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Philibert CE, Garcia-Marcos M. Smooth operator(s): dialing up and down neurotransmitter responses by G-protein regulators. Trends Cell Biol 2024:S0962-8924(24)00140-5. [PMID: 39054106 DOI: 10.1016/j.tcb.2024.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Revised: 06/19/2024] [Accepted: 07/01/2024] [Indexed: 07/27/2024]
Abstract
G-protein-coupled receptors (GPCRs) are essential mediators of neuromodulation and prominent pharmacological targets. While activation of heterotrimeric G-proteins (Gαβɣ) by GPCRs is essential in this process, much less is known about the postreceptor mechanisms that influence G-protein activity. Neurons express G-protein regulators that shape the amplitude and kinetics of GPCR-mediated synaptic responses. Although many of these operate by directly altering how G-proteins handle guanine-nucleotides enzymatically, recent discoveries have revealed alternative mechanisms by which GPCR-stimulated G-protein responses are modulated at the synapse. In this review, we cover the molecular basis for, and consequences of, the action of two G-protein regulators that do not affect the enzymatic activity of G-proteins directly: Gα inhibitory interacting protein (GINIP), which binds active Gα subunits, and potassium channel tetramerization domain-containing 12 (KCTD12), which binds active Gβγ subunits.
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Affiliation(s)
- Clementine E Philibert
- Department of Biochemistry and Cell Biology, Chobanian and Avedisian School of Medicine, Boston University, Boston, MA 02118, USA
| | - Mikel Garcia-Marcos
- Department of Biochemistry and Cell Biology, Chobanian and Avedisian School of Medicine, Boston University, Boston, MA 02118, USA; Department of Biology, College of Arts and Sciences, Boston University, Boston, MA 02115, USA.
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2
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Ortiz AJ, Martín V, Romero D, Guillamon A, Giraldo J. Time-dependent ligand-receptor binding kinetics and functionality in a heterodimeric receptor model. Biochem Pharmacol 2024; 225:116299. [PMID: 38763260 DOI: 10.1016/j.bcp.2024.116299] [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: 01/13/2024] [Revised: 05/05/2024] [Accepted: 05/16/2024] [Indexed: 05/21/2024]
Abstract
GPCRs heteromerize both in CNS and non-CNS regions. The cell uses receptor heteromerization to modulate receptor functionality and to provide fine tuning of receptor signaling. In order for pharmacologists to explore these mechanisms for therapeutic purposes, quantitative receptor models are needed. We have developed a time-dependent model of the binding kinetics and functionality of a preformed heterodimeric receptor involving two drugs. Two cases were considered: both or only one of the drugs are in excess with respect to the total concentration of the receptor. The latter case can be applied to those situations in which a drug causes unwanted side effects that need to be reduced by decreasing its concentration. The required efficacy can be maintained by the allosteric effects mutually exerted by the two drugs in the two-drug combination system. We discuss this concept assuming that the drug causing unwanted side effects is an opioid and that analgesia is the therapeutic effect. As additional points, allosteric modulation by endogenous compounds and synthetic bivalent ligands was included in the study. Receptor heteromerization offers a mechanistic understanding and quantification of the pharmacological effects elicited by combinations of two drugs at different doses and with different efficacies and cooperativity effects, thus providing a conceptual framework for drug combination therapy.
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Affiliation(s)
- Antonio J Ortiz
- Laboratory of Molecular Neuropharmacology and Bioinformatics, Unitat de Bioestadística and Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, Spain; Unitat de Neurociència Traslacional, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí (I3PT), Institut de Neurociències, Universitat Autònoma de Barcelona, Spain.
| | - Víctor Martín
- Laboratory of Molecular Neuropharmacology and Bioinformatics, Unitat de Bioestadística and Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Matemàtiques, EPSEB, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain.
| | - David Romero
- Centre de Recerca Matemàtica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
| | - Antoni Guillamon
- Departament de Matemàtiques, EPSEB, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain; IMTech, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain; Centre de Recerca Matemàtica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
| | - Jesús Giraldo
- Laboratory of Molecular Neuropharmacology and Bioinformatics, Unitat de Bioestadística and Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, Spain; Unitat de Neurociència Traslacional, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí (I3PT), Institut de Neurociències, Universitat Autònoma de Barcelona, Spain.
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3
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Belkacemi K, Rondard P, Pin JP, Prézeau L. Heterodimers Revolutionize the Field of Metabotropic Glutamate Receptors. Neuroscience 2024:S0306-4522(24)00270-7. [PMID: 38936459 DOI: 10.1016/j.neuroscience.2024.06.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 06/13/2024] [Accepted: 06/17/2024] [Indexed: 06/29/2024]
Abstract
Identified 40 years ago, the metabotropic glutamate (mGlu) receptors play key roles in modulating many synapses in the brain, and are still considered as important drug targets to treat various brain diseases. Eight genes encoding mGlu subunits have been identified. They code for complex receptors composed of a large extracellular domain where glutamate binds, connected to a G protein activating membrane domain. They are covalently linked dimers, a quaternary structure needed for their activation by glutamate. For many years they have only been considered as homodimers, then limiting the number of mGlu receptors to 8 subtypes composed of twice the same subunit. Twelve years ago, mGlu subunits were shown to also form heterodimers with specific subunits combinations, increasing the family up to 19 different potential dimeric receptors. Since then, a number of studies brought evidence for the existence of such heterodimers in the brain, through various approaches. Structural and molecular dynamic studies helped understand their peculiar activation process. The present review summarizes the approaches used to study their activation process and their pharmacological properties and to demonstrate their existence in vivo. We will highlight how the existence of mGlu heterodimers revolutionizes the mGlu receptor field, opening new possibilities for therapeutic intervention for brain diseases. As illustrated by the number of possible mGlu heterodimers, this study will highlight the need for further research to fully understand their role in physiological and pathological conditions, and to develop more specific therapeutic tools.
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Affiliation(s)
- Kawthar Belkacemi
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, Inserm, Montpellier, France
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, Inserm, Montpellier, France
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, Inserm, Montpellier, France.
| | - Laurent Prézeau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, Inserm, Montpellier, France.
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4
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Cevheroğlu O, Demirbaş B, Öğütcü D, Murat M. ADGRG1, an adhesion G protein-coupled receptor, forms oligomers. FEBS J 2024; 291:2461-2478. [PMID: 38468592 DOI: 10.1111/febs.17117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 01/26/2024] [Accepted: 03/01/2024] [Indexed: 03/13/2024]
Abstract
G protein-coupled receptor (GPCR) oligomerization is a highly debated topic in the field. While initially believed to function as monomers, current literature increasingly suggests that these cell surface receptors, spanning almost all GPCR families, function as homo- or hetero-oligomers. Yet, the functional consequences of these oligomeric complexes remain largely unknown. Adhesion GPCRs (aGPCRs) present an intriguing family of receptors characterized by their large and multi-domain N-terminal fragments (NTFs), intricate activation mechanisms, and the prevalence of numerous splice variants in almost all family members. In the present study, bioluminescence energy transfer (BRET) and Förster resonance energy transfer (FRET) were used to study the homo-oligomerization of adhesion G protein-coupled receptor G1 (ADGRG1; also known as GPR56) and to assess the involvement of NTFs in these receptor complexes. Based on the results presented herein, we propose that ADGRG1 forms 7-transmembrane-driven homo-oligomers on the plasma membrane. Additionally, Stachel motif interactions appear to influence the conformation of these receptor complexes.
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Affiliation(s)
| | - Berkay Demirbaş
- Department of Biological Sciences, Middle East Technical University, Çankaya, Turkey
| | - Dilara Öğütcü
- Department of Biological Sciences, Middle East Technical University, Çankaya, Turkey
| | - Merve Murat
- Department of Biological Sciences, Middle East Technical University, Çankaya, Turkey
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Mirchandani-Duque M, Choucri M, Hernández-Mondragón JC, Crespo-Ramírez M, Pérez-Olives C, Ferraro L, Franco R, Pérez de la Mora M, Fuxe K, Borroto-Escuela DO. Membrane Heteroreceptor Complexes as Second-Order Protein Modulators: A Novel Integrative Mechanism through Allosteric Receptor-Receptor Interactions. MEMBRANES 2024; 14:96. [PMID: 38786931 PMCID: PMC11122807 DOI: 10.3390/membranes14050096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 04/13/2024] [Accepted: 04/19/2024] [Indexed: 05/25/2024]
Abstract
Bioluminescence and fluorescence resonance energy transfer (BRET and FRET) together with the proximity ligation method revealed the existence of G-protein-coupled receptors, Ionotropic and Receptor tyrosine kinase heterocomplexes, e.g., A2AR-D2R, GABAA-D5R, and FGFR1-5-HT1AR heterocomplexes. Molecular integration takes place through allosteric receptor-receptor interactions in heteroreceptor complexes of synaptic and extra-synaptic regions. It involves the modulation of receptor protomer recognition, signaling and trafficking, as well as the modulation of behavioral responses. Allosteric receptor-receptor interactions in hetero-complexes give rise to concepts like meta-modulation and protein modulation. The introduction of receptor-receptor interactions was the origin of the concept of meta-modulation provided by Katz and Edwards in 1999, which stood for the fine-tuning or modulation of nerve cell transmission. In 2000-2010, Ribeiro and Sebastiao, based on a series of papers, provided strong support for their view that adenosine can meta-modulate (fine-tune) synaptic transmission through adenosine receptors. However, another term should also be considered: protein modulation, which is the key feature of allosteric receptor-receptor interactions leading to learning and consolidation by novel adapter proteins to memory. Finally, it must be underlined that allosteric receptor-receptor interactions and their involvement both in brain disease and its treatment are of high interest. Their pathophysiological relevance has been obtained, especially for major depressive disorder, cocaine use disorder, and Parkinson's disease.
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Affiliation(s)
- Marina Mirchandani-Duque
- Receptomics and Brain Disorders Lab, Department of Human Physiology Physical Education and Sport, Faculty of Medicine, University of Malaga, 29010 Málaga, Spain;
| | - Malak Choucri
- Department of Neuroscience, Karolinska Institutet, Biomedicum (B0852), Solnavägen 9, 17165 Solna, Sweden;
| | - Juan C. Hernández-Mondragón
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (J.C.H.-M.); (M.C.-R.); (M.P.d.l.M.)
| | - Minerva Crespo-Ramírez
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (J.C.H.-M.); (M.C.-R.); (M.P.d.l.M.)
| | - Catalina Pérez-Olives
- Molecular Neurobiology Laboratory, Department of Biochemistry and Molecular Biomedicine, Universitat de Barcelona, 08007 Barcelona, Spain;
| | - Luca Ferraro
- Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products University of Ferrara, 44121 Ferrara, Italy; (L.F.); (R.F.)
| | - Rafael Franco
- Department of Life Sciences and Biotechnology, Section of Medicinal and Health Products University of Ferrara, 44121 Ferrara, Italy; (L.F.); (R.F.)
| | - Miguel Pérez de la Mora
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (J.C.H.-M.); (M.C.-R.); (M.P.d.l.M.)
