1
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Pfeil EM, Brands J, Merten N, Vögtle T, Vescovo M, Rick U, Albrecht IM, Heycke N, Kawakami K, Ono Y, Ngako Kadji FM, Hiratsuka S, Aoki J, Häberlein F, Matthey M, Garg J, Hennen S, Jobin ML, Seier K, Calebiro D, Pfeifer A, Heinemann A, Wenzel D, König GM, Nieswandt B, Fleischmann BK, Inoue A, Simon K, Kostenis E. Heterotrimeric G Protein Subunit Gαq Is a Master Switch for Gβγ-Mediated Calcium Mobilization by Gi-Coupled GPCRs. Mol Cell 2020; 80:940-954.e6. [PMID: 33202251 DOI: 10.1016/j.molcel.2020.10.027] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/21/2020] [Accepted: 10/16/2020] [Indexed: 12/18/2022]
Abstract
Mechanisms that control mobilization of cytosolic calcium [Ca2+]i are key for regulation of numerous eukaryotic cell functions. One such paradigmatic mechanism involves activation of phospholipase Cβ (PLCβ) enzymes by G protein βγ subunits from activated Gαi-Gβγ heterotrimers. Here, we report identification of a master switch to enable this control for PLCβ enzymes in living cells. We find that the Gαi-Gβγ-PLCβ-Ca2+ signaling module is entirely dependent on the presence of active Gαq. If Gαq is pharmacologically inhibited or genetically ablated, Gβγ can bind to PLCβ but does not elicit Ca2+ signals. Removal of an auto-inhibitory linker that occludes the active site of the enzyme is required and sufficient to empower "stand-alone control" of PLCβ by Gβγ. This dependence of Gi-Gβγ-Ca2+ on Gαq places an entire signaling branch of G-protein-coupled receptors (GPCRs) under hierarchical control of Gq and changes our understanding of how Gi-GPCRs trigger [Ca2+]i via PLCβ enzymes.
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Affiliation(s)
- Eva Marie Pfeil
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Julian Brands
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Nicole Merten
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Timo Vögtle
- Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center, University of Würzburg, 97080 Würzburg, Germany
| | - Maddalena Vescovo
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ulrike Rick
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ina-Maria Albrecht
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Nina Heycke
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Yuki Ono
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | | | - Suzune Hiratsuka
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Junken Aoki
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Felix Häberlein
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Michaela Matthey
- Department of Systems Physiology, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany; Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Jaspal Garg
- Institute of Pharmacology and Toxicology, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
| | - Stephanie Hennen
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Marie-Lise Jobin
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany
| | - Kerstin Seier
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany
| | - Davide Calebiro
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany; Institute of Metabolism and Systems Research and Centre of Membrane Proteins and Receptors, University of Birmingham, B15 2TT Birmingham, UK
| | - Alexander Pfeifer
- Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Akos Heinemann
- Division of Pharmacology, Otto-Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz, 8010 Graz, Austria
| | - Daniela Wenzel
- Department of Systems Physiology, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany; Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Gabriele M König
- Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Bernhard Nieswandt
- Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center, University of Würzburg, 97080 Würzburg, Germany
| | - Bernd K Fleischmann
- Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Asuka Inoue
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Katharina Simon
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
| | - Evi Kostenis
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
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2
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Kazemi MH, Raoofi Mohseni S, Hojjat-Farsangi M, Anvari E, Ghalamfarsa G, Mohammadi H, Jadidi-Niaragh F. Adenosine and adenosine receptors in the immunopathogenesis and treatment of cancer. J Cell Physiol 2017; 233:2032-2057. [DOI: 10.1002/jcp.25873] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Accepted: 02/21/2017] [Indexed: 12/18/2022]
Affiliation(s)
- Mohammad H. Kazemi
- Student Research Committee, Department of Immunology, School of Medicine; Iran University of Medical Sciences (IUMS); Tehran Iran
- Immunology Research Center; Tabriz University of Medical Sciences; Tabriz Iran
| | - Sahar Raoofi Mohseni
- Department of Immunology, School of Public Health; Tehran University of Medical Sciences; Tehran Iran
| | - Mohammad Hojjat-Farsangi
- Department of Oncology-Pathology, Immune and Gene Therapy Lab, Cancer Center Karolinska (CCK); Karolinska University Hospital Solna and Karolinska Institute; Stockholm Sweden
- Department of Immunology, School of Medicine; Bushehr University of Medical Sciences; Bushehr Iran
| | - Enayat Anvari
- Faculty of Medicine, Department of Physiology; Ilam University of Medical Sciences; Ilam Iran
| | - Ghasem Ghalamfarsa
- Medicinal Plants Research Center; Yasuj University of Medical Sciences; Yasuj Iran
| | - Hamed Mohammadi
- Immunology Research Center; Tabriz University of Medical Sciences; Tabriz Iran
