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mGluR1 signaling in cerebellar Purkinje cells: Subcellular organization and involvement in cerebellar function and disease. Neuropharmacology 2021; 194:108629. [PMID: 34089728 DOI: 10.1016/j.neuropharm.2021.108629] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 05/19/2021] [Accepted: 05/20/2021] [Indexed: 11/20/2022]
Abstract
The cerebellum is essential for the control, coordination, and learning of movements, and for certain aspects of cognitive function. Purkinje cells are the sole output neurons in the cerebellar cortex and therefore play crucial roles in the diverse functions of the cerebellum. The type 1 metabotropic glutamate receptor (mGluR1) is prominently enriched in Purkinje cells and triggers downstream signaling pathways that are required for functional and structural plasticity, and for synaptic responses. To understand how mGluR1 contributes to cerebellar functions, it is important to consider not only the operational properties of this receptor, but also its spatial organization and the molecular interactions that enable its proper functioning. In this review, we highlight how mGluR1 and its related signaling molecules are organized into tightly coupled microdomains to fulfill physiological functions. We also describe emerging evidence that altered mGluR1 signaling in Purkinje cells underlies cerebellar dysfunction in ataxias of human patients and mouse models.
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Sun L, Li X, Guan H, Chen S, Fan X, Zhou C, Yang H, Xiao W. A Novel Role of A 2AR in the Maintenance of Intestinal Barrier Function of Enteric Glia from Hypoxia-Induced Injury by Combining with mGluR5. Front Pharmacol 2021; 12:633403. [PMID: 34093180 PMCID: PMC8173626 DOI: 10.3389/fphar.2021.633403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/25/2021] [Indexed: 12/20/2022] Open
Abstract
During acute intestinal ischemia reperfusion (IR) injury, the intestinal epithelial barrier (IEB) function is often disrupted. Enteric glial cells (EGCs) play an important role in maintaining the integrity of IEB functions. However, how EGCs regulate IEB function under IR stimulation is unknown. The present study reveals that the adenosine A2A receptor (A2AR) is important for mediating the barrier-modulating roles of EGCs. A2AR knockout (KO) experiments revealed more serious intestinal injury in A2AR KO mice than in WT mice after IR stimulation. Moreover, A2AR expression was significantly increased in WT mice when challenged by IR. To further investigate the role of A2AR in IEB, we established an in vitro EGC-Caco-2 co-culture system. Hypoxia stimulation was used to mimic the process of in vivo IR. Treating EGCs with the CGS21680 A2AR agonist attenuated hypoxia-induced intestinal epithelium damage through up-regulating ZO-1 and occludin expression in cocultured Caco-2 monolayers. Furthermore, we showed that A2AR and metabotropic glutamate receptor 5 (mGluR5) combine to activate the PKCα-dependent pathway in conditions of hypoxia. This study shows, for the first time, that hypoxia induces A2AR-mGluR5 interaction in EGCs to protect IEB function via the PKCα pathway.
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Affiliation(s)
- Lihua Sun
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Xiang Li
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Haidi Guan
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Shuaishuai Chen
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Xin Fan
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Chao Zhou
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Hua Yang
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Weidong Xiao
- Department of General Surgery, Xinqiao Hospital, Army Medical University, Chongqing, China
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Wang Y, Han J, Chen X, Zeng X, Wang Y, Dong J, Chen J. Maternal iodine supplementation improves motor coordination in offspring by modulating the mGluR1 signaling pathway in mild iodine deficiency-induced hypothyroxinemia rats. J Nutr Biochem 2018; 58:80-89. [DOI: 10.1016/j.jnutbio.2018.04.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 04/17/2018] [Accepted: 04/22/2018] [Indexed: 02/02/2023]
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Ca 2+ signaling and spinocerebellar ataxia. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1733-1744. [PMID: 29777722 DOI: 10.1016/j.bbamcr.2018.05.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/07/2018] [Accepted: 05/09/2018] [Indexed: 11/22/2022]
Abstract
Spinocerebellar ataxia (SCA) is a neural disorder, which is caused by degenerative changes in the cerebellum. SCA is primarily characterized by gait ataxia, and additional clinical features include nystagmus, dysarthria, tremors and cerebellar atrophy. Forty-four hereditary SCAs have been identified to date, along with >35 SCA-associated genes. Despite the great diversity and distinct functionalities of the SCA-related genes, accumulating evidence supports the occurrence of a common pathophysiological event among several hereditary SCAs. Altered calcium (Ca2+) homeostasis in the Purkinje cells (PCs) of the cerebellum has been proposed as a possible pathological SCA trigger. In support of this, signaling events that are initiated from or lead to aberrant Ca2+ release from the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1), which is highly expressed in cerebellar PCs, seem to be closely associated with the pathogenesis of several SCA types. In this review, we summarize the current research on pathological hereditary SCA events, which involve altered Ca2+ homeostasis in PCs, through IP3R1 signaling.
