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Coombs ID, Farrant M. An unexpected role for a glutamate receptor. Science 2023; 382:1363-1364. [PMID: 38127768 DOI: 10.1126/science.adm6771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
γ-Aminobutyric acid acts on a glutamate receptor, evoking synaptic plasticity.
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Affiliation(s)
- Ian D Coombs
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, UK
| | - Mark Farrant
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, UK
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Coombs I, Bats C, Sexton CA, Studniarczyk D, Cull-Candy SG, Farrant M. Enhanced functional detection of synaptic calcium-permeable AMPA receptors using intracellular NASPM. eLife 2023; 12:e66765. [PMID: 37042655 PMCID: PMC10168695 DOI: 10.7554/elife.66765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 04/11/2023] [Indexed: 04/13/2023] Open
Abstract
Calcium-permeable AMPA-type glutamate receptors (CP-AMPARs) contribute to many forms of synaptic plasticity and pathology. They can be distinguished from GluA2-containing calcium-impermeable AMPARs by the inward rectification of their currents, which reflects voltage-dependent channel block by intracellular spermine. However, the efficacy of this weakly permeant blocker is differentially altered by the presence of AMPAR auxiliary subunits - including transmembrane AMPAR regulatory proteins, cornichons, and GSG1L - which are widely expressed in neurons and glia. This complicates the interpretation of rectification as a measure of CP-AMPAR expression. Here, we show that the inclusion of the spider toxin analog 1-naphthylacetyl spermine (NASPM) in the intracellular solution results in a complete block of GluA1-mediated outward currents irrespective of the type of associated auxiliary subunit. In neurons from GluA2-knockout mice expressing only CP-AMPARs, intracellular NASPM, unlike spermine, completely blocks outward synaptic currents. Thus, our results identify a functional measure of CP-AMPARs, that is unaffected by their auxiliary subunit content.
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Affiliation(s)
- Ian Coombs
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Cécile Bats
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Craig A Sexton
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Dorota Studniarczyk
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College LondonLondonUnited Kingdom
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Coombs ID, Ziobro J, Krotov V, Surtees T, Cull‐Candy SG, Farrant M. A gain-of-function GRIA2 variant associated with neurodevelopmental delay and seizures: Functional characterization and targeted treatment. Epilepsia 2022; 63:e156-e163. [PMID: 36161652 PMCID: PMC10092096 DOI: 10.1111/epi.17419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 01/11/2023]
Abstract
α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs) are ligand-gated cationic channels formed from combinations of GluA1-4 subunits. Pathogenic variants of GRIA1-4 have been described in patients with developmental delay, intellectual disability, autism spectrum disorder, and seizures, with GRIA2 variants typically causing AMPAR loss of function. Here, we identify a novel, heterozygous de novo pathogenic missense mutation in GRIA2 (c.1928 C>T, p.A643V, NM_001083619.1) in a 1-year-old boy with epilepsy, developmental delay, and failure to thrive. We made patch-clamp recordings to compare the functional and pharmacological properties of variant and wild-type receptors expressed in HEK293 cells, with and without the transmembrane AMPAR regulatory protein γ2. This showed GluA2 A643V-containing AMPARs to exhibit a novel gain of function, with greatly slowed deactivation, markedly reduced desensitization, and increased glutamate sensitivity. Perampanel, an antiseizure AMPAR negative allosteric modulator, was able to fully block GluA2 A643V/γ2 currents, suggesting potential therapeutic efficacy. The subsequent introduction of perampanel to the patient's treatment regimen was associated with a marked reduction in seizure burden, a resolution of failure to thrive, and clear developmental gains. Our study reveals that GRIA2 disorder can be caused by a gain-of-function variant, and both predicts and suggests the therapeutic efficacy of perampanel. Perampanel may prove beneficial for patients with other gain-of-function GRIA variants.
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Affiliation(s)
- Ian D. Coombs
- Department of Neuroscience, Physiology, and PharmacologyUniversity College LondonLondonUK
| | - Julie Ziobro
- Department of PediatricsUniversity of MichiganAnn ArborMichiganUSA
| | - Volodymyr Krotov
- Department of Neuroscience, Physiology, and PharmacologyUniversity College LondonLondonUK
| | - Taryn‐Leigh Surtees
- Department of NeurologyWashington University in St Louis School of MedicineSt LouisMissouriUSA
| | - Stuart G. Cull‐Candy
- Department of Neuroscience, Physiology, and PharmacologyUniversity College LondonLondonUK
| | - Mark Farrant
- Department of Neuroscience, Physiology, and PharmacologyUniversity College LondonLondonUK
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Farrant M. Philip Canning Farrant. BMJ 2022. [DOI: 10.1136/bmj.o1463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Coombs ID, Sexton CA, Cull-Candy SG, Farrant M. Influence of the TARP γ8-Selective Negative Allosteric Modulator JNJ-55511118 on AMPA Receptor Gating and Channel Conductance. Mol Pharmacol 2022; 101:343-356. [PMID: 35246481 PMCID: PMC7615793 DOI: 10.1124/molpharm.121.000473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 02/11/2022] [Indexed: 11/22/2022] Open
Abstract
AMPA-type gultamate receptors (AMPARs) mediate excitatory signaling in the brain and are therapeutic targets for the treatment of diverse neurological disorders. The receptors interact with a variety of auxiliary subunits, including the transmembrane AMPAR regulatory proteins (TARPs). The TARPs influence AMPAR biosynthesis and trafficking and enhance receptor responses by slowing desensitization and deactivation and increasing single-channel conductance. TARP γ8 has an expression pattern that is distinct from that of other TARPs, being enriched in the hippocampus. Recently, several compounds have been identified that selectivity inhibit γ8-containing AMPARs. One such inhibitor, JNJ-55511118, has shown considerable promise for the treatment of epilepsy. However, key details of its mechanism of action are still lacking. Here, using patch-clamp electrophysiological recording from heterologously expressed AMPARs, we show that JNJ-55511118 inhibits peak currents of γ8-containing AMPARs by decreasing their single-channel conductance. The drug also modifies hallmark features of AMPAR pharmacology, including the TARP-dependent actions of intracellular polyamines and the partial agonist kainate. Moreover, we find that JNJ-55511118 reduces the influence of γ8 on all biophysical measures, aside from its effect on the recovery from desensitization. The drug is also effective when applied intracellularly, suggesting it may access its binding site from within the membrane. Additionally, we find that AMPARs incorporating TARP γ2 mutated to contain the JNJ-55511118 binding site, exhibit greater block than seen with AMPARs containing γ8, potentially reflecting differences in TARP stoichiometry. Taken together, our data provide new insight into the mechanism by which γ8-selective drugs inhibit AMPARs. SIGNIFICANCE STATEMENT: Although modulation of AMPA-type glutamate receptors shows promise for the treatment various neurological conditions, the absence of subtype-selective drugs has hindered adoption of this therapeutic strategy. We made patch-clamp recordings to characterize the actions of the γ8-selective AMPAR inhibitor JNJ-55511118 on GluA2(Q) receptors expressed in HEK cells. We report that JNJ-55511118 inhibits AMPAR-mediated currents by reducing single-channel conductance, providing clear insight into the mechanism of action of this important class of AMPAR modulators.
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Affiliation(s)
- Ian D Coombs
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Craig A Sexton
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
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Magno L, Asgarian Z, Pendolino V, Velona T, Mackintosh A, Lee F, Stryjewska A, Zimmer C, Guillemot F, Farrant M, Clark B, Kessaris N. Transient developmental imbalance of cortical interneuron subtypes presages long-term changes in behavior. Cell Rep 2021; 35:109249. [PMID: 34133916 PMCID: PMC8220254 DOI: 10.1016/j.celrep.2021.109249] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 04/02/2021] [Accepted: 05/22/2021] [Indexed: 11/16/2022] Open
Abstract
Cortical GABAergic interneurons are generated in large numbers in the ganglionic eminences and migrate into the cerebral cortex during embryogenesis. At early postnatal stages, during neuronal circuit maturation, autonomous and activity-dependent mechanisms operate within the cortex to adjust cell numbers by eliminating naturally occurring neuron excess. Here, we show that when cortical interneurons are generated in aberrantly high numbers-due to a defect in precursor cell proliferation during embryogenesis-extra parvalbumin interneurons persist in the postnatal mouse cortex during critical periods of cortical network maturation. Even though cell numbers are subsequently normalized, behavioral abnormalities remain in adulthood. This suggests that timely clearance of excess cortical interneurons is critical for correct functional maturation of circuits that drive adult behavior.
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Affiliation(s)
- Lorenza Magno
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Zeinab Asgarian
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Valentina Pendolino
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Theodora Velona
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Albert Mackintosh
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Flora Lee
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Agata Stryjewska
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Celine Zimmer
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Beverley Clark
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK; Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Nicoletta Kessaris
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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Cull‐Candy SG, Farrant M. Ca 2+ -permeable AMPA receptors and their auxiliary subunits in synaptic plasticity and disease. J Physiol 2021; 599:2655-2671. [PMID: 33533533 PMCID: PMC8436767 DOI: 10.1113/jp279029] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 01/28/2021] [Indexed: 12/14/2022] Open
Abstract
AMPA receptors are tetrameric glutamate-gated ion channels that mediate a majority of fast excitatory neurotransmission in the brain. They exist as calcium-impermeable (CI-) and calcium-permeable (CP-) subtypes, the latter of which lacks the GluA2 subunit. CP-AMPARs display an array of distinctive biophysical and pharmacological properties that allow them to be functionally identified. This has revealed that they play crucial roles in diverse forms of central synaptic plasticity. Here we summarise the functional hallmarks of CP-AMPARs and describe how these are modified by the presence of auxiliary subunits that have emerged as pivotal regulators of AMPARs. A lasting change in the prevalence of GluA2-containing AMPARs, and hence in the fraction of CP-AMPARs, is a feature in many maladaptive forms of synaptic plasticity and neurological disorders. These include modifications of glutamatergic transmission induced by inflammatory pain, fear conditioning, cocaine exposure, and anoxia-induced damage in neurons and glia. Furthermore, defective RNA editing of GluA2 can cause altered expression of CP-AMPARs and is implicated in motor neuron damage (amyotrophic lateral sclerosis) and the proliferation of cells in malignant gliomas. A number of the players involved in CP-AMPAR regulation have been identified, providing useful insight into interventions that may prevent the aberrant CP-AMPAR expression. Furthermore, recent molecular and pharmacological developments, particularly the discovery of TARP subtype-selective drugs, offer the exciting potential to modify some of the harmful effects of increased CP-AMPAR prevalence in a brain region-specific manner.
