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Ma S, Yin X, Pin JP, Rondard P, Yi P, Liu J. Absence of calcium-sensing receptor basal activity due to inter-subunit disulfide bridges. Commun Biol 2024; 7:501. [PMID: 38664468 PMCID: PMC11045811 DOI: 10.1038/s42003-024-06189-3] [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: 08/21/2023] [Accepted: 04/12/2024] [Indexed: 04/28/2024] Open
Abstract
G protein-coupled receptors naturally oscillate between inactive and active states, often resulting in receptor constitutive activity with important physiological consequences. Among the class C G protein-coupled receptors that typically sense amino-acids and their derivatives, the calcium sensing receptor (CaSR) tightly controls blood calcium levels. Its constitutive activity has not yet been studied. Here, we demonstrate the importance of the inter-subunit disulfide bridges in maintaining the inactive state of CaSR, resulting in undetectable constitutive activity, unlike the other class C receptors. Deletion of these disulfide bridges results in strong constitutive activity that is abolished by mutations preventing amino acid binding. It shows that this inter-subunit disulfide link is necessary to limit the agonist effect of amino acids on CaSR. Furthermore, human genetic mutations deleting these bridges and associated with hypocalcemia result in elevated CaSR constitutive activity. These results highlight the physiological importance of fine tuning the constitutive activity of G protein-coupled receptors.
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Affiliation(s)
- Shumin Ma
- 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, Hubei, China
| | - Xueliang Yin
- 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, Hubei, China
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, Cedex 5, France
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle (IGF), Université de Montpellier, CNRS, INSERM, Montpellier, Cedex 5, France.
| | - Ping Yi
- 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, Hubei, 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, Hubei, China.
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Constitutive Activity of Serotonin Receptor 6 Regulates Human Cerebral Organoids Formation and Depression-like Behaviors. Stem Cell Reports 2020; 16:75-88. [PMID: 33357407 PMCID: PMC7815944 DOI: 10.1016/j.stemcr.2020.11.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 11/25/2020] [Accepted: 11/25/2020] [Indexed: 01/13/2023] Open
Abstract
Serotonin receptor 6 (5-HT6R), a typical G protein-coupled receptor (GPCR) mainly expressed in the neurogenic area with constitutive activity, is of particular interest as a promising target for emotional impairment. Here, we found that 5-HT6R was highly expressed in human NSCs and activation of the receptor promoted self-renewal of human NSCs, and thus induced the expansion and folding of human cerebral organoids; dysfunction of receptor or inhibition of its constitutive activity resulted in the premature differentiation of NSCs, which ultimately depleted the NSC pool. The following mechanistic study revealed that EPAC-CREB signaling was involved in 5-HT6R regulation. Furthermore, we showed that mice with genetic deletion of 5-HT6R or knockin A268R mutant presented depression-like behaviors and impaired hippocampal neurogenesis for progressive decrease of the NSC pool. Thus, this study indicates that the modulation of 5-HT6R and its constitutive activity may provide a therapeutic alternative to alleviate depression. 5-HT6R regulates human neural stem cell proliferation The constitutive activity of 5-HT6R is essential for human neural stem cell's multipotency 5-HT6R modulates neurogenesis of human cerebral organoids Mice with reduced constitutive activity of 5-HT6R show depression-like behaviors
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A Systematic Review of Inverse Agonism at Adrenoceptor Subtypes. Cells 2020; 9:cells9091923. [PMID: 32825009 PMCID: PMC7564766 DOI: 10.3390/cells9091923] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/16/2020] [Accepted: 08/18/2020] [Indexed: 12/18/2022] Open
Abstract
As many, if not most, ligands at G protein-coupled receptor antagonists are inverse agonists, we systematically reviewed inverse agonism at the nine adrenoceptor subtypes. Except for β3-adrenoceptors, inverse agonism has been reported for each of the adrenoceptor subtypes, most often for β2-adrenoceptors, including endogenously expressed receptors in human tissues. As with other receptors, the detection and degree of inverse agonism depend on the cells and tissues under investigation, i.e., they are greatest when the model has a high intrinsic tone/constitutive activity for the response being studied. Accordingly, they may differ between parts of a tissue, for instance, atria vs. ventricles of the heart, and within a cell type, between cellular responses. The basal tone of endogenously expressed receptors is often low, leading to less consistent detection and a lesser extent of observed inverse agonism. Extent inverse agonism depends on specific molecular properties of a compound, but inverse agonism appears to be more common in certain chemical classes. While inverse agonism is a fascinating facet in attempts to mechanistically understand observed drug effects, we are skeptical whether an a priori definition of the extent of inverse agonism in the target product profile of a developmental candidate is a meaningful option in drug discovery and development.
