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Da Silva E, Scott MGH, Enslen H, Marullo S. Control of CCR5 Cell-Surface Targeting by the PRAF2 Gatekeeper. Int J Mol Sci 2023; 24:17438. [PMID: 38139265 PMCID: PMC10744302 DOI: 10.3390/ijms242417438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/08/2023] [Accepted: 12/09/2023] [Indexed: 12/24/2023] Open
Abstract
The cell-surface targeting of neo-synthesized G protein-coupled receptors (GPCRs) involves the recruitment of receptors into COPII vesicles budding at endoplasmic reticulum exit sites (ERESs). This process is regulated for some GPCRs by escort proteins, which facilitate their export, or by gatekeepers that retain the receptors in the ER. PRAF2, an ER-resident four trans- membrane domain protein with cytoplasmic extremities, operates as a gatekeeper for the GB1 protomer of the heterodimeric GABAB receptor, interacting with a tandem di-leucine/RXR retention motif in the carboxyterminal tail of GB1. PRAF2 was also reported to interact in a two-hybrid screen with a peptide corresponding to the carboxyterminal tail of the chemokine receptor CCR5 despite the absence of RXR motifs in its sequence. Using a bioluminescence resonance energy transfer (BRET)-based subcellular localization system, we found that PRAF2 inhibits, in a concentration-dependent manner, the plasma membrane export of CCR5. BRET-based proximity assays and Co-IP experiments demonstrated that PRAF2/CCR5 interaction does not require the presence of a receptor carboxyterminal tail and involves instead the transmembrane domains of both proteins. The mutation of the potential di-leucine/RXR motif contained in the third intracellular loop of CCR5 does not affect PRAF2-mediated retention. It instead impairs the cell-surface export of CCR5 by inhibiting CCR5's interaction with its private escort protein, CD4. PRAF2 and CD4 thus display opposite roles on the cell-surface export of CCR5, with PRAF2 inhibiting and CD4 promoting this process, likely operating at the level of CCR5 recruitment into COPII vesicles, which leave the ER.
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Affiliation(s)
| | | | | | - Stefano Marullo
- CNRS, INSERM, Institut Cochin, Université Paris Cité, F-75014 Paris, France; (E.D.S.); (M.G.H.S.); (H.E.)
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2
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Wang K, Liang Y, Duan M, Che W, He L. Chronic toxicity of broflanilide in Daphnia magna: changes in molting, behavior, and gene expression. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:54846-54856. [PMID: 36881221 DOI: 10.1007/s11356-023-26255-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 02/27/2023] [Indexed: 06/18/2023]
Abstract
Broflanilide is a novel pesticide used in agriculture that binds to unique receptors on pests; however, the widespread use of broflanilide has led to toxicity in Daphnia magna. At present, little information on the potential threats broflanilide imposes on D. magna is available. Therefore, the present study examined the chronic toxicity of broflanilide in D. magna by comparing changes in molting, neurotransmitter function, and behavior. The results showed that broflanilide caused chronic toxicity in D. magna at a concentration of 8.45 μg/L, and growth, development, reproduction, and the development of offspring were affected. In addition, broflanilide affected the molting of D. magna by significantly inhibiting the expression of chitinase, ecdysteroid, and related genes. Broflanilide also affected the expression of γ-glutamic acid, glutamine, gamma-aminobutyric acid, 5-hydroxytryptamine, 5-hydroxytryptophan, dopa, and dopamine. Furthermore, the swimming distance and speed of D. magna were reduced. Taken together, the results demonstrate the chronic toxicity and exposure risk of broflanilide in D. magna.
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Affiliation(s)
- Kai Wang
- Plant Protection College, Shenyang Agricultural University, Shenyang, China.
| | - Yaping Liang
- Plant Protection College, Shenyang Agricultural University, Shenyang, China
| | - Manman Duan
- College of Science, China Agricultural University, Beijing, China
| | - Wunan Che
- Plant Protection College, Shenyang Agricultural University, Shenyang, China
| | - Lu He
- Plant Protection College, Shenyang Agricultural University, Shenyang, China
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3
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Oligomerization of the heteromeric γ-aminobutyric acid receptor GABA B in a eukaryotic cell-free system. Sci Rep 2022; 12:20742. [PMID: 36456667 PMCID: PMC9715706 DOI: 10.1038/s41598-022-24885-0] [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: 07/28/2022] [Accepted: 11/22/2022] [Indexed: 12/03/2022] Open
Abstract
Understanding the assembly mechanism and function of membrane proteins is a fundamental problem in biochemical research. Among the membrane proteins, G protein-coupled receptors (GPCRs) represent the largest class in the human body and have long been considered to function as monomers. Nowadays, the oligomeric assembly of GPCRs is widely accepted, although the functional importance and therapeutic intervention remain largely unexplored. This is partly due to difficulties in the heterologous production of membrane proteins. Cell-free protein synthesis (CFPS) with its endogenous endoplasmic reticulum-derived structures has proven as a technique to address this issue. In this study, we investigate for the first time the conceptual CFPS of a heteromeric GPCR, the γ-aminobutyric acid receptor type B (GABAB), from its protomers BR1 and BR2 using a eukaryotic cell-free lysate. Using a fluorescence-based proximity ligation assay, we provide evidence for colocalization and thus suggesting heterodimerization. We prove the heterodimeric assembly by a bioluminescence resonance energy transfer saturation assay providing the manufacturability of a heterodimeric GPCR by CFPS. Additionally, we show the binding of a fluorescent orthosteric antagonist, demonstrating the feasibility of combining the CFPS of GPCRs with pharmacological applications. These results provide a simple and powerful experimental platform for the synthesis of heteromeric GPCRs and open new perspectives for the modelling of protein-protein interactions. Accordingly, the presented technology enables the targeting of protein assemblies as a new interface for pharmacological intervention in disease-relevant dimers.
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4
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Lotz-Havla AS, Woidy M, Guder P, Friedel CC, Klingbeil JM, Bulau AM, Schultze A, Dahmen I, Noll-Puchta H, Kemp S, Erdmann R, Zimmer R, Muntau AC, Gersting SW. iBRET Screen of the ABCD1 Peroxisomal Network and Mutation-Induced Network Perturbations. J Proteome Res 2021; 20:4366-4380. [PMID: 34383492 DOI: 10.1021/acs.jproteome.1c00330] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mapping the network of proteins provides a powerful means to investigate the function of disease genes and to unravel the molecular basis of phenotypes. We present an automated informatics-aided and bioluminescence resonance energy transfer-based approach (iBRET) enabling high-confidence detection of protein-protein interactions in living mammalian cells. A screen of the ABCD1 protein, which is affected in X-linked adrenoleukodystrophy (X-ALD), against an organelle library of peroxisomal proteins demonstrated applicability of iBRET for large-scale experiments. We identified novel protein-protein interactions for ABCD1 (with ALDH3A2, DAO, ECI2, FAR1, PEX10, PEX13, PEX5, PXMP2, and PIPOX), mapped its position within the peroxisomal protein-protein interaction network, and determined that pathogenic missense variants in ABCD1 alter the interaction with selected binding partners. These findings provide mechanistic insights into pathophysiology of X-ALD and may foster the identification of new disease modifiers.
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Affiliation(s)
- Amelie S Lotz-Havla
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Mathias Woidy
- University Children's Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Philipp Guder
- University Children's Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Caroline C Friedel
- Institute of Informatics, Ludwig-Maximilians-Universität München, 80538 Munich, Germany
| | - Julian M Klingbeil
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Ana-Maria Bulau
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Anja Schultze
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Ilona Dahmen
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Heidi Noll-Puchta
- Dr. von Hauner Children's Hospital, Ludwig-Maximilians-Universität München, 80337 Munich, Germany
| | - Stephan Kemp
- Department of Clinical Chemistry, Laboratory Genetic Metabolic Diseases, Amsterdam UMC, Amsterdam Neuroscience, Amsterdam Gastroenterology & Metabolism, University of Amsterdam, 1105 WX Amsterdam, The Netherlands
| | - Ralf Erdmann
- Systems Biochemistry, Medical Faculty, Ruhr-University Bochum, 44801 Bochum, Germany
| | - Ralf Zimmer
- Institute of Informatics, Ludwig-Maximilians-Universität München, 80538 Munich, Germany
| | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Søren W Gersting
- University Children's Research, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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5
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Shaye H, Stauch B, Gati C, Cherezov V. Molecular mechanisms of metabotropic GABA B receptor function. SCIENCE ADVANCES 2021; 7:7/22/eabg3362. [PMID: 34049877 PMCID: PMC8163086 DOI: 10.1126/sciadv.abg3362] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 04/14/2021] [Indexed: 05/06/2023]
Abstract
Metabotropic γ-aminobutyric acid G protein-coupled receptors (GABAB) represent one of the two main types of inhibitory neurotransmitter receptors in the brain. These receptors act both pre- and postsynaptically by modulating the transmission of neuronal signals and are involved in a range of neurological diseases, from alcohol addiction to epilepsy. A series of recent cryo-EM studies revealed critical details of the activation mechanism of GABAB Structures are now available for the receptor bound to ligands with different modes of action, including antagonists, agonists, and positive allosteric modulators, and captured in different conformational states from the inactive apo to the fully active state bound to a G protein. These discoveries provide comprehensive insights into the activation of the GABAB receptor, which not only broaden our understanding of its structure, pharmacology, and physiological effects but also will ultimately facilitate the discovery of new therapeutic drugs and neuromodulators.
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Affiliation(s)
- Hamidreza Shaye
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
| | - Benjamin Stauch
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
- Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
| | - Cornelius Gati
- Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Vadim Cherezov
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA.
- Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
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6
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Glial Metabolic Rewiring Promotes Axon Regeneration and Functional Recovery in the Central Nervous System. Cell Metab 2020; 32:767-785.e7. [PMID: 32941799 PMCID: PMC7642184 DOI: 10.1016/j.cmet.2020.08.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 07/07/2020] [Accepted: 08/26/2020] [Indexed: 12/25/2022]
Abstract
Axons in the mature central nervous system (CNS) fail to regenerate after axotomy, partly due to the inhibitory environment constituted by reactive glial cells producing astrocytic scars, chondroitin sulfate proteoglycans, and myelin debris. We investigated this inhibitory milieu, showing that it is reversible and depends on glial metabolic status. We show that glia can be reprogrammed to promote morphological and functional regeneration after CNS injury in Drosophila via increased glycolysis. This enhancement is mediated by the glia derived metabolites: L-lactate and L-2-hydroxyglutarate (L-2HG). Genetically/pharmacologically increasing or reducing their bioactivity promoted or impeded CNS axon regeneration. L-lactate and L-2HG from glia acted on neuronal metabotropic GABAB receptors to boost cAMP signaling. Local application of L-lactate to injured spinal cord promoted corticospinal tract axon regeneration, leading to behavioral recovery in adult mice. Our findings revealed a metabolic switch to circumvent the inhibition of glia while amplifying their beneficial effects for treating CNS injuries.
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7
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Xue L, Sun Q, Zhao H, Rovira X, Gai S, He Q, Pin JP, Liu J, Rondard P. Rearrangement of the transmembrane domain interfaces associated with the activation of a GPCR hetero-oligomer. Nat Commun 2019; 10:2765. [PMID: 31235691 PMCID: PMC6591306 DOI: 10.1038/s41467-019-10834-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 06/04/2019] [Indexed: 02/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) can integrate extracellular signals via allosteric interactions within dimers and higher-order oligomers. However, the structural bases of these interactions remain unclear. Here, we use the GABAB receptor heterodimer as a model as it forms large complexes in the brain. It is subjected to genetic mutations mainly affecting transmembrane 6 (TM6) and involved in human diseases. By cross-linking, we identify the transmembrane interfaces involved in GABAB1-GABAB2, as well as GABAB1-GABAB1 interactions. Our data are consistent with an oligomer made of a row of GABAB1. We bring evidence that agonist activation induces a concerted rearrangement of the various interfaces. While the GB1-GB2 interface is proposed to involve TM5 in the inactive state, cross-linking of TM6s lead to constitutive activity. These data bring insight for our understanding of the allosteric interaction between GPCRs within oligomers. G protein-coupled receptors (GPCRs), such as GABAB, can integrate extracellular signals via allosteric interactions within dimers and oligomers. Here authors use crosslinking and identify two transmembrane interfaces in GABAB which undergo a concerted rearrangement upon agonist activation.
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Affiliation(s)
- Li Xue
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China
| | - Qian Sun
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China
| | - Han Zhao
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China
| | - Xavier Rovira
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, 34094 Montpellier cedex 05, France.,Molecular Photopharmacology Research Group, The Tissue Repair and Regeneration Laboratory, University of Vic - Central University of Catalonia, C. de la Laura, 13, Vic, 08500, Spain
| | - Siyu Gai
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China
| | - Qianwen He
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, 34094 Montpellier cedex 05, France.
| | - Jianfeng Liu
- Cellular Signaling laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, and College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, Hubei, China.
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, 34094 Montpellier cedex 05, France
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8
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KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABAB Receptor-Induced K+ Currents. J Neurosci 2016; 37:1162-1175. [PMID: 28003345 DOI: 10.1523/jneurosci.2181-16.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 11/29/2016] [Accepted: 12/12/2016] [Indexed: 11/21/2022] Open
Abstract
GABAB receptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, GABA. GABAB receptors were shown to associate with homo-oligomers of auxiliary KCTD8, KCTD12, KCTD12b, and KCTD16 subunits (named after their T1 K+-channel tetramerization domain) that regulate G-protein signaling of the receptor. Here we provide evidence that GABAB receptors also associate with hetero-oligomers of KCTD subunits. Coimmunoprecipitation experiments indicate that two-thirds of the KCTD16 proteins in the hippocampus of adult mice associate with KCTD12. We show that the KCTD proteins hetero-oligomerize through self-interacting T1 and H1 homology domains. Bioluminescence resonance energy transfer measurements in live cells reveal that KCTD12/KCTD16 hetero-oligomers associate with both the receptor and the G-protein. Electrophysiological experiments demonstrate that KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties on G-protein-activated Kir3 currents. During prolonged receptor activation (one min) KCTD12/KCTD16 hetero-oligomers produce moderately desensitizing fast deactivating K+ currents, whereas KCTD12 and KCTD16 homo-oligomers produce strongly desensitizing fast deactivating currents and nondesensitizing slowly deactivating currents, respectively. During short activation (2 s) KCTD12/KCTD16 hetero-oligomers produce nondesensitizing slowly deactivating currents. Electrophysiological recordings from hippocampal neurons of KCTD knock-out mice are consistent with these findings and indicate that KCTD12/KCTD16 hetero-oligomers increase the duration of slow IPSCs. In summary, our data demonstrate that simultaneous assembly of distinct KCTDs at the receptor increases the molecular and functional repertoire of native GABAB receptors and modulates physiologically induced K+ current responses in the hippocampus. SIGNIFICANCE STATEMENT The KCTD proteins 8, 12, and 16 are auxiliary subunits of GABAB receptors that differentially regulate G-protein signaling of the receptor. The KCTD proteins are generally assumed to function as homo-oligomers. Here we show that the KCTD proteins also assemble hetero-oligomers in all possible dual combinations. Experiments in live cells demonstrate that KCTD hetero-oligomers form at least tetramers and that these tetramers directly interact with the receptor and the G-protein. KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties to GABAB receptor-induced Kir3 currents in heterologous cells. KCTD12/KCTD16 hetero-oligomers are abundant in the hippocampus, where they prolong the duration of slow IPSCs in pyramidal cells. Our data therefore support that KCTD hetero-oligomers modulate physiologically induced K+ current responses in the brain.
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9
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Romaus-Sanjurjo D, Fernández-López B, Sobrido-Cameán D, Barreiro-Iglesias A, Rodicio MC. Cloning of the GABA B Receptor Subunits B1 and B2 and their Expression in the Central Nervous System of the Adult Sea Lamprey. Front Neuroanat 2016; 10:118. [PMID: 28008311 PMCID: PMC5143684 DOI: 10.3389/fnana.2016.00118] [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: 08/12/2016] [Accepted: 11/22/2016] [Indexed: 11/25/2022] Open
Abstract
In vertebrates, γ-aminobutyric acid (GABA) is the main inhibitory transmitter in the central nervous system (CNS) acting through ionotropic (GABAA) and metabotropic (GABAB) receptors. The GABAB receptor produces a slow inhibition since it activates second messenger systems through the binding and activation of guanine nucleotide-binding proteins [G-protein-coupled receptors (GPCRs)]. Lampreys are a key reference to understand molecular evolution in vertebrates. The importance of the GABAB receptor for the modulation of the circuits controlling locomotion and other behaviors has been shown in pharmacological/physiological studies in lampreys. However, there is no data about the sequence of the GABAB subunits or their expression in the CNS of lampreys. Our aim was to identify the sea lamprey GABAB1 and GABAB2 transcripts and study their expression in the CNS of adults. We cloned two partial sequences corresponding to the GABAB1 and GABAB2 cDNAs of the sea lamprey as confirmed by sequence analysis and comparison with known GABAB sequences of other vertebrates. In phylogenetic analyses, the sea lamprey GABAB sequences clustered together with GABABs sequences of vertebrates and emerged as an outgroup to all gnathostome sequences. We observed a broad and overlapping expression of both transcripts in the entire CNS. Expression was mainly observed in neuronal somas of the periventricular regions including the identified reticulospinal cells. No expression was observed in identifiable fibers. Comparison of our results with those reported in other vertebrates indicates that a broad and overlapping expression of the GABAB subunits in the CNS is a conserved character shared by agnathans and gnathostomes.
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Affiliation(s)
- Daniel Romaus-Sanjurjo
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela Santiago de Compostela, Spain
| | - Blanca Fernández-López
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela Santiago de Compostela, Spain
| | - Daniel Sobrido-Cameán
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela Santiago de Compostela, Spain
| | - Antón Barreiro-Iglesias
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela Santiago de Compostela, Spain
| | - María Celina Rodicio
- Department of Functional Biology, CIBUS, Faculty of Biology, Universidade de Santiago de Compostela Santiago de Compostela, Spain
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10
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Doly S, Shirvani H, Gäta G, Meye F, Emerit MB, Enslen H, Achour L, Pardo-Lopez L, Kwon YS, Armand V, Gardette R, Giros B, Gassmann M, Bettler B, Mameli M, Darmon M, Marullo S. GABAB receptor cell-surface export is controlled by an endoplasmic reticulum gatekeeper. Mol Psychiatry 2016; 21:480-90. [PMID: 26033241 PMCID: PMC4828513 DOI: 10.1038/mp.2015.72] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 04/24/2015] [Accepted: 04/28/2015] [Indexed: 12/20/2022]
Abstract
Endoplasmic reticulum (ER) release and cell-surface export of many G protein-coupled receptors (GPCRs) are tightly regulated. For gamma-aminobutyric acid (GABA)B receptors of GABA, the major mammalian inhibitory neurotransmitter, the ligand-binding GB1 subunit is maintained in the ER by unknown mechanisms in the absence of hetero-dimerization with the GB2 subunit. We report that GB1 retention is regulated by a specific gatekeeper, PRAF2. This ER resident transmembrane protein binds to GB1, preventing its progression in the biosynthetic pathway. GB1 release occurs upon competitive displacement from PRAF2 by GB2. PRAF2 concentration, relative to that of GB1 and GB2, tightly controls cell-surface receptor density and controls GABAB function in neurons. Experimental perturbation of PRAF2 levels in vivo caused marked hyperactivity disorders in mice. These data reveal an unanticipated major impact of specific ER gatekeepers on GPCR function and identify PRAF2 as a new molecular target with therapeutic potential for psychiatric and neurological diseases involving GABAB function.
