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Feldthouse MG, Vyleta NP, Smith SM. PLC regulates spontaneous glutamate release triggered by extracellular calcium and readily releasable pool size in neocortical neurons. Front Cell Neurosci 2023; 17:1193485. [PMID: 37260580 PMCID: PMC10228687 DOI: 10.3389/fncel.2023.1193485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 04/26/2023] [Indexed: 06/02/2023] Open
Abstract
Introduction Dynamic physiological changes in brain extracellular calcium ([Ca2+]o) occur when high levels of neuronal activity lead to substantial Ca2+ entry via ion channels reducing local [Ca2+]o. Perturbations of the extracellular microenvironment that increase [Ca2+]o are commonly used to study how [Ca2+] regulates neuronal activity. At excitatory synapses, the Ca2+-sensing receptor (CaSR) and other G-protein coupled receptors link [Ca2+]o and spontaneous glutamate release. Phospholipase C (PLC) is activated by G-proteins and is hypothesized to mediate this process. Methods Patch-clamping cultured neocortical neurons, we tested how spontaneous glutamate release was affected by [Ca2+]o and inhibition of PLC activity. We used hypertonic sucrose (HS) to evaluate the readily releasable pool (RRP) and test if it was affected by inhibition of PLC activity. Results Spontaneous glutamate release substantially increased with [Ca2+]o, and inhibition of PLC activity, with U73122, abolished this effect. PLC-β1 is an abundant isoform in the neocortex, however, [Ca2+]o-dependent spontaneous release was unchanged in PLC-β1 null mutants (PLC-β1-/-). U73122 completely suppressed this response in PLC-β1-/- neurons, indicating that this residual [Ca2+]o-sensitivity may be mediated by other PLC isoforms. The RRP size was substantially reduced after incubation in U73122, but not U73343. Phorbol esters increased RRP size after PLC inhibition. Discussion Together these data point to a strong role for PLC in mediating changes in spontaneous release elicited by [Ca2+]o and other extracellular cues, possibly by modifying the size of the RRP.
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Affiliation(s)
- Maya G. Feldthouse
- Section of Pulmonary and Critical Care Medicine and Research and Development, VA Portland Health Care System, Portland, OR, United States
| | - Nicholas P. Vyleta
- Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Stephen M. Smith
- Section of Pulmonary and Critical Care Medicine and Research and Development, VA Portland Health Care System, Portland, OR, United States
- Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University, Portland, OR, United States
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Plasticity of Signaling by Spinal Estrogen Receptor α, κ-Opioid Receptor, and Metabotropic Glutamate Receptors over the Rat Reproductive Cycle Regulates Spinal Endomorphin 2 Antinociception: Relevance of Endogenous-Biased Agonism. J Neurosci 2017; 37:11181-11191. [PMID: 29025923 DOI: 10.1523/jneurosci.1927-17.2017] [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: 07/06/2017] [Revised: 09/06/2017] [Accepted: 10/02/2017] [Indexed: 01/22/2023] Open
Abstract
We previously showed that intrathecal application of endomorphin 2 [EM2; the highly specific endogenous μ-opioid receptor (MOR) ligand] induces antinociception that varies with stage of the rat estrous cycle: minimal during diestrus and prominent during proestrus. Earlier studies, however, did not identify proestrus-activated signaling strategies that enable spinal EM2 antinociception. We now report that in female rats, increased spinal dynorphin release and κ-opioid receptor (KOR) signaling, as well as the emergence of glutamate-activated metabotropic glutamate receptor 1 (mGluR1) signaling, are critical to the transition from an EM2 nonresponsive state (during diestrus) to an analgesically responsive state (during proestrus). Differential signaling by mGluR1, depending on its activation by membrane estrogen receptor α (mERα; during diestrus) versus glutamate (during proestrus), concomitant with the ebb and flow of spinal dynorphin/KOR signaling, functions as a switch, preventing or promoting, respectively, spinal EM2 antinociception. Importantly, EM2 and glutamate-containing varicosities appose spinal neurons that express MOR along with mGluRs and mERα, suggesting that signaling mechanisms regulating analgesic effectiveness of intrathecally applied EM2 also pertain to endogenous EM2. Regulation of spinal EM2 antinociception by both the nature of the endogenous mGluR1 activator (i.e., endogenous biased agonism at mGluR1) and changes in spinal dynorphin/KOR signaling represent a novel mechanism for modulating analgesic responsiveness to endogenous EM2 (and perhaps other opioids). This points the way for developing noncanonical pharmacological approaches to pain management by harnessing endogenous opioids for pain relief.SIGNIFICANCE STATEMENT The current prescription opioid abuse epidemic underscores the urgency to develop alternative pharmacotherapies for managing pain. We find that the magnitude of spinal endomorphin 2 (EM2) antinociception not only varies with stage of reproductive cycle, but is also differentially regulated during diestrus and proestrus. This finding highlights the need for sex-specific and cycle-specific approaches to pain management. Additionally, our finding that spinal EM2 antinociception in female rats is regulated by both the ebb and flow of spinal dynorphin/κ-opioid receptor signaling over the estrous cycle, as well as the nature of the endogenous mGluR1 activator, could encourage noncanonical pharmacological approaches to pain management, such as harnessing endogenous opioids for pain relief.
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Kano M, Watanabe T. Type-1 metabotropic glutamate receptor signaling in cerebellar Purkinje cells in health and disease. F1000Res 2017; 6:416. [PMID: 28435670 PMCID: PMC5381626 DOI: 10.12688/f1000research.10485.1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/30/2017] [Indexed: 01/28/2023] Open
Abstract
The cerebellum is a brain structure involved in coordination, control, and learning of movements, as well as certain aspects of cognitive function. Purkinje cells are the sole output neurons from the cerebellar cortex and therefore play crucial roles in the overall function of the cerebellum. The type-1 metabotropic glutamate receptor (mGluR1) is a key “hub” molecule that is critically involved in the regulation of synaptic wiring, excitability, synaptic response, and synaptic plasticity of Purkinje cells. In this review, we aim to highlight how mGluR1 controls these events in Purkinje cells. We also describe emerging evidence that altered mGluR1 signaling in Purkinje cells underlies cerebellar dysfunctions in several clinically relevant mouse models of human ataxias.
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Affiliation(s)
- Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Takaki Watanabe
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
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Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca 2. Int J Mol Sci 2017; 18:ijms18030672. [PMID: 28335551 PMCID: PMC5372683 DOI: 10.3390/ijms18030672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 03/13/2017] [Accepted: 03/17/2017] [Indexed: 12/24/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) associated with the slow phase of the glutamatergic signaling pathway in neurons of the central nervous system have gained importance as drug targets for chronic neurodegenerative diseases. While extracellular Ca2+ was reported to exhibit direct activation and modulation via an allosteric site, the identification of those binding sites was challenged by weak binding. Herein, we review the discovery of extracellular Ca2+ in regulation of mGluRs, summarize the recent developments in probing Ca2+ binding and its co-regulation of the receptor based on structural and biochemical analysis, and discuss the molecular basis for Ca2+ to regulate various classes of drug action as well as its importance as an allosteric modulator in mGluRs.