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Akinaga J, García-Sáinz JA, S Pupo A. Updates in the function and regulation of α 1 -adrenoceptors. Br J Pharmacol 2019; 176:2343-2357. [PMID: 30740663 DOI: 10.1111/bph.14617] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 12/19/2018] [Accepted: 01/21/2019] [Indexed: 12/16/2022] Open
Abstract
α1 -Adrenoceptors are seven transmembrane domain GPCRs involved in numerous physiological functions controlled by the endogenous catecholamines, noradrenaline and adrenaline, and targeted by drugs useful in therapeutics. Three separate genes, whose products are named α1A -, α1B -, and α1D - adrenoceptors, encode these receptors. Although the existence of multiple α1 -adrenoceptors has been acknowledged for almost 25 years, the specific functions regulated by each subtype are still largely unknown. Despite the limited comprehension, the identification of a single class of subtype-selective ligands for the α1A - adrenoceptors, the so-called α-blockers for prostate dysfunction, has led to major improvement in therapeutics, demonstrating the need for continued efforts in the field. This review article surveys the tissue distribution of the three α1 -adrenoceptor subtypes in the cardiovascular system, genitourinary system, and CNS, highlighting the functions already identified as mediated by the predominant activation of specific subtypes. In addition, this review covers the recent advances in the understanding of the molecular mechanisms involved in the regulation of each of the α1 -adrenoceptor subtypes by phosphorylation and interaction with proteins involved in their desensitization and internalization. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.
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Affiliation(s)
- Juliana Akinaga
- Department of Pharmacology, Instituto de Biociências, UNESP, Botucatu, Brazil
| | - J Adolfo García-Sáinz
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - André S Pupo
- Department of Pharmacology, Instituto de Biociências, UNESP, Botucatu, Brazil
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Hamajima K, Hamamura K, Chen A, Yokota H, Mori H, Yo S, Kondo H, Tanaka K, Ishizuka K, Kodama D, Hirai T, Miyazawa K, Goto S, Togari A. Suppression of osteoclastogenesis via α2-adrenergic receptors. Biomed Rep 2018; 8:407-416. [PMID: 29725523 PMCID: PMC5920467 DOI: 10.3892/br.2018.1075] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 02/28/2018] [Indexed: 12/11/2022] Open
Abstract
The sympathetic nervous system is known to regulate osteoclast development. However, the involvement of α2-adrenergic receptors (α2-ARs) in osteoclastogenesis is not well understood. In the present study, their potential role in osteoclastogenesis was investigated. Guanabenz, clonidine and xylazine were used as agonists of α2-ARs, while yohimbine and idazoxan were employed as antagonists. Using RAW264.7 pre-osteoclast and primary bone marrow cells, the mRNA expression of the osteoclast-related genes nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), tartrate-resistant acid phosphatase (TRAP) and cathepsin K was evaluated following induction with receptor activator of nuclear factor κB ligand (RANKL). TRAP staining was also conducted to assess effects on osteoclastogenesis in mouse bone marrow cells in vitro. Administration of 5–20 µM guanabenz (P<0.01, for RANKL-only treatment), 20 µM clonidine (P<0.05, for RANKL-only treatment) and 20 µM xylazine (P<0.05, for RANKL-only treatment) attenuated RANKL-induced upregulation of NFATc1, TRAP and cathepsin K mRNA. Furthermore, the reductions in these mRNAs by 10 µM guanabenz and 20 µM clonidine in the presence of RANKL were attenuated by 20 µM yohimbine or idazoxan (P<0.05). The administration of 5–20 µM guanabenz (P<0.01, for RANKL-only treatment) and 10–20 µM clonidine (P<0.05, for RANKL-only treatment) also decreased the number of TRAP-positive multi-nucleated osteoclasts. Collectively, the present study demonstrates that α2-ARs may be involved in the regulation of osteoclastogenesis.
