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Pampaloni NP, Plested AJR. Slow excitatory synaptic currents generated by AMPA receptors. J Physiol 2021; 600:217-232. [PMID: 34587649 DOI: 10.1113/jp280877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/01/2021] [Indexed: 12/28/2022] Open
Abstract
Decades of literature indicate that the AMPA-type glutamate receptor is among the fastest acting of all neurotransmitter receptors. These receptors are located at excitatory synapses, and conventional wisdom says that they activate in hundreds of microseconds, deactivate in milliseconds due to their low affinity for glutamate and also desensitize profoundly. These properties circumscribe AMPA receptor activation in both space and time. However, accumulating evidence shows that AMPA receptors can also activate with slow, indefatigable responses. They do so through interactions with auxiliary subunits that are able promote a switch to a high open probability, high-conductance 'superactive' mode. In this review, we show that any assumption that this phenomenon is limited to heterologous expression is false and rather that slow AMPA currents have been widely and repeatedly observed throughout the nervous system. Hallmarks of the superactive mode are a lack of desensitization, resistance to competitive antagonists and a current decay that outlives free glutamate by hundreds of milliseconds. Because the switch to the superactive mode is triggered by activation, AMPA receptors can generate accumulating 'pedestal' currents in response to repetitive stimulation, constituting a postsynaptic mechanism for short-term potentiation in the range 5-100 Hz. Further, slow AMPA currents span 'cognitive' time intervals in the 100 ms range (theta rhythms), of particular interest for hippocampal function, where slow AMPA currents are widely expressed in a synapse-specific manner. Here, we outline the implications that slow AMPA receptors have for excitatory synaptic transmission and computation in the nervous system.
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Affiliation(s)
- Niccolò P Pampaloni
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, Berlin, Germany
| | - Andrew J R Plested
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, Berlin, Germany
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2
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Gao XZ, Ma RH, Zhang ZX. miR-339 Promotes Hypoxia-Induced Neuronal Apoptosis and Impairs Cell Viability by Targeting FGF9/CACNG2 and Mediating MAPK Pathway in Ischemic Stroke. Front Neurol 2020; 11:436. [PMID: 32587563 PMCID: PMC7297914 DOI: 10.3389/fneur.2020.00436] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 04/23/2020] [Indexed: 12/20/2022] Open
Abstract
Ischemic stroke (IS) is a common cerebrovascular disease characterized by insufficient blood blow to the brain and the second leading cause of death as well as disability worldwide. Recent literatures have indicated that abnormal expression of miR-339 is closely related to IS. In this study, we attempted to assess the biological function of miR-339 and its underlying mechanism in IS. By accessing the GEO repository, the expression of miR-339, FGF9, and CACNG2 in middle cerebral artery occlusion (MCAO) and non-MCAO was evaluated. PC12 cells after oxygen-glucose deprivation/reoxygenation (OGD/R) treatment were prepared to mimic in vitro the IS model. The levels of miR-339, FGF9, CACNG2, and MAPK-related markers were quantitatively measured by qRT-PCR and Western blot. CCK-8 and flow cytometry analyses were performed to examine cell viability and apoptosis, respectively. IS-related potential pathways were identified using KEGG enrichment analysis and GO annotations. Bioinformatics analysis and dual-luciferase reporter assay were used to predict and verify the possible target of miR-339. Our results showed that miR-339 expression was significantly increased in MCAO and OGD/R-treated PC12 cells. Overexpression of miR-339 inhibited cell viability of PC12 cells subjected to OGD/R treatment. FGF9 and CACMG2 are direct targets of miR-339 and can reverse the aggressive effect of miR-339 on the proliferation and apoptosis of OGD/R-treated PC12 cells. Moreover, miR-339 mediated the activation of the MAPK pathway, which was inhibited by the FGF9/CACNG2 axis in PC12 cells treated by OGD/R stimulation. In summary, these findings suggested that miR-339 might act as a disruptive molecule to accelerate the IS progression via targeting the FGF9/CACNG2 axis and mediating the MAPK pathway.
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Affiliation(s)
- Xiao-Zeng Gao
- Department of Anesthesiology, North China University of Science and Technology, Tangshan, China
| | - Ru-Hua Ma
- Emergency Department, Rizhao Hospital of Traditional Chinese Medicine, Rizhao, China
| | - Zhao-Xia Zhang
- Department of Geriatrics, Shanxian Central Hospital, Heze, China
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Stenum-Berg C, Musgaard M, Chavez-Abiega S, Thisted CL, Barrella L, Biggin PC, Kristensen AS. Mutational Analysis and Modeling of Negative Allosteric Modulator Binding Sites in AMPA Receptors. Mol Pharmacol 2019; 96:835-850. [PMID: 31582576 DOI: 10.1124/mol.119.116871] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 10/01/2019] [Indexed: 12/16/2022] Open
Abstract
The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) constitute a subclass of the ionotropic glutamate receptor superfamily, which functions as glutamate-gated cation channels to mediate the majority of excitatory neurotransmission in the central nervous system. AMPARs are therapeutic targets in a range of brain disorders associated with abnormal glutamate hyperactivity. Multiple classes of AMPAR inhibitors have been developed during the past decades, including competitive antagonists, ion channel blockers, and negative allosteric modulators (NAMs). At present, the NAM is the only class of AMPAR ligands that have been developed into safe and useful drugs in humans in the form of perampanel (Fycompa), which was recently approved for treatment of epilepsy. Compared with the detailed understanding of other AMPAR ligand classes, surprisingly little information has been available regarding the molecular mechanism of perampanel and other classes of NAMs at AMPARs; including the location and structure of NAM binding pockets in the receptor complex. However, structures of the AMPAR GluA2 in complex with NAMs were recently reported that unambiguously identified the NAM binding sites. In parallel with this work, our aim with the present study was to identify specific residues involved in the formation of the NAM binding site for three prototypical AMPAR NAMs. Hence, we have performed a mutational analysis of the AMPAR region that links the four extracellular ligand-binding domains to the central ion channel in the transmembrane domain region. Furthermore, we perform computational ligand docking of the NAMs into structural models of the homomeric GluA2 receptor and optimize side chain conformations around the NAMs to model how NAMs bind in this specific site. The new insights provide potentially valuable input for structure-based drug design of new NAMs. SIGNIFICANCE STATEMENT: The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are glutamate-gated ion channels that mediate the majority of excitatory neurotransmission in the brain. Negative allosteric modulators of AMPA receptors are considered to have significant therapeutic potential in diseases linked to glutamate hyperactivity. The present work employs mutational analysis and molecular modeling of the binding site for prototypical NAMs to provide new molecular insight into how NAMs interact with the AMPA receptor, which is of potential use for future design of new types of NAMs.
