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Graßl F, Bock L, Huete-Huerta González Á, Schiller M, Gmeiner P, König J, Fromm MF, Hübner H, Heinrich MR. Exploring Structural Determinants of Bias among D4 Subtype-Selective Dopamine Receptor Agonists. J Med Chem 2023. [PMID: 37450764 DOI: 10.1021/acs.jmedchem.3c00537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
The high affinity dopamine D4 receptor ligand APH199 and derivatives thereof exhibit bias toward the Gi signaling pathway over β-arrestin recruitment compared to quinpirole. Based on APH199, two novel groups of D4 subtype selective ligands were designed and evaluated, in which the original benzyl phenylsemicarbazide substructure was replaced by either a biphenylmethyl urea or a biphenyl urea moiety. Functional assays revealed a range of different bias profiles among the newly synthesized compounds, namely, with regard to efficacy, potency, and GRK2 dependency, in which bias factors range from 1 to over 300 and activation from 15% to over 98% compared to quinpirole. These observations demonstrate that within bias, an even more precise tuning toward a particular profile is possible, which─in a general sense─could become an important aspect in future drug development. Docking studies enabled further insight into the role of the ECL2 and the EPB in the emergence of bias, thereby taking advantage of the diversity of functionally selective D4 agonists now available.
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Affiliation(s)
- Fabian Graßl
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Leonard Bock
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Álvaro Huete-Huerta González
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Martin Schiller
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Jörg König
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Martin F Fromm
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Harald Hübner
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Markus R Heinrich
- Department of Chemistry and Pharmacy, Pharmaceutical Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
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2
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Investigating the ligand agonism and antagonism at the D 2long receptor by dynamic mass redistribution. Sci Rep 2022; 12:9637. [PMID: 35688965 PMCID: PMC9187652 DOI: 10.1038/s41598-022-14311-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 06/06/2022] [Indexed: 11/09/2022] Open
Abstract
The signalling of the D2 receptor (D2R), a G protein-coupled receptor (GPCR), is a complex process consisting of various components. For the screening of D2R ligands, methods quantifying distinct second messengers such as cAMP or the interaction of the receptor with β-arrestin, are commonly employed. In contrast, a label-free biosensor technology like dynamic mass redistribution (DMR), where it is mostly unknown how the individual signalling pathways contribute to the DMR signal, provides a holistic readout of the complex cellular response. In this study, we report the successful application of the DMR technology to CHO-K1 cells stably expressing the human dopamine D2long receptor. In real-time kinetic experiments, studies of D2R reference compounds yielded results for agonists and antagonists that were consistent with those obtained by conventional methods and also allowed a discrimination between partial and full agonists. Furthermore, investigations on the signalling pathway in CHO-K1 hD2longR cells identified the Gαi/o protein as the main proximal trigger of the observed DMR response. The present study has shown that the DMR technology is a valuable method for the characterisation of putative new ligands and, due to its label-free nature, suggests its use for deorphanisation studies of GPCRs.
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3
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Peverelli E, Treppiedi D, Mangili F, Catalano R, Spada A, Mantovani G. Drug resistance in pituitary tumours: from cell membrane to intracellular signalling. Nat Rev Endocrinol 2021; 17:560-571. [PMID: 34194011 DOI: 10.1038/s41574-021-00514-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/19/2021] [Indexed: 02/06/2023]
Abstract
The pharmacological treatment of pituitary tumours is based on the use of stable analogues of somatostatin and dopamine. The analogues bind to somatostatin receptor types 2 and 5 (SST2 and SST5) and dopamine receptor type 2 (DRD2), respectively, and generate signal transduction cascades in cancerous pituitary cells that culminate in the inhibition of hormone secretion, cell growth and invasion. Drug resistance occurs in a subset of patients and can involve different steps at different stages, such as following receptor activation by the agonist or during the final biological responses. Although the expression of somatostatin and dopamine receptors in cancer cells is a prerequisite for these drugs to reach a biological effect, their presence does not guarantee the success of the therapy. Successful therapy also requires the proper functioning of the machinery of signal transduction and the finely tuned regulation of receptor desensitization, internalization and intracellular trafficking. The present Review provides an updated overview of the molecular factors underlying the pharmacological resistance of pituitary tumours. The Review discusses the experimental evidence that supports a role for receptors and intracellular proteins in the function of SSTs and DRD2 and their clinical importance.
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Affiliation(s)
- Erika Peverelli
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy.