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Biomedicum (B0852), Solnavägen 9, 17165 Solna, Sweden;
| | - Dasiel O. Borroto-Escuela
- Receptomics and Brain Disorders Lab, Department of Human Physiology Physical Education and Sport, Faculty of Medicine, University of Malaga, 29010 Málaga, Spain;
- Department of Neuroscience, Karolinska Institutet, Biomedicum (B0852), Solnavägen 9, 17165 Solna, Sweden;
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Zhang M, Chen T, Lu X, Lan X, Chen Z, Lu S. G protein-coupled receptors (GPCRs): advances in structures, mechanisms, and drug discovery. Signal Transduct Target Ther 2024; 9:88. [PMID: 38594257 PMCID: PMC11004190 DOI: 10.1038/s41392-024-01803-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 02/19/2024] [Accepted: 03/13/2024] [Indexed: 04/11/2024] Open
Abstract
G protein-coupled receptors (GPCRs), the largest family of human membrane proteins and an important class of drug targets, play a role in maintaining numerous physiological processes. Agonist or antagonist, orthosteric effects or allosteric effects, and biased signaling or balanced signaling, characterize the complexity of GPCR dynamic features. In this study, we first review the structural advancements, activation mechanisms, and functional diversity of GPCRs. We then focus on GPCR drug discovery by revealing the detailed drug-target interactions and the underlying mechanisms of orthosteric drugs approved by the US Food and Drug Administration in the past five years. Particularly, an up-to-date analysis is performed on available GPCR structures complexed with synthetic small-molecule allosteric modulators to elucidate key receptor-ligand interactions and allosteric mechanisms. Finally, we highlight how the widespread GPCR-druggable allosteric sites can guide structure- or mechanism-based drug design and propose prospects of designing bitopic ligands for the future therapeutic potential of targeting this receptor family.
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Affiliation(s)
- Mingyang Zhang
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China
- Medicinal Chemistry and Bioinformatics Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Ting Chen
- Department of Cardiology, Changzheng Hospital, Affiliated to Naval Medical University, Shanghai, 200003, China
| | - Xun Lu
- Medicinal Chemistry and Bioinformatics Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Xiaobing Lan
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China
| | - Ziqiang Chen
- Department of Orthopedics, Changhai Hospital, Affiliated to Naval Medical University, Shanghai, 200433, China.
| | - Shaoyong Lu
- Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China.
- Medicinal Chemistry and Bioinformatics Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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Rouyar A, Patil AA, Leon-Noreña M, Li M, Coutinho-Abreu IV, Akbari OS, Riffell JA. Transgenic line for characterizing GABA-receptor expression to study the neural basis of olfaction in the yellow-fever mosquito. Front Physiol 2024; 15:1381164. [PMID: 38606012 PMCID: PMC11008680 DOI: 10.3389/fphys.2024.1381164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 03/14/2024] [Indexed: 04/13/2024] Open
Abstract
The mosquito Aedes aegypti is an important vector of diseases including dengue, Zika, chikungunya, and yellow fever. Olfaction is a critical modality for mosquitoes enabling them to locate hosts, sources of nectar, and sites for oviposition. GABA is an essential neurotransmitter in olfactory processing in the insect brain, including the primary olfactory center, the antennal lobe. Previous work with Ae. aegypti has suggested that antennal lobe inhibition via GABA may be involved in the processing of odors. However, little is known about GABA receptor expression in the mosquito brain, or how they may be involved in odor attraction. In this context, generating mutants that target the mosquito's olfactory responses, and particularly the GABAergic system, is essential to achieve a better understanding of these diverse processes and olfactory coding in these disease vectors. Here we demonstrate the potential of a transgenic line using the QF2 transcription factor, GABA-B1QF2-ECFP, as a new neurogenetic tool to investigate the neural basis of olfaction in Ae. aegypti. Our results show that the gene insertion has a moderate impact on mosquito fitness. Moreover, the line presented here was crossed with a QUAS reporter line expressing the green fluorescent protein and used to determine the location of the metabotropic GABA-B1 receptor expression. We find high receptor expression in the antennal lobes, especially the cell bodies surrounding the antennal lobes. In the mushroom bodies, receptor expression was high in the Kenyon cells, but had low expression in the mushroom body lobes. Behavioral experiments testing the fruit odor attractants showed that the mutants lost their behavioral attraction. Together, these results show that the GABA-B1QF2-ECFP line provides a new tool to characterize GABAergic systems in the mosquito nervous system.
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Affiliation(s)
- Angela Rouyar
- Department of Biology, University of Washington, Seattle, WA, United States
| | - Anandrao A. Patil
- Department of Biology, University of Washington, Seattle, WA, United States
| | | | - Ming Li
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Iliano V. Coutinho-Abreu
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Omar S. Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States
| | - Jeff A. Riffell
- Department of Biology, University of Washington, Seattle, WA, United States
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Liu L, Lin L, Shen C, Rondard P, Pin JP, Xu C, Liu J. Asymmetric activation of dimeric GABA B and metabotropic glutamate receptors. Am J Physiol Cell Physiol 2023; 325:C79-C89. [PMID: 37184233 DOI: 10.1152/ajpcell.00150.2022] [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: 04/08/2022] [Revised: 04/27/2023] [Accepted: 05/11/2023] [Indexed: 05/16/2023]
Abstract
G protein-coupled receptors (GPCRs) represent the largest family of membrane proteins and are important drug targets. GPCRs are allosteric machines that transduce an extracellular signal to the cell by activating heterotrimeric G proteins. Herein, we summarize the recent advancements in the molecular activation mechanism of the γ-aminobutyric acid type B (GABAB) and metabotropic glutamate (mGlu) receptors, the most important class C GPCRs that modulate synaptic transmission in the brain. Both are mandatory dimers, this quaternary structure being needed for their function The structures of these receptors in different conformations and in complexes with G proteins have revealed their asymmetric activation. This asymmetry is further highlighted by the recent discovery of mGlu heterodimers, where the eight mGlu subunits can form specific and functional heterodimers. Finally, the development of allosteric modulators has revealed new possibilities for regulating the function of these receptors by targeting the transmembrane dimer interface. This family of receptors never ceases to astonish and serve as models to better understand the diversity and asymmetric functioning of GPCRs.NEW & NOTEWORTHY γ-aminobutyric acid type B (GABAB) and metabotropic glutamate (mGlu) receptors form constitutive dimers, which are required for their function. They serve as models to better understand the diversity and activation of G protein-coupled receptors (GPCRs). The structures of these receptors in different conformations and in complexes with G proteins have revealed their asymmetric activation. This asymmetry is further highlighted by the recent discovery of specific and functional mGlu heterodimers. Allosteric modulators can be developed to target the transmembrane interface and modulate the asymmetry.
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Affiliation(s)
- Lei 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, People's Republic of China
| | - Li Lin
- 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, People's Republic of China
| | - Cangsong Shen
- 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, People's Republic of China
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Chanjuan Xu
- 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, People's Republic of China
| | - 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, People's Republic of China
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Liu X, Wang H, Wang X, Ning Y, Liu W, Gao J. Baixiangdan capsule and Shuyu capsule regulate anger-out and anger-in, respectively: GB1–mediated GABA can regulate 5-HT levels in multiple brain regions. Aging (Albany NY) 2023; 15:2046-2065. [PMID: 36988497 PMCID: PMC10085605 DOI: 10.18632/aging.204589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 02/13/2023] [Indexed: 03/30/2023]
Abstract
The identity of the mechanism by which the Baixiangdan capsule (BXD) and the Shuyu capsule (SY) control anger-out (AO) and anger-in (AI) in rodents is unclear. The current study clarified the intervention role of BXD and SY on AO and AI male rats. We further explored the differences between BXD and SY in the treatment of AO and AI rats. Social isolation combined with the resident-intruder paradigm was used to establish the anger-out and AI rats models. On this basis, GABA content in the dorsal raphe nucleus (DRN) and serotonin (5-HT) contents in these brain regions were detected using ELISA after various time courses (0, 1, 3, 5, and 7 days) treated with BXD and SY. Co-expression of 5-HT and GB1 in the DRN was detected. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN. Changes in 5-HT levels in these brain regions were then detected. After treatment, rats in the BXD group exhibited lower aggressive behavior scores, longer latencies of aggression, lower total distances in the open field test, and a higher sucrose preference coefficient. Meanwhile, rats in the SY group exhibited higher aggressive behavior scores, shorter latencies of aggression, higher total distances in the open field test, and higher sucrose preference coefficients. With increasing medication duration, 5-HT levels in these brain regions were increased gradually, whereas GABA levels in the DRN were decreased gradually, and all recovered to normal levels by the 7th day. A large number of 5-HT-positive cells could be found in the immunofluorescence section in the DRN containing GABABR1 (GB1)-positive cells, indicating that 5-HT neurons in the DRN co-expressed with GB1. Furthermore, after the drug intervention, the 5-HT level in the DRN was elevated to a normal level, and the GB1 level in the DRN was decreased to a normal level. After the microinjection of baclofen into the DRN, the 5-HT contents in these brain regions were decreased. By contrast, the 5-HT contents were increased after injection with CGP35348. BXD and SY could effectively improve the abnormal behavior changes of AO and AI rats, and the optimal duration of action was 7 days. The improvement way is as follows: Decreased abnormal increase of GABA and GB1 in the DRN further mediated synaptic inhibition and increased 5-HT level in the DRN, leading to increased 5-HT levels in the PFC, hypothalamus, and hippocampus. Therefore, GB1-mediated GABA in the DRN could regulate 5-HT levels in these brain regions, which may be one of the ways by which BXD and SY treat AO and AI, respectively.
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Yang Y, Ren L, Li W, Zhang Y, Zhang S, Ge B, Yang H, Du G, Tang B, Wang H, Wang J. GABAergic signaling as a potential therapeutic target in cancers. Biomed Pharmacother 2023; 161:114410. [PMID: 36812710 DOI: 10.1016/j.biopha.2023.114410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/23/2023] Open
Abstract
GABA is the most common inhibitory neurotransmitter in the vertebrate central nervous system. Synthesized by glutamic acid decarboxylase, GABA could specifically bind with two GABA receptors to transmit inhibition signal stimuli into cells: GABAA receptor and GABAB receptor. In recent years, emerging studies revealed that GABAergic signaling not only participated in traditional neurotransmission but was involved in tumorigenesis as well as regulating tumor immunity. In this review, we summarize the existing knowledge of the GABAergic signaling pathway in tumor proliferation, metastasis, progression, stemness, and tumor microenvironment as well as the underlying molecular mechanism. We also discussed the therapeutical advances in targeting GABA receptors to provide the theoretical basis for pharmacological intervention of GABAergic signaling in cancer treatment especially immunotherapy.
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Affiliation(s)
- Yihui Yang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Liwen Ren
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Wan Li
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Yizhi Zhang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Sen Zhang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Binbin Ge
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Hong Yang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Guanhua Du
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China
| | - Bo Tang
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin's Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, 300060, China
| | - Hongquan Wang
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin's Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, 300060, China
| | - Jinhua Wang
- The State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Beijing 100050, China; Key Laboratory of Drug Target Research and Drug Screen, Institute of Materia Medica, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100050, China.