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Affiliation(s)
- Kosuke Hamajima
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan.,Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Kazunori Hamamura
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Andy Chen
- Department of Biomedical Engineering, Indiana University - Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Hiroki Yokota
- Department of Biomedical Engineering, Indiana University - Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Hironori Mori
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan.,Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Shoyoku Yo
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan.,Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Hisataka Kondo
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Kenjiro Tanaka
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Kyoko Ishizuka
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Daisuke Kodama
- Laboratory of Neuropharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Takao Hirai
- Laboratory of Medical Resources, School of Pharmacy, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Ken Miyazawa
- Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Shigemi Goto
- Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
| | - Akifumi Togari
- Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Aichi 464-8650, Japan
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The α-1 adrenoceptor (ADRA1A) genotype moderates the magnitude of acute cocaine-induced subjective effects in cocaine-dependent individuals. Pharmacogenet Genomics 2017; 26:428-35. [PMID: 27379509 DOI: 10.1097/fpc.0000000000000234] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES We examined whether a functional variant of the ADRA1A gene moderated cocaine-induced subjective effects in a group of cocaine-dependent individuals. METHODS This study was a within-participant, double-blind, placebo-controlled inpatient human laboratory evaluation of 65 nontreatment-seeking, cocaine-dependent [Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV)] individuals aged 18-55 years. Participants received both placebo (saline, IV) and cocaine (40 mg, IV), and subjective responses were assessed 15 min before receiving an infusion and at 5 min intervals for the subsequent 20 min. The rs1048101 variant of the α1A-adrenoceptor (ADRA1A) gene was genotyped and it was evaluated whether the Cys to Arg substitution at codon 347 in exon 2 (Cys347Arg) moderated the magnitude of the subjective effects produced by cocaine. RESULTS Thirty (46%) participants were found to have the major allele CC genotype and 35 (44%) carried at least one minor T-allele of rs1048101 (TT or TC genotype). Individuals with the CC genotype showed greater responses for 'desire' (P<0.0001), 'high' (P<0.0001), 'any drug effect' (P<0.0001), 'like cocaine' (P<0.0001), and 'likely to use cocaine if given access' (P<0.05) with experiment-wise significance. CONCLUSION This study indicates that the ADRA1A genotype could be used to identify individuals for whom acute cocaine exposure may be more rewarding and by inference may result in greater difficulty in establishing and/or maintaining abstinence from cocaine.
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Michel MC, Seifert R. Selectivity of pharmacological tools: implications for use in cell physiology. A review in the theme: Cell signaling: proteins, pathways and mechanisms. Am J Physiol Cell Physiol 2015; 308:C505-20. [PMID: 25631871 DOI: 10.1152/ajpcell.00389.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/24/2015] [Indexed: 01/08/2023]
Abstract
Pharmacological inhibitors are frequently used to identify the receptors, receptor subtypes, and associated signaling pathways involved in physiological cell responses. Based on the effects of such inhibitors conclusions are drawn about the involvement of their assumed target or lack thereof. While such inhibitors can be useful tools for a better physiological understanding, their uncritical use can lead to incorrect conclusions. This article reviews the concept of inhibitor selectivity and its implication for cell physiology. Specifically, we discuss the implications of using inhibitor vs. activator approaches, issues of direct vs. indirect pathway modulation, implications of inverse agonism and biased signaling, and those of orthosteric vs. allosteric, competitive vs. noncompetitive, and reversible vs. irreversible inhibition. Additional problems can result from inconsistent estimates of inhibitor potency and differences in potency between cell-free systems and intact cells. These concepts are illustrated by several examples of inhibitors displaying affinity for related but distinct targets or even unrelated targets. Of note, many of the issues being addressed are also applicable to genetic inhibition strategies. The main practical conclusion following from these concepts is that investigators should be critical in the choice of inhibitor, its concentrations, and its mode of application. When this advice is adhered to, small-molecule pharmacological inhibitors can be important experimental tools in the hand of physiologists.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany; and
| | - Roland Seifert
- Department of Pharmacology, Hannover Medical School, Hannover, Germany
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Zhang B, Albaker A, Plouffe B, Lefebvre C, Tiberi M. Constitutive activities and inverse agonism in dopamine receptors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 70:175-214. [PMID: 24931197 DOI: 10.1016/b978-0-12-417197-8.00007-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The concept of activation in the absence of agonists has been demonstrated for many GPCRs and is now solidified as one of the principal aspects of GPCR signaling. In this chapter, we review how dopamine receptors demonstrate this ability. Although difficult to prove in vivo due to the presence of endogenous dopamine and lack of subtype-selective inverse agonists and "pure" antagonists (neutral ligands), in vitro assays such as measuring intracellular cAMP, [(35)S]GTPγS binding, and [(3)H]thymidine incorporation have uncovered the constitutive activation of D1- and D2-class receptors. Nevertheless, because of limited and inconsistent findings, the existence of constitutive activity for D2-class receptors is currently not well established. Mutagenesis studies have shown that basal signaling, notably by D1-class receptors, is governed by the collective contributions of transmembrane domains and extracellular/intracellular loops, such as the third extracellular loop, the third intracellular loop, and C-terminal tail. Furthermore, constitutive activities of D1-class receptors are subjected to regulation by kinases. Among the dopamine receptor family, the D5 receptor subtype exhibits a higher basal signaling and bears resemblance to constitutively active mutant forms of GPCRs. The presence of its constitutive activity in vivo and its pathophysiological relevance, with a brief mention of other subtypes, are also discussed.
