1
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Membrane trafficking and positioning of mGluRs at presynaptic and postsynaptic sites of excitatory synapses. Neuropharmacology 2021; 200:108799. [PMID: 34592242 DOI: 10.1016/j.neuropharm.2021.108799] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 08/31/2021] [Accepted: 09/17/2021] [Indexed: 01/21/2023]
Abstract
The plethora of functions of glutamate in the brain are mediated by the complementary actions of ionotropic and metabotropic glutamate receptors (mGluRs). The ionotropic glutamate receptors carry most of the fast excitatory transmission, while mGluRs modulate transmission on longer timescales by triggering multiple intracellular signaling pathways. As such, mGluRs mediate critical aspects of synaptic transmission and plasticity. Interestingly, at synapses, mGluRs operate at both sides of the cleft, and thus bidirectionally exert the effects of glutamate. At postsynaptic sites, group I mGluRs act to modulate excitability and plasticity. At presynaptic sites, group II and III mGluRs act as auto-receptors, modulating release properties in an activity-dependent manner. Thus, synaptic mGluRs are essential signal integrators that functionally couple presynaptic and postsynaptic mechanisms of transmission and plasticity. Understanding how these receptors reach the membrane and are positioned relative to the presynaptic glutamate release site are therefore important aspects of synapse biology. In this review, we will discuss the currently known mechanisms underlying the trafficking and positioning of mGluRs at and around synapses, and how these mechanisms contribute to synaptic functioning. We will highlight outstanding questions and present an outlook on how recent technological developments will move this exciting research field forward.
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2
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Park D, Park S, Song J, Kang M, Lee S, Horak M, Suh YH. N‐linked glycosylation of the mGlu7 receptor regulates the forward trafficking and transsynaptic interaction with Elfn1. FASEB J 2020; 34:14977-14996. [DOI: 10.1096/fj.202001544r] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/14/2020] [Accepted: 08/27/2020] [Indexed: 01/13/2023]
Affiliation(s)
- Da‐ha Park
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
| | - Sunha Park
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
| | - Jae‐man Song
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
| | - Minji Kang
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
| | - Sanghyeon Lee
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
| | - Martin Horak
- Institute of Physiology of the Czech Academy of Sciences Institute of Experimental Medicine of the Czech Academy of Sciences Prague 4 Czech Republic
| | - Young Ho Suh
- Department of Biomedical Sciences Neuroscience Research Institute Transplantation Research Institute Seoul National University College of Medicine Seoul South Korea
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Nasrallah C, Rottier K, Marcellin R, Compan V, Font J, Llebaria A, Pin JP, Banères JL, Lebon G. Direct coupling of detergent purified human mGlu 5 receptor to the heterotrimeric G proteins Gq and Gs. Sci Rep 2018. [PMID: 29535347 PMCID: PMC5849714 DOI: 10.1038/s41598-018-22729-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The metabotropic glutamate (mGlu) receptors are class C G protein-coupled receptors (GPCRs) that modulate synaptic activity and plasticity throughout the mammalian brain. Signal transduction is initiated by glutamate binding to the venus flytrap domains (VFT), which initiates a conformational change that is transmitted to the conserved heptahelical domains (7TM) and results ultimately in the activation of intracellular G proteins. While both mGlu1 and mGlu5 activate Gαq G-proteins, they also increase intracellular cAMP concentration through an unknown mechanism. To study directly the G protein coupling properties of the human mGlu5 receptor homodimer, we purified the full-length receptor, which required careful optimisation of the expression, N-glycosylation and purification. We successfully purified functional mGlu5 that activated the heterotrimeric G protein Gq. The high-affinity agonist-PAM VU0424465 also activated the purified receptor in the absence of an orthosteric agonist. In addition, it was found that purified mGlu5 was capable of activating the G protein Gs either upon stimulation with VU0424465 or glutamate, although the later induced a much weaker response. Our findings provide important mechanistic insights into mGlu5 G protein-dependent activity and selectivity.
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Affiliation(s)
- Chady Nasrallah
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France
| | - Karine Rottier
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France
| | - Romain Marcellin
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France
| | - Vincent Compan
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France
| | - Joan Font
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
| | - Amadeu Llebaria
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France
| | - Jean-Louis Banères
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ. Montpellier, ENSCM, Montpellier, France
| | - Guillaume Lebon
- Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Montpellier, F-34000, Montpellier, France.