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11
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Liu H, Li Y, Gao Y. Asymmetric activation of class C GPCRs. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 195:77-87. [PMID: 36707156 DOI: 10.1016/bs.pmbts.2022.06.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Class C G-protein-coupled receptors (GPCRs) comprise a unique GPCR subfamily with large ligand-binding extracellular domains and function as obligate dimers. The recently resolved cryo-EM structures of full-length GABAB, CaSR, and mGlus have revealed that these receptors are activated in an asymmetric manner, leading to G-protein-coupling on one protomer within the receptor dimer. In this review we discuss the mechanisms of asymmetric activation in class C GPCRs and the unique mode of interaction with the inhibitory Gi protein. Upon activation, the two seven-transmembrane domains (7TMs) of class C GPCRs rearrange to form a conserved asymmetric TM6-TM6 interface. In contrast to class A and B GPCRs, G-protein coupling does not involve the cytoplasmic opening of TM6, but is facilitated through the coordination of intracellular loops. Furthermore, positive and negative allosteric modulators (PAMs and NAMs) adopt distinct conformations to regulate the activity of class C GPCRs. Taken together, these recent findings on the mechanism of asymmetric activation of class C GPCRs highlight a novel mechanism of G protein activation and provide new insights into the design of therapeutics targeting these receptors.
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Affiliation(s)
- Hongnan Liu
- Department of Cardiology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China; Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China
| | - Yanjun Li
- Department of Cardiology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China; Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China
| | - Yang Gao
- Department of Cardiology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, China; Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou, China; Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province, Hangzhou, China.
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12
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Caniceiro AB, Bueschbell B, Schiedel AC, Moreira IS. Class A and C GPCR Dimers in Neurodegenerative Diseases. Curr Neuropharmacol 2022; 20:2081-2141. [PMID: 35339177 PMCID: PMC9886835 DOI: 10.2174/1570159x20666220327221830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 02/21/2022] [Accepted: 03/23/2022] [Indexed: 11/22/2022] Open
Abstract
Neurodegenerative diseases affect over 30 million people worldwide with an ascending trend. Most individuals suffering from these irreversible brain damages belong to the elderly population, with onset between 50 and 60 years. Although the pathophysiology of such diseases is partially known, it remains unclear upon which point a disease turns degenerative. Moreover, current therapeutics can treat some of the symptoms but often have severe side effects and become less effective in long-term treatment. For many neurodegenerative diseases, the involvement of G proteincoupled receptors (GPCRs), which are key players of neuronal transmission and plasticity, has become clearer and holds great promise in elucidating their biological mechanism. With this review, we introduce and summarize class A and class C GPCRs, known to form heterodimers or oligomers to increase their signalling repertoire. Additionally, the examples discussed here were shown to display relevant alterations in brain signalling and had already been associated with the pathophysiology of certain neurodegenerative diseases. Lastly, we classified the heterodimers into two categories of crosstalk, positive or negative, for which there is known evidence.
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Affiliation(s)
- Ana B. Caniceiro
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; ,These authors contributed equally to this work.
| | - Beatriz Bueschbell
- PhD Programme in Experimental Biology and Biomedicine, Institute for Interdisciplinary Research (IIIUC), University of Coimbra, Casa Costa Alemão, 3030-789 Coimbra, Portugal; ,These authors contributed equally to this work.
| | - Anke C. Schiedel
- Department of Pharmaceutical & Medicinal Chemistry, Pharmaceutical Institute, University of Bonn, D-53121 Bonn, Germany;
| | - Irina S. Moreira
- University of Coimbra, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal; ,Center for Neuroscience and Cell Biology, Center for Innovative Biomedicine and Biotechnology, 3004-504 Coimbra, Portugal,Address correspondence to this author at the Center for Neuroscience and Cell Biology, Center for Innovative Biomedicine and Biotechnology, 3004-504 Coimbra, Portugal; E-mail:
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13
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Emerging Role of Neuron-Glia in Neurological Disorders: At a Glance. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:3201644. [PMID: 36046684 PMCID: PMC9423989 DOI: 10.1155/2022/3201644] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 08/05/2022] [Indexed: 11/18/2022]
Abstract
Based on the diverse physiological influence, the impact of glial cells has become much more evident on neurological illnesses, resulting in the origins of many diseases appearing to be more convoluted than previously happened. Since neurological disorders are often random and unknown, hence the construction of animal models is difficult to build, representing a small fraction of people with a gene mutation. As a result, an immediate necessity is grown to work within in vitro techniques for examining these illnesses. As the scientific community recognizes cell-autonomous contributions to a variety of central nervous system illnesses, therapeutic techniques involving stem cells for treating neurological diseases are gaining traction. The use of stem cells derived from a variety of sources is increasingly being used to replace both neuronal and glial tissue. The brain's energy demands necessitate the reliance of neurons on glial cells in order for it to function properly. Furthermore, glial cells have diverse functions in terms of regulating their own metabolic activities, as well as collaborating with neurons via secreted signaling or guidance molecules, forming a complex network of neuron-glial connections in health and sickness. Emerging data reveals that metabolic changes in glial cells can cause morphological and functional changes in conjunction with neuronal dysfunction under disease situations, highlighting the importance of neuron-glia interactions in the pathophysiology of neurological illnesses. In this context, it is required to improve our understanding of disease mechanisms and create potential novel therapeutics. According to research, synaptic malfunction is one of the features of various mental diseases, and glial cells are acting as key ingredients not only in synapse formation, growth, and plasticity but also in neuroinflammation and synaptic homeostasis which creates critical physiological capacity in the focused sensory system. The goal of this review article is to elaborate state-of-the-art information on a few glial cell types situated in the central nervous system (CNS) and highlight their role in the onset and progression of neurological disorders.
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14
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Dragan P, Atzei A, Sanmukh SG, Latek D. Computational and experimental approaches to probe GPCR activation and signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 193:1-36. [PMID: 36357073 DOI: 10.1016/bs.pmbts.2022.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
G protein-coupled receptors (GPCRs) regulate different physiological functions, e.g., sensation, growth, digestion, reproductivity, nervous and immune systems response, and many others. In eukaryotes, they are also responsible for intercellular communication in response to pathogens. The major primary messengers binding to these cell-surface receptors constitute small-molecule or peptide hormones and neurotransmitters, nucleotides, lipids as well as small proteins. The simplicity of the way how GPCR signaling can be regulated by their endogenous agonists prompted the usage of GPCRs as major drug targets in modern pharmacology. Drugs targeting GPCRs inhibit pathological processes at the very beginning. This enables to significantly reduce the occurrence of morphological changes caused by diseases. Until recently, X-ray crystallography was the method of the first choice to obtain high-resolution structural information about GPCRs. Following X-ray crystallography, cryo-EM gained attention in GPCR studies as a quick and low-cost alternative. FRET microscopy is also widely used for GPCRs in the analysis of protein-protein interactions (PPIs) in intact cells as well as for screening purposes. Regarding computational methods, molecular dynamics (MD) for many years has proven its usefulness in studying the GPCR activation. MODELLER and Rosetta were widely used to generate preliminary homology models of GPCRs for MD simulation systems. Apart from the conventional all-atom approach with explicitly defined solvent, also other techniques have been applied to GPCRs, e.g., MARTINI or hybrid methods involving the coarse-grained representation, less demanding regarding computational resources, and thus offering much larger simulation timescales.
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Affiliation(s)
- Paulina Dragan
- Faculty of Chemistry, University of Warsaw, Warsaw, Poland
| | | | | | - Dorota Latek
- Faculty of Chemistry, University of Warsaw, Warsaw, Poland.
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15
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Fu X, Wei S, Wang T, Fan H, Zhang Y, Costa CD, Brandner S, Yang G, Pan Y, He Y, Li N. Research Status of the Orphan G Protein Coupled Receptor 158 and Future Perspectives. Cells 2022; 11:cells11081334. [PMID: 35456013 PMCID: PMC9027133 DOI: 10.3390/cells11081334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/10/2022] [Accepted: 04/11/2022] [Indexed: 02/01/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) remain one of the most successful targets for therapeutic drugs approved by the US Food and Drug Administration (FDA). Many novel orphan GPCRs have been identified by human genome sequencing and considered as putative targets for refractory diseases. Of note, a series of studies have been carried out involving GPCR 158 (or GPR158) since its identification in 2005, predominantly focusing on the characterization of its roles in the progression of cancer and mental illness. However, advances towards an in-depth understanding of the biological mechanism(s) involved for clinical application of GPR158 are lacking. In this paper, we clarify the origin of the GPR158 evolution in different species and summarize the relationship between GPR158 and different diseases towards potential drug target identification, through an analysis of the sequences and substructures of GPR158. Further, we discuss how recent studies set about unraveling the fundamental features and principles, followed by future perspectives and thoughts, which may lead to prospective therapies involving GPR158.
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Affiliation(s)
- Xianan Fu
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Shoupeng Wei
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Tao Wang
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Hengxin Fan
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Ying Zhang
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Clive Da Costa
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK;
| | - Sebastian Brandner
- Department of Neurodegenerative Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK;
| | - Guang Yang
- Department of Burn and Plastic Surgery, Institute of Translational Medicine, Shenzhen Second People’s Hospital, The First Affiliated Hospital of Shenzhen University, Health Science Center, Shenzhen 518039, China;
| | - Yihang Pan
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
| | - Yulong He
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
- Center for Digestive Disease, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China
- Correspondence: (Y.H.); (N.L.)
| | - Ningning Li
- Tomas Lindhal Nobel Laureate Laboratory, The Seventh Affiliated Hospital of Sun Yat-sen University (SYSU), No.628, Zhenyuan Rd., Guangming Dist., Shenzhen 518107, China; (X.F.); (S.W.); (T.W.); (H.F.); (Y.Z.); (Y.P.)
- China-UK Institute for Frontier Science, Shenzhen 518107, China
- Correspondence: (Y.H.); (N.L.)
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16
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Gallo M, Defaus S, Andreu D. Disrupting GPCR Complexes with Smart Drug-like Peptides. Pharmaceutics 2022; 14:pharmaceutics14010161. [PMID: 35057055 PMCID: PMC8779866 DOI: 10.3390/pharmaceutics14010161] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/30/2021] [Accepted: 01/05/2022] [Indexed: 02/04/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are a superfamily of proteins classically described as monomeric transmembrane (TM) receptors. However, increasing evidence indicates that many GPCRs form higher-order assemblies made up of monomers pertaining to identical (homo) or to various (hetero) receptors. The formation and structure of these oligomers, their physiological role and possible therapeutic applications raise a variety of issues that are currently being actively explored. In this context, synthetic peptides derived from TM domains stand out as powerful tools that can be predictably targeted to disrupt GPCR oligomers, especially at the interface level, eventually impairing their action. However, despite such potential, TM-derived, GPCR-disrupting peptides often suffer from inadequate pharmacokinetic properties, such as low bioavailability, a short half-life or rapid clearance, which put into question their therapeutic relevance and promise. In this review, we provide a comprehensive overview of GPCR complexes, with an emphasis on current studies using GPCR-disrupting peptides mimicking TM domains involved in multimerization, and we also highlight recent strategies used to achieve drug-like versions of such TM peptide candidates for therapeutic application.
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Affiliation(s)
| | - Sira Defaus
- Correspondence: (S.D.); (D.A.); Tel.: +34-933160868 (S.D. & D.A.)
| | - David Andreu
- Correspondence: (S.D.); (D.A.); Tel.: +34-933160868 (S.D. & D.A.)
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17
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Fritzius T, Stawarski M, Isogai S, Bettler B. Structural Basis of GABA B Receptor Regulation and Signaling. Curr Top Behav Neurosci 2022; 52:19-37. [PMID: 32812202 DOI: 10.1007/7854_2020_147] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
GABAB receptors (GBRs), the G protein-coupled receptors for the inhibitory neurotransmitter γ-aminobutyric acid (GABA), activate Go/i-type G proteins that regulate adenylyl cyclase, Ca2+ channels, and K+ channels. GBR signaling to enzymes and ion channels influences neuronal activity, plasticity processes, and network activity throughout the brain. GBRs are obligatory heterodimers composed of GB1a or GB1b subunits with a GB2 subunit. Heterodimeric GB1a/2 and GB1b/2 receptors represent functional units that associate in a modular fashion with regulatory, trafficking, and effector proteins to generate receptors with distinct physiological functions. This review summarizes current knowledge on the structure, organization, and functions of multi-protein GBR complexes.