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Affiliation(s)
- Charlotte Stenum-Berg
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Maria Musgaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Sergei Chavez-Abiega
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Christine L Thisted
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Lorenzo Barrella
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Philip C Biggin
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (C.S.-B., S.C.-A., C.L.T., L.B., A.S.K.); and Department of Biochemistry, University of Oxford, Oxford, United Kingdom (M.M., P.C.B.)
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Abstract
Chronic postmastectomy pain (PMP) imposes a major burden on the quality of life of the ever-increasing number of long-term survivors of breast cancer. An earlier report by Nissenbaum et al. claimed that particular polymorphisms in the gene CACNG2 are associated with the risk of developing chronic PMP after breast surgery (Nissenbaum J, Devor M, Seltzer Z, Gebauer M, Michaelis M, Tal M, Dorfman R, Abitbul-Yarkoni M, Lu Y, Elahipanah T, delCanho S, Minert A, Fried K, Persson AK, Shpigler H, Shabo E, Yakir B, Pisante A, Darvasi A. Susceptibility to chronic pain following nerve injury is genetically affected by CACNG2. Genome Res 2010;20:1180-90). This information is important because in principle, it can inform the surgical, radiological, and chemotherapeutic decision-making process in ways that could mitigate the increased risk of chronic pain. In this study, we revisited this claim by independently evaluating the proposed marker haplotype using 2 different patient cohorts recruited in different research settings. Meta-analysis of these new postmastectomy cohorts and the original cohort confirmed significant association of the CACNG2 haplotype with PMP. In addition, we tested whether the same markers would predict chronic postsurgical pain in men who underwent surgery for inguinal hernia repair, and whether there is significant genetic association with cutaneous thermal sensitivity in postmastectomy and postherniotomy patients. We found that the biomarker is selective because it did not predict pain after laparoscopic hernia repair and was not associated with pain sensitivity to experimentally applied noxious thermal stimuli. We conclude that the A-C-C haplotype at the 3 single-nucleotide polymorphisms (rs4820242, rs2284015, and rs2284017) in the CACNG2 gene is associated with increased risk of developing PMP. This information may advance current knowledge on pathophysiology of PMP and serve as a step forward in the prediction of clinical outcomes and personalized pain management.
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Lee MR, Gardinier KM, Gernert DL, Schober DA, Wright RA, Wang H, Qian Y, Witkin JM, Nisenbaum ES, Kato AS. Structural Determinants of the γ-8 TARP Dependent AMPA Receptor Antagonist. ACS Chem Neurosci 2017; 8:2631-2647. [PMID: 28825787 DOI: 10.1021/acschemneuro.7b00186] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The forebrain specific AMPA receptor antagonist, LY3130481/CERC-611, which selectively antagonizes the AMPA receptors associated with TARP γ-8, an auxiliary subunit enriched in the forebrain, has potent antiepileptic activities without motor side effects. We designated the compounds with such activities as γ-8 TARP dependent AMPA receptor antagonists (γ-8 TDAAs). In this work, we further investigated the mechanisms of action using a radiolabeled γ-8 TDAA and ternary structural modeling with mutational validations to characterize the LY3130481 binding to γ-8. The radioligand binding to the cells heterologously expressing GluA1 and/or γ-8 revealed that γ-8 TDAAs binds to γ-8 alone without AMPA receptors. Homology modeling of γ-8, based on the crystal structures of a distant TARP homologue, murine claudin 19, in conjunction with knowledge of two γ-8 residues previously identified as critical for the LY3130481 TARP-dependent selectivity provided the basis for a binding mode prediction. This allowed further rational mutational studies for characterization of the structural determinants in TARP γ-8 for LY3130481 activities, both thermodynamically as well as kinetically.
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Affiliation(s)
- Matthew R. Lee
- Lilly
Biotechnology Center, Eli Lilly and Company, 10300 Campus Point Dr. #200, San Diego, California 92121, United States
| | - Kevin M. Gardinier
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Douglas L. Gernert
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Douglas A. Schober
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Rebecca A. Wright
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - He Wang
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Yuewei Qian
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Jeffrey M. Witkin
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Eric S. Nisenbaum
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
| | - Akihiko S. Kato
- Neuroscience
Discovery, Lilly Research Laboratory, 355 E Merril St., Indianapolis, Indiana 46285, United States
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6
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Kato AS, Witkin JM. Auxiliary subunits of AMPA receptors: The discovery of a forebrain-selective antagonist, LY3130481/CERC-611. Biochem Pharmacol 2017; 147:191-200. [PMID: 28987594 DOI: 10.1016/j.bcp.2017.09.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 09/27/2017] [Indexed: 12/11/2022]
Abstract
Drugs originate from the discovery of compounds, natural or synthetic, that bind to proteins (receptors, enzymes, transporters, etc.), the interaction of which modulates biological cascades that have potential therapeutic benefit. Rational strategies for identifying novel drug therapies are typically based on knowledge of the structure of the target proteins and the design of new chemical entities that modulate these proteins in a beneficial manner. The present review discusses a novel approach to drug discovery based on the identification and characterization of auxiliary proteins, the transmembrane AMPA receptor regulatory proteins (TARPs) that are associated with AMPA receptors. Utilizing these auxiliary proteins in compound screening led to the discovery of the TARP-dependent-AMPA forebrain selective receptor antagonist (TDAA), LY3130481/CERC-611 that is currently in clinical development for epilepsy.
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Affiliation(s)
- Akihiko S Kato
- Neuroscience Discovery Research, Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN 46285-0510, United States.
| | - Jeffrey M Witkin
- Neuroscience Discovery Research, Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN 46285-0510, United States.
