101
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de Munnik SM, van der Lee R, Velders DM, van Offenbeek J, Smits-de Vries L, Leurs R, Smit MJ, Vischer HF. The viral G protein-coupled receptor ORF74 unmasks phospholipase C signaling of the receptor tyrosine kinase IGF-1R. Cell Signal 2016; 28:595-605. [DOI: 10.1016/j.cellsig.2016.02.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 11/16/2022]
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102
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Tesmer JJG. Hitchhiking on the heptahelical highway: structure and function of 7TM receptor complexes. Nat Rev Mol Cell Biol 2016; 17:439-50. [PMID: 27093944 DOI: 10.1038/nrm.2016.36] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A revolution in the analysis of seven transmembrane domain (7TM) receptors has provided detailed information about how these physiologically important signalling proteins interact with extracellular cues. However, it has proved much more challenging to understand how 7TM receptors convey information to their principal intracellular targets: heterotrimeric G proteins, G protein-coupled receptor kinases and arrestins. Recent structures now suggest a common mechanism that enables these structurally diverse cytoplasmic proteins to 'hitch a ride' on hundreds of different activated 7TM receptors in order to instigate physiological change.
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Affiliation(s)
- John J G Tesmer
- Life Sciences Institute and Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-2216, USA
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103
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Najafi A, Sequeira V, Kuster DWD, van der Velden J. β-adrenergic receptor signalling and its functional consequences in the diseased heart. Eur J Clin Invest 2016; 46:362-74. [PMID: 26842371 DOI: 10.1111/eci.12598] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 01/30/2016] [Indexed: 12/28/2022]
Abstract
BACKGROUND To maintain the balance between the demand of the body and supply (cardiac output), cardiac performance is tightly regulated via the parasympathetic and sympathetic nervous systems. In heart failure, cardiac output (supply) is decreased due to pathologic remodelling of the heart. To meet the demands of the body, the sympathetic system is activated and catecholamines stimulate β-adrenergic receptors (β-ARs) to increase contractile performance and cardiac output. Although this is beneficial in the acute phase, chronic β-ARs stimulation initiates a cascade of alterations at the cellular level, resulting in a diminished contractile performance of the heart. MATERIALS AND METHODS This narrative review includes results from previously published systematic reviews and clinical and basic research publications obtained via PubMed up to May 2015. RESULTS We discuss the alterations that occur during sustained β-AR stimulation in diseased myocardium and emphasize the consequences of β-AR overstimulation for cardiac function. In addition, current treatment options as well as future therapeutic strategies to treat patients with heart failure to normalize consequences of β-AR overstimulation are discussed. CONCLUSIONS The heart is able to protect itself from chronic stimulation of the β-ARs via desensitization and reduced membrane availability of the β-ARs. However, ultimately this leads to an impaired downstream signalling and decreased protein kinase A (PKA)-mediated protein phosphorylation. β-blockers are widely used to prevent β-AR overstimulation and restore β-ARs in the failing hearts. However, novel and more specific therapeutic treatments are needed to improve treatment of HF in the future.
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Affiliation(s)
- Aref Najafi
- Department of Physiology, VU University Medical Center, Institute for Cardiovascular research (ICaR-VU), Amsterdam, the Netherlands.,ICIN-Netherlands Heart Institute, Utrecht, the Netherlands
| | - Vasco Sequeira
- Department of Physiology, VU University Medical Center, Institute for Cardiovascular research (ICaR-VU), Amsterdam, the Netherlands
| | - Diederik W D Kuster
- Department of Physiology, VU University Medical Center, Institute for Cardiovascular research (ICaR-VU), Amsterdam, the Netherlands
| | - Jolanda van der Velden
- Department of Physiology, VU University Medical Center, Institute for Cardiovascular research (ICaR-VU), Amsterdam, the Netherlands.,ICIN-Netherlands Heart Institute, Utrecht, the Netherlands
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104
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Poniatowski ŁA, Wojdasiewicz P, Krawczyk M, Szukiewicz D, Gasik R, Kubaszewski Ł, Kurkowska-Jastrzębska I. Analysis of the Role of CX3CL1 (Fractalkine) and Its Receptor CX3CR1 in Traumatic Brain and Spinal Cord Injury: Insight into Recent Advances in Actions of Neurochemokine Agents. Mol Neurobiol 2016; 54:2167-2188. [PMID: 26927660 PMCID: PMC5355526 DOI: 10.1007/s12035-016-9787-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 02/11/2016] [Indexed: 12/23/2022]
Abstract
CX3CL1 (fractalkine) is the only member of the CX3C (delta) subfamily of chemokines which is unique and combines the properties of both chemoattractant and adhesion molecules. The two-form ligand can exist either in a soluble form, like all other chemokines, and as a membrane-anchored molecule. CX3CL1 discloses its biological properties through interaction with one dedicated CX3CR1 receptor which belongs to a family of G protein-coupled receptors (GPCR). The CX3CL1/CX3CR1 axis acts in many physiological phenomena including those occurring in the central nervous system (CNS), by regulating the interactions between neurons, microglia, and immune cells. Apart from the role under physiological conditions, the CX3CL1/CX3CR1 axis was implied to have a role in different neuropathologies such as traumatic brain injury (TBI) and spinal cord injury (SCI). CNS injuries represent a serious public health problem, despite improvements in therapeutic management. To date, no effective treatment has been determined, so they constitute a leading cause of death and severe disability. The course of TBI and SCI has two consecutive poorly demarcated phases: the initial, primary injury and secondary injury. Recent evidence has implicated the role of the CX3CL1/CX3CR1 axis in neuroinflammatory processes occurring after CNS injuries. The importance of the CX3CL1/CX3CR1 axis in the pathophysiology of TBI and SCI in the context of systemic and direct local immune response is still under investigation. This paper, based on a review of the literature, updates and summarizes the current knowledge about CX3CL1/CX3CR1 axis involvement in TBI and SCI pathogenesis, indicating possible molecular and cellular mechanisms with a potential target for therapeutic intervention.
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Affiliation(s)
- Łukasz A Poniatowski
- Department of General and Experimental Pathology, 2nd Faculty of Medicine, Medical University of Warsaw, Pawińskiego 3C, 02-106, Warsaw, Poland.
| | - Piotr Wojdasiewicz
- Department of General and Experimental Pathology, 2nd Faculty of Medicine, Medical University of Warsaw, Pawińskiego 3C, 02-106, Warsaw, Poland.,Department of Rheumaorthopaedics, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Spartańska 1, 02-637, Warsaw, Poland.,Department of Neuroorthopaedics and Neurology, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Spartańska 1, 02-637, Warsaw, Poland
| | - Maciej Krawczyk
- 2nd Department of Neurology, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957, Warsaw, Poland.,Department of Pediatric and Neurological Rehabilitation, Faculty of Rehabilitation, Józef Piłsudski University of Physical Education, Marymoncka 34, 00-968, Warsaw, Poland
| | - Dariusz Szukiewicz
- Department of General and Experimental Pathology, 2nd Faculty of Medicine, Medical University of Warsaw, Pawińskiego 3C, 02-106, Warsaw, Poland
| | - Robert Gasik
- Department of Rheumaorthopaedics, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Spartańska 1, 02-637, Warsaw, Poland.,Department of Neuroorthopaedics and Neurology, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Spartańska 1, 02-637, Warsaw, Poland
| | - Łukasz Kubaszewski
- Department of Neuroorthopaedics and Neurology, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Spartańska 1, 02-637, Warsaw, Poland.,Department of Orthopaedics and Traumatology, Wiktor Dega Orthopaedic and Rehabilitation Clinical Hospital, Poznań University of Medical Sciences, 28 Czerwca 1956 135/147, 61-545, Poznań, Poland
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105
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Keenan CR, Lew MJ, Stewart AG. Biased signalling from the glucocorticoid receptor: Renewed opportunity for tailoring glucocorticoid activity. Biochem Pharmacol 2016; 112:6-12. [PMID: 26898958 DOI: 10.1016/j.bcp.2016.02.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 02/16/2016] [Indexed: 12/13/2022]
Abstract
Recent landmark studies applying analytical pharmacology approaches to the glucocorticoid receptor (GR) have demonstrated that different ligands can cause differential activation of distinct GR-regulated genes. Drawing on concepts of signalling bias from the field of G protein-coupled receptor (GPCR) biology, we speculate that ligand-dependent differences in GR signalling can be considered analogous to GPCR biased signalling, and thus can be quantitatively analysed in a similar way. This type of approach opens up the possibility of using rational structure-based drug optimisation strategies to improve the therapeutic selectivity of glucocorticoid drugs to maximise their efficacy and minimise adverse effects.
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Affiliation(s)
- Christine R Keenan
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Michael J Lew
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Alastair G Stewart
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, Victoria 3010, Australia.
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106
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Prihandoko R, Alvarez-Curto E, Hudson BD, Butcher AJ, Ulven T, Miller AM, Tobin AB, Milligan G. Distinct Phosphorylation Clusters Determine the Signaling Outcome of Free Fatty Acid Receptor 4/G Protein–Coupled Receptor 120. Mol Pharmacol 2016; 89:505-20. [DOI: 10.1124/mol.115.101949] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/11/2016] [Indexed: 12/27/2022] Open
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107
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Fan X, Gu X, Zhao R, Zheng Q, Li L, Yang W, Ding L, Xue F, Fan J, Gong Y, Wang Y. Cardiac β2-Adrenergic Receptor Phosphorylation at Ser355/356 Regulates Receptor Internalization and Functional Resensitization. PLoS One 2016; 11:e0161373. [PMID: 27541735 PMCID: PMC4991819 DOI: 10.1371/journal.pone.0161373] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 08/04/2016] [Indexed: 02/05/2023] Open
Abstract
Previous studies have demonstrated that β2-adrenergic receptors (β2ARs) can be phosphorylated by G protein-coupled receptor kinases (GRKs) and protein kinase A (PKA), affecting β2AR internalization and desensitization. However, the exact physiological function of β2ARs in cardiomyocytes is unknown. In this study, we showed that neonatal mouse cardiomyocytes had different contraction and internalization responses to sustained or repeated, transient agonist stimulation. Specifically, short-time stimulation (10 min) with epinephrine or norepinephrine increased the cardiomyocyte contraction rate, reaching a maximum at 5 min, followed by a slow decline. When the agonist was re-added after a 60-min wash-out period, the increase in the cardiomyocyte contraction rate was similar to the initial response. In contrast, when cardiomyocytes were exposed continuously to epinephrine or norepinephrine for 60 min, the second agonist stimulation did not increase the contraction response. These results indicated that continuous β2AR stimulation caused functional desensitization. Phosphorylation of β2ARs at serine (Ser)355/356 GRK phosphorylation sites, but not at Ser345/346 PKA phosphorylation sites increased with continuous epinephrine stimulation for 60 min. Accordingly, β2AR internalization increased. Interestingly, β2AR internalization was blocked by mutations at the GRK phosphorylation sites, but not by mutations at the PKA phosphorylation sites. Furthermore, inhibition of β2AR dephosphorylation by okadaic acid, a phosphatase 2A inhibitor, impaired the recovery of internalized β2ARs and reduced the cardiomyocyte contraction rate in response to epinephrine. Finally, epinephrine treatment induced the physical interaction of β-arrestin with internalized β2ARs in cardiomyocytes. Together, these data revealed the essential role of the Ser355/356 phosphorylation status of β2ARs in regulating receptor internalization and physiological resensitization in neonatal cardiomyocytes to contraction functions.