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Hoxha E, Tempia F, Lippiello P, Miniaci MC. Modulation, Plasticity and Pathophysiology of the Parallel Fiber-Purkinje Cell Synapse. Front Synaptic Neurosci 2016; 8:35. [PMID: 27857688 PMCID: PMC5093118 DOI: 10.3389/fnsyn.2016.00035] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 10/19/2016] [Indexed: 12/24/2022] Open
Abstract
The parallel fiber-Purkinje cell (PF-PC) synapse represents the point of maximal signal divergence in the cerebellar cortex with an estimated number of about 60 billion synaptic contacts in the rat and 100,000 billions in humans. At the same time, the Purkinje cell dendritic tree is a site of remarkable convergence of more than 100,000 parallel fiber synapses. Parallel fiber activity generates fast postsynaptic currents via α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and slower signals, mediated by mGlu1 receptors, resulting in Purkinje cell depolarization accompanied by sharp calcium elevation within dendritic regions. Long-term depression (LTD) and long-term potentiation (LTP) have been widely described for the PF-PC synapse and have been proposed as mechanisms for motor learning. The mechanisms of induction for LTP and LTD involve different signaling mechanisms within the presynaptic terminal and/or at the postsynaptic site, promoting enduring modification in the neurotransmitter release and change in responsiveness to the neurotransmitter. The PF-PC synapse is finely modulated by several neurotransmitters, including serotonin, noradrenaline and acetylcholine. The ability of these neuromodulators to gate LTP and LTD at the PF-PC synapse could, at least in part, explain their effect on cerebellar-dependent learning and memory paradigms. Overall, these findings have important implications for understanding the cerebellar involvement in a series of pathological conditions, ranging from ataxia to autism. For example, PF-PC synapse dysfunctions have been identified in several murine models of spino-cerebellar ataxia (SCA) types 1, 3, 5 and 27. In some cases, the defect is specific for the AMPA receptor signaling (SCA27), while in others the mGlu1 pathway is affected (SCA1, 3, 5). Interestingly, the PF-PC synapse has been shown to be hyper-functional in a mutant mouse model of autism spectrum disorder, with a selective deletion of Pten in Purkinje cells. However, the full range of methodological approaches, that allowed the discovery of the physiological principles of PF-PC synapse function, has not yet been completely exploited to investigate the pathophysiological mechanisms of diseases involving the cerebellum. We, therefore, propose to extend the spectrum of experimental investigations to tackle this problem.
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Affiliation(s)
- Eriola Hoxha
- Neuroscience Institute Cavalieri Ottolenghi (NICO) and Department of Neuroscience, University of TorinoTorino, Italy
| | - Filippo Tempia
- Neuroscience Institute Cavalieri Ottolenghi (NICO) and Department of Neuroscience, University of TorinoTorino, Italy
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Nonobe Y, Yokoyama T, Kamikubo Y, Yoshida S, Hisajima N, Shinohara H, Shiraishi Y, Sakurai T, Tabata T. Application of surface plasmon resonance imaging to monitoring G protein-coupled receptor signaling and its modulation in a heterologous expression system. BMC Biotechnol 2016; 16:36. [PMID: 27068216 PMCID: PMC4828886 DOI: 10.1186/s12896-016-0266-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 04/07/2016] [Indexed: 01/30/2023] Open
Abstract
Background G protein-coupled receptors (GPCRs) are ubiquitous surface proteins mediating various biological responses and thus, important targets for therapeutic drugs. GPCRs individually produce their own signaling as well as modulate the signaling of other GPCRs. Real-time observation of GPCR signaling and modulation in living cells is key to molecular study of biological responses and pharmaceutical development. However, fluorescence imaging, the technique widely used for this purpose, requires a fluorescent dye which may inhibit biological responses or a fluorescent-tagged target protein created through time-consuming genetic manipulation. In this study, we applied two-dimensional surface plasmon resonance (SPR) imaging to monitoring the translocation of protein kinase C (PKC), a major GPCR-coupled signaling molecule in the widely used HEK293 cell lines and examined whether the signaling of, and, modulation between heterologously expressed GPCRs can be measured without fluorescent labeling. Results We cultured HEK293 cells on the gold-plated slide glass and evoked SPR at the interface between the cell’s plasma membrane and the gold surface with incident light. The translocation of activated native PKC to the plasma membrane is expected to alter the incident angle-SPR extent relation, and this could be detected as a change in the intensity of light reflection from the specimen illuminated at a fixed incident angle. Direct activation of PKC with 12-O-tetradecanoylphorbol-13-acetate increased the reflection intensity. This increase indeed reported PKC translocation because it was reduced by a pre-treatment with bisindolylmaleimide-1, a PKC inhibitor. We further applied this technique to a stable HEK293 cell line heterologously expressing the GPCRs type-1 metabotropic glutamate receptor (mGluR1) and adenosine A1 receptor (A1R). (RS)-3,5-dihydroxyphenylglycine, a mGluR1 agonist, increased the reflection intensity, and the PKC inhibitor reduced this increase. A pre-treatment with (R)-N6-phenylisopropyladenosine, an A1R-selective agonist suppressed mGluR1-mediated reflection increase. These results suggest that our technique can detect PKC translocation initiated by ligand binding to mGluR1 and its modulation by A1R. Conclusions SPR imaging turned out to be utilizable for monitoring GPCR-mediated PKC translocation and its modulation by a different GPCR in a heterologous expression system. This technique provides a powerful yet easy-to-use tool for molecular study of biological responses and pharmaceutical development.
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Affiliation(s)
- Yuki Nonobe
- Laboratory for Medical Information Sensing, Graduate School of Science and Engineering, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Tomoki Yokoyama
- Laboratory for Medical Information Sensing, Graduate School of Science and Engineering, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Yuji Kamikubo
- Department of Pharmacology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Sho Yoshida
- Laboratory for Medical Information Sensing, Graduate School of Science and Engineering, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Nozomi Hisajima
- Laboratory for Medical Information Sensing, Graduate School of Science and Engineering, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Hiroaki Shinohara
- Laboratory for Bioelectronics, Graduate School of Innovative Life Science, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Yuki Shiraishi
- Laboratory for Bioelectronics, Graduate School of Innovative Life Science, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan
| | - Takashi Sakurai
- Department of Pharmacology, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Toshihide Tabata
- Laboratory for Medical Information Sensing, Graduate School of Science and Engineering, University of Toyama, 3190 Gokufu, Toyama, Toyama, 930-8555, Japan.
