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Lu Y, Hatzipantelis CJ, Langmead CJ, Stewart GD. Molecular insights into orphan G protein-coupled receptors relevant to schizophrenia. Br J Pharmacol 2024; 181:2095-2113. [PMID: 37605621 DOI: 10.1111/bph.16221] [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: 01/11/2023] [Revised: 06/25/2023] [Accepted: 07/23/2023] [Indexed: 08/23/2023] Open
Abstract
Schizophrenia remains a sizable socio-economic burden that continues to be treated with therapeutics based on 70-year old science. All currently approved therapeutics primarily target the dopamine D2 receptor to achieve their efficacy. Whilst dopaminergic dysregulation is a key feature in this disorder, the targeting of dopaminergic machinery has yielded limited efficacy and an appreciable side effect burden. Over the recent decades, numerous drugs that engage non-dopaminergic G protein-coupled receptors (GPCRs) have yielded a promise of efficacy without the deleterious side effect profile, yet none have successfully completed clinical studies and progressed to the market. More recently, there has been increased attention around non-dopaminergic GPCR-targeting drugs, which demonstrated efficacy in some schizophrenia symptom domains. This provides renewed hope that effective schizophrenia treatment may lie outside of the dopaminergic space. Despite the potential for muscarinic receptor- (and other well-characterised GPCR families) targeting drugs to treat schizophrenia, they are often plagued with complications such as lack of receptor subtype selectivity and peripheral on-target side effects. Orphan GPCR studies have opened a new avenue of exploration with many demonstrating schizophrenia-relevant mechanisms and a favourable expression profile, thus offering potential for novel drug development. This review discusses centrally expressed orphan GPCRs: GPR3, GPR6, GPR12, GPR52, GPR85, GPR88 and GPR139 and their relationship to schizophrenia. We review their expression, signalling mechanisms and cellular function, in conjunction with small molecule development and structural insights. We seek to provide a snapshot of the growing evidence and development potential of new classes of schizophrenia therapeutics. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.
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Affiliation(s)
- Yao Lu
- Drug Discovery Biology and Neuroscience & Mental Health Therapeutic Program Area, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | | | - Christopher J Langmead
- Drug Discovery Biology and Neuroscience & Mental Health Therapeutic Program Area, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
- Neuromedicines Discovery Centre, Monash University, Parkville, Australia
- Phrenix Therapeutics, Parkville, Australia
| | - Gregory D Stewart
- Drug Discovery Biology and Neuroscience & Mental Health Therapeutic Program Area, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
- Neuromedicines Discovery Centre, Monash University, Parkville, Australia
- Phrenix Therapeutics, Parkville, Australia
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2
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Jobe A, Vijayan R. Orphan G protein-coupled receptors: the ongoing search for a home. Front Pharmacol 2024; 15:1349097. [PMID: 38495099 PMCID: PMC10941346 DOI: 10.3389/fphar.2024.1349097] [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: 12/04/2023] [Accepted: 02/15/2024] [Indexed: 03/19/2024] Open
Abstract
G protein-coupled receptors (GPCRs) make up the largest receptor superfamily, accounting for 4% of protein-coding genes. Despite the prevalence of such transmembrane receptors, a significant number remain orphans, lacking identified endogenous ligands. Since their conception, the reverse pharmacology approach has been used to characterize such receptors. However, the multifaceted and nuanced nature of GPCR signaling poses a great challenge to their pharmacological elucidation. Considering their therapeutic relevance, the search for native orphan GPCR ligands continues. Despite limited structural input in terms of 3D crystallized structures, with advances in machine-learning approaches, there has been great progress with respect to accurate ligand prediction. Though such an approach proves valuable given that ligand scarcity is the greatest hurdle to orphan GPCR deorphanization, the future pairings of the remaining orphan GPCRs may not necessarily take a one-size-fits-all approach but should be more comprehensive in accounting for numerous nuanced possibilities to cover the full spectrum of GPCR signaling.