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7
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Forebrain-selective AMPA-receptor antagonism guided by TARP γ-8 as an antiepileptic mechanism. Nat Med 2016; 22:1496-1501. [DOI: 10.1038/nm.4221] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 09/30/2016] [Indexed: 12/12/2022]
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8
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Devi SPS, Howe JR, Auger C. Train stimulation of parallel fibre to Purkinje cell inputs reveals two populations of synaptic responses with different receptor signatures. J Physiol 2016; 594:3705-27. [PMID: 27094216 DOI: 10.1113/jp272415] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 04/15/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Purkinje cells of the cerebellum receive ∼180,000 parallel fibre synapses, which have often been viewed as a homogeneous synaptic population and studied using single action potentials. Many parallel fibre synapses might be silent, however, and granule cells in vivo fire in bursts. Here, we used trains of stimuli to study parallel fibre inputs to Purkinje cells in rat cerebellar slices. Analysis of train EPSCs revealed two synaptic components, phase 1 and 2. Phase 1 is initially large and saturates rapidly, whereas phase 2 is initially small and facilitates throughout the train. The two components have a heterogeneous distribution at dendritic sites and different pharmacological profiles. The differential sensitivity of phase 1 and phase 2 to inhibition by pentobarbital and NBQX mirrors the differential sensitivity of AMPA receptors associated with the transmembrane AMPA receptor regulatory protein, γ-2, gating in the low- and high-open probability modes, respectively. ABSTRACT Cerebellar granule cells fire in bursts, and their parallel fibre axons (PFs) form ∼180,000 excitatory synapses onto the dendritic tree of a Purkinje cell. As many as 85% of these synapses have been proposed to be silent, but most are labelled for AMPA receptors. Here, we studied PF to Purkinje cell synapses using trains of 100 Hz stimulation in rat cerebellar slices. The PF train EPSC consisted of two components that were present in variable proportions at different dendritic sites: one, with large initial EPSC amplitude, saturated after three stimuli and dominated the early phase of the train EPSC; and the other, with small initial amplitude, increased steadily throughout the train of 10 stimuli and dominated the late phase of the train EPSC. The two phases also displayed different pharmacological profiles. Phase 2 was less sensitive to inhibition by NBQX but more sensitive to block by pentobarbital than phase 1. Comparison of synaptic results with fast glutamate applications to recombinant receptors suggests that the high-open-probability gating mode of AMPA receptors containing the auxiliary subunit transmembrane AMPA receptor regulatory protein γ-2 makes a substantial contribution to phase 2. We argue that the two synaptic components arise from AMPA receptors with different functional signatures and synaptic distributions. Comparisons of voltage- and current-clamp responses obtained from the same Purkinje cells indicate that phase 1 of the EPSC arises from synapses ideally suited to transmit short bursts of action potentials, whereas phase 2 is likely to arise from low-release-probability or 'silent' synapses that are recruited during longer bursts.
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Affiliation(s)
| | - James R Howe
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, 06520-8066, USA
| | - Céline Auger
- Laboratoire de Physiologie cérébrale, UMR 8118, Université Paris Descartes, 45, rue des Saints Pères, 75006, Paris, France
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Maher MP, Wu N, Ravula S, Ameriks MK, Savall BM, Liu C, Lord B, Wyatt RM, Matta JA, Dugovic C, Yun S, Ver Donck L, Steckler T, Wickenden AD, Carruthers NI, Lovenberg TW. Discovery and Characterization of AMPA Receptor Modulators Selective for TARP- 8. ACTA ACUST UNITED AC 2016; 357:394-414. [DOI: 10.1124/jpet.115.231712] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/11/2016] [Indexed: 01/14/2023]
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10
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MacLean DM, Ramaswamy SS, Du M, Howe JR, Jayaraman V. Stargazin promotes closure of the AMPA receptor ligand-binding domain. ACTA ACUST UNITED AC 2015; 144:503-12. [PMID: 25422502 PMCID: PMC4242809 DOI: 10.1085/jgp.201411287] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Stargazin enhances closure of the AMPA receptor ligand-binding domain, thereby facilitating channel activation. Transmembrane AMPA receptor (AMPAR) regulatory proteins (TARPs) markedly enhance AMPAR function, altering ligand efficacy and receptor gating kinetics and thereby shaping the postsynaptic response. The structural mechanism underlying TARP effects on gating, however, is unknown. Here we find that the prototypical member of the TARP family, stargazin or γ-2, rescues gating deficits in AMPARs carrying mutations that destabilize the closed-cleft states of the ligand-binding domain (LBD), suggesting that stargazin reverses the effects of these mutations and likely stabilizes closed LBD states. Furthermore, stargazin promotes a more closed conformation of the LBD, as indicated by reduced accessibility to the large antagonist NBQX. Consistent with the functional studies, luminescence resonance energy transfer experiments directly demonstrate that the AMPAR LBD is on average more closed in the presence of stargazin, in both the apo and agonist-bound states. The additional cleft closure and/or stabilization of the more closed-cleft states of the LBD is expected to translate to higher agonist efficacy and could contribute to the structural mechanism for stargazin modulation of AMPAR function.
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Affiliation(s)
- David M MacLean
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
| | - Swarna S Ramaswamy
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
| | - Mei Du
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
| | - James R Howe
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06530
| | - Vasanthi Jayaraman
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
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Zwart R, Sher E, Ping X, Jin X, Sims JR, Chappell AS, Gleason SD, Hahn PJ, Gardinier K, Gernert DL, Hobbs J, Smith JL, Valli SN, Witkin JM. Perampanel, an antagonist of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, for the treatment of epilepsy: studies in human epileptic brain and nonepileptic brain and in rodent models. J Pharmacol Exp Ther 2014; 351:124-33. [PMID: 25027316 DOI: 10.1124/jpet.114.212779] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Perampanel [Fycompa, 2-(2-oxo-1-phenyl-5-pyridin-2-yl-1,2-dihydropyridin-3-yl)benzonitrile hydrate 4:3; Eisai Inc., Woodcliff Lake, NJ] is an AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor antagonist used as an adjunctive treatment of partial-onset seizures. We asked whether perampanel has AMPA receptor antagonist activity in both the cerebral cortex and hippocampus associated with antiepileptic efficacy and also in the cerebellum associated with motor side effects in rodent and human brains. We also asked whether epileptic or nonepileptic human cortex is similarly responsive to AMPA receptor antagonism by perampanel. In rodent models, perampanel decreased epileptic-like activity in multiple seizure models. However, doses of perampanel that had anticonvulsant effects were within the same range as those engendering motor side effects. Perampanel inhibited native rat and human AMPA receptors from the hippocampus as well as the cerebellum that were reconstituted into Xenopus oocytes. In addition, with the same technique, we found that perampanel inhibited AMPA receptors from hippocampal tissue that had been removed from a patient who underwent surgical resection for refractory epilepsy. Perampanel inhibited AMPA receptor-mediated ion currents from all the tissues investigated with similar potency (IC50 values ranging from 2.6 to 7.0 μM). Cortical slices from the left temporal lobe derived from the same patient were studied in a 60-microelectrode array. Large field potentials were evoked on at least 45 channels of the array, and 10 μM perampanel decreased their amplitude and firing rate. Perampanel also produced a 33% reduction in the branching parameter, demonstrating the effects of perampanel at the network level. These data suggest that perampanel blocks AMPA receptors globally across the brain to account for both its antiepileptic and side-effect profile in rodents and epileptic patients.