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Tora AS, Rovira X, Dione I, Bertrand H, Brabet I, De Koninck Y, Doyon N, Pin J, Acher F, Goudet C. Allosteric modulation of metabotropic glutamate receptors by chloride ions. FASEB J 2015; 29:4174-88. [DOI: 10.1096/fj.14-269746] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/15/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Amélie S. Tora
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Xavier Rovira
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Ibrahima Dione
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | | | - Isabelle Brabet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Yves De Koninck
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Nicolas Doyon
- Centre de Recherche de l'Institut Universitaire en Santé Mentale du Québec and Université LavalQuébecCanada
| | - Jean‐Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
| | - Francine Acher
- Laboratoire de Chimie et Biochimie Pharmacologiques et ToxicologiquesCNRS, UMR 8601, Université Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Cyril Goudet
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université de MontpellierMontpellierFrance
- INSERM U1191MontpellierFrance
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Jiang JY, Nagaraju M, Meyer RC, Zhang L, Hamelberg D, Hall RA, Brown EM, Conn PJ, Yang JJ. Extracellular calcium modulates actions of orthosteric and allosteric ligands on metabotropic glutamate receptor 1α. J Biol Chem 2013; 289:1649-61. [PMID: 24280223 DOI: 10.1074/jbc.m113.507665] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Metabotropic glutamate receptor 1α (mGluR1α), a member of the family C G protein-coupled receptors, is emerging as a potential drug target for various disorders, including chronic neuronal degenerative diseases. In addition to being activated by glutamate, mGluR1α is also modulated by extracellular Ca(2+). However, the underlying mechanism is unknown. Moreover, it has long been challenging to develop receptor-specific agonists due to homologies within the mGluR family, and the Ca(2+)-binding site(s) on mGluR1α may provide an opportunity for receptor-selective targeting by therapeutics. In the present study, we show that our previously predicted Ca(2+)-binding site in the hinge region of mGluR1α is adjacent to the site where orthosteric agonists and antagonists bind on the extracellular domain of the receptor. Moreover, we found that extracellular Ca(2+) enhanced mGluR1α-mediated intracellular Ca(2+) responses evoked by the orthosteric agonist l-quisqualate. Conversely, extracellular Ca(2+) diminished the inhibitory effect of the mGluR1α orthosteric antagonist (S)-α-methyl-4-carboxyphenylglycine. In addition, selective positive (Ro 67-4853) and negative (7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester) allosteric modulators of mGluR1α potentiated and inhibited responses to extracellular Ca(2+), respectively, in a manner similar to their effects on the response of mGluR1α to glutamate. Mutations at residues predicted to be involved in Ca(2+) binding, including E325I, had significant effects on the modulation of responses to the orthosteric agonist l-quisqualate and the allosteric modulator Ro 67-4853 by extracellular Ca(2+). These studies reveal that binding of extracellular Ca(2+) to the predicted Ca(2+)-binding site in the extracellular domain of mGluR1α modulates not only glutamate-evoked signaling but also the actions of both orthosteric ligands and allosteric modulators on mGluR1α.
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Affiliation(s)
- Jason Y Jiang
- From the Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
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Jiang Y, Huang Y, Wong HC, Zhou Y, Wang X, Yang J, Hall RA, Brown EM, Yang JJ. Elucidation of a novel extracellular calcium-binding site on metabotropic glutamate receptor 1{alpha} (mGluR1{alpha}) that controls receptor activation. J Biol Chem 2010; 285:33463-33474. [PMID: 20705606 DOI: 10.1074/jbc.m110.147033] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Metabotropic glutamate receptor 1α (mGluR1α) exerts important effects on numerous neurological processes. Although mGluR1α is known to respond to extracellular Ca(2+) ([Ca(2+)](o)) and the crystal structures of the extracellular domains (ECDs) of several mGluRs have been determined, the calcium-binding site(s) and structural determinants of Ca(2+)-modulated signaling in the Glu receptor family remain elusive. Here, we identify a novel Ca(2+)-binding site in the mGluR1α ECD using a recently developed computational algorithm. This predicted site (comprising Asp-318, Glu-325, and Asp-322 and the carboxylate side chain of the receptor agonist, Glu) is situated in the hinge region in the ECD of mGluR1α adjacent to the reported Glu-binding site, with Asp-318 involved in both Glu and calcium binding. Mutagenesis studies indicated that binding of Glu and Ca(2+) to their distinct but partially overlapping binding sites synergistically modulated mGluR1α activation of intracellular Ca(2+) ([Ca(2+)](i)) signaling. Mutating the Glu-binding site completely abolished Glu signaling while leaving its Ca(2+)-sensing capability largely intact. Mutating the predicted Ca(2+)-binding residues abolished or significantly reduced the sensitivity of mGluR1α not only to [Ca(2+)](o) and [Gd(3+)](o) but also, in some cases, to Glu. The dual activation of mGluR1α by [Ca(2+)](o) and Glu has important implications for the activation of other mGluR subtypes and related receptors. It also opens up new avenues for developing allosteric modulators of mGluR function that target specific human diseases.
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Affiliation(s)
- Yusheng Jiang
- From the Department of Chemistry, Atlanta, Georgia 30303
| | - Yun Huang
- From the Department of Chemistry, Atlanta, Georgia 30303
| | | | - Yubin Zhou
- From the Department of Chemistry, Atlanta, Georgia 30303
| | - Xue Wang
- Department of Computer Science, Center for Drug Design and Advanced Biotechnology, Georgia State University, Atlanta, Georgia 30303
| | - Jun Yang
- Department of Toxicology, Hangzhou Normal University School of Public Health, Hangzhou, Zhejiang 310036, China
| | - Randy A Hall
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Edward M Brown
- Division of Endocrinology, Diabetes, and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Jenny J Yang
- From the Department of Chemistry, Atlanta, Georgia 30303.
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Khan MA, Conigrave AD. Mechanisms of multimodal sensing by extracellular Ca(2+)-sensing receptors: a domain-based survey of requirements for binding and signalling. Br J Pharmacol 2010; 159:1039-50. [PMID: 20136834 DOI: 10.1111/j.1476-5381.2009.00603.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In this article we consider the molecular basis of sensing and signalling by the extracellular calcium-sensing receptor. We consider the nature of its ligands and sensing modalities, the identities of its major protein domains and their roles in sensing, signalling and trafficking as well as the significance of receptor homo- and hetero-dimerization. Finally, we consider the current, incomplete, state of knowledge regarding the requirements for ligand-specific signalling.
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Fujita Y, Shimomura T, Hosoguchi M, Kano M, Fukurotani K, Tabata T. A new multiple-drug applicator with minimal drug cross-talk, leakage, and consumption. Neurosci Res 2010; 66:412-4. [PMID: 20060427 DOI: 10.1016/j.neures.2009.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 12/16/2009] [Accepted: 12/24/2009] [Indexed: 11/29/2022]
Abstract
The relative effects of multiple drugs give an important clue to dissect a neuronal mechanism and to seek for a candidate neurotherapeutical agent. Here we have devised a "flute" applicator which can deliver several drugs to a neural cell preparation. The applicator stands by, cleaning itself with bath perfusate and delivers drugs only during test applications. This minimizes drug cross-talk in and leakage from the applicator and drug consumption. Using the applicator, we successfully compared the relative effects of widely different doses of an agonist in single neurons. The flute applicator would be a useful tool for pharmacological analyses.
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Affiliation(s)
- Yosuke Fujita
- Laboratory for Neural Information Technology, Graduate School of Sciences and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
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GABAB Receptor-Mediated Modulation of Metabotropic Glutamate Signaling and Synaptic Plasticity in Central Neurons. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:149-73. [DOI: 10.1016/s1054-3589(10)58007-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Ferraguti F, Crepaldi L, Nicoletti F. Metabotropic glutamate 1 receptor: current concepts and perspectives. Pharmacol Rev 2009; 60:536-81. [PMID: 19112153 DOI: 10.1124/pr.108.000166] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Almost 25 years after the first report that glutamate can activate receptors coupled to heterotrimeric G-proteins, tremendous progress has been made in the field of metabotropic glutamate receptors. Now, eight members of this family of glutamate receptors, encoded by eight different genes that share distinctive structural features have been identified. The first cloned receptor, the metabotropic glutamate (mGlu) receptor mGlu1 has probably been the most extensively studied mGlu receptor, and in many respects it represents a prototypical subtype for this family of receptors. Its biochemical, anatomical, physiological, and pharmacological characteristics have been intensely investigated. Together with subtype 5, mGlu1 receptors constitute a subgroup of receptors that couple to phospholipase C and mobilize Ca(2+) from intracellular stores. Several alternatively spliced variants of mGlu1 receptors, which differ primarily in the length of their C-terminal domain and anatomical localization, have been reported. Use of a number of genetic approaches and the recent development of selective antagonists have provided a means for clarifying the role played by this receptor in a number of neuronal systems. In this article we discuss recent advancements in the pharmacology and concepts about the intracellular transduction and pathophysiological role of mGlu1 receptors and review earlier data in view of these novel findings. The impact that this new and better understanding of the specific role of these receptors may have on novel treatment strategies for a variety of neurological and psychiatric disorders is considered.
