential to significantly extend the use of single oocyte extractions for two-electrode voltage clamp electrophysiology.
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Affiliation(s)
- Sarah A Abdelmassih
- Applied Bioscience Graduate Program, Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Everett Cochrane
- Applied Bioscience Graduate Program, Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada
| | - Sean G Forrester
- Applied Bioscience Graduate Program, Faculty of Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, ON, L1H 7K4, Canada.
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Jørgensen ME, Crocoll C, Halkier BA, Nour-Eldin HH. Uptake Assays in Xenopus laevis Oocytes Using Liquid Chromatography-mass Spectrometry to Detect Transport Activity. Bio Protoc 2017; 7:e2581. [PMID: 34595263 DOI: 10.21769/bioprotoc.2581] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/10/2017] [Accepted: 09/25/2017] [Indexed: 11/02/2022] Open
Abstract
Xenopus laevis oocytes are a widely used model system for characterization of heterologously expressed secondary active transporters. Historically, researchers have relied on detecting transport activity by measuring accumulation of radiolabeled substrates by scintillation counting or of fluorescently labelled substrates by spectrofluorometric quantification. These techniques are, however, limited to substrates that are available as radiolabeled isotopes or to when the substrate is fluorescent. This prompted us to develop a transport assay where we could in principle detect transport activity for any organic metabolite regardless of its availability as radiolabeled isotope or fluorescence properties. In this protocol we describe the use of X. laevis oocytes as a heterologous host for expression of secondary active transporters and how to perform uptake assays followed by detection and quantification of transported metabolites by liquid chromatography-mass spectrometry (LC-MS). We have successfully used this method for identification and characterization of transporters of the plant defense metabolites called glucosinolates and cyanogenic glucosides ( Jørgensen et al., 2017 ), however the method is usable for the characterization of any transporter whose substrate can be detected by LC-MS.
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Affiliation(s)
- Morten Egevang Jørgensen
- University of Würzburg, Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs Platz 2, Würzburg, Germany
| | - Christoph Crocoll
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.,Copenhagen Plant Science Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark
| | - Barbara Ann Halkier
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.,Copenhagen Plant Science Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark
| | - Hussam Hassan Nour-Eldin
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark.,Copenhagen Plant Science Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, Denmark
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Wisden W. A Tribute to Peter H Seeburg (1944-2016): A Founding Father of Molecular Neurobiology. Front Mol Neurosci 2016; 9:133. [PMID: 27965536 PMCID: PMC5126100 DOI: 10.3389/fnmol.2016.00133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 11/15/2016] [Indexed: 11/25/2022] Open
Affiliation(s)
- William Wisden
- Department of Life Sciences and Centre for Neurotechnology, Imperial College London London, UK
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Heterogeneous Inhibition in Macroscopic Current Responses of Four Nicotinic Acetylcholine Receptor Subtypes by Cholesterol Enrichment. J Membr Biol 2016; 249:539-49. [PMID: 27116687 DOI: 10.1007/s00232-016-9896-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 04/02/2016] [Indexed: 10/21/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR), located in the cell membranes of neurons and muscle cells, mediates the transmission of nerve impulses across cholinergic synapses. In addition, the nAChR is also found in the electric organs of electric rays (e.g., the genus Torpedo). Cholesterol, which is a key lipid for maintaining the correct functionality of membrane proteins, has been found to alter the nAChR function. We were thus interested to probe the changes in the functionality of different nAChRs expressed in a model membrane with modified cholesterol to phospholipid ratios (C/P). In this study, we examined the effect of increasing the C/P ratio in Xenopus laevis oocytes expressing the neuronal α7, α4β2, muscle-type, and Torpedo californica nAChRs in their macroscopic current responses. Using the two-electrode voltage clamp technique, it was found that the neuronal α7 and Torpedo nAChRs are significantly more sensitive to small increases in C/P than the muscle-type nAChR. The peak current versus C/P profiles during enrichment display different behaviors; α7 and Torpedo nAChRs display a hyperbolic decay with two clear components, whereas muscle-type and α4β2 nAChRs display simple monophasic decays with different slopes. This study clearly illustrates that a physiologically relevant increase in membrane cholesterol concentration produces a remarkable reduction in the macroscopic current responses of the neuronal α7 and Torpedo nAChRs functionality, whereas the muscle nAChR appears to be the most resistant to cholesterol inhibition among all four nAChR subtypes. Overall, the present study demonstrates differential profiles for cholesterol inhibition among the different types of nAChR to physiological cholesterol increments in the plasmatic membrane. This is the first study to report a cross-correlation analysis of cholesterol sensitivity among different nAChR subtypes in a model membrane.
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Jørgensen ME, Nour-Eldin HH, Halkier BA. A Western Blot Protocol for Detection of Proteins Heterologously Expressed in Xenopus laevis Oocytes. Methods Mol Biol 2016; 1405:99-107. [PMID: 26843169 DOI: 10.1007/978-1-4939-3393-8_10] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Oocytes of the African clawed frog, Xenopus laevis, are often used for expression and biochemical characterization of transporter proteins as the oocytes are particularly suitable for uptake assays and electrophysiological recordings. Assessment of the expression level of expressed transporters at the individual oocyte level is often desirable when comparing properties of wild type and mutant transporters. However, a large content of yolk platelets in the oocyte cytoplasm makes this a challenging task. Here we report a method for fast and easy, semiquantitative Western blot analysis of proteins heterologously expressed in Xenopus oocytes.
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Affiliation(s)
- Morten Egevang Jørgensen
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Hussam Hassan Nour-Eldin
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Barbara Ann Halkier
- DynaMo Center, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, 1871, Frederiksberg C, Denmark.