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Lv X, Liu J, Shi Q, Tan Q, Wu D, Skinner JJ, Walker AL, Zhao L, Gu X, Chen N, Xue L, Si P, Zhang L, Wang Z, Katritch V, Liu ZJ, Stevens RC. In vitro expression and analysis of the 826 human G protein-coupled receptors. Protein Cell 2016; 7:325-37. [PMID: 27085723 PMCID: PMC4853319 DOI: 10.1007/s13238-016-0263-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 03/09/2016] [Indexed: 01/24/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are involved in all human physiological systems where they are responsible for transducing extracellular signals into cells. GPCRs signal in response to a diverse array of stimuli including light, hormones, and lipids, where these signals affect downstream cascades to impact both health and disease states. Yet, despite their importance as therapeutic targets, detailed molecular structures of only 30 GPCRs have been determined to date. A key challenge to their structure determination is adequate protein expression. Here we report the quantification of protein expression in an insect cell expression system for all 826 human GPCRs using two different fusion constructs. Expression characteristics are analyzed in aggregate and among each of the five distinct subfamilies. These data can be used to identify trends related to GPCR expression between different fusion constructs and between different GPCR families, and to prioritize lead candidates for future structure determination feasibility.
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Affiliation(s)
- Xuechen Lv
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Junlin Liu
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Qiaoyun Shi
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Qiwen Tan
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Dong Wu
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - John J Skinner
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Angela L Walker
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, 90089, USA
| | - Lixia Zhao
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Xiangxiang Gu
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Na Chen
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Lu Xue
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Pei Si
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Lu Zhang
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Zeshi Wang
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
| | - Vsevolod Katritch
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, 90089, USA
| | - Zhi-Jie Liu
- iHuman Institute, ShanghaiTech University, Shanghai, 201210, China
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5
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Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors. Eur J Pharmacol 2015; 763:233-40. [PMID: 25981296 DOI: 10.1016/j.ejphar.2015.05.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 03/06/2015] [Accepted: 05/11/2015] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors are divided into three classes (A, B and C) based on homology of their seven transmembrane domains. Class C is the smallest class with 22 human receptor subtypes including eight metabotropic glutamate (mGlu1-8) receptors, two GABAB receptors (GABAB1 and GABAB2), three taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we review the existence of post-translational modifications in class C G protein-coupled receptors and their regulatory roles, with particular focus on glycosylation, phosphorylation, ubiquitination, SUMOylation, disulphide bonding and lipidation.
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Whitaker GM, Lynn FC, McIntosh CHS, Accili EA. Regulation of GIP and GLP1 receptor cell surface expression by N-glycosylation and receptor heteromerization. PLoS One 2012; 7:e32675. [PMID: 22412906 PMCID: PMC3296735 DOI: 10.1371/journal.pone.0032675] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 02/02/2012] [Indexed: 12/25/2022] Open
Abstract
In response to a meal, Glucose-dependent Insulinotropic Polypeptide (GIP) and Glucagon-like Peptide-1 (GLP-1) are released from gut endocrine cells into the circulation and interact with their cognate G-protein coupled receptors (GPCRs). Receptor activation results in tissue-selective pleiotropic responses that include augmentation of glucose-induced insulin secretion from pancreatic beta cells. N-glycosylation and receptor oligomerization are co-translational processes that are thought to regulate the exit of functional GPCRs from the ER and their maintenance at the plasma membrane. Despite the importance of these regulatory processes, their impact on functional expression of GIP and GLP-1 receptors has not been well studied. Like many family B GPCRs, both the GIP and GLP-1 receptors possess a large extracellular N-terminus with multiple consensus sites for Asn-linked (N)-glycosylation. Here, we show that each of these Asn residues is glycosylated when either human receptor is expressed in Chinese hamster ovary cells. N-glycosylation enhances cell surface expression and function in parallel but exerts stronger control over the GIP receptor than the GLP-1 receptor. N-glycosylation mainly lengthens receptor half-life by reducing degradation in the endoplasmic reticulum. N-glycosylation is also required for expression of the GIP receptor at the plasma membrane and efficient GIP potentiation of glucose-induced insulin secretion from the INS-1 pancreatic beta cell line. Functional expression of a GIP receptor mutant lacking N-glycosylation is rescued by co-expressed wild type GLP1 receptor, which, together with data obtained using Bioluminescence Resonance Energy Transfer, suggests formation of a GIP-GLP1 receptor heteromer.
