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Maslov I, Volkov O, Khorn P, Orekhov P, Gusach A, Kuzmichev P, Gerasimov A, Luginina A, Coucke Q, Bogorodskiy A, Gordeliy V, Wanninger S, Barth A, Mishin A, Hofkens J, Cherezov V, Gensch T, Hendrix J, Borshchevskiy V. Sub-millisecond conformational dynamics of the A 2A adenosine receptor revealed by single-molecule FRET. Commun Biol 2023; 6:362. [PMID: 37012383 PMCID: PMC10070357 DOI: 10.1038/s42003-023-04727-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 03/17/2023] [Indexed: 04/05/2023] Open
Abstract
The complex pharmacology of G-protein-coupled receptors (GPCRs) is defined by their multi-state conformational dynamics. Single-molecule Förster Resonance Energy Transfer (smFRET) is well suited to quantify dynamics for individual protein molecules; however, its application to GPCRs is challenging. Therefore, smFRET has been limited to studies of inter-receptor interactions in cellular membranes and receptors in detergent environments. Here, we performed smFRET experiments on functionally active human A2A adenosine receptor (A2AAR) molecules embedded in freely diffusing lipid nanodiscs to study their intramolecular conformational dynamics. We propose a dynamic model of A2AAR activation that involves a slow (>2 ms) exchange between the active-like and inactive-like conformations in both apo and antagonist-bound A2AAR, explaining the receptor's constitutive activity. For the agonist-bound A2AAR, we detected faster (390 ± 80 µs) ligand efficacy-dependent dynamics. Our work establishes a general smFRET platform for GPCR investigations that can potentially be used for drug screening and/or mechanism-of-action studies.
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Affiliation(s)
- Ivan Maslov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
- Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), Hasselt University, Diepenbeek, Belgium
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Leuven, Belgium
| | | | - Polina Khorn
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - Philipp Orekhov
- Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, China
| | - Anastasiia Gusach
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Pavel Kuzmichev
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - Andrey Gerasimov
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
- Vyatka State University, Kirov, Russia
| | - Aleksandra Luginina
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - Quinten Coucke
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Andrey Bogorodskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - Valentin Gordeliy
- Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-CEA-CNRS, Grenoble, France
| | - Simon Wanninger
- Physical Chemistry, Department of Chemistry, Center for Nano Science (CENS), Center for Integrated Protein Science (CIPSM) and Nanosystems Initiative München (NIM), Ludwig-Maximilians-Universität Munich, Munich, Germany
| | - Anders Barth
- Physical Chemistry, Department of Chemistry, Center for Nano Science (CENS), Center for Integrated Protein Science (CIPSM) and Nanosystems Initiative München (NIM), Ludwig-Maximilians-Universität Munich, Munich, Germany
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, HZ, Delft, The Netherlands
| | - Alexey Mishin
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - Johan Hofkens
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Leuven, Belgium
- Max Plank Institute for Polymer Research, Mainz, Germany
| | - Vadim Cherezov
- Bridge Institute, Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Thomas Gensch
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Jelle Hendrix
- Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), Hasselt University, Diepenbeek, Belgium.
- Laboratory for Photochemistry and Spectroscopy, Division for Molecular Imaging and Photonics, Department of Chemistry, KU Leuven, Leuven, Belgium.
| | - Valentin Borshchevskiy
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia.
- Joint Institute for Nuclear Research, Dubna, Russian Federation.
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2
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Engineered Allosteric Regulation of Protein Function. J Mol Biol 2022; 434:167620. [PMID: 35513109 DOI: 10.1016/j.jmb.2022.167620] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/27/2022] [Accepted: 04/26/2022] [Indexed: 11/20/2022]
Abstract
Allosteric regulation of proteins has been utilized to study various aspects of cell signaling, from unicellular events to organism-wide phenotypes. However, traditional methods of allosteric regulation, such as constitutively active mutants and inhibitors, lack tight spatiotemporal control. This often leads to unintended signaling consequences that interfere with data interpretation. To overcome these obstacles, researchers employed protein engineering approaches that enable tight control of protein function through allosteric mechanisms. These methods provide high specificity as well as spatial and temporal precision in regulation of protein activity in vitro and in vivo. In this review, we focus on the recent advancements in engineered allosteric regulation and discuss the various bioengineered allosteric techniques available now, from chimeric GPCRs to chemogenetic and optogenetic switches. We highlight the benefits and pitfalls of each of these techniques as well as areas in which future improvements can be made. Additionally, we provide a brief discussion on implementation of engineered allosteric regulation approaches, demonstrating that these tools can shed light on elusive biological events and have the potential to be utilized in precision medicine.
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3
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Bhanot S, Hemminger G, Martin CL, Aller SG, Forrest JN. A nonolfactory shark adenosine receptor activates CFTR with unique pharmacology and structural features. Am J Physiol Cell Physiol 2021; 320:C892-C901. [PMID: 33689481 DOI: 10.1152/ajpcell.00481.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine receptors (ADORs) are G protein-coupled purinoceptors that have several functions including regulation of chloride secretion via cystic fibrosis transmembrane conductance regulator (CFTR) in human airway and kidney. We cloned an ADOR from Squalus acanthias (shark) that likely regulates CFTR in the rectal gland. Phylogenic and expression analyses indicate that elasmobranch ADORs are nonolfactory and appear to represent extant predecessors of mammalian ADORs. We therefore designate the shark ADOR as the A0 receptor. We coexpressed A0 with CFTR in Xenopus laevis oocytes and characterized the coupling of A0 to the chloride channel. Two-electrode voltage clamping was performed, and current-voltage (I-V) responses were recorded to monitor CFTR status. Only in A0- and CFTR-coinjected oocytes did adenosine analogs produce a significant concentration-dependent activation of CFTR consistent with its electrophysiological signature. A pharmacological profile for A0 was obtained for ADOR agonists and antagonists that differed markedly from all mammalian ADOR subtypes [agonists: R-phenyl-isopropyl adenosine (R-PIA) > S-phenyl-isopropyl adenosine (S-PIA) > CGS21680 > N6-cyclopentyladenosine (CPA) > 2-chloroadenosine (2ClAdo) > CV1808 = N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine (DPMA) > N-ethyl-carboxyl adenosine (NECA); and antagonists: 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) > PD115199 > 1,3-dimethyl-8-phenylxanthine (8PT) > CGS15943]. Structures of human ADORs permitted a high-confidence homology model of the shark A0 core that revealed unique structural features of ancestral receptors. We conclude that 1) A0 is a novel and unique adenosine receptor ancestor by functional and structural criteria; 2) A0 likely activates CFTR in vivo, and this receptor activates CFTR in oocytes, indicating an evolutionary coupling between ADORs and chloride secretion; and 3) A0 appears to be a nonolfactory evolutionary ancestor of all four mammalian ADOR subtypes.
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Affiliation(s)
- Sumeet Bhanot
- Renal Section, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut.,The Mount Desert Island Biological Laboratory, Salisbury Cove, Maine
| | - Gabriele Hemminger
- Renal Section, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut.,The Mount Desert Island Biological Laboratory, Salisbury Cove, Maine
| | - Cole L Martin
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Stephen G Aller
- Renal Section, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut.,The Mount Desert Island Biological Laboratory, Salisbury Cove, Maine.,Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama
| | - John N Forrest
- Renal Section, Department of Medicine, Yale University School of Medicine, New Haven, Connecticut.,The Mount Desert Island Biological Laboratory, Salisbury Cove, Maine
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4
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Hariharan A, Weir N, Robertson C, He L, Betsholtz C, Longden TA. The Ion Channel and GPCR Toolkit of Brain Capillary Pericytes. Front Cell Neurosci 2020; 14:601324. [PMID: 33390906 PMCID: PMC7775489 DOI: 10.3389/fncel.2020.601324] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 11/13/2020] [Indexed: 12/14/2022] Open
Abstract
Brain pericytes reside on the abluminal surface of capillaries, and their processes cover ~90% of the length of the capillary bed. These cells were first described almost 150 years ago (Eberth, 1871; Rouget, 1873) and have been the subject of intense experimental scrutiny in recent years, but their physiological roles remain uncertain and little is known of the complement of signaling elements that they employ to carry out their functions. In this review, we synthesize functional data with single-cell RNAseq screens to explore the ion channel and G protein-coupled receptor (GPCR) toolkit of mesh and thin-strand pericytes of the brain, with the aim of providing a framework for deeper explorations of the molecular mechanisms that govern pericyte physiology. We argue that their complement of channels and receptors ideally positions capillary pericytes to play a central role in adapting blood flow to meet the challenge of satisfying neuronal energy requirements from deep within the capillary bed, by enabling dynamic regulation of their membrane potential to influence the electrical output of the cell. In particular, we outline how genetic and functional evidence suggest an important role for Gs-coupled GPCRs and ATP-sensitive potassium (KATP) channels in this context. We put forth a predictive model for long-range hyperpolarizing electrical signaling from pericytes to upstream arterioles, and detail the TRP and Ca2+ channels and Gq, Gi/o, and G12/13 signaling processes that counterbalance this. We underscore critical questions that need to be addressed to further advance our understanding of the signaling topology of capillary pericytes, and how this contributes to their physiological roles and their dysfunction in disease.
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Affiliation(s)
- Ashwini Hariharan
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Nick Weir
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Colin Robertson
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Liqun He
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Christer Betsholtz
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.,Department of Medicine Huddinge (MedH), Karolinska Institutet & Integrated Cardio Metabolic Centre, Huddinge, Sweden
| | - Thomas A Longden
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, United States
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5
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Silva D, Moreira D, Cordeiro-da-Silva A, Quintas C, Gonçalves J, Fresco P. Intracellular adenosine released from THP-1 differentiated human macrophages is involved in an autocrine control of Leishmania parasitic burden, mediated by adenosine A 2A and A 2B receptors. Eur J Pharmacol 2020; 885:173504. [PMID: 32858046 DOI: 10.1016/j.ejphar.2020.173504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 08/20/2020] [Accepted: 08/23/2020] [Indexed: 12/22/2022]
Abstract
Leishmania infected macrophages have conditions to produce adenosine. Despite its known immunosuppressive effects, no studies have yet established whether adenosine alter Leishmania parasitic burden upon macrophage infection. This work aimed at investigating whether endogenous adenosine exerts an autocrine modulation of macrophage response towards Leishmania infection, identifying its origin and potential pharmacological targets for visceral leishmaniasis (VL), using THP-1 differentiated macrophages. Adenosine deaminase treatment of infected THP-1 cells reduced the parasitic burden (29.1 ± 2.2%, P < 0.05). Adenosine A2A and A2B receptor subtypes expression was confirmed by RT-qPCR and by immunocytochemistry and their blockade with selective adenosine A2A and A2B antagonists reduced the parasitic burden [14.5 ± 3.1% (P < 0.05) and 12.3 ± 3.1% (P < 0.05), respectively; and 24.9 ± 2.8% (P < 0.05), by the combination of the two antagonists)], suggesting that adenosine A2 receptors are tonically activated in infected THP-1 differentiated macrophages. The tonic activation of adenosine A2 receptors was dependent on the release of intracellular adenosine through equilibrative nucleoside transporters (ENT1/ENT2): NBTI or dipyridamole reduced (~25%) whereas, when ENTs were blocked, adenosine A2 receptor antagonists failed to reduce and A2 agonists increase parasitic burden. Effects of adenosine A2 receptors antagonists and ENT1/2 inhibitor were prevented by L-NAME, indicating that nitric oxide production inhibition prevents adenosine from increasing parasitic burden. Results suggest that intracellular adenosine, released through ENTs, elicits an autocrine increase in parasitic burden in THP-1 macrophages, through adenosine A2 receptors activation. These observations open the possibility to use well-established ENT inhibitors or adenosine A2 receptor antagonists as new therapeutic approaches in VL.