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Roome CJ, Empson RM. Survival strategies for mouse cerebellar Purkinje neurons lacking PMCA2. Neurosci Lett 2018; 663:25-28. [PMID: 29452612 DOI: 10.1016/j.neulet.2017.09.045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 09/23/2017] [Indexed: 11/25/2022]
Abstract
Expression of the fast calcium extrusion protein, PMCA2, in the cerebellum is amongst the highest found throughout the central nervous system, and unsurprisingly PMCA2 knockout mice exhibit cerebellar ataxia or loss of controlled movement. The sole output neurons of the cerebellar cortex, Purkinje neurons, are functionally compromised in these knockout mice, yet remarkably these neurons survive. In this mini-review we review and speculate on the importance of multiple PMCA2 dependent actions at cellular and synaptic sites within the cerebellar Purkinje neuron network. We also explore how loss of PMCA2-/- can lead to the ataxic phenotype, but can paradoxically also minimise calcium rises in cerebellar Purkinje neurons, thereby ensuring their resilience and survival.
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Affiliation(s)
- Christopher J Roome
- Optical Neuroimaging Unit, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan.
| | - Ruth M Empson
- Department of Physiology, School of Biomedical Sciences, Brain Health Research Centre, Brain Research New Zealand, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
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Watson LM, Bamber E, Schnekenberg RP, Williams J, Bettencourt C, Lickiss J, Jayawant S, Fawcett K, Clokie S, Wallis Y, Clouston P, Sims D, Houlden H, Becker EB, Németh AH. Dominant Mutations in GRM1 Cause Spinocerebellar Ataxia Type 44. Am J Hum Genet 2017; 101:451-458. [PMID: 28886343 PMCID: PMC5591020 DOI: 10.1016/j.ajhg.2017.08.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 07/25/2017] [Indexed: 12/15/2022] Open
Abstract
The metabotropic glutamate receptor 1 (mGluR1) is abundantly expressed in the mammalian central nervous system, where it regulates intracellular calcium homeostasis in response to excitatory signaling. Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a dominant-negative effect that is associated with juvenile-onset ataxia and intellectual disability. Crucially, the gain-of-function mutations could be pharmacologically modulated in vitro using an existing FDA-approved drug, Nitazoxanide, suggesting a possible avenue for treatment, which is currently unavailable for ataxias.
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Meera P, Pulst S, Otis T. A positive feedback loop linking enhanced mGluR function and basal calcium in spinocerebellar ataxia type 2. eLife 2017; 6. [PMID: 28518055 PMCID: PMC5444899 DOI: 10.7554/elife.26377] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 05/16/2017] [Indexed: 12/11/2022] Open
Abstract
Metabotropic glutamate receptor 1 (mGluR1) function in Purkinje neurons (PNs) is essential for cerebellar development and for motor learning and altered mGluR1 signaling causes ataxia. Downstream of mGluR1, dysregulation of calcium homeostasis has been hypothesized as a key pathological event in genetic forms of ataxia but the underlying mechanisms remain unclear. We find in a spinocerebellar ataxia type 2 (SCA2) mouse model that calcium homeostasis in PNs is disturbed across a broad range of physiological conditions. At parallel fiber synapses, mGluR1-mediated excitatory postsynaptic currents (EPSCs) and associated calcium transients are increased and prolonged in SCA2 PNs. In SCA2 PNs, enhanced mGluR1 function is prevented by buffering [Ca2+] at normal resting levels while in wildtype PNs mGluR1 EPSCs are enhanced by elevated [Ca2+]. These findings demonstrate a deleterious positive feedback loop involving elevated intracellular calcium and enhanced mGluR1 function, a mechanism likely to contribute to PN dysfunction and loss in SCA2. DOI:http://dx.doi.org/10.7554/eLife.26377.001
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Affiliation(s)
- Pratap Meera
- Department of Neurobiology, Geffen School of Medicine, University of California, Los Angeles, United States
| | - Stefan Pulst
- Department of Neurology, University of Utah, Salt Lake, United States
| | - Thomas Otis
- Department of Neurobiology, Geffen School of Medicine, University of California, Los Angeles, United States.,Neuroscience, Ophthalmology, and Rare Diseases, Roche Pharmaceutical Research and Early Development, Basel, Switzerland
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Foster DJ, Conn PJ. Allosteric Modulation of GPCRs: New Insights and Potential Utility for Treatment of Schizophrenia and Other CNS Disorders. Neuron 2017; 94:431-446. [PMID: 28472649 PMCID: PMC5482176 DOI: 10.1016/j.neuron.2017.03.016] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/02/2017] [Accepted: 03/09/2017] [Indexed: 01/11/2023]
Abstract
G-protein-coupled receptors (GPCRs) play critical roles in regulating brain function. Recent advances have greatly expanded our understanding of these receptors as complex signaling machines that can adopt numerous conformations and modulate multiple downstream signaling pathways. While agonists and antagonists have traditionally been pursued to target GPCRs, allosteric modulators provide several mechanistic advantages, including the ability to distinguish between closely related receptor subtypes. Recently, the discovery of allosteric ligands that confer bias and modulate some, but not all, of a given receptor's downstream signaling pathways can provide pharmacological modulation of brain circuitry with remarkable precision. In addition, allosteric modulators with unprecedented specificity have been developed that can differentiate between subpopulations of a given receptor subtype based on the receptor's dimerization state. These advances are not only providing insight into the biological roles of specific receptor populations, but hold great promise for treating numerous CNS disorders.
