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Moo EV, Harpsøe K, Hauser AS, Masuho I, Bräuner-Osborne H, Gloriam DE, Martemyanov KA. Ligand-directed bias of G protein signaling at the dopamine D 2 receptor. Cell Chem Biol 2022; 29:226-238.e4. [PMID: 34302750 PMCID: PMC8770702 DOI: 10.1016/j.chembiol.2021.07.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 05/21/2021] [Accepted: 07/02/2021] [Indexed: 01/11/2023]
Abstract
G-protein-coupled receptors (GPCRs) represent the largest family of drug targets. Upon activation, GPCRs signal primarily via a diverse set of heterotrimeric G proteins. Most GPCRs can couple to several different G protein subtypes. However, how drugs act at GPCRs contributing to the selectivity of G protein recognition is poorly understood. Here, we examined the G protein selectivity profile of the dopamine D2 receptor (D2), a GPCR targeted by antipsychotic drugs. We show that D2 discriminates between six individual members of the Gi/o family, and its profile of functional selectivity is remarkably different across its ligands, which all engaged D2 with a distinct G protein coupling pattern. Using structural modeling, receptor mutagenesis, and pharmacological evaluation, we identified residues in the D2 binding pocket that shape these ligand-directed biases. We further provide pharmacogenomic evidence that natural variants in D2 differentially affect its G protein biases in response to different ligands.
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Affiliation(s)
- Ee Von Moo
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA,Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Kasper Harpsøe
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Alexander S Hauser
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Ikuo Masuho
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - David E. Gloriam
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
| | - Kirill A. Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
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2
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Preto AJ, Barreto CAV, Baptista SJ, Almeida JGD, Lemos A, Melo A, Cordeiro MNDS, Kurkcuoglu Z, Melo R, Moreira IS. Understanding the Binding Specificity of G-Protein Coupled Receptors toward G-Proteins and Arrestins: Application to the Dopamine Receptor Family. J Chem Inf Model 2020; 60:3969-3984. [PMID: 32692555 DOI: 10.1021/acs.jcim.0c00371] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
G-Protein coupled receptors (GPCRs) are involved in a myriad of pathways key for human physiology through the formation of complexes with intracellular partners such as G-proteins and arrestins (Arrs). However, the structural and dynamical determinants of these complexes are still largely unknown. Herein, we developed a computational big-data pipeline that enables the structural characterization of GPCR complexes with no available structure. This pipeline was used to study a well-known group of catecholamine receptors, the human dopamine receptor (DXR) family and its complexes, producing novel insights into the physiological properties of these important drug targets. A detailed description of the protein interfaces of all members of the DXR family (D1R, D2R, D3R, D4R, and D5R) and the corresponding protein interfaces of their binding partners (Arrs: Arr2 and Arr3; G-proteins: Gi1, Gi2, Gi3, Go, Gob, Gq, Gslo, Gssh, Gt2, and Gz) was generated. To produce reliable structures of the DXR family in complex with either G-proteins or Arrs, we performed homology modeling using as templates the structures of the β2-adrenergic receptor (β2AR) bound to Gs, the rhodopsin bound to Gi, and the recently acquired neurotensin receptor-1 (NTSR1) and muscarinic 2 receptor (M2R) bound to arrestin (Arr). Among others, the work demonstrated that the three partner groups, Arrs and Gs- and Gi-proteins, are all structurally and dynamically distinct. Additionally, it was revealed the involvement of different structural motifs in G-protein selective coupling between D1- and D2-like receptors. Having constructed and analyzed 50 models involving DXR, this work represents an unprecedented large-scale analysis of GPCR-intracellular partner interface determinants. All data is available at www.moreiralab.com/resources/dxr.