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Affiliation(s)
- Stuart G. Cull‐Candy
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
| | - Mark Farrant
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
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Coombs ID, Soto D, McGee TP, Gold MG, Farrant M, Cull-Candy SG. Homomeric GluA2(R) AMPA receptors can conduct when desensitized. Nat Commun 2019; 10:4312. [PMID: 31541113 PMCID: PMC6754398 DOI: 10.1038/s41467-019-12280-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 08/28/2019] [Indexed: 11/21/2022] Open
Abstract
Desensitization is a canonical property of ligand-gated ion channels, causing progressive current decline in the continued presence of agonist. AMPA-type glutamate receptors (AMPARs), which mediate fast excitatory signaling throughout the brain, exhibit profound desensitization. Recent cryo-EM studies of AMPAR assemblies show their ion channels to be closed in the desensitized state. Here we present evidence that homomeric Q/R-edited AMPARs still allow ions to flow when the receptors are desensitized. GluA2(R) expressed alone, or with auxiliary subunits (γ-2, γ-8 or GSG1L), generates large fractional steady-state currents and anomalous current-variance relationships. Our results from fluctuation analysis, single-channel recording, and kinetic modeling, suggest that the steady-state current is mediated predominantly by conducting desensitized receptors. When combined with crystallography this unique functional readout of a hitherto silent state enabled us to examine cross-linked cysteine mutants to probe the conformation of the desensitized ligand binding domain of functioning AMPAR complexes. AMPA-type glutamate receptors, which mediate fast excitatory signaling throughout the brain, exhibit profound desensitization, causing a progressive current decline in the continued presence of agonist. Here authors show that homomeric Q/R edited AMPARs still allow ions to flow when the receptors are desensitized.
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Affiliation(s)
- Ian D Coombs
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - David Soto
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.,Department of Biomedicine, Neurophysiology Laboratory, Medical School, Institute of Neurosciences, University of Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Thomas P McGee
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Matthew G Gold
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Lalanne T, Oyrer J, Farrant M, Sjöström PJ. Synapse Type-Dependent Expression of Calcium-Permeable AMPA Receptors. Front Synaptic Neurosci 2018; 10:34. [PMID: 30369875 PMCID: PMC6194349 DOI: 10.3389/fnsyn.2018.00034] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/24/2018] [Indexed: 12/13/2022] Open
Abstract
Calcium-permeable (CP) AMPA-type glutamate receptors (AMPARs) are known to mediate synaptic plasticity in several different interneuron (IN) types. Recent evidence suggests that CP-AMPARs are synapse-specifically expressed at excitatory connections onto a subset of IN types in hippocampus and neocortex. For example, CP-AMPARs are found at connections from pyramidal cells (PCs) to basket cells (BCs), but not to Martinotti cells (MCs). This synapse type-specific expression of CP-AMPARs suggests that synaptic dynamics as well as learning rules are differentially implemented in local circuits and has important implications not just in health but also in disease states such as epilepsy.
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Affiliation(s)
- Txomin Lalanne
- Department of Biomedicine, Institute of Physiology, University of Basel, Basel, Switzerland
| | - Julia Oyrer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - P Jesper Sjöström
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, Montreal General Hospital, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada
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Studniarczyk D, Needham EL, Mitchison HM, Farrant M, Cull-Candy SG. Altered Cerebellar Short-Term Plasticity but No Change in Postsynaptic AMPA-Type Glutamate Receptors in a Mouse Model of Juvenile Batten Disease. eNeuro 2018; 5:ENEURO.0387-17.2018. [PMID: 29780879 PMCID: PMC5956745 DOI: 10.1523/eneuro.0387-17.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 03/22/2018] [Accepted: 03/27/2018] [Indexed: 12/28/2022] Open
Abstract
Juvenile Batten disease is the most common progressive neurodegenerative disorder of childhood. It is associated with mutations in the CLN3 gene, causing loss of function of CLN3 protein and degeneration of cerebellar and retinal neurons. It has been proposed that changes in granule cell AMPA-type glutamate receptors (AMPARs) contribute to the cerebellar dysfunction. In this study, we compared AMPAR properties and synaptic transmission in cerebellar granule cells from wild-type and Cln3 knock-out mice. In Cln3Δex1-6 cells, the amplitude of AMPA-evoked whole-cell currents was unchanged. Similarly, we found no change in the amplitude, kinetics, or rectification of synaptic currents evoked by individual quanta, or in their underlying single-channel conductance. We found no change in cerebellar expression of GluA2 or GluA4 protein. By contrast, we observed a reduced number of quantal events following mossy-fiber stimulation in Sr2+, altered short-term plasticity in conditions of reduced extracellular Ca2+, and reduced mossy fiber vesicle number. Thus, while our results suggest early presynaptic changes in the Cln3Δex1-6 mouse model of juvenile Batten disease, they reveal no evidence for altered postsynaptic AMPARs.
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Affiliation(s)
- Dorota Studniarczyk
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Elizabeth L. Needham
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Hannah M. Mitchison
- UCL Great Ormond Street Institute of Child Health, University College London, London WC1N 1EH, United Kingdom
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Stuart G. Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
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Sheiybani G, Brydon P, Toolan M, Linehan J, Farrant M, Colleypriest B. Does rectal diclofenac reduce post-ERCP pancreatitis? A district general hospital experience. Frontline Gastroenterol 2018; 9:73-77. [PMID: 29484164 PMCID: PMC5824769 DOI: 10.1136/flgastro-2017-100832] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 06/08/2017] [Accepted: 07/03/2017] [Indexed: 02/04/2023] Open
Abstract
INTRODUCTION There is controversy in the literature recently regarding the efficacy of rectal non-steroidal anti-inflammatory drugs (NSAID) to prevent post-ERCP pancreatitis (PEP). The aim of this study was to compare the incidence of PEP in three distinct groups of patients at the Royal United Hospital, Bath: no use of rectal diclofenac, selective use and blanket use without contraindication. METHOD Readmission data, blood results, radiology reports and discharge summaries were used to identify patients with PEP from August 2010 to December 2015. The administration of rectal diclofenac postprocedure was recorded from the endoscopy reporting system. RESULTS 1318 endoscopic retrograde cholangiopancreatographies (ERCP) were performed by four endoscopists during the study period with 66 (5.0%) cases of pancreatitis. 445 ERCPs were performed prior to the introduction of NSAID use during which time, with an incidence of 35 (7.9%) episodes of PEP. During the selective period of NSAID use (high-risk patients) 539 ERCPs were performed and 72 (13.4%) patients received NSAIDs. 17 (3.2%) developed PEP. 334 ERCPs were performed when NSAIDs were given to all patients without contraindication. 289 (86.5%) of patients received rectal diclofenac and 13 (3.9%) developed pancreatitis. There is a statistically significant decrease in PEP comparing the groups of patients receiving NSAIDs selectively (p=0.0009) or routinely (p=0.0172) when compared with none. There is no difference between the selective and routine group (p=0.571). CONCLUSION Our data demonstrate that the introduction of a selective or routine use of NSAIDs for PEP in a District General Hospital (DGH) significantly decreases the risk of pancreatitis (risk reduction 43.7%).
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Affiliation(s)
| | - Peter Brydon
- Gastroenterology, Royal United Hospital, Bath, UK
| | | | - John Linehan
- Gastroenterology, Royal United Hospital, Bath, UK
| | - Mark Farrant
- Gastroenterology, Royal United Hospital, Bath, UK
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Coombs I, Tarasiuk A, Marconi L, Shelley C, Farrant M, Cull-Candy SG. Multiple Subconductance States of Tarped AMPA Receptors Revealed by Slow Dissociation of Antagonist. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Lalanne T, Oyrer J, Mancino A, Gregor E, Chung A, Huynh L, Burwell S, Maheux J, Farrant M, Sjöström PJ. Synapse-specific expression of calcium-permeable AMPA receptors in neocortical layer 5. J Physiol 2015; 594:837-61. [PMID: 26537662 PMCID: PMC4753277 DOI: 10.1113/jp271394] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 11/01/2015] [Indexed: 01/26/2023] Open
Abstract
Key points In the hippocampus, calcium‐permeable AMPA receptors have been found in a restricted subset of neuronal types that inhibit other neurons, although their localization in the neocortex is less well understood. In the present study, we looked for calcium‐permeable AMPA receptors in two distinct populations of neocortical inhibitory neurons: basket cells and Martinotti cells. We found them in the former but not in the latter. Furthermore, in basket cells, these receptors were associated with particularly fast responses. Computer modelling predicted (and experiments verified) that fast calcium‐permeable AMPA receptors enable basket cells to respond rapidly, such that they promptly inhibit neighbouring cells and shut down activity. The results obtained in the present study help our understanding of pathologies such as stroke and epilepsy that have been associated with disordered regulation of calcium‐permeable AMPA receptors.