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Affiliation(s)
- Boyang Zhang
- Ottawa Hospital Research Institute (Neuroscience Program), Ottawa, Ontario, Canada; Departments of Medicine, Cellular & Molecular Medicine, Psychiatry, University of Ottawa, Ottawa, Ontario, Canada
| | - Awatif Albaker
- Ottawa Hospital Research Institute (Neuroscience Program), Ottawa, Ontario, Canada; Departments of Medicine, Cellular & Molecular Medicine, Psychiatry, University of Ottawa, Ottawa, Ontario, Canada
| | - Bianca Plouffe
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada; Institut de recherche en immunologie, cancer, Montréal, Québec, Canada
| | - Caroline Lefebvre
- Ottawa Hospital Research Institute (Neuroscience Program), Ottawa, Ontario, Canada; Departments of Medicine, Cellular & Molecular Medicine, Psychiatry, University of Ottawa, Ottawa, Ontario, Canada
| | - Mario Tiberi
- Ottawa Hospital Research Institute (Neuroscience Program), Ottawa, Ontario, Canada; Departments of Medicine, Cellular & Molecular Medicine, Psychiatry, University of Ottawa, Ottawa, Ontario, Canada.
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Functional analysis of human D1 and D5 dopaminergic G protein-coupled receptors: lessons from mutagenesis of a conserved serine residue in the cytosolic end of transmembrane region 6. Methods Mol Biol 2013; 964:141-80. [PMID: 23296783 DOI: 10.1007/978-1-62703-251-3_10] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In mammals, dopamine G protein-coupled receptors (GPCR) are segregated into two categories: D1-like (D1R and D5R) and D2-like (D2R(short), D2R(long), D3R, and D4R) subtypes. D1R and D5R are primarily coupled to stimulatory heterotrimeric GTP-binding proteins (Gs/olf) leading to activation of adenylyl cyclase and production of intracellular cAMP. D1R and D5R share high level of amino acid identity in transmembrane (TM) regions. Yet these two GPCR subtypes display distinct ligand binding and G protein coupling properties. In fact, our studies suggest that functional properties reported for constitutively active mutants of GPCRs (e.g., increased basal activity, higher agonist affinity and intrinsic activity) are also observed in cells expressing wild type D5R when compared with wild type D1R. Herein, we describe an experimental method based on mutagenesis and transfection of human embryonic kidney 293 (HEK293) cells to explore the molecular mechanisms regulating ligand affinity, agonist-independent and dependent activity of D1R and D5R. We will demonstrate how to mutate one conserved residue in the cytosolic end of TM6 of D1R (Ser263) and D5R (Ser287) by modifying two or three nucleotides in the cDNA of human D1-like receptors. Genetically modified D1R and D5R cDNAs are prepared using a polymerase chain reaction method, propagated in E. coli, purified and mutations confirmed by DNA sequencing. Receptor expression constructs are transfected into HEK293 cells cultured in vitro at 37°C in 5% CO(2) environment and used in radioligand binding and whole cAMP assays. In this study, we will test the effect of S263A/G/D and S287A/G/D mutations on ligand binding and DA-dependent activation of D1R and D5R.
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Hudson BD, Tikhonova IG, Pandey SK, Ulven T, Milligan G. Extracellular ionic locks determine variation in constitutive activity and ligand potency between species orthologs of the free fatty acid receptors FFA2 and FFA3. J Biol Chem 2012; 287:41195-209. [PMID: 23066016 PMCID: PMC3510819 DOI: 10.1074/jbc.m112.396259] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Free fatty acid receptors 2 and 3 (FFA2 and FFA3) are G protein-coupled receptors for short chain free fatty acids (SCFAs). They respond to the same set of endogenous ligands but with distinct rank-order of potency such that acetate (C2) has been described as FFA2-selective, whereas propionate (C3) is non-selective. Although C2 was confirmed to be selective for human FFA2 over FFA3, this ligand was not selective between the mouse orthologs. Moreover, although C3 was indeed not selective between the human orthologs, it displayed clear selectivity for mouse FFA3 over mouse FFA2. This altered selectivity to C2 and C3 resulted from broad differences in SCFAs potency at the mouse orthologs. In studies to define the molecular basis for these observations, marked variation in ligand-independent constitutive activity was identified using a [35S]GTPγS assay. The orthologs with higher potency for the SCFAs, human FFA2 and mouse FFA3, displayed high constitutive activity in this assay, whereas the orthologs with lower potency for the agonist ligands, mouse FFA2 and human FFA3, did not. Sequence alignments of the second extracellular loop identified single negatively charged residues in FFA2 and FFA3 not conserved between species and predicted to form ionic lock interactions with arginine residues within the FFA2 or FFA3 agonist binding pocket to regulate constitutive activity and SCFA potency. Reciprocal mutation of these residues between species orthologs resulted in the induction (or repression) of constitutive activity and in most cases also yielded corresponding changes in SCFA potency.