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Affiliation(s)
- Dany Silva
- Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.
| | - Diana Moreira
- Parasite Disease Group, Institute of Molecular and Cellular Biology, Institute for Research and Innovation in Health Sciences, University of Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal; Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.
| | - Anabela Cordeiro-da-Silva
- Parasite Disease Group, Institute of Molecular and Cellular Biology, Institute for Research and Innovation in Health Sciences, University of Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal; Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.
| | - Clara Quintas
- Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.
| | - Jorge Gonçalves
- Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal; Epithelial Interactions in Cancer, Institute of Molecular Pathology and Immunology, Institute for Research and Innovation in Health Sciences, University of Porto, Rua Alfredo Allen 208, 4200-135, Porto, Portugal.
| | - Paula Fresco
- Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313, Porto, Portugal.
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6
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Thibeault PE, Ramachandran R. Biased signaling in platelet G-protein coupled receptors. Can J Physiol Pharmacol 2020; 99:255-269. [PMID: 32846106 DOI: 10.1139/cjpp-2020-0149] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Platelets are small megakaryocyte-derived, anucleate, disk-like structures that play an outsized role in human health and disease. Both a decrease in the number of platelets and a variety of platelet function disorders result in petechiae or bleeding that can be life threatening. Conversely, the inappropriate activation of platelets, within diseased blood vessels, remains the leading cause of death and morbidity by affecting heart attacks and stroke. The fine balance of the platelet state in healthy individuals is controlled by a number of receptor-mediated signaling pathways that allow the platelet to rapidly respond and maintain haemostasis. G-protein coupled receptors (GPCRs) are particularly important regulators of platelet function. Here we focus on the major platelet-expressed GPCRs and discuss the roles of downstream signaling pathways (e.g., different G-protein subtypes or β-arrestin) in regulating the different phases of the platelet activation. Further, we consider the potential for selectively targeting signaling pathways that may contribute to platelet responses in disease through development of biased agonists. Such selective targeting of GPCR-mediated signaling pathways by drugs, often referred to as biased signaling, holds promise in delivering therapeutic interventions that do not present significant side effects, especially in finely balanced physiological systems such as platelet activation in haemostasis.
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Affiliation(s)
- Pierre E Thibeault
- Department of Physiology and Pharmacology, University of Western Ontario, 1151 Richmond Street, London, ON N6A5C1, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, 1151 Richmond Street, London, ON N6A5C1, Canada
| | - Rithwik Ramachandran
- Department of Physiology and Pharmacology, University of Western Ontario, 1151 Richmond Street, London, ON N6A5C1, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, 1151 Richmond Street, London, ON N6A5C1, Canada
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7
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Jamwal S, Mittal A, Kumar P, Alhayani DM, Al-Aboudi A. Therapeutic Potential of Agonists and Antagonists of A1, A2a, A2b and A3 Adenosine Receptors. Curr Pharm Des 2020; 25:2892-2905. [PMID: 31333104 DOI: 10.2174/1381612825666190716112319] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Accepted: 07/04/2019] [Indexed: 02/04/2023]
Abstract
Adenosine is a naturally occurring nucleoside and an essential component of the energy production and utilization systems of the body. Adenosine is formed by the degradation of adenosine-triphosphate (ATP) during energy-consuming processes. Adenosine regulates numerous physiological processes through activation of four subtypes of G-protein coupled membrane receptors viz. A1, A2A, A2B and A3. Its physiological importance depends on the affinity of these receptors and the extracellular concentrations reached. ATP acts as a neurotransmitter in both peripheral and central nervous systems. In the peripheral nervous system, ATP is involved in chemical transmission in sensory and autonomic ganglia, whereas in central nervous system, ATP, released from synaptic terminals, induces fast excitatory postsynaptic currents. ATP provides the energetics for all muscle movements, heart beats, nerve signals and chemical reactions inside the body. Adenosine has been traditionally considered an inhibitor of neuronal activity and a regulator of cerebral blood flow. Since adenosine is neuroprotective against excitotoxic and metabolic dysfunctions observed in neurological and ocular diseases, the search for adenosinerelated drugs regulating adenosine transporters and receptors can be important for advancement of therapeutic strategies against these diseases. This review will summarize the therapeutic potential and recent SAR and pharmacology of adenosine and its receptor agonists and antagonists.
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Affiliation(s)
- Sumit Jamwal
- School of Pharmacy and Emerging Sciences, Baddi University of Emerging Sciences and Technologies, Baddi, India
| | - Ashish Mittal
- Department of Pharmaceutical Sciences, M.R.S. Punjab Technical University, Bathinda, Punjab, India
| | - Puneet Kumar
- Department of Pharmaceutical Sciences, M.R.S. Punjab Technical University, Bathinda, Punjab, India
| | - Dana M Alhayani
- Faculty of Pharmacy, Philadelphia University, PO Box - 1, 19392, Amman, Jordan
| | - Amal Al-Aboudi
- Faculty of Science, The University of Jordan, Amman, 11942, Jordan
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8
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Guan Z, Makled MN, Inscho EW. Purinoceptors, renal microvascular function and hypertension. Physiol Res 2020; 69:353-369. [PMID: 32301620 DOI: 10.33549/physiolres.934463] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Proper renal blood flow (RBF) and glomerular filtration rate (GFR) are critical for maintaining normal blood pressure, kidney function and water and electrolyte homeostasis. The renal microvasculature expresses a multitude of receptors mediating vasodilation and vasoconstriction, which can influence glomerular blood flow and capillary pressure. Despite this, RBF and GFR remain quite stable when arterial pressure fluctuates because of the autoregulatory mechanism. ATP and adenosine participate in autoregulatory control of RBF and GFR via activation of two different purinoceptor families (P1 and P2). Purinoceptors are widely expressed in renal microvasculature and tubules. Emerging data show altered purinoceptor signaling in hypertension-associated kidney injury, diabetic nephropathy, sepsis, ischemia-reperfusion induced acute kidney injury and polycystic kidney disease. In this brief review, we highlight recent studies and new insights on purinoceptors regulating renal microvascular function and renal hemodynamics. We also address the mechanisms underlying renal microvascular injury and impaired renal autoregulation, focusing on purinoceptor signaling and hypertension-induced renal microvascular dysfunction. Interested readers are directed to several excellent and comprehensive reviews that recently covered the topics of renal autoregulation, and nucleotides in kidney function under physiological and pathophysiological conditions (Inscho 2009, Navar et al. 2008, Carlstrom et al. 2015, Vallon et al. 2020).
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Affiliation(s)
- Z Guan
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, South Birmingham, USA.
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9
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Coronary Physiology Beyond Coronary Flow Reserve in Microvascular Angina. J Am Coll Cardiol 2018; 72:2642-2662. [DOI: 10.1016/j.jacc.2018.07.106] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 07/30/2018] [Indexed: 11/18/2022]
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10
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Jain AR, Stradley SH, Robinson AS. The A2aR C-terminus provides improved total and active expression yields for adenosine receptor chimeras. AIChE J 2018. [DOI: 10.1002/aic.16398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Abhinav R. Jain
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Steven H. Stradley
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
| | - Anne S. Robinson
- Dept. of Chemical and Biomolecular Engineering; Tulane University; New Orleans LA 70118
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11
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Ogawa Y, Furusawa E, Saitoh T, Sugimoto H, Omori T, Shimizu S, Kondo H, Yamazaki M, Sakuraba H, Oishi K. Inhibition of astrocytic adenosine receptor A 2A attenuates microglial activation in a mouse model of Sandhoff disease. Neurobiol Dis 2018; 118:142-154. [DOI: 10.1016/j.nbd.2018.07.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 07/02/2018] [Accepted: 07/15/2018] [Indexed: 12/18/2022] Open
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12
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Beach KM, Hung LF, Arumugam B, Smith EL, Ostrin LA. Adenosine receptor distribution in Rhesus monkey ocular tissue. Exp Eye Res 2018; 174:40-50. [PMID: 29792846 DOI: 10.1016/j.exer.2018.05.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 04/26/2018] [Accepted: 05/20/2018] [Indexed: 02/06/2023]
Abstract
Adenosine receptor (ADOR) antagonists, such as 7-methylxanthine (7-MX), have been shown to slow myopia progression in humans and animal models. Adenosine receptors are found throughout the body, and regulate the release of neurotransmitters such as dopamine and glutamate. However, the role of adenosine in eye growth is unclear. Evidence suggests that 7-MX increases scleral collagen fibril diameter, hence preventing axial elongation. This study used immunohistochemistry (IHC) and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) to examine the distribution of the four ADORs in the normal monkey eye to help elucidate potential mechanisms of action. Eyes were enucleated from six Rhesus monkeys. Anterior segments and eyecups were separated into components and flash-frozen for RNA extraction or fixed in 4% paraformaldehyde and processed for immunohistochemistry against ADORA1, ADORA2a, ADORA2b, and ADORA3. RNA was reverse-transcribed, and qPCR was performed using custom primers. Relative gene expression was calculated using the ΔΔCt method normalizing to liver expression, and statistical analysis was performed using Relative Expression Software Tool. ADORA1 immunostaining was highest in the iris sphincter muscle, trabecular meshwork, ciliary epithelium, and retinal nerve fiber layer. ADORA2a immunostaining was highest in the corneal epithelium, trabecular meshwork, ciliary epithelium, retinal nerve fiber layer, and scleral fibroblasts. ADORA2b immunostaining was highest in corneal basal epithelium, limbal stem cells, iris sphincter, ciliary muscle, ciliary epithelium, choroid, isolated retinal ganglion cells and scattered scleral fibroblasts. ADORA3 immunostaining was highest in the iris sphincter, ciliary muscle, ciliary epithelium, choroid, isolated retinal ganglion cells, and scleral fibroblasts. Compared to liver mRNA, ADORA1 mRNA was significantly higher in the brain, retina and choroid, and significantly lower in the iris/ciliary body. ADORA2a expression was higher in brain and retina, ADORA2b expression was higher in retina, and ADORA3 was higher in the choroid. In conclusion, immunohistochemistry and RT-qPCR indicated differential patterns of expression of the four adenosine receptors in the ocular tissues of the normal non-human primate. The presence of ADORs in scleral fibroblasts and the choroid may support mechanisms by which ADOR antagonists prevent myopia. The potential effects of ADOR inhibition on both anterior and posterior ocular structures warrant investigation.