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Affiliation(s)
- Amie Jobe
- Department of Biology, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ranjit Vijayan
- Department of Biology, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
- The Big Data Analytics Center, United Arab Emirates University, Al Ain, United Arab Emirates
- Zayed Bin Sultan Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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3
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Gay EA, Harris DL, Wilson JW, Blough BE. The development of diphenyleneiodonium analogs as GPR3 agonists. Bioorg Med Chem Lett 2023; 94:129427. [PMID: 37541631 PMCID: PMC10631289 DOI: 10.1016/j.bmcl.2023.129427] [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: 06/02/2023] [Revised: 07/20/2023] [Accepted: 07/29/2023] [Indexed: 08/06/2023]
Abstract
G protein-coupled receptor 3 (GPR3) is an orphan receptor potentially involved in many important physiological processes such as drug abuse, neuropathic pain, and anxiety and depression related disorders. Pharmacological studies of GPR3 have been limited due to the restricted number of known agonists and inverse agonists for this constitutively active receptor. In this medicinal chemistry study, we report the discovery of GPR3 agonists based off the diphenyleneiodonium (DPI) scaffold. The most potent full agonist was the 3-trifluoromethoxy analog (32) with an EC50 of 260 nM and 90% efficacy compared to DPI. Investigation of a homology model of GPR3 from multiple sequence alignment resulted in the finding of a binding site rich in potential π-π and π-cation interactions stabilizing DPI-scaffold agonists. MMGBSA free energy analysis showed a good correlation with trends in observed EC50s. DPI analogs retained the same high receptor selectivity for GPR3 over GPR6 and GPR12 as observed with DPI. Collectively, the DPI analog series shows that order of magnitude improvements in potency with the scaffold were attainable; however, attempts to replace the iodonium ion to make the scaffold more druggable failed.
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Affiliation(s)
- Elaine A Gay
- Center for Drug Discovery, RTI International, Research Triangle Park, NC 27709, USA.
| | - Danni L Harris
- Center for Drug Discovery, RTI International, Research Triangle Park, NC 27709, USA
| | - Joseph W Wilson
- Center for Drug Discovery, RTI International, Research Triangle Park, NC 27709, USA
| | - Bruce E Blough
- Center for Drug Discovery, RTI International, Research Triangle Park, NC 27709, USA
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Meinhardt MW, Giannone F, Hirth N, Bartsch D, Spampinato SM, Kelsch W, Spanagel R, Sommer WH, Hansson AC. Disrupted circadian expression of beta-arrestin 2 affects reward-related µ-opioid receptor function in alcohol dependence. J Neurochem 2021; 160:454-468. [PMID: 34919270 DOI: 10.1111/jnc.15559] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 12/09/2021] [Accepted: 12/09/2021] [Indexed: 12/13/2022]
Abstract
There is increasing evidence for a daily rhythm of μ-opioid receptor (MOR) efficacy and the development of alcohol dependence. Previous studies show that beta-Arrestin 2 (bArr2) has an impact on alcohol intake, at least partially mediated via modulation of MOR signaling, which in turn mediates the alcohol rewarding effects. Considering the interplay of circadian rhythms on MOR and alcohol dependence, we aimed to investigate bArr2 in alcohol dependence at different time-points of the day/light cycle on the level of bArr2 mRNA (in situ hybridization), MOR availability (receptor autoradiography) and MOR signaling (Damgo-stimulated G-protein coupling) in the nucleus accumbens of alcohol-dependent and non-dependent Wistar rats. Using a microarray data set we found that bArr2, but not bArr1, shows a diurnal transcription pattern in the accumbens of naïve rats with higher expression levels during the active cycle. In three-week abstinent rats, bArr2 is upregulated in the accumbens at the beginning of the active cycle (ZT15), whereas no differences were found at the beginning of the inactive cycle (ZT3), compared to controls. This effect was accompanied with a specific downregulation of MOR binding in the active cycle. Additionally, we detect a higher receptor coupling during the inactive cycle compared to the active cycle in alcohol-dependent animals. Together, we report a daily rhythmicity for bArr2 expression linked to an inverse pattern of MOR, suggesting an involvement for bArr2 on circadian regulation of G-protein coupled receptors in alcohol dependence. The presented data may have implications for the development of novel bArr2-related treatment targets for alcoholism.