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Affiliation(s)
- Brian D Hudson
- Molecular Pharmacology Group, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Up-Regulation of α
1a
and α
1d
-Adrenoceptors in the Prostate by Administration of Subtype Selective α
1
-Adrenoceptor Antagonist Tamsulosin in Patients With Benign Prostatic Hyperplasia. J Urol 2011; 186:1530-6. [DOI: 10.1016/j.juro.2011.05.048] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Indexed: 11/19/2022]
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Plouffe B, Yang X, Tiberi M. The third intracellular loop of D1 and D5 dopaminergic receptors dictates their subtype-specific PKC-induced sensitization and desensitization in a receptor conformation-dependent manner. Cell Signal 2011; 24:106-18. [PMID: 21893192 DOI: 10.1016/j.cellsig.2011.08.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/05/2011] [Accepted: 08/17/2011] [Indexed: 01/11/2023]
Abstract
We previously showed that phorbol-12-myristate-13-acetate (PMA) mediates a robust PKC-dependent sensitization and desensitization of the highly homologous human Gs protein and adenylyl cyclase (AC)-linked D1 (hD1R) and D5 (hD5R) dopaminergic receptors, respectively. Here, we demonstrate using forskolin-mediated AC stimulation that PMA-mediated hD1R sensitization and hD5R desensitization is not associated with changes in AC activity. We next employed a series of chimeric hD1R and hD5R to delineate the underlying structural determinants dictating the subtype-specific regulation of human D1-like receptors by PMA. We first used chimeric receptors in which the whole terminal region (TR) spanning from the extracellular face of transmembrane domain 6 to the end of cytoplasmic tail (CT) or CT alone were exchanged between hD1R and hD5R. CT and TR swaps lead to chimeric hD1R and hD5R retaining PMA-induced sensitization and desensitization of wild type parent receptors. In striking contrast, hD1R sensitization and hD5R desensitization mediated by PMA are correspondingly switched to PMA-induced receptor desensitization and sensitization following the IL3 swap between hD1R and hD5R. Cell treatment with the PKC blocker, Gö6983, inhibits PMA-induced regulation of these chimeric receptors in a similar fashion to wild type receptors. Further studies with chimeras constructed by exchanging IL3 and TR show that PMA-induced regulation of these chimeras remains fully switched relative to their respective wild type parent receptor. Interestingly, results obtained with the exchange of IL3 and TR also reveal that the D1-like subtype-specific regulation by PMA, while fully dictated by IL3, can be modulated in a receptor conformation-dependent manner. Overall, our results strongly suggest that IL3 is the critical determinant underlying the subtype-specific regulation of human D1-like receptor responsiveness by PKC.