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Affiliation(s)
- Krista M Beach
- University of Houston College of Optometry, 4901 Calhoun Rd, Houston, TX 77204, USA
| | - Li-Fang Hung
- University of Houston College of Optometry, 4901 Calhoun Rd, Houston, TX 77204, USA
| | - Baskar Arumugam
- University of Houston College of Optometry, 4901 Calhoun Rd, Houston, TX 77204, USA
| | - Earl L Smith
- University of Houston College of Optometry, 4901 Calhoun Rd, Houston, TX 77204, USA
| | - Lisa A Ostrin
- University of Houston College of Optometry, 4901 Calhoun Rd, Houston, TX 77204, USA.
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Welihinda AA, Kaur M, Raveendran KS, Amento EP. Enhancement of inosine-mediated A 2AR signaling through positive allosteric modulation. Cell Signal 2017; 42:227-235. [PMID: 29126977 DOI: 10.1016/j.cellsig.2017.11.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/20/2017] [Accepted: 11/06/2017] [Indexed: 12/14/2022]
Abstract
Inosine is an endogenous nucleoside that is produced by metabolic deamination of adenosine. Inosine is metabolically more stable (half-life 15h) than adenosine (half-life <10s). Inosine exerts anti-inflammatory and immunomodulatory effects similar to those observed with adenosine. These effects are mediated in part through the adenosine A2A receptor (A2AR). Relative to adenosine inosine exhibits a lower affinity towards the A2AR. Therefore, it is generally believed that inosine is incapable of activating the A2AR through direct engagement, but indirectly activates the A2AR upon metabolic conversion to higher affinity adenosine. A handful of studies, however, have provided evidence for direct inosine engagement at the A2AR leading to activation of downstream signaling events and inhibition of cytokine production. Here, we demonstrate that under conditions devoid of adenosine, inosine as well as an analog of inosine 6-S-[(4-Nitrophenyl)methyl]-6-thioinosine selectively and dose-dependently activated A2AR-mediated cAMP production and ERK1/2 phosphorylation in CHO cells stably expressing the human A2AR. Inosine also inhibited LPS-stimulated TNF-α, CCL3 and CCL4 production by splenic monocytes in an A2AR-dependent manner. In addition, we demonstrate that a positive allosteric modulator (PAM) of the A2AR enhanced inosine-mediated cAMP production, ERK1/2 phosphorylation and inhibition of pro-inflammatory cytokine and chemokine production. The cumulative effects of allosteric enhancement of adenosine-mediated and inosine-mediated A2AR activation may be the basis for the sustained anti-inflammatory and immunomodulatory effects observed in vivo and thereby provide insights into potential therapeutic interventions for inflammation- and immune-mediated diseases.
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Affiliation(s)
- Ajith A Welihinda
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085.
| | - Manmeet Kaur
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
| | - Kaviya S Raveendran
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
| | - Edward P Amento
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085
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The Adenosinergic System as a Therapeutic Target in the Vasculature: New Ligands and Challenges. Molecules 2017; 22:molecules22050752. [PMID: 28481238 PMCID: PMC6154114 DOI: 10.3390/molecules22050752] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 04/24/2017] [Accepted: 05/02/2017] [Indexed: 12/20/2022] Open
Abstract
Adenosine is an adenine base purine with actions as a modulator of neurotransmission, smooth muscle contraction, and immune response in several systems of the human body, including the cardiovascular system. In the vasculature, four P1-receptors or adenosine receptors—A1, A2A, A2B and A3—have been identified. Adenosine receptors are membrane G-protein receptors that trigger their actions through several signaling pathways and present differential affinity requirements. Adenosine is an endogenous ligand whose extracellular levels can reach concentrations high enough to activate the adenosine receptors. This nucleoside is a product of enzymatic breakdown of extra and intracellular adenine nucleotides and also of S-adenosylhomocysteine. Adenosine availability is also dependent on the activity of nucleoside transporters (NTs). The interplay between NTs and adenosine receptors’ activities are debated and a particular attention is given to the paramount importance of the disruption of this interplay in vascular pathophysiology, namely in hypertension., The integration of important functional aspects of individual adenosine receptor pharmacology (such as in vasoconstriction/vasodilation) and morphological features (within the three vascular layers) in vessels will be discussed, hopefully clarifying the importance of adenosine receptors/NTs for modulating peripheral mesenteric vascular resistance. In recent years, an increase interest in purine physiology/pharmacology has led to the development of new ligands for adenosine receptors. Some of them have been patented as having promising therapeutic activities and some have been chosen to undergo on clinical trials. Increased levels of endogenous adenosine near a specific subtype can lead to its activation, constituting an indirect receptor targeting approach either by inhibition of NT or, alternatively, by increasing the activity of enzymes responsible for ATP breakdown. These findings highlight the putative role of adenosinergic players as attractive therapeutic targets for cardiovascular pathologies, namely hypertension, heart failure or stroke. Nevertheless, several aspects are still to be explored, creating new challenges to be addressed in future studies, particularly the development of strategies able to circumvent the predicted side effects of these therapies.
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15
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Cunha RA. How does adenosine control neuronal dysfunction and neurodegeneration? J Neurochem 2016; 139:1019-1055. [PMID: 27365148 DOI: 10.1111/jnc.13724] [Citation(s) in RCA: 320] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/23/2016] [Accepted: 06/23/2016] [Indexed: 12/11/2022]
Abstract
The adenosine modulation system mostly operates through inhibitory A1 (A1 R) and facilitatory A2A receptors (A2A R) in the brain. The activity-dependent release of adenosine acts as a brake of excitatory transmission through A1 R, which are enriched in glutamatergic terminals. Adenosine sharpens salience of information encoding in neuronal circuits: high-frequency stimulation triggers ATP release in the 'activated' synapse, which is locally converted by ecto-nucleotidases into adenosine to selectively activate A2A R; A2A R switch off A1 R and CB1 receptors, bolster glutamate release and NMDA receptors to assist increasing synaptic plasticity in the 'activated' synapse; the parallel engagement of the astrocytic syncytium releases adenosine further inhibiting neighboring synapses, thus sharpening the encoded plastic change. Brain insults trigger a large outflow of adenosine and ATP, as a danger signal. A1 R are a hurdle for damage initiation, but they desensitize upon prolonged activation. However, if the insult is near-threshold and/or of short-duration, A1 R trigger preconditioning, which may limit the spread of damage. Brain insults also up-regulate A2A R, probably to bolster adaptive changes, but this heightens brain damage since A2A R blockade affords neuroprotection in models of epilepsy, depression, Alzheimer's, or Parkinson's disease. This initially involves a control of synaptotoxicity by neuronal A2A R, whereas astrocytic and microglia A2A R might control the spread of damage. The A2A R signaling mechanisms are largely unknown since A2A R are pleiotropic, coupling to different G proteins and non-canonical pathways to control the viability of glutamatergic synapses, neuroinflammation, mitochondria function, and cytoskeleton dynamics. Thus, simultaneously bolstering A1 R preconditioning and preventing excessive A2A R function might afford maximal neuroprotection. The main physiological role of the adenosine modulation system is to sharp the salience of information encoding through a combined action of adenosine A2A receptors (A2A R) in the synapse undergoing an alteration of synaptic efficiency with an increased inhibitory action of A1 R in all surrounding synapses. Brain insults trigger an up-regulation of A2A R in an attempt to bolster adaptive plasticity together with adenosine release and A1 R desensitization; this favors synaptotocity (increased A2A R) and decreases the hurdle to undergo degeneration (decreased A1 R). Maximal neuroprotection is expected to result from a combined A2A R blockade and increased A1 R activation. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".
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Affiliation(s)
- Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,FMUC-Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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16
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Kumbhani DJ, de Lemos JA. Finding an effective treatment for microvascular obstruction in STEMI: a road to perdition? Eur Heart J 2016; 37:1920-2. [PMID: 27194779 DOI: 10.1093/eurheartj/ehw186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Dharam J Kumbhani
- Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - James A de Lemos
- Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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17
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Hamidzadeh K, Mosser DM. Purinergic Signaling to Terminate TLR Responses in Macrophages. Front Immunol 2016; 7:74. [PMID: 26973651 PMCID: PMC4773587 DOI: 10.3389/fimmu.2016.00074] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 02/15/2016] [Indexed: 12/20/2022] Open
Abstract
Macrophages undergo profound physiological alterations when they encounter pathogen-associated molecular patterns (PAMPs). These alterations can result in the elaboration of cytokines and mediators that promote immune responses and contribute to the clearance of pathogens. These innate immune responses by myeloid cells are transient. The termination of these secretory responses is not due to the dilution of stimuli, but rather to the active downregulation of innate responses induced by the very PAMPs that initiated them. Here, we describe a purinergic autoregulatory program whereby TLR-stimulated macrophages control their activation state. In this program, TLR-stimulated macrophages undergo metabolic alterations that result in the production of ATP and its release through membrane pannexin channels. This purine nucleotide is rapidly hydrolyzed to adenosine by ectoenzymes on the macrophage surface, CD39 and CD73. Adenosine then signals through the P1 class of seven transmembrane receptors to induce a regulatory state that is characterized by the downregulation of inflammatory cytokines and the production of anti-inflammatory cytokines and growth factors. This purinergic autoregulatory system mitigates the collateral damage that would be caused by the prolonged activation of macrophages and rather allows the macrophage to maintain homeostasis. The transient activation of macrophages can be prolonged by treating macrophages with IFN-γ. IFN-γ-treated macrophages become less sensitive to the regulatory effects of adenosine, allowing them to sustain macrophage activation for the duration of an adaptive immune response.