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Affiliation(s)
- Stéphane Doly
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Hamasseh Shirvani
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Gabriel Gäta
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Frank Meye
- Institut du Fer à Moulin
Université Pierre et Marie Curie - Paris 6INSERM17 Rue du fer à moulin 75005 Paris
| | - Michel-Boris Emerit
- CPN, Centre de Psychiatrie et Neurosciences
INSERMUniversité Paris Descartes - Paris 5Groupe Hospitalier BrocaSite Broca - Sainte Anne 2 ter Rue d'Alésia75014 Paris
| | - Hervé Enslen
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Lamia Achour
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Liliana Pardo-Lopez
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Yang Seung Kwon
- CPN, Centre de Psychiatrie et Neurosciences
INSERMUniversité Paris Descartes - Paris 5Groupe Hospitalier BrocaSite Broca - Sainte Anne 2 ter Rue d'Alésia75014 Paris
| | - Vincent Armand
- CPN, Centre de Psychiatrie et Neurosciences
INSERMUniversité Paris Descartes - Paris 5Groupe Hospitalier BrocaSite Broca - Sainte Anne 2 ter Rue d'Alésia75014 Paris
| | - Robert Gardette
- CPN, Centre de Psychiatrie et Neurosciences
INSERMUniversité Paris Descartes - Paris 5Groupe Hospitalier BrocaSite Broca - Sainte Anne 2 ter Rue d'Alésia75014 Paris
| | - Bruno Giros
- Physiopathologie des Maladies du Système Nerveux Central
Université Pierre et Marie Curie - Paris 6INSERMCentre National de la Recherche ScientifiqueBâtiment B, 4ème étage, case courrier 37 9 Quai Saint Bernard 75252 Paris Cedex 05
- Service Psychiatrie
McGill University [Montréal]Institut Universitaire en Santé Mentale Douglas6875 Boulevard Lasalle, Montréal, QC H4H 1R2
| | - Martin Gassmann
- Department of Biomedicine
University of Basel Petersplatz 1, 4003 Basel
| | - Bernhard Bettler
- Department of Biomedicine
University of Basel Petersplatz 1, 4003 Basel
| | - Manuel Mameli
- Institut du Fer à Moulin
Université Pierre et Marie Curie - Paris 6INSERM17 Rue du fer à moulin 75005 Paris
| | - Michèle Darmon
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
| | - Stefano Marullo
- Institut Cochin
INSERMCentre National de la Recherche ScientifiqueUniversité Paris Descartes - Paris 5Institut National de la Recherche Agronomique (INRA)Université de Versailles Saint-Quentin-en-Yvelines22 Rue Méchain, 75014 Paris
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11
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Lahaie N, Kralikova M, Prézeau L, Blahos J, Bouvier M. Post-endocytotic Deubiquitination and Degradation of the Metabotropic γ-Aminobutyric Acid Receptor by the Ubiquitin-specific Protease 14. J Biol Chem 2016; 291:7156-70. [PMID: 26817839 DOI: 10.1074/jbc.m115.686907] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Indexed: 02/01/2023] Open
Abstract
Mechanisms controlling the metabotropic γ-aminobutyric acid receptor (GABAB) cell surface stability are still poorly understood. In contrast with many other G protein-coupled receptors (GPCR), it is not subject to agonist-promoted internalization, but is constitutively internalized and rapidly down-regulated. In search of novel interacting proteins regulating receptor fate, we report that the ubiquitin-specific protease 14 (USP14) interacts with the GABAB(1b)subunit's second intracellular loop. Probing the receptor for ubiquitination using bioluminescence resonance energy transfer (BRET), we detected a constitutive and phorbol 12-myristate 13-acetate (PMA)-induced ubiquitination of the receptor at the cell surface. PMA also increased internalization and accelerated receptor degradation. Overexpression of USP14 decreased ubiquitination while treatment with a small molecule inhibitor of the deubiquitinase (IU1) increased receptor ubiquitination. Treatment with the internalization inhibitor Dynasore blunted both USP14 and IU1 effects on the receptor ubiquitination state, suggesting a post-endocytic site of action. Overexpression of USP14 also led to an accelerated degradation of GABABin a catalytically independent fashion. We thus propose a model whereby cell surface ubiquitination precedes endocytosis, after which USP14 acts as an ubiquitin-binding protein that targets the ubiquitinated receptor to lysosomal degradation and promotes its deubiquitination.
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Affiliation(s)
- Nicolas Lahaie
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Michaela Kralikova
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Laurent Prézeau
- Institut de Génomique Fonctionnelle, Université de Montpellier 1 and 2, 34090 Montpellier, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Michel Bouvier
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada,
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12
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Fève M, Saliou JM, Zeniou M, Lennon S, Carapito C, Dong J, Van Dorsselaer A, Junier MP, Chneiweiss H, Cianférani S, Haiech J, Kilhoffer MC. Comparative expression study of the endo-G protein coupled receptor (GPCR) repertoire in human glioblastoma cancer stem-like cells, U87-MG cells and non malignant cells of neural origin unveils new potential therapeutic targets. PLoS One 2014; 9:e91519. [PMID: 24662753 PMCID: PMC3963860 DOI: 10.1371/journal.pone.0091519] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Accepted: 02/10/2014] [Indexed: 12/22/2022] Open
Abstract
Glioblastomas (GBMs) are highly aggressive, invasive brain tumors with bad prognosis and unmet medical need. These tumors are heterogeneous being constituted by a variety of cells in different states of differentiation. Among these, cells endowed with stem properties, tumor initiating/propagating properties and particularly resistant to chemo- and radiotherapies are designed as the real culprits for tumor maintenance and relapse after treatment. These cells, termed cancer stem-like cells, have been designed as prominent targets for new and more efficient cancer therapies. G-protein coupled receptors (GPCRs), a family of membrane receptors, play a prominent role in cell signaling, cell communication and crosstalk with the microenvironment. Their role in cancer has been highlighted but remains largely unexplored. Here, we report a descriptive study of the differential expression of the endo-GPCR repertoire in human glioblastoma cancer stem-like cells (GSCs), U-87 MG cells, human astrocytes and fetal neural stem cells (f-NSCs). The endo-GPCR transcriptome has been studied using Taqman Low Density Arrays. Of the 356 GPCRs investigated, 138 were retained for comparative studies between the different cell types. At the transcriptomic level, eight GPCRs were specifically expressed/overexpressed in GSCs. Seventeen GPCRs appeared specifically expressed in cells with stem properties (GSCs and f-NSCs). Results of GPCR expression at the protein level using mass spectrometry and proteomic analysis are also presented. The comparative GPCR expression study presented here gives clues for new pathways specifically used by GSCs and unveils novel potential therapeutic targets.
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Affiliation(s)
- Marie Fève
- Laboratoire d'Innovation Thérapeutique, UMR7200, Laboratoire d'Excellence Medalis, CNRS, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Jean-Michel Saliou
- Laboratoire de Spectrométrie de Masse BioOrganique, UMR7178, CNRS, Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Strasbourg, France
| | - Maria Zeniou
- Laboratoire d'Innovation Thérapeutique, UMR7200, Laboratoire d'Excellence Medalis, CNRS, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Sarah Lennon
- Laboratoire de Spectrométrie de Masse BioOrganique, UMR7178, CNRS, Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Strasbourg, France
| | - Christine Carapito
- Laboratoire de Spectrométrie de Masse BioOrganique, UMR7178, CNRS, Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Strasbourg, France
| | - Jihu Dong
- Laboratoire d'Innovation Thérapeutique, UMR7200, Laboratoire d'Excellence Medalis, CNRS, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Alain Van Dorsselaer
- Laboratoire de Spectrométrie de Masse BioOrganique, UMR7178, CNRS, Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Strasbourg, France
| | - Marie-Pierre Junier
- Neuroscience Paris Seine, UMR8246, Inserm U1130, Institut de Biologie Paris Seine, CNRS, Université Pierre et Marie Curie, Paris, France
| | - Hervé Chneiweiss
- Neuroscience Paris Seine, UMR8246, Inserm U1130, Institut de Biologie Paris Seine, CNRS, Université Pierre et Marie Curie, Paris, France
| | - Sarah Cianférani
- Laboratoire de Spectrométrie de Masse BioOrganique, UMR7178, CNRS, Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Strasbourg, France
| | - Jacques Haiech
- Laboratoire d'Innovation Thérapeutique, UMR7200, Laboratoire d'Excellence Medalis, CNRS, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
| | - Marie-Claude Kilhoffer
- Laboratoire d'Innovation Thérapeutique, UMR7200, Laboratoire d'Excellence Medalis, CNRS, Université de Strasbourg, Faculté de Pharmacie, Illkirch, France
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13
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Ivankova K, Turecek R, Fritzius T, Seddik R, Prezeau L, Comps-Agrar L, Pin JP, Fakler B, Besseyrias V, Gassmann M, Bettler B. Up-regulation of GABA(B) receptor signaling by constitutive assembly with the K+ channel tetramerization domain-containing protein 12 (KCTD12). J Biol Chem 2013; 288:24848-56. [PMID: 23843457 PMCID: PMC3750179 DOI: 10.1074/jbc.m113.476770] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
GABAB receptors are the G-protein coupled receptors (GPCRs) for GABA, the main inhibitory neurotransmitter in the central nervous system. Native GABAB receptors comprise principle and auxiliary subunits that regulate receptor properties in distinct ways. The principle subunits GABAB1a, GABAB1b, and GABAB2 form fully functional heteromeric GABAB(1a,2) and GABAB(1b,2) receptors. Principal subunits regulate forward trafficking of the receptors from the endoplasmic reticulum to the plasma membrane and control receptor distribution to axons and dendrites. The auxiliary subunits KCTD8, -12, -12b, and -16 are cytosolic proteins that influence agonist potency and G-protein signaling of GABAB(1a,2) and GABAB(1b,2) receptors. Here, we used transfected cells to study assembly, surface trafficking, and internalization of GABAB receptors in the presence of the KCTD12 subunit. Using bimolecular fluorescence complementation and metabolic labeling, we show that GABAB receptors associate with KCTD12 while they reside in the endoplasmic reticulum. Glycosylation experiments support that association with KCTD12 does not influence maturation of the receptor complex. Immunoprecipitation and bioluminescence resonance energy transfer experiments demonstrate that KCTD12 remains associated with the receptor during receptor activity and receptor internalization from the cell surface. We further show that KCTD12 reduces constitutive receptor internalization and thereby increases the magnitude of receptor signaling at the cell surface. Accordingly, knock-out or knockdown of KCTD12 in cultured hippocampal neurons reduces the magnitude of the GABAB receptor-mediated K+ current response. In summary, our experiments support that the up-regulation of functional GABAB receptors at the neuronal plasma membrane is an additional physiological role of the auxiliary subunit KCTD12.