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Affiliation(s)
- Bianca Plouffe
- Ottawa Hospital Research Institute, Department of Medicine, University of Ottawa, Ottawa, ON, Canada
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Melief EJ, Miyatake M, Carroll FI, Béguin C, Carlezon WA, Cohen BM, Grimwood S, Mitch CH, Rorick-Kehn L, Chavkin C. Duration of action of a broad range of selective κ-opioid receptor antagonists is positively correlated with c-Jun N-terminal kinase-1 activation. Mol Pharmacol 2011; 80:920-9. [PMID: 21832171 DOI: 10.1124/mol.111.074195] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The κ-opioid receptor is a widely expressed G-protein-coupled receptor that has been implicated in biological responses to pain, stress, anxiety, and depression, and its potential as a therapeutic target in these syndromes is becoming increasingly apparent. However, the prototypical selective κ-opioid antagonists have very long durations of action that have been attributed to c-Jun N-terminal kinase (JNK) 1 activation in vivo. To test generality of this proposed noncompetitive mechanism, we used C57BL/6 wild type mice to determine the durations of antagonist action of novel κ-opioid receptor ligands and examined their efficacies for JNK1 activation compared with conventional competitive antagonists. Of the 12 compounds tested, 5 had long durations of action that positively correlated with JNK activation: RTI-5989-97 [(3S)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-2-methyl-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-194 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylbutyl]-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-241 [(3R)-7-hydroxy-N-[(1S)-1-{[(3R,4R)-4-(3-methoxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxamide)], nor-binaltorphimine (nor-BNI); and (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic). Seven had short durations of action and did not increase phospho-JNK-ir: RTI-5989-212[(3R)-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], RTI-5989-240 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethylpiperidin-1-yl]methyl}-(2-methylpropyl]-3-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], JSPA0658 [(S)-3-fluoro-4-(4-((2-(3,5-dimethylphenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], JSPA071B [(S)-3-fluoro-4-(4-((2-(3,5-bis(trifluoromethyl)phenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide]. PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], FP3FBZ [(S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], and naloxone. After long-acting antagonist treatment, pJNK-ir did not increase in mice lacking the κ-opioid receptor; increased pJNK-ir returned to baseline by 48 h after treatment; and a second challenge with nor-BNI 72 h after the first did not increase pJNK-ir. Long-lasting antagonism and increased phospho-JNK-ir were not seen in animals lacking the JNK1 isoform. These results support the hypothesis that the duration of action of small molecule κ-opioid receptor antagonists in vivo is determined by their efficacy in activating JNK1 and that persistent inactivation of the κ-receptor does not require sustained JNK activation.
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Affiliation(s)
- Erica J Melief
- Department of Pharmacology, University of Washington School of Medicine, Seattle WA 98195-7280, USA
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Multiscale computational methods for mapping conformational ensembles of G-protein-coupled receptors. COMPUTATIONAL CHEMISTRY METHODS IN STRUCTURAL BIOLOGY 2011; 85:253-80. [DOI: 10.1016/b978-0-12-386485-7.00007-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Blais V, Bounif N, Dubé F. Characterization of a novel octopamine receptor expressed in the surf clam Spisula solidissima. Gen Comp Endocrinol 2010; 167:215-27. [PMID: 20302871 DOI: 10.1016/j.ygcen.2010.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 01/18/2010] [Accepted: 03/11/2010] [Indexed: 10/19/2022]
Abstract
We have cloned and sequenced a cDNA from the surf clam (Spisula solidissima, a pelecypod mollusc) that encodes an octopamine receptor which we have named Spi-OAR. The sequence of Spi-OAR shares many similarities with two Aplysia and three Drosophila octopamine receptors belonging to a sub-group of beta-adrenergic-like octopamine receptors. Using an expression vector and transient transfections of Spi-OAR into HEK 293 cells, we observed an increase of cAMP upon addition of octopamine and, to a lesser extent, of tyramine, but not after addition of dopamine, serotonin, or histamine. Using a battery of known agonists and antagonists for octopamine receptors, we observed a rather unique pharmacological profile for Spi-OAR through measurements of cAMP. Spi-OAR exhibited some constitutive activity in HEK 293 cells and no Ca(2+) responses could be detected following addition of octopamine to Spi-OAR-transfected cells. RT-PCR analysis revealed ubiquitous expression of Spi-OAR mRNA in all adult tissues, oocytes and early embryos examined. While addition of serotonin to isolated clam oocytes resulted in meiotic activation, similar additions of octopamine had no effect, suggesting that its potential role in clam reproductive physiology differs significantly from that of serotonin. This work identifies Spi-OAR as a novel mollusc octopamine receptor closely related to other invertebrate beta-adrenergic-like octopamine receptors, with possible reproductive and other physiological functions. This initial characterization of Spi-OAR makes possible further investigations and comparisons with more studied and familiar insect or gastropod mollusc octopamine receptors.