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Affiliation(s)
- Kajal Hamidzadeh
- Department of Cell Biology and Molecular Genetics, The Maryland Pathogen Research Institute, University of Maryland , College Park, MD , USA
| | - David M Mosser
- Department of Cell Biology and Molecular Genetics, The Maryland Pathogen Research Institute, University of Maryland , College Park, MD , USA
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18
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Orczyk JJ, Sethia R, Doster D, Garraghty PE. Transcriptome response to infraorbital nerve transection in the gonadally intact male rat barrel cortex: RNA-seq. J Comp Neurol 2016; 524:152-9. [PMID: 26109564 DOI: 10.1002/cne.23831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 06/12/2015] [Accepted: 06/16/2015] [Indexed: 11/11/2022]
Abstract
The effects of infraorbital nerve (ION) transection on gene expression in the adult male rat barrel cortex were investigated using RNA sequencing. After a 24-hour survival duration, 98 genes were differentially regulated by ION transection. Differentially expressed genes suggest changes in neuronal activity, excitability, and morphology. The production of mRNA for neurotrophins, including brain-derived neurotrophin factor (BNDF), was decreased following ION transection. Several potassium channels showed decreased mRNA production, whereas a sodium channel (Na(V)β4) associated with burst firing showed increased mRNA production. The results may have important implications for phantom-limb pain and complex regional pain syndrome. Future experiments should determine the extent to which changes in RNA result in changes in protein expression, in addition to utilizing laser capture microdissection techniques to differentiate between neuronal and glial cells.
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Affiliation(s)
- John J Orczyk
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, 47045
| | - Rishabh Sethia
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, 47045
| | - Dominique Doster
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, 47045
| | - Preston E Garraghty
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, 47045.,Program in Neuroscience, Indiana University, Bloomington, Indiana, 47045
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Molina CE, Llach A, Herraiz-Martínez A, Tarifa C, Barriga M, Wiegerinck RF, Fernandes J, Cabello N, Vallmitjana A, Benitéz R, Montiel J, Cinca J, Hove-Madsen L. Prevention of adenosine A2A receptor activation diminishes beat-to-beat alternation in human atrial myocytes. Basic Res Cardiol 2015; 111:5. [PMID: 26611209 DOI: 10.1007/s00395-015-0525-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 11/20/2015] [Indexed: 11/28/2022]
Abstract
Atrial fibrillation (AF) has been associated with increased spontaneous calcium release from the sarcoplasmic reticulum and linked to increased adenosine A2A receptor (A2AR) expression and activation. Here we tested whether this may favor atrial arrhythmogenesis by promoting beat-to-beat alternation and irregularity. Patch-clamp and confocal calcium imaging was used to measure the beat-to-beat response of the calcium current and transient in human atrial myocytes. Responses were classified as uniform, alternating or irregular and stimulation of Gs-protein coupled receptors decreased the frequency where a uniform response could be maintained from 1.0 ± 0.1 to 0.6 ± 0.1 Hz; p < 0.01 for beta-adrenergic receptors and from 1.4 ± 0.1 to 0.5 ± 0.1 Hz; p < 0.05 for A2ARs. The latter was linked to increased spontaneous calcium release and after-depolarizations. Moreover, A2AR activation increased the fraction of non-uniformly responding cells in HL-1 myocyte cultures from 19 ± 3 to 51 ± 9 %; p < 0.02, and electrical mapping in perfused porcine atria revealed that adenosine induced electrical alternans at longer cycle lengths, doubled the fraction of electrodes showing alternation, and increased the amplitude of alternations. Importantly, protein kinase A inhibition increased the highest frequency where uniform responses could be maintained from 0.84 ± 0.12 to 1.86 ± 0.11 Hz; p < 0.001 and prevention of A2AR-activation with exogenous adenosine deaminase selectively increased the threshold from 0.8 ± 0.1 to 1.2 ± 0.1 Hz; p = 0.001 in myocytes from patients with AF. In conclusion, A2AR-activation promotes beat-to-beat irregularities in the calcium transient in human atrial myocytes, and prevention of A2AR activation may be a novel means to maintain uniform beat-to-beat responses at higher beating frequencies in patients with atrial fibrillation.
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Affiliation(s)
- Cristina E Molina
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain
- Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, 45122, Essen, Germany
| | - Anna Llach
- Department of Cardiology and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Adela Herraiz-Martínez
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain
| | - Carmen Tarifa
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain
| | - Montserrat Barriga
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain
| | - Rob F Wiegerinck
- Department of Cardiology and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Jacqueline Fernandes
- Department of Cardiology and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Nuria Cabello
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain
| | - Alex Vallmitjana
- Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - Raúl Benitéz
- Department of Automatic Control, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - José Montiel
- Department of Cardiac Surgery and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Juan Cinca
- Department of Cardiology and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Leif Hove-Madsen
- Cardiac Rhythm and Contraction, Cardiovascular Research Centre CSIC-ICCC and IIB Sant Pau, Hospital de la Santa Creu i Sant Pau, St Antoni Mª Claret 167, 08025, Barcelona, Spain.
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20
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Welihinda AA, Amento EP. Positive allosteric modulation of the adenosine A2a receptor attenuates inflammation. JOURNAL OF INFLAMMATION-LONDON 2014; 11:37. [PMID: 25473378 PMCID: PMC4253011 DOI: 10.1186/s12950-014-0037-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 11/13/2014] [Indexed: 11/24/2022]
Abstract
Background Adenosine is produced at high levels at inflamed sites as a by-product of cellular activation and breakdown. Adenosine mediates its anti-inflammatory activity primarily through the adenosine A2a receptor (A2aR), a member of the G-protein coupled receptors. A2aR agonists have demonstrated anti-inflammatory efficacy, however, their therapeutic utility is hindered by a lack of adenosine receptor subtype selectivity upon systemic exposure. We sought to harness the anti-inflammatory effects of adenosine by enhancing the responsiveness of A2aR to endogenously produced adenosine through allosteric modulation. We have identified a family of positive allosteric modulators (PAMs) of the A2aR. Using one member of this PAM family, AEA061, we demonstrate that A2aRs are amenable to allosteric enhancement and such enhancement produces increased A2aR signaling and diminished inflammation in vivo. Methods A2aR activity was evaluated using a cell-based cAMP assay. Binding affinity of A2aR was determined using [3H]CGS 21680. A2aR-mediated G-protein activation was quantified using [35S]GTP-γS. The effect of AEA061 on cytokine production was evaluated using primary monocytes and splenocytes. The anti-inflammatory effect of AEA061 was evaluated in the LPS-induced mouse model of inflammation. Results AEA061 had no detectable intrinsic agonist activity towards either rat or human A2aRs. AEA061 enhanced the efficacy of adenosine to rat and human A2aRs by 11.5 and 2.8 fold respectively. AEA061 also enhanced the maximal response by 4.2 and 2.1 fold for the rat and the human A2aR respectively. AEA061 potentiated agonist-mediated Gα activation by 3.7 fold. Additionally, AEA061 enhanced both the affinity as well as the Bmax at the human A2aR by 1.8 and 3 fold respectively. Consistent with the anti-inflammatory role of the A2aR, allosteric enhancement with AEA061 inhibited the production of TNF-α, MIP-1α, MIP-1β, MIP-2, IL-1α, KC and RANTES by LPS-stimulated macrophages and/or splenocytes. Moreover, AEA061 reduced circulating plasma TNF-α and MCP-1 levels and increased plasma IL-10 in endotoxemic A2aR intact, but not in A2aR deficient, mice. Conclusions AEA061 increases affinity and Bmax of A2aR to adenosine, thereby increasing adenosine potency and efficacy, which translates to enhanced A2aR responsiveness. Since the A2aR negatively regulates inflammation, PAMs of the receptor offer a novel means of modulating inflammatory processes.
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Affiliation(s)
- Ajith A Welihinda
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085 USA
| | - Edward P Amento
- Molecular Medicine Research Institute, 428 Oakmead Parkway, Sunnyvale, CA 94085 USA
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Wu YC, Lai HL, Chang WC, Lin JT, Liu YJ, Chern Y. A novel Gαs-binding protein, Gas-2 like 2, facilitates the signaling of the A2A adenosine receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3145-3154. [PMID: 23994616 DOI: 10.1016/j.bbamcr.2013.08.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 08/08/2013] [Accepted: 08/12/2013] [Indexed: 12/13/2022]
Abstract
The A2A adenosine receptor (A2AR) is a G-protein-coupled receptor that contains a long cytoplasmic carboxyl terminus (A2AR-C). We report here that Gas-2 like 2 (G2L2) is a new interacting partner of A2AR-C. The interaction between A2AR and G2L2 was verified by GST pull-down, co-immunoprecipitation, immunocytochemical staining, and fluorescence resonance energy transfer. Expression of G2L2 increased the intracellular cAMP content evoked by A2AR in an A2AR-C-dependent manner. Immunoprecipitation and pull-down assays demonstrated that G2L2 selectively bound to A2AR-C and the inactive form of Gαs to facilitate the recruitment of the trimeric G protein complex to the proximal position of A2AR for efficient activation. Collectively, G2L2 is a new effector that controls the action of A2AR by modulating its ability to regulate the Gαs-mediated cAMP contents.
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Affiliation(s)
- Yi-Chih Wu
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, Taiwan; Taiwan International Graduate Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Hsing-Lin Lai
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Wei-Cheng Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Jiun-Tsai Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yu-Ju Liu
- Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Yijuang Chern
- Taiwan International Graduate Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan; Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.
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22
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Bao Y, Chen Y, Ledderose C, Li L, Junger WG. Pannexin 1 channels link chemoattractant receptor signaling to local excitation and global inhibition responses at the front and back of polarized neutrophils. J Biol Chem 2013; 288:22650-7. [PMID: 23798685 DOI: 10.1074/jbc.m113.476283] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Neutrophil chemotaxis requires excitatory signals at the front and inhibitory signals at the back of cells, which regulate cell migration in a chemotactic gradient field. We have previously shown that ATP release via pannexin 1 (PANX1) channels and autocrine stimulation of P2Y2 receptors contribute to the excitatory signals at the front. Here we show that PANX1 also contributes to the inhibitory signals at the back, namely by providing the ligand for A2A adenosine receptors. In resting neutrophils, we found that A2A receptors are uniformly distributed across the cell surface. In polarized cells, A2A receptors redistributed to the back where their stimulation triggered intracellular cAMP accumulation and protein kinase A (PKA) activation, which blocked chemoattractant receptor signaling. Inhibition of PANX1 blocked A2A receptor stimulation and cAMP accumulation in response to formyl peptide receptor stimulation. Treatments that blocked endogenous A2A receptor signaling impaired the polarization and migration of neutrophils in a chemotactic gradient field and resulted in enhanced ERK and p38 MAPK signaling in response to formyl peptide receptor stimulation. These findings suggest that chemoattractant receptors require PANX1 to trigger excitatory and inhibitory signals that synergize to fine-tune chemotactic responses at the front and back of neutrophils. PANX1 channels thus link local excitatory signals to the global inhibitory signals that orchestrate chemotaxis of neutrophils in gradient fields.