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Affiliation(s)
- R Zwart
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - E Sher
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - X Ping
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - X Jin
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - J R Sims
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - A S Chappell
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - S D Gleason
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - P J Hahn
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - K Gardinier
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - D L Gernert
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - J Hobbs
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - J L Smith
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - S N Valli
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
| | - J M Witkin
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana (J.R.S., A.S.C., S.D.G., P.J.H., K.G., D.L.G., S.N.V., J.M.W.); Lilly Research Laboratories, Eli Lilly and Company, Windlesham, Surrey, United Kingdom (R.Z., E.S.); and Indiana University/Purdue University, Riley Hospital, Indianapolis, Indiana (X.P., X.J., J.H., J.L.S.)
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12
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Zaccara G, Giovannelli F, Cincotta M, Iudice A. AMPA receptor inhibitors for the treatment of epilepsy: the role of perampanel. Expert Rev Neurother 2014; 13:647-55. [PMID: 23739002 DOI: 10.1586/ern.13.46] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the postsynaptic membrane are involved in fast excitatory signaling in the brain and their activation may lead to the firing of action potentials. Talampanel and perampanel were the first noncompetitive AMPA receptor antagonists to be tested as add-on drugs in patients with refractory partial seizures, and were found to be effective in improving seizure control. Due to an unfavorable kinetic and tolerability profile, talampanel clinical development in the field of epilepsy was discontinued early while perampanel has been recently approved in Europe and the USA as adjunctive therapy for adults with partial seizures with or without secondary generalization. The recommended perampanel starting dose is 2 mg/day once daily, which can be increased up to the recommended maintenance dose of 4-8 mg/day. Increments should be of 2 mg/day and based on clinical response and tolerability. Titration should be performed at 1-week intervals or at lower speed and a 12-mg daily dose should be considered after careful evaluation. To date, no serious and/or idiosyncratic adverse effects have been associated with this agent. Most frequently reported adverse effects are dizziness, ataxia, aggression, irritability, vertigo, somnolence, fatigue, headache and gait disturbance. Weight increase is the only non-neurological adverse effects associated with perampanel.
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Affiliation(s)
- Gaetano Zaccara
- Unit of Neurology, Department of Medicine, Florence Health Authority, Firenze, Italy.
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13
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Niciu MJ, Ionescu DF, Richards EM, Zarate CA. Glutamate and its receptors in the pathophysiology and treatment of major depressive disorder. J Neural Transm (Vienna) 2013; 121:907-24. [PMID: 24318540 DOI: 10.1007/s00702-013-1130-x] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 11/25/2013] [Indexed: 12/13/2022]
Abstract
Monoaminergic neurotransmitter (serotonin, norepinephrine and dopamine) mechanisms of disease dominated the research landscape in the pathophysiology and treatment of major depressive disorder (MDD) for more than 50 years and still dominate available treatment options. However, the sum of all brain neurons that use monoamines as their primary neurotransmitter is <20%. In addition, most patients treated with monoaminergic antidepressants are left with significant residual symptoms and psychosocial disability not to mention side effects, e.g., sexual dysfunction. In the past several decades, there has been greater focus on the major excitatory neurotransmitter in the human brain, glutamate, in the pathophysiology and treatment of MDD. Although several preclinical and human magnetic resonance spectroscopy studies had already implicated glutamatergic abnormalities in the human brain, it was rocketed by the discovery that the N-methyl-D-aspartate receptor antagonist ketamine has rapid and potent antidepressant effects in even the most treatment-resistant MDD patients, including those who failed to respond to electroconvulsive therapy and who have active suicidal ideation. In this review, we will first provide a brief introduction to glutamate and its receptors in the mammalian brain. We will then review the clinical evidence for glutamatergic dysfunction in MDD, the discovery and progress-to-date with ketamine as a rapidly acting antidepressant, and other glutamate receptor modulators (including proprietary medications) for treatment-resistant depression. We will finally conclude by offering potential future directions necessary to realize the enormous therapeutic promise of glutamatergic antidepressants.
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Affiliation(s)
- Mark J Niciu
- Experimental Therapeutics and Pathophysiology Branch, Intramural Research Program, Department of Health and Human Services, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, Building 10/CRC, Room 7-5545, Bethesda, MD, 20892, USA,
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14
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Rogawski MA. AMPA receptors as a molecular target in epilepsy therapy. Acta Neurol Scand 2013:9-18. [PMID: 23480151 DOI: 10.1111/ane.12099] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2013] [Indexed: 11/28/2022]
Abstract
Epileptic seizures occur as a result of episodic abnormal synchronous discharges in cerebral neuronal networks. Although a variety of non-conventional mechanisms may play a role in epileptic synchronization, cascading excitation within networks of synaptically connected excitatory glutamatergic neurons is a classical mechanism. As is the case throughout the central nervous system, fast synaptic excitation within and between brain regions relevant to epilepsy is mediated predominantly by AMPA receptors. By inhibiting glutamate-mediated excitation, AMPA receptor antagonists markedly reduce or abolish epileptiform activity in in vitro preparations and confer seizure protection in a broad range of animal seizure models. NMDA receptors may also contribute to epileptiform activity, but NMDA receptor blockade is not sufficient to eliminate epileptiform discharges. AMPA receptors move into and out of the synapse in a dynamic fashion in forms of synaptic plasticity, underlying learning and memory. Often, the trigger for these dynamic movements is the activation of NMDA receptors. While NMDA receptor antagonists inhibit these forms of synaptic plasticity, AMPA receptor antagonists do not impair synaptic plasticity and do not inhibit memory formation or retrieval. The demonstrated clinical efficacy of perampanel, a high-potency, orally active non-competitive AMPA receptor antagonist, supports the concept that AMPA receptors are critical to epileptic synchronization and the generation and spread of epileptic discharges in human epilepsy.