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Affiliation(s)
- Gina M. Whitaker
- Cardiovascular Research Group, University of British Columbia, Vancouver, British Columbia, Canada
- Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Francis C. Lynn
- Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher H. S. McIntosh
- Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- Diabetes Research Group, University of British Columbia, Vancouver, British Columbia, Canada
| | - Eric A. Accili
- Cardiovascular Research Group, University of British Columbia, Vancouver, British Columbia, Canada
- Life Sciences Institute, Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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7
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Albuminuria and glomerular damage in mice lacking the metabotropic glutamate receptor 1. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 178:1257-69. [PMID: 21356376 DOI: 10.1016/j.ajpath.2010.11.050] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 09/27/2010] [Accepted: 11/01/2010] [Indexed: 02/02/2023]
Abstract
The metabotropic glutamate (mGlu) receptor 1 (GRM1) has been shown to play an important role in neuronal cells by triggering, through calcium release from intracellular stores, various signaling pathways that finally modulate neuron excitability, synaptic plasticity, and mechanisms of feedback regulation of neurotransmitter release. Herein, we show that Grm1 is expressed in glomerular podocytes and that a glomerular phenotype is exhibited by Grm1(crv4) mice carrying a spontaneous recessive inactivating mutation of the gene. Homozygous Grm1(crv4/crv4) and, to a lesser extent, heterozygous mice show albuminuria, podocyte foot process effacement, and reduced levels of nephrin and other proteins known to contribute to the maintenance of podocyte cell structure. Overall, the present data extend the role of mGlu1 receptor to the glomerular filtration barrier. The regulatory action of mGlu1 receptor in dendritic spine morphology and in the control of glutamate release is well acknowledged in neuronal cells. Analogously, we speculate that mGlu1 receptor may regulate foot process morphology and intercellular signaling in the podocyte.
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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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Deriu D, Gassmann M, Firbank S, Ristig D, Lampert C, Mosbacher J, Froestl W, Kaupmann K, Bettler B, Grütter M. Determination of the minimal functional ligand-binding domain of the GABAB1b receptor. Biochem J 2005; 386:423-31. [PMID: 15482257 PMCID: PMC1134860 DOI: 10.1042/bj20040804] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the mammalian central nervous system, slow inhibitory neurotransmission is largely mediated by metabotropic GABA(B) receptors (where GABA stands for gamma-aminobutyric acid), which belong to the G-protein-coupled receptor gene family. Functional GABA(B) receptors are assembled from two subunits GABA(B1) (GABA(B) receptor subtype 1) and GABA(B2). For the GABA(B1) subunit, which binds the neurotransmitter GABA, two variants GABA(B1a) (GABA(B) receptor subtype 1 variant a) and GABA(B1b) have been identified. They differ at the very N-terminus of their large glycosylated ECD (extracellular domain). To simplify the structural characterization, we designed truncated GABA(B1) receptors to identify the minimal functional domain which still binds a competitive radioligand and leads to a functional, GABA-responding receptor when co-expressed with GABA(B2). We show that it is necessary to include all the portion of the ECD encoded by exon 6 to exon 14. Furthermore, we studied mutant GABA(B1b) receptors, in which single or all potential N-glycosylation sites are removed. The absence of oligosaccharides does not impair receptor function, suggesting that the unglycosylated ECD of GABA(B1) can be used for further functional or structural investigations.