Abstract AMPA‐type glutamate receptors (AMPARs) lacking an edited GluA2 subunit are calcium‐permeable (CP) and contribute to synaptic plasticity in several hippocampal interneuron types, although their precise role in the neocortex is not well described. We explored the presence of CP‐AMPARs at pyramidal cell (PC) inputs to Martinotti cells (MCs) and basket cells (BCs) in layer 5 of the developing mouse visual cortex (postnatal days 12–21). GluA2 immunolabelling was stronger in MCs than in BCs. A differential presence of CP‐AMPARs at PC‐BC and PC‐MC synapses was confirmed electrophysiologically, based on measures of spermine‐dependent rectification and CP‐AMPAR blockade by 1‐naphtyl acetyl spermine using recordings from synaptically connected cell pairs, NPEC‐AMPA uncaging and miniature current recordings. In addition, CP‐AMPAR expression in BCs was correlated with rapidly decaying synaptic currents. Computer modelling predicted that this reduces spike latencies and sharpens suprathreshold responses in BCs, which we verified experimentally using the dynamic clamp technique. Thus, the synapse‐specific expression of CP‐AMPARs may critically influence both plasticity and information processing in neocortical microcircuits. In the hippocampus, calcium‐permeable AMPA receptors have been found in a restricted subset of neuronal types that inhibit other neurons, although their localization in the neocortex is less well understood. In the present study, we looked for calcium‐permeable AMPA receptors in two distinct populations of neocortical inhibitory neurons: basket cells and Martinotti cells. We found them in the former but not in the latter. Furthermore, in basket cells, these receptors were associated with particularly fast responses. Computer modelling predicted (and experiments verified) that fast calcium‐permeable AMPA receptors enable basket cells to respond rapidly, such that they promptly inhibit neighbouring cells and shut down activity. The results obtained in the present study help our understanding of pathologies such as stroke and epilepsy that have been associated with disordered regulation of calcium‐permeable AMPA receptors.
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Affiliation(s)
- Txomin Lalanne
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.,Integrated Program in Neuroscience, McGill University, Montreal, Quebec, Canada
| | - Julia Oyrer
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Adamo Mancino
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Erica Gregor
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Andrew Chung
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Louis Huynh
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Sasha Burwell
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Jérôme Maheux
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - P Jesper Sjöström
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada.,Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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14
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Zonouzi M, Scafidi J, Li P, McEllin B, Edwards J, Dupree JL, Harvey L, Sun D, Hübner CA, Cull-Candy SG, Farrant M, Gallo V. GABAergic regulation of cerebellar NG2 cell development is altered in perinatal white matter injury. Nat Neurosci 2015; 18:674-82. [PMID: 25821912 PMCID: PMC4459267 DOI: 10.1038/nn.3990] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/06/2015] [Indexed: 01/11/2023]
Abstract
Diffuse white matter injury (DWMI), a leading cause of neurodevelopmental disabilities in preterm infants, is characterized by reduced oligodendrocyte formation. NG2-expressing oligodendrocyte precursor cells (NG2 cells) are exposed to various extrinsic regulatory signals, including the neurotransmitter GABA. We investigated GABAergic signaling to cerebellar white matter NG2 cells in a mouse model of DWMI (chronic neonatal hypoxia). We found that hypoxia caused a loss of GABAA receptor-mediated synaptic input to NG2 cells, extensive proliferation of these cells and delayed oligodendrocyte maturation, leading to dysmyelination. Treatment of control mice with a GABAA receptor antagonist or deletion of the chloride-accumulating transporter NKCC1 mimicked the effects of hypoxia. Conversely, blockade of GABA catabolism or GABA uptake reduced NG2 cell numbers and increased the formation of mature oligodendrocytes both in control and hypoxic mice. Our results indicate that GABAergic signaling regulates NG2 cell differentiation and proliferation in vivo, and suggest that its perturbation is a key factor in DWMI.
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MESH Headings
- Action Potentials/drug effects
- Animals
- Animals, Newborn
- Asphyxia Neonatorum/pathology
- Carbachol/pharmacology
- Cell Count
- Cells, Cultured
- Cerebellum/growth & development
- Cerebellum/pathology
- Demyelinating Diseases/chemically induced
- Demyelinating Diseases/etiology
- Disease Models, Animal
- Female
- GABA-A Receptor Antagonists/toxicity
- Hypoxia, Brain/pathology
- Hypoxia, Brain/physiopathology
- Interneurons/pathology
- Male
- Mice
- Mice, Knockout
- Mice, Transgenic
- Neural Stem Cells/cytology
- Neurogenesis/drug effects
- Neurogenesis/physiology
- Nipecotic Acids/pharmacology
- Nipecotic Acids/therapeutic use
- Oligodendroglia/cytology
- Purkinje Cells/pathology
- Receptors, GABA-A/physiology
- Solute Carrier Family 12, Member 2/deficiency
- Solute Carrier Family 12, Member 2/physiology
- Tiagabine
- Vigabatrin/pharmacology
- Vigabatrin/therapeutic use
- White Matter/injuries
- gamma-Aminobutyric Acid/physiology
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Affiliation(s)
- Marzieh Zonouzi
- 1] Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA. [2] Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Joseph Scafidi
- 1] Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA. [2] Department of Neurology, Children's National Medical Center, Washington, DC, USA
| | - Peijun Li
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA
| | - Brian McEllin
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA
| | - Jorge Edwards
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA
| | - Jeffrey L Dupree
- Department of Anatomy and Neurobiology, Virginia Commonwealth University, Medical Center, Richmond, Virginia, USA
| | - Lloyd Harvey
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Christian A Hübner
- Friedrich-Schiller-University Jena, Institute of Human Genetics, Jena University Hospital, Jena, Germany
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Vittorio Gallo
- Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC, USA
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15
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Palles C, Chegwidden L, Li X, Findlay JM, Farnham G, Castro Giner F, Peppelenbosch MP, Kovac M, Adams CL, Prenen H, Briggs S, Harrison R, Sanders S, MacDonald D, Haigh C, Tucker A, Love S, Nanji M, deCaestecker J, Ferry D, Rathbone B, Hapeshi J, Barr H, Moayyedi P, Watson P, Zietek B, Maroo N, Gay L, Underwood T, Boulter L, McMurtry H, Monk D, Patel P, Ragunath K, Al Dulaimi D, Murray I, Koss K, Veitch A, Trudgill N, Nwokolo C, Rembacken B, Atherfold P, Green E, Ang Y, Kuipers EJ, Chow W, Paterson S, Kadri S, Beales I, Grimley C, Mullins P, Beckett C, Farrant M, Dixon A, Kelly S, Johnson M, Wajed S, Dhar A, Sawyer E, Roylance R, Onstad L, Gammon MD, Corley DA, Shaheen NJ, Bird NC, Hardie LJ, Reid BJ, Ye W, Liu G, Romero Y, Bernstein L, Wu AH, Casson AG, Fitzgerald R, Whiteman DC, Risch HA, Levine DM, Vaughan TL, Verhaar AP, van den Brande J, Toxopeus EL, Spaander MC, Wijnhoven BPL, van der Laan LJW, Krishnadath K, Wijmenga C, Trynka G, McManus R, Reynolds JV, O'Sullivan J, MacMathuna P, McGarrigle SA, Kelleher D, Vermeire S, Cleynen I, Bisschops R, Tomlinson I, Jankowski J. Polymorphisms near TBX5 and GDF7 are associated with increased risk for Barrett's esophagus. Gastroenterology 2015; 148:367-78. [PMID: 25447851 PMCID: PMC4315134 DOI: 10.1053/j.gastro.2014.10.041] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 10/19/2014] [Accepted: 10/21/2014] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Barrett's esophagus (BE) increases the risk of esophageal adenocarcinoma (EAC). We found the risk to be BE has been associated with single nucleotide polymorphisms (SNPs) on chromosome 6p21 (within the HLA region) and on 16q23, where the closest protein-coding gene is FOXF1. Subsequently, the Barrett's and Esophageal Adenocarcinoma Consortium (BEACON) identified risk loci for BE and esophageal adenocarcinoma near CRTC1 and BARX1, and within 100 kb of FOXP1. We aimed to identify further SNPs that increased BE risk and to validate previously reported associations. METHODS We performed a genome-wide association study (GWAS) to identify variants associated with BE and further analyzed promising variants identified by BEACON by genotyping 10,158 patients with BE and 21,062 controls. RESULTS We identified 2 SNPs not previously associated with BE: rs3072 (2p24.1; odds ratio [OR] = 1.14; 95% CI: 1.09-1.18; P = 1.8 × 10(-11)) and rs2701108 (12q24.21; OR = 0.90; 95% CI: 0.86-0.93; P = 7.5 × 10(-9)). The closest protein-coding genes were respectively GDF7 (rs3072), which encodes a ligand in the bone morphogenetic protein pathway, and TBX5 (rs2701108), which encodes a transcription factor that regulates esophageal and cardiac development. Our data also supported in BE cases 3 risk SNPs identified by BEACON (rs2687201, rs11789015, and rs10423674). Meta-analysis of all data identified another SNP associated with BE and esophageal adenocarcinoma: rs3784262, within ALDH1A2 (OR = 0.90; 95% CI: 0.87-0.93; P = 3.72 × 10(-9)). CONCLUSIONS We identified 2 loci associated with risk of BE and provided data to support a further locus. The genes we found to be associated with risk for BE encode transcription factors involved in thoracic, diaphragmatic, and esophageal development or proteins involved in the inflammatory response.