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11
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Filchakova O, McIntosh JM. Functional expression of human α9* nicotinic acetylcholine receptors in X. laevis oocytes is dependent on the α9 subunit 5' UTR. PLoS One 2013; 8:e64655. [PMID: 23717646 PMCID: PMC3661583 DOI: 10.1371/journal.pone.0064655] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/18/2013] [Indexed: 11/19/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing the α9 subunit are expressed in a wide variety of non-neuronal tissues ranging from immune cells to breast carcinomas. The α9 subunit is able to assemble into a functional homomeric nAChR and also co-assemble with the α10 subunit into functional heteromeric nAChRs. Despite the increasing awareness of the important roles of this subunit in vertebrates, the study of human α9-containing nAChRs has been severely limited by difficulties in its expression in heterologous systems. In Xenopus laevis oocytes, functional expression of human α9α10 nAChRs is very low compared to that of rat α9α10 nAChRs. When oocytes were co-injected with cRNA of α9 and α10 subunits of human versus those of rat, oocytes with the rat α9 human α10 combination had an ∼-fold higher level of acetylcholine-gated currents (IACh) than those with the human α9 rat α10 combination, suggesting difficulties with human α9 expression. When the ratio of injected human α9 cRNA to human α10 cRNA was increased from 1∶1 to 5∶1, IACh increased 36-fold (from 142±23 nA to 5171±748 nA). Functional expression of human α9-containing receptors in oocytes was markedly improved by appending the 5′-untranslated region of alfalfa mosaic virus RNA4 to the 5′-leader sequence of the α9 subunit cRNA. This increased the functional expression of homomeric human α9 receptors by 70-fold (from 7±1 nA to 475±158 nA) and of human α9α10 heteromeric receptors by 80-fold (from 113±62 nA to 9192±1137 nA). These findings indicate the importance of the composition of the 5′ untranslated leader sequence for expression of α9-containing nAChRs.
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Affiliation(s)
- Olena Filchakova
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, Utah, United States of America.
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12
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Odorant receptor modulation: Ternary paradigm for mode of action of insect repellents. Neuropharmacology 2012; 62:2086-95. [DOI: 10.1016/j.neuropharm.2012.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 12/12/2011] [Accepted: 01/09/2012] [Indexed: 11/18/2022]
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Bohbot JD, Fu L, LE TC, Chauhan KR, Cantrell CL, Dickens JC. Multiple activities of insect repellents on odorant receptors in mosquitoes. MEDICAL AND VETERINARY ENTOMOLOGY 2011; 25:436-444. [PMID: 21395633 DOI: 10.1111/j.1365-2915.2011.00949.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Several lines of evidence suggest that insect repellent molecules reduce mosquito-host contacts by interacting with odorants and odorant receptors (ORs), thereby ultimately affecting olfactory-driven behaviours. We describe the molecular effects of 10 insect repellents and a pyrethroid insecticide with known repellent activity on two highly specific Aedes aegypti (Diptera: Culicidae) ORs, AaOR2 + AaOR7 and AaOR8 + AaOR7, exquisitely sensitive to key mosquito attractants indole and (R)-(-)-1-octen-3-ol, expressed in oocytes of Xenopus (Anura: Pipidae). Our study demonstrates that insect repellents can both inhibit odorant-evoked currents mediated by ORs and independently elicit currents in the absence of odorants. All of the repellents had effects on one or both ORs; most of these compounds were selective inhibitors and showed a high degree of specificity in their capacity to activate the two ORs. These results show that a range of insect repellents belonging to structurally diverse chemical classes modulate the function of mosquito ORs through multiple molecular mechanisms.
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Affiliation(s)
- J D Bohbot
- Invasive Insect Biocontrol and Behavior Laboratory, Plant Sciences Institute, U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), Henry A. Wallace Beltsville Agricultural Research Center, Beltsville, MD, U.S.A.
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Bohbot JD, Dickens JC. Insect repellents: modulators of mosquito odorant receptor activity. PLoS One 2010; 5:e12138. [PMID: 20725637 PMCID: PMC2920324 DOI: 10.1371/journal.pone.0012138] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 07/21/2010] [Indexed: 11/18/2022] Open
Abstract
Background DEET, 2-undecanone (2-U), IR3535 and Picaridin are widely used as insect repellents to prevent interactions between humans and many arthropods including mosquitoes. Their molecular action has only recently been studied, yielding seemingly contradictory theories including odorant-dependent inhibitory and odorant-independent excitatory activities on insect olfactory sensory neurons (OSNs) and odorant receptor proteins (ORs). Methodology/Principal Findings Here we characterize the action of these repellents on two Aedes aegypti ORs, AaOR2 and AaOR8, individually co-expressed with the common co-receptor AaOR7 in Xenopus oocytes; these ORs are respectively activated by the odors indole (AaOR2) and (R)-(−)-1-octen3-ol (AaOR8), odorants used to locate oviposition sites and host animals. In the absence of odorants, DEET activates AaOR2 but not AaOR8, while 2-U activates AaOR8 but not AaOR2; IR3535 and Picaridin do not activate these ORs. In the presence of odors, DEET strongly inhibits AaOR8 but not AaOR2, while 2-U strongly inhibits AaOR2 but not AaOR8; IR3535 and Picaridin strongly inhibit both ORs. Conclusions/Significance These data demonstrate that repellents can act as olfactory agonists or antagonists, thus modulating OR activity, bringing concordance to conflicting models.
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Affiliation(s)
- Jonathan D. Bohbot
- Invasive Insect Biocontrol and Behavior Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Plant Sciences Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland, United States of America
| | - Joseph C. Dickens
- Invasive Insect Biocontrol and Behavior Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Plant Sciences Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland, United States of America
- * E-mail:
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Musa-Aziz R, Boron WF, Parker MD. Using fluorometry and ion-sensitive microelectrodes to study the functional expression of heterologously-expressed ion channels and transporters in Xenopus oocytes. Methods 2010; 51:134-45. [PMID: 20051266 PMCID: PMC2905798 DOI: 10.1016/j.ymeth.2009.12.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 12/23/2009] [Accepted: 12/29/2009] [Indexed: 12/17/2022] Open
Abstract
The Xenopus laevis oocyte is a model system for the electrophysiological study of exogenous ion transporters. Three main reasons make the oocyte suitable for this purpose: (a) it has a large cell size (approximately 1mm diameter), (b) it has an established capacity to produce-from microinjected mRNAs or cRNAs-exogenous ion transporters with close-to-physiological post-translational modifications and actions, and (c) its membranes contain endogenous ion-transport activities which are usually smaller in magnitude than the activities of exogenously-expressed ion transporters. The expression of ion transporters as green fluorescent protein fusions allows the fluorometric assay of transporter yield in living oocytes. Monitoring of transporter-mediated movement of ions such as Cl(-), H(+) (and hence base equivalents like OH(-) and HCO(3)(-)), K(+), and Na(+) is achieved by positioning the tips of ion-sensitive microelectrodes inside the oocyte and/or at the surface of the oocyte plasma membrane. The use of ion-sensitive electrodes is critical for studying net ion-movements mediated by electroneutral transporters. The combined use of fluorometry and electrophysiology expedites transporter study by allowing measurement of transporter yield prior to electrophysiological study and correlation of relative transporter yield with transport rates.