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Affiliation(s)
- M. A. Rogawski
- Department of Neurology; School of Medicine and Center for Neuroscience; University of California, Davis; Sacramento; CA; USA
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15
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Semenov A, Möykkynen T, Coleman SK, Korpi ER, Keinänen K. Autoinactivation of the stargazin-AMPA receptor complex: subunit-dependency and independence from physical dissociation. PLoS One 2012; 7:e49282. [PMID: 23166629 PMCID: PMC3498123 DOI: 10.1371/journal.pone.0049282] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 10/08/2012] [Indexed: 11/18/2022] Open
Abstract
Agonist responses and channel kinetics of native α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors are modulated by transmembrane accessory proteins. Stargazin, the prototypical accessory protein, decreases desensitization and increases agonist potency at AMPA receptors. Furthermore, in the presence of stargazin, the steady-state responses of AMPA receptors show a gradual decline at higher glutamate concentrations. This "autoinactivation" has been assigned to physical dissociation of the stargazin-AMPA receptor complex and suggested to serve as a protective mechanism against overactivation. Here, we analyzed autoinactivation of GluA1-A4 AMPA receptors (all flip isoform) expressed in the presence of stargazin. Homomeric GluA1, GluA3, and GluA4 channels showed pronounced autoinactivation indicated by the bell-shaped steady-state dose response curves for glutamate. In contrast, homomeric GluA2i channels did not show significant autoinactivation. The resistance of GluA2 to autoinactivation showed striking dependence on the splice form as GluA2-flop receptors displayed clear autoinactivation. Interestingly, the resistance of GluA2-flip containing receptors to autoinactivation was transferred onto heteromeric receptors in a dominant fashion. To examine the relationship of autoinactivation to physical separation of stargazin from the AMPA receptor, we analyzed a GluA4-stargazin fusion protein. Notably, the covalently linked complex and separately expressed proteins expressed a similar level of autoinactivation. We conclude that autoinactivation is a subunit and splice form dependent property of AMPA receptor-stargazin complexes, which involves structural rearrangements within the complex rather than any physical dissociation.
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Affiliation(s)
- Artur Semenov
- Department of Biosciences, Division of Biochemistry and Biotechnology, University of Helsinki, Helsinki, Finland
| | - Tommi Möykkynen
- Department of Biosciences, Division of Biochemistry and Biotechnology, University of Helsinki, Helsinki, Finland
- Institute of Biomedicine, Pharmacology, University of Helsinki, Helsinki, Finland
| | - Sarah K. Coleman
- Department of Biosciences, Division of Biochemistry and Biotechnology, University of Helsinki, Helsinki, Finland
| | - Esa R. Korpi
- Institute of Biomedicine, Pharmacology, University of Helsinki, Helsinki, Finland
| | - Kari Keinänen
- Department of Biosciences, Division of Biochemistry and Biotechnology, University of Helsinki, Helsinki, Finland
- * E-mail:
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16
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Penn A, Balik A, Wozny C, Cais O, Greger I. Activity-mediated AMPA receptor remodeling, driven by alternative splicing in the ligand-binding domain. Neuron 2012; 76:503-10. [PMID: 23141062 PMCID: PMC3500689 DOI: 10.1016/j.neuron.2012.08.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/03/2012] [Indexed: 02/01/2023]
Abstract
The AMPA-type glutamate receptor (AMPAR) subunit composition shapes synaptic transmission and varies throughout development and in response to different input patterns. Here, we show that chronic activity deprivation gives rise to synaptic AMPAR responses with enhanced fidelity. Extrasynaptic AMPARs exhibited changes in kinetics and pharmacology associated with splicing of the alternative flip/flop exons. AMPAR mRNA indeed exhibited reprogramming of the flip/flop exons for GluA1 and GluA2 subunits in response to activity, selectively in the CA1 subfield. However, the functional changes did not directly correlate with the mRNA expression profiles but result from altered assembly of GluA1/GluA2 subunit splice variants, uncovering an additional regulatory role for flip/flop splicing in excitatory signaling. Our results suggest that activity-dependent AMPAR remodeling underlies changes in short-term synaptic plasticity and provides a mechanism for neuronal homeostasis.
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Affiliation(s)
- Andrew C. Penn
- Neurobiology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Ales Balik
- Neurobiology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Christian Wozny
- Neurobiology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Ondrej Cais
- Neurobiology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Ingo H. Greger
- Neurobiology Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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17
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Ahmed AH, Hamada M, Shinada T, Ohfune Y, Weerasinghe L, Garner PP, Oswald RE. The structure of (-)-kaitocephalin bound to the ligand binding domain of the (S)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/glutamate receptor, GluA2. J Biol Chem 2012; 287:41007-13. [PMID: 23076153 DOI: 10.1074/jbc.m112.416362] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glutamate receptors mediate the majority of excitatory synaptic transmission in the central nervous system, and excessive stimulation of these receptors is involved in a variety of neurological disorders and neuronal damage from stroke. The development of new subtype-specific antagonists would be of considerable therapeutic interest. Natural products can provide important new lead compounds for drug discovery. The only natural product known to inhibit glutamate receptors competitively is (-)-kaitocephalin, which was isolated from the fungus Eupenicillium shearii and found to protect CNS neurons from excitotoxicity. Previous work has shown that it is a potent antagonist of some subtypes of glutamate receptors (AMPA and NMDA, but not kainate). The structure of kaitocephalin bound to the ligand binding domain of the AMPA receptor subtype, GluA2, is reported here. The structure suggests how kaitocephalin can be used as a scaffold to develop more selective and high affinity antagonists for glutamate receptors.
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Affiliation(s)
- Ahmed H Ahmed
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, USA
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18
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Jackson AC, Nicoll RA. Stargazing from a new vantage--TARP modulation of AMPA receptor pharmacology. J Physiol 2012; 589:5909-10. [PMID: 22174138 DOI: 10.1113/jphysiol.2011.223495] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Alexander C Jackson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143, USA.