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Affiliation(s)
- Claire Palles
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.
| | - Laura Chegwidden
- Plymouth University Peninsula School of Medicine and Dentistry, Plymouth, Devon, UK
| | - Xinzhong Li
- Centre of Biostatistics, Bioinformatics and Biomarkers, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, Devon, UK
| | - John M Findlay
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Garry Farnham
- Plymouth University Peninsula School of Medicine and Dentistry, Plymouth, Devon, UK
| | | | - Maikel P Peppelenbosch
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Michal Kovac
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Claire L Adams
- Plymouth University Peninsula School of Medicine and Dentistry, Plymouth, Devon, UK
| | - Hans Prenen
- Department of Digestive Oncology, University Hospital Gasthuisberg, Leuven, Belgium
| | - Sarah Briggs
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Rebecca Harrison
- Department of Pathology, Leicester Royal Infirmary, Leicester, UK
| | - Scott Sanders
- Department of Cellular Pathology, Warwick Hospital, Warwick, UK
| | - David MacDonald
- Department of Oral Biological and Medical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Chris Haigh
- Department of Gastroenterology, Wansbeck General Hospital, Ashington, Northumberland, UK
| | - Art Tucker
- William Harvey Research Institute, The Ernest Cooke Vascular & Microvascular Unit, Centre for Clinical Pharmacology, St Bartholomew's Hospital, London, UK
| | - Sharon Love
- Centre for Statistics in Medicine and Oxford Clinical Trials Research Unit, Oxford, UK
| | - Manoj Nanji
- Centre for Digestive Diseases, Queen Mary University of London, London, UK
| | - John deCaestecker
- Department of Gastroenterology, Leicester General Hospital, Leicester, UK
| | - David Ferry
- Department of Oncology, New Cross Hospital, Royal Wolverhampton Hospitals NHS Trust, Wolverhampton, UK
| | - Barrie Rathbone
- Department for Gastroenterology, Leicester Royal Infirmary, Leicester, UK
| | - Julie Hapeshi
- Gloucestershire Royal Hospital, Great Western Road, Gloucester, UK
| | - Hugh Barr
- Department of Upper GI Surgery, Gloucestershire, Royal Hospital, Gloucester, UK
| | - Paul Moayyedi
- Department of Medicine, McMaster HC, Hamilton Ontario, Canada
| | - Peter Watson
- School of Medicine, Dentistry, and Biomedical Sciences, Centre for Public Health, Queens University Belfast, NI
| | - Barbara Zietek
- Centre for Digestive Diseases, Queen Mary University of London, London, UK
| | - Neera Maroo
- Centre for Digestive Diseases, Queen Mary University of London, London, UK
| | - Laura Gay
- Centre for Digestive Diseases, Queen Mary University of London, London, UK
| | - Tim Underwood
- University of Southampton, Southampton General Hospital, Tremona Road, Southampton, UK
| | - Lisa Boulter
- University of Southampton, Southampton General Hospital, Tremona Road, Southampton, UK
| | - Hugh McMurtry
- Lancashire Teaching Hospitals NHS Foundation Trust, Royal Preston Hospital, Lancashire, UK
| | - David Monk
- General Surgery, Countess of Chester Hospital, Chester, UK
| | - Praful Patel
- Southampton University Hospitals NHS Trust, Southampton, UK
| | - Krish Ragunath
- Wolfson Digestive Diseases Centre, Queens Medical Centre, Nottingham, UK
| | - David Al Dulaimi
- Worcestershire Acute Hospitals NHS Trust, Alexandra Hospital, Redditch, UK
| | - Iain Murray
- Department of Gastroenterology, Royal Cornwall Hospital, Truro, Cornwall, UK
| | - Konrad Koss
- Macclesfield General Hospital, Macclefield, Cheshire, UK
| | - Andrew Veitch
- Department of Oncology, New Cross Hospital, Royal Wolverhampton Hospitals NHS Trust, Wolverhampton, UK
| | - Nigel Trudgill
- Department of Gastroenterology, Sandwell General Hospital, Lyndon, West Bromwich, UK
| | - Chuka Nwokolo
- Department of Gastroenterology, University Hospital of Coventry, Coventry, UK
| | - Bjorn Rembacken
- Department of Gastroenterology, Leeds General Infirmary, Leeds, UK
| | - Paul Atherfold
- Department of Clinical Pharmacology University of Oxford, Oxford, UK
| | - Elaine Green
- School of Biomedical & Healthcare Sciences, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, UK
| | - Yeng Ang
- Gastroenterology, Royal Albert Edward Infirmary NHS Trust, Wigan, UK; GI Science Centre, Salford Royal NHS Foundation Trust, University of Manchester, Salford, UK
| | - Ernst J Kuipers
- Department of Gastroenterology and Hepatology, Department of Internal Medicine, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Wu Chow
- Forth Valley Royal Hospital, Larbert, Scotland, UK
| | - Stuart Paterson
- Norfolk and Norwich University Hospitals NHS Foundation Trust, Norfolk and Norwich University Hospital, Norwich, UK
| | - Sudarshan Kadri
- Department for Gastroenterology, Leicester Royal Infirmary, Leicester, UK
| | - Ian Beales
- Burnley General Hospital, Burnley, Lancashire, UK
| | - Charles Grimley
- Head of Gastroenterology, University Hospital of Northern BC, Prince George, British Columbia, Canada
| | - Paul Mullins
- Bradford Teaching Hospitals NHS Foundation Trust, Bradford Royal Infirmary, Bradford, UK
| | - Conrad Beckett
- Royal United Hospital Bath NHS Trust, Royal United Hospital, Avon, Bath, Somerset, UK
| | - Mark Farrant
- Kettering General Hospital NHS Foundation Trust, Kettering General Hospital, Rothwell Road, Kettering, Northants, UK
| | - Andrew Dixon
- York Teaching Hospital NHS Foundation Trust, York, UK
| | - Sean Kelly
- Luton and Dunstable University Hospital NHS Foundation Trust, Luton, Bedfordshire, UK
| | - Matthew Johnson
- Department of Thoracic and Upper Gastrointestinal Surgery, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
| | - Shahjehan Wajed
- County and Durham and Darlington NHS Foundation Trust, Bishop Auckland, County Durham, UK
| | - Anjan Dhar
- Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - Elinor Sawyer
- Barts Cancer Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, UK
| | - Rebecca Roylance
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Centre, Seattle, Washington
| | - Lynn Onstad
- Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, North Carolina
| | - Marilie D Gammon
- Division of Research and San Francisco Medical Center, Kaiser Permanente Northern California, California
| | - Douglas A Corley
- Division of Gastroenterology and Hepatology, UNC School of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | | | - Nigel C Bird
- Division of Epidemiology, University of Leeds, Leeds, UK
| | - Laura J Hardie
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Brian J Reid
- Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, North Carolina; Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Weimin Ye
- Princess Margaret Cancer Centre, Ontario Cancer Institute, Toronto, ON, Canada
| | - Geoffrey Liu
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota
| | - Yvonne Romero
- Registry, On behalf of the Romero; Department of Population Sciences, Beckman Research Institute and City of Hope Comprehensive Cancer Center, Duarte, California
| | - Leslie Bernstein
- Department of Preventive Medicine, University of Southern California/Norris Comprehensive Cancer Center, Los Angeles, California
| | - Anna H Wu
- Department of Surgery, University of Saskatchewan, Saskatoon, Canada
| | - Alan G Casson
- MRC Cancer Cell Unit, Hutchison-MRC Research Centre and University of Cambridge, Cambridge, UK
| | - Rebecca Fitzgerald
- Cancer Control, QIMR Berghofer Medical Research Institute, Queensland, Australia
| | - David C Whiteman
- Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, Connecticut
| | - Harvey A Risch
- Department of Biostatistics, University of Washington School of Public Health, Seattle, Washington
| | - David M Levine
- Department of Gastroenterology, Tergooi Hospital, Hilversum, The Netherlands
| | - Tom L Vaughan
- Department of Epidemiology, University of North Carolina School of Public Health, Chapel Hill, North Carolina
| | - Auke P Verhaar
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Jan van den Brande
- Department of Surgery, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Eelke L Toxopeus
- Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Manon C Spaander
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Bas P L Wijnhoven
- Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Luc J W van der Laan
- Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
| | - Kausilia Krishnadath
- Department of Genetics, University Medical Centre Groningen and University of Groningen, The Netherlands
| | - Cisca Wijmenga
- Department of Clinical Medicine & Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James's Hospital, Dublin, Ireland
| | - Gosia Trynka
- Department of Clinical Medicine & Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St James's Hospital, Dublin, Ireland
| | - Ross McManus
- Department of Surgery, Trinity Centre for Health Sciences, Trinity College Dublin, St. James' Hospital, Dublin, Ireland
| | - John V Reynolds
- Gastrointestinal Unit, Mater Misericordiae University Hospital, University College Dublin, Dublin, Ireland
| | - Jacintha O'Sullivan
- Gastrointestinal Unit, Mater Misericordiae University Hospital, University College Dublin, Dublin, Ireland
| | - Padraic MacMathuna
- Faculty of Medicine, Imperial College London, South Kensington Campus, London, UK
| | - Sarah A McGarrigle
- Gastrointestinal Unit, Mater Misericordiae University Hospital, University College Dublin, Dublin, Ireland
| | - Dermot Kelleher
- Faculty of Medicine, Imperial College, South Kensington Campus, London, UK
| | - Severine Vermeire
- Department of Digestive Oncology, University Hospital Gasthuisberg, Leuven, Belgium
| | - Isabelle Cleynen
- Department of Digestive Oncology, University Hospital Gasthuisberg, Leuven, Belgium
| | - Raf Bisschops
- Department of Digestive Oncology, University Hospital Gasthuisberg, Leuven, Belgium
| | - Ian Tomlinson
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.
| | - Janusz Jankowski
- University Hospitals Coventry & Warwickshire NHS Trust, Warwickshire, England; Warwick Medical School, University of Warwick, Warwickshire, England.