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Affiliation(s)
- Klara Ivankova
- Department of Biomedicine, University of Basel, CH-4056 Basel, Switzerland
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14
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Lam VM, Beerepoot P, Angers S, Salahpour A. A Novel Assay for Measurement of Membrane-Protein Surface Expression using a β-lactamase Reporter. Traffic 2013; 14:778-84. [DOI: 10.1111/tra.12073] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Revised: 04/04/2013] [Accepted: 04/09/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Vincent M. Lam
- Department of Pharmacology and Toxicology; University of Toronto; Toronto; Ontario,; Canada
| | - Pieter Beerepoot
- Department of Pharmacology and Toxicology; University of Toronto; Toronto; Ontario,; Canada
| | - Stephane Angers
- Leslie Dan Faculty of Pharmacy; University of Toronto; Toronto; Ontario,; Canada
| | - Ali Salahpour
- Department of Pharmacology and Toxicology; University of Toronto; Toronto; Ontario,; Canada
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15
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Valdés V, Valenzuela JI, Salas DA, Jaureguiberry-Bravo M, Otero C, Thiede C, Schmidt CF, Couve A. Endoplasmic reticulum sorting and kinesin-1 command the targeting of axonal GABAB receptors. PLoS One 2012; 7:e44168. [PMID: 22952914 PMCID: PMC3428321 DOI: 10.1371/journal.pone.0044168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 07/30/2012] [Indexed: 12/17/2022] Open
Abstract
In neuronal cells the intracellular trafficking machinery controls the availability of neurotransmitter receptors at the plasma membrane, which is a critical determinant of synaptic strength. Metabotropic γ amino-butyric acid (GABA) type B receptors (GABABRs) are neurotransmitter receptors that modulate synaptic transmission by mediating the slow and prolonged responses to GABA. GABABRs are obligatory heteromers constituted by two subunits, GABABR1 and GABABR2. GABABR1a and GABABR1b are the most abundant subunit variants. GABABR1b is located in the somatodendritic domain whereas GABABR1a is additionally targeted to the axon. Sushi domains located at the N-terminus of GABABR1a constitute the only difference between both variants and are necessary and sufficient for axonal targeting. The precise targeting machinery and the organelles involved in sorting and transport have not been described. Here we demonstrate that GABABRs require the Golgi apparatus for plasma membrane delivery but that axonal sorting and targeting of GABABR1a operate in a pre-Golgi compartment. In the axon GABABR1a subunits are enriched in the endoplasmic reticulum (ER), and their dynamic behavior and colocalization with other secretory organelles like the ER-to-Golgi intermediate compartment (ERGIC) suggest that they employ a local secretory route. The transport of axonal GABABR1a is microtubule-dependent and kinesin-1, a molecular motor of the kinesin family, determines axonal localization. Considering that progression of GABABRs through the secretory pathway is regulated by an ER retention motif our data contribute to understand the role of the axonal ER in non-canonical sorting and targeting of neurotransmitter receptors.
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Affiliation(s)
- Viviana Valdés
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - José Ignacio Valenzuela
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Daniela A. Salas
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Matías Jaureguiberry-Bravo
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- School of Biochemistry, Faculty of Biological Science, Universidad Andrés Bello, Santiago, Chile
| | - Carolina Otero
- Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christina Thiede
- Georg-August-Universität, Fakultät für Physik, Drittes Physikalisches Institut-Biophysik, Göttingen, Germany
| | - Christoph F. Schmidt
- Georg-August-Universität, Fakultät für Physik, Drittes Physikalisches Institut-Biophysik, Göttingen, Germany
| | - Andrés Couve
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- * E-mail:
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16
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Presynaptic GABA(B) receptors decrease neurotransmitter release in vestibular nuclei neurons during vestibular compensation. Neuroscience 2012; 223:333-54. [PMID: 22871524 DOI: 10.1016/j.neuroscience.2012.07.061] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/18/2012] [Accepted: 07/30/2012] [Indexed: 01/25/2023]
Abstract
Unilateral damage to the peripheral vestibular receptors precipitates a debilitating syndrome of oculomotor and balance deficits at rest, which extensively normalize during the first week after the lesion due to vestibular compensation. In vivo studies suggest that GABA(B) receptor activation facilitates recovery. However, the presynaptic or postsynaptic sites of action of GABA(B) receptors in vestibular nuclei neurons after lesions have not been determined. Accordingly, here presynaptic and postsynaptic GABA(B) receptor activity in principal cells of the tangential nucleus, a major avian vestibular nucleus, was investigated using patch-clamp recordings correlated with immunolabeling and confocal imaging of the GABA(B) receptor subunit-2 (GABA(B)R2) in controls and operated chickens shortly after unilateral vestibular ganglionectomy (UVG). Baclofen, a GABA(B) agonist, generated no postsynaptic currents in principal cells in controls, which correlated with weak GABA(B)R2 immunolabeling on principal cell surfaces. However, baclofen decreased miniature excitatory postsynaptic current (mEPSC) and GABAergic miniature inhibitory postsynaptic current (mIPSC) events in principal cells in controls, compensating and uncompensated chickens three days after UVG, indicating the presence of functional GABA(B) receptors on presynaptic terminals. Baclofen decreased GABAergic mIPSC frequency to the greatest extent in principal cells on the intact side of compensating chickens, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 2-labeled terminals. In uncompensated chickens, baclofen decreased mEPSC frequency to the greatest extent in principal cells on the intact side, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 1-labeled terminals. Altogether, these results revealed changes in presynaptic GABA(B) receptor function and expression which differed in compensating and uncompensated chickens shortly after UVG. This work supports an important role for GABA(B) autoreceptor-mediated inhibition in vestibular nuclei neurons on the intact side during early stages of vestibular compensation, and a role for GABA(B) heteroreceptor-mediated inhibition of glutamatergic terminals on the intact side in the failure to recover function.
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17
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Sushi domains confer distinct trafficking profiles on GABAB receptors. Proc Natl Acad Sci U S A 2012; 109:12171-6. [PMID: 22778417 DOI: 10.1073/pnas.1201660109] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
GABA(B) receptors mediate slow inhibitory neurotransmission in the brain and feature during excitatory synaptic plasticity, as well as various neurological conditions. These receptors are obligate heterodimers composed of GABA(B)R1 and R2 subunits. The two predominant R1 isoforms differ by the presence of two complement control protein modules or Sushi domains (SDs) in the N terminus of R1a. By using live imaging, with an α-bungarotoxin-binding site (BBS) and fluorophore-linked bungarotoxin, we studied how R2 stabilizes R1b subunits at the cell surface. Heterodimerization with R2 reduced the rate of internalization of R1b, compared with R1b homomers. However, R1aR2 heteromers exhibited increased cell surface stability compared with R1bR2 receptors in hippocampal neurons, suggesting that for receptors containing the R1a subunit, the SDs play an additional role in the surface stability of GABA(B) receptors. Both SDs were necessary to increase the stability of R1aR2 because single deletions caused the receptors to be internalized at the same rate and extent as R1bR2 receptors. Consistent with these findings, a chimera formed from the metabotropic glutamate receptor (mGluR)2 and the SDs from R1a increased the surface stability of mGluR2. These results suggest a role for SDs in stabilizing cell surface receptors that could impart different pre- and postsynaptic trafficking itineraries on GABA(B) receptors, thereby contributing to their physiological and pathological roles.
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18
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Baloucoune GA, Chun L, Zhang W, Xu C, Huang S, Sun Q, Wang Y, Tu H, Liu J. GABAB receptor subunit GB1 at the cell surface independently activates ERK1/2 through IGF-1R transactivation. PLoS One 2012; 7:e39698. [PMID: 22761875 PMCID: PMC3386256 DOI: 10.1371/journal.pone.0039698] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 05/29/2012] [Indexed: 12/24/2022] Open
Abstract
Background Functional GABAB receptor is believed to require hetero-dimerization between GABAB1 (GB1) and GABAB2 (GB2) subunits. The GB1 extracellular domain is required for ligand binding, and the GB2 trans-membrane domain is responsible for coupling to G proteins. Atypical GABAB receptor responses observed in GB2-deficient mice suggested that GB1 may have activity in the absence of GB2. However the underlying mechanisms remain poorly characterized. Methodology/Principal Findings Here, by using cells overexpressing a GB1 mutant (GB1asa) with the ability to translocate to the cell surface in the absence of GB2, we show that GABAB receptor agonists, such as GABA and Baclofen, can induce ERK1/2 phosphorylation in the absence of GB2. Furthermore, we demonstrate that GB1asa induces ERK1/2 phosphorylation through Gi/o proteins and PLC dependent IGF-1R transactivation. Conclusions/Significance Our data suggest that GB1 may form a functional receptor at the cell surface in the absence of GB2.