| | - Donatella Treppiedi
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy
| | - Federica Mangili
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy
| | - Rosa Catalano
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy
- PhD Program in Endocrinological Sciences, Sapienza University of Rome, Rome, Italy
| | - Anna Spada
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy
| | - Giovanna Mantovani
- University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Endocrinology Unit, Milan, Italy
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4
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Ullmann T, Gienger M, Budzinski J, Hellmann J, Hübner H, Gmeiner P, Weikert D. Homobivalent Dopamine D 2 Receptor Ligands Modulate the Dynamic Equilibrium of D 2 Monomers and Homo- and Heterodimers. ACS Chem Biol 2021; 16:371-379. [PMID: 33435665 DOI: 10.1021/acschembio.0c00895] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Dopamine D2 receptors (D2Rs) are major targets in the treatment of psychiatric and neurodegenerative diseases. As with many other G protein-coupled receptors (GPCRs), D2Rs interact within the cellular membrane, leading to a transient receptor homo- or heterodimerization. These interactions are known to alter ligand binding, signaling, and receptor trafficking. Bivalent ligands are ideally suited to target GPCR dimers and are composed of two pharmacophores connected by a spacer element. If properly designed, bivalent ligands are able to engange the two orthosteric binding sites of a GPCR dimer simultaneously. Taking advantage of previously developed ligands for heterodimers of D2R and the neurotensin receptor 1 (NTSR1), we synthesized homobivalent ligands targeting D2R. Employing bioluminescence resonance energy transfer, we found that the bivalent ligands 3b and 4b comprising a 92-atom spacer are able to foster D2R-homodimerization while simultaneously reducing interactions of D2R with NTSR1. Both receptors are coexpressed in the central nervous system and involved in important physiological processes. The newly developed bivalent ligands are excellent tools to further understand the pharmacological consequences of D2R homo- and heterodimerization. Not limited to the dopaminergic system, modifying class A GPCRs' dynamic equilibrium between monomers, homomers, and heteromers with bivalent ligands may represent a novel pharmacological concept paving the way toward innovative drugs.
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Affiliation(s)
- Tamara Ullmann
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Marie Gienger
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Julian Budzinski
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Jan Hellmann
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Harald Hübner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
| | - Dorothee Weikert
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 10, 91058 Erlangen, Germany
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5
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Uzuneser TC, Weiss EM, Dahlmanns J, Kalinichenko LS, Amato D, Kornhuber J, Alzheimer C, Hellmann J, Kaindl J, Hübner H, Löber S, Gmeiner P, Grömer TW, Müller CP. Presynaptic vesicular accumulation is required for antipsychotic efficacy in psychotic-like rats. J Psychopharmacol 2021; 35:65-77. [PMID: 33274688 PMCID: PMC7770212 DOI: 10.1177/0269881120965908] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND The therapeutic effects of antipsychotic drugs (APDs) are mainly attributed to their postsynaptic inhibitory functions on the dopamine D2 receptor, which, however, cannot explain the delayed onset of full therapeutic efficacy. It was previously shown that APDs accumulate in presynaptic vesicles during chronic treatment and are released like neurotransmitters in an activity-dependent manner triggering an auto-inhibitory feedback mechanism. Although closely mirroring therapeutic action onset, the functional consequence of the APD accumulation process remained unclear. AIMS Here we tested whether the accumulation of the APD haloperidol (HAL) is required for full therapeutic action in psychotic-like rats. METHODS We designed a HAL analog compound (HAL-F), which lacks the accumulation property of HAL, but retains its postsynaptic inhibitory action on dopamine D2 receptors. RESULTS/OUTCOMES By perfusing LysoTracker fluorophore-stained cultured hippocampal neurons, we confirmed the accumulation of HAL and the non-accumulation of HAL-F. In an amphetamine hypersensitization psychosis-like model in rats, we found that subchronic intracerebroventricularly delivered HAL (0.1 mg/kg/day), but not HAL-F (0.3-1.5 mg/kg/day), attenuates psychotic-like behavior in rats. CONCLUSIONS/INTERPRETATION These findings suggest the presynaptic accumulation of HAL may serve as an essential prerequisite for its full antipsychotic action and may explain the time course of APD action. Targeting accumulation properties of APDs may, thus, become a new strategy to improve APD action.
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Affiliation(s)
- Taygun C Uzuneser
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany,Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Eva-Maria Weiss
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Jana Dahlmanns
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Liubov S Kalinichenko
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Davide Amato
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany,Department of Neuroscience, Medical University of South Carolina, Charleston, USA
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Christian Alzheimer
- Institute of Physiology and Pathophysiology, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Jan Hellmann
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Jonas Kaindl
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Harald Hübner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Stefan Löber
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Teja W Grömer
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany
| | - Christian P Müller
- Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany,Christian P Müller, Department of Psychiatry and Psychotherapy, University Clinic, Friedrich-Alexander University of Erlangen-Nuremberg, Schwabachanlage 6, Erlangen 91054, Germany.
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6
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Gienger M, Hübner H, Löber S, König B, Gmeiner P. Structure-based development of caged dopamine D 2/D 3 receptor antagonists. Sci Rep 2020; 10:829. [PMID: 31965029 PMCID: PMC6972920 DOI: 10.1038/s41598-020-57770-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/06/2020] [Indexed: 12/17/2022] Open
Abstract
Dopamine is a neurotransmitter of great physiological relevance. Disorders in dopaminergic signal transduction are associated with psychiatric and neurological pathologies such as Parkinson’s disease, schizophrenia and substance abuse. Therefore, a detailed understanding of dopaminergic neurotransmission may provide access to novel therapeutic strategies for the treatment of these diseases. Caged compounds with photoremovable groups represent molecular tools to investigate a biological target with high spatiotemporal resolution. Based on the crystal structure of the D3 receptor in complex with eticlopride, we have developed caged D2/D3 receptor ligands by rational design. We initially found that eticlopride, a widely used D2/D3 receptor antagonist, was photolabile and therefore is not suitable for caging. Subtle structural modification of the pharmacophore led us to the photostable antagonist dechloroeticlopride, which was chemically transformed into caged ligands. Among those, the 2-nitrobenzyl derivative 4 (MG307) showed excellent photochemical stability, pharmacological behavior and decaging properties when interacting with dopamine receptor-expressing cells.