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Affiliation(s)
- A J Preto
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Casa Costa Alemão - Pólo II
- Rua Dom Francisco de Lemos, 3030-789 Coimbra, Portugal
| | - Carlos A V Barreto
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Casa Costa Alemão - Pólo II
- Rua Dom Francisco de Lemos, 3030-789 Coimbra, Portugal
| | - Salete J Baptista
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao Km 139,7, 2695-066 Bobadela, Portugal
| | - José Guilherme de Almeida
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,European Bioinformatics Institute EMBL-EBI, Hinxton, Cambridgeshire CB10 1SD, United Kingdom
| | - Agostinho Lemos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,GIGA Cyclotron Research Centre In Vivo Imaging, University of Liège, Bâtiment B30, Allée du 6 Août, 8, 4000 Liège, Belgium
| | - André Melo
- REQUIMTE/LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre 687, s/n, 4169-007 Porto, Portugal
| | - M Nátalia D S Cordeiro
- REQUIMTE/LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua Campo Alegre 687, s/n, 4169-007 Porto, Portugal
| | - Zeynep Kurkcuoglu
- Bijvoet Center for Biomolecular Research, Faculty of Science - Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Rita Melo
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10, ao Km 139,7, 2695-066 Bobadela, Portugal
| | - Irina S Moreira
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,University of Coimbra, Center for Innovative Biomedicine and Biotechnology, Faculty of Medicine, Pólo I, 1st floor, 3004-504 Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Colégio de S. Bento, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
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3
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Gnaz couples the circadian and dopaminergic system to G protein-mediated signaling in mouse photoreceptors. PLoS One 2017; 12:e0187411. [PMID: 29088301 PMCID: PMC5663513 DOI: 10.1371/journal.pone.0187411] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/19/2017] [Indexed: 01/08/2023] Open
Abstract
The mammalian retina harbors a circadian clockwork that regulates vision and promotes healthiness of retinal neurons, mainly through directing the rhythmic release of the neurohormones dopamine—acting on dopamine D4 receptors—and melatonin—acting on MT1 and MT2 receptors. The gene Gnaz—a unique Gi/o subfamily member—was seen in the present study to be expressed in photoreceptors where its protein product Gαz shows a daily rhythm in its subcellular localization. Apart from subcellular localization, Gnaz displays a daily rhythm in expression—with peak values at night—in preparations of the whole retina, microdissected photoreceptors and photoreceptor-related pinealocytes. In retina, Gnaz rhythmicity was observed to persist under constant darkness and to be abolished in retina deficient for Clock or dopamine D4 receptors. Furthermore, circadian regulation of Gnaz was disturbed in the db/db mouse, a model of diabetic retinopathy. The data of the present study suggest that Gnaz links the circadian clockwork—via dopamine acting on D4 receptors—to G protein-mediated signaling in intact but not diabetic retina.
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4
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Clayton CC, Donthamsetti P, Lambert NA, Javitch JA, Neve KA. Mutation of three residues in the third intracellular loop of the dopamine D2 receptor creates an internalization-defective receptor. J Biol Chem 2014; 289:33663-75. [PMID: 25336643 DOI: 10.1074/jbc.m114.605378] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Arrestins mediate desensitization and internalization of G protein-coupled receptors and also direct receptor signaling toward heterotrimeric G protein-independent signaling pathways. We previously identified a four-residue segment (residues 212-215) of the dopamine D2 receptor that is necessary for arrestin binding in an in vitro heterologous expression system but that also impairs receptor expression. We now describe the characterization of additional mutations at that arrestin binding site in the third intracellular loop. Mutating two (residues 214 and 215) or three (residues 213-215) of the four residues to alanine partially decreased agonist-induced recruitment of arrestin3 without altering activation of a G protein. Arrestin-dependent receptor internalization, which requires arrestin binding to β2-adaptin (the β2 subunit of the clathrin-associated adaptor protein AP2) and clathrin, was disproportionately affected by the three-residue mutation, with no agonist-induced internalization observed even in the presence of overexpressed arrestin or G protein-coupled receptor kinase 2. The disjunction between arrestin recruitment and internalization could not be explained by alterations in the time course of the receptor-arrestin interaction, the recruitment of G protein-coupled receptor kinase 2, or the receptor-induced interaction between arrestin and β2-adaptin, suggesting that the mutation impairs a property of the internalization complex that has not yet been identified.