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Affiliation(s)
- Guillaume A. Baloucoune
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Lei Chun
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Wenhua Zhang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Chanjuan Xu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Siluo Huang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Qian Sun
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yunyun Wang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Haijun Tu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jianfeng Liu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- * E-mail:
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19
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Leskelä TT, Lackman JJ, Vierimaa MM, Kobayashi H, Bouvier M, Petäjä-Repo UE. Cys-27 variant of human δ-opioid receptor modulates maturation and cell surface delivery of Phe-27 variant via heteromerization. J Biol Chem 2011; 287:5008-20. [PMID: 22184124 DOI: 10.1074/jbc.m111.305656] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The important role of G protein-coupled receptor homo/heteromerization in receptor folding, maturation, trafficking, and cell surface expression has become increasingly evident. Here we investigated whether the human δ-opioid receptor (hδOR) Cys-27 variant that shows inherent compromised maturation has an effect on the behavior of the more common Phe-27 variant in the early secretory pathway. We demonstrate that hδOR-Cys-27 acts in a dominant negative manner and impairs cell surface delivery of the co-expressed hδOR-Phe-27 and impairs conversion of precursors to the mature form. This was demonstrated by metabolic labeling, Western blotting, flow cytometry, and confocal microscopy in HEK293 and human SH-SY5Y neuroblastoma cells using differentially epitope-tagged variants. The hδOR-Phe-27 precursors that were redirected to the endoplasmic reticulum-associated degradation were, however, rescued by a pharmacological chaperone, the opioid antagonist naltrexone. Co-immunoprecipitation of metabolically labeled variants revealed that both endoplasmic reticulum-localized precursors and mature receptors exist as homo/heteromers. The existence of homo/heteromers was confirmed in living cells by bioluminescence resonance energy transfer measurements, showing that the variants have a similar propensity to form homo/heteromers. By forming both homomers and heteromers, the hδOR-Cys-27 variant may thus regulate the levels of receptors at the cell surface, possibly leading to altered responsiveness to opioid ligands in individuals carrying the Cys-27 variant.
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Affiliation(s)
- Tarja T Leskelä
- Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, FI-90014 Oulu, Finland
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20
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Hannan S, Wilkins ME, Dehghani-Tafti E, Thomas P, Baddeley SM, Smart TG. Gamma-aminobutyric acid type B (GABA(B)) receptor internalization is regulated by the R2 subunit. J Biol Chem 2011; 286:24324-35. [PMID: 21724853 PMCID: PMC3129212 DOI: 10.1074/jbc.m110.220814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 04/20/2011] [Indexed: 01/04/2023] Open
Abstract
γ-Aminobutyric acid type B (GABA(B)) receptors are important for slow synaptic inhibition in the CNS. The efficacy of inhibition is directly related to the stability of cell surface receptors. For GABA(B) receptors, heterodimerization between R1 and R2 subunits is critical for cell surface expression and signaling, but how this determines the rate and extent of receptor internalization is unknown. Here, we insert a high affinity α-bungarotoxin binding site into the N terminus of the R2 subunit and reveal its dominant role in regulating the internalization of GABA(B) receptors in live cells. To simultaneously study R1a and R2 trafficking, a new α-bungarotoxin binding site-labeling technique was used, allowing α-bungarotoxin conjugated to different fluorophores to selectively label R1a and R2 subunits. This approach demonstrated that R1a and R2 are internalized as dimers. In heterologous expression systems and neurons, the rates and extents of internalization for R1aR2 heteromers and R2 homomers are similar, suggesting a regulatory role for R2 in determining cell surface receptor stability. The fast internalization rate of R1a, which has been engineered to exit the endoplasmic reticulum, was slowed to that of R2 by truncating the R1a C-terminal tail or by removing a dileucine motif in its coiled-coil domain. Slowing the rate of internalization by co-assembly with R2 represents a novel role for GPCR heterodimerization whereby R2 subunits, via their C terminus coiled-coil domain, mask a dileucine motif on R1a subunits to determine the surface stability of the GABA(B) receptor.
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Affiliation(s)
- Saad Hannan
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
- GlaxoSmithKline R&D, Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Megan E. Wilkins
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Ebrahim Dehghani-Tafti
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Philip Thomas
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
| | - Stuart M. Baddeley
- GlaxoSmithKline R&D, Medicines Research Centre, Gunnels Wood Road, Stevenage SG1 2NY, United Kingdom
| | - Trevor G. Smart
- From the Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom and
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21
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Hannan S, Wilkins ME, Dehghani-Tafti E, Thomas P, Baddeley SM, Smart TG. γ-Aminobutyric Acid Type B (GABAB) Receptor Internalization Is Regulated by the R2 Subunit. J Biol Chem 2011. [DOI: 10.1074/jbc.m111.220814] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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22
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Breton B, Lagacé M, Bouvier M. Combining resonance energy transfer methods reveals a complex between the α 2A‐adrenergic receptor, Gα i1β 1γ 2, and GRK2. FASEB J 2010. [DOI: 10.1096/fj.10.164061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Billy Breton
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
| | - Monique Lagacé
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
| | - Michel Bouvier
- Department of BiochemistryInstitute for Research in Immunology and CancerGroupe de Recherche Universitaire sur le MédicamentUniversité de Montréal Montréal Québec Canada
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23
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Ciruela F, Fernández-Dueñas V, Sahlholm K, Fernández-Alacid L, Nicolau JC, Watanabe M, Luján R. Evidence for oligomerization between GABAB receptors and GIRK channels containing the GIRK1 and GIRK3 subunits. Eur J Neurosci 2010; 32:1265-77. [PMID: 20846323 DOI: 10.1111/j.1460-9568.2010.07356.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The stimulation of inhibitory neurotransmitter receptors, such as γ-aminobutyric acid type B (GABA(B) ) receptors, activates G protein-gated inwardly-rectifying K(+) (GIRK) channels, which influence membrane excitability. There is now evidence suggesting that G protein-coupled receptors and G protein-gated inwardly-rectifying K(+) [GIRK/family 3 of inwardly-rectifying K(+) (Kir3)] channels do not diffuse freely within the plasma membrane, but instead there are direct protein-protein interactions between them. Here, we used bioluminescence resonance energy transfer, co-immunoprecipitation, confocal and electron microscopy techniques to investigate the oligomerization of GABA(B) receptors with GIRK channels containing the GIRK3 subunit, whose contribution to functional channels is still unresolved. Co-expression of GABA(B) receptors and GIRK channels in human embryonic kidney-293 cells in combination with co-immunoprecipitation experiments established that the metabotropic receptor forms stable complexes with GIRK channels. Using bioluminescence resonance energy transfer, we have shown that, in living cells under physiological conditions, GABA(B) receptors interact directly with GIRK1/GIRK3 heterotetramers. In addition, we have provided evidence that the receptor-effector complexes are also found in vivo and identified that the cerebellar granule cells are one neuron population where the interaction probably takes place. Altogether, our data show that signalling complexes containing GABA(B) receptors and GIRK channels are formed shortly after biosynthesis, probably in the endoplasmic reticulum and/or endoplasmic reticulum/Golgi apparatus complex, suggesting that this might be a general feature of receptor-effector ion channel signal transduction and supporting a channel-forming role for the GIRK3 subunit.
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Affiliation(s)
- Francisco Ciruela
- Unitat de Farmacologia (4102), Departament Patologia i Terapèutica Experimental, Facultat de Medicina-Bellvitge, Universitat de IDIBELL-Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain.
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24
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Breton B, Lagacé M, Bouvier M. Combining resonance energy transfer methods reveals a complex between the alpha2A-adrenergic receptor, Galphai1beta1gamma2, and GRK2. FASEB J 2010; 24:4733-43. [PMID: 20696855 DOI: 10.1096/fj.10-164061] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Traditionally, G-protein-coupled receptor (GPCR) interactions with their G proteins and regulatory proteins, GPCR kinases (GRKs) and arrestins, are described as sequential events involving rapid assemblies/disassemblies. To directly monitor the dynamics of these interactions in living cells, we combined two spectrally resolved bioluminescence and one fluorescence resonance energy transfer (RET) methods. The RET combination analysis revealed that stimulation of the α(2A)-adrenergic receptor (α(2A)AR) leads to the recruitment of GRK2 at a receptor still associated with the Gα(i1)β(1)γ(2) complex. The interaction kinetics of GRKs with Gγ(2) (2.8 ± 0.4 s) and α(2A)AR (5.2 ± 0.5 s) were similar to that of the receptor-promoted change in RET between Gα(i1) and Gγ(2) (5.2 ± 1.2 s), and persisted until the translocation of βarrestin2 to the receptor, indicating that GRK2 remains associated to the receptor/G-protein complex for longer periods than anticipated. Moreover, GRK2 or a kinase-deficient GRK2 mutant, but not GRK5, potentiated the receptor-promoted changes in RET between Gα(i1) and Gγ(2) and abrogated the α(2A)AR-stimulated calcium response, suggesting that the recruitment of GRK2 to the complex contributes to the structural rearrangement and functional regulation of the signaling unit, independently of the kinase activity. RET combination analysis revealed unanticipated dynamics in GPCR signaling and will be applicable to many biological systems.