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Affiliation(s)
- Raif Musa-Aziz
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Characterization of an enantioselective odorant receptor in the yellow fever mosquito Aedes aegypti. PLoS One 2009; 4:e7032. [PMID: 19753115 PMCID: PMC2737144 DOI: 10.1371/journal.pone.0007032] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 08/17/2009] [Indexed: 11/19/2022] Open
Abstract
Enantiomers differ only in the left or right handedness (chirality) of their orientations and exhibit identical chemical and physical properties. In chemical communication systems, enantiomers can be differentially active at the physiological and behavioral levels. Only recently were enantioselective odorant receptors demonstrated in mammals while their existence in insects has remained hypothetical. Using the two-microelectrode voltage clamp of Xenopus oocytes, we show that the yellow fever mosquito, Aedes aegypti, odorant receptor 8 (AaOR8) acts as a chiral selective receptor for the (R)-(-)-enantiomer of 1-octen-3-ol, which in the presence of other kairomones is an attractant used by blood-sucking insects to locate their hosts. In addition to steric constraints, chain length and degree of unsaturation play important roles in this recognition process. This is the first characterization of an enantioselective odorant receptor in insects and the results demonstrate that an OR alone, without helper proteins, can account for chiral specificity exhibited by olfactory sensory neurons (OSNs).
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Schmidt C, Klein C, Hollmann M. Xenopus laevis Oocytes Endogenously Express All Subunits of the Ionotropic Glutamate Receptor Family. J Mol Biol 2009; 390:182-95. [DOI: 10.1016/j.jmb.2009.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 05/07/2009] [Accepted: 05/07/2009] [Indexed: 01/27/2023]
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Millar NS. A review of experimental techniques used for the heterologous expression of nicotinic acetylcholine receptors. Biochem Pharmacol 2009; 78:766-76. [PMID: 19540210 DOI: 10.1016/j.bcp.2009.06.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 06/08/2009] [Accepted: 06/10/2009] [Indexed: 11/18/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are members of the Cys-loop family of neurotransmitter-gated ion channels, a family that also includes receptors for gamma-aminobutyric acid, glycine and 5-hydroxytryptamine. In humans, nAChRs have been implicated in several neurological and psychiatric disorders and are major targets for pharmaceutical drug discovery. In addition, nAChRs are important targets for neuroactive pesticides in insects and in other invertebrates. Historically, nAChRs have been one of the most intensively studied families of neurotransmitter receptors. They were the first neurotransmitter receptors to be biochemically purified and the first to be characterized by molecular cloning and heterologous expression. Although much has been learnt from studies of native nAChRs, the expression of recombinant nAChRs has provided dramatic advances in the characterization of these important receptors. This review will provide a brief history of the characterization of nAChRs by heterologous expression. It will focus, in particular, upon studies of recombinant nAChRs, work that has been conducted by many hundreds of scientists during a period of almost 30 years since the molecular cloning of nAChR subunits in the early 1980s.
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Affiliation(s)
- Neil S Millar
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
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Abstract
In this perspective I tell the story (albeit a clearly abridged version) of how our knowledge of ion conduction through ion channels has evolved from a purely electrical concept to a structural dynamics view of ions interacting with a membrane protein. Our progress in this field has shown steady growth over the years but has also been interspersed with sudden jumps of discovery. These leaps have normally been associated with the introduction of a new technical advance or the development of a new biological preparation; therefore, it is quite certain that we have not seen them all.
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Affiliation(s)
- Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
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Tammaro P, Shimomura K, Proks P. Xenopus oocytes as a heterologous expression system for studying ion channels with the patch-clamp technique. Methods Mol Biol 2008; 491:127-39. [PMID: 18998089 DOI: 10.1007/978-1-59745-526-8_10] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Oocytes from the Xenopus laevis represent one of the most widely used expression systems for functional characterization of ion channels. Their large size facilitates both injection of heterologous cRNA and subsequent electrophysiological recordings of ion channel currents. Furthermore, Xenopus oocytes translate cRNA very efficiently, resulting in the generation of a large number of ion channels in the plasma membrane. In this chapter, we outline methods for oocyte preparation and maintenance and describe procedures for patch-clamping of oocytes, with a special focus on the macropatch technique. We discuss some common problems associated with patch-clamping of oocytes and their use as an expression system for ion channels.
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Affiliation(s)
- Paolo Tammaro
- Department of Physiology, Anatomy and Genetics, University of Oxford, UK
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Gerber S, Krasky A, Rohwer A, Lindauer S, Closs E, Rognan D, Gunkel N, Selzer PM, Wolf C. Identification and characterisation of the dopamine receptor II from the cat flea Ctenocephalides felis (CfDopRII). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2006; 36:749-58. [PMID: 17027841 DOI: 10.1016/j.ibmb.2006.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 07/12/2006] [Accepted: 07/13/2006] [Indexed: 05/12/2023]
Abstract
G protein-coupled receptors (GPCRs) represent a protein family with a wide range of functions. Approximately 30% of human drug targets are GPCRs, illustrating their pharmaceutical relevance. In contrast, the knowledge about invertebrate GPCRs is limited and is mainly restricted to model organisms like Drosophila melanogaster and Caenorhabditis elegans. Especially in ectoparasites like ticks and fleas, only few GPCRs are characterised. From the cat flea Ctenocephalides felis, a relevant parasite of cats and dogs, no GPCRs are known so far. Thus, we performed a bioinformatic analysis of available insect GPCR sequences from the honeybee Apis mellifera, the mosquito Anopheles gambiae, the fruit fly Drosophila melanogaster and genomic sequences from insect species. Aim of this analysis was the identification of highly conserved GPCRs in order to clone orthologs of these candidates from Ctenocephalides felis. It was found that the dopamine receptor family revealed highest conservation levels and thus was chosen for further characterisation. In this work, the identification, full-length cloning and functional expression of the first GPCR from Ctenocephalides felis, the dopamine receptor II (CfDopRII), are described.