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Affiliation(s)
- Thorsten Fritzius
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Michal Stawarski
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Shin Isogai
- Biozentrum, Focal Area Structural Biology and Biophysics, University of Basel, Basel, Switzerland.
- Microbial Downstream Process Development, Lonza AG, Visp, Switzerland.
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland.
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18
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Dale NC, Johnstone EKM, Pfleger KDG. GPCR heteromers: An overview of their classification, function and physiological relevance. Front Endocrinol (Lausanne) 2022; 13:931573. [PMID: 36111299 PMCID: PMC9468249 DOI: 10.3389/fendo.2022.931573] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 08/08/2022] [Indexed: 11/25/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are capable of interacting to form higher order structures such as homomers and heteromers. Heteromerisation in particular has implications for receptor function, with research showing receptors can attain unique expression, ligand binding, signalling and intracellular trafficking upon heteromerisation. As such, GPCR heteromers represent novel drug targets with extensive therapeutic potential. Changes to ligand affinity, efficacy and G protein coupling have all been described, with alterations to these pharmacological aspects now well accepted as common traits for heteromeric complexes. Changes in internalisation and trafficking kinetics, as well as β-arrestin interactions are also becoming more apparent, however, few studies to date have explicitly looked at the implications these factors have upon the signalling profile of a heteromer. Development of ligands to target GPCR heteromers both experimentally and therapeutically has been mostly concentrated on bivalent ligands due to difficulties in identifying and developing heteromer-specific ligands. Improving our understanding of the pharmacology and physiology of GPCR heteromers will enable further development of heteromer-specific ligands with potential to provide therapeutics with increased efficacy and decreased side effects.
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Affiliation(s)
- Natasha C. Dale
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
| | - Elizabeth K. M. Johnstone
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
- School of Biomedical Sciences, The University of Western Australia, Nedlands, WA, Australia
- *Correspondence: Kevin D. G. Pfleger, ; Elizabeth K. M. Johnstone,
| | - Kevin D. G. Pfleger
- Molecular Endocrinology and Pharmacology, Harry Perkins Institute of Medical Research and Centre for Medical Research, The University of Western Australia, Nedlands, WA, Australia
- Australian Research Council Centre for Personalised Therapeutics Technologies, Perth, WA, Australia
- Dimerix Limited, Nedlands, Australia
- *Correspondence: Kevin D. G. Pfleger, ; Elizabeth K. M. Johnstone,
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19
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Abstract
Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain, acts at the ionotropic GABAA and GABAC receptors, and the metabotropic GABAB receptor. This chapter summarizes the studies that have investigated the role of the GABAB receptor in stress-related psychiatric disorders including anxiety and mood disorders. Overall, clinical and preclinical evidences strongly suggest that the GABAB receptor is a therapeutic candidate for depression and anxiety disorders. However, the clinical development of GABAB receptor-based drugs to treat these disorders has been hampered by their potential side-effects, particularly those of agonists. Nevertheless, the discovery of novel GABAB receptor allosteric modulators, and increasing understanding of the influence of specific intracellular GABAB receptor-associated proteins on GABAB receptor activity, may now pave the way towards GABAB receptor therapeutics in the treatment of mood and anxiety disorders.
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Affiliation(s)
- Daniela Felice
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - John F Cryan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
| | - Olivia F O'Leary
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
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20
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Parmar S, Tadavarty R, Sastry BR. G-protein coupled receptors and synaptic plasticity in sleep deprivation. World J Psychiatry 2021; 11:954-980. [PMID: 34888167 PMCID: PMC8613756 DOI: 10.5498/wjp.v11.i11.954] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 06/05/2021] [Accepted: 09/19/2021] [Indexed: 02/06/2023] Open
Abstract
Insufficient sleep has been correlated to many physiological and psychoneurological disorders. Over the years, our understanding of the state of sleep has transcended from an inactive period of rest to a more active state involving important cellular and molecular processes. In addition, during sleep, electrophysiological changes also occur in pathways in specific regions of the mammalian central nervous system (CNS). Activity mediated synaptic plasticity in the CNS can lead to long-term and sometimes permanent strengthening and/or weakening synaptic strength affecting neuronal network behaviour. Memory consolidation and learning that take place during sleep cycles, can be affected by changes in synaptic plasticity during sleep disturbances. G-protein coupled receptors (GPCRs), with their versatile structural and functional attributes, can regulate synaptic plasticity in CNS and hence, may be potentially affected in sleep deprived conditions. In this review, we aim to discuss important functional changes that can take place in the CNS during sleep and sleep deprivation and how changes in GPCRs can lead to potential problems with therapeutics with pharmacological interventions.
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Affiliation(s)
- Shweta Parmar
- Department of Anesthesiology, Pharmacology and Therapeutics, The University of British Columbia, Vancouver V6T 1Z3, British Columbia, Canada
| | - Ramakrishna Tadavarty
- Department of Anesthesiology, Pharmacology and Therapeutics, The University of British Columbia, Vancouver V6T 1Z3, British Columbia, Canada
| | - Bhagavatula R Sastry
- Department of Anesthesiology, Pharmacology and Therapeutics, The University of British Columbia, Vancouver V6T 1Z3, British Columbia, Canada
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21
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Liu XJ, Wang HJ, Wang XY, Ning YX, Gao J. GABABR1 in DRN mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior. Neurochem Int 2021; 150:105180. [PMID: 34509561 DOI: 10.1016/j.neuint.2021.105180] [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: 01/05/2021] [Revised: 08/26/2021] [Accepted: 09/06/2021] [Indexed: 11/21/2022]
Abstract
The identity of the mechanism that controls aggressive behavior in rodents is unclear. Serotonin (5-HT) and GABA are associated with aggressive behavior in rodents. However, the regulatory relationship between these chemicals in the different brain regions of rats has not been fully defined. This study aimed to clarify the role of GABABR1 in DRN-mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior. Rat models of highly and less aggressive behavior were established through social isolation plus resident intruder. On this basis, GABA content in the DRN and 5-HT contents in the PFC, hypothalamus, hippocampus and DRN were detected using ELISA. Co-expression of 5-HT and GB1 in the DRN was detected by immunofluorescence and immunoelectron microscopy at the tissue and subcellular levels, respectively. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN by stereotaxic injection. Changes in 5-HT levels in the PFC, hypothalamus and hippocampus were detected afterward. After modeling, rats with highly aggressive behavior exhibited higher aggressive behavior scores, shorter latencies of aggression, and higher total distances in the open field test than rats with less aggressive behavior. The contents of 5-HT in the PFC, hypothalamus and hippocampus of rats with high and low aggressive behavior (no difference between the two groups) were significantly decreased, but the change in GABA content in the DRN was the opposite. GB1 granules could be found on synaptic membranes containing 5-HT granules, which indicated that 5-HT neurons in the DRN co-expressed with GB1, which also occurred in double immunofluorescence results. At the same time, we found that the expression of GB1 in the DRN of rats with high and low aggressive behavior was significantly increased, and the expression of GB1 in the DRN of rats with low aggressive behavior was significantly higher than that in rats with high aggressive behavior. Nevertheless, the expression of 5-HT in DRN was opposite in these two groups. After microinjection of baclofen into the DRN, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group decreased significantly. In contrast, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group increased significantly after injection with CGP35348. The significant increase in GABA in the DRN combined with the significant increase in GB1 in the DRN further mediated the synaptic inhibition effect, which reduced the 5-HT level of 5-HT neurons in the DRN, resulting in a significant decrease in 5-HT levels in the PFC, hypothalamus and hippocampus. Therefore, GB1-mediated GABA regulation of 5-HT levels in the PFC, hypothalamus and hippocampus is one of the mechanisms of highly and less aggressive behavior originating in the DRN. The increased GB1 level in the DRN of LA-behavior rats exhibited a greater degree of change than in the HA-group rats, which indicated that differently decreased 5-HT levels in the DRN may be the internal mechanisms of high and low aggression behaviors.
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Affiliation(s)
- Xiao-Ju Liu
- Shandong University of Traditional Chinese Medicine, Jinan, 250355, People's Republic of China
| | - Hai-Juan Wang
- Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 250117, People's Republic of China
| | - Xiao-Yu Wang
- Shandong University of Traditional Chinese Medicine, Jinan, 250355, People's Republic of China
| | - Yin-Xia Ning
- Shandong University of Traditional Chinese Medicine, Jinan, 250355, People's Republic of China
| | - Jie Gao
- Shandong University of Traditional Chinese Medicine, Jinan, 250355, People's Republic of China.
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22
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A nanobody activating metabotropic glutamate receptor 4 discriminates between homo- and heterodimers. Proc Natl Acad Sci U S A 2021; 118:2105848118. [PMID: 34385321 DOI: 10.1073/pnas.2105848118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
There is growing interest in developing biologics due to their high target selectivity. The G protein-coupled homo- and heterodimeric metabotropic glutamate (mGlu) receptors regulate many synapses and are promising targets for the treatment of numerous brain diseases. Although subtype-selective allosteric small molecules have been reported, their effects on the recently discovered heterodimeric receptors are often not known. Here, we describe a nanobody that specifically and fully activates homodimeric human mGlu4 receptors. Molecular modeling and mutagenesis studies revealed that the nanobody acts by stabilizing the closed active state of the glutamate binding domain by interacting with both lobes. In contrast, this nanobody does not activate the heterodimeric mGlu2-4 but acts as a pure positive allosteric modulator. These data further reveal how an antibody can fully activate a class C receptor and bring further evidence that nanobodies represent an alternative way to specifically control mGlu receptor subtypes.
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23
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GABA B Receptor Chemistry and Pharmacology: Agonists, Antagonists, and Allosteric Modulators. Curr Top Behav Neurosci 2021; 52:81-118. [PMID: 34036555 DOI: 10.1007/7854_2021_232] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The GABAB receptors are metabotropic G protein-coupled receptors (GPCRs) that mediate the actions of the primary inhibitory neurotransmitter, γ-aminobutyric acid (GABA). In the CNS, GABA plays an important role in behavior, learning and memory, cognition, and stress. GABA is also located throughout the gastrointestinal (GI) tract and is involved in the autonomic control of the intestine and esophageal reflex. Consequently, dysregulated GABAB receptor signaling is associated with neurological, mental health, and gastrointestinal disorders; hence, these receptors have been identified as key therapeutic targets and are the focus of multiple drug discovery efforts for indications such as muscle spasticity disorders, schizophrenia, pain, addiction, and gastroesophageal reflex disease (GERD). Numerous agonists, antagonists, and allosteric modulators of the GABAB receptor have been described; however, Lioresal® (Baclofen; β-(4-chlorophenyl)-γ-aminobutyric acid) is the only FDA-approved drug that selectively targets GABAB receptors in clinical use; undesirable side effects, such as sedation, muscle weakness, fatigue, cognitive deficits, seizures, tolerance and potential for abuse, limit their therapeutic use. Here, we review GABAB receptor chemistry and pharmacology, presenting orthosteric agonists, antagonists, and positive and negative allosteric modulators, and highlight the therapeutic potential of targeting GABAB receptor modulation for the treatment of various CNS and peripheral disorders.
