Metabotropic Glutamate receptors (mGluRs) belong to Family C GPCRs. Interestingly enough receptors for Gamma-amino butyric acid, the GABAb receptors from this family, were first discovered putative heterodimers.
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Increasing evidence indicates that heterotrimeric G proteins, and in particular Go, regulate ionic channel activities. In order to investigate the role of Go proteins in the modulation of the Ca2+ influx, C6 glioma cells were stably... more
Increasing evidence indicates that heterotrimeric G proteins, and in particular Go, regulate ionic channel activities. In order to investigate the role of Go proteins in the modulation of the Ca2+ influx, C6 glioma cells were stably transfected with alpha o1 cDNA. Expression of the Go1 alpha protein was checked by Bordetella pertussis toxin-catalyzed ADP-ribosylation and Western blots using one- and two-dimensional gel analyses. Three clones were selected based on their degree of Go1 alpha expression. In alpha o1-transfected cells, cAMP accumulations, in response to isoproterenol or forskolin, were lower than in control cells. This inhibitory effect was a function of the amount of expressed Go1 alpha. In contrast, Go1 alpha expression was not followed by a significant inhibition of isoproterenol- or forskolin-stimulated adenylyl cyclase activities in particulate fractions. In C6 parental cells, 50-60% of the isoproterenol-induced cAMP accumulation was dependent on external Ca2+ concentration. This Ca(2+)-dependent cAMP accumulation was related to an induced transient Ca2+ influx. In transfected cells, expression of Go1 alpha inhibited the Ca2+ influx and the Ca(2+)-dependent component of isoproterenol-induced cAMP accumulation. In conclusion, beta-adrenergic agonists stimulate an entry of Ca2+ which exerts a positive feedback on cAMP production, and Go1 alpha blocks this positive feedback by inhibiting the Ca2+ influx.
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In primary cultures of striatal neurons, stimulation of N-methyl-D-aspartic acid (NMDA) receptors or associative activation (but not separate activation) of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors... more
In primary cultures of striatal neurons, stimulation of N-methyl-D-aspartic acid (NMDA) receptors or associative activation (but not separate activation) of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and metabotropic glutamate receptors (mGluR) strongly increased arachidonic acid (AA) release via activation of phospholipase A2 (PLA2). Depolarizing agents, such as veratridine, were as potent as NMDA in stimulating AA release. However, increasing the intracellular Ca2+ concentration via voltage-sensitive Ca2+ channels did not result in a significant stimulation of PLA2. Substitution of sodium by lithium, a monovalent cation that does not participate in the Na+/Ca2+ exchanger activity but permeates ionotropic glutamate receptor channels, blocked AA release induced by veratridine or AMPA plus mGluR agonists. It also reduced the NMDA-induced AA release, to a lesser extent. The contribution of the Na+/Ca2+ exchanger to the activation of PLA2 after veratridine, NMDA receptor, or AMPA receptor plus mGluR stimulation was confirmed by using a selective inhibitor of the Na+/Ca2+ exchanger.
Research Interests: Chemistry, Electrophysiology, Calcium, Molecular Pharmacology, Medicine, and 15 moreMice, Pubmed, Animals, Neurons, Long Term Depression, Sodium, Stimulation, Neurosciences, Arachidonic Acid, Glutamate Receptor, Corpus striatum, NMDA receptor, NBQX, Protein Kinase C, and Pharmacology and pharmaceutical sciences
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Research Interests: Analytical Chemistry, Biology, Fluorescent Dyes and Reagents, Medicine, Fluorescence Resonance Energy Transfer, and 15 moreBiological Sciences, Antibodies, Humans, High throughput screening, Animals, Drug Design, CHEMICAL SCIENCES, Energy Transfer, Ligands, Biosensing Techniques, Biochemistry and cell biology, Cell Membrane, Homogeneous, fluorescent dyes, and G Protein Coupled Receptors
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ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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G protein-coupled receptors (GPCRs) are important drug targets that mediate various signaling pathways by activating G proteins and engaging β-arrestin proteins. Despite its importance for the development of therapeutics with fewer side... more
G protein-coupled receptors (GPCRs) are important drug targets that mediate various signaling pathways by activating G proteins and engaging β-arrestin proteins. Despite its importance for the development of therapeutics with fewer side effects, the underlying mechanism that controls the balance between these signaling modes of GPCRs remains largely unclear. Here, we show that assembly into dimers and oligomers can largely influence the signaling mode of the platelet-activating factor receptor (PAFR). Single-particle analysis results show that PAFR can form oligomers at low densities through two possible dimer interfaces. Stabilization of PAFR oligomers through cross-linking increases G protein activity, and decreases β-arrestin recruitment and agonist-induced internalization significantly. Reciprocally, β-arrestin prevents PAFR oligomerization. Our results highlight a mechanism involved in the control of receptor signaling, and thereby provide important insights into the relationsh...