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Affiliation(s)
- Billy Breton
- Department of Biochemistry, Institute for Research in Immunology and Cancer, and Groupe de Recherche Universitaire sur le Médicament, Université de Montréal, Montréal, Québec, Canada
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25
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Galanopoulou AS. Mutations affecting GABAergic signaling in seizures and epilepsy. Pflugers Arch 2010; 460:505-23. [PMID: 20352446 DOI: 10.1007/s00424-010-0816-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 02/18/2010] [Accepted: 02/23/2010] [Indexed: 02/02/2023]
Abstract
The causes of epilepsies and epileptic seizures are multifactorial. Genetic predisposition may contribute in certain types of epilepsies and seizures, whether idiopathic or symptomatic of genetic origin. Although these are not very common, they have offered a unique opportunity to investigate the molecular mechanisms underlying epileptogenesis and ictogenesis. Among the implicated gene mutations, a number of GABAA receptor subunit mutations have been recently identified that contribute to several idiopathic epilepsies, febrile seizures, and rarely to certain types of symptomatic epilepsies, like the severe myoclonic epilepsy of infancy. Deletion of GABAA receptor genes has also been linked to Angelman syndrome. Furthermore, mutations of proteins controlling chloride homeostasis, which indirectly defines the functional consequences of GABAA signaling, have been identified. These include the chloride channel 2 (CLCN2) and the potassium chloride cotransporter KCC3. The pathogenic role of CLCN2 mutations has not been clearly demonstrated and may represent either susceptibility genes or, in certain cases, innocuous polymorphisms. KCC3 mutations have been associated with hereditary motor and sensory polyneuropathy with corpus callosum agenesis (Andermann syndrome) that often manifests with epileptic seizures. This review summarizes the recent progress in the genetic linkages of epilepsies and seizures to the above genes and discusses potential pathogenic mechanisms that contribute to the age, sex, and conditional expression of these seizures in carriers of these mutations.
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Affiliation(s)
- Aristea S Galanopoulou
- Saul R. Korey Department of Neurology and Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Kennedy Center Room 306, Bronx, NY 10461, USA.
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26
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Ramírez OA, Vidal RL, Tello JA, Vargas KJ, Kindler S, Härtel S, Couve A. Dendritic assembly of heteromeric gamma-aminobutyric acid type B receptor subunits in hippocampal neurons. J Biol Chem 2009; 284:13077-85. [PMID: 19276079 PMCID: PMC2676040 DOI: 10.1074/jbc.m900575200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 03/09/2009] [Indexed: 01/27/2023] Open
Abstract
Understanding the mechanisms that control synaptic efficacy through the availability of neurotransmitter receptors depends on uncovering their specific intracellular trafficking routes. gamma-Aminobutyric acid type B (GABA(B)) receptors (GABA(B)Rs) are obligatory heteromers present at dendritic excitatory and inhibitory postsynaptic sites. It is unknown whether synthesis and assembly of GABA(B)Rs occur in the somatic endoplasmic reticulum (ER) followed by vesicular transport to dendrites or whether somatic synthesis is followed by independent transport of the subunits for assembly and ER export throughout the somatodendritic compartment. To discriminate between these possibilities we studied the association of GABA(B)R subunits in dendrites of hippocampal neurons combining live fluorescence microscopy, biochemistry, quantitative colocalization, and bimolecular fluorescent complementation. We demonstrate that GABA(B)R subunits are segregated and differentially mobile in dendritic intracellular compartments and that a high proportion of non-associated intracellular subunits exist in the brain. Assembled heteromers are preferentially located at the plasma membrane, but blockade of ER exit results in their intracellular accumulation in the cell body and dendrites. We propose that GABA(B)R subunits assemble in the ER and are exported from the ER throughout the neuron prior to insertion at the plasma membrane. Our results are consistent with a bulk flow of segregated subunits through the ER and rule out a post-Golgi vesicular transport of preassembled GABA(B)Rs.
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Affiliation(s)
- Omar A Ramírez
- Physiology and Biophysics, Faculty of Medicine, Universidad de Chile, Santiago, Chile
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27
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Richer M, David M, Villeneuve LR, Trieu P, Ethier N, Pétrin D, Mamarbachi AM, Hébert TE. GABA-B(1) receptors are coupled to the ERK1/2 MAP kinase pathway in the absence of GABA-B(2) subunits. J Mol Neurosci 2008; 38:67-79. [PMID: 19052921 DOI: 10.1007/s12031-008-9163-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 11/06/2008] [Indexed: 01/22/2023]
Abstract
In the current model of gamma-aminobutyric acid (GABA) B receptor function, there is a requirement for GABA-B(1/2) heterodimerisation for targetting to the cell surface. However, different lines of evidence suggest that the GABA-B(1) subunit can form a functional receptor in the absence of GABA-B(2). We observed coupling of endogenous GABA-B(1) receptors in the DI-TNC1 glial cell line to the ERK pathway in response to baclofen even though these cells do not express GABA-B(2). GABA-B(1A) receptors were also able to mediate a rapid, transient, and dose-dependent activation of the ERK1/2 MAP kinase pathway when transfected alone into HEK 293 cells. The response was abolished by G(i/o) and MEK inhibition, potentiated by inhibitors of phospholipase C and protein kinase C and did not involve PI-3-kinase activity. Finally, using bioluminescence resonance energy transfer and co-immunoprecipitation, we show the existence of homodimeric GABA-B(1A) receptors in transfected HEK293 cells. Altogether, our observations show that GABA-B(1A) receptors are able to activate the ERK1/2 pathway despite the absence of surface targetting partner GABA-B(2) in both HEK 293 cells and the DI-TNC1 cell line.
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Affiliation(s)
- Maxime Richer
- Département de biochimie and Groupe de recherche universitaire sur le médicament (GRUM), Université de Montréal, Montréal, Québec, Canada
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28
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Maurel D, Comps-Agrar L, Brock C, Rives ML, Bourrier E, Ayoub MA, Bazin H, Tinel N, Durroux T, Prézeau L, Trinquet E, Pin JP. Cell-surface protein-protein interaction analysis with time-resolved FRET and snap-tag technologies: application to GPCR oligomerization. Nat Methods 2008; 5:561-7. [PMID: 18488035 DOI: 10.1038/nmeth.1213] [Citation(s) in RCA: 377] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Accepted: 04/14/2008] [Indexed: 11/09/2022]
Abstract
Cell-surface proteins are important in cell-cell communication. They assemble into heterocomplexes that include different receptors and effectors. Elucidation and manipulation of such protein complexes offers new therapeutic possibilities. We describe a methodology combining time-resolved fluorescence resonance energy transfer (FRET) with snap-tag technology to quantitatively analyze protein-protein interactions at the surface of living cells, in a high throughput-compatible format. Using this approach, we examined whether G protein-coupled receptors (GPCRs) are monomers or assemble into dimers or larger oligomers--a matter of intense debate. We obtained evidence for the oligomeric state of both class A and class C GPCRs. We also observed different quaternary structure of GPCRs for the neurotransmitters glutamate and gamma-aminobutyric acid (GABA): whereas metabotropic glutamate receptors assembled into strict dimers, the GABA(B) receptors spontaneously formed dimers of heterodimers, offering a way to modulate G-protein coupling efficacy. This approach will be useful in systematic analysis of cell-surface protein interaction in living cells.
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Affiliation(s)
- Damien Maurel
- Centre National de la Recherche Scientifique (CNRS), UMR 5203, Institut de Génomique Fonctionnelle, 141 Rue de la Cardonille, Montpellier F-34000, France
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29
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Harrison PJ, Lyon L, Sartorius LJ, Burnet PWJ, Lane TA. The group II metabotropic glutamate receptor 3 (mGluR3, mGlu3, GRM3): expression, function and involvement in schizophrenia. J Psychopharmacol 2008; 22:308-22. [PMID: 18541626 DOI: 10.1177/0269881108089818] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Group II metabotropic glutamate receptors (mGluRs) comprise mGluR2 (mGlu2; encoded by GRM2) and mGluR3 (mGlu3; encoded by GRM3) and modulate glutamate neurotransmission and synaptic plasticity. Here we review the expression and function of mGluR3 and its involvement in schizophrenia. mGluR3 is expressed by glia and neurons in many brain regions and has a predominantly presynaptic distribution, consistent with its role as an inhibitory autoreceptor and heteroceptor. mGluR3 splice variants exist in human brain but are of unknown function. Differentiation of mGluR3 from mGluR2 has been problematic because of the lack of selective ligands and antibodies; the available data suggest particular roles for mGluR3 in long-term depression, in glial function and in neuroprotection. Some but not all studies find genetic association of GRM3 polymorphisms with psychosis, with the risk alleles also being associated with schizophrenia-related endophenotypes such as impaired cognition, cortical activation and glutamate markers. The dimeric form of mGluR3 may be reduced in the brain in schizophrenia. Finally, preclinical findings have made mGluR3 a putative therapeutic target, and now direct evidence for antipsychotic efficacy of a group II mGluR agonist has emerged from a randomised clinical trial in schizophrenia. Together these data implicate mGluR3 in aetiological, pathophysiological and pharmacotherapeutic aspects of the disorder.
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Affiliation(s)
- P J Harrison
- Department of Psychiatry, University of Oxford, Neurosciences Building, Warneford Hospital, Oxford, UK.