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24
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Structural Characterization of Receptor-Receptor Interactions in the Allosteric Modulation of G Protein-Coupled Receptor (GPCR) Dimers. Int J Mol Sci 2021; 22:ijms22063241. [PMID: 33810175 PMCID: PMC8005122 DOI: 10.3390/ijms22063241] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 03/17/2021] [Accepted: 03/20/2021] [Indexed: 01/07/2023] Open
Abstract
G protein-coupled receptor (GPCR) oligomerization, while contentious, continues to attract the attention of researchers. Numerous experimental investigations have validated the presence of GPCR dimers, and the relevance of dimerization in the effectuation of physiological functions intensifies the attractiveness of this concept as a potential therapeutic target. GPCRs, as a single entity, have been the main source of scrutiny for drug design objectives for multiple diseases such as cancer, inflammation, cardiac, and respiratory diseases. The existence of dimers broadens the research scope of GPCR functions, revealing new signaling pathways that can be targeted for disease pathogenesis that have not previously been reported when GPCRs were only viewed in their monomeric form. This review will highlight several aspects of GPCR dimerization, which include a summary of the structural elucidation of the allosteric modulation of class C GPCR activation offered through recent solutions to the three-dimensional, full-length structures of metabotropic glutamate receptor and γ-aminobutyric acid B receptor as well as the role of dimerization in the modification of GPCR function and allostery. With the growing influence of computational methods in the study of GPCRs, we will also be reviewing recent computational tools that have been utilized to map protein-protein interactions (PPI).
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25
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Bhagat K, Singh JV, Pagare PP, Kumar N, Sharma A, Kaur G, Kinarivala N, Gandu S, Singh H, Sharma S, Bedi PMS. Rational approaches for the design of various GABA modulators and their clinical progression. Mol Divers 2021; 25:551-601. [PMID: 32170466 PMCID: PMC8422677 DOI: 10.1007/s11030-020-10068-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 02/28/2020] [Indexed: 12/20/2022]
Abstract
GABA (γ-amino butyric acid) is an important inhibitory neurotransmitter in the central nervous system. Attenuation of GABAergic neurotransmission plays an important role in the etiology of several neurological disorders including epilepsy, Alzheimer's disease, Huntington's chorea, migraine, Parkinson's disease, neuropathic pain, and depression. Increase in the GABAergic activity may be achieved through direct agonism at the GABAA receptors, inhibition of enzymatic breakdown of GABA, or by inhibition of the GABA transport proteins (GATs). These functionalities make GABA receptor modulators and GATs attractive drug targets in brain disorders associated with decreased GABA activity. There have been several reports of development of GABA modulators (GABA receptors, GABA transporters, and GABAergic enzyme inhibitors) in the past decade. Therefore, the focus of the present review is to provide an overview on various design strategies and synthetic approaches toward developing GABA modulators. Furthermore, mechanistic insights, structure-activity relationships, and molecular modeling inputs for the biologically active derivatives have also been discussed. Summary of the advances made over the past few years in the clinical translation and development of GABA receptor modulators is also provided. This compilation will be of great interest to the researchers working in the field of neuroscience. From the light of detailed literature, it can be concluded that numerous molecules have displayed significant results and their promising potential, clearly placing them ahead as potential future drug candidates.
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Affiliation(s)
- Kavita Bhagat
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India
| | - Jatinder V Singh
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India
| | - Piyusha P Pagare
- Department of Medicinal Chemistry, School of Pharmacy and Institute for Structural Biology, Drug Discovery and Development, Virginia Commonwealth University, Richmond, VA, 23219, USA
| | - Nitish Kumar
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India
| | - Anchal Sharma
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India
| | - Gurinder Kaur
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India
| | - Nihar Kinarivala
- Program in Chemical Biology, Sloan Kettering Institute, New York, NY, 10065, USA
| | - Srinivasa Gandu
- Department of Cell Biology and Neuroscience, Cell and Development Biology Graduate Program, The State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Harbinder Singh
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India.
| | - Sahil Sharma
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India.
- Program in Chemical Biology, Sloan Kettering Institute, New York, NY, 10065, USA.
| | - Preet Mohinder S Bedi
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, PB, 143005, India.
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26
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Ellaithy A, Gonzalez-Maeso J, Logothetis DA, Levitz J. Structural and Biophysical Mechanisms of Class C G Protein-Coupled Receptor Function. Trends Biochem Sci 2020; 45:1049-1064. [PMID: 32861513 PMCID: PMC7642020 DOI: 10.1016/j.tibs.2020.07.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/22/2020] [Accepted: 07/30/2020] [Indexed: 02/07/2023]
Abstract
Groundbreaking structural and spectroscopic studies of class A G protein-coupled receptors (GPCRs), such as rhodopsin and the β2 adrenergic receptor, have provided a picture of how structural rearrangements between transmembrane helices control ligand binding, receptor activation, and effector coupling. However, the activation mechanism of other GPCR classes remains more elusive, in large part due to complexity in their domain assembly and quaternary structure. In this review, we focus on the class C GPCRs, which include metabotropic glutamate receptors (mGluRs) and gamma-aminobutyric acid B (GABAB) receptors (GABABRs) most prominently. We discuss the unique biophysical questions raised by the presence of large extracellular ligand-binding domains (LBDs) and constitutive homo/heterodimerization. Furthermore, we discuss how recent studies have begun to unravel how these fundamental class C GPCR features impact the processes of ligand binding, receptor activation, signal transduction, regulation by accessory proteins, and crosstalk with other GPCRs.
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Affiliation(s)
- Amr Ellaithy
- Department of Neurology, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA; Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Javier Gonzalez-Maeso
- Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Diomedes A Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, USA; Department of Chemistry and Chemical Biology, College of Science and Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY 10065, USA.
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27
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Impaired Expression of GABA Signaling Components in the Alzheimer's Disease Middle Temporal Gyrus. Int J Mol Sci 2020; 21:ijms21228704. [PMID: 33218044 PMCID: PMC7698927 DOI: 10.3390/ijms21228704] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/13/2020] [Accepted: 11/16/2020] [Indexed: 12/26/2022] Open
Abstract
γ-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter, playing a central role in the regulation of cortical excitability and the maintenance of the excitatory/inhibitory (E/I) balance. Several lines of evidence point to a remodeling of the cerebral GABAergic system in Alzheimer’s disease (AD), with past studies demonstrating alterations in GABA receptor and transporter expression, GABA synthesizing enzyme activity and focal GABA concentrations in post-mortem tissue. AD is a chronic neurodegenerative disorder with a poorly understood etiology and the temporal cortex is one of the earliest regions in the brain to be affected by AD neurodegeneration. Utilizing NanoString nCounter analysis, we demonstrate here the transcriptional downregulation of several GABA signaling components in the post-mortem human middle temporal gyrus (MTG) in AD, including the GABAA receptor α1, α2, α3, α5, β1, β2, β3, δ, γ2, γ3, and θ subunits and the GABAB receptor 2 (GABABR2) subunit. In addition to this, we note the transcriptional upregulation of the betaine-GABA transporter (BGT1) and GABA transporter 2 (GAT2), and the downregulation of the 67 kDa isoform of glutamate decarboxylase (GAD67), the primary GABA synthesizing enzyme. The functional consequences of these changes require further investigation, but such alterations may underlie disruptions to the E/I balance that are believed to contribute to cognitive decline in AD.
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28
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Zhang S, Xue L, Liu X, Zhang XC, Zhou R, Zhao H, Shen C, Pin JP, Rondard P, Liu J. Structural basis for distinct quality control mechanisms of GABA B receptor during evolution. FASEB J 2020; 34:16348-16363. [PMID: 33058267 DOI: 10.1096/fj.202001355rr] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 09/25/2020] [Accepted: 10/02/2020] [Indexed: 12/29/2022]
Abstract
Cell surface trafficking of many G protein-coupled receptors is tightly regulated. Among them, the mandatory heterodimer GABAB receptor for the main inhibitory neurotransmitter, γ-aminobutyric acid (GABA), is a model. In mammals, its cell surface trafficking is highly controlled by an endoplasmic reticulum retention signal in the C-terminal intracellular region of the GB1 subunit that is masked through a coiled-coil interaction with the GB2 subunit. Here, we investigate the molecular basis for the export of its homolog in Drosophila melanogaster that regulates the circadian rhythm and sleep. In contrast to mammals, the endoplasmic retention signal is carried by GB2, while GB1 reaches the cell surface alone. NMR analysis showed that the coiled-coil domain that controls GABAB heterodimer formation is structurally conserved between flies and mammals, despite specific features. These findings show the adaptation of a similar quality control system during evolution for maintaining the subunit composition of a functional heterodimeric receptor.
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Affiliation(s)
- Shenglan Zhang
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Li Xue
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Xuehui Liu
- Core Facility for Protein Research, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xuejun Cai Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Rui Zhou
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Han Zhao
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Cangsong Shen
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Jean-Philippe Pin
- CNRS, INSERM, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France
| | - Philippe Rondard
- CNRS, INSERM, Institut de Génomique Fonctionnelle, Université de Montpellier, Montpellier, France
| | - Jianfeng Liu
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China.,Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
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29
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Lai S, Cheng R, Gao D, Chen YG, Deng C. LGR5 constitutively activates NF-κB signaling to regulate the growth of intestinal crypts. FASEB J 2020; 34:15605-15620. [PMID: 33001511 DOI: 10.1096/fj.202001329r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 09/01/2020] [Accepted: 09/22/2020] [Indexed: 01/09/2023]
Abstract
Mammalian LGR5 and LGR4, markers of adult stem cells, are involved in many physiological functions by enhancing WNT signaling. However, whether LGR5 and LGR4 are coupled to other intracellular signaling pathways to regulate stem cell function remains unknown. Here, we show that LGR5 and LGR4 can constitutively activate NF-κB signaling in a ligand-independent manner, which is dependent on their C-termini, but independent of receptor endocytosis. Moreover, the C-termini of LGR5/4 interact with TROY, which is required for activating NF-κB signaling. In small intestinal crypt organoids, overexpression of a C-terminal deletion mutant of LGR5 inhibits the growth and bud formation of organoids, whereas overexpression of the R-spondin-binding mutant of LGR5 that is defective for WNT signaling can still promote organoid growth. Our study reveals that NF-κB signaling, regulated by LGR5 and LGR4, plays an important role in the survival of colon cancer cells and the growth of intestinal crypts. Our findings also suggest that LGR5/4-induced NF-κB signaling and WNT signaling may co-regulate the growth of LGR5+ adult stem cells and intestinal crypts.