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Affiliation(s)
- Cecilea C Clayton
- the Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239
| | - Prashant Donthamsetti
- the Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, the Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, and
| | - Nevin A Lambert
- the Department of Pharmacology and Toxicology, Medical College of Georgia, Georgia Regents University, Augusta, Georgia 30912
| | - Jonathan A Javitch
- the Departments of Psychiatry and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, the Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, New York 10032, and
| | - Kim A Neve
- the Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, Oregon 97239, From the Research Service, Department of Veterans Affairs Medical Center, Portland, Oregon 97239,
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5
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Nord AS, Blow MJ, Attanasio C, Akiyama JA, Holt A, Hosseini R, Phouanenavong S, Plajzer-Frick I, Shoukry M, Afzal V, Rubenstein JLR, Rubin EM, Pennacchio LA, Visel A. Rapid and pervasive changes in genome-wide enhancer usage during mammalian development. Cell 2014; 155:1521-31. [PMID: 24360275 DOI: 10.1016/j.cell.2013.11.033] [Citation(s) in RCA: 260] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 10/28/2013] [Accepted: 11/22/2013] [Indexed: 12/26/2022]
Abstract
Enhancers are distal regulatory elements that can activate tissue-specific gene expression and are abundant throughout mammalian genomes. Although substantial progress has been made toward genome-wide annotation of mammalian enhancers, their temporal activity patterns and global contributions in the context of developmental in vivo processes remain poorly explored. Here we used epigenomic profiling for H3K27ac, a mark of active enhancers, coupled to transgenic mouse assays to examine the genome-wide utilization of enhancers in three different mouse tissues across seven developmental stages. The majority of the ∼90,000 enhancers identified exhibited tightly temporally restricted predicted activity windows and were associated with stage-specific biological functions and regulatory pathways in individual tissues. Comparative genomic analysis revealed that evolutionary conservation of enhancers decreases following midgestation across all tissues examined. The dynamic enhancer activities uncovered in this study illuminate rapid and pervasive temporal in vivo changes in enhancer usage that underlie processes central to development and disease.
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Affiliation(s)
- Alex S Nord
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Matthew J Blow
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Catia Attanasio
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jennifer A Akiyama
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Amy Holt
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Roya Hosseini
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Sengthavy Phouanenavong
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Ingrid Plajzer-Frick
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Malak Shoukry
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Veena Afzal
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - John L R Rubenstein
- Department of Psychiatry, Rock Hall, University of California, San Francisco, CA 94158-2324, USA
| | - Edward M Rubin
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Len A Pennacchio
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA 94598, USA.
| | - Axel Visel
- Genomics Division, MS 84-171, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; U.S. Department of Energy Joint Genome Institute, Walnut Creek, CA 94598, USA; School of Natural Sciences, University of California, Merced, CA 95343, USA.
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6
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Hultman R, Kumari U, Michel N, Casey PJ. Gαz regulates BDNF-induction of axon growth in cortical neurons. Mol Cell Neurosci 2013; 58:53-61. [PMID: 24321455 DOI: 10.1016/j.mcn.2013.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 11/27/2013] [Accepted: 12/03/2013] [Indexed: 01/26/2023] Open
Abstract
The disruption of neurotransmitter and neurotrophic factor signaling in the central nervous system (CNS) is implicated as the root cause of neuropsychiatric disorders, including schizophrenia, epilepsy, chronic pain, and depression. Therefore, identifying the underlying molecular mechanisms by which neurotransmitter and neurotrophic factor signaling regulates neuronal survival or growth may facilitate identification of more effective therapies for these disorders. Previously, our lab found that the heterotrimeric G protein, Gz, mediates crosstalk between G protein-coupled receptors and neurotrophin signaling in the neural cell line PC12. These data, combined with Gαz expression profiles--predominantly in neuronal cells with higher expression levels corresponding to developmental times of target tissue innervation--suggested that Gαz may play an important role in neurotrophin signaling and neuronal development. Here, we provide evidence in cortical neurons, both manipulated ex vivo and those cultured from Gz knockout mice, that Gαz is localized to axonal growth cones and plays a significant role in the development of axons of cortical neurons in the CNS. Our findings indicate that Gαz inhibits BDNF-stimulated axon growth in cortical neurons, establishing an endogenous role for Gαz in regulating neurotrophin signaling in the CNS.
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Affiliation(s)
- Rainbo Hultman
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA; Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore
| | - Udhaya Kumari
- Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore
| | - Nadine Michel
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA
| | - Patrick J Casey
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA; Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, Singapore 169857, Republic of Singapore.