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MESH Headings
- Animals
- Animals, Newborn
- Cells, Cultured
- Epinephrine/pharmacology
- Female
- Kinetics
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Knockout
- Mutagenesis, Site-Directed
- Mutation/genetics
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Norepinephrine/pharmacology
- Phosphorylation/drug effects
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Adrenergic, beta-2/metabolism
- Serine/metabolism
- Signal Transduction/drug effects
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Affiliation(s)
- Xiaofang Fan
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Xuejiang Gu
- Department of Endocrine and Metabolic Diseases, 1 Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Ru Zhao
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Qingqing Zheng
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Lan Li
- Department of Pathology, Shantou University Medical College, Shantou, Guangdong, P.R. China
| | - Wenbing Yang
- Department of Pathology, Shantou University Medical College, Shantou, Guangdong, P.R. China
| | - Lu Ding
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Feng Xue
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Junming Fan
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
| | - Yongsheng Gong
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
- * E-mail: (YW); (YG)
| | - Yongyu Wang
- Institute of Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, P.R. China
- * E-mail: (YW); (YG)
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108
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“Barcode” and Differential Effects of GPCR Phosphorylation by Different GRKs. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2016. [DOI: 10.1007/978-1-4939-3798-1_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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109
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Sosa-Alvarado C, Hernández-Méndez A, Romero-Ávila MT, Sánchez-Reyes OB, Takei Y, Tsujimoto G, Hirasawa A, García-Sáinz JA. Agonists and protein kinase C-activation induce phosphorylation and internalization of FFA1 receptors. Eur J Pharmacol 2015; 768:108-15. [DOI: 10.1016/j.ejphar.2015.10.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 10/14/2015] [Accepted: 10/21/2015] [Indexed: 01/12/2023]
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110
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Phosphorylation and Internalization of Lysophosphatidic Acid Receptors LPA1, LPA2, and LPA3. PLoS One 2015; 10:e0140583. [PMID: 26473723 PMCID: PMC4608732 DOI: 10.1371/journal.pone.0140583] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/27/2015] [Indexed: 12/31/2022] Open
Abstract
Results The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation increases intracellular calcium concentration in a concentration-dependent fashion. Phorbol myristate acetate markedly inhibited LPA1- and LPA3-mediated effect, whereas that mediated by LPA2 was only partially diminished; the actions of the phorbol ester were inhibited by bisindolylmaleimide I and by overnight incubation with the protein kinase C activator, which leads to down regulation of this protein kinase. Homologous desensitization was also observed for the three LPA receptors studied, with that of LPA2 receptors being consistently of lesser magnitude; neither inhibition nor down-regulation of protein kinase C exerted any effect on homologous desensitization. Activation of LPA1–3 receptors induced ERK 1/2 phosphorylation; this effect was markedly attenuated by inhibition of epidermal growth factor receptor tyrosine kinase activity, suggesting growth factor receptor transactivation in this effect. Lysophosphatidic acid and phorbol myristate acetate were able to induce LPA1–3 phosphorylation, in time- and concentration-dependent fashions. It was also clearly observed that agonists and protein kinase C activation induced internalization of these receptors. Phosphorylation of the LPA2 subtype required larger concentrations of these agents and its internalization was less intense than that of the other subtypes. Conclusion Our data show that these three LPA receptors are phosphoproteins whose phosphorylation state is modulated by agonist-stimulation and protein kinase C-activation and that differences in regulation and cellular localization exist, among the subtypes.
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111
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Park F. Accessory proteins for heterotrimeric G-proteins in the kidney. Front Physiol 2015; 6:219. [PMID: 26300785 PMCID: PMC4528294 DOI: 10.3389/fphys.2015.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/20/2015] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center Memphis, TN, USA
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112
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Piscitelli CL, Kean J, de Graaf C, Deupi X. A Molecular Pharmacologist's Guide to G Protein-Coupled Receptor Crystallography. Mol Pharmacol 2015; 88:536-51. [PMID: 26152196 DOI: 10.1124/mol.115.099663] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/07/2015] [Indexed: 12/14/2022] Open
Abstract
G protein-coupled receptor (GPCR) structural biology has progressed dramatically in the last decade. There are now over 120 GPCR crystal structures deposited in the Protein Data Bank of 32 different receptors from families scattered across the phylogenetic tree, including class B, C, and Frizzled GPCRs. These structures have been obtained in combination with a wide variety of ligands and captured in a range of conformational states. This surge in structural knowledge has enlightened research into the molecular recognition of biologically active molecules, the mechanisms of receptor activation, the dynamics of functional selectivity, and fueled structure-based drug design efforts for GPCRs. Here we summarize the innovations in both protein engineering/molecular biology and crystallography techniques that have led to these advances in GPCR structural biology and discuss how they may influence the resulting structural models. We also provide a brief molecular pharmacologist's guide to GPCR X-ray crystallography, outlining some key aspects in the process of structure determination, with the goal to encourage noncrystallographers to interrogate structures at the molecular level. Finally, we show how chemogenomics approaches can be used to marry the wealth of existing receptor pharmacology data with the expanding repertoire of structures, providing a deeper understanding of the mechanistic details of GPCR function.
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Affiliation(s)
- Chayne L Piscitelli
- Laboratory of Biomolecular Research, Department of Biology and Chemistry (C.L.P., X.D.), and Condensed Matter Theory Group, Department of Research with Neutrons and Muons (X.D.), Paul Scherrer Institute, Villigen, Switzerland; Heptares Therapeutics Ltd., Welwyn Garden City, United Kingdom (J.K.); and Division of Medicinal Chemistry, Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems, VU University of Amsterdam, Amsterdam, The Netherlands (C.G.)
| | - James Kean
- Laboratory of Biomolecular Research, Department of Biology and Chemistry (C.L.P., X.D.), and Condensed Matter Theory Group, Department of Research with Neutrons and Muons (X.D.), Paul Scherrer Institute, Villigen, Switzerland; Heptares Therapeutics Ltd., Welwyn Garden City, United Kingdom (J.K.); and Division of Medicinal Chemistry, Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems, VU University of Amsterdam, Amsterdam, The Netherlands (C.G.)
| | - Chris de Graaf
- Laboratory of Biomolecular Research, Department of Biology and Chemistry (C.L.P., X.D.), and Condensed Matter Theory Group, Department of Research with Neutrons and Muons (X.D.), Paul Scherrer Institute, Villigen, Switzerland; Heptares Therapeutics Ltd., Welwyn Garden City, United Kingdom (J.K.); and Division of Medicinal Chemistry, Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems, VU University of Amsterdam, Amsterdam, The Netherlands (C.G.)
| | - Xavier Deupi
- Laboratory of Biomolecular Research, Department of Biology and Chemistry (C.L.P., X.D.), and Condensed Matter Theory Group, Department of Research with Neutrons and Muons (X.D.), Paul Scherrer Institute, Villigen, Switzerland; Heptares Therapeutics Ltd., Welwyn Garden City, United Kingdom (J.K.); and Division of Medicinal Chemistry, Faculty of Sciences, Amsterdam Institute for Molecules, Medicines and Systems, VU University of Amsterdam, Amsterdam, The Netherlands (C.G.)
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113
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Alfonzo MJ, Alfonzo RGD, Alfonzo González M, de Becemberg IL. Muscarinic drugs regulate the PKG-II-dependent phosphorylation of M3 muscarinic acetylcholine receptors at plasma membranes from airway smooth muscle. J Recept Signal Transduct Res 2015; 35:319-28. [PMID: 26053513 DOI: 10.3109/10799893.2014.982826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Muscarinic agonists induce the activation of the airway smooth muscle (ASM) leading to smooth muscle contraction, important in asthma. This activation is mediated through M2/M3 muscarinic acetylcholine receptors (mAChRs). Muscarinic receptor activity, expressed as [(3)H]QNB binding at plasma membranes from bovine tracheal smooth muscle (BTSM), increased with cGMP and was augmented significantly cGMP plus ATP but diminished with the PKG-II inhibitor, Sp-8-pCPT-cGMPS. The [(3)H]-QNB binding was accelerated by okadaic acid, (OKA), a protein phosphatase (PPase) inhibitor. These two results indicated the involvement of a membrane-bound PPase. Moreover, a cGMP-dependent-[(32)P]γATP phosphorylation of plasma membranes from BTSM was stimulated at low concentrations of muscarinic agonist carbamylcholine (CC). However, higher amounts of CC produced a significant decrement of [(32)P]-labeling. A selective M3mAChR antagonist, 4-DAMP produced a dramatic inhibition of the basal and CC-dependent [(32)P]-labeling. The [(32)P] labeled membrane sediments were detergent solubilized and immunoprecipitated with specific M2/M3mAChR antibodies. The M3mAChR immuno-precipitates exhibited the highest cGMP-dependent [(32)P]-labeling, indicating it is a PKG-II substrate. Experiments using synthetic peptides from the C-terminal of the third intracellular loop (i3) of both M2mAChR (356-369) and M3mAChR (480-493) as external PKG-II substrates resulted in the i3M3-peptide being heavily phosphorylated. These results indicated that PKG-II phosphorylated the M3mAChR at the i3M3 domain ((480)MSLIKEKK(485)), suggesting that Ser(481) may be the target. Finally, this phosphorylation site seems to be regulated by a membrane-bound PPase linked to muscarinic receptor. These findings are important to understand the role of M3mAChR in the patho-physiology of ASM involved in asthma and COPD.