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Affiliation(s)
- Shanshan Lai
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Ran Cheng
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Dan Gao
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Ye-Guang Chen
- The State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Cheng Deng
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
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30
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Serrano-Regal MP, Bayón-Cordero L, Ordaz RP, Garay E, Limon A, Arellano RO, Matute C, Sánchez-Gómez MV. Expression and Function of GABA Receptors in Myelinating Cells. Front Cell Neurosci 2020; 14:256. [PMID: 32973453 PMCID: PMC7472887 DOI: 10.3389/fncel.2020.00256] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/24/2020] [Indexed: 01/14/2023] Open
Abstract
Myelin facilitates the fast transmission of nerve impulses and provides metabolic support to axons. Differentiation of oligodendrocyte progenitor cells (OPCs) and Schwann cell (SC) precursors is critical for myelination during development and myelin repair in demyelinating disorders. Myelination is tightly controlled by neuron-glia communication and requires the participation of a wide repertoire of signals, including neurotransmitters such as glutamate, ATP, adenosine, or γ-aminobutyric acid (GABA). GABA is the main inhibitory neurotransmitter in the central nervous system (CNS) and it is also present in the peripheral nervous system (PNS). The composition and function of GABA receptors (GABARs) are well studied in neurons, while their nature and role in glial cells are still incipient. Recent studies demonstrate that GABA-mediated signaling mechanisms play relevant roles in OPC and SC precursor development and function, and stand out the implication of GABARs in oligodendrocyte (OL) and SC maturation and myelination. In this review, we highlight the evidence supporting the novel role of GABA with an emphasis on the molecular identity of the receptors expressed in these glial cells and the possible signaling pathways involved in their actions. GABAergic signaling in myelinating cells may have potential implications for developing novel reparative therapies in demyelinating diseases.
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Affiliation(s)
- Mari Paz Serrano-Regal
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - Laura Bayón-Cordero
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - Rainald Pablo Ordaz
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Edith Garay
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Agenor Limon
- Department of Neurology, Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, United States
| | - Rogelio O. Arellano
- Laboratorio de Neurofisiología Celular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Mexico
| | - Carlos Matute
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
| | - María Victoria Sánchez-Gómez
- Laboratory of Neurobiology, Achucarro Basque Center for Neuroscience, Leioa, Spain
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Leioa, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Leioa, Spain
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31
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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32
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Park J, Fu Z, Frangaj A, Liu J, Mosyak L, Shen T, Slavkovich VN, Ray KM, Taura J, Cao B, Geng Y, Zuo H, Kou Y, Grassucci R, Chen S, Liu Z, Lin X, Williams JP, Rice WJ, Eng ET, Huang RK, Soni RK, Kloss B, Yu Z, Javitch JA, Hendrickson WA, Slesinger PA, Quick M, Graziano J, Yu H, Fiehn O, Clarke OB, Frank J, Fan QR. Structure of human GABA B receptor in an inactive state. Nature 2020; 584:304-309. [PMID: 32581365 PMCID: PMC7725281 DOI: 10.1038/s41586-020-2452-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 05/01/2020] [Indexed: 01/21/2023]
Abstract
The human GABAB receptor-a member of the class C family of G-protein-coupled receptors (GPCRs)-mediates inhibitory neurotransmission and has been implicated in epilepsy, pain and addiction1. A unique GPCR that is known to require heterodimerization for function2-6, the GABAB receptor has two subunits, GABAB1 and GABAB2, that are structurally homologous but perform distinct and complementary functions. GABAB1 recognizes orthosteric ligands7,8, while GABAB2 couples with G proteins9-14. Each subunit is characterized by an extracellular Venus flytrap (VFT) module, a descending peptide linker, a seven-helix transmembrane domain and a cytoplasmic tail15. Although the VFT heterodimer structure has been resolved16, the structure of the full-length receptor and its transmembrane signalling mechanism remain unknown. Here we present a near full-length structure of the GABAB receptor, captured in an inactive state by cryo-electron microscopy. Our structure reveals several ligands that preassociate with the receptor, including two large endogenous phospholipids that are embedded within the transmembrane domains to maintain receptor integrity and modulate receptor function. We also identify a previously unknown heterodimer interface between transmembrane helices 3 and 5 of both subunits, which serves as a signature of the inactive conformation. A unique 'intersubunit latch' within this transmembrane interface maintains the inactive state, and its disruption leads to constitutive receptor activity.
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Affiliation(s)
- Jinseo Park
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Ziao Fu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Aurel Frangaj
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Jonathan Liu
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Lidia Mosyak
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Tong Shen
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA, USA
| | - Vesna N Slavkovich
- Department of Environmental Health Sciences, Columbia University, New York, NY, USA
| | - Kimberly M Ray
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Jaume Taura
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Baohua Cao
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Yong Geng
- Department of Pharmacology, Columbia University, New York, NY, USA
- Key Laboratory of Receptor Research, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hao Zuo
- Department of Pharmacology, Columbia University, New York, NY, USA
| | - Yongjun Kou
- Key Laboratory of Receptor Research, Center for Structure and Function of Drug Targets, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Robert Grassucci
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Shaoxia Chen
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Zheng Liu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Xin Lin
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Justin P Williams
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - William J Rice
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Edward T Eng
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology Center, New York, NY, USA
| | - Rick K Huang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Rajesh K Soni
- Proteomics Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA
| | - Brian Kloss
- Center on Membrane Protein Production and Analysis, New York Structural Biology Center, New York, NY, USA
| | - Zhiheng Yu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jonathan A Javitch
- Department of Pharmacology, Columbia University, New York, NY, USA
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
- Center on Membrane Protein Production and Analysis, New York Structural Biology Center, New York, NY, USA
| | - Paul A Slesinger
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthias Quick
- Department of Psychiatry, Columbia University, New York, NY, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY, USA
| | - Joseph Graziano
- Department of Environmental Health Sciences, Columbia University, New York, NY, USA
| | - Hongtao Yu
- Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Oliver Fiehn
- NIH West Coast Metabolomics Center, University of California Davis, Davis, CA, USA
| | - Oliver B Clarke
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA.
- Department of Anesthesiology and the Irving Institute for Clinical and Translational Research, Columbia University, New York, NY, USA.
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
- Department of Biological Sciences, Columbia University, New York, NY, USA.
| | - Qing R Fan
- Department of Pharmacology, Columbia University, New York, NY, USA.
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA.
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33
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Mugnaini C, Brizzi A, Mostallino R, Castelli MP, Corelli F. Structure optimization of positive allosteric modulators of GABA B receptors led to the unexpected discovery of antagonists/potential negative allosteric modulators. Bioorg Med Chem Lett 2020; 30:127443. [PMID: 32730942 DOI: 10.1016/j.bmcl.2020.127443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/21/2020] [Accepted: 07/23/2020] [Indexed: 11/25/2022]
Abstract
Positive allosteric modulators (PAMs) of GABAB receptor represent an interesting alternative to receptor agonists such as baclofen, as they act on the receptor in a more physiological way and thus are devoid of the side effects typically exerted by the agonists. Based on our interest in the identification of new GABAB receptor PAMs, we followed a merging approach to design new chemotypes starting from selected active compounds, such as GS39783, rac-BHFF, and BHF177, and we ended up with the synthesis of four different classes of compounds. The new compounds were tested alone or in the presence of 10 µM GABA using [35S]GTPγS binding assay to assess their functionality at the receptor. Unexpectedly, a number of them significantly inhibited GABA-stimulated GTPγS binding thus revealing a functional switch with respect to the prototype molecules. Further studies on selected compounds will clarify if they act as negative modulators of the receptor or, instead, as antagonists at the orthosteric binding site.
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Affiliation(s)
- Claudia Mugnaini
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100 Siena, SI, Italy.
| | - Antonella Brizzi
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100 Siena, SI, Italy
| | - Rafaela Mostallino
- Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy
| | - Maria Paola Castelli
- Department of Biomedical Sciences, University of Cagliari, 09042 Monserrato, Italy; Guy Everett Laboratory, University of Cagliari, 09042 Monserrato, Italy; Center of Excellence "Neurobiology of Addiction", University of Cagliari, 09042 Monserrato, Italy.
| | - Federico Corelli
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, I-53100 Siena, SI, Italy
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Evenseth LSM, Gabrielsen M, Sylte I. The GABA B Receptor-Structure, Ligand Binding and Drug Development. Molecules 2020; 25:molecules25133093. [PMID: 32646032 PMCID: PMC7411975 DOI: 10.3390/molecules25133093] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/02/2020] [Accepted: 07/06/2020] [Indexed: 11/17/2022] Open
Abstract
The γ-aminobutyric acid (GABA) type B receptor (GABAB-R) belongs to class C of the G-protein coupled receptors (GPCRs). Together with the GABAA receptor, the receptor mediates the neurotransmission of GABA, the main inhibitory neurotransmitter in the central nervous system (CNS). In recent decades, the receptor has been extensively studied with the intention being to understand pathophysiological roles, structural mechanisms and develop drugs. The dysfunction of the receptor is linked to a broad variety of disorders, including anxiety, depression, alcohol addiction, memory and cancer. Despite extensive efforts, few compounds are known to target the receptor, and only the agonist baclofen is approved for clinical use. The receptor is a mandatory heterodimer of the GABAB1 and GABAB2 subunits, and each subunit is composed of an extracellular Venus Flytrap domain (VFT) and a transmembrane domain of seven α-helices (7TM domain). In this review, we briefly present the existing knowledge about the receptor structure, activation and compounds targeting the receptor, emphasizing the role of the receptor in previous and future drug design and discovery efforts.
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Affiliation(s)
- Linn Samira Mari Evenseth
- Molecular Pharmacology and Toxicology, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway
| | - Mari Gabrielsen
- Molecular Pharmacology and Toxicology, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway
| | - Ingebrigt Sylte
- Molecular Pharmacology and Toxicology, Department of Medical Biology, Faculty of Health Sciences, UiT The Arctic University of Norway, NO-9037 Tromsø, Norway
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Abstract
GABA (γ-aminobutyric acid) stimulation of the metabotropic GABAB receptor results in prolonged inhibition of neurotransmission that is central to brain physiology1. GABAB belongs to the Family C of G protein-coupled receptors (GPCRs), which operate as dimers to relay synaptic neurotransmitter signals into a cellular response through the binding and activation of heterotrimeric G proteins2,3. GABAB, however, is unique in its function as an obligate heterodimer in which agonist binding and G protein activation take place on distinct subunits4,5. Here we show structures of heterodimeric and homodimeric full-length GABAB receptors. Complemented by cellular signaling assays and atomistic simulations, the structures reveal an essential role for the GABAB extracellular loop 2 (ECL2) in relaying structural transitions by ordering the linker connecting the extracellular ligand-binding domain to the transmembrane region. Furthermore, the ECL2 of both GABAB subunits caps and interacts with the hydrophilic head of a phospholipid occupying the extracellular half of the transmembrane domain, thereby providing a potentially crucial link between ligand binding and the receptor core that engages G protein. These results provide a starting framework to decipher mechanistic modes of signal transduction mediated by GABAB dimers and have important implications for rational drug design targeting these receptors.
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Abstract
Baclofen, β-(4-chlorophenyl)-γ-aminobutyric acid, holds a unique position in neuroscience, remaining the only U.S. Food and Drug Administration (FDA) approved GABAB agonist. While intended to be a more brain penetrant, i.e, ability to cross the blood-brain barrier (BBB), version of GABA (γ-aminobutyric acid) for the potential treatment of epilepsy, baclofen's highly efficacious muscle relaxant properties led to its approval, as a racemate, for the treatment of spasticity. Interestingly, baclofen received FDA approval before its receptor, GABAB, was discovered and its exact mechanism of action was known. In recent times, baclofen has a myriad of off-label uses, with the treatment for alcohol abuse and drug addiction garnering a great deal of attention. This Review aims to capture the >60 year legacy of baclofen by walking through the history, pharmacology, synthesis, drug metabolism, routes of administration, and societal impact of this Classic in chemical neuroscience.