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Affiliation(s)
- Yi Bao
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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Huot P, Johnston TH, Koprich JB, Fox SH, Brotchie JM. The Pharmacology of l-DOPA-Induced Dyskinesia in Parkinson’s Disease. Pharmacol Rev 2013; 65:171-222. [DOI: 10.1124/pr.111.005678] [Citation(s) in RCA: 233] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Hua X, Chason KD, Jania C, Acosta T, Ledent C, Tilley SL. Gs-coupled adenosine receptors differentially limit antigen-induced mast cell activation. J Pharmacol Exp Ther 2012; 344:426-35. [PMID: 23149337 DOI: 10.1124/jpet.112.198978] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mast cell activation results in the immediate release of proinflammatory mediators prestored in cytoplasmic granules, as well as initiation of lipid mediator production and cytokine synthesis by these resident tissue leukocytes. Allergen-induced mast cell activation is central to the pathogenesis of asthma and other allergic diseases. Presently, most pharmacological agents for the treatment of allergic disease target receptors for inflammatory mediators. Many of these mediators, such as histamine, are released by mast cells. Targeting pathways that limit antigen-induced mast cell activation may have greater therapeutic efficacy by inhibiting the synthesis and release of many proinflammatory mediators produced in the mast cell. In vitro studies using cultured human and mouse mast cells, and studies of mice lacking A(2B) receptors, suggest that adenosine receptors, specifically the G(s)-coupled A(2A) and A(2B) receptors, might provide such a target. Here, using a panel of mice lacking various combinations of adenosine receptors, and mast cells derived from these animals, we show that adenosine receptor agonists provide an effective means of inhibition of mast cell degranulation and induction of cytokine production both in vitro and in vivo. We identify A(2B) as the primary receptor limiting mast cell degranulation, whereas the combined activity of A(2A) and A(2B) is required for the inhibition of cytokine synthesis.
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Affiliation(s)
- Xiaoyang Hua
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of North Carolina at Chapel Hill, 8033 Burnett-Womack, Chapel Hill, NC 27599-7219, USA
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Konrad FM, Witte E, Vollmer I, Stark S, Reutershan J. Adenosine receptor A2b on hematopoietic cells mediates LPS-induced migration of PMNs into the lung interstitium. Am J Physiol Lung Cell Mol Physiol 2012; 303:L425-38. [DOI: 10.1152/ajplung.00387.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Uncontrolled transmigration of polymorphonuclear leukocytes (PMNs) into the different compartments of the lungs (intravascular, interstitial, alveolar) is a critical event in the early stage of acute lung injury and acute respiratory distress syndrome. Adenosine receptor A2b is highly expressed in the inflamed lungs and has been suggested to mediate cell trafficking. In a murine model of LPS-induced lung inflammation, we investigated the role of A2b on migration of PMNs into the different compartments of the lung. In A2b−/− mice, LPS-induced accumulation of PMNs was significantly higher in the interstitium, but not in the alveolar space. In addition, pulmonary clearance of PMNs was delayed in A2b−/− mice. Using chimeric mice, we identified A2b on hematopoietic cells as crucial for PMN migration. A2b did not affect the release of relevant chemokines into the alveolar space. LPS-induced microvascular permeability was under the control of A2b on both hematopoietic and nonhematopoietic cells. Activation of A2b on endothelial cells also reduced formation of LPS-induced stress fibers, highlighting its role for endothelial integrity. A specific A2b agonist (BAY 60–6583) was effective in decreasing PMN migration into the lung interstitium and microvascular permeability. In addition, in vitro transmigration of human PMNs through a layer of human endothelial or epithelial cells was A2b dependent. Activation of A2b on human PMNs reduced oxidative burst activity. Together, our results demonstrate anti-inflammatory effects of A2b on two major characteristics of acute lung injury, with a distinct role of hematopoietic A2b for cell trafficking and endothelial A2b for microvascular permeability.
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Affiliation(s)
- Franziska M. Konrad
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Tübingen, Tübingen, Germany
| | - Esther Witte
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Tübingen, Tübingen, Germany
| | - Irene Vollmer
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Tübingen, Tübingen, Germany
| | - Stefanie Stark
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Tübingen, Tübingen, Germany
| | - Jörg Reutershan
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Tübingen, Tübingen, Germany
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Peeters MC, Wisse LE, Dinaj A, Vroling B, Vriend G, Ijzerman AP. The role of the second and third extracellular loops of the adenosine A1 receptor in activation and allosteric modulation. Biochem Pharmacol 2012; 84:76-87. [PMID: 22449615 DOI: 10.1016/j.bcp.2012.03.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 03/13/2012] [Accepted: 03/14/2012] [Indexed: 10/28/2022]
Abstract
The adenosine A1 receptor is a member of the large membrane protein family that signals through G proteins, the G protein-coupled receptors (GPCRs). GPCRs consist of seven transmembrane domains connected by three intracellular and three extracellular loops. Their N-terminus is extracellular, the C-terminal tail is in the cytoplasm. The transmembrane domains in receptor subfamilies that bind the same endogenous ligand, such as dopamine or adenosine, tend to be highly similar. In contrast, the loop regions can vary greatly, both in sequence and in length, and the role these loops have in the activation mechanism of the receptors remains unclear. Here, we investigated the activating role of the second and third extracellular loop of the human adenosine A1 receptor. By means of an (Ala)3 mutagenic scan in which consecutive sets of three amino acids were mutated into alanine residues in EL2 and a classical alanine scan in EL3, we revealed a strong regulatory role for the second extracellular loop (EL2) of the human adenosine A1 receptor. Besides many residues in the second and the third extracellular loops important for adenosine A1 receptor activation, we also identified two residues in EL2, a tryptophan and a glutamate, that affect the influence of the allosteric modulator PD81,723. These results, combined with a comparison of the different receptor loop regions, provide insight in the activation mechanism of this typical class A GPCR and further emphasize the unique pharmacological profile the loops can provide to individual receptors, even within subfamilies of GPCRs.
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Affiliation(s)
- M C Peeters
- Division of Medicinal Chemistry, Leiden/Amsterdam Centre for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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Vuaden FC, Savio LEB, Ramos DB, Casali EA, Bogo MR, Bonan CD. Endotoxin-induced effects on nucleotide catabolism in mouse kidney. Eur J Pharmacol 2011; 674:422-9. [PMID: 22108548 DOI: 10.1016/j.ejphar.2011.11.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 09/30/2011] [Accepted: 11/02/2011] [Indexed: 12/20/2022]
Abstract
Extracellular adenosine 5'-triphosphate (ATP) acts as a proinflammatory mediator. Adenosine, the final product of ATP breakdown, is an anti-inflammatory compound, acting mainly on adenosine A(2A) receptors. Considering that the kidney is an organ strongly affected during systemic inflammatory responses and that ectonucleotidases are responsible for the control of extracellular nucleotide and nucleoside levels, we examined the endotoxin-induced effects on ectonucleotidases in kidney membranes of mice, and whether CGS-21680 hydrochloride (3-[4-[2-[[6-amino-9-[(2R,3R,4S,5S)-5-(ethylcarbamoyl)-3,4-dihydroxy-oxolan-2-yl]purin-2-yl]amino]ethyl]phenyl]propanoic acid), a selective adenosine A(2A) receptor agonist, antagonizes the lipopolysaccharide (LPS)-induced effects on nucleotide catabolism in kidney. Animals were injected intraperitoneally with 12 mg/kg LPS and/or 0.5mg/kg CGS-21680 or saline. Nucleotidase activities were determined in kidney membrane preparations and ATP metabolism was measured by high performance liquid chromatography (HPLC) assay. Analysis of ectonucleotidase expression was carried out by semi-quantitative semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Exposure to endotoxemia promoted an increase in ATP and p-Nitrophenyl thymidine 5'-monophosphate (p-Nph-5'-TMP) hydrolysis, and a decrease in adenosine 5'-monophosphate (AMP) hydrolysis. CGS-21680 treatment failed to reverse these changes. HPLC analysis indicated a decrease in extracellular ATP and adenosine levels in groups treated with LPS and LPS plus CGS-21680. The expression pattern of ectonucleotidases revealed an increase in Entpd3, Enpp2, and Enpp3 mRNA levels after LPS injection. These findings indicate that nucleotide and nucleoside availability in mouse kidney is altered at different stages of endotoxemia, in order to protect the integrity of this organ when exposed to systemic inflammation.
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Affiliation(s)
- Fernanda C Vuaden
- Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, 90035-003, Porto Alegre, RS, Brazil
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Activation of adenosine A2A receptor up-regulates BDNF expression in rat primary cortical neurons. Neurochem Res 2011; 36:2259-69. [PMID: 21792677 DOI: 10.1007/s11064-011-0550-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2011] [Revised: 06/18/2011] [Accepted: 07/14/2011] [Indexed: 01/12/2023]
Abstract
As a member of neurotrophin family, brain derived neurotrophic factor (BDNF) plays critical roles in neuronal development, differentiation, synaptogenesis, and neural protection from the harmful stimuli. There have been reported that adenosine A2(A) receptor subtype is widely distributed in the brain regions, such as hippocampus, striatum, and cortex. Adenosine A2(A) receptor is colocalized with BDNF in brain regions and the functional interaction between A2(A) receptor stimulation and BDNF action has been suggested. In this study, we investigated the possibility that the activation of A2(A) receptor modulates BDNF production in rat primary cortical neuron. CGS21680, an adenosine A2(A) receptor agonist, induced BDNF expression and release. An antagonist against A2(A) receptor, ZM241385, prevented CGS21680-induced increase in BDNF production. A2(A) receptor stimulation induced the activation of Akt-GSK-3β signaling pathway and the blockade of the signaling pathway with specific inhibitors abolished the increase in BDNF production, possibly via modulation of ERK1/2-CREB pathway. The physiological roles of A2(A) receptor-induced BDNF production was demonstrated by the protection of neurons from the excitotoxicity and increased neurite extension as well as synapse formation from immature and mature neurons. Taken together, activation of A2(A) receptor regulates BDNF production in rat cortical neuron, which provides neuro-protective action.
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Differential role of the carboxy-terminus of the A(2B) adenosine receptor in stimulation of adenylate cyclase, phospholipase Cbeta, and interleukin-8. Purinergic Signal 2009; 5:289-98. [PMID: 19125355 DOI: 10.1007/s11302-008-9129-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 12/10/2008] [Indexed: 10/21/2022] Open
Abstract
In human mast cells and microvascular endothelial cells, the A(2B) adenosine receptor controls at least three independent signaling pathways, i.e., Gs-mediated stimulation of adenylate cyclase, Gq-mediated stimulation of phospholipase Cbeta, and Gs/Gq-independent upregulation of IL-8. Functional analysis of cells transfected with full-length and truncated receptor constructs revealed that the A(2B) receptor C-terminus is important for coupling to Gs and Gq proteins. Removal of the entire cytoplasmic portion in the A(2B) receptor C-terminus rendered it incapable of stimulating adenylate cyclase and phospholipase Cbeta. Conversely, removal of the distal 16 amino acids facilitated signal transduction from the receptor to the downstream Gs but not Gq proteins. However, the A(2B) receptor C-terminus is not essential for upregulation of IL-8. Analysis of chimeric A(2A)/A(2B) receptors demonstrated that only chimeras containing the third intracellular loop of the A(2B) receptor mediated agonist-dependent IL-8 reporter stimulation, suggesting that this domain is important for upregulation of IL-8.