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Affiliation(s)
- Marcelo J Alfonzo
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Ramona González de Alfonzo
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Marcelo Alfonzo González
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
| | - Itala Lippo de Becemberg
- a Facultad de Medicina, Sección de Biomembranas , Instituto de Medicina Experimental (IME), Universidad Central de Venezuela , Sabana Grande, Caracas , Venezuela
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114
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Prihandoko R, Bradley SJ, Tobin AB, Butcher AJ. Determination of GPCR Phosphorylation Status: Establishing a Phosphorylation Barcode. ACTA ACUST UNITED AC 2015; 69:2.13.1-2.13.26. [PMID: 26344213 DOI: 10.1002/0471141755.ph0213s69] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are rapidly phosphorylated following agonist occupation in a process that mediates receptor uncoupling from its cognate G protein, a process referred to as desensitization. In addition, this process provides a mechanism by which receptors can engage with arrestin adaptor molecules and couple to downstream signaling pathways. The importance of this regulatory process has been highlighted recently by the understanding that ligands can direct receptor signaling along one pathway in preference to another, the phenomenon of signaling bias that is partly mediated by the phosphorylation status or phosphorylation barcode of the receptor. Methods to determine the phosphorylation status of a GPCR in vitro and in vivo are necessary to understand not only the physiological mechanisms involved in GPCR signaling, but also to fully examine the signaling properties of GPCR ligands. This unit describes detailed methods for determining the overall phosphorylation pattern on a receptor (the phosphorylation barcode), as well as mass spectrometry approaches that can define the precise sites that become phosphorylated. These techniques, coupled with the generation and characterization of receptor phosphorylation-specific antibodies, provide a full palate of techniques necessary to determine the phosphorylation status of any given GPCR subtype.
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Affiliation(s)
- Rudi Prihandoko
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Sophie J Bradley
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Andrew B Tobin
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
| | - Adrian J Butcher
- MRC Toxicology Unit, University of Leicester, Leicester, United Kingdom
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115
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de Munnik SM, Kooistra AJ, van Offenbeek J, Nijmeijer S, de Graaf C, Smit MJ, Leurs R, Vischer HF. The Viral G Protein-Coupled Receptor ORF74 Hijacks β-Arrestins for Endocytic Trafficking in Response to Human Chemokines. PLoS One 2015; 10:e0124486. [PMID: 25894435 PMCID: PMC4403821 DOI: 10.1371/journal.pone.0124486] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 03/03/2015] [Indexed: 12/21/2022] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus-infected cells express the virally encoded G protein-coupled receptor ORF74. Although ORF74 is constitutively active, it binds human CXC chemokines that modulate this basal activity. ORF74-induced signaling has been demonstrated to underlie the development of the angioproliferative tumor Kaposi’s sarcoma. Whereas G protein-dependent signaling of ORF74 has been the subject of several studies, the interaction of this viral GPCR with β-arrestins has hitherto not been investigated. Bioluminescence resonance energy transfer experiments demonstrate that ORF74 recruits β-arrestins and subsequently internalizes in response to human CXCL1 and CXCL8, but not CXCL10. Internalized ORF74 traffics via early endosomes to recycling and late endosomes. Site-directed mutagenesis and homology modeling identified four serine and threonine residues at the distal end of the intracellular carboxyl-terminal of ORF74 that are required for β-arrestin recruitment and subsequent endocytic trafficking. Hijacking of the human endocytic trafficking machinery is a previously unrecognized action of ORF74.
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Affiliation(s)
- Sabrina M. de Munnik
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Albert J. Kooistra
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Jody van Offenbeek
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Saskia Nijmeijer
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Chris de Graaf
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Martine J. Smit
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Rob Leurs
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
| | - Henry F. Vischer
- Department of Chemistry and Pharmaceutical Sciences, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems (AIMMS), VU University Amsterdam, Amsterdam, The Netherlands
- * E-mail:
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Wang Y, Gao E, Lau WB, Wang Y, Liu G, Li JJ, Wang X, Yuan Y, Koch WJ, Ma XL. G-protein-coupled receptor kinase 2-mediated desensitization of adiponectin receptor 1 in failing heart. Circulation 2015; 131:1392-404. [PMID: 25696921 DOI: 10.1161/circulationaha.114.015248] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 02/13/2015] [Indexed: 01/23/2023]
Abstract
BACKGROUND Phosphorylative desensitization of G-protein-coupled receptors contributes significantly to post-myocardial infarction (MI) remodeling and heart failure (HF). Here, we determined whether adiponectin receptors (AdipoRs) 1 and 2 (the 7-transmembrane domain-containing receptors mediating adiponectin functions) are phosphorylatively modified and functionally impaired after MI. METHODS AND RESULTS Post-MI HF was induced by coronary artery occlusion. Receptor phosphorylation, kinase expression, and adiponectin function were determined via in vivo, ex vivo, and in vitro models. AdipoR1 and AdipoR2 are not phosphorylated in the normal heart. However, AdipoR1 was significantly phosphorylated after MI, peaking at 7 days and remaining significantly phosphorylated thereafter. The extent of post-MI AdipoR1 phosphorylation positively correlated with the expression level of GPCR kinase (GRK) 2, the predominant GRK isoform upregulated in the failing heart. Cardiac-specific GRK2 knockout virtually abolished post-MI AdipoR1 phosphorylation, whereas virus-mediated GRK2 overexpression significantly phosphorylated AdipoR1 and blocked adiponectin metabolic-regulatory/anti-inflammatory signaling. Mass spectrometry identified serine-7, threonine-24, and threonine-53 (residues located in the n-terminal intracellular AdipoR1 region) as the GRK2 phosphorylation sites. Ex vivo experiments demonstrated that adenosine monophosphate-activated protein kinase activation and the anti-tumor necrosis factor-α effect of adiponectin were significantly inhibited in cardiomyocytes isolated from nonischemic area 7 days after MI. In vivo experiments demonstrated that acute adiponectin administration-induced cardiac GLUT4 translocation and endothelial nitric oxide synthase phosphorylation were blunted 7 days after MI. Continuous adiponectin administration beginning 7 days after MI failed to protect the heart from adverse remodeling and HF progression. Finally, cardiac-specific GRK2 knockdown restored the cardioprotective effect of adiponectin. CONCLUSION AdipoR1 is phosphorylatively modified and desensitized by GRK2 in failing cardiomyocytes, contributing to post-MI remodeling and HF progression.
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Affiliation(s)
- Yajing Wang
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.).
| | - Erhe Gao
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Wayne Bond Lau
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Yang Wang
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Gaizheng Liu
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Jing-Jing Li
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Xiaoliang Wang
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Yuexing Yuan
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Walter J Koch
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.)
| | - Xin-Liang Ma
- From Department of Emergency Medicine (Y.W., W.B.L., Y.W., G.L., J.-J.L., X.W., Y.Y., X.-L.M.) and Center for Translational Medicine, Department of Medicine (X.-L.M.), Thomas Jefferson University, Philadelphia, PA; and Center for Translational Medicine, Temple University, Philadelphia, PA (E.G., W.J.K.).
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Evolutionary pattern in the OXT-OXTR system in primates: coevolution and positive selection footprints. Proc Natl Acad Sci U S A 2014; 112:88-93. [PMID: 25535371 DOI: 10.1073/pnas.1419399112] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oxytocin is a nonapeptide involved in a wide range of physiologic and behavioral functions. Until recently, it was believed that an unmodified oxytocin sequence was present in all placental mammals. This study analyzed oxytocin (OXT) in 29 primate species and the oxytocin receptor (OXTR) in 21 of these species. We report here three novel OXT forms in the New World monkeys, as well as a more extensive distribution of a previously described variant (Leu8Pro). In structural terms, these OXTs share the same three low-energy conformations in solution during molecular dynamic simulations, with subtle differences in their side chains. A consistent signal of positive selection was detected in the Cebidae family, and OXT position 8 showed a statistically significant (P = 0.013) correlation with litter size. Several OXTR changes were identified, some of them promoting gain or loss of putative phosphorylation sites, with possible consequences for receptor internalization and desensitization. OXTR amino acid sites are under positive selection, and intramolecular and intermolecular coevolutionary processes with OXT were also detected. We suggest that some New World monkey OXT-OXTR forms can be correlated to male parental care through the increase of cross-reactivity with its correlated vasopressin system.
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118
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Fahrenkrug J, Falktoft B, Georg B, Hannibal J, Kristiansen SB, Klausen TK. Phosphorylation of rat melanopsin at Ser-381 and Ser-398 by light/dark and its importance for intrinsically photosensitive ganglion cells (ipRGCs) cellular Ca2+ signaling. J Biol Chem 2014; 289:35482-93. [PMID: 25378407 PMCID: PMC4271233 DOI: 10.1074/jbc.m114.586529] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The G protein-coupled light-sensitive receptor melanopsin is involved in non-image-forming light responses including circadian timing. The predicted secondary structure of melanopsin indicates a long cytoplasmic tail with many potential phosphorylation sites. Using bioinformatics, we identified a number of amino acids with a high probability of being phosphorylated. We generated antibodies against melanopsin phosphorylated at Ser-381 and Ser-398, respectively. The antibody specificity was verified by immunoblotting and immunohistochemical staining of HEK-293 cells expressing rat melanopsin mutated in Ser-381 or Ser-398. Using the antibody recognizing phospho-Ser-381 melanopsin, we demonstrated by immunoblotting and immunohistochemical staining in HEK-293 cells expressing rat melanopsin that the receptor is phosphorylated in this position during the dark and dephosphorylated when light is turned on. On the contrary, we found that melanopsin at Ser-398 was unphosphorylated in the dark and became phosphorylated after light stimulation. The light-induced changes in phosphorylation at both Ser-381 and Ser-398 were rapid and lasted throughout the 4-h experimental period. Furthermore, phosphorylation at Ser-381 and Ser-398 was independent of each other. The changes in phosphorylation were confirmed in vivo by immunohistochemical staining of rat retinas during light and dark. We further demonstrated that mutation of Ser-381 and Ser-398 in melanopsin-expressing HEK-293 cells affected the light-induced Ca2+ response, which was significantly reduced as compared with wild type. Examining the light-evoked Ca2+ response in a melanopsin Ser-381 plus Ser-398 double mutant provided evidence that the phosphorylation events were independent.