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New technologies based on luminescence have been essential to monitor the organization, signaling, trafficking or ligand binding of G Protein-Coupled Receptors (GPCRs), but they rely on the overexpression of genetically modified... more
New technologies based on luminescence have been essential to monitor the organization, signaling, trafficking or ligand binding of G Protein-Coupled Receptors (GPCRs), but they rely on the overexpression of genetically modified receptors. As more and more studies indicate the importance of studying native receptors in their natural environment, it is essential to develop approaches allowing the specific labeling of native receptors. Here we report an innovative ligand directed approach to specifically label residues of native GPCRs upon ligand binding. To this end, we developed a ligand-directed toolbox based on a novel approach that uses molecular modules to build fluorescent ligand-directed probes that can label an archetypical aminergic GPCR (D1R). Our probes can be readily prepared before the labeling reaction from two molecular modules: an activated electrophilic linker which includes a fluorescent dye and a GPCR ligand that may include nucleophilic groups. Thanks to a fast an...
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Although presynaptic localization of mGluR7 is well established, the mechanism by which the receptor may control Ca2+channels in neurons is still unknown. We show here that cultured cerebellar granule cells express native metabotropic... more
Although presynaptic localization of mGluR7 is well established, the mechanism by which the receptor may control Ca2+channels in neurons is still unknown. We show here that cultured cerebellar granule cells express native metabotropic glutamate receptor type 7 (mGluR7) in neuritic processes, whereas transfected mGluR7 was also expressed in cell bodies. This allowed us to study the effect of the transfected receptor on somatic Ca2+channels. In transfected neurons, mGuR7 selectively inhibited P/Q-type Ca2+channels. The effect was mimicked by GTPγS and blocked by pertussis toxin (PTX) or a selective antibody raised against the G-protein αo subunit, indicating the involvement of a Go-like protein. The mGuR7 effect did not display the characteristics of a direct interaction between G-protein βγ subunits and the α1A Ca2+channel subunit, but was abolished by quenching βγ subunits with specific intracellular peptides. Intracellular dialysis of G-protein βγ subunits did not mimic the action ...
Research Interests: Neuroscience, Biology, Cell Biology, Medicine, Signal Transduction, and 15 moreAntibodies, Cerebellum, Mice, Animals, Calcium Channel, Synaptic Transmission, Neurons, Barium, Transfection, G protein, Calcium Channel Blockers, Phospholipase C, Psychology and Cognitive Sciences, Protein Kinase C, and Medical and Health Sciences
Metabotropic glutamate receptors (mGluRs) are mandatory dimers playing important roles in regulating CNS function. Although assumed to form exclusive homodimers, 16 possible heterodimeric mGluRs have been proposed but their existence in... more
Metabotropic glutamate receptors (mGluRs) are mandatory dimers playing important roles in regulating CNS function. Although assumed to form exclusive homodimers, 16 possible heterodimeric mGluRs have been proposed but their existence in native cells remains elusive. Here, we set up two assays to specifically identify the pharmacological properties of rat mGlu heterodimers composed of mGlu2 and 4 subunits. We used either a heterodimer-specific conformational LRET-based biosensor or a system that guarantees the cell surface targeting of the heterodimer only. We identified mGlu2-4 specific pharmacological fingerprints that were also observed in a neuronal cell line and in lateral perforant path terminals naturally expressing mGlu2 and mGlu4. These results bring strong evidence for the existence of mGlu2-4 heterodimers in native cells. In addition to reporting a general approach to characterize heterodimeric mGluRs, our study opens new avenues to understanding the pathophysiological rol...