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Affiliation(s)
- Marcus W Meinhardt
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany.,Department of Molecular Neuroimaging, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Francesco Giannone
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Nathalie Hirth
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Santi M Spampinato
- Department of Pharmacy and Biotechnology, University of Bologna, Via Irnerio 48, 40126, Bologna, Italy
| | - Wolfgang Kelsch
- Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Rainer Spanagel
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Wolfgang H Sommer
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
| | - Anita C Hansson
- Institute of Psychopharmacology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Square J5, 68159, Mannheim, Germany
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5
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GPR3 accelerates neurite outgrowth and neuronal polarity formation via PI3 kinase-mediating signaling pathway in cultured primary neurons. Mol Cell Neurosci 2021; 118:103691. [PMID: 34871769 DOI: 10.1016/j.mcn.2021.103691] [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: 06/05/2021] [Revised: 11/24/2021] [Accepted: 11/28/2021] [Indexed: 11/23/2022] Open
Abstract
During neuronal development, immature neurons extend neurites and subsequently polarize to form an axon and dendrites. We have previously reported that G protein-coupled receptor 3 (GPR3) levels increase during neuronal development, and that GPR3 has functions in neurite outgrowth and neuronal differentiation in cerebellar granular neurons. Moreover, GPR3 is transported and concentrated at the tips of neurite, thereby contributing to the local activation of protein kinase A (PKA). However, the signaling pathways for GPR3-mediated neurite outgrowth and its subsequent effects on neuronal polarization have not yet been elucidated. We therefore analyzed the signaling pathways related to GPR3-mediated neurite outgrowth, and also focused on the possible roles of GPR3 in axon polarization. We demonstrated that, in cerebellar granular neurons, GPR3-mediated neurite outgrowth was mediated by multiple signaling pathways, including those of PKA, extracellular signal-regulated kinases (ERKs), and most strongly phosphatidylinositol 3-kinase (PI3K). In addition, the GPR3-mediated activation of neurite outgrowth was associated with G protein-coupled receptor kinase 2 (GRK2)-mediated signaling and phosphorylation of the C-terminus serine/threonine residues of GPR3, which affected downstream protein kinase B (Akt) signaling. We further demonstrated that GPR3 was transiently increased early in the development of rodent hippocampal neurons. It was subsequently concentrated at the tip of the longest neurite, and was thus associated with accelerated polarity formation in a PI3K-dependent manner in rat hippocampal neurons. In addition, GPR3 knockout in mouse hippocampal neurons led to delayed neuronal polarity formation, thereby affecting the dephosphorylation of collapsing response mediator protein 2 (CRMP2), which is downstream of the PI3K signaling pathway. Taken together, these findings suggest that the intrinsic expression of GPR3 in differentiated neurons constitutively activates PI3K-mediated signaling pathway predominantly, thus accelerating neurite outgrowth and further augmenting polarity formation in primary cultured neurons.
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6
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Biringer RG. Endocannabinoid signaling pathways: beyond CB1R and CB2R. J Cell Commun Signal 2021; 15:335-360. [PMID: 33978927 PMCID: PMC8222499 DOI: 10.1007/s12079-021-00622-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/27/2021] [Indexed: 12/15/2022] Open
Abstract
The search for cannabinoid receptors other than CB1R and CB2R has been ongoing for over a decade. A number of orphan receptors have been proposed as potential cannabinoid receptors primarily based on phylogenic arguments and reactivity towards known endocannabinoids and phytocannabinoids. Seven putative cannabinoid receptors are described and discussed, and evidence for and against their inclusion in this category are presented.
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Affiliation(s)
- Roger Gregory Biringer
- College of Osteopathic Medicine, Lake Erie College of Osteopathic Medicine, Bradenton, FL, 34211, USA.
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7
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Arcones AC, Vila-Bedmar R, Mirasierra M, Cruces-Sande M, Vallejo M, Jones B, Tomas A, Mayor F, Murga C. GRK2 regulates GLP-1R-mediated early phase insulin secretion in vivo. BMC Biol 2021; 19:40. [PMID: 33658023 PMCID: PMC7931601 DOI: 10.1186/s12915-021-00966-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 01/22/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Insulin secretion from the pancreatic β-cell is finely modulated by different signals to allow an adequate control of glucose homeostasis. Incretin hormones such as glucagon-like peptide-1 (GLP-1) act as key physiological potentiators of insulin release through binding to the G protein-coupled receptor GLP-1R. Another key regulator of insulin signaling is the Ser/Thr kinase G protein-coupled receptor kinase 2 (GRK2). However, whether GRK2 affects insulin secretion or if GRK2 can control incretin actions in vivo remains to be analyzed. RESULTS Using GRK2 hemizygous mice, isolated pancreatic islets, and model β-cell lines, we have uncovered a relevant physiological role for GRK2 as a regulator of incretin-mediated insulin secretion in vivo. Feeding, oral glucose gavage, or administration of GLP-1R agonists in animals with reduced GRK2 levels (GRK2+/- mice) resulted in enhanced early phase insulin release without affecting late phase secretion. In contrast, intraperitoneal glucose-induced insulin release was not affected. This effect was recapitulated in isolated islets and correlated with the increased size or priming efficacy of the readily releasable pool (RRP) of insulin granules that was observed in GRK2+/- mice. Using nanoBRET in β-cell lines, we found that stimulation of GLP-1R promoted GRK2 association to this receptor and that GRK2 protein and kinase activity were required for subsequent β-arrestin recruitment. CONCLUSIONS Overall, our data suggest that GRK2 is an important negative modulator of GLP-1R-mediated insulin secretion and that GRK2-interfering strategies may favor β-cell insulin secretion specifically during the early phase, an effect that may carry interesting therapeutic applications.