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Affiliation(s)
- Francesco Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Peter-Mayr Strasse 1a, Innsbruck A-6020, Austria.
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Kano M, Hashimoto K, Tabata T. Type-1 metabotropic glutamate receptor in cerebellar Purkinje cells: a key molecule responsible for long-term depression, endocannabinoid signalling and synapse elimination. Philos Trans R Soc Lond B Biol Sci 2008; 363:2173-86. [PMID: 18339599 DOI: 10.1098/rstb.2008.2270] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The cerebellum is a brain structure involved in the coordination, control and learning of movements, and elucidation of its function is an important issue. Japanese scholars have made seminal contributions in this field of neuroscience. Electrophysiological studies of the cerebellum have a long history in Japan since the pioneering works by Ito and Sasaki. Elucidation of the basic circuit diagram of the cerebellum in the 1960s was followed by the construction of cerebellar network theories and finding of their neural correlates in the 1970s. A theoretically predicted synaptic plasticity, long-term depression (LTD) at parallel fibre to Purkinje cell synapse, was demonstrated experimentally in 1982 by Ito and co-workers. Since then, Japanese neuroscientists from various disciplines participated in this field and have made major contributions to elucidate molecular mechanisms underlying LTD. An important pathway for LTD induction is type-1 metabotropic glutamate receptor (mGluR1) and its downstream signal transduction in Purkinje cells. Sugiyama and co-workers demonstrated the presence of mGluRs and Nakanishi and his pupils identified the molecular structures and functions of the mGluR family. Moreover, the authors contributed to the discovery and elucidation of several novel functions of mGluR1 in cerebellar Purkinje cells. mGluR1 turned out to be crucial for the release of endocannabinoid from Purkinje cells and the resultant retrograde suppression of transmitter release. It was also found that mGluR1 and its downstream signal transduction in Purkinje cells are indispensable for the elimination of redundant synapses during post-natal cerebellar development. This article overviews the seminal works by Japanese neuroscientists, focusing on mGluR1 signalling in cerebellar Purkinje cells.
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Affiliation(s)
- Masanobu Kano
- Department of Cellular Neuroscience, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
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15
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Tabata T, Kawakami D, Hashimoto K, Kassai H, Yoshida T, Hashimotodani Y, Fredholm BB, Sekino Y, Aiba A, Kano M. G protein-independent neuromodulatory action of adenosine on metabotropic glutamate signalling in mouse cerebellar Purkinje cells. J Physiol 2007; 581:693-708. [PMID: 17379632 PMCID: PMC2075187 DOI: 10.1113/jphysiol.2007.129866] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Adenosine receptors (ARs) are G protein-coupled receptors (GPCRs) mediating the neuromodulatory actions of adenosine that influence emotional, cognitive, motor, and other functions in the central nervous system (CNS). Previous studies show complex formation between ARs and metabotropic glutamate receptors (mGluRs) in heterologous systems and close colocalization of ARs and mGluRs in several central neurons. Here we explored the possibility of intimate functional interplay between G(i/o) protein-coupled A(1)-subtype AR (A1R) and type-1 mGluR (mGluR1) naturally occurring in cerebellar Purkinje cells. Using a perforated-patch voltage-clamp technique, we found that both synthetic and endogenous agonists for A1R induced continuous depression of a mGluR1-coupled inward current. A1R agonists also depressed mGluR1-coupled intracellular Ca(2+) mobilization monitored by fluorometry. A1R indeed mediated this depression because genetic depletion of A1R abolished it. Surprisingly, A1R agonist-induced depression persisted after blockade of G(i/o) protein. The depression appeared to involve neither the cAMP-protein kinase A cascade downstream of the alpha subunits of G(i/o) and G(s) proteins, nor cytoplasmic Ca(2+) that is suggested to be regulated by the beta-gamma subunit complex of G(i/o) protein. Moreover, A1R did not appear to affect G(q) protein which mediates the mGluR1-coupled responses. These findings suggest that A1R modulates mGluR1 signalling without the aid of the major G proteins. In this respect, the A1R-mediated depression of mGluR1 signalling shown here is clearly distinguished from the A1R-mediated neuronal responses described so far. These findings demonstrate a novel neuromodulatory action of adenosine in central neurons.
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Affiliation(s)
- Toshihide Tabata
- Department of Cellular Neuroscience, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
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16
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Valério P, Pereira MM, Goes AM, Leite MF. BG60S dissolution interferes with osteoblast calcium signals. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2007; 18:265-71. [PMID: 17323157 DOI: 10.1007/s10856-006-0688-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Accepted: 08/23/2006] [Indexed: 05/14/2023]
Abstract
We investigated the influence of extracellular calcium concentration, caused by the dissolution of a bioactive glass with 60% of silicon (BG60S), on intracellular calcium (Ca(i) (2 +)) signals and expression of inositol 1, 4, 5-triphosphate receptors (InsP(3)R) in primary culture of osteoblasts. We found that BG60S caused an increase in Ca(i) (2 +) signals in this cell type. Additionally, osteoblasts pre-incubated in the presence of BG60S showed an increase in Ca(i) (2 +) when cells were stimulated with vasopressin. On the other hand, a decrease in Ca(i) (2 +) signals were observed in osteoblasts pre-treated with BG60S and stimulated with KCl. We furher found that in osteoblasts, the type I InsP(3)R is preferentially distributed in the nucleus while the type II InsP(3)R in the cytoplasm. Preincubation of osteoblasts with BG60S altered the receptor expression level, increasing the type I InsP(3)R in the nucleus and decreasing type II InsP(3)R in the cytosol. Together, our results showed that in osteoblasts, BG60S increased Ca(i) (2 +)signals and altered Ca(i) (2 +) machinery.
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Affiliation(s)
- P Valério
- Department of Physiology and Biophysics, Federal University of Minas Gerais, Av Antonio Carlos 6627, Pampulha, ICB, Bloco A4, Belo Horizonte, MG, Brazil.