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7
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Kimple ME, Moss JB, Brar HK, Rosa TC, Truchan NA, Pasker RL, Newgard CB, Casey PJ. Deletion of GαZ protein protects against diet-induced glucose intolerance via expansion of β-cell mass. J Biol Chem 2012; 287:20344-55. [PMID: 22457354 DOI: 10.1074/jbc.m112.359745] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Insufficient plasma insulin levels caused by deficits in both pancreatic β-cell function and mass contribute to the pathogenesis of type 2 diabetes. This loss of insulin-producing capacity is termed β-cell decompensation. Our work is focused on defining the role(s) of guanine nucleotide-binding protein (G protein) signaling pathways in regulating β-cell decompensation. We have previously demonstrated that the α-subunit of the heterotrimeric G(z) protein, Gα(z), impairs insulin secretion by suppressing production of cAMP. Pancreatic islets from Gα(z)-null mice also exhibit constitutively increased cAMP production and augmented glucose-stimulated insulin secretion, suggesting that Gα(z) is a tonic inhibitor of adenylate cyclase, the enzyme responsible for the conversion of ATP to cAMP. In the present study, we show that mice genetically deficient for Gα(z) are protected from developing glucose intolerance when fed a high fat (45 kcal%) diet. In these mice, a robust increase in β-cell proliferation is correlated with significantly increased β-cell mass. Further, an endogenous Gα(z) signaling pathway, through circulating prostaglandin E activating the EP3 isoform of the E prostanoid receptor, appears to be up-regulated in insulin-resistant, glucose-intolerant mice. These results, along with those of our previous work, link signaling through Gα(z) to both major aspects of β-cell decompensation: insufficient β-cell function and mass.
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Affiliation(s)
- Michelle E Kimple
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705, USA.
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8
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Pou C, Mannoury la Cour C, Stoddart LA, Millan MJ, Milligan G. Functional homomers and heteromers of dopamine D2L and D3 receptors co-exist at the cell surface. J Biol Chem 2012; 287:8864-78. [PMID: 22291025 DOI: 10.1074/jbc.m111.326678] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human dopamine D(2long) and D(3) receptors were modified by N-terminal addition of SNAP or CLIP forms of O(6)-alkylguanine-DNA-alkyltransferase plus a peptide epitope tag. Cells able to express each of these four constructs only upon addition of an antibiotic were established and used to confirm regulated and inducible control of expression, the specificity of SNAP and CLIP tag covalent labeling reagents, and based on homogenous time-resolved fluorescence resonance energy transfer, the presence of cell surface D(2long) and D(3) receptor homomers. Following constitutive expression of reciprocal constructs, potentially capable of forming and reporting the presence of cell surface D(2long)-D(3) heteromers, individual clones were assessed for levels of expression of the constitutively expressed protomer. This was unaffected by induction of the partner protomer and the level of expression of the partner required to generate detectable cell surface D(2long)-D(3) heteromers was defined. Such homomers and heteromers were found to co-exist and using a reconstitution of function approach both homomers and heteromers of D(2long) and D(3) receptors were shown to be functional, potentially via trans-activation of associated G protein. These studies demonstrate the ability of dopamine D(2long) and D(3) receptors to form both homomers and heteromers, and show that in cells expressing each subtype a complex mixture of homomers and heteromers co-exists at steady state. These data are of potential importance both to disorders in which D(2long) and D(3) receptors are implicated, like schizophrenia and Parkinson disease, and also to drugs exerting their actions via these sites.
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Affiliation(s)
- Chantevy Pou
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
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Abstract
Endocrine pituitary cells are neuronlike; they express numerous voltage-gated sodium, calcium, potassium, and chloride channels and fire action potentials spontaneously, accompanied by a rise in intracellular calcium. In some cells, spontaneous electrical activity is sufficient to drive the intracellular calcium concentration above the threshold for stimulus-secretion and stimulus-transcription coupling. In others, the function of these action potentials is to maintain the cells in a responsive state with cytosolic calcium near, but below, the threshold level. Some pituitary cells also express gap junction channels, which could be used for intercellular Ca(2+) signaling in these cells. Endocrine cells also express extracellular ligand-gated ion channels, and their activation by hypothalamic and intrapituitary hormones leads to amplification of the pacemaking activity and facilitation of calcium influx and hormone release. These cells also express numerous G protein-coupled receptors, which can stimulate or silence electrical activity and action potential-dependent calcium influx and hormone release. Other members of this receptor family can activate calcium channels in the endoplasmic reticulum, leading to a cell type-specific modulation of electrical activity. This review summarizes recent findings in this field and our current understanding of the complex relationship between voltage-gated ion channels, ligand-gated ion channels, gap junction channels, and G protein-coupled receptors in pituitary cells.
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Affiliation(s)
- Stanko S Stojilkovic
- Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Building 49, Room 6A-36, 49 Convent Drive, Bethesda, Maryland 20892-4510, USA.