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Affiliation(s)
- Alba C Arcones
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain
| | - Rocío Vila-Bedmar
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos (URJC), Madrid, Spain
| | - Mercedes Mirasierra
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM); Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (Ciberdem), Madrid, Spain
| | - Marta Cruces-Sande
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain
| | - Mario Vallejo
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM); Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (Ciberdem), Madrid, Spain
| | - Ben Jones
- Section of Investigative Medicine, Imperial College London, London, W12 0NN, UK
| | - Alejandra Tomas
- Section of Cell Biology and Functional Genomics, Imperial College London, London, W12 0NN, UK
| | - Federico Mayor
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain.
| | - Cristina Murga
- Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (CBMSO) UAM-CSIC; Instituto de Investigación Sanitaria Hospital Universitario La Princesa; CIBER de Enfermedades Cardiovasculares (CIBERCV), UNIVERSIDAD AUTONOMA DE MADRID and Instituto de Salud Carlos III, Madrid, Spain.
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8
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Cecconi S, Rapino C, Di Nisio V, Rossi G, Maccarrone M. The (endo)cannabinoid signaling in female reproduction: What are the latest advances? Prog Lipid Res 2019; 77:101019. [PMID: 31862482 DOI: 10.1016/j.plipres.2019.101019] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 10/11/2019] [Accepted: 11/04/2019] [Indexed: 02/06/2023]
Abstract
Cannabis extracts like marijuana have the highest consumption rate worldwide. Yet, their societal acceptance as recreational and therapeutic drugs could represent a serious hazard to female human reproduction, because cannabis ingredients [termed (phyto)cannabinoids] can perturb an endogenous system of lipid signals known as endocannabinoids. Accumulated evidence on animal models and humans has demonstrated a crucial role of these endogenous signals on different aspects of female reproduction, where they act through an ensamble of proteins that synthesize, transport, degrade and traffic them. Several reports have recently evidenced the potential role of endocannabinoids as biomarkers of female infertility for disease treatment and prevention, as well as their possible epigenetic effects on pregnancy. The purpose of this review is to provide an update of data collected in the last decade on the effects of cannabinoids and endocannabinoids on female reproductive events, from development and maturation of follicles and oocytes, to fertilization, oviductal transport, implantation and labor. In this context, a particular attention has been devoted to the ovary and the production of fertilizable oocytes, because recent studies have addressed this hot topic with conflicting results among species.
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Affiliation(s)
- Sandra Cecconi
- Department of Life, Health and Environmental Sciences, University of L'Aquila, 67100 L'Aquila, Italy.
| | - Cinzia Rapino
- Faculty of Veterinary Medicine, University of Teramo, 64100 Teramo, Italy.
| | - Valentina Di Nisio
- Department of Life, Health and Environmental Sciences, University of L'Aquila, 67100 L'Aquila, Italy.
| | - Gianna Rossi
- Department of Life, Health and Environmental Sciences, University of L'Aquila, 67100 L'Aquila, Italy.
| | - Mauro Maccarrone
- Department of Medicine, Campus Bio-Medico University of Rome, 00128 Rome, Italy; European Center for Brain Research (CERC)/Santa Lucia Foundation, Via del Fosso di Fiorano, 64 - 00143 Rome, Italy.
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9
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Ayukawa K, Suzuki C, Ogasawara H, Kinoshita T, Furuno M, Suzuki G. Development of a High-Throughput Screening-Compatible Assay for Discovery of GPR3 Inverse Agonists Using a cAMP Biosensor. SLAS DISCOVERY 2019; 25:287-298. [PMID: 31516076 DOI: 10.1177/2472555219875101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
While G-protein-coupled receptors (GPCRs) represent the largest class of cell surface proteins, there are ≥100 orphan GPCRs whose endogenous ligands are unknown. Accordingly, these could prove to be potential therapeutic targets for the pharmaceutical intervention of various diseases. Constitutively active orphan GPCRs are activated without ligands; thus, inverse agonists may be very useful pharmacological tools for inhibiting constitutive activity. However, in general, inverse agonist screening is considered more difficult to perform with high quality than antagonist screening, particularly due to the narrow assay window. We developed a high-throughput screening (HTS)-compatible assay to identify inverse agonists of GPR3. GPR3 is expressed in the central nervous system (CNS) and is known to be related to Alzheimer's disease and other CNS diseases. The GPR3 inducible cell line was established using T-REx 293 cells that stably expressed the tetracycline repressor protein, and the cAMP biosensor, GloSensor, was stably co-expressed. After optimization of the induction level of GPR3 and assay conditions, the GloSensor assay showed an approximately 20-fold signal-to-background ratio and high sensitivity. Using the HTS method, we successfully screened a library of hundreds of thousands of compounds for the inhibition of constitutive activity with good quality and excellent reproducibility. Finally, 35 compounds were identified as GPR3 selective inverse agonists. This inverse agonist screening approach using GloSensor in combination with the inducible expression of orphan GPCR indicates universal applicability to the search for inverse agonists of constitutively active orphan GPCRs.