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17
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Galvan A, Kuwajima M, Smith Y. Glutamate and GABA receptors and transporters in the basal ganglia: what does their subsynaptic localization reveal about their function? Neuroscience 2006; 143:351-75. [PMID: 17059868 PMCID: PMC2039707 DOI: 10.1016/j.neuroscience.2006.09.019] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 09/10/2006] [Accepted: 09/13/2006] [Indexed: 01/29/2023]
Abstract
GABA and glutamate, the main transmitters in the basal ganglia, exert their effects through ionotropic and metabotropic receptors. The dynamic activation of these receptors in response to released neurotransmitter depends, among other factors, on their precise localization in relation to corresponding synapses. The use of high resolution quantitative electron microscope immunocytochemical techniques has provided in-depth description of the subcellular and subsynaptic localization of these receptors in the CNS. In this article, we review recent findings on the ultrastructural localization of GABA and glutamate receptors and transporters in monkey and rat basal ganglia, at synaptic, extrasynaptic and presynaptic sites. The anatomical evidence supports numerous potential locations for receptor-neurotransmitter interactions, and raises important questions regarding mechanisms of activation and function of synaptic versus extrasynaptic receptors in the basal ganglia.
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Affiliation(s)
- A Galvan
- Yerkes National Primate Research Center, Emory University, Atlanta, GA 30322, USA.
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18
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Tabata T, Kano M. GABA(B) receptor-mediated modulation of glutamate signaling in cerebellar Purkinje cells. THE CEREBELLUM 2006; 5:127-33. [PMID: 16818387 DOI: 10.1080/14734220600788911] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Since Purkinje cells are the sole output neurons of the cerebellar cortex, the postsynaptic integration of excitatory and inhibitory synaptic inputs in this cell type is a pivotal step for cerebellar motor information processing. In Purkinje cells, Gi/o protein-coupled B-type gamma-aminobutyric acid receptor (GABABR) is expressed at the annuli of the dendritic spines that are innervated by the glutamatergic terminals of parallel fibers. The subcellular localization of GABABR suggests the possibility of postsynaptic interplay between GABABR and glutamate signaling. It has recently been demonstrated that GABABR indeed modulates alpha amino-3-hydroxy-5-methyl-4-isoxalone propionate-type ionotropic glutamate receptor (AMPAR)-mediated and type-1 metabotropic glutamate receptor (mGluR1)-mediated signaling. Interestingly, GABABR exerts modulatory actions not only via the classical Gi/o protein-dependent signaling cascade but also via a Gi/o protein-independent interaction between GABABR and mGluR1. In this review, we compare the physiological nature, underlying mechanisms, and possible functional significance of these modulatory actions of GABABR.
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Affiliation(s)
- Toshihide Tabata
- Department of Cellular Neuroscience, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan
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19
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Kornau HC. GABAB receptors and synaptic modulation. Cell Tissue Res 2006; 326:517-33. [PMID: 16932937 DOI: 10.1007/s00441-006-0264-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2006] [Accepted: 05/31/2006] [Indexed: 12/18/2022]
Abstract
GABA(B) receptors modulate transmitter release and postsynaptic membrane potential at various types of central synapses. They function as heterodimers of two related seven-transmembrane domain receptor subunits. Trafficking, activation and signalling of GABA(B) receptors are regulated both by allosteric interactions between the subunits and by the binding of additional proteins. Recent studies have shed light on the roles of GABA(B) receptors in plasticity processes at excitatory synapses. This review summarizes our knowledge of the localization, structure and function of GABA(B) receptors in the central nervous system and their use as drug targets for neurological and psychiatric disorders.
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Affiliation(s)
- Hans-Christian Kornau
- Center for Molecular Neurobiology (ZMNH), University of Hamburg, Falkenried 94, 20251 Hamburg, Germany.
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20
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Hardingham NR, Bannister NJ, Read JCA, Fox KD, Hardingham GE, Jack JJB. Extracellular calcium regulates postsynaptic efficacy through group 1 metabotropic glutamate receptors. J Neurosci 2006; 26:6337-45. [PMID: 16763042 PMCID: PMC6675184 DOI: 10.1523/jneurosci.5128-05.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Bursts of synaptic transmission are known to induce transient depletion of Ca2+ within the synaptic cleft. Although Ca2+ depletion has been shown to lower presynaptic release probability, effects on the postsynaptic cell have not been reported. In this study, we show that physiologically relevant reductions in extracellular Ca2+ lead to a decrease in synaptic strength between synaptically coupled layer 2/3 cortical pyramidal neurons. Using quantal analysis and mEPSP analysis, we demonstrate that a lowered extracellular Ca2+ produces a reduction in the postsynaptic quantal size in addition to its known effect on release probability. An elevated Mg2+ level can prevent this reduction in postsynaptic efficacy at subphysiological Ca2+ levels. We show that the calcium-dependent effect on postsynaptic quantal size is mediated by group 1 metabotropic glutamate receptors, acting via CaMKII (Ca2+/calmodulin-dependent protein kinase II) and PKC. Therefore, physiologically relevant changes in extracellular Ca2+ can regulate information transfer at cortical synapses via both presynaptic and postsynaptic mechanisms.
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Affiliation(s)
- Neil R Hardingham
- The University Laboratory of Physiology, Oxford University, Oxford OX1 3PT, United Kingdom.
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21
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Kuang D, Hampson DR. Ion dependence of ligand binding to metabotropic glutamate receptors. Biochem Biophys Res Commun 2006; 345:1-6. [PMID: 16674916 DOI: 10.1016/j.bbrc.2006.04.064] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Accepted: 04/13/2006] [Indexed: 11/25/2022]
Abstract
The ionic requirements for ligand binding to metabotropic glutamate receptors were carried out on secreted truncated receptors containing only the extracellular ligand binding domains of the receptors. The influence of ions on agonist binding was examined in mGluR1, mGluR3, and mGluR4 representing Group I, II, and III metabotropic glutamate receptors, respectively. [(3)H]Quisqualic acid binding to mGluR1 required the presence of calcium (or magnesium) ions but not sodium or chloride ions while [(3)H]DCG-IV binding to mGluR3 was dependent upon both cations and anions. [(3)H]L-AP4 binding to mGluR4 required chloride ions but not monovalent or divalent cations. The EC(50) for chloride facilitation of L-AP4 binding to mGluR4 was 63mM; this value is approximately one-half of the normal resting extracellular chloride concentration. These results demonstrate that metabotropic glutamate receptor subtypes require different complements of ions for ligand binding and suggest that natural physiological fluctuations in synaptic ion concentrations may regulate receptor binding and activation.
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Affiliation(s)
- Donghui Kuang
- Department of Pharmaceutical Sciences and Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada
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22
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Tateyama M, Kubo Y. Dual signaling is differentially activated by different active states of the metabotropic glutamate receptor 1alpha. Proc Natl Acad Sci U S A 2006; 103:1124-8. [PMID: 16410359 PMCID: PMC1347971 DOI: 10.1073/pnas.0505925103] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Indexed: 11/18/2022] Open
Abstract
The metabotropic glutamate receptor 1alpha (mGluR1alpha) is crucial for some forms of synaptic plasticity, by inducing various cell responses via coupling to various types of G proteins. Upon glutamate binding, an active conformation, closed-open/active, of the extracellular domain is stabilized, which induces dimeric rearrangement in the intracellular domains, resulting in the initiation of downstream signals. We have confirmed that mGluR1alpha functionally interacts with both Gq and Gs pathways; a combination of fluorescent indicators showed that glutamate increased intracellular Ca(2+) and cAMP concentration ([Ca(2+)](i) and [cAMP](i)). By contrast, Gd(3+), a different type of ligand whose recognition site on mGluR1alpha is distinct from the glutamate site, increased only [Ca(2+)](i) and the concentration-activation curve was bell-shaped. FRET analysis revealed that a low concentration of Gd(3+) induced dimeric rearrangement of the intracellular domains of mGluR1alpha as does glutamate, whereas a high concentration of Gd(3+) reversed the FRET efficiency, which was consistent with a bell-shaped relationship between concentration and Gq activation. These results suggest that Gd(3+) induces an active and a sort of "inactivated" conformation in mGluR1alpha. The Gd(3+)-induced active state is considered to correspond to the closed-closed/active conformation, revealed by previous x-ray crystallographic studies. In conclusion, the glutamate-induced closed-open/active state coupled both to Gs and Gq proteins whereas the Gd(3+)-induced closed-closed/active conformation state preferred Gq to Gs, suggesting that mGluR1alpha serves not only as a simple on/off switch but also as a multiple signaling path regulator.