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Affiliation(s)
- Marie Gienger
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058, Erlangen, Germany
| | - Harald Hübner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058, Erlangen, Germany
| | - Stefan Löber
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058, Erlangen, Germany
| | - Burkhard König
- Institute of Organic Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Medicinal Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Straße 10, 91058, Erlangen, Germany.
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7
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Abstract
Background Impulsive aggression (IA) is considered a maladaptive form of aggression that is reactive and overt and occurs outside of the acceptable social context. Many children and adolescents with attention-deficit/hyperactivity disorder (ADHD) display clinically significant aggression, with the predominant subtype being IA. However, there is currently no Food and Drug Administration-approved medication specifically to treat IA. The pathophysiology of IA is not fully understood, although it has been suggested to include the dopamine, norepinephrine, and serotonin systems. Methods SPN-810 (extended-release molindone) is being developed for the novel indication of IA and is currently being studied in patients treated for ADHD. Molindone is an indole derivative and a dopamine D2 receptor antagonist. Results The in vitro pharmacological studies described in the current manuscript demonstrate that the active substance molindone (SPN-810M) is a potent antagonist for the dopamine receptors, D2S and D2L, and the serotonin receptor, 5-HT2B, at therapeutic concentrations. The in vitro studies further demonstrate that the antagonist effect of SPN-810M is due to the parent drug and not the metabolites, and that the antagonism is not affected by the presence of norepinephrine or dopamine neurotransmitters. In addition, studies investigating the potential differential effects of the enantiomers of SPN-810M have demonstrated that the R(−) enantiomer is more potent than S(+), showing greater regulatory effect on D2S and D2L receptors. Conclusion Overall, the results of the in vitro SPN-810M pharmacological studies provide some insight into how SPN-810M modulates the serotonin and dopamine pathways that play a role in IA.
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Affiliation(s)
- Chungping Yu
- Preclinical DMPK and Pharmacology, Supernus Pharmaceuticals, Inc., Rockville, MD, USA,
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8
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Kasai RS, Ito SV, Awane RM, Fujiwara TK, Kusumi A. The Class-A GPCR Dopamine D2 Receptor Forms Transient Dimers Stabilized by Agonists: Detection by Single-Molecule Tracking. Cell Biochem Biophys 2017; 76:29-37. [PMID: 29116599 PMCID: PMC5913388 DOI: 10.1007/s12013-017-0829-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 09/18/2017] [Indexed: 01/06/2023]
Abstract
Whether class-A G-protein coupled receptors (GPCRs) exist and work as monomers or dimers has drawn extensive attention. A class-A GPCR dopamine D2 receptor (D2R) is involved in many physiological and pathological processes and diseases, indicating its critical role in proper functioning of neuronal circuits. In particular, D2R homodimers might play key roles in schizophrenia development and amphetamine-induced psychosis. Here, using single-molecule imaging, we directly tracked single D2R molecules in the plasma membrane at a physiological temperature of 37 °C, and unequivocally determined that D2R forms transient dimers with a lifetime of 68 ms in its resting state. Agonist addition prolonged the dimer lifetime by a factor of ~1.5, suggesting the possibility that transient dimers might be involved in signaling.
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Affiliation(s)
- Rinshi S Kasai
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan
| | - Shuichi V Ito
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan
| | - Ryo M Awane
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan
| | - Takahiro K Fujiwara
- Center for Meso-Bio Single-Molecule Imaging (CeMI), Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, 606-8507, Japan
| | - Akihiro Kusumi
- Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, 606-8507, Japan. .,Center for Meso-Bio Single-Molecule Imaging (CeMI), Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, 606-8507, Japan. .,Membrane Cooperativity Unit, Okinawa Institute of Science and Technology, Okinawa, 904-0495, Japan.