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Affiliation(s)
- Jan Fahrenkrug
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Birgitte Falktoft
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Birgitte Georg
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Jens Hannibal
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Sarah B Kristiansen
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Thomas K Klausen
- Department of Biology, Faculty of Science, University of Copenhagen, DK-2200 Copenhagen N, Denmark
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Santhosh KT, Sikarwar AS, Hinton M, Chelikani P, Dakshinamurti S. Thromboxane receptor hyper-responsiveness in hypoxic pulmonary hypertension requires serine 324. Br J Pharmacol 2014; 171:676-87. [PMID: 24490858 DOI: 10.1111/bph.12487] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 09/21/2013] [Accepted: 10/03/2013] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Dysregulation of the thromboxane A₂ (TP) receptor, resulting in agonist hypersensitivity and hyper-responsiveness, contributes to exaggerated vasoconstriction in the hypoxic pulmonary artery in neonatal persistent pulmonary hypertension. We previously reported that hypoxia inhibits TP receptor phosphorylation, causing desensitization. Hence, we examined the role of PKA-accessible serine residues in determining TP receptor affinity, using site-directed mutational analysis. EXPERIMENTAL APPROACH Vasoconstriction to a thromboxane mimetic and phosphorylation of TP receptor serine was examined in pulmonary arteries from neonatal swine with persistent pulmonary hypertension and controls. Effects of hypoxia were determined in porcine and human TP receptors. Human TPα serines at positions 324, 329 and 331 (C-terminal tail) were mutated to alanine and transiently expressed in HEK293T cells. Saturation binding and displacement kinetics of a TP antagonist and agonist were determined in porcine TP, wild-type human TPα and all TP mutants. Agonist-elicited calcium mobilization was determined for each TP mutant, in the presence of a PKA activator or inhibitor, and in hypoxic and normoxic conditions. KEY RESULTS The Ser324A mutant was insensitive to PKA activation and hypoxia, had a high affinity for agonist and increased agonist-induced calcium mobilization. Ser329A was no different from wild-type TP receptors. Ser331A was insensitive to hypoxia and PKA with a decreased agonist-mediated response. CONCLUSIONS AND IMPLICATIONS In hypoxic pulmonary hypertension, loss of site-specific phosphorylation of the TP receptor causes agonist hyper-responsiveness. Ser324 is the primary residue phosphorylated by PKA, which regulates TP receptor-agonist interactions. Ser331 mutation confers loss of TP receptor-agonist interaction, regardless of PKA activity.
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Affiliation(s)
- K T Santhosh
- Biology of Breathing Group, Manitoba Institute of Child Health, Winnipeg, MB, Canada
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120
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Kurko D, Kapui Z, Nagy J, Lendvai B, Kolok S. Analysis of functional selectivity through G protein-dependent and -independent signaling pathways at the adrenergic α(2C) receptor. Brain Res Bull 2014; 107:89-101. [PMID: 25080296 DOI: 10.1016/j.brainresbull.2014.07.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 01/01/2023]
Abstract
Although G protein-coupled receptors (GPCRs) are traditionally categorized as Gs-, Gq-, or Gi/o-coupled, their signaling is regulated by multiple mechanisms. GPCRs can couple to several effector pathways, having the capacity to interact not only with more than one G protein subtype but also with alternative signaling or effector proteins such as arrestins. Moreover, GPCR ligands can have different efficacies for activating these signaling pathways, a characteristic referred to as biased agonism or functional selectivity. In this work our aim was to detect differences in the ability of various agonists acting at the α2C type of adrenergic receptors (α2C-ARs) to modulate cAMP accumulation, cytoplasmic Ca(2+) release, β-arrestin recruitment and receptor internalization. A detailed comparative pharmacological characterization of G protein-dependent and -independent signaling pathways was carried out using adrenergic agonists (norepinephrine, phenylephrine, brimonidine, BHT-920, oxymetazoline, clonidine, moxonidine, guanabenz) and antagonists (MK912, yohimbine). As initial analysis of agonist Emax and EC50 values suggested possible functional selectivity, ligand bias was quantified by applying the relative activity scale and was compared to that of the endogenous agonist norepinephrine. Values significantly different from 0 between pathways indicated an agonist that promoted different level of activation of diverse effector pathways most likely due to the stabilization of a subtly different receptor conformation from that induced by norepinephrine. Our results showed that a series of agonists acting at the α2C-AR displayed different degree of functional selectivity (bias factors ranging from 1.6 to 36.7) through four signaling pathways. As signaling via these pathways seems to have distinct functional and physiological outcomes, studying all these stages of receptor activation could have further implications for the development of more selective therapeutics with improved efficacy and/or fewer side effects.
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Affiliation(s)
- Dalma Kurko
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary.
| | - Zoltán Kapui
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - József Nagy
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - Balázs Lendvai
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - Sándor Kolok
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
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Blasic JR, Matos-Cruz V, Ujla D, Cameron EG, Hattar S, Halpern ME, Robinson PR. Identification of critical phosphorylation sites on the carboxy tail of melanopsin. Biochemistry 2014; 53:2644-9. [PMID: 24678795 PMCID: PMC4010260 DOI: 10.1021/bi401724r] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
![]()
Light-activated
opsins undergo carboxy-terminal phosphorylation,
which contributes to the deactivation of their photoresponse. The
photopigment melanopsin possesses an unusually long carboxy tail containing
37 serine and threonine sites that are potential sites for phosphorylation
by a G-protein dependent kinase (GRK). Here, we show that a small
cluster of six to seven sites is sufficient for deactivation of light-activated
mouse melanopsin. Surprisingly, these sites are distinct from those
that regulate deactivation of rhodopsin. In zebrafish, there are five
different melanopsin genes that encode proteins with distinct carboxy-terminal
domains. Naturally occurring changes in the same cluster of phosphorylatable
amino acids provides diversity in the deactivation kinetics of the
zebrafish proteins. These results suggest that variation in phosphorylation
sites provides flexibility in the duration and kinetics of melanopsin-mediated
light responses.
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Affiliation(s)
- Joseph R Blasic
- Department of Biological Sciences, University of Maryland, Baltimore County , Baltimore, Maryland 21250, United States
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Gao S, Malbon C, Wang HY. Probing the stoichiometry of β2-adrenergic receptor phosphorylation by targeted mass spectrometry. J Mol Signal 2014; 9:3. [PMID: 24690384 PMCID: PMC4022239 DOI: 10.1186/1750-2187-9-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 03/18/2014] [Indexed: 01/21/2023] Open
Abstract
Background Protein phosphorylation of G-protein-coupled receptors (GPCR) is central to the myriad of functions that these ubiquitous receptors perform in biology. Although readily addressable with the use of phospho-specific antibodies, analysis phosphorylation at the level of stoichiometry requires receptor isolation and advanced proteomics. We chose two key sites of potential phosphorylation of human beta2-adrenergic receptor (β2AR residues S355 and S356) to ascertain the feasibility of applying targeted mass spectrometry to establishing the stoichiometry of the phosphorylation. Method We stimulated HEK293 cells stably expressing Flag-tagged β2AR-eGFP with 10 μM beta-adrenergic agonist (isoproterenol) and made use of proteomics and targeted mass spectrometry (MS) to quantify the molar ration of phosphorylation on S355 and S356 versus non-phosphorylated receptor in agonist-treated cells. Results Phosphorylation of either S355 or S356 residue occurred only for agonist-occupied β2AR. The results demonstrated that pS356 is the dominant site of protein phosphorylation. The abundance of the p356 was 8.6-fold more than that of pS355. Calculation of the molar ratio of phosphorylated (pS355 plus pS356) versus non-phosphorylated receptor reveals that at high occupancy of the receptor only 12.4% of the β2AR is phosphorylated at these sites. Conclusions Application of advanced proteomics and use of the most sensitive targeted MS strategy makes possible the detection and quantification of phosphorylation of very low abundance peptide digests of β2AR. Establishing the stoichiometry of two key sites of agonist-stimulated phosphorylation with β2AR is an essential first-step to global analysis of the stoichiometry of GPCR phosphorylation.
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Affiliation(s)
- Shujuan Gao
- Department of Pharmacology, Health Sciences Center, School of Medicine, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
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C5L2 is required for C5a-triggered receptor internalization and ERK signaling. Cell Signal 2014; 26:1409-19. [PMID: 24631530 DOI: 10.1016/j.cellsig.2014.02.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 02/24/2014] [Indexed: 12/26/2022]
Abstract
C5L2 is a receptor that binds to C5a and belongs to the family of G protein-coupled receptors, but its role in physiological C5a-mediated responses remains under debate. Here we show that, like the canonical C5a receptor C5aR, C5L2 plays a pro-inflammatory role in a murine model of acute experimental colitis. We demonstrate that C5L2 physically interacts with C5aR and is required for optimal C5a-mediated C5aR internalization and associated ERK activation. Abrogation of C5a-induced receptor internalization by treatment with the dynamin inhibitor dynasore(TM) impaired C5a-induced MEK and ERK signaling. Although the presence of C5aR alone was sufficient to recruit the scaffold protein β-arrestin1 to the cell membrane in response to C5a stimulation, it was inadequate to mediate AP2 recruitment and subsequent C5aR internalization. Expression of C5L2 allowed normal internalization of C5aR in response to C5a stimulation, followed by normal ERK signaling. Thus, our work reveals an essential role for C5L2 in C5a-triggered, AP2-dependent C5aR internalization and downstream ERK signaling.