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19
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Alkorta I, Elguero J, Roussel C, Vanthuyne N, Piras P. Atropisomerism and Axial Chirality in Heteroaromatic Compounds. ADVANCES IN HETEROCYCLIC CHEMISTRY 2012. [DOI: 10.1016/b978-0-12-396530-1.00001-2] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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20
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Abstract
An estimated 15-50% of the population experiences pain at any given time, at great personal and societal cost. Pain is the most common reason patients seek medical attention, and there is a high degree of individual variability in reporting the incidence and severity of symptoms. Research suggests that pain sensitivity and risk for chronic pain are complex heritable traits of polygenic origin. Animal studies and candidate gene testing in humans have provided some progress in understanding the heritability of pain, but the application of the genome-wide association methodology offers a new tool for further elucidating the genetic contributions to normal pain responding and pain in clinical populations. Although the determination of the genetics of pain is still in its infancy, it is clear that a number of genes play a critical role in determining pain sensitivity or susceptibility to chronic pain. This review presents an update of the most recent findings that associate genetic variation with variability in pain and an overview of the candidate genes with the highest translational potential.
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Affiliation(s)
- Erin E Young
- Department of Anesthesiology, Molecular Epidemiology of Pain Program, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA
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21
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Ahmed AH, Wang S, Chuang HH, Oswald RE. Mechanism of AMPA receptor activation by partial agonists: disulfide trapping of closed lobe conformations. J Biol Chem 2011; 286:35257-66. [PMID: 21846932 PMCID: PMC3186401 DOI: 10.1074/jbc.m111.269001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 07/08/2011] [Indexed: 11/06/2022] Open
Abstract
The mechanism by which agonist binding to an ionotropic glutamate receptor leads to channel opening is a central issue in molecular neurobiology. Partial agonists are useful tools for studying the activation mechanism because they produce full channel activation with lower probability than full agonists. Structural transitions that determine the efficacy of partial agonists can provide information on the trigger that begins the channel-opening process. The ligand-binding domain of AMPA receptors is a bilobed structure, and the closure of the lobes is associated with channel activation. One possibility is that partial agonists sterically block full lobe closure but that partial degrees of closure trigger the channel with a lower probability. Alternatively, full lobe closure may be required for activation, and the stability of the fully closed state could determine efficacy with the fully closed state having a lower stability when bound to partial relative to full agonists. Disulfide-trapping experiments demonstrated that even extremely low efficacy ligands such as 6-cyano-7-nitroquinoxaline-2,3-dione can produce a full lobe closure, presumably with low probability. The results are consistent the hypothesis that the efficacy is determined at least in part by the stability of the state in which the lobes are fully closed.
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Affiliation(s)
| | - Shu Wang
- Biomedical Sciences, Cornell University, Ithaca, New York 14853
| | - Huai-Hu Chuang
- Biomedical Sciences, Cornell University, Ithaca, New York 14853
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22
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Maclean DM, Bowie D. Transmembrane AMPA receptor regulatory protein regulation of competitive antagonism: a problem of interpretation. J Physiol 2011; 589:5383-90. [PMID: 21969453 DOI: 10.1113/jphysiol.2011.219485] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Synaptic AMPA receptors are greatly influenced by a family of transmembrane AMPA receptor regulatory proteins (TARPs) which control trafficking, channel gating and pharmacology. The prototypical TARP, stargazin (or γ2), shifts the blocking ability of several AMPAR-selective compounds including the commonly used quinoxalinedione antagonists, CNQX and NBQX. Stargazin's effect on CNQX is particularly intriguing as it not only apparently lowers the potency of block, as with NBQX, but also renders it a partial agonist. Given this, agonist behaviour by CNQX has been speculated to account for its weaker blocking effect on AMPAR-TARP complexes. Here we show that this is not the case. The apparent effect of stargazin on CNQX antagonism can be almost entirely explained by an increase in the apparent affinity for l-glutamate (l-Glu), a full agonist and neurotransmitter at AMPAR synapses. Partial agonism at best plays a minor role but not through channel gating per se but rather because CNQX elicits AMPAR desensitization. Our study reveals that CNQX is best thought of as a non-competitive antagonist at glutamatergic synapses due to the predominance of non-equilibrium conditions. Consequently, CNQX primarily reports the proportion of AMPARs available for activation but may also impose additional block by receptor desensitization.
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Affiliation(s)
- David M Maclean
- Department of Pharmacology & Therapeutics, McGill University, Montreal, Québec, Canada H3G 0B1
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23
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Abstract
In the 1990s there was intense interest in ionotropic glutamate receptors as therapeutic targets for diverse neurological disorders, including epilepsy. NMDA receptors were thought to play a key role in the generation of seizures, leading to clinical studies of NMDA receptor blocking drugs in epilepsy. Disappointing results dampened enthusiasm for ionotropic glutamate receptors as a therapeutic target. Eventually it became appreciated that another type of ionotropic glutamate receptor, the AMPA receptor, is actually the predominant mediator of excitatory neurotransmission in the central nervous system and moreover that AMPA receptors are critical to the generation and spread of epileptic activity. As drugs became available that selectively target AMPA receptors, it was possible to demonstrate that AMPA receptor antagonists have powerful antiseizure activity in in vitro and in vivo models. A decade later, promising clinical studies with AMPA receptor antagonists, including the potent noncompetitive antagonist perampanel, are once again focusing attention on AMPA receptors as a drug target for epilepsy therapy.
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24
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Jackson AC, Nicoll RA. The expanding social network of ionotropic glutamate receptors: TARPs and other transmembrane auxiliary subunits. Neuron 2011; 70:178-99. [PMID: 21521608 DOI: 10.1016/j.neuron.2011.04.007] [Citation(s) in RCA: 288] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2011] [Indexed: 12/25/2022]
Abstract
Ionotropic glutamate receptors (iGluRs) underlie rapid, excitatory synaptic signaling throughout the CNS. After years of intense research, our picture of iGluRs has evolved from them being companionless in the postsynaptic membrane to them being the hub of dynamic supramolecular signaling complexes, interacting with an ever-expanding litany of other proteins that regulate their trafficking, scaffolding, stability, signaling, and turnover. In particular, the discovery that transmembrane AMPA receptor regulatory proteins (TARPs) are AMPA receptor auxiliary subunits that are critical determinants of their trafficking, gating, and pharmacology has changed the way we think about iGluR function. Recently, a number of novel transmembrane proteins have been uncovered that may also serve as iGluR auxiliary proteins. Here we review pivotal developments in our understanding of the role of TARPs in AMPA receptor trafficking and gating, and provide an overview of how newly discovered transmembrane proteins expand our view of iGluR function in the CNS.