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Affiliation(s)
- Sonja Gerber
- Intervet Innovation GmbH, Zur Propstei, 55270 Schwabenheim, Germany
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22
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Hosy E, Duby G, Véry AA, Costa A, Sentenac H, Thibaud JB. A procedure for localisation and electrophysiological characterisation of ion channels heterologously expressed in a plant context. PLANT METHODS 2005; 1:14. [PMID: 16359560 PMCID: PMC1352354 DOI: 10.1186/1746-4811-1-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Accepted: 12/19/2005] [Indexed: 05/05/2023]
Abstract
BACKGROUND In silico analyses based on sequence similarities with animal channels have identified a large number of plant genes likely to encode ion channels. The attempts made to characterise such putative plant channels at the functional level have most often relied on electrophysiological analyses in classical expression systems, such as Xenopus oocytes or mammalian cells. In a number of cases, these expression systems have failed so far to provide functional data and one can speculate that using a plant expression system instead of an animal one might provide a more efficient way towards functional characterisation of plant channels, and a more realistic context to investigate regulation of plant channels. RESULTS With the aim of developing a plant expression system readily amenable to electrophysiological analyses, we optimised experimental conditions for preparation and transformation of tobacco mesophyll protoplasts and engineered expression plasmids, that were designed to allow subcellular localisation and functional characterisation of ion channels eventually in presence of their putative (possibly over-expressed) regulatory partners. Two inward K+ channels from the Shaker family were functionally expressed in this system: not only the compliant KAT1 but also the recalcitrant AKT1 channel, which remains electrically silent when expressed in Xenopus oocytes or in mammalian cells. CONCLUSION The level of endogenous currents in control protoplasts seems compatible with the use of the described experimental procedures for the characterisation of plant ion channels, by studying for instance their subcellular localisation, functional properties, structure-function relationships, interacting partners and regulation, very likely in a more realistic context than the classically used animal systems.
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Affiliation(s)
- E Hosy
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
- Present address: Laboratoire de Biophysique Moléculaire et Cellulaire, UMR 5090, CEA-DRDC-BMC, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France
| | - G Duby
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
- Present address: Unité de Biochimie Physiologique, Institut des Sciences de la Vie, Université Catholique Louvain, Place Croix du Sud, 5-15, 1348 Louvain-la-Neuve, Belgium
| | - A-A Véry
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
| | - A Costa
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
- Present address: Division of Biology, Cell and Developmental Biology Section, and Center for Molecular Genetics, University of California San Diego, CA 92093-0116 La Jolla, USA
| | - H Sentenac
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
| | - J-B Thibaud
- Biochimie et Physiologie Moléculaires des Plantes, UMR 5004, Agro-M/CNRS/INRA/UM2, F-34060 Montpellier Cedex 1, France
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Sigel E, Minier F. TheXenopus oocyte: System for the study of functional expression and modulation of proteins. Mol Nutr Food Res 2005; 49:228-34. [PMID: 15704243 DOI: 10.1002/mnfr.200400104] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Erwin Sigel
- Department of Pharmacology, University of Bern, Bern, Switzerland.
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24
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Affiliation(s)
- Donald D Brown
- Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland 21210, USA.
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25
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Barnard EA. Imagination and reality in the search for the P2Y receptors. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 81:10-5. [PMID: 10869694 DOI: 10.1016/s0165-1838(00)00147-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A great body of evidence based on tissue and organ physiology and pharmacology led to the recognition, widespread by about 1990, that there must be cell membrane receptors for extracellular nucleotides to transduce their effects. This evidence was provided by the pioneering work of Geoffrey Burnstock and those who worked with him, or was developed by others starting from that information. This article will review how we could start from that foundation to clone the first known gene for such a receptor, P2Y(1). Some unusual properties of that receptor were revealed. I will consider further the P2Y receptors as a class - its definition, now that many such genes have become known. Imagination and reality have been intertwined in this saga.
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Affiliation(s)
- E A Barnard
- Department of Pharmacology, University of Cambridge, Tennis Court Road, CB2 1QJ, Cambridge, UK.
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26
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Nicke A, Rettinger J, Büttner C, Eichele A, Lambrecht G, Schmalzing G. Evolving view of quaternary structures of ligand-gated ion channels. PROGRESS IN BRAIN RESEARCH 1999; 120:61-80. [PMID: 10550988 DOI: 10.1016/s0079-6123(08)63546-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Affiliation(s)
- A Nicke
- Pharmakologisches Institut für Naturwissenschaftler, Johann Wolfgang Goethe-Universität, Frankfurt/Main, Germany
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27
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Affiliation(s)
- W Stühmer
- Max-Planck-Institut für Experimentelle Medizin, Göttingen, Germany
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28
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Leite MF, Moyer MS, Andrews NW. Expression of the mammalian calcium signaling response to Trypanosoma cruzi in Xenopus laevis oocytes. Mol Biochem Parasitol 1998; 92:1-13. [PMID: 9574905 DOI: 10.1016/s0166-6851(97)00211-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Infective stages of the protozoan parasite Trypanosoma cruzi contain a soluble factor that induces elevation in the intracellular free Ca2+ concentration ([Ca2+]i) of mammalian cells. The process is pertussis toxin (PTx)-sensitive, and involves phospholipase C (PLC) activation, inositol 1,4,5-trisphosphate (IP3) formation and Ca2+ release from intracellular stores (Tardieux I, et al. J Exp Med 1994;179:1017-1022; Rodriguez A, et al. J Cell Biol 1995;129:1263-1273). We now report that a molecule exposed on the surface of the target cells is required to trigger the signaling cascade, and that a response with identical characteristics can be induced in Xenopus laevis oocytes injected with mRNA from normal rat kidney (NRK) fibroblasts. Xenopus oocytes do not show an endogenous response to the trypomastigote Ca2+ signaling factor, but a vigorous response in the form of a propagating Ca2+ wave is expressed after injection of NRK cell mRNA. As previously demonstrated for mammalian cells, the response is inhibited when injected oocytes are pretreated with PTx, implicating Galphai or Galphao trimeric G-proteins, and with thapsigargin, which depletes intracellular Ca2+ stores. Moreover, the [Ca2+]i transients triggered by the T. cruzi soluble factor in mRNA-injected oocytes are blocked by the same inhibitors of the parasite oligopeptidase B that abolish the [Ca2+]i response in NRK cells (Burleigh B, Andrews NW. J Biol Chem 1995;270:5172-5180; Burleigh BA et al. J Cell Biol 1997;136:609-620). The NRK mRNA fraction that induces expression of the [Ca2+]i response to the T. cruzi signaling factor contains messages from 1.5 to 2.0 kb, a size range consistent with the family of seven-transmembrane G-protein-coupled receptors.