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The metabotropic glutamate receptors (mGluRs) share no sequence homology and show different structural features compared with most other G protein-coupled receptors (GPCRs). In particular, some isoforms of the phospholipase C... more
The metabotropic glutamate receptors (mGluRs) share no sequence homology and show different structural features compared with most other G protein-coupled receptors (GPCRs). In particular, some isoforms of the phospholipase C (PLC)-coupled mGluRs (mGluR1a, mGluR5a, and mGluR5b) have a surprisingly long carboxyl-terminal intracellular domain of more than 350 residues, whereas the splice variants mGluR1b and mGluR1c have a much shorter carboxyl terminus. In the current study, the different splice variants of mGluR1 were expressed in porcine kidney epithelial (LLC-PK1) or the human embryonic kidney (HEK 293) cells, and their levels of expression were examined with the use of Western blot analysis. Expression of the short isoforms mGluR1b and mGluR1c did not modify the basal inositol phosphate production. In contrast, expression to similar levels of mGluR1a resulted in a 2-fold increase in the basal inositol phosphate formation. This increase in basal PLC activity was due to neither the...
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Both subunits in the metabotropic glutamate receptor 1 dimer move relative to each other before one adopts an active conformation.
Research Interests: Chemistry, Kinetics, Calcium, Confocal Microscopy, Medicine, and 12 moreFluorescence Resonance Energy Transfer, Cercopithecus aethiops, Humans, Animals, Metabotropic Glutamate Receptors, Polymerase Chain Reaction, Synaptic Transmission, Protein Conformation, Biochemistry and cell biology, Dimerization, Glutamate Receptor, and Protein subunits
A splice variant of the metabotropic glutamate receptor (mGluR) 1a, named mGluR1c, was isolated. Compared to mGluR1a, the predicted mGluR1c protein is 302 amino acids shorter at its C-terminal end. Despite this difference, mGluR1c... more
A splice variant of the metabotropic glutamate receptor (mGluR) 1a, named mGluR1c, was isolated. Compared to mGluR1a, the predicted mGluR1c protein is 302 amino acids shorter at its C-terminal end. Despite this difference, mGluR1c activates phospholipase C in Xenopus oocytes with a pharmacological profile identical to that of mGluR1a. However, in contrast to the large fast transient responses induced by mGluR1a, mGluR1c receptors elicit a small more slowly generated long-lasting oscillatory current, suggesting that these two receptors do not generate the same pattern of Ca2+ release in Xenopus oocytes. In situ hybridization data show that mGluR1c mRNA is expressed at a lower level than the other splice variants of mGluR1. Some differences in the regional distribution of these transcripts were observed in the cerebellum, the olfactory bulb, and the striatum.
Research Interests: Biology, Calcium, Medicine, Multidisciplinary, Xenopus, and 15 moreAnimals, Polymerase Chain Reaction, Alternative splicing, D-Aspartic Acid, Neurotoxins, Olfactory Bulb, Alternative Splicing, Amino Acid Sequence, Base Sequence, Transient Response, Oocytes, Phospholipase C, Molecular Sequence Data, Kainic acid, and Restriction Mapping
Research Interests: Chemistry, Biological Chemistry, Medicine, Biological Sciences, Animals, and 13 moreMetabotropic Glutamate Receptors, Stereochemistry, CHEMICAL SCIENCES, Rats, Pyridines, Amino Acid Sequence, Chromones, Structure activity Relationship, Molecular Sequence Data, binding sites, CHO cells, Cricetinae, and Medical and Health Sciences
Research Interests: Biology, Cell Biology, Biological Chemistry, Medicine, Signal Transduction, and 14 moreBiological Sciences, Internalization, Hippocampus, Cercopithecus aethiops, Mice, Animals, Potassium, Neurons, CHEMICAL SCIENCES, Receptor, Potassium Channels, Knockout Mice, Cell Membrane, and Medical and Health Sciences
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Class-C GPCRs have become an increasingly important target class for new therapies, particularly in areas such as pain, anxiety, neurodegenerative disorders and as antispasmodics, but also potentially for the treatment of hyperthyroidism... more
Class-C GPCRs have become an increasingly important target class for new therapies, particularly in areas such as pain, anxiety, neurodegenerative disorders and as antispasmodics, but also potentially for the treatment of hyperthyroidism and osteoporosis. Both positive and ...