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Affiliation(s)
- Caitlin N. Kent
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Charlotte Park
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Craig W. Lindsley
- Warren Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
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Shaye H, Ishchenko A, Lam JH, Han GW, Xue L, Rondard P, Pin JP, Katritch V, Gati C, Cherezov V. Structural basis of the activation of a metabotropic GABA receptor. Nature 2020; 584:298-303. [PMID: 32555460 PMCID: PMC8020835 DOI: 10.1038/s41586-020-2408-4] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 04/07/2020] [Indexed: 12/26/2022]
Abstract
Metabotropic γ-aminobutyric acid receptors (GABAB) are involved in the modulation of synaptic responses in the central nervous system and are implicated in various neuropsychological conditions, ranging from addiction to psychosis1. GABAB belongs to G protein-coupled receptor class C, and its functional entity consists of an obligate heterodimer composed of GB1 and GB22. Each subunit possesses an extracellular Venus flytrap domain, connected to a canonical seven-transmembrane domain. Here, we present four cryo-EM structures of the human full-length GB1-GB2 heterodimer in its inactive apo, two intermediate agonist-bound, and active agonist/positive allosteric modulator bound forms. The structures reveal startling differences, shedding light onto the complex motions underlying the unique activation mechanism of GABAB. Our results show that agonist binding in the GB1 Venus flytrap domain triggers a series of transitions, first rearranging and bringing the two transmembrane domains into close contact along transmembrane helix 6 and ultimately inducing conformational rearrangements in the GB2 transmembrane domain via a lever-like mechanism, potentiated by a positive allosteric modulator binding at the dimerization interface, to initiate downstream signaling.
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Affiliation(s)
- Hamidreza Shaye
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Andrii Ishchenko
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Jordy Homing Lam
- Bridge Institute, USC 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
| | - Gye Won Han
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Li Xue
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, France
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, France
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle (IGF), CNRS, INSERM, Université de Montpellier, Montpellier, France
| | - Vsevolod Katritch
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA.,Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA
| | - Cornelius Gati
- Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. .,Department of Structural Biology, Stanford University, Stanford, CA, USA.
| | - Vadim Cherezov
- Bridge Institute, USC Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA. .,Department of Chemistry, University of Southern California, Los Angeles, CA, USA. .,Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
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Direct Interaction of PP2A Phosphatase with GABA B Receptors Alters Functional Signaling. J Neurosci 2020; 40:2808-2816. [PMID: 32111696 PMCID: PMC7117905 DOI: 10.1523/jneurosci.2654-19.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/02/2020] [Accepted: 02/18/2020] [Indexed: 01/16/2023] Open
Abstract
Addictive drugs usurp the brain's intrinsic mechanism for reward, leading to compulsive and destructive behaviors. In the ventral tegmental area (VTA), the center of the brain's reward circuit, GABAergic neurons control the excitability of dopamine (DA) projection neurons and are the site of initial psychostimulant-dependent changes in signaling. Previous work established that cocaine/methamphetamine exposure increases protein phosphatase 2A (PP2A) activity, which dephosphorylates the GABABR2 subunit, promotes internalization of the GABAB receptor (GABABR) and leads to smaller GABABR-activated G-protein-gated inwardly rectifying potassium (GIRK) currents in VTA GABA neurons. How the actions of PP2A become selective for a particular signaling pathway is poorly understood. Here, we demonstrate that PP2A can associate directly with a short peptide sequence in the C terminal domain of the GABABR1 subunit, and that GABABRs and PP2A are in close proximity in rodent neurons (mouse/rat; mixed sexes). We show that this PP2A-GABABR interaction can be regulated by intracellular Ca2+ Finally, a peptide that potentially reduces recruitment of PP2A to GABABRs and thereby limits receptor dephosphorylation increases the magnitude of baclofen-induced GIRK currents. Thus, limiting PP2A-dependent dephosphorylation of GABABRs may be a useful strategy to increase receptor signaling for treating diseases.SIGNIFICANCE STATEMENT Dysregulation of GABAB receptors (GABABRs) underlies altered neurotransmission in many neurological disorders. Protein phosphatase 2A (PP2A) is involved in dephosphorylating and subsequent internalization of GABABRs in models of addiction and depression. Here, we provide new evidence that PP2A B55 regulatory subunit interacts directly with a small region of the C-terminal domain of the GABABR1 subunit, and that this interaction is sensitive to intracellular Ca2+ We demonstrate that a short peptide corresponding to the PP2A interaction site on GABABR1 competes for PP2A binding, enhances phosphorylation GABABR2 S783, and affects functional signaling through GIRK channels. Our study highlights how targeting PP2A dependent dephosphorylation of GABABRs may provide a specific strategy to modulate GABABR signaling in disease conditions.
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Kniazeff J. The different aspects of the GABAB receptor allosteric modulation. FROM STRUCTURE TO CLINICAL DEVELOPMENT: ALLOSTERIC MODULATION OF G PROTEIN-COUPLED RECEPTORS 2020; 88:83-113. [DOI: 10.1016/bs.apha.2020.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Fonin AV, Darling AL, Kuznetsova IM, Turoverov KK, Uversky VN. Multi-functionality of proteins involved in GPCR and G protein signaling: making sense of structure-function continuum with intrinsic disorder-based proteoforms. Cell Mol Life Sci 2019; 76:4461-4492. [PMID: 31428838 PMCID: PMC11105632 DOI: 10.1007/s00018-019-03276-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 08/05/2019] [Accepted: 08/12/2019] [Indexed: 12/21/2022]
Abstract
GPCR-G protein signaling system recognizes a multitude of extracellular ligands and triggers a variety of intracellular signaling cascades in response. In humans, this system includes more than 800 various GPCRs and a large set of heterotrimeric G proteins. Complexity of this system goes far beyond a multitude of pair-wise ligand-GPCR and GPCR-G protein interactions. In fact, one GPCR can recognize more than one extracellular signal and interact with more than one G protein. Furthermore, one ligand can activate more than one GPCR, and multiple GPCRs can couple to the same G protein. This defines an intricate multifunctionality of this important signaling system. Here, we show that the multifunctionality of GPCR-G protein system represents an illustrative example of the protein structure-function continuum, where structures of the involved proteins represent a complex mosaic of differently folded regions (foldons, non-foldons, unfoldons, semi-foldons, and inducible foldons). The functionality of resulting highly dynamic conformational ensembles is fine-tuned by various post-translational modifications and alternative splicing, and such ensembles can undergo dramatic changes at interaction with their specific partners. In other words, GPCRs and G proteins exist as sets of conformational/basic, inducible/modified, and functioning proteoforms characterized by a broad spectrum of structural features and possessing various functional potentials.
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Affiliation(s)
- Alexander V Fonin
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
| | - April L Darling
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Irina M Kuznetsova
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
| | - Konstantin K Turoverov
- Laboratory of structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russian Federation
- Department of Biophysics, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya av. 29, St. Petersburg, 195251, Russian Federation
| | - Vladimir N Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
- Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow, Russian Federation.
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Park J, Jeong D, Jang B, Oh ES. The melanocortin-1 receptor reversely regulates the melanin synthesis and migration of melanoma cells via dimerization-induced conformational changes. Biochem Biophys Res Commun 2019; 518:739-745. [DOI: 10.1016/j.bbrc.2019.08.123] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 08/23/2019] [Indexed: 01/03/2023]
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Hajj M, De Vita T, Vol C, Renassia C, Bologna JC, Brabet I, Cazade M, Pastore M, Blahos J, Labesse G, Pin JP, Prézeau L. Nonclassical Ligand-Independent Regulation of Go Protein by an Orphan Class C G-Protein–Coupled Receptor. Mol Pharmacol 2019; 96:233-246. [DOI: 10.1124/mol.118.113019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 05/28/2019] [Indexed: 01/20/2023] Open
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Pin JP, Kniazeff J, Prézeau L, Liu JF, Rondard P. GPCR interaction as a possible way for allosteric control between receptors. Mol Cell Endocrinol 2019; 486:89-95. [PMID: 30849406 DOI: 10.1016/j.mce.2019.02.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 02/19/2019] [Accepted: 02/20/2019] [Indexed: 12/17/2022]
Abstract
For more than twenty years now, GPCR dimers and larger oligomers have been the subject of intense debates. Evidence for a role of such complexes in receptor trafficking to and from the plasma membrane have been provided. However, one main issue is of course to determine whether or not such a phenomenon can be responsible for an allosteric and reciprocal control (allosteric control) of the subunits. Such a possibility would indeed add to the possible ways a cell integrates various signals targeting GPCRs. Among the large GPCR family, the class C receptors that include mGlu and GABAB receptors, represent excellent models to examine such a possibility as they are mandatory dimers. In the present review, we will report on the observed allosteric interaction between the subunits of class C GPCRs, both mGluRs and GABABRs, and on the structural bases of these interactions. We will then discuss these findings for other GPCR types such as the rhodopsin-like class A receptors. We will show that many of the observations made with class C receptors have also been reported with class A receptors, suggesting that the mechanisms involved in the allosteric control between subunits in GPCR dimers may not be unique to class C GPCRs.
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Affiliation(s)
- Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.
| | - Julie Kniazeff
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Laurent Prézeau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Jiang-Feng Liu
- Cellular Signaling Laboratory, International Research Center for Sensory Biology and Technology of MOST, Key Laboratory of Molecular Biophysics of MOE, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
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Structural basis for auxiliary subunit KCTD16 regulation of the GABA B receptor. Proc Natl Acad Sci U S A 2019; 116:8370-8379. [PMID: 30971491 DOI: 10.1073/pnas.1903024116] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Metabotropic GABAB receptors mediate a significant fraction of inhibitory neurotransmission in the brain. Native GABAB receptor complexes contain the principal subunits GABAB1 and GABAB2, which form an obligate heterodimer, and auxiliary subunits, known as potassium channel tetramerization domain-containing proteins (KCTDs). KCTDs interact with GABAB receptors and modify the kinetics of GABAB receptor signaling. Little is known about the molecular mechanism governing the direct association and functional coupling of GABAB receptors with these auxiliary proteins. Here, we describe the high-resolution structure of the KCTD16 oligomerization domain in complex with part of the GABAB2 receptor. A single GABAB2 C-terminal peptide is bound to the interior of an open pentamer formed by the oligomerization domain of five KCTD16 subunits. Mutation of specific amino acids identified in the structure of the GABAB2-KCTD16 interface disrupted both the biochemical association and functional modulation of GABAB receptors and G protein-activated inwardly rectifying K+ channel (GIRK) channels. These interfacial residues are conserved among KCTDs, suggesting a common mode of KCTD interaction with GABAB receptors. Defining the binding interface of GABAB receptor and KCTD reveals a potential regulatory site for modulating GABAB-receptor function in the brain.