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9
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Schübler M, Sadek B, Kottke T, Weizel L, Stark H. Synthesis, Molecular Properties Estimations, and Dual Dopamine D 2 and D 3 Receptor Activities of Benzothiazole-Based Ligands. Front Chem 2017; 5:64. [PMID: 28955709 PMCID: PMC5601007 DOI: 10.3389/fchem.2017.00064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/28/2017] [Indexed: 11/15/2022] Open
Abstract
Neurleptic drugs, e.g., aripiprazole, targeting the dopamine D2S and D3 receptors (D2SR and D3R) in the central nervous system are widely used in the treatment of several psychotic and neurodegenerative diseases. Therefore, a new series of benzothiazole-based ligands (3-20) was synthesized by applying the bioisosteric approach derived from the selective D3Rs ligand BP-897 (1) and its structurally related benz[d]imidazole derivative (2). Herein, introduction of the benzothiazole moiety was well tolerated by D2SR and D3R binding sites leading to antagonist affinities in the low nanomolar concentration range at both receptor subtypes. However, all novel compounds showed lower antagonist affinity to D3R when compared to that of 1. Further exploration of different substitution patterns at the benzothiazole heterocycle and the basic 4-phenylpiperazine resulted in the discovery of high dually acting D2SR and D3R ligands. Moreover, the methoxy substitution at 2-position of 4-phenylpiperazine resulted in significantly (22-fold) increased D2SR binding affinity as compared to the parent ligand 1, and improved physicochemical and drug-likeness properties of ligands 3-11. However, the latter structural modifications failed to improve the drug-able properties in ligands having un-substituted 4-phenylpiperazine analogs (12-20). Accordingly, compound 9 showed in addition to high dual affinity at the D2SR and D3R [Ki (hD2SR) = 2.8 ± 0.8 nM; Ki (hD3R) = 3.0 ± 1.6 nM], promising clogS, clogP, LE (hD2SR, hD3R), LipE (hD2SR, hD3R), and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (4.4, 4.3), and 0.7, respectively. Also, the deaminated analog 10 [Ki (hD2SR) = 3.2 ± 0.4 nM; Ki (hD3R) = 8.5 ± 2.2 nM] revealed clogS, clogP, LE (hD2SR, hD3R), LipE (hD2SR, hD3R) and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (3.9, 3.5), and 0.4, respectively. The results observed for the newly developed benzothiazole-based ligands 3-20 provide clues for the diversity in structure activity relationships (SARs) at the D2SR and D3R subtypes.
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Affiliation(s)
- Moritz Schübler
- Institute of Pharmaceutical Chemistry, Goethe University FrankfurtFrankfurt, Germany
| | - Bassem Sadek
- Department of Pharmacology and Therapeutics, College of Medicine and Health Sciences, United Arab Emirates UniversityAl Ain, United Arab Emirates
| | - Tim Kottke
- Institute of Pharmaceutical Chemistry, Goethe University FrankfurtFrankfurt, Germany
| | - Lilia Weizel
- Institute of Pharmaceutical Chemistry, Goethe University FrankfurtFrankfurt, Germany
| | - Holger Stark
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität DüsseldorfDuesseldorf, Germany
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10
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Visualization of ligand-induced dopamine D 2S and D 2L receptor internalization by TIRF microscopy. Sci Rep 2017; 7:10894. [PMID: 28883522 PMCID: PMC5589927 DOI: 10.1038/s41598-017-11436-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/23/2017] [Indexed: 01/11/2023] Open
Abstract
G protein-coupled receptors (GPCRs), including the dopamine receptors, represent a group of important pharmacological targets. Upon agonist binding, GPCRs frequently undergo internalization, a process that is known to attenuate functional responses upon prolonged exposure to agonists. In this study, internalization was visualized by means of total internal reflection fluorescence (TIRF) microscopy at a level of discrete single events near the plasma membrane with high spatial resolution. A novel method has been developed to determine the relative extent of internalized fluorescent receptor-ligand complexes by comparative fluorescence quantification in living CHO cells. The procedure entails treatment with the reducing agent sodium borohydride, which converts cyanine-based fluorescent ligands on the membrane surface to a long-lived reduced form. Because the highly polar reducing agent is not able to pass the cell membrane, the fluorescent receptor-ligand complexes located in internalized compartments remain fluorescent under TIRF illumination. We applied the method to investigate differences of the short (D2S) and the long (D2L) isoforms of dopamine D2 receptors in their ability to undergo agonist-induced internalization.
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11
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Tabor A, Weisenburger S, Banerjee A, Purkayastha N, Kaindl JM, Hübner H, Wei L, Grömer TW, Kornhuber J, Tschammer N, Birdsall NJM, Mashanov GI, Sandoghdar V, Gmeiner P. Visualization and ligand-induced modulation of dopamine receptor dimerization at the single molecule level. Sci Rep 2016; 6:33233. [PMID: 27615810 PMCID: PMC5018964 DOI: 10.1038/srep33233] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 08/23/2016] [Indexed: 12/19/2022] Open
Abstract
G protein–coupled receptors (GPCRs), including dopamine receptors, represent a group of important pharmacological targets. An increased formation of dopamine receptor D2 homodimers has been suggested to be associated with the pathophysiology of schizophrenia. Selective labeling and ligand-induced modulation of dimerization may therefore allow the investigation of the pathophysiological role of these dimers. Using TIRF microscopy at the single molecule level, transient formation of homodimers of dopamine receptors in the membrane of stably transfected CHO cells has been observed. The equilibrium between dimers and monomers was modulated by the binding of ligands; whereas antagonists showed a ratio that was identical to that of unliganded receptors, agonist-bound D2 receptor-ligand complexes resulted in an increase in dimerization. Addition of bivalent D2 receptor ligands also resulted in a large increase in D2 receptor dimers. A physical interaction between the protomers was confirmed using high resolution cryogenic localization microscopy, with ca. 9 nm between the centers of mass.