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Affiliation(s)
- M F Leite
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
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29
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Reale V, Hannan F, Midgley JM, Evans PD. The expression of a cloned Drosophila octopamine/tyramine receptor in Xenopus oocytes. Brain Res 1997; 769:309-20. [PMID: 9374200 DOI: 10.1016/s0006-8993(97)00723-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The expression of a cloned Drosophila octopamine/tyramine receptor (OctyR99AB) is described in Xenopus oocytes. Agonist stimulation of OctyR99AB receptors increased intracellular Ca2+ levels monitored as changes in the endogenous inward Ca2+-dependent chloride current. The receptor is preferentially sensitive to biogenic amines with a single hydroxyl on the aromatic ring. The G-protein, Galphai, appears to be involved in the coupling of the receptor to the production of intracellular calcium signals, since the effect is pertussis-toxin sensitive and is blocked or substantially reduced in antisense knockout experiments using oligonucleotides directed against Galphai but not by those directed against Galphao, Galphaq and Galpha11. The increase in intracellular calcium levels induced by activation of the OctyR99AB receptor can potentiate the ability of activation of a co-expressed beta2-adrenergic receptor to increase oocyte cyclic AMP levels. A comparison of the pharmacological coupling of OctyR99AB to different second messenger systems when expressed in Xenopus oocytes with previous studies on the expression of the receptor in a Chinese hamster ovary cell line suggests that the property of agonist-specific coupling of the receptor to different second messenger systems may be cell-specific, depending upon the G-protein environment of any particular cell type.
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Affiliation(s)
- V Reale
- The Babraham Institute Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, UK
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30
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Abstract
A cDNA clone is described that encodes a novel G-protein-coupled dopamine receptor (DopR99B) expressed in Drosophila heads. The DopR99B receptor maps to 99B3-5, close to the position of the octopamine/tyramine receptor gene at 99A10-B1, suggesting that the two may be related through a gene duplication. Agonist stimulation of DopR99B receptors expressed in Xenopus oocytes increased intracellular Ca2+ levels monitored as changes in an endogenous inward Ca2+-dependent chloride current. In addition to initiating this intracellular Ca2+ signal, stimulation of DopR99B increased cAMP levels. The rank order of potency of agonists in stimulating the chloride current is: dopamine > norepinephrine > epinephrine > tyramine. Octopamine and 5-hydroxytryptamine are not active (< 100 microM). This pharmacological profile plus the second-messenger coupling pattern suggest that the DopR99B receptor is a D1-like dopamine receptor. However, the hydrophobic core region of the DopR99B receptor shows almost equal amino acid sequence identity (40-48%) with vertebrate serotonergic, alpha 1- and beta-adrenergic, and D1-like and D2-like dopaminergic receptors. Thus, this Drosophila receptor defines a novel structural class of dopamine receptors. Because DopR99B is the second dopamine receptor cloned from Drosophila, this work establishes dopamine receptor diversity in a system amenable to genetic dissection.
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Narahashi T, Ma JY, Arakawa O, Reuveny E, Nakahiro M. GABA receptor-channel complex as a target site of mercury, copper, zinc, and lanthanides. Cell Mol Neurobiol 1994; 14:599-621. [PMID: 7641224 DOI: 10.1007/bf02088671] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. The GABAA receptor-chloride channel complex has been shown to be modulated by a variety of chemicals. Scores of chemicals with diverse and unrelated structures augment the GABA-induced chloride current, while some other chemicals suppress the current. Certain heavy metals and a variety of polyvalent cations increase or decrease the current in a potent and efficacious manner. 2. We have studied the mechanisms whereby mercury, copper, zinc, and lanthanides modulated the GABA system by whole-cell and single-channel patch clamp techniques as applied to the rat dorsal root ganglion neurons in primary culture. 3. Mercuric chloride augmented the GABA-induced current to 115% of control at 0.1 microM and to 270% of control at 100 microM. It also generated a slowly developing inward current carried by a variety of ions. In contrast, methylmercury suppressed the GABA-induced current. The potent stimulation of the GABA system by mercuric chloride is deemed important in mercury intoxication. 4. Copper and zinc suppressed the GABA-induced current with an EC50 of 16 and 19 microM, respectively. They bound to a common site on the external surface of the GABA receptor-channel complex. 5. Lanthanum augmented the GABA-induced current with an EC50 of 230 microM by increasing the affinity of the receptor for GABA. It bound to a site on or near the external surface of the GABA receptor-channel complex which is different from the sites for GABA, barbiturates, benzodiazepines, picrotoxin, and copper/zinc. 6. Six other lanthanides with larger atomic numbers also exerted the same stimulatory effect with their efficacies increasing with the atomic number. 7. Single-channel analyses have revealed that the augmentation of whole-cell current by terbium, a lanthanide, is due to three actions: an increase in the overall mean open time, a decrease in the overall mean closed time, and an increase in the overall mean burst time.