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16
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Pasley T, Farrant M, Amir N, Young S. Primary adrenal insufficiency in a 19-year-old male presenting with cardiomyopathy. Heart Lung Circ 2015. [DOI: 10.1016/j.hlc.2015.06.249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Cais O, Herguedas B, Krol K, Cull-Candy SG, Farrant M, Greger IH. Mapping the interaction sites between AMPA receptors and TARPs reveals a role for the receptor N-terminal domain in channel gating. Cell Rep 2014; 9:728-40. [PMID: 25373908 PMCID: PMC4405707 DOI: 10.1016/j.celrep.2014.09.029] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/12/2014] [Accepted: 09/19/2014] [Indexed: 11/18/2022] Open
Abstract
AMPA-type glutamate receptors (AMPARs) mediate fast neurotransmission at excitatory synapses. The extent and fidelity of postsynaptic depolarization triggered by AMPAR activation are shaped by AMPAR auxiliary subunits, including the transmembrane AMPAR regulatory proteins (TARPs). TARPs profoundly influence gating, an effect thought to be mediated by an interaction with the AMPAR ion channel and ligand binding domain (LBD). Here, we show that the distal N-terminal domain (NTD) contributes to TARP modulation. Alterations in the NTD-LBD linker result in TARP-dependent and TARP-selective changes in AMPAR gating. Using peptide arrays, we identify a TARP interaction region on the NTD and define the path of TARP contacts along the LBD surface. Moreover, we map key binding sites on the TARP itself and show that mutation of these residues mediates gating modulation. Our data reveal a TARP-dependent allosteric role for the AMPAR NTD and suggest that TARP binding triggers a drastic reorganization of the AMPAR complex. The NTD linker has a TARP-dependent and TARP-specific impact on AMPAR gating Peptide arrays reveal binding of TARPs to both extracellular domains of AMPARs A structural reorganization of AMPARs is triggered by TARP binding
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Affiliation(s)
- Ondrej Cais
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Beatriz Herguedas
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Karolina Krol
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Stuart G Cull-Candy
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Mark Farrant
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Ingo H Greger
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
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18
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Bats C, Farrant M, Cull-Candy SG. A role of TARPs in the expression and plasticity of calcium-permeable AMPARs: evidence from cerebellar neurons and glia. Neuropharmacology 2013; 74:76-85. [PMID: 23583927 PMCID: PMC3751754 DOI: 10.1016/j.neuropharm.2013.03.037] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/21/2013] [Accepted: 03/28/2013] [Indexed: 02/04/2023]
Abstract
The inclusion of GluA2 subunits has a profound impact on the channel properties of AMPA receptors (AMPARs), in particular rendering them impermeable to calcium. While GluA2-containing AMPARs are the most abundant in the central nervous system, GluA2-lacking calcium-permeable AMPARs are also expressed in wide variety of neurons and glia. Accumulating evidence suggests that the dynamic control of the GluA2 content of AMPARs plays a critical role in development, synaptic plasticity, and diverse neurological conditions ranging from ischemia-induced brain damage to drug addiction. It is thus important to understand the molecular mechanisms involved in regulating the balance of AMPAR subtypes, particularly the role of their co-assembled auxiliary subunits. The discovery of transmembrane AMPAR regulatory proteins (TARPs), initially within the cerebellum, has transformed the field of AMPAR research. It is now clear that these auxiliary subunits play a key role in multiple aspects of AMPAR trafficking and function in the brain. Yet, their precise role in AMPAR subtype-specific regulation has only recently received particular attention. Here we review recent findings on the differential regulation of calcium-permeable (CP-) and -impermeable (CI-) AMPARs in cerebellar neurons and glial cells, and discuss the critical involvement of TARPs in this process. This article is part of the Special Issue entitled ‘Glutamate Receptor-Dependent Synaptic Plasticity’. Calcium-permeable AMPARs are present in various cerebellar neurons and glial cells. The contribution of calcium-permeable AMPARs to transmission is dynamically regulated. TARPs influence the relative expression of AMPAR subtypes. Evidence suggests that TARPs play a role in calcium-permeable AMPAR plasticity.
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Affiliation(s)
- Cécile Bats
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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19
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Shelley C, Farrant M, Cull-Candy SG. TARP-associated AMPA receptors display an increased maximum channel conductance and multiple kinetically distinct open states. J Physiol 2012; 590:5723-38. [PMID: 22988139 DOI: 10.1113/jphysiol.2012.238006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Fast excitatory synaptic transmission in the CNS is mediated mainly by AMPA-type glutamate receptors (AMPARs), whose biophysical properties are dramatically modulated by the presence of transmembrane AMPAR regulatory proteins (TARPs). To help construct a kinetic model that will realistically describe native AMPAR/TARP function, we have examined the single-channel properties of homomeric GluA1 AMPARs in combination with the TARPs, γ-2, γ-4 and γ-5. In a saturating concentration of agonist, each of these AMPAR/TARP combinations gave rise to single-channel currents with multiple conductance levels that appeared intrinsic to the receptor-channel complex, and showed long-lived subconductance states. The open time and burst length distributions of the receptor complexes displayed multiple dwell-time components. In the case of γ-2- and γ-4-associated receptors, these distributions included a long-lived component lasting tens of milliseconds that was absent from both GluA1 alone and γ-5-associated receptors. The open time distributions for each conductance level required two dwell-time components, indicating that at each conductance level the channel occupies a minimum of two kinetically distinct open states. We have explored how these data place novel constraints on possible kinetic models of TARP-associated AMPARs that may be used to define AMPAR-mediated synaptic transmission.
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Affiliation(s)
- Chris Shelley
- Department of Neuroscience, University College London, Gower Street, London WC1E 6BT, UK
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20
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Bats C, Soto D, Studniarczyk D, Farrant M, Cull-Candy SG. Channel properties reveal differential expression of TARPed and TARPless AMPARs in stargazer neurons. Nat Neurosci 2012; 15:853-61. [PMID: 22581185 PMCID: PMC3427011 DOI: 10.1038/nn.3107] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 04/10/2012] [Indexed: 12/14/2022]
Abstract
Dynamic regulation of calcium-permeable (CP-) AMPARs is important in normal synaptic transmission, plasticity and pathological changes. While the involvement of TARPs in trafficking of calcium-impermeable (CI-) AMPARs has been extensively studied, their role in surface expression and function of CP-AMPARs remains unclear. Here we examined AMPAR-mediated currents in cerebellar stellate cells from stargazer mice, lacking the prototypical TARP stargazin (γ-2). We found a marked increase in the contribution of CP-AMPARs to synaptic responses, indicating that, unlike CI-AMPARs, these can localize at synapses in the absence of γ-2. In contrast with CP-AMPARs in extrasynaptic regions, synaptic CP-AMPARs displayed an unexpectedly low channel conductance and strong block by intracellular spermine, suggesting they were ‘TARPless’. As proof of principle that TARP-association is not an absolute requirement for AMPAR clustering at synapses, mEPSCs mediated by TARPless AMPARs were readily detected in stargazer granule cells following knock down of their only other TARP, γ-7.
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Affiliation(s)
- Cécile Bats
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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Shelley C, Renzi M, Zonouzi M, Coombs I, Soto D, Farrant M, Cull-Candy SG. Functional Effects of Cornichon Proteins on Homomeric Glua1 AMPAR Single-Channels. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.1673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Longcroft-Wheaton G, Marden P, Colleypriest B, Gavin D, Taylor G, Farrant M. Understanding why patients die after gastrostomy tube insertion: a retrospective analysis of mortality. JPEN J Parenter Enteral Nutr 2009; 33:375-9. [PMID: 19339748 DOI: 10.1177/0148607108327156] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVES To understand the causes of mortality of inpatients receiving a percutaneous endoscopic gastrostomy (PEG) tube compared with a survival curve predicted from a model proposed by Levine et al (2007). DESIGN A retrospective study of patients receiving a PEG over an 18-month period. SETTING Royal United Hospital Bath, a district general hospital in the southwest of England. PATIENTS Fifty-five cases, with 44 found eligible for inclusion. INTERVENTIONS A Levine score was calculated for this cohort. A survival curve after PEG was produced and compared with the Kaplan-Meier curve predicted by the Levine model. MAIN OUTCOME MEASURES Mortality over a period of 1 year. RESULTS The mortality at 1, 3, 6, and 12 months was 16%, 20%, 25%, and 28%, respectively. This matched the predicted death rate from the Levine model closely (Pearson's rank correlation coefficient = 0.96). CONCLUSIONS The authors found that the mortality of patients receiving a PEG followed that predicted for a similar cohort of patients without PEGs in the Levine model. This suggests that the deaths observed were due to underlying comorbidities, can provide a baseline for mortality targets for PEG services, and is useful patient information regarding the risks and benefits of the procedure. The findings demonstrate that PEG does no harm and supports the accepted opinion that nutrition support is associated with a better outcome. Furthermore, they show that most deaths occur within the first month of placement and would support arguments for delaying placement until outcome from the underlying condition is more predictable.
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Abstract
Among principal neurons, adult Purkinje cells have long been considered unusual in lacking functional NMDA receptors. This view has emerged largely from studies on rats, where NMDA receptors are expressed in Purkinje cells of newborn animals, but are lost after 2 weeks. By contrast, immunolabelling data have shown that Purkinje cells from adult mice express multiple NMDA receptor subunits, suggesting a possible species difference. To investigate the presence of functional NMDA receptors in Purkinje cells of mice, and to explore the contribution of different receptor subunits, we made whole-cell and single-channel patch-clamp recordings from Purkinje cells of wild-type and NR2D-/- mice of different ages. Here we report that multiple NMDA receptor subtypes are indeed expressed in Purkinje cells of young and adult mice; in the adult, both NR2A- and NR2B-containing subtypes are present. Furthermore, we show that NMDA receptor-mediated EPSCs can be evoked by climbing fibre stimulation, and appear to be mediated mainly by NR2A-containing receptors.
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Affiliation(s)
- Massimiliano Renzi
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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25
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Soto D, Coombs ID, Kelly L, Farrant M, Cull-Candy SG. Stargazin attenuates intracellular polyamine block of calcium-permeable AMPA receptors. Nat Neurosci 2007; 10:1260-7. [PMID: 17873873 PMCID: PMC2430330 DOI: 10.1038/nn1966] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Accepted: 07/20/2007] [Indexed: 11/09/2022]
Abstract
Endogenous polyamines profoundly affect the activity of various ion channels, including that of calcium-permeable AMPA-type glutamate receptors (CP-AMPARs). Here we show that stargazin, a transmembrane AMPAR regulatory protein (TARP) known to influence transport, gating and desensitization of AMPARs, greatly reduces block of CP-AMPARs by intracellular polyamines. By decreasing CP-AMPAR affinity for cytoplasmic polyamines, stargazin enhances the charge transfer following single glutamate applications and eliminates the frequency-dependent facilitation seen with repeated applications. In cerebellar stellate cells, which express both synaptic CP-AMPARs and stargazin, we found that the rectification and unitary conductance of channels underlying excitatory postsynaptic currents were matched by those of recombinant AMPARs only when the latter were associated with stargazin. Taken together, our observations establish modulatory actions of stargazin that are specific to CP-AMPARs, and suggest that during synaptic transmission the activity of such receptors, and thus calcium influx, is fundamentally changed by TARPs.