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Affiliation(s)
- Daniela Deriu
- *Institute of Biochemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Martin Gassmann
- †Department of Clinical-Biological Sciences, University of Basel, Pharmazentrum, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
| | - Susan Firbank
- *Institute of Biochemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
| | - Dorothee Ristig
- ‡Novartis, Institute of Biomedical Research Basel, CH-4002 Basel, Switzerland
| | - Christina Lampert
- ‡Novartis, Institute of Biomedical Research Basel, CH-4002 Basel, Switzerland
| | - Johannes Mosbacher
- ‡Novartis, Institute of Biomedical Research Basel, CH-4002 Basel, Switzerland
| | - Wolfgang Froestl
- ‡Novartis, Institute of Biomedical Research Basel, CH-4002 Basel, Switzerland
| | - Klemens Kaupmann
- ‡Novartis, Institute of Biomedical Research Basel, CH-4002 Basel, Switzerland
| | - Bernhard Bettler
- †Department of Clinical-Biological Sciences, University of Basel, Pharmazentrum, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
| | - Markus G. Grütter
- *Institute of Biochemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
- To whom correspondence should be addressed (email )
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Quirk PL, Rao S, Roth BL, Siegel RE. Three putative N-glycosylation sites within the murine 5-HT3A receptor sequence affect plasma membrane targeting, ligand binding, and calcium influx in heterologous mammalian cells. J Neurosci Res 2004; 77:498-506. [PMID: 15264219 DOI: 10.1002/jnr.20185] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The serotonin type 3(A) receptor (5-HT3(A)R) is a ligand-gated ion channel (LGIC) that modulates a diverse set of cognitive and physiological functions. The 5-HT3(A)R, as with other LGICs, is a pentameric ion channel comprising five glycoprotein subunits. Although the N-terminal of the 5-HT3(A)R contains three putative N-linked glycosylation sites, the importance of each glycosylation site has not yet been established. To address this question, we used tunicamycin treatment and site-directed mutagenesis to inhibit selectively N-linked glycosylation at each site and then examined the effects of these treatments on receptor expression and function in transiently transfected heterologous cells. We show that the murine 5-HT3(A)R is glycosylated and that each N-linked glycosylation site plays a role in receptor regulation. Our findings suggest that N109 is necessary for receptor assembly, whereas N174 and N190 are important for plasma membrane targeting and ligand binding. Furthermore, we demonstrate that each site is necessary for 5-HT3(A)R-mediated Ca(2+) influx. We conclude that N-glycosylation is a critical step in the maturation, trafficking, and function of the murine 5-HT3(A)R.
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Affiliation(s)
- Phillip L Quirk
- Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106-4965, USA
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Michineau S, Muller L, Pizard A, Alhenc-Gélas F, Rajerison RM. N-linked glycosylation of the human bradykinin B2 receptor is required for optimal cell-surface expression and coupling. Biol Chem 2004; 385:49-57. [PMID: 14977046 DOI: 10.1515/bc.2004.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
To investigate the glycosylation of the human bradykinin B2 receptor and the functional significance of this modification, we studied receptors mutated at single or multiple combinations of the three potential N-linked glycosylation sites, asparagines N3, N12 and N180, in COS-7, HEK 293 and CHO-K1 cells. Western blot experiments demonstrated that all three extracellular asparagines are glycosylated. The kinetics of bradykinin binding and receptor sequestration remained unchanged after glycosylation had been suppressed. However, the glycosylated receptors were expressed at the cell-surface to a much greater extent than the non-glycosylated receptor and coupling to phospholipase C was less efficient for receptor lacking N-terminal glycosylation. These results indicate that, for the human bradykinin B2 receptor, glycosylation is not required for optimal ligand binding, but plays an important role in cell-surface addressing and receptor function.
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12
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Hilgemann DW, Feng S, Nasuhoglu C. The complex and intriguing lives of PIP2 with ion channels and transporters. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2001; 2001:re19. [PMID: 11734659 DOI: 10.1126/stke.2001.111.re19] [Citation(s) in RCA: 368] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Phosphatidylinositol-4,5-bisphosphate (PIP(2)), the precursor of several signaling molecules in eukayotic cells, is itself also used by cells to signal to membrane-associated proteins. PIP(2) anchors numerous signaling molecules and cytoskeleton at the cell membrane, and the metabolism of PIP(2) is closely connected to membrane trafficking. Recently, ion transporters and channels have been discovered to be regulated by PIP(2). Systems reported to be activated by PIP(2) include (i) plasmalemmal calcium pumps (PMCA), (ii) cardiac sodium-calcium exchangers (NCX1), (iii) sodium-proton exchangers (NHE1-4), (iv) a sodium-magnesium exchanger of unknown identity, (v) all inward rectifier potassium channels (KATP, IRK, GIRK, and ROMK channels), (vi) epithelial sodium channels (ENaC), and (vii) ryanodine-sensitive