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Affiliation(s)
- Daniel J Foster
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA
| | - P Jeffrey Conn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA.
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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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Affiliation(s)
- Visou Ady
- Department of Biology, McGill University, Montreal, H3G 0B1, Canada
| | - Alanna J Watt
- Department of Biology, McGill University, Montreal, H3G 0B1, Canada
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Pu-erh Tea Protects the Nervous System by Inhibiting the Expression of Metabotropic Glutamate Receptor 5. Mol Neurobiol 2016; 54:5286-5299. [PMID: 27578019 PMCID: PMC5533841 DOI: 10.1007/s12035-016-0064-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 08/17/2016] [Indexed: 12/31/2022]
Abstract
Glutamate is one of the major excitatory neurotransmitters of the CNS and is essential for numerous key neuronal functions. However, excess glutamate causes massive neuronal death and brain damage owing to excitotoxicity via the glutamate receptors. Metabotropic glutamate receptor 5 (mGluR5) is one of the glutamate receptors and represents a promising target for studying neuroprotective agents of potential application in neurodegenerative diseases. Pu-erh tea, a fermented tea, mainly produced in Yunnan province, China, has beneficial effects, including the accommodation of the CNS. In this study, pu-erh tea markedly decreased the transcription and translation of mGluR5 compared to those by black and green teas. Pu-erh tea also inhibited the expression of Homer, one of the synaptic scaffolding proteins binding to mGluR5. Pu-erh tea protected neural cells from necrosis via blocked Ca2+ influx and inhibited protein kinase C (PKC) activation induced by excess glutamate. Pu-erh tea relieved rat epilepsy induced by LiCl-pilocarpine in behavioural and physiological assays. Pu-erh tea also decreased the expression of mGluR5 in the hippocampus. These results show that the inhibition of mGluR5 plays a role in protecting neural cells from glutamate. The results also indicate that pu-erh tea contains biological compounds binding transcription factors and inhibiting the expression of mGluR5 and identify pu-erh tea as a novel natural neuroprotective agent.
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Forsythe ID. Editorial. J Physiol 2016; 594:4469-70. [DOI: 10.1113/jp272724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Ian D. Forsythe
- Department of Neuroscience, Psychology & Behaviour; University of Leicester; UK
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Mark MD, Schwitalla JC, Groemmke M, Herlitze S. Keeping Our Calcium in Balance to Maintain Our Balance. Biochem Biophys Res Commun 2016; 483:1040-1050. [PMID: 27392710 DOI: 10.1016/j.bbrc.2016.07.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 07/04/2016] [Indexed: 01/13/2023]
Abstract
Calcium is a key signaling molecule and ion involved in a variety of diverse processes in our central nervous system (CNS) which include gene expression, synaptic transmission and plasticity, neuronal excitability and cell maintenance. Proper control of calcium signaling is not only vital for neuronal physiology but also cell survival. Mutations in fundamental channels, transporters and second messenger proteins involved in orchestrating the balance of our calcium homeostasis can lead to severe neurodegenerative disorders, such as Spinocerebellar (SCA) and Episodic (EA) ataxias. Hereditary ataxias make up a remarkably diverse group of neurological disorders clinically characterized by gait ataxia, nystagmus, dysarthria, trunk and limb ataxia and often atrophy of the cerebellum. The largest family of hereditary ataxias is SCAs which consists of a growing family of 42 members. A relatively smaller family of 8 members compose the EAs. The gene mutations responsible for half of the EA members and over 35 of the SCA subtypes have been identified, and several have been found to be responsible for cerebellar atrophy, abnormal intracellular calcium levels, dysregulation of Purkinje cell pacemaking, altered cerebellar synaptic transmission and/or ataxia in mouse models. Although the genetic diversity and affected cellular pathways of hereditary ataxias are broad, one common theme amongst these genes is their effects on maintaining calcium balance in primarily the cerebellum. There is emerging evidence that the pathogenesis of hereditary ataxias may be caused by imbalances in intracellular calcium due to genetic mutations in calcium-mediating proteins. In this review we will discuss the current evidence supporting the role of deranged calcium as the culprit to neurodegenerative diseases with a primary focus on SCAs and EAs.
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Affiliation(s)
- Melanie D Mark
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
| | - Jan Claudius Schwitalla
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Michelle Groemmke
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Stefan Herlitze
- Department of Zoology and Neurobiology, ND7/31, Ruhr University Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
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