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MESH Headings
- Animals
- Binding Sites
- CHO Cells
- Cell Physiological Phenomena
- Cricetinae
- Crystallography, X-Ray
- Cyclic AMP/metabolism
- Dimerization
- Dose-Response Relationship, Drug
- Enzyme Activation
- Fluorescence Resonance Energy Transfer
- Glutamates/metabolism
- Glutamic Acid/chemistry
- Glutamic Acid/metabolism
- Image Processing, Computer-Assisted
- Ligands
- Microscopy, Fluorescence
- Models, Biological
- Models, Statistical
- Protein Binding
- Protein Conformation
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Glutamate
- Receptors, Metabotropic Glutamate/metabolism
- Sequence Analysis, DNA
- Signal Transduction
- Time Factors
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Affiliation(s)
- Michihiro Tateyama
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan.
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23
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McCarson KE, Duric V, Reisman SA, Winter M, Enna SJ. GABA(B) receptor function and subunit expression in the rat spinal cord as indicators of stress and the antinociceptive response to antidepressants. Brain Res 2005; 1068:109-17. [PMID: 16368079 DOI: 10.1016/j.brainres.2005.11.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Revised: 11/02/2005] [Accepted: 11/06/2005] [Indexed: 02/05/2023]
Abstract
Experiments were undertaken to examine whether once daily i.p. administration of either of two antidepressants used for the treatment of neuropathic pain, amitriptyline (10 mg/kg) and fluoxetine (5 mg/kg), to rats for 7 days modifies GABA(B) receptor function and subunit expression in the lumbar spinal cord. The results indicate that, as previously reported for desipramine, both amitriptyline and fluoxetine increase the pain threshold to a thermal stimulus, the expression of GABA(B(1)) subunits, and baclofen-stimulated [35S]GTPgammaS binding, a measure of GABA(B) receptor function. The effects of antidepressant administration on GABA(B(1b)) and GABA(B(2)) subunit expression in spinal cord are more variable than for GABA(B(1a)). It was also discovered that repeated daily exposure to a thermal stimulus or immobilization stress increases GABA(B(1a)) expression in the lumbar spinal cord, with no commensurate change in thermal pain threshold or GABA(B) receptor sensitivity. These results support a relationship between GABA(B) receptors and the action of antidepressants. The findings demonstrate that drug-induced increases in GABA(B) receptor function can occur independently of any change in GABA(B) receptor subunit expression and are consistent with the notion that GABA(B) receptor subunits have multiple functions, only one of which is dimerization to form GABA(B) receptors. The data also suggest that GABA(B) subunit gene expression may serve as a preclinical marker of antidepressant efficacy and of drug- or stress-induced modifications in central nervous system activity.
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Affiliation(s)
- Kenneth E McCarson
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
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24
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Kubo Y, Tateyama M. Towards a view of functioning dimeric metabotropic receptors. Curr Opin Neurobiol 2005; 15:289-95. [PMID: 15922585 DOI: 10.1016/j.conb.2005.05.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Accepted: 05/06/2005] [Indexed: 11/19/2022]
Abstract
X-ray crystallography was used to solve the atomic structure of the ligand binding domain of the metabotropic glutamate receptor type1 homo-dimer, making it possible to show the conformational change of this domain upon glutamate binding. Studies of dimeric metabotropic receptors thereafter have focused on the respective roles and interaction of the two subunits, on the activation mechanisms following the structural rearrangements of the ligand-binding domain, and on the functional significance of polyvalent cations, the binding of which was identified in the crystal. The direct interaction between the GABA(B) receptor and the metabotropic glutamate receptor (mGluR1) has also attracted attention. Recently, attention has focused on incorporating these structural features into a functional view of the receptors.
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Affiliation(s)
- Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Nishigoh-naka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan.
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25
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Huang J, Spier AD, Pickel VM. 5-HT3A receptor subunits in the rat medial nucleus of the solitary tract: subcellular distribution and relation to the serotonin transporter. Brain Res 2005; 1028:156-69. [PMID: 15527741 DOI: 10.1016/j.brainres.2004.09.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/08/2004] [Indexed: 10/26/2022]
Abstract
The 5-hydroxytryptamine 3 (5HT3) receptor is a serotonin-gated ion channel implicated in reflex regulation of autonomic functions within the nucleus of the solitary tract (NTS). To determine the relevant sites for 5-HT3 receptor mediated transmission in this region, we used electron microscopic immunocytochemistry to examine the subcellular distribution of the 5HT3 receptor subunit A (5HT3A) in relation to the serotonin transporter (SERT) in the intermediate medial NTS (mNTS) of rat brain. The 5HT3A immunolabeling was detected in many axonal as well as somatodendritic and glial profiles. The axonal profiles included small axons and axon terminals in which the 5HT3A immunoreactivity was localized to membranes of synaptic vesicles and extrasynaptic plasma membranes. In dendrites and glia, the 5HT3A immunoreactivity was located on the plasma membranes or in association with membranous cytoplasmic organelles. The dendritic plasmalemmal 5HT3A labeling was prominent within and near excitatory-type synapses from terminals including those that resemble vagal afferents. The 5HT3A-labeled glial processes apposed 5HT3A-immunoreactive axonal and dendritic profiles, some of which also contained SERT. Terminals containing 5-HT3A and/or SERT were among those providing synaptic input to 5HT3A-labeled dendrites. Thus, 5HT3A has a subcellular distribution consistent with the involvement of 5-HT3 receptors in modulation of both presynaptic release and postsynaptic responses of mNTS neurons, some of which are serotonergic. The results further suggest that the neuronal as well as glial 5HT3 receptors can be activated by release of serotonin from presynaptic terminals or by diffusion facilitated by SERT distribution at a distant from the synapse.