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The design and synthesis of 2-(3'-(1H-tetrazol-5-yl)bicyclo[1.1.1]pent-1-yl)glycine (S-TBPG), a novel mGluR1 antagonist is reported. S-TBPG is characterized by the bioisosteric replacement of the distal carboxy group of... more
The design and synthesis of 2-(3'-(1H-tetrazol-5-yl)bicyclo[1.1.1]pent-1-yl)glycine (S-TBPG), a novel mGluR1 antagonist is reported. S-TBPG is characterized by the bioisosteric replacement of the distal carboxy group of 2-(3'-carboxybicyclo [1.1.1]pent-1-yl)glycine (S-CBPG) by a tetrazolyl moiety. Despite a moderate reduction in potency, S-TBPG is a selective mGluR1 antagonist (69 microM), with no activity at other mGluR subtypes. The interesting biological profile of S-TBPG, coupled with its peculiar chemical structure, is discussed in terms of the structure activity relationship (SAR) of mGluR1 antagonists.
Research Interests: Chemistry, Organic Chemistry, Medicine, Cell line, Humans, and 14 moreMetabotropic Glutamate Receptors, Stereochemistry, Antagonist, Glutamine, Glycine, Bioorganic and medicinal Chemistry, Structure activity Relationship, Chemical Synthesis, Chemical Structure, Minimum inhibitory concentration, Tetrazoles, Inositol Phosphates, Pharmacology and pharmaceutical sciences, and Minimum Inhibitory Concentration(Metabotropic Glutamate Receptors, Stereochemistry, Antagonist, Glutamine, Glycine, Bioorganic and medicinal Chemistry, Structure activity Relationship, Chemical Synthesis, Chemical Structure, Minimum inhibitory concentration, Tetrazoles, Inositol Phosphates, Pharmacology and pharmaceutical sciences, and Minimum Inhibitory Concentration)
(Metabotropic Glutamate Receptors, Stereochemistry, Antagonist, Glutamine, Glycine, Bioorganic and medicinal Chemistry, Structure activity Relationship, Chemical Synthesis, Chemical Structure, Minimum inhibitory concentration, Tetrazoles, Inositol Phosphates, Pharmacology and pharmaceutical sciences, and Minimum Inhibitory Concentration)
G‐protein‐coupled receptors (GPCRs) are key players in the precise tuning of intercellullar communication. In the brain, both major neurotransmitters, glutamate and GABA, act on specific GPCRs [the metabotropic glutamate (mGlu) and GABAB... more
G‐protein‐coupled receptors (GPCRs) are key players in the precise tuning of intercellullar communication. In the brain, both major neurotransmitters, glutamate and GABA, act on specific GPCRs [the metabotropic glutamate (mGlu) and GABAB receptors] to modulate synaptic transmission. These receptors are encoded by the largest gene family, and have been found to associate into both homo‐ and hetero‐oligomers, which increases the complexity of this cell communication system. Here we show that dimerization is required for mGlu and GABAB receptors to function, since the activation process requires a relative movement between the subunits to occur. We will also show that, in contrast to the mGlu receptors, which form strict dimers, the GABAB receptors assemble into larger complexes, both in transfected cells and in the brain, resulting in a decreased G‐protein coupling efficacy. We propose that GABAB receptor oligomerization offers a way to increase the possibility of modulating receptor ...