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Affiliation(s)
- Alexander C Jackson
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94143, USA.
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25
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Schober DA, Gill MB, Yu H, Gernert DL, Jeffries MW, Ornstein PL, Kato AS, Felder CC, Bredt DS. Transmembrane AMPA receptor regulatory proteins and cornichon-2 allosterically regulate AMPA receptor antagonists and potentiators. J Biol Chem 2011; 286:13134-42. [PMID: 21343286 DOI: 10.1074/jbc.m110.212522] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AMPA receptors mediate fast excitatory transmission in the brain. Neuronal AMPA receptors comprise GluA pore-forming principal subunits and can associate with multiple modulatory components, including transmembrane AMPA receptor regulatory proteins (TARPs) and CNIHs (cornichons). AMPA receptor potentiators and non-competitive antagonists represent potential targets for a variety of neuropsychiatric disorders. Previous studies showed that the AMPA receptor antagonist GYKI-53655 displaces binding of a potentiator from brain receptors but not from recombinant GluA subunits. Here, we asked whether AMPA receptor modulatory subunits might resolve this discrepancy. We find that the cerebellar TARP, stargazin (γ-2), enhances the binding affinity of the AMPA receptor potentiator [(3)H]-LY450295 and confers sensitivity to displacement by non-competitive antagonists. In cerebellar membranes from stargazer mice, [(3)H]-LY450295 binding is reduced and relatively resistant to displacement by non-competitive antagonists. Coexpression of AMPA receptors with CNIH-2, which is expressed in the hippocampus and at low levels in the cerebellar Purkinje neurons, confers partial sensitivity of [(3)H]-LY450295 potentiator binding to displacement by non-competitive antagonists. Autoradiography of [(3)H]-LY450295 binding to stargazer and γ-8-deficient mouse brain sections, demonstrates that TARPs regulate the pharmacology of allosteric AMPA potentiators and antagonists in the cerebellum and hippocampus, respectively. These studies demonstrate that accessory proteins define AMPA receptor pharmacology by functionally linking allosteric AMPA receptor potentiator and antagonist sites.
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Affiliation(s)
- Douglas A Schober
- Discovery Neuroscience Research, Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, Indiana 46285, USA
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26
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Kato AS, Gill MB, Ho MT, Yu H, Tu Y, Siuda ER, Wang H, Qian YW, Nisenbaum ES, Tomita S, Bredt DS. Hippocampal AMPA receptor gating controlled by both TARP and cornichon proteins. Neuron 2011; 68:1082-96. [PMID: 21172611 DOI: 10.1016/j.neuron.2010.11.026] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2010] [Indexed: 11/17/2022]
Abstract
Transmembrane AMPA receptor regulatory proteins (TARPs) and cornichon proteins (CNIH-2/3) independently modulate AMPA receptor trafficking and gating. However, the potential for interactions of these subunits within an AMPA receptor complex is unknown. Here, we find that TARPs γ-4, γ-7, and γ-8, but not γ-2, γ-3, or γ-5, cause AMPA receptors to "resensitize" upon continued glutamate application. With γ-8, resensitization occurs with all GluA subunit combinations; however, γ-8-containing hippocampal neurons do not display resensitization. In recombinant systems, CNIH-2 abrogates γ-8-mediated resensitization and modifies AMPA receptor pharmacology and gating to match that of hippocampal neurons. In hippocampus, γ-8 and CNIH-2 associate in postsynaptic densities and CNIH-2 protein levels are markedly diminished in γ-8 knockout mice. Manipulating neuronal CNIH-2 levels modulates the electrophysiological properties of extrasynaptic and synaptic γ-8-containing AMPA receptors. Thus, γ-8 and CNIH-2 functionally interact with common hippocampal AMPA receptor complexes to modulate synergistically kinetics and pharmacology.
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Affiliation(s)
- Akihiko S Kato
- Department of Neuroscience, Eli Lilly and Company, Indianapolis, IN 46285, USA.
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27
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Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R. Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev 2010; 62:405-96. [PMID: 20716669 PMCID: PMC2964903 DOI: 10.1124/pr.109.002451] [Citation(s) in RCA: 2579] [Impact Index Per Article: 184.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.
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Affiliation(s)
- Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Rollins Research Center, 1510 Clifton Road, Atlanta, GA 30322-3090, USA.
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28
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Nissenbaum J, Devor M, Seltzer Z, Gebauer M, Michaelis M, Tal M, Dorfman R, Abitbul-Yarkoni M, Lu Y, Elahipanah T, delCanho S, Minert A, Fried K, Persson AK, Shpigler H, Shabo E, Yakir B, Pisanté A, Darvasi A. Susceptibility to chronic pain following nerve injury is genetically affected by CACNG2. Genome Res 2010; 20:1180-90. [PMID: 20688780 DOI: 10.1101/gr.104976.110] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Chronic neuropathic pain is affected by specifics of the precipitating neural pathology, psychosocial factors, and by genetic predisposition. Little is known about the identity of predisposing genes. Using an integrative approach, we discovered that CACNG2 significantly affects susceptibility to chronic pain following nerve injury. CACNG2 encodes for stargazin, a protein intimately involved in the trafficking of glutamatergic AMPA receptors. The protein might also be a Ca(2+) channel subunit. CACNG2 has previously been implicated in epilepsy. Initially, using two fine-mapping strategies in a mouse model (recombinant progeny testing [RPT] and recombinant inbred segregation test [RIST]), we mapped a pain-related quantitative trait locus (QTL) (Pain1) into a 4.2-Mb interval on chromosome 15. This interval includes 155 genes. Subsequently, bioinformatics and whole-genome microarray expression analysis were used to narrow the list of candidates and ultimately to pinpoint Cacng2 as a likely candidate. Analysis of stargazer mice, a Cacng2 hypomorphic mutant, provided electrophysiological and behavioral evidence for the gene's functional role in pain processing. Finally, we showed that human CACNG2 polymorphisms are associated with chronic pain in a cohort of cancer patients who underwent breast surgery. Our findings provide novel information on the genetic basis of neuropathic pain and new insights into pain physiology that may ultimately enable better treatments.