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Affiliation(s)
- Kumiko Ayukawa
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Chie Suzuki
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Hiroyuki Ogasawara
- Pharmaceutical Frontier Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Kanazawa-ku, Yokohama, Kanagawa, Japan
| | - Tomomi Kinoshita
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Masahiro Furuno
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
| | - Gentaroh Suzuki
- Biological/Pharmacological Research Laboratories, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Takatsuki, Osaka, Japan
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10
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Laun AS, Shrader SH, Brown KJ, Song ZH. GPR3, GPR6, and GPR12 as novel molecular targets: their biological functions and interaction with cannabidiol. Acta Pharmacol Sin 2019; 40:300-308. [PMID: 29941868 PMCID: PMC6460361 DOI: 10.1038/s41401-018-0031-9] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 04/17/2018] [Indexed: 01/08/2023] Open
Abstract
The G protein-coupled receptors 3, 6, and 12 (GPR3, GPR6, and GPR12) comprise a family of closely related orphan receptors with no confirmed endogenous ligands. These receptors are constitutively active and capable of signaling through G protein-mediated and non-G protein-mediated mechanisms. These orphan receptors have previously been reported to play important roles in many normal physiological functions and to be involved in a variety of pathological conditions. Although they are orphans, GPR3, GPR6, and GPR12 are phylogenetically most closely related to the cannabinoid receptors. Using β-arrestin2 recruitment and cAMP accumulation assays, we recently found that the nonpsychoactive phytocannabinoid cannabidiol (CBD) is an inverse agonist for GPR3, GPR6, and GPR12. This discovery highlights these orphan receptors as potential new molecular targets for CBD, provides novel mechanisms of action, and suggests new therapeutic uses of CBD for illnesses such as Alzheimer's disease, Parkinson's disease, cancer, and infertility. Furthermore, identification of CBD as a new inverse agonist for GPR3, GPR6, and GPR12 provides the initial chemical scaffolds upon which potent and efficacious agents acting on these receptors can be developed, with the goal of developing chemical tools for studying these orphan receptors and ultimately new therapeutic agents.
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Affiliation(s)
- Alyssa S Laun
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, 40292, USA
| | - Sarah H Shrader
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, 40292, USA
| | - Kevin J Brown
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, 40292, USA
| | - Zhao-Hui Song
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, 40292, USA.
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11
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Morales P, Isawi I, Reggio PH. Towards a better understanding of the cannabinoid-related orphan receptors GPR3, GPR6, and GPR12. Drug Metab Rev 2018; 50:74-93. [PMID: 29390908 DOI: 10.1080/03602532.2018.1428616] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
GPR3, GPR6, and GPR12 are three orphan receptors that belong to the Class A family of G-protein-coupled receptors (GPCRs). These GPCRs share over 60% of sequence similarity among them. Because of their close phylogenetic relationship, GPR3, GPR6, and GPR12 share a high percentage of homology with other lipid receptors such as the lysophospholipid and the cannabinoid receptors. On the basis of sequence similarities at key structural motifs, these orphan receptors have been related to the cannabinoid family. However, further experimental data are required to confirm this association. GPR3, GPR6, and GPR12 are predominantly expressed in mammalian brain. Their high constitutive activation of adenylyl cyclase triggers increases in cAMP levels similar in amplitude to fully activated GPCRs. This feature defines their physiological role under certain pathological conditions. In this review, we aim to summarize the knowledge attained so far on the understanding of these receptors. Expression patterns, pharmacology, physiopathological relevance, and molecules targeting GPR3, GPR6, and GPR12 will be analyzed herein. Interestingly, certain cannabinoid ligands have been reported to modulate these orphan receptors. The current debate about sphingolipids as putative endogenous ligands will also be addressed. A special focus will be on their potential role in the brain, particularly under neurological conditions such as Parkinson or Alzheimer's disease. Reported physiological roles outside the central nervous system will also be covered. This critical overview may contribute to a further comprehension of the physiopathological role of these orphan GPCRs, hopefully attracting more research towards a future therapeutic exploitation of these promising targets.