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Affiliation(s)
- Alina Tabor
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Siegfried Weisenburger
- Max Planck Institute for the Science of Light and Department of Physics, Friedrich-Alexander University, Günther-Scharowsky-Straße 1/ Bldg. 24, 91058 Erlangen, Germany
| | - Ashutosh Banerjee
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Nirupam Purkayastha
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Jonas M Kaindl
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Harald Hübner
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Luxi Wei
- Max Planck Institute for the Science of Light and Department of Physics, Friedrich-Alexander University, Günther-Scharowsky-Straße 1/ Bldg. 24, 91058 Erlangen, Germany
| | - Teja W Grömer
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Johannes Kornhuber
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander University, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Nuska Tschammer
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
| | - Nigel J M Birdsall
- The Francis Crick Institute, Mill Hill Laboratory, Mill Hill, London NW7 1AA, UK
| | - Gregory I Mashanov
- The Francis Crick Institute, Mill Hill Laboratory, Mill Hill, London NW7 1AA, UK
| | - Vahid Sandoghdar
- Max Planck Institute for the Science of Light and Department of Physics, Friedrich-Alexander University, Günther-Scharowsky-Straße 1/ Bldg. 24, 91058 Erlangen, Germany
| | - Peter Gmeiner
- Department of Chemistry and Pharmacy, Emil Fischer Center, Friedrich-Alexander University, Schuhstraße 19, 91052 Erlangen, Germany
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A peripherally restricted P2Y 12 receptor antagonist altered rat tumor incidences with no human relevance: Mode of action consistent with dopamine agonism. Toxicol Rep 2014; 1:1202-1212. [PMID: 28962330 PMCID: PMC5598522 DOI: 10.1016/j.toxrep.2014.11.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 11/10/2014] [Accepted: 11/11/2014] [Indexed: 12/26/2022] Open
Abstract
Background Ticagrelor is an orally available, direct acting and reversible P2Y12 receptor antagonist approved for treatment of acute coronary syndrome. The objectives of these studies were to (1) evaluate the Ticagrelor 2-year rat carcinogenicity bioassay data; (2) investigate potential mode of action (MOA) and (3) interpret human relevance. Methods The following studies were done (1) rat two-year carcinogenicity study in male and female rats, (2) in vitro and in vivo genotoxicity assays, (3) quantitative whole body autoradiography (QWBA; male and female rats), (4) in vitro pharmacological profiling for more than 300 assays, and (5) in vivo ovariectomized rat assay. Results The carcinogenicity study indicated Ticagrelor increased uterine tumor incidence while decreasing mammary and pituitary tumors/hyperplasia incidences in only high dose female rats. However, this altered tumor incidences were not P2Y12 target related since marketed non-reversible P2Y12 receptor antagonists were not associated with alter tumor incidences. MOA studies determined Ticagrelor exposure in the anterior pituitary and Ticagrelor was (1) non-genotoxic, (2) peripherally-restricted, (3) a dopamine transport (DAT) inhibitor with an IC50 lower than systemic free exposure in the rat carcinogenic study and more than a log higher than the free systemic exposure seen in clinical trials and (4) an inhibitor of estradiol-induced prolactin secretion. Discussion Similar to Ticagrelor, centrally active dopamine agonists induce the same altered tumor incidence patterns that according to literature do not translate into the clinical setting, with a MOA involving decreased prolactin secretion. The Ticagrelor MOA data and literature suggest that altered dopamine levels in the hypophyseal part of the hypothalamus–hypophyseal axis (by Ticagrelor) will result in similar altered tumor incidences in rat that do not translate into the clinical setting, based on qualitative species differences. In conclusion Ticagrelor increased uterine tumors in the rat carcinogenesis study by a MOA consistent with reduced dopamine inhibition of prolactin, which is not a patient safety risk.
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Key Words
- ADP, adenosine-5′-diphosphate
- AUC, area under the curve
- CHO, Chinese hamster ovary
- Carcinogenicity
- Cmax, maximal concentration, DAT, dopamine transport
- Dopamine transport inhibitor
- E2, estradiol
- GLP, good laboratory practice
- H&E, hematoxylin and eosin
- IC50, inhibitory concentration fifty percent
- Ki, inhibition concentration
- LC-MS/MS, liquid chromatography-mass spectrometric
- LLOQ, lower limits of quantification
- MOA, mode of action
- MTD, maximum tolerated dose
- NH, Hill coefficient
- Prolactin
- QWBA, quantitative whole body autoradiography
- TK, toxicokinetics
- Translational
- Uterine tumor
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Kara E, Lin H, Svensson K, Johansson AM, Strange PG. Analysis of the actions of the novel dopamine receptor-directed compounds (S)-OSU6162 and ACR16 at the D2 dopamine receptor. Br J Pharmacol 2011; 161:1343-50. [PMID: 20804495 DOI: 10.1111/j.1476-5381.2010.01010.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
UNLABELLED BACKGROUND AND PURPOSE; The two phenylpiperidines, OSU6162 and ACR16, have been proposed as novel drugs for the treatment of brain disorders, including schizophrenia and Huntington's disease, because of their putative dopamine stabilizing effects. Here we evaluated the activities of these compounds in a range of assays for the D(2) dopamine receptor in vitro. EXPERIMENTAL APPROACH The affinities of these compounds for the D(2) dopamine receptor were evaluated in competition with [(3) H]spiperone and [(3) H]NPA. Agonist activity of these compounds was evaluated in terms of their ability to stimulate [(35) S]GTPγS binding. KEY RESULTS Both compounds had low affinities for inhibition of [(3) H]spiperone binding (pK(i) vs. [(3) H]spiperone, ACR16: <5, OSU6162: 5.36). Neither compound was able to stimulate [(35) S]GTPγS binding when assayed in the presence of Na(+) ions, but if the Na(+) ions were removed, both compounds were low-affinity, partial agonists (E(max) relative to dopamine: ACR16: 10.2%, OSU6162:54.3%). Schild analysis of the effects of OSU6162 to inhibit dopamine-stimulated [(35) S]GTPγS binding indicated Schild slopes of ∼0.9, suggesting little deviation from competitive inhibition. OSU6162 was, however, able to accelerate [(3) H]NPA dissociation from D(2) dopamine receptors, indicating some allosteric effects of this compound. CONCLUSIONS AND IMPLICATIONS The two phenylpiperidines were low-affinity, low-efficacy partial agonists at the D(2) dopamine receptor in vitro, possibly exhibiting some allosteric effects. Comparing their in vitro and in vivo effects, the in vitro affinities were a reasonable guide to potencies in vivo. However, the lack of in vitro-in vivo correlation for agonist efficacy needs to be further addressed. LINKED ARTICLES This article is part of a themed section on Analytical Receptor Pharmacology in Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2010.161.issue-6.