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Affiliation(s)
- Jonathan Nissenbaum
- Department of Genetics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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29
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Tomita S. Regulation of ionotropic glutamate receptors by their auxiliary subunits. Physiology (Bethesda) 2010; 25:41-9. [PMID: 20134027 DOI: 10.1152/physiol.00033.2009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glutamate receptors are major excitatory receptors in the brain. Recent findings have established auxiliary subunits of glutamate receptors as critical modulators of synaptic transmission, synaptic plasticity, and neurological disorder. The elucidation of the molecular rules governing glutamate receptors and subunits will improve our understanding of synapses and of neural-circuit regulation in the brain.
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Affiliation(s)
- Susumu Tomita
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA.
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30
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Kato AS, Gill MB, Yu H, Nisenbaum ES, Bredt DS. TARPs differentially decorate AMPA receptors to specify neuropharmacology. Trends Neurosci 2010; 33:241-8. [PMID: 20219255 DOI: 10.1016/j.tins.2010.02.004] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 02/11/2010] [Accepted: 02/13/2010] [Indexed: 11/30/2022]
Abstract
Transmembrane AMPA receptor regulatory proteins (TARPs) are the first identified auxiliary subunits for a neurotransmitter-gated ion channel. Although initial studies found that stargazin, the prototypical TARP, principally chaperones AMPA receptors, subsequent research demonstrated that it also regulates AMPA receptor kinetics and synaptic waveforms. Recent studies have identified a diverse collection of TARP isoforms--types Ia, Ib II--that distinctly regulate AMPA receptor trafficking, gating and neuropharmacology. These TARP isoforms are heterogeneously expressed in specific neuronal populations and can differentially sculpt synaptic transmission and plasticity. Whole-genome analyses also link multiple TARP loci to childhood epilepsy, schizophrenia and bipolar disorder. TARPs emerge as vital components of excitatory synapses that participate both in signal transduction and in neuropsychiatric disorders.
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Affiliation(s)
- Akihiko S Kato
- Department of Neuroscience, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285-0510, USA
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31
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Fleming JJ, England PM. Developing a complete pharmacology for AMPA receptors: a perspective on subtype-selective ligands. Bioorg Med Chem 2010; 18:1381-7. [PMID: 20096591 DOI: 10.1016/j.bmc.2009.12.072] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 12/19/2009] [Accepted: 12/31/2009] [Indexed: 01/15/2023]
Abstract
AMPA receptors are a family of ligand-gated ion channels that play central roles in rapid neural signaling and in regulation of synaptic strength. Additionally, these receptors are implicated in a number of major psychiatric and neurological diseases. A comprehensive understanding of the roles that AMPA receptors play in the mammalian nervous system has been hampered by the dearth of ligands available to select between individual AMPA receptors subtypes. Here we provide a perspective on opportunities for developing a complete pharmacology for AMPA receptors.
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Affiliation(s)
- James J Fleming
- Department of Pharmaceutical Chemistry and Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
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32
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Covington HE, Vialou V, Nestler EJ. From synapse to nucleus: novel targets for treating depression. Neuropharmacology 2009; 58:683-93. [PMID: 20018197 DOI: 10.1016/j.neuropharm.2009.12.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Accepted: 12/07/2009] [Indexed: 12/28/2022]
Abstract
The need for newer compounds to treat depression is an ever-growing concern due to the enormous societal and financial ramifications of this disorder. Here, we review some of the candidate systems that could potentially be involved in depression, or an inherent resistance to depression termed resilience, and the numerous protein targets for these systems. A substantial body of literature provides strong evidence that neurotrophic factors, glutamate receptors, hypothalamic feeding peptides, nuclear hormone receptors, and epigenetic mechanisms, among others, will make for interesting targets when examining depressive behavior or resilience in preclinical models, and eventually clinical trials. Although some of these targets for depression already appear promising, new waves of more selective compounds for any molecular system should promote a better understanding of this complex disease and perhaps improved treatments.
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Affiliation(s)
- Herbert E Covington
- Fishberg Department of Neuroscience, Mount Sinai School of Medicine, NY 10029, USA
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Sager C, Terhag J, Kott S, Hollmann M. C-terminal domains of transmembrane alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor regulatory proteins not only facilitate trafficking but are major modulators of AMPA receptor function. J Biol Chem 2009; 284:32413-24. [PMID: 19773551 DOI: 10.1074/jbc.m109.039891] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-type glutamate receptors are essential players in fast synaptic transmission in the vertebrate central nervous system. Their synaptic delivery and localization as well as their electrophysiological properties are regulated by transmembrane AMPA receptor regulatory proteins (TARPs). However, the exact mechanisms of how the four originally designated TARPs (gamma2, gamma3, gamma4, and gamma8) modulate AMPA receptor function remain largely unknown. Previous studies suggested the C-terminal domain (CTD) of gamma2 to mediate increased trafficking and reduced desensitization of AMPA receptors. As it remained unclear whether these findings extend to other TARPs, we set out to investigate and compare the role of the CTDs of the four original TARPs in AMPA receptor modulation. To address this issue, we replaced the TARP CTDs with the CTD of the homologous subunit gamma1, a voltage-dependent calcium channel subunit expressed in skeletal muscle that lacks TARP properties. We analyzed the impact of the resulting chimeras on GluR1 functional properties in Xenopus oocytes and HEK293 cells. Interestingly, the CTDs of all TARPs not only modulate the extent and kinetics of desensitization but also modulate agonist potencies of AMPA receptors. Furthermore, the CTDs are required for TARP-induced modulation of AMPA receptor gating, including conversion of antagonists to partial agonists and constitutive channel openings. Strikingly, we found a special role of the cytoplasmic tail of gamma4, suggesting that the underlying mechanisms of modulation of AMPA receptor function are different among the TARPs. We propose that the intracellularly located CTD is the origin of TARP-specific functional modulation and not merely a facilitator of trafficking.
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Affiliation(s)
- Charlotte Sager
- Department of Biochemistry I-Receptor Biochemistry, Ruhr University Bochum, Germany
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