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Affiliation(s)
- Véronique Blais
- CR-CHUM (Centre de recherche du Centre Hospitalier de l'Université de Montréal), Département d'obstétrique-gynécologie, Hôpital Saint-Luc, 264 René-Lévesque E., Montréal, Québec, Canada H2X 1P1
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D'Aoust JP, Tiberi M. Role of the extracellular amino terminus and first membrane-spanning helix of dopamine D1 and D5 receptors in shaping ligand selectivity and efficacy. Cell Signal 2010; 22:106-16. [DOI: 10.1016/j.cellsig.2009.09.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 09/14/2009] [Indexed: 01/28/2023]
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Plouffe B, D'Aoust JP, Laquerre V, Liang B, Tiberi M. Probing the constitutive activity among dopamine D1 and D5 receptors and their mutants. Methods Enzymol 2010; 484:295-328. [PMID: 21036239 DOI: 10.1016/b978-0-12-381298-8.00016-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dopamine D1 and D5 receptors are prototypical cell-surface seven-transmembrane (TM) G protein-coupled receptors (GPCRs) mediating elevation of intracellular cAMP levels. The high level of constitutive activity of D5 receptor mediating intracellular cAMP production is one of the functional hallmarks distinguishing the closely related D1-like dopaminergic subtypes (D1 and D5). D1-like subtypes share over 80% identity within their TM regions. Thus, D1 and D5 receptors can serve as unparalleled and useful molecular tools to gain structural and mechanistic insights into subtype-specific determinants regulating GPCR constitutive activation and inverse agonism. A method has been developed that relies on the use of transfected human embryonic kidney 293 cells with wild-type (WT), epitope-tagged, chimeric, truncated, and mutant forms of mammalian D1 and D5 receptors using a modified DNA and calcium phosphate precipitation procedure. Receptor expression levels are quantified by a radioligand binding using [(3)H]-SCH23390, a D1-like selective drug. Regulation of ligand-independent and dependent activity of WT and mutated D1 and D5 receptors is determined by whole cell cAMP assays using metabolic [(3)H]-adenine labeling and sequential purification radiolabeled nucleotides over Dowex and alumina resin columns. Results on the regulation of D1 and D5 constitutive activity are presented here. Our studies indicate that dopamine-mediated D5 receptor stimulation in a dose-dependent manner is not always detectable, suggesting that D5 receptors can exist in a "locked" constitutively activated state. This "locked" constitutively active state of D5 receptor is not linked to aberrant high receptor expression levels or cell behavior, as D1 receptor function remains essentially unchanged in these cells. In fact, we show that phorbol ester treatment of cells harboring "locked" constitutively active D5 receptors abrogates constitutive activation of D5R to allow its stimulation by dopamine in a dose-dependent manner.
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Affiliation(s)
- Bianca Plouffe
- Ottawa Hospital Research Institute (Neurosciences), Department of Medicine, University of Ottawa, Ontario, Canada
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α(1D)-Adrenergic receptors constitutive activity and reduced expression at the plasma membrane. Methods Enzymol 2010; 484:109-25. [PMID: 21036229 DOI: 10.1016/b978-0-12-381298-8.00006-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Adrenergic receptors are a heterogeneous family of the G protein-coupled receptors that mediate the actions of adrenaline and noradrenaline. Adrenergic receptors comprise three subfamilies (α(1), α(2), and β, with three members each) and the α(1D)-adrenergic receptor is one of the members of the α(1) subfamily with some interesting traits. The α(1D)-adrenergic receptor is difficult to express, seems predominantly located intracellularly, and exhibits constitutive activity. In this chapter, we will describe in detail the conditions and procedures used to determine changes in intracellular free calcium concentration which has been instrumental to define the constitutive activity of these receptors. Taking advantage of the fact that truncation of the first 79 amino acids of α(1D)-adrenergic receptors markedly increased their membrane expression, we were able to show that constitutive activity is present in receptors truncated at the amino and carboxyl termini, which indicates that such domains are dispensable for this action. Constitutive activity could be observed in cells expressing either the rat or human α(1D)-adrenergic receptor orthologs. Such constitutive activity has been observed in native rat arteries and we will discuss the possible functional implications that it might have in the regulation of blood pressure.
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Lei B, Morris DP, Smith MP, Schwinn DA. Lipid rafts constrain basal alpha(1A)-adrenergic receptor signaling by maintaining receptor in an inactive conformation. Cell Signal 2009; 21:1532-9. [PMID: 19520158 DOI: 10.1016/j.cellsig.2009.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/20/2009] [Accepted: 06/01/2009] [Indexed: 12/16/2022]
Abstract
We have reported that the alpha(1A)-adrenergic receptor (alpha(1A)AR) in rat-1 fibroblasts is a lipid raft protein. Here we examined whether disrupting lipid rafts by methyl-beta-cyclodextrin (MCD) sequestration of cholesterol affects alpha(1A)AR signaling. Unexpectedly, MCD increased alpha(1A)AR-dependent basal inositol phosphate formation and p38 mitogen-activated protein kinase activation in a cholesterol-dependent manner. It also initiated internalization of surface alpha(1A)AR, which was partially blocked by receptor inhibition. Binding assays revealed MCD-mediated increases in receptor agonist affinity as well as reciprocal decreases in inverse agonist affinity, a behavior that is usually interpreted as a shift toward the active receptor conformation. In untreated cells a fraction of the receptor was found to be present in preassociated receptor/G protein complexes, which rapidly dissociate upon receptor stimulation. Consistent with MCD-induced signaling, raft disruption resulted in an increase in receptor/G protein complexes. These results strongly suggest that lipid rafts constrain basal alpha(1A)AR activity; however, preassembled receptor/G protein complexes could still provide a mechanism for accelerating alpha(1A)AR signaling following stimulation.