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Affiliation(s)
- Jie Huang
- Division of Neurobiology, Department of Neurology and Neuroscience, Weill Medical College of Cornell University, 411 East 69th Street, New York, NY 10021, USA
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26
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Tabata T, Araishi K, Hashimoto K, Hashimotodani Y, van der Putten H, Bettler B, Kano M. Ca2+ activity at GABAB receptors constitutively promotes metabotropic glutamate signaling in the absence of GABA. Proc Natl Acad Sci U S A 2004; 101:16952-7. [PMID: 15550547 PMCID: PMC529326 DOI: 10.1073/pnas.0405387101] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Type B gamma-aminobutyric acid receptor (GABABR) is a G protein-coupled receptor that regulates neurotransmitter release and neuronal excitability throughout the brain. In various neurons, GABABRs are concentrated at excitatory synapses. Although these receptors are assumed to respond to GABA spillover from neighboring inhibitory synapses, their function is not fully understood. Here we show a previously undescribed function of GABABR exerted independent of GABA. In cerebellar Purkinje cells, interaction of GABABR with extracellular Ca2+ (Ca(2+)o) leads to a constitutive increase in the glutamate sensitivity of metabotropic glutamate receptor 1 (mGluR1). mGluR1 sensitization is clearly mediated by GABABR because it is absent in GABABR1 subunit-knockout cells. However, the mGluR1 sensitization does not require G(i/o) proteins that mediate the GABABR's classical functions. Moreover, coimmunoprecipitation reveals complex formation between GABABR and mGluR1 in the cerebellum. These findings demonstrate that GABABR can act as Ca(2+)o-dependent cofactors to enhance neuronal metabotropic glutamate signaling.
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Affiliation(s)
- Toshihide Tabata
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan
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27
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Tabata T, Kano M. Calcium dependence of native metabotropic glutamate receptor signaling in central neurons. Mol Neurobiol 2004; 29:261-70. [PMID: 15181238 DOI: 10.1385/mn:29:3:261] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Accepted: 11/17/2003] [Indexed: 11/11/2022]
Abstract
Metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors that are distributed throughout the brain and play important roles in regulation of synaptic efficacy. Some studies report that mGluRs heterologously expressed in nonneuronal cells are sensitive not only to glutamate but also to extracellular Ca2+ (Ca2+o). We studied the Ca2+o-sensitivity of native mGluRs in mammalian central neurons. In cerebellar Purkinje cells that naturally express type-1 mGluR (mGluR1), physiological levels of Ca2+o (around 2 mM) activate mGluR1-mediated intracellular Ca2+ mobilization. The activation of the native mGluR1 response to Ca2+o appears to be slower than that to glutamate. Ca2+o (2 mM) also augments glutamate analog-evoked, native mGluR1-mediated inward cation current and intracellular Ca2+o mobilization. Detailed analysis of this effect suggests that Ca2+o modulates the glutamate responsiveness of native and heterologously expressed mGluR1s in different manners. These findings suggest that Ca2+o may enhance the basal level and glutamate responsiveness of neuronal mGluR signaling in vivo.
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Affiliation(s)
- Toshihide Tabata
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan.
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28
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Sato M, Tabata T, Hashimoto K, Nakamura K, Nakao K, Katsuki M, Kitano J, Moriyoshi K, Kano M, Nakanishi S. Altered agonist sensitivity and desensitization of neuronal mGluR1 responses in knock-in mice by a single amino acid substitution at the PKC phosphorylation site. Eur J Neurosci 2004; 20:947-55. [PMID: 15305863 DOI: 10.1111/j.1460-9568.2004.03552.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
mGluR1 and mGluR5 of the metabotropic glutamate receptor family are coupled to inositol trisphosphate-Ca2+ signal cascades and evoke distinct Ca2+ responses in neural cells and heterologously expressing cells. In heterologous cells, stimulation of recombinant mGluR1 evokes a single-peaked Ca2+ response whereas mGluR5 elicits an oscillatory Ca2+ response. The distinct Ca2+ responses are interchangeable by single amino substitution of aspartate for threonine at the corresponding position of the carboxy-terminal cytoplasmic regions of mGluR1 and mGluR5, respectively. In this investigation, we generated knock-in mice, termed mGluR1 D854T mice, in which aspartate of mGluR1 was replaced with threonine. We examined the effect of this D854T substitution on Ca2+ and current responses mediated by mGluR1 in cultured cerebellar Purkinje cells. Stimulation of mGluR1 D854T by a group 1 mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG) evoked, as in wild-type mGluR1, only single-peaked Ca2+ responses as measured by Ca2+ fluorometric analysis. We then examined mGluR1-induced inward currents carried by nonselective cation channels during whole-cell recordings from cultured Purkinje cells. The mGluR1 D854T mutation abolished the responsiveness of mGluR1 to low concentrations of DHPG (0.5-500 nM) and reduced its desensitization during prolonged agonist application. mGluR1 D854T homozygous mutants showed no apparent behavioural abnormality as analysed by motor movement tests. These results indicate that, although additional modulatory mechanisms seem to be required to produce oscillatory Ca2+ responses of mGluR1, the single amino acid substitution at position 854 of mGluR1 is capable of influencing the kinetics of neuronal mGluR1 responses, most probably through PKC-mediated phosphorylation.
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Affiliation(s)
- Masaaki Sato
- Department of Molecular and System Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
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29
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Abstract
Regulation of Ca2+ homeostasis in the extracellular space plays an important role in neuronal function. Several modeling studies and recent measurements have demonstrated that modest action potential or synaptic activity can result in a significant reduction in extracellular calcium ([Ca]o(2+)). Changes in [Ca]o(2+) can regulate intracellular signaling enzymes, such as Ca2+/calmodulin-dependent protein kinase II, and influence neuronal function at synaptic and nonsynaptic sites. The change in [Ca]o(2+) can affect several types of ion channels and neurotransmitter receptors and activate a Ca(2+)-sensitive receptor in neuronal membranes. Depletion of [Ca]o(2+) may function as an activity-dependent extracellular messenger that regulates nervous system function during development, learning, and disease.
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Affiliation(s)
- Jonathan E Cohen
- National Institutes of Health, National Institute for Child and Human Development, Section on Nervous System Development and Plasticity, Bethesda, MD 20892, USA
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30
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Kim SJ, Kim YS, Yuan JP, Petralia RS, Worley PF, Linden DJ. Activation of the TRPC1 cation channel by metabotropic glutamate receptor mGluR1. Nature 2003; 426:285-91. [PMID: 14614461 DOI: 10.1038/nature02162] [Citation(s) in RCA: 283] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2003] [Accepted: 10/30/2003] [Indexed: 11/08/2022]
Abstract
Group I metabotropic glutamate receptors (consisting of mGluR1 and mGluR5) are G-protein-coupled neurotransmitter receptors that are found in the perisynaptic region of the postsynaptic membrane. These receptors are not activated by single synaptic volleys but rather require bursts of activity. They are implicated in many forms of neural plasticity including hippocampal long-term potentiation and depression, cerebellar long-term depression, associative learning, and cocaine addiction. When activated, group I mGluRs engage two G-protein-dependent signalling mechanisms: stimulation of phospholipase C and activation of an unidentified, mixed-cation excitatory postsynaptic conductance (EPSC), displaying slow activation, in the plasma membrane. Here we report that the mGluR1-evoked slow EPSC is mediated by the TRPC1 cation channel. TRPC1 is expressed in perisynaptic regions of the cerebellar parallel fibre-Purkinje cell synapse and is physically associated with mGluR1. Manipulations that interfere with TRPC1 block the mGluR1-evoked slow EPSC in Purkinje cells; however, fast transmission mediated by AMPA-type glutamate receptors remains unaffected. Furthermore, co-expression of mGluR1 and TRPC1 in a heterologous system reconstituted a mGluR1-evoked conductance that closely resembles the slow EPSC in Purkinje cells.