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Affiliation(s)
- T Narahashi
- Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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Sumikawa K, Nishizaki T. The amino acid residues 1-128 in the alpha subunit of the nicotinic acetylcholine receptor contain assembly signals. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1994; 25:257-64. [PMID: 7808225 DOI: 10.1016/0169-328x(94)90161-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Expression of nicotinic acetylcholine receptor (AChR) involves complex processes including assembly of different receptor subunits into hetero-oligomers. To identify the minimal N-terminal region involved in AChR subunit association, we used a dominant negative assay. Co-expression of fragments of the alpha subunit, containing the N-terminal extracellular domain and transmembrane domain 1 (TM 1), with the parental AChR subunits in Xenopus oocytes blocked functional expression of the receptor. In contrast, co-expression of N-terminal extracellular fragments without TM1 failed to inhibit functional expression of AChRs, but altered the functional properties of co-expressed parental AChRs. Furthermore, when these alpha subunit fragments were co-expressed with the beta, gamma, and delta subunits, they were co-immunoprecipitated with a mixture of beta, gamma, and delta subunit specific antibodies. These results suggest that 'assembly signals' are confined to a local structure in the N-terminal extracellular domain. Our findings also indicate that an assembly step may be a target for genetic intervention not only to block the expression of functional receptors, but also to alter the function of the receptor.
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Affiliation(s)
- K Sumikawa
- Department of Psychobiology, University of California, Irvine 92717-4550
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Schröder B, Reinhardt-Maelicke S, Schrattenholz A, McLane K, Kretschmer A, Conti-Tronconi B, Maelicke A. Monoclonal antibodies FK1 and WF6 define two neighboring ligand binding sites on Torpedo acetylcholine receptor alpha-polypeptide. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34075-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Morgan PJ, Barrett P, Howell HE, Helliwell R. Melatonin receptors: localization, molecular pharmacology and physiological significance. Neurochem Int 1994; 24:101-46. [PMID: 8161940 DOI: 10.1016/0197-0186(94)90100-7] [Citation(s) in RCA: 419] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A pre-requisite to understanding the physiological mechanisms of action of melatonin is the identification of the target sites where the hormone acts. The radioligand 2-[125I]iodo-melatonin has been used extensively to localize binding sites in both the brain and peripheral tissues. In general these binding sites have been found to be high affinity, with Kd in the low picomolar range, and selective for structural analogues of melatonin. Also the affinity of these sites can generally be modulated by guanine nucleotides, consistent with the notion that they are putative G-protein coupled receptors. However, only a few studies have demonstrated that these putative receptors mediate biochemical and cellular responses. In the pars tuberalis (PT) and pars distalis (PD) of the pituitary, the amphibian melanophore and vertebrate retina, evidence indicates that melatonin acts to inhibit intracellular cyclic AMP through a G-protein coupled mechanism, demonstrating that this is a common signal transduction pathway for many melatonin receptors. However in the pars distalis the inhibition of calcium influx and membrane potential are also important mediators of melatonin effects. How many different forms or states of the melatonin receptor exist is unknown, but clearly the identification of the structure of the melatonin receptor(s) and its ability to interact with different G-proteins and signal transduction pathways are quintessential to our understanding of the physiological mechanisms of action of melatonin. In parallel the recent development of new melatonin analogues will greatly aid our understanding of the pharmacology of the melatonin receptor both in terms of the development of potent melatonin receptor antagonists and for the definition of receptor sub-types. The wide species and phylogenic diversity of melatonin binding sites in the brain has probably generated more questions than answers. Nevertheless the localization of melatonin receptors to the suprachiasmatic nucleus of the hypothalamus is at least consistent with circadian effects within the foetus and the adult. In contrast the PT of the pituitary presents an enigma in relation to the seasonal effects of melatonin. A model of how melatonin might mediate the timing of the circannual events through the PT is proposed.
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Affiliation(s)
- P J Morgan
- Rowett Research Institute, Aberdeen, Bucksburn, Scotland
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Kawano H, Sashihara S, Mita T, Ohno K, Kawamura M, Yoshii K. Phenytoin, an antiepileptic drug, competitively blocked non-NMDA receptors produced by Xenopus oocytes. Neurosci Lett 1994; 166:183-6. [PMID: 8177496 DOI: 10.1016/0304-3940(94)90481-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The blocking effect of phenytoin (PHT) and other antiepileptic agents on the glutamate receptors was investigated under voltage-clamp conditions using Xenopus oocytes that translated ddY-stock mouse brain mRNA. PHT shifted the concentration-response curve for kainate to right without significant block on the maximum response obtained, indicating that PHT competitively blocks the non-NMDA receptors. An apparent dissociation constant of PHT was 1.9 x 10(-4) M. The block was voltage-independent. Other antiepileptic agents examined hardly blocked the kainate responses except phenobarbital that blocked the responses. The possibility that the competitive block constitutes a part of the antiepileptic action of PHT was discussed.
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Affiliation(s)
- H Kawano
- Department of Molecular Biology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
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Girard S, Clapham DE. Simultaneous near ultraviolet and visible excitation confocal microscopy of calcium transients in Xenopus oocytes. Methods Cell Biol 1994; 40:263-84. [PMID: 8201979 DOI: 10.1016/s0091-679x(08)61118-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- S Girard
- Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905
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Ikeda SR, Soler F, Zühlke RD, Joho RH, Lewis DL. Heterologous expression of the human potassium channel Kv2.1 in clonal mammalian cells by direct cytoplasmic microinjection of cRNA. Pflugers Arch 1992; 422:201-3. [PMID: 1283219 DOI: 10.1007/bf00370422] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The cloned human delayed rectifying K+ channel Kv2.1 (drk1) was expressed in clonal mouse fibroblasts (L-cells) and rat basophilic leukemia cells (RBL-1) by direct cytoplasmic microinjection of complementary RNA (cRNA). Within six hours, cells microinjected with Kv2.1 cRNA expressed a large sustained outward current as determined from whole-cell patch-clamp recordings. Nearly 100% of cells injected with cRNA expressed outward current. Current density was 30-70 pA/pF when measured at a potential of +50 mV. Steady-state activation and inactivation parameters for Kv2.1 were similar when expressed in either L-cells or RBL-1 cells. These results are the first to demonstrate that functional ion channel proteins can be expressed in mammalian clonal cell lines by direct cytoplasmic microinjection of cRNA.