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Affiliation(s)
- Elodie Kara
- School of Pharmacy, University of Reading, Reading, UK
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Neto LV, Machado EDO, Luque RM, Taboada GF, Marcondes JB, Chimelli LMC, Quintella LP, Niemeyer P, de Carvalho DP, Kineman RD, Gadelha MR. Expression analysis of dopamine receptor subtypes in normal human pituitaries, nonfunctioning pituitary adenomas and somatotropinomas, and the association between dopamine and somatostatin receptors with clinical response to octreotide-LAR in acromegaly. J Clin Endocrinol Metab 2009; 94:1931-7. [PMID: 19293270 PMCID: PMC2730344 DOI: 10.1210/jc.2008-1826] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
CONTEXT Dopamine receptor (DR) and somatostatin receptor subtype expression in pituitary adenomas may predict the response to postsurgical therapies. OBJECTIVES Our objectives were to assess and compare the mRNA levels of DR1-5 and somatostatin receptors 1-5 in normal pituitaries (NPs), nonfunctioning pituitary adenomas (NFPAs), and somatotropinomas. In addition, we determined whether the level of DR expression correlates with the in vivo response to octreotide-LAR in acromegalic patients. DESIGN AND PATIENTS Eight NPs, 30 NFPAs, and 39 somatotropinomas were analyzed for receptor mRNA levels by real-time RT-PCR. The DR2 short variant was estimated as the DR2 long/DR2 total (DR2T). The relationship between DR expression and the postsurgical response to octreotide-LAR was assessed in 19 of the acromegalic patients. RESULTS DR3 was not detected. The relationship between expression levels of DR subtypes in NPs and somatotropinomas was DR2T>>>DR4>>DR5>DR1, whereas in NFPAs, DR2T>>>DR4>>DR1>DR5. The DR2 short variant was the predominant DR2 variant in the majority of samples. In acromegalics treated with octreotide-LAR, DR1 was negatively correlated with percent GH reduction (3 months: r = -0.67, P = 0.002; and 6 months: r = -0.58, P = 0.009), and DR5 was positively correlated with percent IGF-I reduction (3 months: r = 0.55, P = 0.01; and 6 months: r = 0.47, P = 0.04). CONCLUSIONS DR2 is the predominant DR subtype in NPs, NFPAs, and somatotropinomas. The fact that DR1, DR4, and DR5 are also expressed in many adenomas tested suggests that these receptors might also play a role in the therapeutic impact of postsurgical medical therapies in patients with NFPA and acromegaly. This was supported by the finding that the in vivo response to octreotide-LAR was negatively associated with DR1 and positively associated with DR5.