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10
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Millan MJ. From the cell to the clinic: a comparative review of the partial D₂/D₃receptor agonist and α2-adrenoceptor antagonist, piribedil, in the treatment of Parkinson's disease. Pharmacol Ther 2010; 128:229-73. [PMID: 20600305 DOI: 10.1016/j.pharmthera.2010.06.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/02/2010] [Indexed: 12/16/2022]
Abstract
Though L-3,4-dihydroxyphenylalanine (L-DOPA) is universally employed for alleviation of motor dysfunction in Parkinson's disease (PD), it is poorly-effective against co-morbid symptoms like cognitive impairment and depression. Further, it elicits dyskinesia, its pharmacokinetics are highly variable, and efficacy wanes upon long-term administration. Accordingly, "dopaminergic agonists" are increasingly employed both as adjuncts to L-DOPA and as monotherapy. While all recognize dopamine D(2) receptors, they display contrasting patterns of interaction with other classes of monoaminergic receptor. For example, pramipexole and ropinirole are high efficacy agonists at D(2) and D(3) receptors, while pergolide recognizes D(1), D(2) and D(3) receptors and a broad suite of serotonergic receptors. Interestingly, several antiparkinson drugs display modest efficacy at D(2) receptors. Of these, piribedil displays the unique cellular signature of: 1), signal-specific partial agonist actions at dopamine D(2)and D(3) receptors; 2), antagonist properties at α(2)-adrenoceptors and 3), minimal interaction with serotonergic receptors. Dopamine-deprived striatal D(2) receptors are supersensitive in PD, so partial agonism is sufficient for relief of motor dysfunction while limiting undesirable effects due to "over-dosage" of "normosensitive" D(2) receptors elsewhere. Further, α(2)-adrenoceptor antagonism reinforces adrenergic, dopaminergic and cholinergic transmission to favourably influence motor function, cognition, mood and the integrity of dopaminergic neurones. In reviewing the above issues, the present paper focuses on the distinctive cellular, preclinical and therapeutic profile of piribedil, comparisons to pramipexole, ropinirole and pergolide, and the core triad of symptoms that characterises PD-motor dysfunction, depressed mood and cognitive impairment. The article concludes by highlighting perspectives for clarifying the mechanisms of action of piribedil and other antiparkinson agents, and for optimizing their clinical exploitation.
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Affiliation(s)
- Mark J Millan
- Dept of Psychopharmacology, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy/Seine (Paris), France.
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11
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Britz D, Chandra S, Strutwolf J, Wong DK. Diffusion-limited chronoamperometry at conical-tip microelectrodes. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2009.10.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Stojilkovic SS, Murano T, Gonzalez-Iglesias AE, Andric SA, Popovic MA, Van Goor F, Tomić M. Multiple roles of Gi/o protein-coupled receptors in control of action potential secretion coupling in pituitary lactotrophs. Ann N Y Acad Sci 2009; 1152:174-86. [PMID: 19161388 DOI: 10.1111/j.1749-6632.2008.03994.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
G(i/o) protein-coupled receptors, signaling through G protein-dependent and protein-independent pathways, have prominent effects on secretion by modulating calcium signaling and regulating the size of the releasable secretory pool, the rates of exocytosis and endocytosis, and de novo synthesis. Pituitary cells fire action potentials spontaneously, and the associated calcium influx is sufficient to maintain prolactin (PRL) release but not gonadotropin release at high and steady levels for many hours. Such secretion, termed intrinsic, spontaneous, or basal, reflects fusion of secretory vesicles triggered by the cell type-specific pattern of action potentials. In lactotrophs, activation of endothelin ET(A) and dopamine D(2) receptors causes inhibition of spontaneous electrical activity and basal adenylyl cyclase activity accompanied with inhibition of basal PRL release. Agonist-induced inhibition of cAMP production and firing of action potentials is abolished in cells with blocked pertussis toxin (PTX)-sensitive G(i/o) signaling pathway. However, agonist-induced inhibition of PRL release is only partially relieved in such treated cells, indicating that both receptors also inhibit exocytosis downstream of cAMP/calcium signaling. The PTX-insensitive step in agonist-induced inhibition of PRL release is not affected by inhibition of phosphoinositide 3-kinase and glycogen synthase kinase-3 but is partially rescued by downregulation of the G(z)alpha expression. Thus, ET(A) and D(2) receptors inhibit basal PRL release not only by blocking electrical activity but also by desensitizing calcium-secretion coupling.