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Affiliation(s)
- S R Ikeda
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta 30912
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38
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Krafte DS, Volberg WA. Properties of endogenous voltage-dependent sodium currents in Xenopus laevis oocytes. J Neurosci Methods 1992; 43:189-93. [PMID: 1383646 DOI: 10.1016/0165-0270(92)90028-c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Endogenous voltage-dependent sodium currents were recorded using standard 2-microelectrode techniques in Xenopus laevis oocytes. Maximal inward current occurred at -10 mV with an average amplitude of -279 +/- 17 nA and steady-state inactivation was half-maximal at a voltage of -38 +/- 0.5 mV. Currents were blocked by low concentrations of tetrodotoxin (TTX) with an IC50 value of 6 nM. These properties make the endogenous sodium current in Xenopus oocytes similar to sodium currents expressed following injection of mammalian brain RNA. While endogenous sodium channels have the potential to complicate analysis when using the oocyte expression system, they are only present at significant levels in rare batches of oocytes (less than 5%). Our results do stress the need, however, to reproduce results from exogenous expression studies across several batches of oocytes from different donors.
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Affiliation(s)
- D S Krafte
- Department of Cardiovascular Pharmacology, Sterling Winthrop Pharmaceuticals Research Division, Rensselaer, NY 12144
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Sumikawa K. Sequences on the N-terminus of ACh receptor subunits regulate their assembly. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1992; 13:349-53. [PMID: 1320723 DOI: 10.1016/0169-328x(92)90218-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Mutant alpha subunits of Torpedo acetylcholine receptors (AChR) were constructed and expressed in Xenopus oocytes together with other normal subunits to investigate regions in the subunit that are required for subunit assembly. I have found that chimeric alpha subunits, consisting of the N-terminal extracellular domain of the AChR alpha subunit, followed either by the hydrophobic transmembrane segments of GABAA receptor or glutamate receptor subunits, were still recognized as the AChR subunit and associated with co-expressed other normal AChR subunits, suggesting that this part of the N-terminal extracellular domain contains 'assembly signals'.
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Affiliation(s)
- K Sumikawa
- Department of Psychobiology, University of California, Irvine 92717-4550
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Krafte DS, Lester HA. Use of stage II-III Xenopus oocytes to study voltage-dependent ion channels. Methods Enzymol 1992; 207:339-45. [PMID: 1382189 DOI: 10.1016/0076-6879(92)07022-g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Stage II-III Xenopus oocytes represent a useful extension of the standard Xenopus oocyte expression system. The oocytes are smaller; the reduction in membrane area, and therefore capacitance, leads to a faster settling time during a voltage clamp step. In addition, there appears to be less Ca(2+)-activated chloride current; this may render the stage II-III oocyte a useful system for studying K+ channels, where chloride currents can be a significant problem. Conversely, though, these early stage oocytes may not be useful for expression of neurotransmitter receptors coupled to phospholipase C, for such receptors are often monitored by activation of the Cl-current. The injections of RNA are technically more difficult in stage II-III oocytes. This can, however, be overcome with some simple modifications of the injection apparatus, mainly inclusion of a pump or similar device for actual injections.
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Gu Y, Forsayeth JR, Verrall S, Yu XM, Hall ZW. Assembly of the mammalian muscle acetylcholine receptor in transfected COS cells. J Biophys Biochem Cytol 1991; 114:799-807. [PMID: 1869588 PMCID: PMC2289901 DOI: 10.1083/jcb.114.4.799] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We have investigated the mechanisms of assembly and transport to the cell surface of the mouse muscle nicotinic acetylcholine receptor (AChR) in transiently transfected COS cells. In cells transfected with all four subunit cDNAs, AChR was expressed on the surface with properties resembling those seen in mouse muscle cells (Gu, Y., A. F. Franco, Jr., P.D. Gardner, J. B. Lansman, J. R. Forsayeth, and Z. W. Hall. 1990. Neuron. 5:147-157). When incomplete combinations of AChR subunits were expressed, surface binding of 125I-alpha-bungarotoxin was not detected except in the case of alpha beta gamma which expressed less than 15% of that seen with all four subunits. Immunoprecipitation and sucrose gradient sedimentation experiments showed that in cells expressing pairs of subunits, alpha delta and alpha gamma heterodimers were formed, but alpha beta was not. When three subunits were expressed, alpha delta beta and alpha gamma beta complexes were formed. Variation of the ratios of the four subunit cDNAs used in the transfection mixture showed that surface AChR expression was decreased by high concentrations of delta or gamma cDNAs in a mutually competitive manner. High expression of delta or gamma subunits also each inhibited formation of a heterodimer with alpha and the other subunit. These results are consistent with a defined pathway for AChR assembly in which alpha delta and alpha gamma heterodimers are formed first, followed by association with the beta subunit and with each other to form the complete AChR.
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Affiliation(s)
- Y Gu
- Department of Physiology, School of Medicine, University of California, San Francisco 94143-0444
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Saedi MS, Conroy WG, Lindstrom J. Assembly of Torpedo acetylcholine receptors in Xenopus oocytes. J Biophys Biochem Cytol 1991; 112:1007-15. [PMID: 1999453 PMCID: PMC2288882 DOI: 10.1083/jcb.112.5.1007] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To study pathways by which acetylcholine receptor (AChR) subunits might assemble, Torpedo alpha subunits were expressed in Xenopus oocytes alone or in combination with beta, gamma, or delta subunits. The maturation of the conformation of the main immunogenic region (MIR) on alpha subunits was measured by binding of mAbs and the maturation of the conformation of the AChR binding site on alpha subunits was measured by binding of alpha-bungarotoxin (alpha Bgt) and cholinergic ligands. The size of subunits and subunit complexes was assayed by sedimentation on sucrose gradients. It is generally accepted that native AChRs have the subunit composition alpha 2 beta gamma delta. Torpedo alpha subunits expressed alone resulted in an amorphous range of complexes with little affinity for alpha Bgt or mAbs to the MIR, rather than in a unique 5S monomeric assembly intermediate species. A previously recognized temperature-dependent failure in alpha subunit maturation may cause instability of the monomeric assembly intermediate and accumulation of aggregated denatured alpha subunits. Coexpression of alpha with beta subunits also resulted in an amorphous range of complexes. However, coexpression of alpha subunits with gamma or delta subunits resulted in the efficient formation of 6.5S alpha gamma or alpha delta complexes with high affinity for mAbs to the MIR, alpha Bgt, and small cholinergic ligands. These alpha gamma and alpha delta subunit pairs may represent normal assembly intermediates in which Torpedo alpha is stabilized and matured in conformation. Coexpression of alpha, gamma, and delta efficiently formed 8.8S complexes, whereas complexes containing alpha beta and gamma or alpha beta and delta subunits are formed less efficiently. Assembly of beta subunits with complexes containing alpha gamma and delta subunits may normally be a rate-limiting step in assembly of AChRs.