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Affiliation(s)
- Paula Morales
- a Department of Chemistry and Biochemistry , University of North Carolina at Greensboro , Greensboro , NC , USA
| | - Israa Isawi
- a Department of Chemistry and Biochemistry , University of North Carolina at Greensboro , Greensboro , NC , USA
| | - Patricia H Reggio
- a Department of Chemistry and Biochemistry , University of North Carolina at Greensboro , Greensboro , NC , USA
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12
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Tanaka S. [Signaling and functions of G-protein-coupled receptor 3 in cerebellar granular neurons]. Nihon Yakurigaku Zasshi 2018; 152:78-83. [PMID: 30101864 DOI: 10.1254/fpj.152.78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
G-protein-coupled receptor 3 (GPR3) is a member of the class A rhodopsin-type GPCR family and is highly expressed in various neurons. A unique feature of GPR3 is its ability to constitutively activate the Gαs protein without the addition of ligands, which results in the elevation of the basal level of intracellular cAMP. During the development of the cerebellum, GPR3 expression is upregulated in cerebellar granular neurons (CGNs) and maintained thereafter. In our previous studies, we showed that the intrinsic expression of GPR3 in CGNs is highly associated with neurite outgrowth, neurite differentiation, and neuronal survival. Recently, we have focused on the possible signaling pathways associated with GPR3-mediated neurite outgrowth in CGNs. Interestingly, GPR3-mediated neurite outgrowth is mediated by not only PKA-dependent signaling pathways but also PI3K-mediated signaling pathways. Moreover, the Gβγ-mediated signaling pathway is involved in GPR3-mediated neurite outgrowth. These results suggested that neural expression of GPR3 stimulates multiple downstream signaling pathways, contributing to the maintenance of homeostasis in neurons. Further precise analyses of constitutively active GPCRs may help in unveiling novel neuronal functions.
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Affiliation(s)
- Shigeru Tanaka
- Department of Molecular and Pharmacological Neuroscience, Graduate school of Biomedical & Health Sciences, Hiroshima University
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Okamoto Y, Shikano S. Differential phosphorylation signals control endocytosis of GPR15. Mol Biol Cell 2017; 28:2267-2281. [PMID: 28615320 PMCID: PMC5555655 DOI: 10.1091/mbc.e16-09-0627] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 06/05/2017] [Accepted: 06/07/2017] [Indexed: 12/30/2022] Open
Abstract
GPR15 undergoes a ligand-independent endocytosis, which requires phosphorylation of a distal C-terminal Ser-357 mediated by multiple basophilic kinases. The functional role of Ser-357 in endocytosis is distinct from that of a conserved Ser/Thr cluster, which is more responsible for the use of GRKs and β-arrestin. GPR15 is an orphan G protein–coupled receptor (GPCR) that serves for an HIV coreceptor and was also recently found as a novel homing receptor for T-cells implicated in colitis. We show that GPR15 undergoes a constitutive endocytosis in the absence of ligand. The endocytosis was clathrin dependent and partially dependent on β-arrestin in HEK293 cells, and nearly half of the internalized GPR15 receptors were recycled to the plasma membrane. An Ala mutation of the distal C-terminal Arg-354 or Ser-357, which forms a consensus phosphorylation site for basophilic kinases, markedly reduced the endocytosis, whereas phosphomimetic mutation of Ser-357 to Asp did not. Ser-357 was phosphorylated in vitro by multiple kinases, including PKA and PKC, and pharmacological activation of these kinases enhanced both phosphorylation of Ser-357 and endocytosis of GPR15. These results suggested that Ser-357 phosphorylation critically controls the ligand-independent endocytosis of GPR15. The functional role of Ser-357 in endocytosis was distinct from that of a conserved Ser/Thr cluster in the more proximal C-terminus, which was responsible for the β-arrestin– and GPCR kinase–dependent endocytosis of GPR15. Thus phosphorylation signals may differentially control cell surface density of GPR15 through endocytosis.
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Affiliation(s)
- Yukari Okamoto
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607-7170
| | - Sojin Shikano
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607-7170
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Wang C, Xu C, Liu M, Pan Y, Bai B, Chen J. C-terminus of OX2R significantly affects downstream signaling pathways. Mol Med Rep 2017; 16:159-166. [PMID: 28487995 PMCID: PMC5482145 DOI: 10.3892/mmr.2017.6557] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 03/30/2017] [Indexed: 12/11/2022] Open
Abstract
The human orexin 2 receptor (OX2R) is a G-protein‑coupled receptor (GPCR) that has been implicated in a number of diverse physiological functions. Recent studies have identified a number of functions of the C‑termini of GPCRs. However, the importance of the OX2R C‑terminus in regulating signaling and surface expression remains unclear. In the present study, the function of the OX2R C‑terminus was investigated using three C‑terminal mutants, which were truncated at residues 368, 384 and 414, respectively, and the wild‑type control, which expressed the full‑length OX2R. HEK‑293 cells were transfected with the mutated and control OX2R constructs. ELISA, western blot analysis and calcium assays were used to investigate the effects of the mutations on OX2R function. The present results demonstrated that residues 385‑414 and 415‑444 exhibited a cumulative effect on the surface expression of OX2R. Residues 369‑384 exhibited a significant influence on inositol phosphate production and extracellular signal‑regulated kinase 1/2 phosphorylation. Residues 385‑414 significantly influenced agonist‑induced internalization, whereas residues 369‑384 and 385‑414 significantly influenced Ca2+ release. The results of the present study suggest that the C‑terminus of OX2R is important for its role in various physiological and pathological processes, and may therefore be associated with such disorders as depression and anorexia.