calcium release channels (RyR). Systems reported to be inhibited by PIP(2) include (i) cyclic nucleotide-gated channels of the rod (CNG), (ii) transient receptor potential-like (TRPL) Drosophila phototransduction channels, (iii) capsaicin-activated transient receptor potential (TRP) channels (VR1), and (iv) IP(3)-gated calcium release channels (IP3R). Systems that appear to be completely insensitive to PIP(2) include (i) voltage-gated sodium channels, (ii) most voltage-gated potassium channels, (iii) sodium-potassium pumps, (iv) several neurotransmitter transporters, and (v) cystic fibrosis transmembrane receptor (CFTR)-type chloride channels. Presumably, local changes of the concentration of PIP(2) in the plasma membrane represent cell signals to those mechanisms sensitive to PIP(2) changes. Unfortunately, our understanding of how local PIP(2) concentrations are regulated remains very limited. One important complexity is the probable existence of phospholipid microdomains, or lipid rafts. Such domains may serve to localize PIP(2) and thereby PIP(2) signaling, as well as to organize PIP(2) binding partners into signaling complexes. A related biological role of PIP(2) may be to control the activity of ion transporters and channels during biosynthesis or vesicle trafficking. Low PIP(2) concentrations in the secretory pathway would inactivate all of the systems that are stimulated by PIP(2). How, in detail, is PIP(2) used by cells to control ion channel and transporter activities? Further progress requires an improved understanding of lipid kinases and phosphatases, how they are regulated, where they are localized in cells, and with which ion channels and transporters they might localize.
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Affiliation(s)
- D W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA.
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Hermans E, Challiss RA. Structural, signalling and regulatory properties of the group I metabotropic glutamate receptors: prototypic family C G-protein-coupled receptors. Biochem J 2001; 359:465-84. [PMID: 11672421 PMCID: PMC1222168 DOI: 10.1042/0264-6021:3590465] [Citation(s) in RCA: 208] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In 1991 a new type of G-protein-coupled receptor (GPCR) was cloned, the type 1a metabotropic glutamate (mGlu) receptor, which, despite possessing the defining seven-transmembrane topology of the GPCR superfamily, bore little resemblance to the growing number of other cloned GPCRs. Subsequent studies have shown that there are eight mammalian mGlu receptors that, together with the calcium-sensing receptor, the GABA(B) receptor (where GABA is gamma-aminobutyric acid) and a subset of pheromone, olfactory and taste receptors, make up GPCR family C. Currently available data suggest that family C GPCRs share a number of structural, biochemical and regulatory characteristics, which differ markedly from those of the other GPCR families, most notably the rhodopsin/family A GPCRs that have been most widely studied to date. This review will focus on the group I mGlu receptors (mGlu1 and mGlu5). This subgroup of receptors is widely and differentially expressed in neuronal and glial cells within the brain, and receptor activation has been implicated in the control of an array of key signalling events, including roles in the adaptative changes needed for long-term depression or potentiation of neuronal synaptic connectivity. In addition to playing critical physiological roles within the brain, the mGlu receptors are also currently the focus of considerable attention because of their potential as drug targets for the treatment of a variety of neurological and psychiatric disorders.
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Affiliation(s)
- E Hermans
- Laboratoire de Pharmacologie, Université Catholique de Louvain (54.10), B-1200 Brussels, Belgium.
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14
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Nash MS, Selkirk JV, Gaymer CE, Challiss RA, Nahorski SR. Enhanced inducible mGlu1alpha receptor expression in Chinese hamster ovary cells. J Neurochem 2001; 77:1664-7. [PMID: 11413250 DOI: 10.1046/j.1471-4159.2001.00405.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Inducible expression of the group-I metabotropic glutamate receptor (mGlu1alpha) in Chinese hamster ovary cells allows for the study of receptor density dependent effects. However, expression levels attainable with this system are lower than those reported for various brain regions and achieved by conventional (constitutive) transfection. Thus, direct comparison of mGlu1alpha receptor-mediated responses in this inducible expression system with those for receptors expressed heterologously or in vivo is compounded. We show here that inducible expression can be selectively augmented by butyrate pretreatment to levels approaching those reported for cerebral tissue. Enhanced mGlu1alpha receptor protein levels, agonist-induced inositol phosphate accumulation, as well as single-cell inositol 1,4,5-trisphosphate production and intracellular Ca(2+) mobilization occurred following co-induction with butyrate. In contrast, endogenous purinoceptor function was unaffected. Importantly, the ability to titrate receptor expression by varying isopropyl beta-thiogalactoside concentration was retained. Sodium butyrate thus offers a simple and convenient method to enhance inducible gene expression to levels found in vivo.