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Isoforms of protein kinase C involved in phorbol ester-induced sphingosine 1-phosphate receptor 1 phosphorylation and desensitization. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:327-34. [DOI: 10.1016/j.bbamcr.2013.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 11/04/2013] [Accepted: 11/07/2013] [Indexed: 12/11/2022]
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Pimentel-Santillana M, Través PG, Pérez-Sen R, Delicado EG, Martín-Sanz P, Miras-Portugal MT, Boscá L. Sustained release of prostaglandin E₂ in fibroblasts expressing ectopically cyclooxygenase 2 impairs P2Y-dependent Ca²⁺-mobilization. Mediators Inflamm 2014; 2014:832103. [PMID: 25214717 PMCID: PMC4151624 DOI: 10.1155/2014/832103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/01/2014] [Indexed: 02/07/2023] Open
Abstract
The nucleotide uridine trisphosphate (UTP) released to the extracellular milieu acts as a signaling molecule via activation of specific pyrimidine receptors (P2Y). P2Y receptors are G protein-coupled receptors expressed in many cell types. These receptors mediate several cell responses and they are involved in intracellular calcium mobilization. We investigated the role of the prostanoid PGE2 in P2Y signaling in mouse embryonic fibroblasts (MEFs), since these cells are involved in different ontogenic and physiopathological processes, among them is tissue repair following proinflammatory activation. Interestingly, Ca(2+)-mobilization induced by UTP-dependent P2Y activation was reduced by PGE2 when this prostanoid was produced by MEFs transfected with COX-2 or when PGE2 was added exogenously to the culture medium. This Ca(2+)-mobilization was important for the activation of different metabolic pathways in fibroblasts. Moreover, inhibition of COX-2 with selective coxibs prevented UTP-dependent P2Y activation in these cells. The inhibition of P2Y responses by PGE2 involves the activation of PKCs and PKD, a response that can be suppressed after pharmacological inhibition of these protein kinases. In addition to this, PGE2 reduces the fibroblast migration induced by P2Y-agonists such as UTP. Taken together, these data demonstrate that PGE2 is involved in the regulation of P2Y signaling in these cells.
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Affiliation(s)
- María Pimentel-Santillana
- 1Instituto de Investigaciones Biomédicas Alberto Sols, Centro Mixto CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain
| | - Paqui G. Través
- 1Instituto de Investigaciones Biomédicas Alberto Sols, Centro Mixto CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain
- 2The Salk Institute, 10010 N Torrey Pines Road, La Jolla, CA 92037, USA
| | - Raquel Pérez-Sen
- 3Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria e Instituto Universitario de Investigación en Neuroquímica, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Universidad Complutense, Madrid, Spain
| | - Esmerilda G. Delicado
- 3Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria e Instituto Universitario de Investigación en Neuroquímica, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Universidad Complutense, Madrid, Spain
| | - Paloma Martín-Sanz
- 1Instituto de Investigaciones Biomédicas Alberto Sols, Centro Mixto CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain
- 4Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberehd), Spain
| | - María Teresa Miras-Portugal
- 3Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria e Instituto Universitario de Investigación en Neuroquímica, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Universidad Complutense, Madrid, Spain
| | - Lisardo Boscá
- 1Instituto de Investigaciones Biomédicas Alberto Sols, Centro Mixto CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain
- 3Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria e Instituto Universitario de Investigación en Neuroquímica, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), Universidad Complutense, Madrid, Spain
- 4Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberehd), Spain
- *Lisardo Boscá:
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Abstract
It is now established that agonists do not uniformly activate pleiotropic signaling mechanisms initiated by receptors but rather can bias signals according to the unique receptor conformations they stabilize. One of the important emerging signaling systems where this can occur is through β-arrestin. This chapter discusses biased signaling where emphasis or de-emphasis of β-arrestin signaling is postulated (or been shown) to be beneficial. The chapter specifically focuses on methods to quantify biased effects; these methods furnish scales that can be used in the process of optimizing biased agonism (and antagonism) for therapeutic benefit. Specifically, methods to derive ΔΔLog(τ/K A) or ΔΔLog(Relative Activity) values are described to do this.
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Affiliation(s)
- Terry Kenakin
- Department of Pharmacology, University of North Carolina School of Medicine, 120 Mason Farm Road, Room 4042, Genetic Medicine Building, CB# 7365, Chapel Hill, NC, 27599-7365, USA,
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Hernández-Méndez A, Alcántara-Hernández R, Acosta-Cervantes GC, Martínez-Ortiz J, Avendaño-Vázquez SE, García-Sáinz JA. Conventional protein kinase C isoforms mediate phorbol ester-induced lysophosphatidic acid LPA1 receptor phosphorylation. Eur J Pharmacol 2013; 723:124-30. [PMID: 24355769 DOI: 10.1016/j.ejphar.2013.11.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 11/26/2013] [Accepted: 11/28/2013] [Indexed: 01/16/2023]
Abstract
Using C9 cells stably expressing LPA1 receptors fused to the enhanced green fluorescent protein, it was observed that activation of protein kinase C induced a rapid and strong increase in the phosphorylation state of these receptors. Overnight incubation with phorbol esters markedly decreased the amount of conventional (α, βI, βII and γ) and novel (δ) but not atypical (ζ) immunodetected PKC isoforms, this treatment blocks the action of protein kinase on receptor function and phosphorylation. Bis-indolylmaleimide I a general, non-subtype selective protein kinase C inhibitor, and Gö 6976, selective for the isoforms α and β, were also able to block LPA1 receptor desensitization and phosphorylation; hispidin, isoform β-selective blocker partially avoided receptor desensitization. Expression of dominant-negative protein kinase C α or β II mutants and knocking down the expression of these kinase isozymes markedly decreased phorbol ester-induced LPA1 receptor phosphorylation without avoiding receptor desensitization. This effect was blocked by bis-indolyl-maleimide and Gö 6976, suggesting that these genetic interventions were not completely effective. It was also observed that protein kinase C α and β II isozymes co-immunoprecipitate with LPA1 receptors and that such an association was further increased by cell treatments with phorbol esters or lysophosphatidic acid. Our data suggest that conventional protein kinase C α and β isozymes modulate LPA1 receptor phosphorylation state. Receptor desensitization appears to be a more complex process that might involve additional elements.
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Affiliation(s)
- Aurelio Hernández-Méndez
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico
| | - Rocío Alcántara-Hernández
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico
| | - Germán C Acosta-Cervantes
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico
| | - Javier Martínez-Ortiz
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico
| | - S Eréndira Avendaño-Vázquez
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico
| | - J Adolfo García-Sáinz
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F-04510, Mexico.
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128
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Zhang L, Loh HH, Law PY. A novel noncanonical signaling pathway for the μ-opioid receptor. Mol Pharmacol 2013; 84:844-53. [PMID: 24061856 DOI: 10.1124/mol.113.088278] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The µ-opioid receptor (OPRM1) signals as a classic G protein-coupled receptor by activating heterotrimeric Gi/Go proteins resulting in adenylyl cyclase (AC) inhibition. Such AC inhibition is desensitized after prolonged agonist treatment. However, after receptor desensitization, the intracellular cAMP level remains regulated by OPRM1, as demonstrated by the intracellular cAMP level increase or AC superactivation upon removal of an agonist or addition of an antagonist. We now demonstrate that such intracellular cAMP regulation is mediated by a novel noncanonical signaling pathway resulting from OPRM1 being converted to a receptor tyrosine kinase (RTK)-like entity. This noncanonical OPRM1 signaling is initiated by the receptor recruiting and activating Src kinase within the receptor complex, leading to phosphorylation of the OPRM1 Tyr(336) residue. Phospho-Tyr(336) serves as the docking site for growth factor receptor-bound protein/son of sevenless, leading to the recruitment and activation of the Ras/Raf-1 and subsequent phosphorylation and activation of AC5/6 by Raf-1. Such sequence of events was established by the absence of Ras/Raf1 recruitment and activation by the OPRM1-Y336F mutant, by the presence of Src kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) or the absence of Src activity, by the presence of specific Raf-1 inhibitor GW5074 (5-iodo-3-[(3,5-dibromo-4-hydroxyphenyl) methylene]-2-indolinone) or the absence of Raf-1, or by the dominant negative RasN17 mutant. Src together with Ras activates Raf1 which was established by the inability of the Raf1-Tyr(340/341) mutant to activate AC. Hence, the phosphorylation of OPRM1 at Tyr(336) by Src serves as the trigger for the conversion of a classic Gi/Go-coupled receptor into an RTK-like entity, resulting in a noncanonical pathway even after the original Gi/Go signals are blunted.
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Affiliation(s)
- Lei Zhang
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota
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129
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Lowther KM, Uliasz TF, Götz KR, Nikolaev VO, Mehlmann LM. Regulation of Constitutive GPR3 Signaling and Surface Localization by GRK2 and β-arrestin-2 Overexpression in HEK293 Cells. PLoS One 2013; 8:e65365. [PMID: 23826079 PMCID: PMC3694969 DOI: 10.1371/journal.pone.0065365] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 04/30/2013] [Indexed: 01/06/2023] Open
Abstract
G protein-coupled receptor 3 (GPR3) is a constitutively active receptor that maintains high 3′-5′-cyclic adenosine monophosphate (cAMP) levels required for meiotic arrest in oocytes and CNS function. Ligand-activated G protein-coupled receptors (GPCRs) signal at the cell surface and are silenced by phosphorylation and β-arrestin recruitment upon endocytosis. Some GPCRs can also signal from endosomes following internalization. Little is known about the localization, signaling, and regulation of constitutively active GPCRs. We demonstrate herein that exogenously-expressed GPR3 localizes to the cell membrane and undergoes internalization in HEK293 cells. Inhibition of endocytosis increased cell surface-localized GPR3 and cAMP levels while overexpression of GPCR-Kinase 2 (GRK2) and β-arrestin-2 decreased cell surface-localized GPR3 and cAMP levels. GRK2 by itself is sufficient to decrease cAMP production but both GRK2 and β-arrestin-2 are required to decrease cell surface GPR3. GRK2 regulates GPR3 independently of its kinase activity since a kinase inactive GRK2-K220R mutant significantly decreased cAMP levels. However, GRK2-K220R and β-arrestin-2 do not diminish cell surface GPR3, suggesting that phosphorylation is required to induce GPR3 internalization. To understand which residues are targeted for desensitization, we mutated potential phosphorylation sites in the third intracellular loop and C-terminus and examined the effect on cAMP and receptor surface localization. Mutation of residues in the third intracellular loop dramatically increased cAMP levels whereas mutation of residues in the C-terminus produced cAMP levels comparable to GPR3 wild type. Interestingly, both mutations significantly reduced cell surface expression of GPR3. These results demonstrate that GPR3 signals at the plasma membrane and can be silenced by GRK2/β-arrestin overexpression. These results also strongly implicate the serine and/or threonine residues in the third intracellular loop in the regulation of GPR3 activity.