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Affiliation(s)
- Leonardo Vieira Neto
- Endocrinology Section, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-913, Brazil
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Meyers NL, Hickling RI. Pharmacology and metabolism of renzapride : a novel therapeutic agent for the potential treatment of irritable bowel syndrome. Drugs R D 2008; 9:37-63. [PMID: 18095752 DOI: 10.2165/00126839-200809010-00004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND OBJECTIVE Renzapride (ATL-1251), a novel benzamide, is currently under clinical development for the treatment of irritable bowel syndrome (IBS). Previous in vitro and in vivo experimental studies have characterized renzapride as a full serotonin 5-HT(4) receptor agonist on the gut and a 5-HT(3) receptor antagonist. Clinical studies have confirmed the therapeutic efficacy, tolerability and safety of renzapride in patients with constipation-predominant IBS. This study set out to characterize the pharmacological profile of renzapride and its potential metabolic products at both 5-HT and other monoamine receptors in the gut. METHODS The affinity of renzapride, its (+) and (-) enantiomers, and its primary metabolite, renzapride N-oxide and its enantiomers, for serotonin receptors was assessed by means of in vitro radioligand binding inhibition studies. After membranes prepared from animal tissue or membranes of cell lines transfected with cloned human receptors had been incubated with radiolabelled ligand with high affinity for a specific receptor, renzapride was added to competitively inhibit this binding. Levels of bound radioligand were measured by filtration and counting of the bound radioactivity. In instances where >50% inhibition of radioligand binding had occurred, the inhibition constant (K(i)) was calculated. Metabolism of renzapride by liver microsomes was assessed by incubating 10 micromol/L renzapride with human liver microsome samples for 60 minutes at 37 degrees C. After the reaction was stopped, the samples were centrifuged and the supernatant analysed for metabolites by high-pressure liquid chromatography (HPLC). The potential inhibitory effects of renzapride on cytochrome P450 (CYP) enzymes were assessed by incubating renzapride at various concentrations over a 1-500 micromol/L concentration range with microsomes genetically engineered to express a single CYP. RESULTS Renzapride was selective for serotonergic receptors and, in particular, had high affinity for human 5-HT(3) and guinea-pig 5-HT(4) receptors (K(i) 17 and 477 nm, respectively). Inhibitory properties at 5-HT(2B) receptors were also identified for renzapride, as well as some affinity for 5-HT(2A) and 5-HT(2C) receptors. Renzapride N-oxide and its enantiomers demonstrated much lower affinity for all 5-HT receptors compared with renzapride. Renzapride was metabolized by liver microsomes to a limited extent and there was no significant non-microsomal metabolism of renzapride. Renzapride did not inhibit the major CYP drug-metabolizing enzymes CYP2C9, CYP2D6, CYP1A2, CYP2A6, CYP2C19, CYP2E1 or CYP3A4 at concentrations consistent with use in a clinical setting. CONCLUSIONS These results confirm and extend earlier studies in animal and human receptors that show renzapride is a potent and generally full 5-HT(4) receptor agonist and 5-HT(3) receptor antagonist. The results reported in the present study indicate that the metabolites of renzapride are minor and are unlikely to contribute to its therapeutic profile or lead to interaction of renzapride with other drugs that inhibit the major drug-metabolizing enzymes in the liver at therapeutic doses. These data contribute to the understanding of the pharmacological actions and metabolic fate of renzapride in vivo.
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Gemignani F, Landi S, Moreno V, Gioia-Patricola L, Chabrier A, Guino E, Navarro M, Cambray M, Capellà G, Canzian F. Polymorphisms of the Dopamine Receptor Gene DRD2 and Colorectal Cancer Risk. Cancer Epidemiol Biomarkers Prev 2005; 14:1633-8. [PMID: 16030094 DOI: 10.1158/1055-9965.epi-05-0057] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Sporadic colorectal cancer is considered a multifactorial disease in which multiple exposures interact with the individual genetic background resulting in risk modulation. Recent experimental data suggest a role of dopamine and dopamine receptors in the control of proliferation of the cells of colon and gastrointestinal tract. To investigate whether polymorphisms within dopamine receptors genes could have a role in modulating the risk of sporadic colorectal cancer, we did a case-control association study and genotyped 370 cases and 327 controls for seven single-nucleotide polymorphisms (SNP) of DRD2 (-141Cdel, 957T>C, TaqIB, TaqIA, 1412A>G, S311C, and 3208G>T) by a microarray-based technique. Three SNPs within DRD2 were associated with colorectal cancer, with a maximum odds ratio of 2.28 (95% confidence interval, 1.38-3.76) for carriers of the functional SNP -141Cdel. The haplotype which includes -141Cdel, together with the variants 957C and 1412G, shows an odds ratio of 2.86 (95% confidence interval, 1.58-5.18), as compared with the most frequent haplotype. The SNPs within DRD2 associated with colorectal cancer are known to be related to reduced levels of D2 dopamine receptor. Thus, our data point to a possible role of dopamine receptor DRD2 in modulating the risk of colorectal cancer. Future studies on dopamine receptor-mediated signal transduction may provide new insight into the mechanisms of colorectal cancer and suggest new therapeutic strategies.
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M. El-Abadelah M, Gmeiner P, Hübner H, A. Abu Safieh K, I. Fasfous I, S. Sabri S, Voelter W. Synthesis and Dopamine Receptor Binding of Some Pyrazolo[3’,4’:6,7]azepino[5,4,3-cd]indoles. HETEROCYCLES 2003. [DOI: 10.3987/com-03-9734] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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18
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Pauwels PJ, Tardif S, Wurch T, Colpaert FC. Real-time analysis of dopamine: antagonist interactions at recombinant human D2long receptor upon modulation of its activation state. Br J Pharmacol 2001; 134:88-97. [PMID: 11522600 PMCID: PMC1572932 DOI: 10.1038/sj.bjp.0704243] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Antipsychotic drugs may mediate their therapeutic effects not only by preventing the binding of dopamine but also by decreasing the propensity of the dopamine receptor to assume an active R* state. Ligand-mediated activation and blockade of the recombinant human D(2long) receptor was investigated in CHO-K1 cells upon modulation of its R* state. 2. Both the Ala(371)Lys (A371K) and Thr(372)Arg (T372R) D2long receptor mutants could be activated in a ligand-dependent manner via a chimeric G(alphaq/o) protein, and more efficaciously so than with the promiscuous G(alpha15) protein. 3. Dopamine and partial agonists (E(max): lisuride >> (+)-UH 232 approximately bromerguride) displayed dissimilar Ca(2+) kinetic properties at wild-type and mutant receptors. A371K and T372R D2long receptor mutants demonstrated an attenuated and enhanced maximal response to these partial agonists, respectively. 4. Dopamine antagonists were unable to block the transient high-magnitude Ca(2+) phase at the wild-type D2long receptor upon simultaneous exposure to antagonist and dopamine, while full blockade of the low-magnitude Ca(2+) phase did occur at a later time (onset-time: haloperidol < bromerguride < (+)-butaclamol). A similar, though more efficacious, antagonist profile was also found at the A371K mutant receptor. Conversely, the blockade of the low-magnitude Ca(2+) phase was attenuated (haloperidol) or almost absent [(+)-butaclamol and bromerguride] at the T372R mutant receptor. 5. In conclusion, mutagenesis of the Ala(371) and Thr(372) positions affects in an opposite way the ligand-dependent activation and blockade of the D2long receptor. The observed attenuation of dopamine-mediated Ca(2+) signal generation with different decay-times may underlie distinct properties of the dopaminergic ligands.