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Affiliation(s)
- Sang Jeong Kim
- Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, Maryland 21205, USA
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Nishida M, Sugimoto K, Hara Y, Mori E, Morii T, Kurosaki T, Mori Y. Amplification of receptor signalling by Ca2+ entry-mediated translocation and activation of PLCgamma2 in B lymphocytes. EMBO J 2003; 22:4677-88. [PMID: 12970180 PMCID: PMC212724 DOI: 10.1093/emboj/cdg457] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Revised: 07/22/2003] [Accepted: 07/23/2003] [Indexed: 11/14/2022] Open
Abstract
In non-excitable cells, receptor-activated Ca2+ signalling comprises initial transient responses followed by a Ca2+ entry-dependent sustained and/or oscillatory phase. Here, we describe the molecular mechanism underlying the second phase linked to signal amplification. An in vivo inositol 1,4,5-trisphosphate (IP3) sensor revealed that in B lymphocytes, receptor-activated and store-operated Ca2+ entry greatly enhanced IP3 production, which terminated in phospholipase Cgamma2 (PLCgamma2)-deficient cells. Association between receptor-activated TRPC3 Ca2+ channels and PLCgamma2, which cooperate in potentiating Ca2+ responses, was demonstrated by co-immunoprecipitation. PLCgamma2-deficient cells displayed diminished Ca2+ entry-induced Ca2+ responses. However, this defect was canceled by suppressing IP3-induced Ca2+ release, implying that IP3 and IP3 receptors mediate the second Ca2+ phase. Furthermore, confocal visualization of PLCgamma2 mutants demonstrated that Ca2+ entry evoked a C2 domain-mediated PLCgamma2 translocation towards the plasma membrane in a lipase-independent manner to activate PLCgamma2. Strikingly, Ca2+ entry-activated PLCgamma2 maintained Ca2+ oscillation and extracellular signal-regulated kinase activation downstream of protein kinase C. We suggest that coupling of Ca2+ entry with PLCgamma2 translocation and activation controls the amplification and co-ordination of receptor signalling.
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Affiliation(s)
- Motohiro Nishida
- Division of Molecular and Cellular Physiology, Center for Integrative Bioscience, Okazaki National Research Institutes, Okazaki, Aichi 444-8585, Japan
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O'Malley KL, Jong YJI, Gonchar Y, Burkhalter A, Romano C. Activation of metabotropic glutamate receptor mGlu5 on nuclear membranes mediates intranuclear Ca2+ changes in heterologous cell types and neurons. J Biol Chem 2003; 278:28210-9. [PMID: 12736269 DOI: 10.1074/jbc.m300792200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nuclear Ca2+ plays a critical role in many cellular functions although its mode (s) of regulation is unclear. This study shows that the metabotropic glutamate receptor, mGlu5, mobilizes nuclear Ca2+ independent of cytosolic Ca2+ regulation. Immunocytochemical, ultrastructural, and subcellular fractionation techniques revealed that the metabotropic glutamate receptor, mGlu5, can be localized to nuclear membranes in heterologous cells as well as midbrain and cortical neurons. Nuclear mGlu5 receptors derived from HEK cells or cortical cell types bound [3H]quisqualate. When loaded with Oregon Green BAPTA, nuclei isolated from mGlu5-expressing HEK cells responded to the addition of glutamate with rapid, oscillatory [Ca2+] elevations that were blocked by antagonist or EGTA. In contrast, carbachol-activation of endogenous muscarinic receptors led to cytoplasmic but not nuclear Ca2+ responses. Similarly, activation of mGlu5 receptors expressed on neuronal nuclei led to sustained Ca2+ oscillatory responses. These results suggest mGlu5 may mediate intranuclear signaling pathways.
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Affiliation(s)
- Karen L O'Malley
- Department of Anatomy, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Fukudome Y, Tabata T, Miyoshi T, Haruki S, Araishi K, Sawada S, Kano M. Insulin-like growth factor-I as a promoting factor for cerebellar Purkinje cell development. Eur J Neurosci 2003; 17:2006-16. [PMID: 12786966 DOI: 10.1046/j.1460-9568.2003.02640.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the mammalian CNS, the peptide hormone insulin-like growth factor-I (IGF-I) is synthesized in a certain subset of neurons and, it has been suggested, serves as a local neurotrophic factor. A postnatal increase in the expression of IGF-I and the type-1 IGF receptors (IGFR1) in the cerebellar cortex and its related brain regions indicates that developing cerebellar Purkinje cells (PC) may be an important target of IGF-I. However, little is known about how IGF-I influences PC development. Here we addressed this question, using a reduced environment of cerebellar neuron culture derived from perinatal mice. IGF-I exogenously applied at a physiological concentration (10 nm) greatly promoted the dendritic growth and survival of the PCs. By contrast, IGF-I only slightly promoted the somatic growth and little affected the maturation of the electrophysiological excitability of the PCs. The closely related hormone insulin had weaker promoting effects than did IGF-I. IGF-I appeared to at least bind to IGFR1 and to up-regulate the signalling pathways involving the phosphoinositide 3-kinase (PI3-K), mitogen-activated protein kinase (MAPK), p38 kinase (p38K), and an unknown signalling molecule(s). These signalling pathways may be coupled to the individual aspects of PC development in different manners and this may explain the difference in effects of IGF-I among these aspects. These findings suggest that IGF-I serves as a promoting factor for PC development, particularly postnatal survival and dendritic growth.
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Affiliation(s)
- Yuko Fukudome
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan
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Lorez M, Humbel U, Pflimlin MC, Kew JNC. Group III metabotropic glutamate receptors as autoreceptors in the cerebellar cortex. Br J Pharmacol 2003; 138:614-25. [PMID: 12598415 PMCID: PMC1573705 DOI: 10.1038/sj.bjp.0705099] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Group III metabotropic glutamate receptors (mGluRs) of the subtype 4a are localized within presynaptic active zones of cerebellar parallel fibre (PF)-Purkinje cell (PC) synapses. In order to investigate the conditions necessary for group III mGluR autoreceptor-activation by synaptically released glutamate, we characterized the effects of selective agonists and antagonists on excitatory postsynaptic currents (EPSCs) evoked by several distinct PF stimulation patterns. 2. The group III mGluR-selective agonist L-AP4 depressed evoked EPSCs at PF-PC synapses in rat brain slices with an EC(50) of 2.4 microM and maximum inhibition of 80%. This L-AP4-induced depression was antagonized by the group III mGluR-selective antagonist MSOP with an estimated equilibrium dissaciation constant of 12.5 microM. 3. Paired-pulse or four-pulse PF stimulations did not activate presynaptic group III mGluRs as revealed by the lack of effect of 1 mM MSOP on relative test EPSC amplitudes with latencies of 250-500 ms. The potentiation of a test EPSC evoked 200-500 ms after a short tetanic burst (100 Hz for 60 ms), was also unchanged in the presence of MSOP. 4. Endogenous autoreceptor-activation was revealed only during prolonged stimulation trains (10 Hz for 4.4 s), where, in the presence of 1 mM MSOP, the EPSC amplitudes were enhanced by 15%. 5. These observations support an autoreceptor function of group III mGluRs and a role in short-term synaptic plasticity at PF synapses. However, the low to moderate activation levels observed, despite the close spatial relation with glutamate release sites, suggests that additional mechanisms regulate receptor activation.
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Affiliation(s)
- Matthias Lorez
- Pharma Division Pre-clinical Research, F Hoffmann-La Roche Ltd, CH-4002 Basel, Switzerland.
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