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Affiliation(s)
- David Soto
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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26
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Wulff P, Goetz T, Leppä E, Linden AM, Renzi M, Swinny JD, Vekovischeva OY, Sieghart W, Somogyi P, Korpi ER, Farrant M, Wisden W. From synapse to behavior: rapid modulation of defined neuronal types with engineered GABAA receptors. Nat Neurosci 2007; 10:923-9. [PMID: 17572671 PMCID: PMC2092503 DOI: 10.1038/nn1927] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 05/22/2007] [Indexed: 11/09/2022]
Abstract
In mammals, identifying the contribution of specific neurons or networks to behavior is a key challenge. Here we describe an approach that facilitates this process by enabling the rapid modulation of synaptic inhibition in defined cell populations. Binding of zolpidem, a systemically active allosteric modulator that enhances the function of the GABAA receptor, requires a phenylalanine residue (Phe77) in the gamma2 subunit. Mice in which this residue is changed to isoleucine are insensitive to zolpidem. By Cre recombinase-induced swapping of the gamma2 subunit (that is, exchanging Ile77 for Phe77), zolpidem sensitivity can be restored to GABAA receptors in chosen cell types. We demonstrate the power of this method in the cerebellum, where zolpidem rapidly induces significant motor deficits when Purkinje cells are made uniquely sensitive to its action. This combined molecular and pharmacological technique has demonstrable advantages over targeted cell ablation and will be invaluable for investigating many neuronal circuits.
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Affiliation(s)
- Peer Wulff
- Department of Clinical Neurobiology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany.
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Quinlan JM, Colleypriest BJ, Farrant M, Tosh D. Epithelial metaplasia and the development of cancer. Biochim Biophys Acta Rev Cancer 2007; 1776:10-21. [PMID: 17618050 DOI: 10.1016/j.bbcan.2007.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 05/17/2007] [Accepted: 05/18/2007] [Indexed: 01/15/2023]
Abstract
Metaplasia means the conversion, in postnatal life, of one cell type to another. Understanding the steps leading to metaplasia is important for two reasons. Firstly, it tells us something about the normal developmental biology of the tissues that interconvert. Secondly, metaplasia predisposes to certain forms of neoplasia. So understanding the molecular and cellular mechanisms underlying metaplasia will provide insights into clinical diagnosis and potential therapies. One of the best-described examples of metaplasia is Barrett's metaplasia or the appearance of intestinal-like columnar tissue in the oesophagus. Barrett's metaplasia develops as a result of gastro-oesophageal reflux and is considered the precursor lesion for oesophageal adenocarcinoma. While we know quite a bit about the molecular events associated with the development of oesophageal adenocarcinoma, our understanding of the initial events leading to Barrett's metaplasia is lacking. In the present review we will focus on examples of metaplasia that lead to neoplasia and discuss some of the underlying molecular and cellular mechanisms.
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Affiliation(s)
- Jonathan M Quinlan
- Centre for Regenerative Medicine, Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, UK
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28
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Abstract
GABA(A) receptors mediate fast synaptic inhibition in the CNS. Whilst this is undoubtedly true, it is a gross oversimplification of their actions. The receptors themselves are diverse, being formed from a variety of subunits, each with a different temporal and spatial pattern of expression. This diversity is reflected in differences in subcellular targetting and in the subtleties of their response to GABA. While activation of the receptors leads to an inevitable increase in membrane conductance, the voltage response is dictated by the distribution of the permeant Cl(-) and HCO(3)(-) ions, which is established by anion transporters. Similar to GABA(A) receptors, the expression of these transporters is not only developmentally regulated but shows cell-specific and subcellular variation. Untangling all these complexities allows us to appreciate the variety of GABA-mediated signalling, a diverse set of phenomena encompassing both synaptic and non-synaptic functions that can be overtly excitatory as well as inhibitory.
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Affiliation(s)
- Mark Farrant
- Department of Pharmacology, UCL (University College London), Gower Street, London WC1E 6BT, UK.
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Cull-Candy S, Kelly L, Farrant M. Regulation of Ca2+-permeable AMPA receptors: synaptic plasticity and beyond. Curr Opin Neurobiol 2006; 16:288-97. [PMID: 16713244 DOI: 10.1016/j.conb.2006.05.012] [Citation(s) in RCA: 357] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 05/08/2006] [Indexed: 12/13/2022]
Abstract
AMPA-type glutamate receptors (AMPARs) mediate most fast excitatory synaptic transmission in the brain. Diversity in excitatory signalling arises, in part, from functional differences among AMPAR subtypes. Although the rapid insertion or deletion of AMPARs is recognised as important for the expression of conventional forms of long-term synaptic plasticity--triggered, for example, by Ca2+ entry through NMDA-type glutamate receptors--only recently has attention focused on novel forms of plasticity that are regulated by, or alter the expression of, Ca2+-permeable AMPARs. The dynamic regulation of these receptors is important for normal synaptic function and in disease states.
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Affiliation(s)
- Stuart Cull-Candy
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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30
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Abstract
The proper functioning of the adult mammalian brain relies on the orchestrated regulation of neural activity by a diverse population of GABA (gamma-aminobutyric acid)-releasing neurons. Until recently, our appreciation of GABA-mediated inhibition focused predominantly on the GABA(A) (GABA type A) receptors located at synaptic contacts, which are activated in a transient or 'phasic' manner by GABA that is released from synaptic vesicles. However, there is growing evidence that low concentrations of ambient GABA can persistently activate certain subtypes of GABA(A) receptor, which are often remote from synapses, to generate a 'tonic' conductance. In this review, we consider the distinct roles of synaptic and extrasynaptic GABA receptor subtypes in the control of neuronal excitability.
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Affiliation(s)
- Mark Farrant
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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Stell BM, Brickley SG, Tang CY, Farrant M, Mody I. Neuroactive steroids reduce neuronal excitability by selectively enhancing tonic inhibition mediated by delta subunit-containing GABAA receptors. Proc Natl Acad Sci U S A 2003; 100:14439-44. [PMID: 14623958 PMCID: PMC283610 DOI: 10.1073/pnas.2435457100] [Citation(s) in RCA: 603] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2003] [Indexed: 11/18/2022] Open
Abstract
Neuroactive steroids are potent modulators of gamma-aminobutyric acid type A receptors (GABAARs), and their behavioral effects are generally viewed in terms of altered inhibitory synaptic transmission. Here we report that, at concentrations known to occur in vivo, neuroactive steroids specifically enhance a tonic inhibitory conductance in central neurons that is mediated by extrasynaptic delta subunit-containing GABAARs. The neurosteroid-induced augmentation of this tonic conductance decreases neuronal excitability. Fluctuations in the circulating concentrations of endogenous neuroactive steroids have been implicated in the genesis of premenstrual syndrome, postpartum depression, and other anxiety disorders. Recognition that delta subunit-containing GABAARs responsible for a tonic conductance are a preferential target for neuroactive steroids may lead to novel pharmacological approaches for the treatment of these common conditions.
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Affiliation(s)
- Brandon M Stell
- Department of Neurology, The David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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Cathala L, Brickley S, Cull-Candy S, Farrant M. Maturation of EPSCs and intrinsic membrane properties enhances precision at a cerebellar synapse. J Neurosci 2003; 23:6074-85. [PMID: 12853426 PMCID: PMC6740347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
The timing of action potentials is an important determinant of information coding in the brain. The shape of the EPSP has a key influence on the temporal precision of spike generation. Here we use dynamic clamp recording and passive neuronal models to study how developmental changes in synaptic conductance waveform and intrinsic membrane properties combine to affect the EPSP and action potential generation in cerebellar granule cells. We recorded EPSCs at newly formed and mature mossy fiber-granule cell synapses. Both quantal and evoked currents showed a marked speeding of the AMPA receptor-mediated component. We also found evidence for age- and activity-dependent changes in the involvement of NMDA receptors. Although AMPA and NMDA receptors contributed to quantal EPSCs at immature synapses, multiquantal release was required to activate NMDA receptors at mature synapses, suggesting a developmental redistribution of NMDA receptors. These changes in the synaptic conductance waveform result in a faster rising EPSP and reduced spike latency in mature granule cells. Mature granule cells also have a significantly decreased input resistance, contributing to a faster decaying EPSP and a reduced spike jitter. We suggest that these concurrent developmental changes, which increase the temporal precision of EPSP-spike coupling, will increase the fidelity with which sensory information is processed within the input layer of the cerebellar cortex.
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Affiliation(s)
- Laurence Cathala
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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Aller MI, Jones A, Merlo D, Paterlini M, Meyer AH, Amtmann U, Brickley S, Jolin HE, McKenzie ANJ, Monyer H, Farrant M, Wisden W. Cerebellar granule cell Cre recombinase expression. Genesis 2003; 36:97-103. [PMID: 12820171 DOI: 10.1002/gene.10204] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The cerebellum maintains balance and orientation, refines motor action, stores motor memories, and contributes to the timing aspects of cognition. We generated two mouse lines for making Cre recombinase-mediated gene disruptions largely confined to adult cerebellar granule cells. For this purpose we chose the GABA(A) receptor alpha6 subunit gene, whose expression marks this cell type. Here we describe mouse lines expressing Cre recombinase generated by 1) Cre knocked into the native alpha6 subunit gene by homologous recombination in embryonic stem cells; and 2) Cre recombined into an alpha6 subunit gene carried on a bacterial artificial chromosome (BAC) genomic clone. The fidelity of Cre expression was tested by crossing the mouse lines with the ROSA26 reporter mice. The particular alpha6BAC clone we identified will be valuable for delivering other gene products to cerebellar granule cells.
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Affiliation(s)
- M I Aller
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK
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Abstract
Cerebellar granule cells receive inhibitory synaptic input from Golgi cells, which is mediated by gamma-aminobutyric acid (GABA) acting on GABA(A) receptors. In the present study we examined the properties of GABAergic inhibitory postsynaptic currents (IPSCs) in granule cells of the rat at a time when they first receive synaptic contacts from Golgi cells. Our results demonstrate that granule cells receive functional GABAergic synaptic input as early as postnatal day three (P3). The kinetic properties of these early IPSCs and the single-channel conductance of the synaptic receptors are similar to those seen at the end of the first postnatal week, suggesting a stable subunit composition during this initial period of development. However, at P3, unlike the situation at more mature synapses, two distinct patterns of synaptic activity are evident, with IPSCs occurring either regularly or in bursts. In addition we find that Golgi cells are spontaneously active during early development, and at P7 most IPSCs are action potential-dependent. Moreover, paired Golgi-granule cell recordings suggest a high level of connectivity and a high release probability at these early synapses.