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Metabotropic glutamate receptors (mGluRs) are a family of G protein-coupled receptors characterized by a large, extracellular N-terminal domain comprising the glutamate-binding site. In the current study, we examined the pharmacological... more
Metabotropic glutamate receptors (mGluRs) are a family of G protein-coupled receptors characterized by a large, extracellular N-terminal domain comprising the glutamate-binding site. In the current study, we examined the pharmacological profile and site of action of the non-amino-acid antagonist 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt). CPCCOEt selectively inhibited glutamate-induced increases in intracellular calcium at human mGluR1b (hmGluR1b) with an apparent IC50 of 6.5 microM while having no agonist or antagonist activity at hmGluR2, -4a, -5a, -7b, and -8a up to 100 microM. Schild analysis indicated that CPCCOEt acts in a noncompetitive manner by decreasing the efficacy of glutamate-stimulated phosphoinositide hydrolysis without affecting the EC50 value or Hill coefficient of glutamate. Similarly, CPCCOEt did not displace [3H]glutamate binding to membranes prepared from mGluR1a-expressing cells. To elucidate the site of action, we systematica...
Research Interests: Biology, Molecular Pharmacology, Medicine, Signal Transduction, Molecular, and 15 moreHumans, Animals, Threonine, Rats, Alanine, Amino Acid Sequence, Chromones, Recombinant Proteins, Neurosciences, Glutamic Acid, Glutamate Receptor, Molecular Sequence Data, CHO cells, Cricetinae, and Pharmacology and pharmaceutical sciences
The effects of a nitric oxide (NO) donor, sodium nitroprusside (SNP), on N-methyl-D-aspartate (NMDA) receptors were assessed by optical measurements of intracellular calcium concentration ([Ca2+]i) and patch-clamp techniques in cultured... more
The effects of a nitric oxide (NO) donor, sodium nitroprusside (SNP), on N-methyl-D-aspartate (NMDA) receptors were assessed by optical measurements of intracellular calcium concentration ([Ca2+]i) and patch-clamp techniques in cultured central neurons. SNP selectively blocked NMDA-mediated currents and increases in [Ca2+]i. SNP inhibited the binding of [3H]-CGS 19755. The blockade of NMDA responses by SNP was prevented by CPP or APV which are selective competitive NMDA receptor antagonists. These effects were not necessarily mediated by NO, since they were mimicked by ferrocyanide ions, the NO companion photolysis product of SNP.
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Research Interests: Endocrinology, Physiology, Chemistry, Calcium, Medicine, and 15 moreAluminum, Internal Medicine, cyclic AMP, Female, Animals, Medical Physiology, Fluorine, Adrenocorticotropic Hormone, Angiotensin II, Biochemistry and cell biology, Intracellular Calcium, Calcium Channel Blockers, Intracellular, Phospholipase C, and Adrenal glands
The GABAB (γ-aminobutyric acid-B) receptor is composed of two subunits, GABAB1 and GABAB2. Both subunits share structural homology with other class-III G-protein-coupled receptors. They contain two main domains, a heptahelical domain... more
The GABAB (γ-aminobutyric acid-B) receptor is composed of two subunits, GABAB1 and GABAB2. Both subunits share structural homology with other class-III G-protein-coupled receptors. They contain two main domains, a heptahelical domain typical of all G-protein-coupled receptors and a large ECD (extracellular domain). It has not been demonstrated whether the association of these two subunits is always required for function. However, GABAB2 plays a major role in coupling with G-proteins, and GABAB1 has been shown to bind GABA. To date, only ligands interacting with GABAB1-ECD have been identified. In the present study, we explored the mechanism of action of CGP7930, a compound described as a positive allosteric regulator of the GABAB receptor. We have shown that it can weakly activate the wild-type GABAB receptor, but also the GABAB2 expressed alone, thus being the first described agonist of GABAB2. CGP7930 retains its weak agonist activity on a GABAB2 subunit deleted of its ECD. Thus t...
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We tested the effects of two enantiomers of a glutamate analogue,(trans)-1-aminocyclopentyl-1, 3-dicarboxylate (t-ACPD), in striatal and cerebellar neurons in primary culture, as well as in Xenopus oocytes injected with cerebellar rat... more
We tested the effects of two enantiomers of a glutamate analogue,(trans)-1-aminocyclopentyl-1, 3-dicarboxylate (t-ACPD), in striatal and cerebellar neurons in primary culture, as well as in Xenopus oocytes injected with cerebellar rat RNA. In the presence of ...