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Affiliation(s)
- Chunmei Wang
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Chao Xu
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Minghui Liu
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Yanyou Pan
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Bo Bai
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
| | - Jing Chen
- Neurobiology Institute, Jining Medical University, Jining, Shandong 272067, P.R. China
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Miyagi T, Tanaka S, Hide I, Shirafuji T, Sakai N. The Subcellular Dynamics of the Gs-Linked Receptor GPR3 Contribute to the Local Activation of PKA in Cerebellar Granular Neurons. PLoS One 2016; 11:e0147466. [PMID: 26800526 PMCID: PMC4723318 DOI: 10.1371/journal.pone.0147466] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 01/03/2016] [Indexed: 12/12/2022] Open
Abstract
G-protein-coupled receptor (GPR) 3 is a member of the GPR family that constitutively activates adenylate cyclase. We have reported that the expression of GPR3 in cerebellar granular neurons (CGNs) contributes to neurite outgrowth and modulates neuronal proliferation and survival. To further identify its role, we have analyzed the precise distribution and local functions of GPR3 in neurons. The fluorescently tagged GPR3 protein was distributed in the plasma membrane, the Golgi body, and the endosomes. In addition, we have revealed that the plasma membrane expression of GPR3 functionally up-regulated the levels of PKA, as measured by a PKA FRET indicator. Next, we asked if the PKA activity was modulated by the expression of GPR3 in CGNs. PKA activity was highly modulated at the neurite tips compared to the soma. In addition, the PKA activity at the neurite tips was up-regulated when GPR3 was transfected into the cells. However, local PKA activity was decreased when endogenous GPR3 was suppressed by a GPR3 siRNA. Finally, we determined the local dynamics of GPR3 in CGNs using time-lapse analysis. Surprisingly, the fluorescent GPR3 puncta were transported along the neurite in both directions over time. In addition, the anterograde movements of the GPR3 puncta in the neurite were significantly inhibited by actin or microtubule polymerization inhibitors and were also disturbed by the Myosin II inhibitor blebbistatin. Moreover, the PKA activity at the tips of the neurites was decreased when blebbistatin was administered. These results suggested that GPR3 was transported along the neurite and contributed to the local activation of PKA in CGN development. The local dynamics of GPR3 in CGNs may affect local neuronal functions, including neuronal differentiation and maturation.
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Affiliation(s)
- Tatsuhiro Miyagi
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Shigeru Tanaka
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Izumi Hide
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Toshihiko Shirafuji
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Norio Sakai
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
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16
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Ahmad R, Wojciech S, Jockers R. Hunting for the function of orphan GPCRs - beyond the search for the endogenous ligand. Br J Pharmacol 2014; 172:3212-28. [PMID: 25231237 DOI: 10.1111/bph.12942] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 09/04/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022] Open
Abstract
Seven transmembrane-spanning proteins (7TM), also called GPCRs, are among the most versatile and evolutionary successful protein families. Out of the 400 non-odourant members identified in the human genome, approximately 100 remain orphans that have not been matched with an endogenous ligand. Apart from the classical deorphanization strategies, several alternative strategies provided recent new insights into the function of these proteins, which hold promise for high therapeutic potential. These alternative strategies consist of the phenotypical characterization of organisms silenced or overexpressing orphan 7TM proteins, the search for constitutive receptor activity and formation of protein complexes including 7TM proteins as well as the development of synthetic, surrogate ligands. Taken together, a variety of ligand-independent functions can be attributed to orphan 7TM proteins that range from constitutive activity to complex formation with other proteins and include 'true' orphans for which no ligand exist and 'conditional' orphans that behave like orphans in the absence of ligand and as non-orphans in the presence of ligand.