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Affiliation(s)
- Mark Farrant
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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Brickley SG, Farrant M, Swanson GT, Cull-Candy SG. CNQX increases GABA-mediated synaptic transmission in the cerebellum by an AMPA/kainate receptor-independent mechanism. Neuropharmacology 2001; 41:730-6. [PMID: 11640927 DOI: 10.1016/s0028-3908(01)00135-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
GABA(A) receptor-mediated inhibitory synaptic transmission within the CNS is often studied in the presence of glutamate receptor antagonists. However, for nearly a decade it has been known that, in the hippocampus, one of the most commonly used alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonists, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), can increase the frequency of spontaneous GABA(A) receptor-mediated postsynaptic currents (sIPSCs). In the present study we examined the effect of CNQX and related compounds on GABA-mediated synaptic transmission in the cerebellum. At various stages of development, low concentrations of CNQX increased the frequency of sIPSCs recorded from granule cells. This effect was independent of the blocking action of CNQX on ionotropic glutamate receptors, as it was not observed with the broad-spectrum glutamate receptor antagonist kynurenate. No increase in sIPSC frequency was observed with the NMDA receptor antagonists D-AP5 or 7-ClK, the selective AMPA receptor antagonists GYKI 52466 or GYKI 53655, or the kainate receptor antagonist NS-102. In contrast, two other quinoxaline derivatives, NBQX and DNQX, were capable of increasing sIPSC frequency. These results demonstrate that the novel excitatory action of CNQX, unrelated to blockade of ionotropic glutamate receptors, is not restricted to the hippocampus and can be observed with structurally related compounds.
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Affiliation(s)
- S G Brickley
- Department of Pharmacology, University College London, Gower Street, WC1E 6BT, London, UK
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Abstract
N-methyl-D-aspartate receptors (NMDARs) are present at many excitatory glutamate synapses in the central nervous system and display unique properties that depend on their subunit composition. Biophysical, pharmacological and molecular methods have been used to determine the key features conferred by the various NMDAR subunits, and have helped to establish which NMDAR subtypes are present at particular synapses. Recent studies are beginning to address the functional significance of NMDAR diversity under normal and pathological conditions.
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Affiliation(s)
- S Cull-Candy
- Department of Pharmacology, University College London, Gower Street, WC1E 6BT, London, UK.
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Brickley SG, Revilla V, Cull-Candy SG, Wisden W, Farrant M. Adaptive regulation of neuronal excitability by a voltage-independent potassium conductance. Nature 2001; 409:88-92. [PMID: 11343119 DOI: 10.1038/35051086] [Citation(s) in RCA: 441] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Many neurons receive a continuous, or 'tonic', synaptic input, which increases their membrane conductance, and so modifies the spatial and temporal integration of excitatory signals. In cerebellar granule cells, although the frequency of inhibitory synaptic currents is relatively low, the spillover of synaptically released GABA (gamma-aminobutyric acid) gives rise to a persistent conductance mediated by the GABA A receptor that also modifies the excitability of granule cells. Here we show that this tonic conductance is absent in granule cells that lack the alpha6 and delta-subunits of the GABAA receptor. The response of these granule cells to excitatory synaptic input remains unaltered, owing to an increase in a 'leak' conductance, which is present at rest, with properties characteristic of the two-pore-domain K+ channel TASK-1 (refs 9,10,11,12). Our results highlight the importance of tonic inhibition mediated by GABAA receptors, loss of which triggers a form of homeostatic plasticity leading to a change in the magnitude of a voltage-independent K + conductance that maintains normal neuronal behaviour.
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Affiliation(s)
- S G Brickley
- Department of Pharmacology, University College London, London WC1E 6BT, UK
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Misra C, Brickley SG, Farrant M, Cull-Candy SG. Identification of subunits contributing to synaptic and extrasynaptic NMDA receptors in Golgi cells of the rat cerebellum. J Physiol 2000; 524 Pt 1:147-62. [PMID: 10747189 PMCID: PMC2269854 DOI: 10.1111/j.1469-7793.2000.00147.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/1999] [Accepted: 12/22/1999] [Indexed: 11/29/2022] Open
Abstract
1. To investigate the properties of N-methyl-D-aspartate receptors (NMDARs) in cerebellar Golgi cells, patch-clamp recordings were made in cerebellar slices from postnatal day 14 (P14) rats. To verify cell identity, cells were filled with Neurobiotin and examined using confocal microscopy. 2. The NR2B subunit-selective NMDAR antagonist ifenprodil (10 microM) reduced whole-cell NMDA-evoked currents by approximately 80 %. The NMDA-evoked currents were unaffected by the Zn2+ chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylenediamine (TPEN; 1 microM) suggesting the absence of NMDARs containing NR2A subunits. 3. Outside-out patches from Golgi cells exhibited a population of 'high-conductance' 50 pS NMDAR openings. These were inhibited by ifenprodil, with an IC50 of 19 nM. 4. Patches from these cells also contained 'low-conductance' NMDAR channels, with features characteristic of NR2D subunit-containing receptors. These exhibited a main conductance of 39 pS, with a sub-conductance level of 19 pS, with clear asymmetry of transitions between the two levels. As expected of NR2D-containing receptors, these events were not affected by ifenprodil. 5. The NMDAR-mediated component of EPSCs, evoked by parallel fibre stimulation or occurring spontaneously, was not affected by 1 microM TPEN. However, it was reduced (by approximately 60 %) in the presence of 10 microM ifenprodil, to leave a residual NMDAR-mediated current that exhibited fast decay kinetics. This is, therefore, unlikely to have arisen from receptors composed of NR1/NR2D subunits. 6. We conclude that in cerebellar Golgi cells, the high- and low-conductance NMDAR channels arise from NR2B- and NR2D-containing receptors, respectively. We found no evidence for NR2A-containing receptors in these cells. While NR2B-containing receptors are present in both the synaptic and extrasynaptic membrane, our results indicate that NR1/NR2D receptors do not contribute to the EPSC and appear to be restricted to the extrasynaptic membrane.
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Affiliation(s)
- C Misra
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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Brickley SG, Cull-Candy SG, Farrant M. Single-channel properties of synaptic and extrasynaptic GABAA receptors suggest differential targeting of receptor subtypes. J Neurosci 1999; 19:2960-73. [PMID: 10191314 PMCID: PMC6782265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
Many neurons express a multiplicity of GABAA receptor subunit isoforms. Despite having only a single source of inhibitory input, the cerebellar granule cell displays, at various stages of development, more than 10 different GABAA subunit types. This subunit diversity would be expected to result in significant receptor heterogeneity, yet the functional consequences of such heterogeneity remain poorly understood. Here we have used single-channel properties to characterize GABAA receptor types in the synaptic and extrasynaptic membrane of granule cells. In the presence of high concentrations of GABA, which induced receptor desensitization, extrasynaptic receptors in outside-out patches from the soma entered long-lived closed states interrupted by infrequent clusters of openings. Each cluster of openings, which is assumed to result from the repeated activation of a single channel, was to one of three main conductance states (28, 17, or 12 pS), the relative frequency of which differed between patches. Such behavior indicates the presence of at least three different receptor types. This heterogeneity was not replicated by individual recombinant receptors (alpha1beta2gamma2S or alpha1beta3gamma2S), which gave rise to clusters of a single type only. By contrast, the conductance of synaptic receptors, determined by fluctuation analysis of the synaptic current or direct resolution of channel events, was remarkably uniform and similar to the highest conductance value seen in extrasynaptic patches. These results suggest that granule cells express multiple GABAA receptor types, but only those with a high conductance, most likely containing a gamma subunit, are activated at the synapse.
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Affiliation(s)
- S G Brickley
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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40
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Cull-Candy SG, Brickley SG, Misra C, Feldmeyer D, Momiyama A, Farrant M. NMDA receptor diversity in the cerebellum: identification of subunits contributing to functional receptors. Neuropharmacology 1998; 37:1369-80. [PMID: 9849672 DOI: 10.1016/s0028-3908(98)00119-1] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent studies of N-methyl-D-aspartate (NMDA) receptors have led to the suggestion that there are two distinct classes of native NMDA receptors, identifiable from their single-channel conductance properties. 'High-conductance' openings arise from NR2A- or NR2B-containing receptors, and 'low-conductance' openings arise from NR2C- or NR2D-containing receptors. In addition, the low-conductance channels show reduced sensitivity to block by Mg2+. The readily identified cell types and simple architecture of the cerebellum make it an ideal model system in which to determine the contribution of specific subunits to functional NMDA receptors. Furthermore, mRNA for all of these four NR2 subunits are represented in this brain region. We have examined NMDA channels in Purkinje cells, deep cerebellar nuclei (DCN) neurons and Golgi cells. First we find that NR2D-containing NMDA receptors give rise to low-conductance openings in cell-attached recordings from Purkinje cells. The characteristic conductance of these events cannot, therefore, be ascribed to patch excision. Second, patches from some DCN neurons exhibit mixed populations of high- and low-conductance openings. Third, Golgi cells also exhibit a mixed population of high- and low-conductance NMDA receptor openings. The features of these low-conductance openings are consistent with the presence of NR2D-containing NMDA receptors, as suggested by in situ hybridization data. On the other hand the existence of high-conductance channels, with properties typical of NR2B-containing receptors, was not expected. Our results provide new evidence about the subunit composition of NMDA receptors in identified cerebellar cells, and suggest that examination of single-channel properties is a potentially powerful approach for determining the possible subunit composition of native NMDA receptors.
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Affiliation(s)
- S G Cull-Candy
- Department of Pharmacology, University College London, UK.
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41
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Abstract
In many neurons, responses to individual quanta of transmitter exhibit large variations in amplitude. The origin of this variability, although central to our understanding of synaptic transmission and plasticity, remains controversial. To examine the relationship between quantal amplitude and postsynaptic receptor number, we adopted a novel approach, combining patch-clamp recording of synaptic currents with quantitative immunogold localization of synaptic receptors. Here, we report that in cerebellar stellate cells, where variability in GABA miniature synaptic currents is particularly marked, the distribution of quantal amplitudes parallels that of synaptic GABA(A) receptor number. We also show that postsynaptic GABA(A) receptor density is uniform, allowing synaptic area to be used as a measure of relative receptor content. Flurazepam, which increases GABA(A) receptor affinity, prolongs the decay of all miniature currents but selectively increases the amplitude of large events. From this differential effect, we show that a quantum of GABA saturates postsynaptic receptors when <80 receptors are present but results in incomplete occupancy at larger synapses.