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Affiliation(s)
- Stanko S Stojilkovic
- Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
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Kitanaka N, Kitanaka J, Hall FS, Tatsuta T, Morita Y, Takemura M, Wang XB, Uhl GR. Alterations in the levels of heterotrimeric G protein subunits induced by psychostimulants, opiates, barbiturates, and ethanol: Implications for drug dependence, tolerance, and withdrawal. Synapse 2008; 62:689-99. [PMID: 18566973 DOI: 10.1002/syn.20543] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Neuronal adaptations have been found to occur in multiple brain regions after chronic intake of abused drugs, and are therefore thought to underlie drug dependence, tolerance, and withdrawal. Pathophysiological changes in drug responsiveness as well as behavioral sequelae of chronic drug exposure are thought to depend largely upon the altered state of heterotrimeric GTP binding protein (G protein)-coupled receptor (GPCR)-G protein interactions. Responsiveness of GPCR-related intracellular signaling systems to drugs of abuse is heterogeneous, depending on the types of intracellular effectors to which the specific Galpha protein subtypes are coupled and GPCR-G protein coupling efficiency, factors influenced by the class of drug, expression levels of G protein subunits, and drug treatment regimens. To enhance understanding of the molecular mechanisms that underlie the development of pathophysiological states resulting from chronic intake of abused drugs, this review focuses on alterations in the expression levels of G protein subunits induced by various drugs of abuse. Changes in these mechanisms appear to be specific to particular drugs of abuse, and specific conditions of drug treatment.
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Affiliation(s)
- Nobue Kitanaka
- Department of Pharmacology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, Japan.
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Gonzalez-Iglesias AE, Murano T, Li S, Tomić M, Stojilkovic SS. Dopamine inhibits basal prolactin release in pituitary lactotrophs through pertussis toxin-sensitive and -insensitive signaling pathways. Endocrinology 2008; 149:1470-9. [PMID: 18096663 PMCID: PMC2276716 DOI: 10.1210/en.2007-0980] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dopamine D2 receptors signal through the pertussis toxin (PTX)-sensitive G(i/o) and PTX-insensitive G(z) proteins, as well as through a G protein-independent, beta-arrestin/glycogen synthase kinase-3-dependent pathway. Activation of these receptors in pituitary lactotrophs leads to inhibition of prolactin (PRL) release. It has been suggested that this inhibition occurs through the G(i/o)-alpha protein-mediated inhibition of cAMP production and/or G(i/o)-betagamma dimer-mediated activation of inward rectifier K(+) channels and inhibition of voltage-gated Ca(2+) channels. Here we show that the dopamine agonist-induced inhibition of spontaneous Ca(2+) influx and release of prestored PRL was preserved when cAMP levels were elevated by forskolin treatment. We further observed that dopamine agonists inhibited both spontaneous and depolarization-induced Ca(2+) influx in untreated but not in PTX-treated cells. This inhibition was also observed in cells with blocked inward rectifier K(+) channels, suggesting that the dopamine effect on voltage-gated Ca(2+) channel gating is sufficient to inhibit spontaneous Ca(2+) influx. However, agonist-induced inhibition of PRL release was only partially relieved in PTX-treated cells, indicating that dopamine receptors also inhibit exocytosis downstream of voltage-gated Ca(2+) influx. The PTX-insensitive step in agonist-induced inhibition of PRL release was not affected by the addition of wortmannin, an inhibitor of phosphatidylinositol 3-kinase, and lithium, an inhibitor of glycogen synthase kinase-3, but was attenuated in the presence of phorbol 12-myristate 13-acetate, which inhibits G(z) signaling pathway in a protein kinase C-dependent manner. Thus, dopamine inhibits basal PRL release by blocking voltage-gated Ca(2+) influx through the PTX-sensitive signaling pathway and by desensitizing Ca(2+) secretion coupling through the PTX-insensitive and protein kinase C-sensitive signaling pathway.