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Affiliation(s)
- Katie M Lowther
- Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut, United States of America
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130
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Hierarchical organization of multi-site phosphorylation at the CXCR4 C terminus. PLoS One 2013; 8:e64975. [PMID: 23734232 PMCID: PMC3666969 DOI: 10.1371/journal.pone.0064975] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 04/23/2013] [Indexed: 01/07/2023] Open
Abstract
The chemokine receptor CXCR4 regulates cell migration during ontogenesis and disease states including cancer and inflammation. Upon stimulation by the endogenous ligand CXCL12, CXCR4 becomes phosphorylated at multiple sites in its C-terminal domain. Mutations in the CXCR4 gene affecting C-terminal phosphorylation sites are a hallmark of WHIM syndrome, a genetic disorder characterized by a gain-of-CXCR4-function. To better understand how multi-site phosphorylation of CXCR4 is organized and how perturbed phosphorylation might affect CXCR4 function, we developed novel phosphosite-specific CXCR4 antibodies and studied the differential regulation and interaction of three C-terminal phosphorylation sites in human embryonic kidney cells (HEK293). CXCL12 promoted a robust phosphorylation at S346/347 which preceded phosphorylation at S324/325 and S338/339. After CXCL12 washout, the phosphosites S338/339 and S324/325 were rapidly dephosphorylated whereas phosphorylation at S346/347 was long-lasting. CXCL12-induced phosphorylation at S346/347 was staurosporine-insensitive and mediated by GRK2/3. WHIM syndrome-associated CXCR4 truncation mutants lacking the S346/347 phosphosite and the recently identified E343K WHIM mutant displayed strongly impaired phosphorylation at S324/325 and S338/339 as well as reduced CXCL12-induced receptor internalization. Relevance of the S346-S348 site was confirmed by a S346-348A mutant showing strongly impaired CXCL12-promoted phosphorylation at S324/325 and S338/339, defective internalization, gain of calcium mobilization, and reduced desensitization. Thus, the triple serine motif S346-S348 contains a major initial CXCR4 phosphorylation site and is required for efficient subsequent multi-site phosphorylation and receptor regulation. Hierarchical organization of CXCR4 phosphorylation explains why small deletions at the extreme CXCR4 C terminus typically associated with WHIM syndrome severely alter CXCR4 function.
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131
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Cho DI, Zheng M, Min C, Kwon KJ, Shin CY, Choi HK, Kim KM. ARF6 and GASP-1 are post-endocytic sorting proteins selectively involved in the intracellular trafficking of dopamine D₂ receptors mediated by GRK and PKC in transfected cells. Br J Pharmacol 2013; 168:1355-74. [PMID: 23082996 PMCID: PMC3596642 DOI: 10.1111/bph.12025] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 09/07/2012] [Accepted: 09/28/2012] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE GPCRs undergo both homologous and heterologous regulatory processes in which receptor phosphorylation plays a critical role. The protein kinases responsible for each pathway are well established; however, other molecular details that characterize each pathway remain unclear. In this study, the molecular mechanisms that determine the differences in the functional roles and intracellular trafficking between homologous and PKC-mediated heterologous internalization pathways for the dopamine D₂ receptor were investigated. EXPERIMENTAL APPROACH All of the S/T residues located within the intracellular loops of D₂ receptor were mutated, and the residues responsible for GRK- and PKC-mediated internalization were determined in HEK-293 cells and SH-SY5Y cells. The functional role of receptor internalization and the cellular components that determine the post-endocytic fate of internalized D₂ receptors were investigated in the transfected cells. KEY RESULTS T134, T225/S228/S229 and S325 were involved in PKC-mediated D₂ receptor desensitization. S229 and adjacent S/T residues mediated the PKC-dependent internalization of D₂ receptors, which induced down-regulation and desensitization. S/T residues within the second intracellular loop and T225 were the major residues involved in GRK-mediated internalization of D₂ receptors, which induced receptor resensitization. ARF6 mediated the recycling of D₂ receptors internalized in response to agonist stimulation. In contrast, GASP-1 mediated the down-regulation of D₂ receptors internalized in a PKC-dependent manner. CONCLUSIONS AND IMPLICATIONS GRK- and PKC-mediated internalizations of D₂ receptors occur through different intracellular trafficking pathways and mediate distinct functional roles. Distinct S/T residues within D₂ receptors and different sorting proteins are involved in the dissimilar regulation of D₂ receptors by GRK2 and PKC.
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Affiliation(s)
- D I Cho
- Department of Pharmacology, College of Pharmacy, Drug Development Research Institute, Chonnam National University, Gwang-Ju, Korea
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132
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Kenakin T. New concepts in pharmacological efficacy at 7TM receptors: IUPHAR review 2. Br J Pharmacol 2013; 168:554-75. [PMID: 22994528 PMCID: PMC3579279 DOI: 10.1111/j.1476-5381.2012.02223.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 08/03/2012] [Accepted: 09/12/2012] [Indexed: 01/14/2023] Open
Abstract
The present-day concept of drug efficacy has changed completely from its original description as the property of agonists that causes tissue activation. The ability to visualize the multiple behaviours of seven transmembrane receptors has shown that drugs can have many efficacies and also that the transduction of drug stimulus to various cellular stimulus-response cascades can be biased towards some but not all pathways. This latter effect leads to agonist 'functional selectivity', which can be favourable for the improvement of agonist therapeutics. However, in addition, biased agonist potency becomes cell type dependent with the loss of the monotonic behaviour of stimulus-response mechanisms, leading to potential problems in agonist quantification. This has an extremely important effect on the discovery process for new agonists since it now cannot be assumed that a given screening or lead optimization assay will correctly predict therapeutic behaviour. This review discusses these ideas and how new approaches to quantifying agonist effect may be used to circumvent the cell type dependence of agonism. This article, written by a corresponding member of the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR), reviews our current understanding of the interaction of ligands with seven transmembrane receptors. Further information on these pharmacological concepts is being incorporated into the IUPHAR/BPS database GuideToPharmacology.org.
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Affiliation(s)
- Terry Kenakin
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC, USA.
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133
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Prabakaran S, Lippens G, Steen H, Gunawardena J. Post-translational modification: nature's escape from genetic imprisonment and the basis for dynamic information encoding. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2012; 4:565-83. [PMID: 22899623 DOI: 10.1002/wsbm.1185] [Citation(s) in RCA: 223] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We discuss protein post-translational modification (PTM) from an information processing perspective. PTM at multiple sites on a protein creates a combinatorial explosion in the number of potential 'mod-forms', or global patterns of modification. Distinct mod-forms can elicit distinct downstream responses, so that the overall response depends partly on the effectiveness of a particular mod-form to elicit a response and partly on the stoichiometry of that mod-form in the molecular population. We introduce the 'mod-form distribution'-the relative stoichiometries of each mod-form-as the most informative measure of a protein's state. Distinct mod-form distributions may summarize information about distinct cellular and physiological conditions and allow downstream processes to interpret this information accordingly. Such information 'encoding' by PTMs may facilitate evolution by weakening the need to directly link upstream conditions to downstream responses. Mod-form distributions provide a quantitative framework in which to interpret ideas of 'PTM codes' that are emerging in several areas of biology, as we show by reviewing examples of ion channels, GPCRs, microtubules, and transcriptional co-regulators. We focus particularly on examples other than the well-known 'histone code', to emphasize the pervasive use of information encoding in molecular biology. Finally, we touch briefly on new methods for measuring mod-form distributions.
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134
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Kenakin T. Casting a wider net: whole-cell assays to capture varied and biased signaling. Mol Pharmacol 2012; 82:571-4. [PMID: 22828801 DOI: 10.1124/mol.112.081117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The observation of complex receptor behaviors has shown how ligands can have multiple efficacies and can also differentially stimulate certain cellular signaling pathways over others (i.e., biased signaling). Conventional pharmacological assays (usually proximal to the receptor) will detect ligands that produce the signal defined by the assay (i.e., Ca²⁺, cAMP, and others) but otherwise may miss biased ligands that produce little activation of pathways not measured by the assay. In theory, this is less of a hazard for generic whole-cell assays, which may be sensitive to multiple signaling inputs. Whole-cell assays have the advantage of detecting effects induced by a variety of receptor interactions with cytosolic proteins, including those that may be previously unknown. These ideas are discussed within the context of the high-throughput flow cytometry measurement of receptor internalization described by Wu et al. in the current issue of the journal. The internalization of receptors can be a useful therapeutic modality and the article by Wu et al. illustrates how this new assay, targeted to downstream cellular effects, can uncover unique ligand efficacies linked to receptor internalization.
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Affiliation(s)
- Terry Kenakin
- Department of Pharmacology, University of North Carolina School of Medicine, 120 Mason Farm Rd., Room 4042 Genetic Medicine Building, CB#7365, Chapel Hill, NC 27599-7365, USA.
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135
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Agonist activation and analysis. Biophysics (Nagoya-shi) 2012. [DOI: 10.1017/cbo9781139035002.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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136
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Butcher AJ, Kong KC, Prihandoko R, Tobin AB. Physiological role of G-protein coupled receptor phosphorylation. Handb Exp Pharmacol 2012:79-94. [PMID: 22222696 DOI: 10.1007/978-3-642-23274-9_5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is now well established that G-protein coupled receptors (GPCRs) are hyper-phosphorylated following agonist occupation usually at serine and threonine residues contained on the third intracellular loop and C-terminal tail. After some 2 decades of intensive research, the nature of protein kinases involved in this process together with the signalling consequences of receptor phosphorylation has been firmly established. The major challenge that the field currently faces is placing all this information within a physiological context and determining to what extent does phosphoregulation of GPCRs impact on whole animal responses. In this chapter, we address this issue by describing how GPCR phosphorylation might vary depending on the cell type in which the receptor is expressed and how this might be employed to drive selective regulation of physiological responses.