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Affiliation(s)
- Beilei Lei
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA.
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Pro- and anti-apoptotic dual functions of the C5a receptor: involvement of regulator of G protein signaling 3 and extracellular signal-regulated kinase. J Transl Med 2009; 89:676-94. [PMID: 19333232 PMCID: PMC7503222 DOI: 10.1038/labinvest.2009.27] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
When apoptosis is initiated by manganese (II) loading, hyperthermia or thapsigargin treatment, human HL-60 and AsPC-1 cells initiate de novo synthesis of the C5a receptor (C5aR) and generation of its ligand, the ribosomal protein S19 (RP S19) homodimer. The ligand-receptor interaction, in an autocrine/paracrine fashion, promotes apoptosis, which can be bypassed by exogenous administration of C5a, another ligand. The proapoptotic function of the RP S19 dimer is reproduced by a C5a/RPS19 chimera that contains the body of C5a and the C-terminal region (Ile134-His145) of RP S19. The RP S19 dimer or C5a/RPS19 and C5a inversely regulate the expression of Regulator of G protein Signaling 3 (RGS3) gene in the apoptosis-initiated cells. Namely, the RP S19-type proteins upregulate RGS3 expression, whereas the C5a reduce it. Transformation of HL-60 cells to overexpress RGS3 promotes apoptosis in association with the downregulation of the Extracellular signal-Regulated Kinase (ERK) signal, and vice versa in the RGS3 knocked-down cells. Consistent with this result, an inhibitor of ERK phosphorylation effectively enhances the apoptotic rate in wild-type HL-60 cells. Moreover, a dominant negative effect on the RP S19 dimer production encourages apoptosis-initiated HL-60 cells with a longer lifespan in mouse than the natural effect. Our data indicate that, in apoptosis-initiated cells, the ligand-dependent C5aR-mediated dual signal affects the fate of cells, either apoptosis execution or survival, through regulation of RGS3 gene expression and subsequent modulation of ERK signal.
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Huber T, Menon S, Sakmar TP. Structural basis for ligand binding and specificity in adrenergic receptors: implications for GPCR-targeted drug discovery. Biochemistry 2008; 47:11013-23. [PMID: 18821775 DOI: 10.1021/bi800891r] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Crystal structures of engineered human beta 2-adrenergic receptors (ARs) in complex with an inverse agonist ligand, carazolol, provide three-dimensional snapshots of the disposition of seven transmembrane helices and the ligand-binding site of an important G protein-coupled receptor (GPCR). As expected, beta 2-AR shares substantial structural similarities with rhodopsin, the dim-light photoreceptor of the rod cell. However, although carazolol and the 11- cis-retinylidene moiety of rhodopsin are situated in the same general binding pocket, the second extracellular (E2) loop structures are quite distinct. E2 in rhodopsin shows beta-sheet structure and forms part of the chromophore-binding site. In the beta 2-AR, E2 is alpha-helical and seems to be distinct from the receptor's active site, allowing a potential entry pathway for diffusible ligands. The structures, together with extensive structure-activity relationship (SAR) data from earlier studies, provide insight about possible structural determinants of ligand specificity and how the binding of agonist ligands might alter receptor conformation. We review key features of the new beta 2-AR structures in the context of recent complementary work on the conformational dynamics of GPCRs. We also report 600 ns molecular dynamics simulations that quantified beta 2-AR receptor mobility in a membrane bilayer environment and show how the binding of an agonist ligand, adrenaline (epinephrine), causes conformational changes to the ligand-binding pocket and neighboring helices.
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Affiliation(s)
- Thomas Huber
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA.
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Guo J, Williams DJ, Puhl HL, Ikeda SR. Inhibition of N-Type Calcium Channels by Activation of GPR35, an Orphan Receptor, Heterologously Expressed in Rat Sympathetic Neurons. J Pharmacol Exp Ther 2007; 324:342-51. [DOI: 10.1124/jpet.107.127266] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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