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Affiliation(s)
- Arturo E Gonzalez-Iglesias
- National Institute of Child Health and Human Development, 49 Convent Drive, Bethesda, MD 20892-4510, USA
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Kimple ME, Joseph JW, Bailey CL, Fueger PT, Hendry IA, Newgard CB, Casey PJ. Galphaz negatively regulates insulin secretion and glucose clearance. J Biol Chem 2007; 283:4560-7. [PMID: 18096703 DOI: 10.1074/jbc.m706481200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Relatively little is known about the in vivo functions of the alpha subunit of the heterotrimeric G protein Gz (Galphaz). Clues to one potential function recently emerged with the finding that activation of Galphaz inhibits glucose-stimulated insulin secretion in an insulinoma cell line (Kimple, M. E., Nixon, A. B., Kelly, P., Bailey, C. L., Young, K. H., Fields, T. A., and Casey, P. J. (2005) J. Biol. Chem. 280, 31708-31713). To extend this study in vivo, a Galphaz knock-out mouse model was utilized to determine whether Galphaz function plays a role in the inhibition of insulin secretion. No differences were discovered in the gross morphology of the pancreatic islets or in the islet DNA, protein, or insulin content between Galphaz-null and wild-type mice. There was also no difference between the insulin sensitivity of Galphaz-null mice and wild-type controls, as measured by insulin tolerance tests. Galphaz-null mice did, however, display increased plasma insulin concentrations and a corresponding increase in glucose clearance following intraperitoneal and oral glucose challenge as compared with wild-type controls. The increased plasma insulin observed in Galphaz-null mice is most likely a direct result of enhanced insulin secretion, since pancreatic islets isolated from Galphaz-null mice exhibited significantly higher glucose-stimulated insulin secretion than those of wild-type mice. Finally, the increased insulin secretion observed in Galphaz-null islets appears to be due to the relief of a tonic inhibition of adenylyl cyclase, as cAMP production was significantly increased in Galphaz-null islets in the absence of exogenous stimulation. These findings indicate that Galphaz may be a potential new target for therapeutics aimed at ameliorating beta-cell dysfunction in Type 2 diabetes.
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Affiliation(s)
- Michelle E Kimple
- Department of Pharmacology, and The Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, North Carolina 27710-3813, USA
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van den Buuse M, Martin S, Holgate J, Matthaei K, Hendry I. Mice deficient in the alpha subunit of G(z) show changes in pre-pulse inhibition, anxiety and responses to 5-HT(1A) receptor stimulation, which are strongly dependent on the genetic background. Psychopharmacology (Berl) 2007; 195:273-83. [PMID: 17684732 DOI: 10.1007/s00213-007-0888-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Accepted: 07/02/2007] [Indexed: 10/23/2022]
Abstract
RATIONALE G(z), a member of the G(i) G protein family, is involved in the coupling of dopaminergic and serotonergic receptors. In the present study, we investigated behaviour of mice deficient in the alpha subunit of G(z) and focused on pre-pulse inhibition (PPI) and anxiety-like responses and the role of serotonin-1A (5-HT(1A)) receptors. MATERIALS AND METHODS We compared male and female wild-type and knock-out mice on either a C57Bl/6 or Balb/c background. We used automated startle boxes to assess startle and PPI and elevated plus maze to assess anxiety-like behaviours. RESULTS Balb/c mice showed higher baseline PPI than C57Bl/6 mice, and there was no difference between the genotypes. The 5-HT(1A) receptor agonist, 8-hydroxy-di-propylaminotetralin (8-OH-DPAT), had no effect on PPI in C57Bl/6 mice but markedly increased PPI in Balb/c mice, with the effect being attenuated in Galpha(z) knock-outs. On the elevated plus maze, there was little effect of the knock-out or 8-OH-DPAT in C57Bl/6 mice, whereas in Balb/c mice, Galpha(z) knock-outs showed a phenotype of high levels of anxiety-like behaviour. 8-OH-DPAT was anxiogenic in Balb/c mice, but this effect was attenuated in Galpha(z) knock-outs. CONCLUSIONS 5-HT(1A) receptors couple to G(z). In a strictly background strain-dependent manner, Galpha(z) knock-out mice display high levels of anxiety-like behaviour and are less sensitive to the action of 8-OH-DPAT. Balb/c mice show much more clear effects of the Galpha(z) knock-out than C57Bl/6 mice, which are often considered the standard background strain for genetic modifications. Therefore, our results suggest caution when studying the behavioural effects of genetic modifications only in C57Bl/6 mice.
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Affiliation(s)
- Maarten van den Buuse
- Behavioural Neuroscience Laboratory, Mental Health Research Institute, 155 Oak Street, Parkville, Victoria 3052, Australia.
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