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Affiliation(s)
- M S Nash
- Department of Cell Physiology and Pharmacology, University of Leicester, UK.
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15
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Tiwari-Woodruff SK, Buznikov AG, Vu TQ, Micevych PE, Chen K, Kornblum HI, Bronstein JM. OSP/claudin-11 forms a complex with a novel member of the tetraspanin super family and beta1 integrin and regulates proliferation and migration of oligodendrocytes. J Cell Biol 2001; 153:295-305. [PMID: 11309411 PMCID: PMC2169454 DOI: 10.1083/jcb.153.2.295] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Oligodendrocyte-specific protein (OSP)/claudin-11 is a major component of central nervous system myelin and forms tight junctions (TJs) within myelin sheaths. TJs are essential for forming a paracellular barrier and have been implicated in the regulation of growth and differentiation via signal transduction pathways. We have identified an OSP/claudin-11-associated protein (OAP)1, using a yeast two-hybrid screen. OAP-1 is a novel member of the tetraspanin superfamily, and it is widely expressed in several cell types, including oligodendrocytes. OAP-1, OSP/claudin-11, and beta1 integrin form a complex as indicated by coimmunoprecipitation and confocal immunocytochemistry. Overexpression of OSP/claudin-11 or OAP-1 induced proliferation in an oligodendrocyte cell line. Anti-OAP-1, anti-OSP/claudin-11, and anti-beta1 integrin antibodies inhibited migration of primary oligodendrocytes, and migration was impaired in OSP/claudin-11-deficient primary oligodendrocytes. These data suggest a role for OSP/claudin-11, OAP-1, and beta1 integrin complex in regulating proliferation and migration of oligodendrocytes, a process essential for normal myelination and repair.
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Affiliation(s)
- Seema K. Tiwari-Woodruff
- Department of Neurology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Alex G. Buznikov
- Department of Neurology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Trung Q. Vu
- Department of Neurology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Paul E. Micevych
- Department of Neurobiology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
- Department of Molecular and Medical Pharmacology and Pediatrics, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Kendall Chen
- Department of Neurology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Harley I. Kornblum
- Department of Molecular and Medical Pharmacology and Pediatrics, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
- The Brain Research Institute, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
| | - Jeff M. Bronstein
- Department of Neurology, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
- The Brain Research Institute, University of California at Los Angeles School of Medicine, Los Angeles, California 90095
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16
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Selkirk JV, Price GW, Nahorski SR, Challiss RA. Cell type-specific differences in the coupling of recombinant mGlu1alpha receptors to endogenous G protein sub-populations. Neuropharmacology 2001; 40:645-56. [PMID: 11311892 DOI: 10.1016/s0028-3908(00)00208-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In this study the effects of cell background on the coupling of the type 1alpha metabotropic glutamate (mGlu1alpha) receptor to different G protein sub-populations by recombinant expression of this receptor subtype in baby hamster kidney (BHK) and Chinese hamster ovary (CHO) cells have been investigated. Receptor-G protein interactions were assessed using [(35)S]GTPgammaS binding and subsequent Galpha subunit-specific immunoprecipitation. In a CHO cell line (CHO-lac-mGlu1alpha), where mGlu1alpha receptor expression is under inducible control, stimulation of membranes with the mGlu receptor agonist quisqualate resulted in an increase in specific [(35)S]GTPgammaS binding to G(q/11)alpha only, whereas in a BHK cell line (BHK-mGlu1alpha) agonist stimulation increased [(35)S]GTPgammaS binding to G(q/11)alpha and also to pertussis toxin (PTx)-sensitive G(i/o) proteins (assessed using G(i1/2)alpha- and G(i3/o)alpha-specific antibodies). These data are consistent with our previous observations of dual, antagonistic G(q/11)/G(i/o) regulation of phospholipase C (PLC) in BHK-mGlu1alpha cells, whereas no evidence was found for a G(i/o) modulation of PLC activity in the CHO-lac-mGlu1alpha cell line. PTx pre-treatment of either cell line had no effect on either the magnitude or the concentration-dependency of agonist-stimulated [(35)S]GTPgammaS-G(q/11)alpha binding, excluding the possibility that receptor-G(i/o) uncoupling can unmask an increase in receptor-G(q/11) interaction. mGlu1alpha receptor expression per se had little effect on Galpha protein expression levels in either CHO or BHK cell lines, with the possible exception of a small, but consistent increase in G(o)alpha expression in BHK-mGlu1alpha cells compared to the vector-transfected control cell line (BHK-570). Semi-quantitative assessment of mGlu1alpha receptor immunoreactivity and [(3)H]quisqualate saturation binding analysis demonstrated a ca 10-fold higher mGlu1alpha receptor content in BHK cells. Whether the higher receptor expression level in BHK-mGlu1alpha cells underlies the additional G(i/o) coupling observed in this cell line, or additional factors contribute to the phenomenon are discussed.