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30
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Remelli R, Robbins MJ, McIlhinney RAJ. The C-terminus of the metabotropic glutamate receptor 1b regulates dimerization of the receptor. J Neurochem 2008; 104:1020-31. [DOI: 10.1111/j.1471-4159.2007.05034.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Nomura R, Suzuki Y, Kakizuka A, Jingami H. Direct detection of the interaction between recombinant soluble extracellular regions in the heterodimeric metabotropic gamma-aminobutyric acid receptor. J Biol Chem 2007; 283:4665-73. [PMID: 18165688 DOI: 10.1074/jbc.m705202200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma-aminobutyric acid, type B (GABAB) receptor is a heterodimeric receptor consisting of two complementary subunits, GABAB1 receptor (GBR1) and GABAB2 receptor (GBR2). GBR1 is responsible for GABA binding, whereas GBR2 is considered to perform a critical role in signal transduction toward downstream targets. Therefore, precise communication between GBR1 and GBR2 is thought to be essential for the proper signal transduction process. However, biochemical data describing the interaction of the two subunits, especially for the extracellular regions, are not sufficient. Thus we began by developing a protein expression system of the soluble extracellular regions. One of the soluble recombinant GBR1 proteins exhibited a ligand binding ability, which is similar to that of the full-length GBR1, and thus the ligand-binding domain was determined. Direct interaction between GBR1 and GBR2 extracellular soluble fragments was confirmed by co-expression followed by affinity column chromatography and a sucrose density gradient sedimentation. In addition, we also found homo-oligomeric states of these soluble extracellular regions. The interaction between the two soluble extracellular regions caused the enhancement of the agonist affinity for GBR1 as previously reported in a cell-based assay. These results not only open the way to future structural studies but also highlight the role of the interaction between the extracellular regions, which controls agonist affinity to the heterodimeric receptor.
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Affiliation(s)
- Rei Nomura
- Department of Molecular Biology, Biomolecular Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
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32
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Abstract
In the basal ganglia the effects of gamma-aminobutyrate (GABA) are mediated by both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the existence and widespread distribution in the CNS of the GABA(B) receptor had been established in the 1980s the field of GABA(B) research was revolutionized with the discovery that two related G-protein-coupled receptors (GPCRs) needed to dimerize to form the functional GABA(B) receptor at the cell surface. This finding lead to a number of studies of oligomerization in GPCRs and detailed pharmacological studies of the cloned receptors and their splice variants. Particular interest has focused on the proteins interacting with the receptor which may be important in mediating the longer term signalling effects of the receptor and modifying its cellular localization or physiology. The cloning of the GABA(B) receptors also lead to the identification of the first compounds interacting in an allosteric fashion with the receptor some of which may have therapeutic value. Most recently "knockouts" of both the GABA(B) subunits have been produced where in general as expected there is a loss of the majority of the inhibitory effects of the GABA(B) receptor.
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Affiliation(s)
- Piers C Emson
- The Babraham Institute, Babraham Research Campus, Cambridge CB2 4AT, UK.
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33
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Kanaide M, Uezono Y, Matsumoto M, Hojo M, Ando Y, Sudo Y, Sumikawa K, Taniyama K. Desensitization of GABA(B) receptor signaling by formation of protein complexes of GABA(B2) subunit with GRK4 or GRK5. J Cell Physiol 2007; 210:237-45. [PMID: 17013811 DOI: 10.1002/jcp.20863] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We investigated the role of G protein coupled-receptor kinases (GRKs) in the desensitization of GABA(B) receptor-mediated signaling using Xenopus oocytes and baby hamster kidney (BHK) cells. Baclofen elicited inward K(+) currents in oocytes coexpressing heterodimeric GABA(B) receptor, GABA(B1a) subunit (GB(1a)R) and GABA(B2) subunit (GB(2)R), together with G protein-activated inwardly rectifying K(+) channels (GIRKs), in a concentration-dependent manner. Repetitive application of baclofen to oocytes coexpressing GABA(B)R and GIRKs did not change peak K(+) currents in the first and second responses, but the latter responses were significantly attenuated by coexpression of either GRK4 or GRK5 with attenuation efficacy of GRK4 > GRK5. Coexpression of other GRKs including GRK2, GRK3, and GRK6 had no effect on GABA(B) receptor-mediated desensitization processes. In BHK cells coexpressing GRK4 fused to Venus (brighter variant of yellow fluorescent protein, GRK4-Venus) with GB(1a)R and GB(2)R, GRK4-Venus was expressed in the cytosol but was translocated to the plasma membranes by GABA(B)R activation. In BHK cells coexpressing GRK4 fused to Cerulean (brighter variant of cyan fluorescent protein, GRK4-Cerulean) with GB(1a)R and GB(2)R-Venus, fluorescence resonance energy transfer (FRET) analysis demonstrated that GRK4-Cerulean formed a protein complex with GB(2)R-Venus. Immunoprecipitation and Western blot analysis confirmed GB(2)R-GRK4 complex formation. GRK5 also formed a complex with GB(2)R on the plasma membranes as determined by FRET and Western blotting but not GRK2, GRK3, and GRK6. Our results indicate that GRK4 and GRK5 desensitize GABA(B) receptor-mediated responses by forming protein complexes with GB(2)R subunit of GABA(B)R at the plasma membranes.
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Affiliation(s)
- Masato Kanaide
- Department of Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
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34
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Breit A, Wolff K, Kalwa H, Jarry H, Büch T, Gudermann T. The natural inverse agonist agouti-related protein induces arrestin-mediated endocytosis of melanocortin-3 and -4 receptors. J Biol Chem 2006; 281:37447-56. [PMID: 17041250 DOI: 10.1074/jbc.m605982200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Agouti-related protein (Agrp), one of the two naturally occurring inverse agonists known to inhibit G protein-coupled receptor activity, regulates energy expenditure by decreasing basal and blocking agonist-promoted melanocortin receptor (MCR) signaling. Here we report that, in addition to its inverse agonistic activities, Agrp exhibits agonistic properties on the endocytosis pathway of melanocortin receptors. Sustained exposure of human embryonic kidney 293 cells to Agrp induced endocytosis of the MC3R or the MC4R. The extent and kinetics of Agrp-promoted MCR endocytosis were similar to the endocytosis induced by melanocortins. Using the bioluminescence resonance energy transfer technique, we further showed that after binding of Agrp both MCRs interacted with beta-arrestins. In line with this observation, in COS-7 cells co-expression of beta-arrestins enhanced Agrp-induced MCR endocytosis, whereas in human embryonic kidney 293 cells co-transfection of beta-arrestin-specific small interference RNAs diminished Agrp-promoted endocytosis. This new regulatory mechanism was likewise detectable in a cell line derived from murine hypothalamic neurons endogenously expressing MC4R, pointing to the physiological relevance of Agrp-promoted receptor endocytosis. In conclusion, we demonstrated that Agrp does not solely act by directly blocking MCR signaling but also by reducing the amount of MCR molecules accessible to melanocortins at the cell surface. This beta-arrestin-dependent mechanism reveals a new aspect of MCR signaling in particular and refines the concept of G protein-coupled receptor antagonism in general.
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MESH Headings
- Agouti-Related Protein
- Animals
- Arrestins/antagonists & inhibitors
- Arrestins/genetics
- Arrestins/metabolism
- Base Sequence
- COS Cells
- Cell Line
- Chlorocebus aethiops
- Cyclic AMP/biosynthesis
- Endocytosis/physiology
- Humans
- Intercellular Signaling Peptides and Proteins/genetics
- Intercellular Signaling Peptides and Proteins/metabolism
- Mice
- Protein Binding
- RNA, Small Interfering/genetics
- Receptor, Melanocortin, Type 3/antagonists & inhibitors
- Receptor, Melanocortin, Type 3/genetics
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/antagonists & inhibitors
- Receptor, Melanocortin, Type 4/genetics
- Receptor, Melanocortin, Type 4/metabolism
- Recombinant Fusion Proteins/antagonists & inhibitors
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Signal Transduction
- Transfection
- beta-Arrestins
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Affiliation(s)
- Andreas Breit
- Institut für Pharmakologie und Toxikologie, Philipps-Universität Marburg, 35033 Marburg, Germany
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35
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Herrick-Davis K, Weaver BA, Grinde E, Mazurkiewicz JE. Serotonin 5-HT2C receptor homodimer biogenesis in the endoplasmic reticulum: real-time visualization with confocal fluorescence resonance energy transfer. J Biol Chem 2006; 281:27109-16. [PMID: 16857671 DOI: 10.1074/jbc.m604390200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dimerization is a common property of G-protein-coupled receptors (GPCR). While the formation of GPCR dimers/oligomers has been reported to play important roles in regulating receptor expression, ligand binding, and second messenger activation, less is known about how and where GPCR dimerization occurs. The present study was performed to identify the precise cellular compartment in which class A GPCR dimer/oligomer biogenesis occurs. We addressed this issue using confocal microscopy and fluorescence resonance energy transfer (FRET) to monitor GPCR proximity within discrete intracellular compartments of intact living cells. Time-lapse confocal imaging was used to follow CFP- and YFP-tagged serotonin 5-HT2C receptors during biosynthesis in the endoplasmic reticulum (ER), trafficking through the Golgi apparatus and subsequent expression on the plasma membrane. Real-time monitoring of FRET between CFP- and YFP-tagged 5-HT2C receptors was performed by acceptor photobleaching within discrete regions of the ER, Golgi, and plasma membrane. The FRET signal was dependent on the ratio of CFP- to YFP-tagged 5-HT2C receptors expressed in each region and was independent of receptor expression level, as predicted for proteins in a non-random, clustered distribution. FRET efficiencies measured in the ER, Golgi, and plasma membrane were similar. These experiments provide direct evidence for homodimerization/oligomerization of class A GPCR in the ER and Golgi of intact living cells, and suggest that dimer/oligomer formation is a naturally occurring step in 5-HT2C receptor maturation and processing.
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Affiliation(s)
- Katharine Herrick-Davis
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA.