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Tang H, Shu C, Chen H, Zhang X, Zang Z, Deng C. Constitutively active BRS3 is a genuinely orphan GPCR in placental mammals. PLoS Biol 2019; 17:e3000175. [PMID: 30840614 PMCID: PMC6422423 DOI: 10.1371/journal.pbio.3000175] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 03/18/2019] [Accepted: 02/19/2019] [Indexed: 11/19/2022] Open
Abstract
G protein-coupled receptors (GPCRs) play an important role in physiology and disease and represent the most productive drug targets. Orphan GPCRs, with their endogenous ligands unknown, were considered a source of drug targets and consequently attract great interest to identify their endogenous cognate ligands for deorphanization. However, a contrary view to the ubiquitous existence of endogenous ligands for every GPCR is that there might be a significant overlooked fraction of orphan GPCRs that function constitutively in a ligand-independent manner only. Here, we investigated the evolution of the bombesin receptor-ligand family in vertebrates in which one member-bombesin receptor subtype-3 (BRS3)-is a potential orphan GPCR. With analysis of 17 vertebrate BRS3 structures and 10 vertebrate BRS3 functional data, our results demonstrated that nonplacental vertebrate BRS3 still connects to the original ligands-neuromedin B (NMB) and gastrin-releasing peptide (GRP)-because of adaptive evolution, with significantly changed protein structure, especially in three altered key residues (Q127R, P205S, and R294H) originally involved in ligand binding/activation, whereas the placental mammalian BRS3 lost the binding affinity to NMB/GRP and constitutively activates Gs/Gq/G12 signaling in a ligand-independent manner. Moreover, the N terminus of placental mammalian BRS3 underwent positive selection, exhibiting significant structural differences compared to nonplacental vertebrate BRS3, and this domain plays an important role in constitutive activity of placental mammalian BRS3. In conclusion, constitutively active BRS3 is a genuinely orphan GPCR in placental mammals, including human. To our knowledge, this study identified the first example that might represent a new group of genuinely orphan GPCRs that will never be deorphanized by the discovery of a natural ligand and provided new perspectives in addition to the current ligand-driven GPCR deorphanization.
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Affiliation(s)
- Huihao Tang
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Chuanjun Shu
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
- Department of Bioinformatics, College of Biomedical Engineering and Information, Nanjing Medical University, Nanjing, China
| | - Haidi Chen
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Xiaojing Zhang
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Zhuqing Zang
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Cheng Deng
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
- * E-mail:
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El Khamlichi C, Reverchon-Assadi F, Hervouet-Coste N, Blot L, Reiter E, Morisset-Lopez S. Bioluminescence Resonance Energy Transfer as a Method to Study Protein-Protein Interactions: Application to G Protein Coupled Receptor Biology. Molecules 2019; 24:E537. [PMID: 30717191 PMCID: PMC6384791 DOI: 10.3390/molecules24030537] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 01/21/2019] [Accepted: 01/30/2019] [Indexed: 12/22/2022] Open
Abstract
The bioluminescence resonance energy transfer (BRET) approach involves resonance energy transfer between a light-emitting enzyme and fluorescent acceptors. The major advantage of this technique over biochemical methods is that protein-protein interactions (PPI) can be monitored without disrupting the natural environment, frequently altered by detergents and membrane preparations. Thus, it is considered as one of the most versatile technique for studying molecular interactions in living cells at "physiological" expression levels. BRET analysis has been applied to study many transmembrane receptor classes including G-protein coupled receptors (GPCR). It is well established that these receptors may function as dimeric/oligomeric forms and interact with multiple effectors to transduce the signal. Therefore, they are considered as attractive targets to identify PPI modulators. In this review, we present an overview of the different BRET systems developed up to now and their relevance to identify inhibitors/modulators of protein⁻protein interaction. Then, we introduce the different classes of agents that have been recently developed to target PPI, and provide some examples illustrating the use of BRET-based assays to identify and characterize innovative PPI modulators in the field of GPCRs biology. Finally, we discuss the main advantages and the limits of BRET approach to characterize PPI modulators.
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Affiliation(s)
- Chayma El Khamlichi
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, University of Orléans and INSERM, 45071 Orléans, France.
- PRC, INRA, CNRS, Université François Rabelais-Tours, 37380 Nouzilly, France.
| | - Flora Reverchon-Assadi
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, University of Orléans and INSERM, 45071 Orléans, France.
| | - Nadège Hervouet-Coste
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, University of Orléans and INSERM, 45071 Orléans, France.
| | - Lauren Blot
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, University of Orléans and INSERM, 45071 Orléans, France.
| | - Eric Reiter
- PRC, INRA, CNRS, Université François Rabelais-Tours, 37380 Nouzilly, France.
| | - Séverine Morisset-Lopez
- Centre de Biophysique Moléculaire, CNRS, UPR 4301, University of Orléans and INSERM, 45071 Orléans, France.
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Frangaj A, Fan QR. Structural biology of GABA B receptor. Neuropharmacology 2018; 136:68-79. [PMID: 29031577 PMCID: PMC5897222 DOI: 10.1016/j.neuropharm.2017.10.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 10/09/2017] [Accepted: 10/11/2017] [Indexed: 11/17/2022]
Abstract
Metabotropic GABAB receptor is a G protein-coupled receptor (GPCR) that mediates slow and prolonged inhibitory neurotransmission in the brain. It functions as a constitutive heterodimer composed of the GABAB1 and GABAB2 subunits. Each subunit contains three domains; the extracellular Venus flytrap module, seven-helix transmembrane region and cytoplasmic tail. In recent years, the three-dimensional structures of GABAB receptor extracellular and intracellular domains have been elucidated. These structures reveal the molecular basis of ligand recognition, receptor heterodimerization and receptor activation. Here we provide a brief review of the GABAB receptor structures, with an emphasis on describing the different ligand-bound states of the receptor. We will also compare these with the known structures of related GPCRs to shed light on the molecular mechanisms of activation and regulation in the GABAB system, as well as GPCR dimers in general. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- Aurel Frangaj
- Department of Pharmacology, Columbia University, New York, NY 10032, USA
| | - Qing R Fan
- Department of Pharmacology, Columbia University, New York, NY 10032, USA; Department of Pathology & Cell Biology, Columbia University, New York, NY 10032, USA.
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Porzionato A, Stocco E, Guidolin D, Agnati L, Macchi V, De Caro R. Receptor-Receptor Interactions of G Protein-Coupled Receptors in the Carotid Body: A Working Hypothesis. Front Physiol 2018; 9:697. [PMID: 29930516 PMCID: PMC6000251 DOI: 10.3389/fphys.2018.00697] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 05/18/2018] [Indexed: 12/15/2022] Open
Abstract
In the carotid body (CB), a wide series of neurotransmitters and neuromodulators have been identified. They are mainly produced and released by type I cells and act on many different ionotropic and metabotropic receptors located in afferent nerve fibers, type I and II cells. Most metabotropic receptors are G protein-coupled receptors (GPCRs). In other transfected or native cells, GPCRs have been demonstrated to establish physical receptor–receptor interactions (RRIs) with formation of homo/hetero-complexes (dimers or receptor mosaics) in a dynamic monomer/oligomer equilibrium. RRIs modulate ligand binding, signaling, and internalization of GPCR protomers and they are considered of relevance for physiology, pharmacology, and pathology of the nervous system. We hypothesize that RRI may also occur in the different structural elements of the CB (type I cells, type II cells, and afferent fibers), with potential implications in chemoreception, neuromodulation, and tissue plasticity. This ‘working hypothesis’ is supported by literature data reporting the contemporary expression, in type I cells, type II cells, or afferent terminals, of GPCRs which are able to physically interact with each other to form homo/hetero-complexes. Functional data about cross-talks in the CB between different neurotransmitters/neuromodulators also support the hypothesis. On the basis of the above findings, the most significant homo/hetero-complexes which could be postulated in the CB include receptors for dopamine, adenosine, ATP, opioids, histamine, serotonin, endothelin, galanin, GABA, cannabinoids, angiotensin, neurotensin, and melatonin. From a methodological point of view, future studies should demonstrate the colocalization in close proximity (less than 10 nm) of the above receptors, through biophysical (i.e., bioluminescence/fluorescence resonance energy transfer, protein-fragment complementation assay, total internal reflection fluorescence microscopy, fluorescence correlation spectroscopy and photoactivated localization microscopy, X-ray crystallography) or biochemical (co-immunoprecipitation, in situ proximity ligation assay) methods. Moreover, functional approaches will be able to show if ligand binding to one receptor produces changes in the biochemical characteristics (ligand recognition, decoding, and trafficking processes) of the other(s). Plasticity aspects would be also of interest, as development and environmental stimuli (chronic continuous or intermittent hypoxia) produce changes in the expression of certain receptors which could potentially invest the dynamic monomer/oligomer equilibrium of homo/hetero-complexes and the correlated functional implications.
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Affiliation(s)
| | - Elena Stocco
- Department of Neuroscience, University of Padua, Padua, Italy
| | - Diego Guidolin
- Department of Neuroscience, University of Padua, Padua, Italy
| | - Luigi Agnati
- Department of Diagnostic, Clinical Medicine and Public Health, University of Modena and Reggio Emilia, Modena, Italy
| | - Veronica Macchi
- Department of Neuroscience, University of Padua, Padua, Italy
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Gurevich VV, Gurevich EV. GPCRs and Signal Transducers: Interaction Stoichiometry. Trends Pharmacol Sci 2018; 39:672-684. [PMID: 29739625 DOI: 10.1016/j.tips.2018.04.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/11/2018] [Accepted: 04/13/2018] [Indexed: 12/12/2022]
Abstract
Until the late 1990s, class A G protein-coupled receptors (GPCRs) were believed to function as monomers. Indirect evidence that they might internalize or even signal as dimers has emerged, along with proof that class C GPCRs are obligatory dimers. Crystal structures of GPCRs and their much larger binding partners were consistent with the idea that two receptors might engage a single G protein, GRK, or arrestin. However, recent biophysical, biochemical, and structural evidence invariably suggests that a single GPCR binds G proteins, GRKs, and arrestins. Here we review existing evidence of the stoichiometry of GPCR interactions with signal transducers and discuss potential biological roles of class A GPCR oligomers, including proposed homo- and heterodimers.
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Affiliation(s)
- Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.
| | - Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
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Stewart GD, Comps-Agrar L, Nørskov-Lauritsen LB, Pin JP, Kniazeff J. Allosteric interactions between GABA B1 subunits control orthosteric binding sites occupancy within GABA B oligomers. Neuropharmacology 2018; 136:92-101. [PMID: 29305121 DOI: 10.1016/j.neuropharm.2017.12.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 12/22/2017] [Accepted: 12/25/2017] [Indexed: 12/16/2022]
Abstract
The GABAB receptor was the first G protein-coupled receptor identified as an obligate heterodimer. It is composed of two subunits, GABAB1 containing the agonist binding site and GABAB2 responsible for G protein activation. The GABAB receptor was found to associate into larger complexes through GABAB1-GABAB1 interactions, both in transfected cells and in brain membranes. Here we assessed the possible allosteric interactions between GABAB heterodimers by analyzing the effect of mutations located at the putative interface between the extracellular binding domains. These mutations decrease, but do not suppress, the Förster resonance energy transfer (FRET) signal measured between GABAB1 subunits. Further analysis of one of these mutations revealed an increase in G protein-coupling efficacy and in the maximal antagonist binding by approximately two-fold. Hypothesizing that a tetramer is an elementary unit within oligomers, additional FRET data using fluorescent ligands and tagged subunits suggest that adjacent binding sites within the GABAB oligomers are not simultaneously occupied. Our data show a strong negative effect between GABAB1 binding sites within GABAB oligomers. Accordingly, GABAB receptor assembly appears to limit receptor signaling to G proteins, a property that may offer novel regulatory mechanism for this important neuronal receptor. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- Gregory D Stewart
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Univ. Montpellier, France
| | - Laëtitia Comps-Agrar
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Univ. Montpellier, France; Cisbio Bioassays, Codolet, France
| | | | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Univ. Montpellier, France
| | - Julie Kniazeff
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Univ. Montpellier, France.
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