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Affiliation(s)
- M S Saedi
- Salk Institute for Biological Studies, La Jolla, California 92093
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Abstract
Receptor-based assays have benefitted from the newest advances in biotechnology and electronics in three main ways: genetically engineered cells expressing single receptor subtypes have been developed for many natural and synthetic ligands; assays have been designed which take advantage of a variety of signals triggered in cells by binding, or inhibition of binding, of ligands to surface-bound receptors; and radiolabelled ligand assays have been considerably improved and simplified by novel electronic devices.
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Affiliation(s)
- A D Strosberg
- CNRS, Université Paris VII, Institut Cochin de Génétique Moléculaire, France
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Bertrand D, Cooper E, Valera S, Rungger D, Ballivet M. Electrophysiology of Neuronal Nicotinic Acetylcholine Receptors Expressed in Xenopus Oocytes following Nuclear Injection of Genes or cDNAs. METHODS IN NEUROSCIENCES 1991. [DOI: 10.1016/b978-0-12-185257-3.50017-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Abstract
Glutamate receptor subtypes mediating excitatory synaptic neurotransmission in the cerebellar cortex are briefly reviewed from molecular biological, electrophysiological and pharmacological points of view. In particular, molecular biological findings of a novel family of AMPA-selective glutamate receptors are introduced, and the pharmacological and electrophysiological properties and the identity of cerebellar N-methyl-D-aspartate-sensitive receptors probably existing on Purkinje cells are discussed in comparison with well-established cerebral NMDA receptors. As possible intracellular mechanisms of the long-term depression of parallel fiber-Purkinje cell neurotransmission, the perspective of the roles of novel messengers, nitric oxide and arachidonic acid, is particularly commented based on recent information about cerebral long-term events. The specificity and possible independence of cerebellar excitatory amino acid receptors and linked intracellular second messengers are also suggested, taking the highly active guanylate cyclase system in Purkinje cells and other cerebellum-specific proteins into consideration.
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Affiliation(s)
- K Okamoto
- Department of Pharmacology, National Defense Medical College, Saitama, Japan
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Witzemann V, Stein E, Barg B, Konno T, Koenen M, Kues W, Criado M, Hofmann M, Sakmann B. Primary structure and functional expression of the alpha-, beta-, gamma-, delta- and epsilon-subunits of the acetylcholine receptor from rat muscle. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 194:437-48. [PMID: 1702709 DOI: 10.1111/j.1432-1033.1990.tb15637.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The isolation and characterization of five clones carrying sequences of the alpha-, beta-, gamma-, delta- and epsilon-subunit precursors of the rat muscle acetylcholine receptor (AChR) are described. The deduced amino acid sequences indicate that these polypeptides contain 457-519 amino acids and reveal the structural characteristics common to subunits of ligand-gated ion channels. The pattern of subunit-specific mRNA levels in rat muscle shows characteristic changes during development and following denervation, suggesting that innervation of muscle reduces the expression of the alpha-, beta- and delta-subunit mRNAs, suppresses the expression of the gamma-subunit mRNA, and induces expression of epsilon-subunit mRNA. Subunit-specific cRNAs generated in vitro were injected into Xenopus laevis oocytes, resulting in the assembly of two functionally different AChR channel subtypes. The AChR gamma, composed of the alpha-, beta-, gamma- and delta-subunits, has functional properties similar to those of the native AChRs in fetal muscle. The AChR epsilon, composed of alpha-, beta-, delta- and epsilon-subunits, corresponds to the end-plate channel of the adult muscle. Thus in rat skeletal muscle the motor nerve regulates the expression of two functionally different AChR subtypes with different molecular composition by the differential expression of subunit-specific mRNAs.
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Affiliation(s)
- V Witzemann
- Max-Planck-Institut für medizinische Forschung, Abteilung Zellphysiologie, Heidelberg, Federal Republic of Germany
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Conroy WG, Saedi MS, Lindstrom J. TE671 cells express an abundance of a partially mature acetylcholine receptor alpha subunit which has characteristics of an assembly intermediate. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(18)45789-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Buckley NJ, Hulme EC, Birdsall NJ. Use of clonal cell lines in the analysis of neurotransmitter receptor mechanisms and function. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1055:43-53. [PMID: 2171675 DOI: 10.1016/0167-4889(90)90089-v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- N J Buckley
- National Institute for Medical Research, Division of Physical Biochemistry, The Ridgeway, London, U.K
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50
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Mochida S, Poulain B, Eisel U, Binz T, Kurazono H, Niemann H, Tauc L. Exogenous mRNA encoding tetanus or botulinum neurotoxins expressed in Aplysia neurons. Proc Natl Acad Sci U S A 1990; 87:7844-8. [PMID: 2236000 PMCID: PMC54846 DOI: 10.1073/pnas.87.20.7844] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Injection of exogenous mRNA purified from various tissue preparations into cellular translation systems such as Xenopus oocytes has allowed expression of complex proteins (e.g., receptors for neurotransmitters). No evidence for expression of injected exogenous mRNA, however, has been reported in terminally differentiated neurons. If achieved, it would allow the study of long-lasting changes of properties of nerve cells in their functional context. To obtain evidence of such expression, we chose two proteins that produce a detectable effect even at very low intracellular concentrations. Tetanus toxin and botulinum neurotoxin fulfill this criterion, being the most potent neurotoxins known. Both toxins block neurotransmitter release at nanomolar intracellular concentrations. These di-chain proteins, consisting of a light chain and a heavy chain, have recently been sequenced. Their active sites are located (or partly located) on the light chain. mRNAs encoding the light chain of either toxin were transcribed in vitro from the cloned and specifically truncated genes of Clostridium tetani and Clostridium botulinum, respectively, and injected into presynaptic cholinergic neurons of the buccal ganglia of Aplysia californica. Depression of neurotransmitter release appeared in less than 1 hr, demonstrating successful expression of foreign mRNA injected into a neuron in situ.
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Affiliation(s)
- S Mochida
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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