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Affiliation(s)
- Raise Ahmad
- Institut Cochin, INSERM, Paris, France.,CNRS UMR 8104, Paris, France.,Paris Descartes University, Paris, France
| | - Stefanie Wojciech
- Institut Cochin, INSERM, Paris, France.,CNRS UMR 8104, Paris, France.,Paris Descartes University, Paris, France
| | - Ralf Jockers
- Institut Cochin, INSERM, Paris, France.,CNRS UMR 8104, Paris, France.,Paris Descartes University, Paris, France
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17
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Tanaka S, Miyagi T, Dohi E, Seki T, Hide I, Sotomaru Y, Saeki Y, Antonio Chiocca E, Matsumoto M, Sakai N. Developmental expression of GPR3 in rodent cerebellar granule neurons is associated with cell survival and protects neurons from various apoptotic stimuli. Neurobiol Dis 2014; 68:215-27. [PMID: 24769160 DOI: 10.1016/j.nbd.2014.04.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 03/08/2014] [Accepted: 04/15/2014] [Indexed: 11/15/2022] Open
Abstract
G-protein coupled receptor 3 (GPR3), GPR6, and GPR12 belong to a family of constitutively active Gs-coupled receptors that activate 3'-5'-cyclic adenosine monophosphate (cAMP) and are highly expressed in the brain. Among these receptors, the endogenous expression of GPR3 in cerebellar granule neurons (CGNs) is increased following development. GPR3 is important for neurite outgrowth and neural maturation; however, the physiological functions of GPR3 remain to be fully elucidated. Here, we investigated the survival and antiapoptotic functions of GPR3 under normal and apoptosis-inducing culture conditions. Under normal culture conditions, CGNs from GPR3-knockout mice demonstrated lower survival than did CGNs from wild-type or GPR3-heterozygous mice. Cerebellar sections from GPR3-/- mice at P7, P14, and P21 revealed more caspase-3-positive neurons in the internal granular layer than in cerebellar sections from wild-type mice. Conversely, in a potassium-deprivation model of apoptosis, increased expression of these three receptors promoted neuronal survival. The antiapoptotic effect of GPR3 was also observed under hypoxic (1% O2/5% CO2) and reactive oxygen species (ROS)-induced apoptotic conditions. We further investigated the signaling pathways involved in the GPR3-mediated antiapoptotic effect. The addition of the PKA inhibitor KT5720, the MAP kinase inhibitor U0126, and the PI3 kinase inhibitor LY294002 abrogated the GPR3-mediated antiapoptotic effect in a potassium-deprivation model of apoptosis, whereas the PKC inhibitor Gö6976 did not affect the antiapoptotic function of GPR3. Furthermore, downregulation of endogenous GPR3 expression in CGNs resulted in a marked reduction in the basal levels of ERK and Akt phosphorylation under normal culture conditions. Finally, we used a transient middle cerebral artery occlusion (tMCAO) model in wild-type and GPR3-knockout mice to determine whether GPR3 expression modulates neuronal survival after brain ischemia. After tMCAO, GPR3-knockout mice exhibited a significantly larger infarct area than did wild-type mice. Collectively, these in vitro and in vivo results suggest that the developmental expression of constitutively active Gs-coupled GPR3 activates the ERK and Akt signaling pathways at the basal level, thereby protecting neurons from apoptosis that is induced by various stimuli.
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Affiliation(s)
- Shigeru Tanaka
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan; Department of Clinical Neuroscience and Therapeutics, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
| | - Tatsuhiro Miyagi
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Eisuke Dohi
- Department of Clinical Neuroscience and Therapeutics, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Takahiro Seki
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Izumi Hide
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Yusuke Sotomaru
- Natural Science Center for Basic Research and Development, Hiroshima University, Hiroshima 734-8551, Japan
| | | | - E Antonio Chiocca
- Harvey Cushing Neuro-Oncology Laboratories, Department of Neurosurgery, Institute for the Neurosciences at the Brigham, Brigham and Women's/Faulkner Hospital and Center for Neuro-Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
| | - Masayasu Matsumoto
- Department of Clinical Neuroscience and Therapeutics, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
| | - Norio Sakai
- Department of Molecular and Pharmacological Neuroscience, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima 734-8551, Japan
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18
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Ye C, Zhang Z, Wang Z, Hua Q, Zhang R, Xie X. Identification of a novel small-molecule agonist for human G protein-coupled receptor 3. J Pharmacol Exp Ther 2014; 349:437-43. [PMID: 24633425 DOI: 10.1124/jpet.114.213082] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptor 3 (GPR3) is an orphan G protein-coupled receptor (GPCR) predominantly expressed in mammalian brain and oocytes. GPR3 plays important roles in these two organs and is known as a Gαs-coupled receptor-activated constitutively in cells. However, the signal transduction pathway and pharmacological function of GPR3 remain unclear because of the lack of a specific ligand. By use of a human embryonic kidney 293 cell line stably expressing FLAG-GPR3-green fluorescent protein, a chemical screening for GPR3 ligands was performed using homogeneous time-resolved fluorescence cAMP assay. Diphenyleneiodonium chloride (DPI) was identified as a novel agonist of GPR3 with weak or no cross-reactivity with other GPCRs. DPI was further characterized to activate several GPR3-mediated signal transduction pathways, including Ca(2+) mobilization, cAMP accumulation, membrane recruitment of β-arrestin2, and receptor desensitization. Parallel studies revealed that the activity of DPI is much more pronounced than sphingosine 1-phosphate, a previously reported GPR3 agonist. Our study identified a novel and specific agonist of GPR3, which provides a useful tool for further study of this orphan GPCR.
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Affiliation(s)
- Chenli Ye
- Shanghai Key Laboratory of Signaling and Disease Research, Laboratory of Receptor-based Bio-medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China (C.Y., Z.Z., Q.H., R.Z., X.X.); and CAS Key Laboratory of Receptor Research, National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China (Z.W., X.X.)
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