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Affiliation(s)
- Z Nusser
- Department of Pharmacology, University College London, United Kingdom
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Clark BA, Farrant M, Cull-Candy SG. A direct comparison of the single-channel properties of synaptic and extrasynaptic NMDA receptors. J Neurosci 1997; 17:107-16. [PMID: 8987740 PMCID: PMC6793703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The assumption that synaptic and extrasynaptic glutamate receptors are similar underpins many studies that have sought to relate the behavior of channels in excised patches to the macroscopic properties of the EPSC. We have examined this issue for NMDA receptors in cerebellar granule cells, the small size of which allows the opening of individual synaptic NMDA channels to be resolved directly. We have used whole-cell patch-clamp recordings to determine the conductance and open time of NMDA channels activated during the EPSC and used cell-attached and outside-out recordings to examine NMDA receptors in somatic membrane. Conductance and open time of synaptic channels were indistinguishable from those of extrasynaptic channels in cell-attached patches. However, the channel conductance in outside-out patches was 20% lower than in cell-attached recordings. This change was partially reduced by dantrolene and phalloidin, suggesting that it may involve depolymerization of actin following Ca2+ release from intracellular stores. Our results demonstrate that synaptic and extrasynaptic NMDA receptors have similar microscopic properties. However, NMDA channel conductance is reduced following the formation of an outside-out patch.
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Affiliation(s)
- B A Clark
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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Brickley SG, Cull-Candy SG, Farrant M. Development of a tonic form of synaptic inhibition in rat cerebellar granule cells resulting from persistent activation of GABAA receptors. J Physiol 1996; 497 ( Pt 3):753-9. [PMID: 9003560 PMCID: PMC1160971 DOI: 10.1113/jphysiol.1996.sp021806] [Citation(s) in RCA: 609] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. To investigate the origin and functional significance of a recently described tonic GABAA receptor-mediated conductance in cerebellar granule cells we have made recordings from cells in cerebellar slices from rats of different ages (postnatal days P4 to P28). 2. During development there was a dramatic change in the properties of GABA-mediated synaptic transmission. The contribution to GABAA receptor-mediated charge transfer from the tonic conductance (GGABA), relative to that resulting from discrete spontaneous postsynaptic currents (sPSCs), was increased from 5% at P7 to 99% at P21. GGABA was reduced by bicuculline, tetrodotoxin and by lowering extracellular Ca2+, and was initially present only in those cells which exhibited sPSCs. 3. At P7 sPSCs were depolarizing, occasionally triggering a single action potential. By P18 the GABA reversal potential was shifted close to the resting potential and GGABA produced a shunting inhibition. Removal of GGABA by bicuculline increased granule cell excitability in response to current injection. 4. This novel tonic inhibition is present despite the low number of Golgi cell synapses on individual granule cells and appears to result from 'overspill' of synaptically released GABA leading to activation of synaptic and extrasynaptic GABAA receptors.
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Affiliation(s)
- S G Brickley
- Department of Pharmacology, University College London, UK
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44
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Abstract
1. Patch-clamp methods have been used to characterize GABA-and glycine-activated channels and spontaneous synaptic currents in granule cells in thin cerebellar slices from 7- to 20-day-old rats. 2. All granule cells responded to 10 microM GABA, while approximately 60% responded to 100 microM glycine. With repeated against application, whole-cell responses to GABA, but not those to glycine, declined over a period of minutes unless the pipette solution contained Mg-ATP. 3. Whole-cell concentration-response curves gave EC50 values at 45.2 and 99.6 microM and Hill slopes of 0.94 and 2.6 for GABA and glycine, respectively. At saturating concentrations, currents evoked by GABA were fivefold larger than those evoked by glycine. 4. Whole-cell current-voltage (I-V) relationships of GABA- and glycine-activated currents reversed close to the predicted Cl- equilibrium potential. Partial replacement of intracellular Cl- with F- shifted the GABA reversal potential to a more negative value. 'Instantaneous' I-V relationships produced by ionophoretic application of GABA were linear, while 'steady-state' I-V relationships produced by ramp changes in potential showed outward rectification. For glycine, 'steady-state' I-V plots were linear. 5. Responses to GABA were blocked by the GABAA receptor antagonists bicuculline (15 microM), SR-95531 (10 microM) and picrotoxinin (100 microM) while responses to glycine were selectively blocked by strychnine (200 nM), indicating the presence of two separate receptor types. 6. In outside-out membrane patches, GABA opened channels with conductances of 16 and 28 pS. The proportion of openings to each of the conductances varied between patches, possibly indicating the activation of two distinct channel types. Glycine-activated single-channel currents had conductances of 32, 55 and 104 pS. Single-channel I-V relationships were linear. 7. Spontaneous synaptic currents with a rapid rise time and biexponential decay were present in more than half of the cells examined. These currents were eliminated by bicuculline (15 microM) or SR-95331 (10 microM) and were greatly reduced in frequency by tetrodotoxin (TTX; 300 nM), suggesting that they were mediated by GABA and arose from spontaneous activity in Golgi interneurones. In granule cells where this spontaneous synaptic activity was apparent, glycine and low concentrations of GABA increased the frequency of the synaptic currents.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- M Kaneda
- Department of Pharmacology, University College London, UK
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45
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Abstract
In the cerebellum, NMDA (N-methyl-D-aspartate) receptors play an important role in neuronal differentiation and excitatory synaptic transmission. During early cerebellar development, marked changes occur in the distribution of messenger RNAs encoding various NMDA-receptor subunits. To determine whether these changes result in the appearance of functionally distinct NMDA receptors, we have recorded single-channel currents in rat cerebellar granule cells during the period of their migration from the external germinal layer to the inner granular layer. Here we show that before synapse formation, pre-migratory and migrating granule cells express NMDA receptors possessing single-channel properties similar to those previously described for many central neurons. In contrast, mature post-migratory cells also express an atypical form of NMDA receptor that has a lower single-channel conductance and distinct kinetic behaviour. The properties of these 'low-conductance' channels correspond to those described for recombinant NMDA receptors formed by coexpression of NR1 and NR2C subunits. The NR2C subunit appears postnatally and is found predominantly in the adult cerebellum. Our data demonstrate developmental changes in NMDA-receptor properties at the single-channel level, and suggest that in the cerebellum the expression of a specific subunit protein results in a distinct form of native receptor.
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Affiliation(s)
- M Farrant
- Department of Pharmacology, University College London, UK
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Perren T, Farrant M, McCarthy K, Harper P, Wiltshaw E. Lymphomas of the cervix and upper vagina: a report of five cases and a review of the literature. Gynecol Oncol 1992; 44:87-95. [PMID: 1730432 DOI: 10.1016/0090-8258(92)90018-e] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Five cases of non-Hodgkin's lymphoma of the cervix or upper vagina presenting over the last 20 years are described. The international literature has been reviewed for similar cases and a further 72 found. In 37 of these cases the pathology had been described according to one of the modern lymphoma classifications and details of clinical presentation, staging, treatment, and outcome were adequately described. The management and outcome of these patients have been critically reviewed and recommendations for the management of patients presenting with this disease have been made.
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Affiliation(s)
- T Perren
- Gynaecology Unit, Royal Marsden Hospital, London, United Kingdom
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49
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Abstract
Six jaundiced patients with primary sclerosing cholangitis and a dominant biliary stricture were managed by endoscopic placement of endoprostheses. Five showed considerable improvement within weeks of stenting: their serum bilirubin concentration fell from mean (range) 266 mumol/l (63-681) to 65 mumol/l (10-280) after one month. One patient required a liver transplant at five months because of continued deterioration in hepatic function. Follow up of 12-49 months in the remaining five patients shows sustained biochemical improvement, with repeat cholangiograms indicating doubling of the minimum calibre of the extrahepatic bile duct in four patients and considerable shortening of stricture length in three. Three patients developed sepsis at the time of the initial endoprosthesis insertion: surgical drainage was necessary in one. Endoscopic methods of improving biliary-enteric drainage in jaundiced patients with primary sclerosing cholangitis may be preferable to surgical and percutaneous methods, which may complicate subsequent liver transplantation.
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Affiliation(s)
- M Lombard
- Liver Unit, King's College Hospital, London
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50
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Abstract
Glutamate receptors of the N-methyl-D-aspartate (NMDA) and non-NMDA type serve different functions during excitatory synaptic transmission. Although many central neurons bear both types of receptor, the evidence concerning the sensitivity of cerebellar Purkinje cells to NMDA is contradictory. To investigate the receptor types present in Purkinje cells, we have used whole-cell and outside-out patch-clamp methods to record from cells in thin cerebellar slices from young rats. At a holding potential of -70 mV (in nominally Mg(2+)-free medium, with added glycine) NMDA caused a whole-cell current response which consisted of a dramatic increase in the frequency of synaptic currents. In the presence of tetrodotoxin (TTX) and the gamma-aminobutyric acidA (GABAA) receptor antagonist bicuculline, spontaneous synaptic currents and responses to NMDA were inhibited. In a proportion of cells a small polysynaptic response to NMDA persisted, which was further reduced by the non-NMDA receptor antagonist 6-cyano-2,3-dihydro-7-nitroquinoxalinedione (CNQX). The non-NMDA glutamate receptor agonists kainate (KA), quisqualate (QA) and s-alpha-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (s-AMPA), evoked large inward currents due to the direct activation of receptors in Purkinje cells. NMDA applied to excised membrane patches failed to evoke any single-channel currents, whereas s-AMPA and QA caused small inward currents accompanied by marked increases in current noise. Spectral analysis of the s-AMPA noise in patches gave an estimated mean channel conductance of approximately 4 pS.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Farrant
- Department of Pharmacology, University College London, U.K
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