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Affiliation(s)
- Adrian J Butcher
- Department of Cell Physiology and Pharmacology, University of Leicester, Hodgkin Building, Lancaster Road, Leicester, LE1 9HN, UK
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137
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Unknown Mechanisms Regulating the GPCR Signal Cascade in Vertebrate Photoreceptors. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11055-011-9551-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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138
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Vischer HF, Watts AO, Nijmeijer S, Leurs R. G protein-coupled receptors: walking hand-in-hand, talking hand-in-hand? Br J Pharmacol 2011; 163:246-60. [PMID: 21244374 DOI: 10.1111/j.1476-5381.2011.01229.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Most cells express a panel of different G protein-coupled receptors (GPCRs) allowing them to respond to at least a corresponding variety of extracellular ligands. In order to come to an integrative well-balanced functional response these ligand-receptor pairs can often cross-regulate each other. Although most GPCRs are fully capable to induce intracellular signalling upon agonist binding on their own, many GPCRs, if not all, appear to exist and function in homomeric and/or heteromeric assemblies for at least some time. Such heteromeric organization offers unique allosteric control of receptor pharmacology and function between the protomers and might even unmask 'new' features. However, it is important to realize that some functional consequences that are proposed to originate from heteromeric receptor interactions may also be observed due to intracellular crosstalk between signalling pathways of non-associated GPCRs.
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Affiliation(s)
- Henry F Vischer
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
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139
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Polter AM, Li X. Glycogen Synthase Kinase-3 is an Intermediate Modulator of Serotonin Neurotransmission. Front Mol Neurosci 2011; 4:31. [PMID: 22028682 PMCID: PMC3199786 DOI: 10.3389/fnmol.2011.00031] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 09/28/2011] [Indexed: 01/22/2023] Open
Abstract
Serotonin is a neurotransmitter with broad functions in brain development, neuronal activity, and behaviors; and serotonin is the prominent drug target in several major neuropsychiatric diseases. The multiple actions of serotonin are mediated by diverse serotonin receptor subtypes and associated signaling pathways. However, the key signaling components that mediate specific function of serotonin neurotransmission have not been fully identified. This review will provide evidence from biochemical, pharmacological, and animal behavioral studies showing that serotonin regulates the activation states of brain glycogen synthase kinase-3 (GSK3) via type 1 and type 2 serotonin receptors. In return, GSK3 directly interacts with serotonin receptors in a highly selective manner, with a prominent effect on modulating serotonin 1B receptor activity. Therefore, GSK3 acts as an intermediate modulator in the serotonin neurotransmission system, and balanced GSK3 activity is essential for serotonin-regulated brain function and behaviors. Particularly important, several classes of serotonin-modulating drugs, such as antidepressants and atypical antipsychotics, regulate GSK3 by inhibiting its activity in brain, which reinforces the importance of GSK3 as a potential therapeutic target in neuropsychiatric diseases associated with abnormal serotonin function.
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Affiliation(s)
- Abigail M Polter
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham Birmingham, AL, USA
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140
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Alvarez-Curto E, Prihandoko R, Tautermann CS, Zwier JM, Pediani JD, Lohse MJ, Hoffmann C, Tobin AB, Milligan G. Developing chemical genetic approaches to explore G protein-coupled receptor function: validation of the use of a receptor activated solely by synthetic ligand (RASSL). Mol Pharmacol 2011; 80:1033-46. [PMID: 21880827 DOI: 10.1124/mol.111.074674] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Molecular evolution and chemical genetics have been applied to generate functional pairings of mutated G protein-coupled receptors (GPCRs) and nonendogenous ligands. These mutant receptors, referred to as receptors activated solely by synthetic ligands (RASSLs) or designer receptors exclusively activated by designer drugs (DREADDs), have huge potential to define physiological roles of GPCRs and to validate receptors in animal models as therapeutic targets to treat human disease. However, appreciation of ligand bias and functional selectivity of different ligands at the same receptor suggests that RASSLs may signal differently than wild-type receptors activated by endogenous agonists. We assessed this by generating forms of wild-type human M(3) muscarinic receptor and a RASSL variant that responds selectively to clozapine N-oxide. Although the RASSL receptor had reduced affinity for muscarinic antagonists, including atropine, stimulation with clozapine N-oxide produced effects very similar to those generated by acetylcholine at the wild-type M(3)-receptor. Such effects included the relative movement of the third intracellular loop and C-terminal tail of intramolecular fluorescence resonance energy transfer sensors and the ability of the wild type and evolved mutant to regulate extracellular signal-regulated kinase 1/2 phosphorylation. Each form interacted similarly with β-arrestin 2 and was internalized from the cell surface in response to the appropriate ligand. Furthermore, the pattern of phosphorylation of specific serine residues within the evolved receptor in response to clozapine N-oxide was very similar to that produced by acetylcholine at the wild type. Such results provide confidence that, at least for the M(3) muscarinic receptor, results obtained after transgenic expression of this RASSL are likely to mirror the actions of acetylcholine at the wild type receptor.
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Affiliation(s)
- Elisa Alvarez-Curto
- Molecular Pharmacology Group, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
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141
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Szopa P, Lipniacki T, Kazmierczak B. Exact solutions to a spatially extended model of kinase-receptor interaction. Phys Biol 2011; 8:055005. [PMID: 21832804 DOI: 10.1088/1478-3975/8/5/055005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
B and Mast cells are activated by the aggregation of the immune receptors. Motivated by this phenomena we consider a simple spatially extended model of mutual interaction of kinases and membrane receptors. It is assumed that kinase activates membrane receptors and in turn the kinase molecules bound to the active receptors are activated by transphosphorylation. Such a type of interaction implies positive feedback and may lead to bistability. In this study we apply the Steklov eigenproblem theory to analyze the linearized model and find exact solutions in the case of non-uniformly distributed membrane receptors. This approach allows us to determine the critical value of receptor dephosphorylation rate at which cell activation (by arbitrary small perturbation of the inactive state) is possible. We found that cell sensitivity grows with decreasing kinase diffusion and increasing anisotropy of the receptor distribution. Moreover, these two effects are cooperating. We showed that the cell activity can be abruptly triggered by the formation of the receptor aggregate. Since the considered activation mechanism is not based on receptor crosslinking by polyvalent antigens, the proposed model can also explain B cell activation due to receptor aggregation following binding of monovalent antigens presented on the antigen presenting cell.
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Affiliation(s)
- Piotr Szopa
- Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland.
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142
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Kao YJ, Ghosh M, Schonbrunn A. Ligand-dependent mechanisms of sst2A receptor trafficking: role of site-specific phosphorylation and receptor activation in the actions of biased somatostatin agonists. Mol Endocrinol 2011; 25:1040-54. [PMID: 21493671 DOI: 10.1210/me.2010-0398] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The somatostatin receptor subtype 2A (sst2A) mediates many of somatostatin's neuroendocrine actions and is the primary therapeutic target for the stable somatostatin analogs used to inhibit hormone secretion by pituitary and gastroenteropancreatic tumors. Two new multireceptor targeting somatostatin analogs currently under clinical investigation, the multisomatostatin receptor agonist cyclo-[diaminoethylcarbamoyl-HydroxyPro-Phenylglycine-D-Trp-Lys-(4-O-benzyl)Tyr-Phe] (SOM230) (Pasireotide) and pan-somatostatin receptor agonist Tyr-cyclo-[D-diaminobutyric acid-Arg-Phe-Phe-D-Trp-Lys-Thr-Phe] (KE108), behave as functionally selective ligands at the sst2A receptor, mimicking some of somatostatin's actions but antagonizing others. Further, SOM230 and KE108 are less able to induce receptor internalization than somatostatin, indicating that they exhibit functional selectivity for receptor regulation as well as signaling. Here, we identify agonist-specific differences in the molecular events regulating sst2A receptor endocytosis. SOM230 and KE108 were less potent and less effective than somatostatin at stimulating sst2A receptor phosphorylation at two pairs of residues, Ser341/343 and Thr353/354. Only the pattern of Thr353/354 phosphorylation correlated with receptor internalization, consistent with the known importance of Thr phosphorylation for sst2A receptor endocytosis. As expected, arrestin recruitment to membrane receptors was reduced with SOM230 and KE108. In addition, both receptor dephosphorylation and receptor recycling occurred more rapidly with SOM230 and KE108 than with somatostatin. Surprisingly, however, SOM230 and KE108 also altered sst2A internalization in a phosphorylation-independent manner, because these analogs were less effective than somatostatin at stimulating the endocytosis of a phosphorylation-negative receptor mutant. These results show that the decreased receptor internalization produced by SOM230 and KE108 compared with somatostatin result from phosphorylation-independent effects as well as reduced site-specific receptor phosphorylation and receptor-arrestin association.
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Affiliation(s)
- Yachu J Kao
- Department of Integrative Biology and Pharmacology, University of Texas, Health Science Center-Houston, Houston, Texas 77030, USA
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143
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Daaka Y. S-nitrosylation-regulated GPCR signaling. Biochim Biophys Acta Gen Subj 2011; 1820:743-51. [PMID: 21397660 DOI: 10.1016/j.bbagen.2011.03.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 02/26/2011] [Accepted: 03/04/2011] [Indexed: 01/14/2023]
Abstract
G protein-coupled receptors (GPCRs) are the most numerous and diverse type of cell surface receptors, accounting for about 1% of the entire human genome and relaying signals from a variety of extracellular stimuli that range from lipid and peptide growth factors to ions and sensory inputs. Activated GPCRs regulate a multitude of target cell functions, including intermediary metabolism, growth and differentiation, and migration and invasion. The GPCRs contain a characteristic 7-transmembrane domain topology and their activation promotes complex formation with a variety of intracellular partner proteins, which form basis for initiation of distinct signaling networks as well as dictate fate of the receptor itself. Both termination of active GPCR signaling and removal from the plasma membrane are controlled by protein post-translational modifications of the receptor itself and its interacting partners. Phosphorylation, acylation and ubiquitination are the most studied post-translational modifications involved in GPCR signal transduction, subcellular trafficking and overall expression. Emerging evidence demonstrates that protein S-nitrosylation, the covalent attachment of a nitric oxide moiety to specified cysteine thiol groups, of GPCRs and/or their associated effectors also participates in the fine-tuning of receptor signaling and expression. This newly appreciated mode of GPCR system modification adds another set of controls to more precisely regulate the many cellular functions elicited by this large group of receptors. This article is part of a Special Issue entitled: Regulation of cellular processes by S-nitrosylation.
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Affiliation(s)
- Yehia Daaka
- The Department of Microbiology and Immunology, University of California, San Francisco, CA, United States.