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Navar LG, Arendshorst WJ, Pallone TL, Inscho EW, Imig JD, Bell PD. The Renal Microcirculation. Compr Physiol 2008. [DOI: 10.1002/cphy.cp020413] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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31
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Navar LG, Arendshorst WJ, Pallone TL, Inscho EW, Imig JD, Bell PD. The Renal Microcirculation. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00015-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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32
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Russell JM, Stephenson GS, Yellowley CE, Benton HP. Adenosine inhibition of lipopolysaccharide-induced interleukin-6 secretion by the osteoblastic cell line MG-63. Calcif Tissue Int 2007; 81:316-26. [PMID: 17705048 DOI: 10.1007/s00223-007-9060-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 07/06/2007] [Indexed: 12/21/2022]
Abstract
Adenosine is known to inhibit inflammatory responses in many cell systems via a family of purine receptors termed "P1." The P1 family consists of the adenosine receptors (ADORA) of subtypes A(1), A(2a), A(2b), and A(3). In order to assess whether adenosine has anti-inflammatory actions in osteoblastic cells, we investigated its effects on lipopolysaccharide (LPS)-induced interleukin 6 (IL-6) release in an in vitro inflammatory functional response model. We showed that the osteoblastic cell line MG-63 expresses ADORA(1), A(2a), and A(2b) but not A(3). Treatment of MG-63 cells with adenosine and pharmacological ADORA agonist 5'-N-ethylcarboxamidoadenosine or 2-[4-(2-p-carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS21680) inhibits LPS-induced IL-6 release. This inhibition was protein kinase A (PKA)-dependent and mimicked by treatment with the adenylate cyclase activator forskolin. Treatment of MG-63 with the ADORA(2a)-specific antagonist ZM241385 partially reversed the inhibitory effects of ADORA stimulation on LPS-induced IL-6 release. Overall, these data suggest that ADORA(2a) is involved in the regulation of LPS-induced IL-6 release, thus illustrating a regulatory role for adenosine receptors in the control of inflammation and potentially osteoclastogenesis and bone resorption.
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Affiliation(s)
- Joseph M Russell
- Department of Veterinary Medicine, Anatomy, Physiology, and Cell Biology, University of California, Davis, CA 95616, USA.
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Ezeamuzie CI, Khan I. The role of adenosine A2 receptors in the regulation of TNF-α production and PGE2 release in mouse peritoneal macrophages. Int Immunopharmacol 2007; 7:483-90. [PMID: 17321471 DOI: 10.1016/j.intimp.2006.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2006] [Revised: 11/29/2006] [Accepted: 12/04/2006] [Indexed: 11/19/2022]
Abstract
The adenosine A(2) receptors are known to mediate most of the anti-inflammatory activities of adenosine. In lipopolysaccharides (LPS)-stimulated macrophages adenosine strongly inhibits TNF-alpha release, but may also enhance PGE(2) generation. The aims of this study were to determine the relative contributions of the A(2A) and A(2B) receptor subclasses in these two effects and to determine whether the enhanced release of PGE(2) contributes to the inhibition of TNF-alpha release. In LPS-stimulated mouse macrophages, adenosine potently inhibited TNF-alpha production and also potentiated PGE(2) release, though less potently (IC(50)=250 nM vs EC(50) approximately 8 microM, respectively). The non-selective adenosine receptor agonist NECA, and the selective A(2A) receptor agonist CGS21680 also inhibited TNF-alpha production even more potently (IC(50)=4.8 and 2.3 nM, respectively). NECA, but not CGS21680, also enhanced PGE(2) production. The selective A(2A) receptor antagonist ZM241385 (30 nM), but not the selective A(2B) receptor antagonist MRS1754 (30 nM), blocked the inhibitory effect of NECA and CGS21680 on TNF-alpha release. On the other hand, MRS1754, but not ZM241385, abolished the PGE(2) potentiating effect of NECA. Pre-treatment with indomethacin (1 microM) abolished adenosine-induced PGE(2) release enhancement but did not prevent the inhibition of TNF-alpha release. These results show that in this system, the inhibition of TNF-alpha release by adenosine is mediated by the A(2A) receptors whereas the enhancement of PGE(2) release appears to be mediated by the A(2B) receptors. The results also show that while exogenous PGE(2) is a potent inhibitor of TNF-alpha release, the enhanced PGE(2) release induced by adenosine does not appear to contribute to the inhibition of TNF-alpha release.
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Affiliation(s)
- C I Ezeamuzie
- Department of Pharmacology, Faculty of Medicine, Kuwait University, Kuwait
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Matsumoto ML, Narzinski K, Nikiforovich GV, Baranski TJ. A Comprehensive Structure-Function Map of the Intracellular Surface of the Human C5a Receptor. J Biol Chem 2007; 282:3122-33. [PMID: 17090530 DOI: 10.1074/jbc.m607683200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Within any given cell many G protein-coupled receptors are expressed in the presence of multiple G proteins, yet most receptors couple to a specific subset of G proteins to elicit their programmed response. Numerous studies demonstrate that the carboxyl-terminal five amino acids of the Galpha subunits are a major determinant of specificity, however the receptor determinants of specificity are less clear. We have used a collection of 133 functional mutants of the C5a receptor obtained in a mutagenesis screen targeting the intracellular loops and the carboxyl terminus (Matsumoto, M. L., Narzinski, K., Kiser, P. D., Nikiforovich, G. V., and Baranski, T. J. (2007) J. Biol. Chem. 282, 3105-3121) to investigate how specificity is encoded. Each mutant, originally selected for its ability to signal through a nearly full-length Galpha(i) in yeast, was tested to see whether it could activate three versions of chimeric Galpha subunits consisting of Gpa1 fused to the carboxyl-terminal five amino acids of Galpha(i), Galpha(q), or Galpha(s) in yeast. Surprisingly the carboxyl-terminal tail of the C5a receptor is the most important specificity determinant in that nearly all mutants in this region showed a gain in coupling to Galpha(q) and/or Galpha(s). More than half of the receptors mutated in the second intracellular loop also demonstrated broadened G protein coupling. Given a lack of selective advantage for this broadened signaling in the initial screen, we propose a model in which the carboxyl-terminal tail acts together with the intracellular loops to generate a specificity filter for receptor-G protein interactions that functions primarily to restrict access of incorrect G proteins to the receptor.
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Affiliation(s)
- Marissa L Matsumoto
- Department of Medicine and Molecular Biology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Sahin B, Galdi S, Hendrick J, Greene RW, Snyder GL, Bibb JA. Evaluation of neuronal phosphoproteins as effectors of caffeine and mediators of striatal adenosine A2A receptor signaling. Brain Res 2007; 1129:1-14. [PMID: 17157277 PMCID: PMC1847645 DOI: 10.1016/j.brainres.2006.10.059] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2006] [Revised: 10/02/2006] [Accepted: 10/26/2006] [Indexed: 11/26/2022]
Abstract
Adenosine A(2A) receptors are predominantly expressed in the dendrites of enkephalin-positive gamma-aminobutyric acidergic medium spiny neurons in the striatum. Evidence indicates that these receptors modulate striatal dopaminergic neurotransmission and regulate motor control, vigilance, alertness, and arousal. Although the physiological and behavioral correlates of adenosine A(2A) receptor signaling have been extensively studied using a combination of pharmacological and genetic tools, relatively little is known about the signal transduction pathways that mediate the diverse biological functions attributed to this adenosine receptor subtype. Using a candidate approach based on the coupling of these receptors to adenylate cyclase-activating G proteins, a number of membranal, cytosolic, and nuclear phosphoproteins regulated by PKA were evaluated as potential mediators of adenosine A(2A) receptor signaling in the striatum. Specifically, the adenosine A(2A) receptor agonist, CGS 21680, was used to determine whether the phosphorylation state of each of the following PKA targets is responsive to adenosine A(2A) receptor stimulation in this tissue: Ser40 of tyrosine hydroxylase, Ser9 of synapsin, Ser897 of the NR1 subunit of the N-methyl-d-aspartate-type glutamate receptor, Ser845 of the GluR1 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate receptor, Ser94 of spinophilin, Thr34 of the dopamine- and cAMP-regulated phosphoprotein, M(r) 32,000, Ser133 of the cAMP-response element-binding protein, Thr286 of Ca(2+)/calmodulin-dependent protein kinase II, and Thr202/Tyr204 and Thr183/Tyr185 of the p44 and p42 isoforms, respectively, of mitogen-activated protein kinase. Although the substrates studied differed considerably in their responsiveness to selective adenosine A(2A) receptor activation, the phosphorylation state of all postsynaptic PKA targets was up-regulated in a time- and dose-dependent manner by treatment with CGS 21680, whereas presynaptic PKA substrates were unresponsive to this agent, consistent with the postsynaptic localization of adenosine A(2A) receptors. Finally, the phosphorylation state of these proteins was further assessed in vivo by systemic administration of caffeine.
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Affiliation(s)
- Bogachan Sahin
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Claus M, Neumann S, Kleinau G, Krause G, Paschke R. Structural determinants for G-protein activation and specificity in the third intracellular loop of the thyroid-stimulating hormone receptor. J Mol Med (Berl) 2006; 84:943-54. [PMID: 16955277 DOI: 10.1007/s00109-006-0087-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Accepted: 06/12/2006] [Indexed: 11/24/2022]
Abstract
The selectivity of G-protein recognition is determined by the intracellular loops (ICLs) of seven-transmembrane-spanning receptors. In a previous study, we have shown that the N-terminal and central portions of ICL2 from F525 to D530 participate in dual Galphas-/Galphaq-protein activation by the thyroid-stimulating hormone receptor (TSHR). ICL3 is another major determinant for G-protein activation. Therefore, the aim of our study was to identify important amino acids within ICL3 of the TSHR to gain insight in more detail about its specific function for Galphas- and Galphaq-protein activation and selectivity. Single-alanine substitutions of residues in the N-terminal, middle, and C-terminal region of ICL3 were generated. N-terminal residues Y605 and V608 and C-terminal positions K618, K621, and I622 were identified as selectively important for Galphaq activation, whereas mutations in the center of ICL3 had no effect on TSHR signaling. Our findings provide evidence for an amino acid pattern in the N- and C-terminal part of ICL3, which is involved in Galphaq-mediated signaling. Furthermore, molecular modeling of interaction of TSHR ICL2 and 3 with Galphaq suggests three potential contact sites: TSHR C-terminal ICL3 with beta5-6 loop of Galphaq, TSHR ICL2 residues I523-R531 with beta2-3 loop and N-terminal helix of Galphaq, and TSHR ICL2/transmembrane helix (TMH) 3+ICL3/TMH6 with C-terminal tail of Galphaq.