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Affiliation(s)
- P J Pauwels
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17, avenue Jean Moulin, 81106 Castres Cédex, France.
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Hoare SRJ, Coldwell MC, Armstrong D, Strange PG. Regulation of human D(1), d(2(long)), d(2(short)), D(3) and D(4) dopamine receptors by amiloride and amiloride analogues. Br J Pharmacol 2000; 130:1045-59. [PMID: 10882389 PMCID: PMC1572149 DOI: 10.1038/sj.bjp.0703370] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The modulatory effects of the allosteric effectors methylisobutylamiloride (MIA), benzamil and amiloride have been examined at human D(1), D(2), D(3) and D(4) dopamine receptors. The subtype selectivity and the mechanism of action of this allosteric regulation was examined. 2. In radioligand dissociation experiments each modulator accelerated dissociation from all four receptor subtypes indicating allosteric regulation. MIA displayed selectivity for the D(3) subtype for acceleration of radioligand dissociation. 3. In equilibrium binding (pseudo-competition) experiments the three compounds inhibited radioligand binding at the four receptor subtypes. Inhibition curves for D(1), D(2(short)), D(2(long)) and D(3) receptors were described by Hill coefficients exceeding unity and data were fitted best by a model that assumes binding of modulator to both the primary and allosteric binding sites of the receptor (the allosteric/competitive model). 4. At the D(4) subtype, Hill coefficients of unity described the binding data for amiloride and benzamil, consistent with competitive inhibition. The Hill coefficient for MIA at the D(4) subtype was less than unity and data could be fitted well by the allosteric/competitive model, but it was not possible to define unambiguously the modulatory mechanism. For this effect a better definition of the mechanism could be obtained by simultaneous analysis of data obtained in the presence of a range of concentrations of a purely competitive ligand. 5. MIA reduced the potency with which dopamine stimulated [(35)S]-GTPgammaS binding at the D(2) receptor. The effects of MIA could be described by the allosteric/competitive model with effects of MIA to inhibit the binding of dopamine but not its ability to induce a response.
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Affiliation(s)
- S R J Hoare
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ
| | - M C Coldwell
- Psychiatry Research, SmithKline Beecham Pharmaceuticals, New Frontiers Science Research Park, Harlow, Essex CM19 5AW
| | - D Armstrong
- School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ
| | - P G Strange
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ
- School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading RG6 6AJ
- Author for correspondence:
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Gardner B, Hall DA, Strange PG. Pharmacological analysis of dopamine stimulation of [35S]-GTP gamma S binding via human D2short and D2long dopamine receptors expressed in recombinant cells. Br J Pharmacol 1996; 118:1544-50. [PMID: 8832084 PMCID: PMC1909660 DOI: 10.1111/j.1476-5381.1996.tb15572.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. The activation of G-proteins by agonist-occupied D2 or D3 dopamine receptors in membranes from recombinant cells expressing the cloned receptors has been analysed by a [35S]-guanosine 5'-[gamma-thio] triphosphate ([35S]-GTP gamma S) binding assay. 2. The rate of [35S]-GTP gamma S binding was increased by dopamine in a dose-dependent manner in membranes from CHO cells stably expressing either the D2short or D2long dopamine receptor. 3. The dopamine-induced stimulation of [35S]-GTP gamma S binding could be inhibited by a range of antagonists. Affinities for antagonists derived from the inhibition of the dopamine stimulation of [35S]-GTP gamma S binding correlated very well with affinities derived from radioligand binding studies. 4. When the maximum [35S]-GTP gamma S binding responses stimulated by dopamine acting at different receptor subtypes were compared, there was a tendency for the stimulation via the D2short receptor to be greater than via the D2long receptor and for the stimulation via the D3 dopamine receptor to be less than for either D2 receptor. These differences in maximal response were also seen when the inhibitory effects of dopamine on adenylyl cyclase via the three receptor subtypes were compared. 5. The stimulation of [35S]-GTP gamma S binding by dopamine in membranes from recombinant cells therefore provides an excellent system for studying the molecular nature of agonism and the receptor/G-protein interactions for these receptors.
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Affiliation(s)
- B Gardner
- Research School of Biosciences, The University, Canterbury, Kent
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