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36
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Breit A, Gagnidze K, Devi LA, Lagacé M, Bouvier M. Simultaneous activation of the delta opioid receptor (deltaOR)/sensory neuron-specific receptor-4 (SNSR-4) hetero-oligomer by the mixed bivalent agonist bovine adrenal medulla peptide 22 activates SNSR-4 but inhibits deltaOR signaling. Mol Pharmacol 2006; 70:686-96. [PMID: 16682504 DOI: 10.1124/mol.106.022897] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hetero-oligomerization among G protein-coupled receptors has been proposed to contribute to signal integration. Because sensory neuron-specific receptors (SNSRs) and the opioid receptors (OR) share a common ligand, the bovine adrenal medulla peptide (BAM) 22, and have opposite effects on pain modulation, we investigated the possible consequences of deltaOR/SNSR-4 hetero-oligomerization on the signaling properties of both receptor subtypes. Bioluminescence resonance energy transfer revealed that the human deltaOR has similar propensity to homo-oligomerize and to form hetero-oligomers with human SNSR-4 when coexpressed in human embryonic kidney 293 cells. The hetero-oligomerization leads to a receptor form displaying unique functional properties. Individual activation of either deltaOR or SNSR-4 in cells coexpressing the two receptors led to the modulation of their respective signaling pathways; inhibition of adenylyl cyclase and activation of phospholipase C, respectively. In contrast, the deltaOR/SNSR-4 bivalent agonist BAM22, which could activate each receptor expressed individually, fully activated the SNSR-4-dependent phospholipase C but did not promote deltaOR-mediated inhibition of adenylyl cyclase in deltaOR/SNSR-4-coexpressing cells. Likewise, concomitant activation of the deltaOR/SNSR-4 hetero-oligomer by selective deltaOR and SNSR-4 agonists promoted SNSR-4 but not deltaOR signaling, revealing an agonist-dependent dominant-negative effect of SNSR-4 on deltaOR signaling. Furthermore, the deltaOR selective antagonist naltrexone trans-inhibited the SNSR-4-promoted phospholipase C activation mediated by BAM22 but not by the SNSR-4-selective agonists, suggesting a bivalent binding mode of BAM22 to the deltaOR/SNSR-4 hetero-oligomer. The observation that BAM22 inhibited the Leu-enkephalin-promoted cAMP inhibition in rat dorsal root ganglia neurons supports the potential physiological implication of such regulatory mechanism.
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MESH Headings
- Adenylyl Cyclase Inhibitors
- Adenylyl Cyclases/metabolism
- Animals
- Cells, Cultured
- Endocytosis
- Enkephalin, Methionine/analogs & derivatives
- Enkephalin, Methionine/pharmacology
- Ganglia, Spinal/drug effects
- Humans
- Naltrexone/pharmacology
- Neurons, Afferent/metabolism
- Protein Kinase C/physiology
- Protein Precursors/pharmacology
- Rats
- Rats, Long-Evans
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/drug effects
- Receptors, Opioid, delta/antagonists & inhibitors
- Receptors, Opioid, delta/chemistry
- Receptors, Opioid, delta/drug effects
- Receptors, Opioid, delta/metabolism
- Signal Transduction
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Affiliation(s)
- Andreas Breit
- Département de Biochimie, Université de Montréal, H3C 3J7 Montréal, QC, Canada
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Bettler B, Tiao JYH. Molecular diversity, trafficking and subcellular localization of GABAB receptors. Pharmacol Ther 2006; 110:533-43. [PMID: 16644017 DOI: 10.1016/j.pharmthera.2006.03.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 03/23/2006] [Indexed: 12/14/2022]
Abstract
GABAB receptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, gamma-aminobutyric acid (GABA). While native studies predicted pharmacologically distinct GABAB receptor subtypes, molecular studies failed to identify the expected receptor varieties. Mouse genetic experiments therefore addressed whether the cloned receptors can account for the classical electrophysiological, biochemical and behavioral GABAB responses or whether additional receptors exist. Among G-protein coupled receptors, GABAB receptors are unique in that they require 2 distinct subunits for functioning. This atypical receptor structure triggered a large body of work that investigated the regulation of receptor assembly and trafficking. With the availability of molecular tools, substantial progress was also made in the analysis of the receptor protein distribution in neuronal compartments. Here, we review recent studies that shed light on the molecular diversity, the subcellular distribution and the cell surface dynamics of GABAB receptors.
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Affiliation(s)
- Bernhard Bettler
- Institute of Physiology, Department of Clinical-Biological Sciences, Pharmazentrum, Klingelbergstrasse 50-70, University of Basel, CH-4056 Basel, Switzerland.
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Perán M, Hooper H, Boulaiz H, Marchal JA, Aránega A, Salas R. The M3/M4 cytoplasmic loop of the α1 subunit restricts GABAARs lateral mobility: A study using fluorescence recovery after photobleaching. ACTA ACUST UNITED AC 2006; 63:747-57. [PMID: 17029290 DOI: 10.1002/cm.20156] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A crucial problem in neurobiology is how neurons are able to maintain neurotransmitter receptors at specific membrane domains. The large structural heterogeneity of gamma aminobutyric acid receptors (GABAARs) led to the hypothesis that there could be a link between GABAAR gene diversity and the targeting properties of the receptor complex. Previous studies using Fluorescence Recovery After Photobleaching (FRAP) have shown a restricted mobility in GABAARs containing the alpha1 subunit. The M3/M4 cytoplasmic loop is the region of the alpha1 subunit with the lowest sequence homology to other subunits. Therefore, we asked whether the M3/M4 loop is involved in cytoskeletal anchoring and GABAAR clustering. A series of alpha1 chimeric subunits was constructed: alpha1CH (control subunit), alpha1CD (Cytoplasmic loop deleted), alpha1CD2, and alpha1CD3 (alpha1 with the M3/M4 loop from the alpha2 and alpha3 subunits, respectively). Our results using FRAP indicate an involvement of the M3/M4 cytoplasmic loop of the alpha1 subunit in controlling receptor lateral mobility. On the other hand, inmunocytochemical approaches showed that this domain is not involved in subunit targeting to the cell surface, subunit-subunit assembly, or receptor aggregation.
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Affiliation(s)
- Macarena Perán
- Department of Anatomy and Human Embryology, Faculty of Medicine, University of Granada, Granada, Spain.
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Brock C, Boudier L, Maurel D, Blahos J, Pin JP. Assembly-dependent surface targeting of the heterodimeric GABAB Receptor is controlled by COPI but not 14-3-3. Mol Biol Cell 2005; 16:5572-8. [PMID: 16176975 PMCID: PMC1289403 DOI: 10.1091/mbc.e05-05-0400] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cell surface expression of transmembrane proteins is strictly regulated. Mutually exclusive interaction with COPI or 14-3-3 proteins has been proposed as a mechanism underlying such trafficking control of various proteins. In particular, 14-3-3 dimers have been proposed to "sense" correctly assembled oligomers, allowing their surface targeting by preventing COPI-mediated intracellular retention. Here we examined whether such a mechanism is involved in the quality control of the heterodimeric G protein-coupled GABAB receptor. Its GB1 subunit, carrying the retention signal RSR, only reaches the cell surface when associated with the GB2 subunit. We show that COPI and 14-3-3 specifically bind to the GB1 RSR sequence and that COPI is involved in its intracellular retention. However, we demonstrate that the interaction with 14-3-3 is not required for proper function of the GABAB receptor quality control. Accordingly, competition between 14-3-3 and COPI cannot be considered as a general trafficking control mechanism. A possible other role for competition between COPI and 14-3-3 binding is discussed.
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Uezono Y, Kanaide M, Kaibara M, Barzilai R, Dascal N, Sumikawa K, Taniyama K. Coupling of GABAB receptor GABAB2 subunit to G proteins: evidence from Xenopus oocyte and baby hamster kidney cell expression system. Am J Physiol Cell Physiol 2005; 290:C200-7. [PMID: 16120656 DOI: 10.1152/ajpcell.00269.2005] [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] [Indexed: 11/22/2022]
Abstract
Coupling of functional GABAB receptors (GABABR) to G proteins was investigated with an expression system of baby hamster kidney (BHK) cells and Xenopus oocytes. Fluorescence resonance energy transfer (FRET) analysis of BHK cells coexpressing GABAB1a receptor (GB1aR) fused to Cerulean, a brighter variant of cyan fluorescent protein, and GABAB2 receptor (GB2R) fused to Venus, a brighter variant of yellow fluorescent protein, revealed that GB1aR-Cerulean and GB2R-Venus form a heterodimer. The GABABR agonists baclofen and 3-aminopropylphosphonic acid (3-APPA) elicited inward-rectifying K+ currents in a concentration-dependent manner in oocytes expressing GB1aR and GB2R, or GB1aR-Cerulean and GB2R-Venus, together with G protein-activated inward-rectifying K+ channels (GIRKs), but not in oocytes expressing GB1aR alone or GB2R alone together with GIRKs. Oocytes coexpressing GB1aR + Galphai2-fused GB2R (GB2R-Galphai2) caused faster K+ currents in response to baclofen. Furthermore, oocytes coexpressing GB1aR + GB2R fused to Galphaqi5 (a chimeric Galphaq protein that activates PLC pathways) caused PLC-mediated Ca2+-activated Cl- currents in response to baclofen. In contrast, these responses to baclofen were not observed in oocytes coexpressing GB1aR-Galphai2 or GB1aR-Galphaqi5 together with GB2R. BHK cells and Xenopus oocytes coexpressing GB1aR-Cerulean + a triplet tandem of GB2R-Venus-Galphaqi5 caused FRET and Ca2+-activated Cl- currents, respectively, with a similar potency in BHK cells coexpressing GB1aR-Cerulean + GB2R-Venus and in oocytes coexpressing GB1aR + GB2R-Galphaqi5. Our results indicate that functional GABABR forms a heterodimer composed of GB1R and GB2R and that the signal transducing G proteins are directly coupled to GB2R but not to GB1R.
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Affiliation(s)
- Yasuhito Uezono
- Dept. of Pharmacology, Nagasaki Univ. Graduate School of Biomedical Sciences, Nagasaki 852-8523, Japan.
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