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144
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Ghosh M, Schonbrunn A. Differential temporal and spatial regulation of somatostatin receptor phosphorylation and dephosphorylation. J Biol Chem 2011; 286:13561-73. [PMID: 21343287 DOI: 10.1074/jbc.m110.215723] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The G(i)-coupled somatostatin 2A receptor (sst2A) mediates many of the neuromodulatory and neuroendocrine actions of somatostatin (SS) and is targeted by the SS analogs used to treat neuroendocrine tumors. As for other G protein-coupled receptors, agonists stimulate sst2A receptor phosphorylation on multiple residues, and phosphorylation at different sites has distinct effects on receptor internalization and uncoupling. To elucidate the spatial and temporal regulation of sst2A receptor phosphorylation, we examined agonist-stimulated phosphorylation of multiple receptor GPCR kinase sites using phospho-site-specific antibodies. SS increased receptor phosphorylation sequentially, first on Ser-341/343 and then on Thr-353/354, followed by receptor internalization. Reversal of receptor phosphorylation was determined by the duration of prior agonist exposure. In acutely stimulated cells, in which most receptors remained on the cell surface, dephosphorylation occurred only on Thr-353/354. In contrast, both Ser-341/343 and Thr-353/354 were rapidly dephosphorylated when cells were stimulated long enough to allow receptor internalization before agonist removal. Consistent with these observations, dephosphorylation of Thr-353/354 was not affected by either hypertonic sucrose or dynasore, which prevent receptor internalization, whereas dephosphorylation of Ser-341/343 was completely blocked. An okadaic acid- and fostriecin-sensitive phosphatase catalyzed the dephosphorylation of Thr-353/354 both intracellularly and at the cell surface. In contrast, dephosphorylation of Ser-341/343 was insensitive to these inhibitors. Our results show that the phosphorylation and dephosphorylation of neighboring GPCR kinase sites in the sst2A receptor are subject to differential spatial and temporal regulation. Thus, the pattern of receptor phosphorylation is determined by the duration of agonist stimulation and compartment-specific enzymatic activity.
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Affiliation(s)
- Madhumita Ghosh
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas 77225, USA
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145
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Abstract
Label-free biosensors offer integrated, kinetic and multi-parametric measures of receptor biology and ligand pharmacology in whole cells. Being highly sensitive and pathway-unbiased, label-free receptor assays can be used to probe the systems cell biology including pleiotropic signaling of receptors, and to characterize the functional selectivity and phenotypic pharmacology of ligand molecules. These assays provide a new dimension for elucidating receptor biology and for facilitating drug discovery.
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Affiliation(s)
- Ye Fang
- Biochemical Technologies, Science and Technology Division, Corning Inc., Sullivan Park, Corning, NY 14831, Tele: 607-9747203, Fax: 919-9745957
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146
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Abstract
Phosphorylation of G protein-coupled receptors (GPCRs) is one of the most prominent post-translation modifications mediated by agonist stimulation. This process has been shown to result not only in receptor desensitisation but also, via the recruitment of arrestin adaptor proteins, to promote receptor coupling to numerous signalling pathways. Furthermore, there is now a growing body of evidence suggesting that GPCRs may employ phosphorylation as a mechanism to regulate their cell-type-specific signalling, hence generating tissue-specific functions. These advances have resulted partly from improved methods used in the determination of phospho-acceptor sites on GPCRs and improved analysis of the consequences of phosphorylation. This chapter aims to describe the methods used in our laboratory for the investigation of site-specific phosphorylation of the M₃-muscarinic receptor. These methods could easily be applied in the study of other receptors.
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Affiliation(s)
- Adrian J Butcher
- Department of Cell Physiology and Pharmacology and the Protein and Nucleic Acid Chemistry Laboratory, University of Leicester, Leicester, UK
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147
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Butcher AJ, Prihandoko R, Kong KC, McWilliams P, Edwards JM, Bottrill A, Mistry S, Tobin AB. Differential G-protein-coupled receptor phosphorylation provides evidence for a signaling bar code. J Biol Chem 2010; 286:11506-18. [PMID: 21177246 PMCID: PMC3064205 DOI: 10.1074/jbc.m110.154526] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
G-protein-coupled receptors are hyper-phosphorylated in a process that controls receptor coupling to downstream signaling pathways. The pattern of receptor phosphorylation has been proposed to generate a “bar code” that can be varied in a tissue-specific manner to direct physiologically relevant receptor signaling. If such a mechanism existed, receptors would be expected to be phosphorylated in a cell/tissue-specific manner. Using tryptic phosphopeptide maps, mass spectrometry, and phospho-specific antibodies, it was determined here that the prototypical Gq/11-coupled M3-muscarinic receptor was indeed differentially phosphorylated in various cell and tissue types supporting a role for differential receptor phosphorylation in directing tissue-specific signaling. Furthermore, the phosphorylation profile of the M3-muscarinic receptor was also dependent on the stimulus. Full and partial agonists to the M3-muscarinic receptor were observed to direct phosphorylation preferentially to specific sites. This hitherto unappreciated property of ligands raises the possibility that one mechanism underlying ligand bias/functional selectivity, a process where ligands direct receptors to preferred signaling pathways, may be centered on the capacity of ligands to promote receptor phosphorylation at specific sites.
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Affiliation(s)
- Adrian J Butcher
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
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148
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Zimmerman B, Simaan M, Akoume MY, Houri N, Chevallier S, Séguéla P, Laporte SA. Role of ßarrestins in bradykinin B2 receptor-mediated signalling. Cell Signal 2010; 23:648-59. [PMID: 21145390 DOI: 10.1016/j.cellsig.2010.11.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 11/22/2010] [Accepted: 11/25/2010] [Indexed: 10/18/2022]
Abstract
G protein-coupled receptors (GPCRs) can engage multiple pathways to activate ERK1/2 via both G proteins and/or ßarrestin. Receptor recruitment of ßarrestin is also important for GPCR desensitization, internalization and resensitization. Modulation of the receptor/ßarrestin interaction through modification of either component would presumably alter the output generated by receptor activation. Here we examined how ßarrestins regulate bradykinin (BK) B2 receptor (B2R) signalling and desensitization by either truncating ßarrestin1 or ßarrestin2 or by alanine substitution of a serine/threonine cluster in the C-terminal tail of B2R (B2R-4A), conditions which all affect the avidity of the B2R/ßarrestin complex. We first demonstrate that BK-mediated ERK1/2 activation is biphasic containing an early peak (between 2-5min) followed by sustained activation for at least 60min. The early but not the sustained phase was predictably affected by inhibition of either Gαq/11 or Gαi/o, whereas loss of ßarrestin2 but not ßarrestin1 resulted in diminished prolonged ERK1/2 activation. ßarrestin2's role was further examined using a truncation mutant with augmented avidity for the agonist-occupied receptor, revealing an increase in both immediate and extended ERK1/2 signalling. We also show that ERK1/2 is recruited to the B2R/ßarrestin complex on endosomes as well as the plasma membrane. Moreover, we investigated ßarrestin's role using the B2R-4A, which is deficient in ßarrestin binding and does not internalize. We show that ERK1/2 signalling downstream of the receptor is entirely G protein-dependent and receptor-mediated intracellular calcium mobilization studies revealed a lack of desensitization. Functionally, the lack of desensitization resulted in increased cell growth and migration compared to the wild-type receptor, which was sensitive to MEK inhibition. These results highlight ßarrestin's crucial role in the maintenance of proper B2R signalling.
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Affiliation(s)
- Brandon Zimmerman
- McGill University Health Center Research Institute, Department of Medicine, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec, Canada
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149
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Abstract
This themed section of BJP includes 11 reviews on the biology of G-protein coupled receptors (GPCRs) and the drug targets that these present, 21 research papers on the pharmacology of a range of GPCRs and Commentaries on four of the papers. Areas reviewed include molecular interactions, particular in respect of hetero-dimerisation between receptors and other membrane-located proteins and other key signalling molecules including cAMP and G12/13 proteins and recently de-orphanised receptors including the Neuromedins U & S and the Free Fatty Acid receptors FFA2 & FFA3. The research papers cover the pharmacology of a range of agents acting at GPCRs, including adrenoceptors, purinoceptors, 5HT, opioid, cannabinoid & PAR-2 receptors. A group of papers is concerned with the interesting and rapidly developing pharmacology of drugs acting at beta(2)-adrenoceptors. The reach of GPCRs is illustrated by the range of physiological systems and therapeutic applications involved, including pain, cancer, cardiovascular, gastrointestinal, visual and respiratory and central nervous systems.
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150
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Burns RN, Moniri NH. Agonism with the omega-3 fatty acids alpha-linolenic acid and docosahexaenoic acid mediates phosphorylation of both the short and long isoforms of the human GPR120 receptor. Biochem Biophys Res Commun 2010; 396:1030-5. [PMID: 20471368 DOI: 10.1016/j.bbrc.2010.05.057] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 05/10/2010] [Indexed: 10/19/2022]
Abstract
The newly discovered G protein-coupled receptor GPR120 has recently been shown to stimulate secretion of the gut hormones glucagon-like peptide-1 and cholecystokinin upon binding of free fatty acids, thrusting it to the forefront of drug discovery efforts for treatment of type 2 diabetes as well as satiety and obesity. Although sequences for two alternative splice variants of the human GPR120 receptor have been reported, there have been no studies which directly compare the signaling of these isoforms. We have identified an additional 16 amino acid gap containing four phospho-labile serine/threonine residues which is localized to the third intracellular loop of the GPR120-long (GPR120-L) isoform. Based on this finding, we hypothesized that the agonist-stimulated phosphorylation profiles of this isoform would be distinct from that of the short isoform (GPR120-S). Using a clonal HEK293 cell model, we examined agonist-mediated phosphorylation of GPR120-S and GPR120-L with the omega-3 fatty acids alpha-linolenic acid (ALA) and docosahexaenoic acid (DHA). Our results show rapid phosphorylation of both isoforms following agonism by either ALA or DHA. Moreover, we show no significant difference in the degree or rate of phosphorylation of both isoforms upon agonism with either ALA or DHA, suggesting that the additional gap in the longer variant is not phosphorylated. Importantly, our results demonstrate that the shorter variant exhibits significantly more pronounced basal phosphorylation in the absence of agonist, suggesting that the additional gap in the long variant may contribute to masking of constitutive phosphorylation sites. These are the first results which demonstrate specific phosphorylation of GPR120 isoforms upon agonism by free fatty acids and the first which distinguish the phosphorylation profiles of the two GPR120 isoforms.
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Affiliation(s)
- Rebecca N Burns
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Mercer University, Atlanta, GA 30341, USA
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