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MESH Headings
- Alanine
- Amino Acid Sequence
- Animals
- Binding Sites
- COS Cells
- Chlorocebus aethiops
- Cyclic AMP/metabolism
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gq-G11/chemistry
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- GTP-Binding Protein alpha Subunits, Gs/chemistry
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Humans
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Thyrotropin/agonists
- Receptors, Thyrotropin/chemistry
- Receptors, Thyrotropin/genetics
- Receptors, Thyrotropin/metabolism
- Signal Transduction/drug effects
- Thyrotropin/metabolism
- Thyrotropin/pharmacology
- Transfection
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Affiliation(s)
- Maren Claus
- III. Medical Department, University of Leipzig, Philipp-Rosenthal-Str. 27, 04103, Leipzig, Germany
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Bhattacharya S, Youkey R, Ghartey K, Leonard M, Linden J, Tucker A. The allosteric enhancer PD81,723 increases chimaeric A1/A2A adenosine receptor coupling with Gs. Biochem J 2006; 396:139-46. [PMID: 16390330 PMCID: PMC1449996 DOI: 10.1042/bj20051422] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PD81,723 {(2-amino-4,5-dimethyl-3-thienyl)-[3-(trifluromethyl)-phenyl]methanone} is a selective allosteric enhancer of the G(i)-coupled A1 AR (adenosine receptor) that is without effect on G(s)-coupled A2A ARs. PD81,723 elicits a decrease in the dissociation kinetics of A1 AR agonist radioligands and an increase in functional agonist potency. In the present study, we sought to determine whether enhancer sensitivity is dependent on coupling domains or G-protein specificity of the A1 AR. Using six chimaeric A1/A2A ARs, we show that the allosteric effect of PD81,723 is maintained in a chimaera in which the predominant G-protein-coupling domain of the A1 receptor, the 3ICL (third intracellular loop), is replaced with A2A sequence. These chimaeric receptors are dually coupled with G(s) and G(i), and PD81,723 increases the potency of N6-cyclopentyladenosine to augment cAMP accumulation with or without pretreatment of cells with pertussis toxin. Thus PD81,723 has similar functional effects on chimaeric receptors with A1 transmembrane sequences that couple with G(i) or G(s). This is the first demonstration that an allosteric regulator can function in the context of a switch in G-protein-coupling specificity. There is no enhancement by PD81,723 of G(i)-coupled A2A chimaeric receptors with A1 sequence replacing A2A sequence in the 3ICL. The results suggest that the recognition site for PD81,723 is on the A1 receptor and that the enhancer acts to directly stabilize the receptor to a conformational state capable of coupling with G(i) or G(s).
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MESH Headings
- Adenosine/analogs & derivatives
- Adenosine/pharmacology
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic alpha-Antagonists/pharmacology
- Allosteric Regulation/drug effects
- Animals
- Cell Line
- Cyclic AMP/metabolism
- Dogs
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Humans
- Iodobenzenes/pharmacology
- Kidney/cytology
- Protein Conformation
- Protein Interaction Mapping
- Protein Structure, Tertiary
- Radioligand Assay
- Receptor, Adenosine A1/chemistry
- Receptor, Adenosine A1/drug effects
- Receptor, Adenosine A1/genetics
- Receptor, Adenosine A1/metabolism
- Receptor, Adenosine A2A/chemistry
- Receptor, Adenosine A2A/drug effects
- Receptor, Adenosine A2A/genetics
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/drug effects
- Recombinant Fusion Proteins/metabolism
- Thiophenes/pharmacology
- Transfection
- Xanthines/pharmacology
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Affiliation(s)
- Samita Bhattacharya
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
| | - Rebecca L. Youkey
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
| | - Kobina Ghartey
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
| | - Matthew Leonard
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
| | - Joel Linden
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
- †Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
- ‡Cardiovascular Research Center, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
| | - Amy L. Tucker
- *Department of Internal Medicine, Cardiovascular Division, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
- †Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
- ‡Cardiovascular Research Center, University of Virginia Health Sciences Center, Charlottesville, VA 22908, U.S.A
- To whom correspondence should be addressed, at Box 801394, MR5 Room G219, University of Virginia Health System, Charlottesville, VA 22908, U.S.A. (email )
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Sato A, Terata K, Miura H, Toyama K, Loberiza FR, Hatoum OA, Saito T, Sakuma I, Gutterman DD. Mechanism of vasodilation to adenosine in coronary arterioles from patients with heart disease. Am J Physiol Heart Circ Physiol 2005; 288:H1633-40. [PMID: 15772334 DOI: 10.1152/ajpheart.00575.2004] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine is a key myocardial metabolite that elicits coronary vasodilation in a variety of pathophysiological conditions. We examined the mechanism of adenosine-induced vasodilation in coronary arterioles from patients with heart disease. Human coronary arterioles (HCAs) were dissected from pieces of the atrial appendage obtained at the time of cardiac surgery and cannulated for the measurement of internal diameter with videomicroscopy. Adenosine-induced vasodilation was not inhibited by endothelial denudation, but A(2) receptor antagonism with 3,7-dimethyl-1-propargylxanthine and adenylate cyclase (AC) inhibition with SQ22536 significantly attenuated the dilation. In contrast, A(1) receptor antagonism with 8-cyclopentyl-1,3-dipropylxanthine significantly augmented the sensitivity to adenosine. Moreover, dilation to A(2a) receptor activation with 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido-adenosine hydrochloride was reduced by the A(1) receptor agonist (2S)-N(6)-(2-endo-norbornyl)adenosine. The nonspecific calcium-activated potassium (K(Ca)) channel blocker tetrabutylammonium attenuated adenosine-induced dilation, as did the intermediate-conductance K(Ca) blocker clotrimazole. Neither the large-conductance K(Ca) blocker iberiotoxin nor small-conductance K(Ca) blocker apamin altered the dilation. In conclusion, adenosine endothelium independently dilates HCAs from patients with heart disease through a receptor-mediated mechanism that involves the activation of intermediate-conductance K(Ca) channels via an AC signaling pathway. The roles of A(1) and A(2) receptor subtypes are opposing, with the former being inhibitory to AC-mediated dilator actions of the latter. These observations identify unique fundamental physiological characteristics of the human coronary circulation and may help to target the use of novel adenosine analogs for vasodilation in perfusion imaging or suggest new strategies for myocardial preconditioning.
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Affiliation(s)
- Atsushi Sato
- Dept. of Medicine, Cardiovascular Center, and Veterans Administration Medical Center, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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Zhang JG, Hepburn L, Cruz G, Borman RA, Clark KL. The role of adenosine A2A and A2B receptors in the regulation of TNF-α production by human monocytes. Biochem Pharmacol 2005; 69:883-9. [DOI: 10.1016/j.bcp.2004.12.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2004] [Accepted: 12/28/2004] [Indexed: 10/25/2022]
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Abstract
Caveolae are flask-shaped invaginations in the membrane that depend on the contents of cholesterol and on the structural protein caveolin. The organisation of caveolae in parallel strands between dense bands in smooth muscle is arguably unique. It is increasingly recognised, bolstered in large part by recent studies in caveolae deficient animals, that caveolae sequester and regulate a variety of signalling intermediaries. The role of caveolae in smooth muscle signal transduction, as inferred from studies on transgenic animals and in vitro approaches, is the topic of the current review. Both G-protein coupled receptors and tyrosine kinase receptors are believed to cluster in caveolae, and the exciting possibility that caveolae provide a platform for interactions between the sarcoplasmic reticulum and plasmalemmal ion channels is emerging. Moreover, messengers involved in Ca2+ sensitization of myosin phosphorylation and contraction may depend on caveolae or caveolin. Caveolae thus appear to constitute an important signalling domain that plays a role not only in regulation of smooth muscle tone, but also in proliferation, such as seen in neointima formation and atherosclerosis.
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Affiliation(s)
- Andreas Bergdahl
- Department of Physiological Sciences, Lund University, Biomedical Centre, Sweden
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41
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Liu C, Sandford G, Fei G, Nicholas J. Galpha protein selectivity determinant specified by a viral chemokine receptor-conserved region in the C tail of the human herpesvirus 8 g protein-coupled receptor. J Virol 2004; 78:2460-71. [PMID: 14963144 PMCID: PMC369212 DOI: 10.1128/jvi.78.5.2460-2471.2004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The viral G-protein coupled receptor (vGPCR) specified by human herpesvirus 8 (HHV-8) open reading frame 74 (ORF74) is a ligand-independent chemokine receptor that has structural and functional homologues among other characterized gammaherpesviruses and related receptors in the betaherpesviruses. Sequence comparisons of the gammaherpesvirus vGPCRs revealed a highly conserved region in the C tail, just distal to the seventh transmembrane domain. Mutagenesis of the corresponding codons of HHV-8 ORF74 was carried out to provide C-tail-altered proteins for functional analyses. By measuring receptor-activated vascular endothelial growth factor promoter induction and NF-kappaB, mitogen-activated protein kinase, and Ca(2+) signaling, we found that while some altered receptors showed general signaling deficiencies, others had distinguishable activation profiles, suggestive of selective Galpha protein coupling. This was supported by the finding that vGPCR and representative functionally altered variants, vGPCR.8 (R322W) and vGPCR.15 (M325S), were affected differently by inhibitors of Galpha(i) (pertussis toxin), protein kinase C (GF109203X), and phosphatidylinositol 3-kinase (wortmannin). Consistent with the signaling data, [(35)S]GTPgammaS incorporation assays revealed preferential coupling of vGPCR.15 to Galpha(q) and an inability of vGPCR.8 to couple functionally to Galpha(q). However, both variants, wild-type vGPCR, and a C-tail deletion version of the receptor were equally able to associate physically with Galpha(q). Combined, our data demonstrate that HHV-8 vGPCR contains discrete sites of Galpha interaction and that receptor residues in the proximal region of the cytoplasmic tail are determinants of Galpha protein coupling specificity.
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Affiliation(s)
- Chaoqi Liu
- Molecular Virology Laboratories, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, Maryland 21231, USA
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Kinsel JF, Sitkovsky MV. Possible targeting of G protein coupled receptors to manipulate inflammation in vivo using synthetic and natural ligands. Ann Rheum Dis 2003; 62 Suppl 2:ii22-4. [PMID: 14532142 PMCID: PMC1766756 DOI: 10.1136/ard.62.suppl_2.ii22] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Cyclic AMP elevating Gs protein coupled receptors were considered for a long time to be immunosuppressive. One of these receptors, adenosine A(2A) receptor, was implicated in a physiological mechanism that down regulates inflammation and protects tissues from excessive immune mediated damage. Targeting of these receptors by selective agonists may lead to better protocols of anti-inflammatory treatments. At the same time inhibiting the Gs protein coupled mediated signalling with antagonists could be explored in studies of approaches to enhance inflammation and tissue damage. Enhancement of targeted tissue damage is highly desirable when it is cancerous tissue, while enhancement of inflammatory events might be desirable in the development of new vaccine adjuvants.