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Affiliation(s)
- J V Selkirk
- Department of Cell Physiology and Pharmacology, Maurice Shock Medical Sciences Building, University of Leicester, University Road, Leicester LE1 9HN, UK.
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17
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Pei D, Kang T, Qi H. Cysteine array matrix metalloproteinase (CA-MMP)/MMP-23 is a type II transmembrane matrix metalloproteinase regulated by a single cleavage for both secretion and activation. J Biol Chem 2000; 275:33988-97. [PMID: 10945999 DOI: 10.1074/jbc.m006493200] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Matrix metalloproteinases characterized so far are either secreted or membrane anchored via a type I transmembrane domain or a glycosylphosphatidylinositol linkage. Lacking either membrane-anchoring mechanism, the newly discovered CA-MMP/MMP-23 was reported to be expressed as a cell-associated protein. In this report, we present evidence that CA-MMP is expressed as an integral membrane zymogen with an N-terminal signal anchor, and secreted as a fully processed mature enzyme. We further demonstrate that L(20)GAALSGLCLLSALALL(36) is required for this unique membrane localization as a signal anchor and its secretion is regulated by a proprotein convertase motif RRRR(79) sandwiched between its pro- and catalytic domains. Thus, CA-MMP is a type II transmembrane MMP that can be regulated by a single proteolytic cleavage for both activation and secretion, establishing a novel paradigm for protein trafficking and processing within the secretory pathway.
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Affiliation(s)
- D Pei
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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18
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Hermans E, Saunders R, Selkirk JV, Mistry R, Nahorski SR, Challiss RA. Complex involvement of pertussis toxin-sensitive G proteins in the regulation of type 1alpha metabotropic glutamate receptor signaling in baby hamster kidney cells. Mol Pharmacol 2000; 58:352-60. [PMID: 10908303 DOI: 10.1124/mol.58.2.352] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously, we demonstrated that the coupling of the metabotropic glutamate receptor mGlu1alpha to phosphoinositide hydrolysis is enhanced by pertussis toxin (PTX) in stably transfected baby hamster kidney cells (BHK). Here, we show that the PTX effect on agonist-stimulated [(3)H]inositol phosphate accumulation can be resolved into two components: an immediate increase in agonist potency, and a more slowly developing increase in the magnitude of the response observed at maximally effective agonist concentrations. Using G(q/11)alpha- and G(i/o)alpha-selective antibodies to immunoprecipitate [(35)S]guanosine-5'-O-(3-thio)triphosphate-bound Galpha proteins, we also show that agonist stimulation of mGlu1alpha in BHK membranes increases specific [(35)S]guanosine-5'-O-(3-thio)triphosphate binding to both G(q/11) and G(i/o) proteins. Preincubation of BHK-mGlu1alpha with L-glutamate (300 microM) results in a progressive loss (60% in 30 min) of L-quisqualate-induced [(3)H]inositol phosphate accumulation (without a change in potency), providing evidence for agonist-induced receptor desensitization. Although such desensitization of mGlu receptor signaling was mimicked by a phorbol ester, agonist-induced phosphorylation of the receptor was not observed and protein kinase C inhibition by Ro 31-8220 did not prevent L-glutamate-mediated desensitization. In contrast, PTX treatment of the cells almost completely prevented L-glutamate-mediated desensitization. Together, these data provide evidence for a multifunctional coupling of mGlu1alpha to different types of G proteins, including PTX-sensitive G(i)-type G proteins. The latter are involved in the negative control of phospholipase C activity while also influencing the rate of desensitization of the mGlu1alpha receptor.
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Affiliation(s)
- E Hermans
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom.
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