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43
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Abstract
The purine nucleoside adenosine acts via four distinct adenosine receptor subtypes: the adenosine A(1), A(2A), A(2B), and A(3) receptor. They are all G protein-coupled receptors (GPCR) coupling to classical second messenger pathways such as modulation of cAMP production or the phospholipase C (PLC) pathway. In addition, they couple to mitogen-activated protein kinases (MAPK), which could give them a role in cell growth, survival, death and differentiation. Although each of the adenosine receptors can activate one or more of the MAPKs, the mechanisms appear to differ substantially, both between receptor subtypes in the same cell type and between the same receptor in different cell types.
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Affiliation(s)
- Gunnar Schulte
- Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77, Stockholm, Sweden.
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Queiroz G, Talaia C, Gonçalves J. Adenosine A2A receptor-mediated facilitation of noradrenaline release involves protein kinase C activation and attenuation of presynaptic inhibitory receptor-mediated effects in the rat vas deferens. J Neurochem 2003; 85:740-8. [PMID: 12694400 DOI: 10.1046/j.1471-4159.2003.01715.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the epididymal portion of rat vas deferens, facilitation of noradrenaline release mediated by adenosine A2A receptors, but not that mediated by beta2-adrenoceptors or by direct activation of adenylyl cyclase, was attenuated by blockade of alpha2-adrenoceptors and abolished by simultaneous blockade of alpha2-adrenoceptors, adenosine A1 and P2Y receptors. The adenosine A2A receptor-mediated facilitation was not changed by inhibitors of protein kinase A, protein kinase G or calmodulin kinase II but was prevented by inhibition of protein kinase C with chelerythrine or bisindolylmaleimide XI. Activation of protein kinase C with phorbol 12-myristate 13-acetate caused a facilitation of noradrenaline release that was abolished by bisindolylmaleimide XI and reduced by antagonists of alpha2-adrenoceptors, adenosine A1 and P2Y receptors. Activation of adenosine A2A receptors attenuated the inhibition of noradrenaline release mediated by the presynaptic inhibitory receptors. This effect was mimicked by phorbol 12-myristate 13-acetate and prevented by bisindolylmaleimide XI. It is concluded that adenosine A2A receptors facilitate noradrenaline release by a mechanism that involves a protein kinase C-mediated attenuation of effects mediated by presynaptic inhibitory receptors, namely alpha2-adrenoceptors, adenosine A1 and P2Y receptors.
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Affiliation(s)
- Glória Queiroz
- Laboratório de Farmacologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
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45
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Gomez G, Sitkovsky MV. Targeting G protein-coupled A2a adenosine receptors to engineer inflammation in vivo. Int J Biochem Cell Biol 2003; 35:410-4. [PMID: 12565702 DOI: 10.1016/s1357-2725(02)00177-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
G protein-coupled adenosine receptors are the subject of intense study as immunomodulators of inflammation especially since the recent demonstration that the A2a receptor acts to down-regulate inflammation and inhibit tissue damage in vivo [Nature 414 (6866) (2001) 916]. The adverse effects of overactive inflammation are evident in diseases e.g. sepsis, rheumatoid arthritis, and multiple sclerosis underscoring the importance of inhibiting inflammation or selectively enhancing inflammatory processes. It has been shown recently that the A2a adenosine receptor is a critical component of an endogenous "immunosuppressive loop" in which extracellular adenosine that accumulates due to local hypoxia caused by inflammatory insult signals through cAMP-elevating A2a receptors in a delayed negative feedback manner. Understanding how tissues regulate inflammation will provide the information necessary to allow for the engineering, or selective targeting, of endogenous inflammatory pathways. Recognition of A2a receptors as "natural" or endogenous brakes of inflammation provides the intellectual scaffolding needed to pursue these goals.
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Affiliation(s)
- Gregorio Gomez
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 10/11N311, 10 Center Drive-MSC 1892, Bethesda, MD 20892-1892, USA
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46
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Hillion J, Canals M, Torvinen M, Casado V, Scott R, Terasmaa A, Hansson A, Watson S, Olah ME, Mallol J, Canela EI, Zoli M, Agnati LF, Ibanez CF, Lluis C, Franco R, Ferre S, Fuxe K. Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors. J Biol Chem 2002; 277:18091-7. [PMID: 11872740 DOI: 10.1074/jbc.m107731200] [Citation(s) in RCA: 375] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antagonistic and reciprocal interactions are known to exist between adenosine and dopamine receptors in the striatum. In the present study, double immunofluorescence experiments with confocal laser microscopy showed a high degree of colocalization of adenosine A(2A) receptors (A(2A)R) and dopamine D(2) receptors (D(2)R) in cell membranes of SH-SY5Y human neuroblastoma cells stably transfected with human D(2)R and in cultured striatal cells. A(2A)R/D(2)R heteromeric complexes were demonstrated in coimmunoprecipitation experiments in membrane preparations from D(2)R-transfected SH-SY5Y cells and from mouse fibroblast Ltk(-) cells stably transfected with human D(2)R (long form) and transiently cotransfected with the A(2A)R double-tagged with hemagglutinin. Long term exposure to A(2A)R and D(2)R agonists in D(2)R-cotransfected SH-SY5Y cells resulted in coaggregation, cointernalization and codesensitization of A(2A)R and D(2)R. These results give a molecular basis for adenosine-dopamine antagonism at the membrane level and have implications for treatment of Parkinson's disease and schizophrenia, in which D(2)R are involved.
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Affiliation(s)
- Joelle Hillion
- Department of Neuroscience, Karolinska Institute, 17177 Stockholm, Sweden.
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Langer I, Vertongen P, Perret J, Waelbroeck M, Robberecht P. A small sequence in the third intracellular loop of the VPAC(1) receptor is responsible for its efficient coupling to the calcium effector. Mol Endocrinol 2002; 16:1089-96. [PMID: 11981043 DOI: 10.1210/mend.16.5.0822] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The stimulatory effect of VIP on intracellular calcium concentration ([Ca(2+)](i)) has been investigated in Chinese hamster ovary cells stably transfected with the reporter gene aequorin, and expressing human VPAC(1), VPAC(2), chimeric VPAC(1)/VPAC(2), or mutated receptors. The VIP-induced [Ca(2+)](i) increase was linearly correlated with receptor density and was higher in cells expressing VPAC(1) receptors than in cells expressing a similar VPAC(2) receptor density. The study was performed to establish the receptor sequence responsible for that difference. VPAC(1)/VPAC(2) chimeric receptors were first used for a broad positioning: those having the third intracellular loop (IC(3)) of the VPAC(1) or of the VPAC(2) receptor behaved, in that respect, phenotypically like VPAC(1) and VPAC(2) receptor, respectively. Replacement in the VPAC(2) receptor of the sequence 315-318 (VGGN) within the IC(3) by its VPAC(1) receptor counterpart 328-331 (IRKS) and the introduction of VGGN in state of IRKS in VPAC(1) was sufficient to mimic the VPAC(1) and VPAC(2) receptor characteristics, respectively. Thus, a small sequence in the IC(3) of the VPAC(1) receptor, probably through interaction with G(alphai) and G(alphaq) proteins, is responsible for the efficient agonist-stimulated [Ca(2+)](i) increase.
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Affiliation(s)
- Ingrid Langer
- Department of Biological Chemistry and Nutrition, Faculty of Medicine, Université Libre de Bruxelles, B-1070 Brussels, Belgium.
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48
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Klinger M, Freissmuth M, Nanoff C. Adenosine receptors: G protein-mediated signalling and the role of accessory proteins. Cell Signal 2002; 14:99-108. [PMID: 11781133 DOI: 10.1016/s0898-6568(01)00235-2] [Citation(s) in RCA: 212] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ever since the discovery of the effects of adenosine in the circulation, adenosine receptors continue to represent a promising drug target. Firstly, this is due to the fact that the receptors are expressed in a large variety of cells; in particular, the actions of adenosine (or, respectively, of the antagonistic methylxanthines) in the central nervous system, in the circulation, on immune cells and on other tissues can be beneficial in certain disorders. Secondly, there exists a large number of ligands, which have been generated by introducing several modifications in the structure of the lead compounds (adenosine and methylxanthine), some of them highly specific. Four adenosine receptor subtypes have been identified by molecular cloning; they belong to the family of G protein-coupled receptors, which transfer signals by activating heterotrimeric G proteins. It has been appreciated recently that accessory proteins impinge on the receptor/G protein interaction and thus modulate the signalling reaction. These accessory components may be thought as adaptors that redirect the signalling pathway to elicit a cell-specific response. Here, we review the recent literature on adenosine receptors and place a focus on the role of accessory proteins in the organisation of adenosine receptor signalling. These components have been involved in receptor sorting, in the control of signal amplification and in the temporal regulation of receptor activity, while the existence of others is postulated on the basis of atypical cellular reactions elicited by receptor activation.
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Affiliation(s)
- Markus Klinger
- Institute of Pharmacology, University of Vienna, Währinger Strasse 13a, Vienna A-1090, Austria
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49
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Fredholm BB, Arslan G, Halldner L, Kull B, Schulte G, Ådén U, Svenningsson P. Adenosine receptor signaling in vitro and in vivo. Drug Dev Res 2001. [DOI: 10.1002/ddr.1124] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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50
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Cunha RA. Adenosine as a neuromodulator and as a homeostatic regulator in the nervous system: different roles, different sources and different receptors. Neurochem Int 2001; 38:107-25. [PMID: 11137880 DOI: 10.1016/s0197-0186(00)00034-6] [Citation(s) in RCA: 462] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Adenosine exerts two parallel modulatory roles in the CNS, acting as a homeostatic modulator and also as a neuromodulator at the synaptic level. We will present evidence to suggest that these two different modulatory roles are fulfilled by extracellular adenosine originated from different metabolic sources, and involve receptors with different sub-cellular localisation. It is widely accepted that adenosine is an inhibitory modulator in the CNS, a notion that stems from the preponderant role of inhibitory adenosine A(1) receptors in defining the homeostatic modulatory role of adenosine. However, we will review recent data that suggests that the synaptically localised neuromodulatory role of adenosine depend on a balanced activation of inhibitory A(1) receptors and mostly facilitatory A(2A) receptors. This balanced activation of A(1) and A(2A) adenosine receptors depends not only on the transient levels of extracellular adenosine, but also on the direct interaction between A(1) and A(2A) receptors, which control each other's action.
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Affiliation(s)
- R A Cunha
- Laboratory of Neurosciences, Faculty of Medicine, University of Lisbon, Portugal.
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