- Faculty of Medicine, Department of Immunology; Tabriz University of Medical Sciences; Tabriz Iran
| | - Farhad Jadidi-Niaragh
- Immunology Research Center; Tabriz University of Medical Sciences; Tabriz Iran
- Department of Immunology, School of Public Health; Tehran University of Medical Sciences; Tehran Iran
- Faculty of Medicine, Department of Immunology; Tabriz University of Medical Sciences; Tabriz Iran
- Drug Applied Research Center; Tabriz University of Medical Sciences; Tabriz Iran
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3
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Erb L, Weisman GA. Coupling of P2Y receptors to G proteins and other signaling pathways. ACTA ACUST UNITED AC 2012; 1:789-803. [PMID: 25774333 DOI: 10.1002/wmts.62] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
P2Y receptors are G protein-coupled receptors (GPCRs) that are activated by adenine and uridine nucleotides and nucleotide sugars. There are eight subtypes of P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and P2Y14), which activate intracellular signaling cascades to regulate a variety of cellular processes, including proliferation, differentiation, phagocytosis, secretion, nociception, cell adhesion, and cell migration. These signaling cascades operate mainly by the sequential activation or deactivation of heterotrimeric and monomeric G proteins, phospholipases, adenylyl and guanylyl cyclases, protein kinases, and phosphodiesterases. In addition, there are numerous ion channels, cell adhesion molecules, and receptor tyrosine kinases that are modulated by P2Y receptors and operate to transmit an extracellular signal to an intracellular response.
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Affiliation(s)
- Laurie Erb
- Department of Biochemistry, Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA
| | - Gary A Weisman
- Department of Biochemistry, Life Sciences Center, University of Missouri-Columbia, Columbia, MO 65211, USA
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4
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Amber-Cicek F, Ugur O, Sayar K, Ugur M. Cell adhesion modulates 5-HT(1D) and P2Y receptor signal trafficking differentially in LTK-8 cells. Eur J Pharmacol 2008; 590:12-9. [PMID: 18582865 DOI: 10.1016/j.ejphar.2008.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 04/15/2008] [Accepted: 05/13/2008] [Indexed: 12/31/2022]
Abstract
In this study, we investigated adhesion-induced changes in cellular responses to serotonin 5-HT(1D) and purinergic P2Y receptor stimulation. We demonstrated that detachment of LTK-8 cells increased 5-HT(1D) receptor-mediated intracellular Ca(2+) and extracellular signal regulated kinase (ERK) phosphorylation responses without affecting the adenylate cyclase response. Additionally, detachment enabled 5-HT(1D) receptor stimulation to inhibit P2Y receptor-induced [Ca(2+)](i) mobilization. Such a cross talk between the two receptor systems was not observed in attached cells. P2Y receptor-induced Ca(2+) response was insensitive to adhesion state of the cells, while ERK phosphorylation response was enhanced upon detachment. Integrity of the actin cytoskeleton did not appear to play a role in adhesion sensitivity of 5-HT(1D)-mediated responses, as treatment of attached cells with cytochalasin D did not mimic detachment-induced effects. Effects of detachment were reversed immediately after re-attachment of the suspended cells on poly-l-lysine coated cover slips, suggesting that the involvement of integrins or focal adhesion complexes is unlikely. Taken collectively, our results demonstrate that not only cellular responses induced by different G protein-coupled receptors, but also different responses induced by a particular G protein-coupled receptor, can be affected differentially by the adhesion status of cells. This suggests an important role for cell adhesion in controlling the coupling of a single G protein-coupled receptor to different intracellular responses.
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Affiliation(s)
- Figen Amber-Cicek
- Ankara University, Faculty of Medicine, Department of Biophysics, Ankara, Turkey
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5
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Kolachala VL, Bajaj R, Chalasani M, Sitaraman SV. Purinergic receptors in gastrointestinal inflammation. Am J Physiol Gastrointest Liver Physiol 2008; 294:G401-10. [PMID: 18063703 DOI: 10.1152/ajpgi.00454.2007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Purinergic receptors comprise a family of transmembrane receptors that are activated by extracellular nucleosides and nucleotides. The two major classes of purinergic receptors, P1 and P2, are expressed widely in the gastrointestinal tract as well as immune cells. The purinergic receptors serve a variety of functions from acting as neurotransmitters, to autocoid and paracrine signaling, to cell activation and immune response. Nucleosides and nucleotide agonist of purinergic receptors are released by many cell types in response to specific physiological signals, and their levels are increased during inflammation. In the past decade, the advent of genetic knockout mice and the development of highly potent and selective agonists and antagonists for the purinergic receptors have significantly advanced the understanding of purinergic receptor signaling in health and inflammation. In fact, agonist/antagonists of purinergic receptors are emerging as therapeutic modalities to treat intestinal inflammation. In this article, the distribution of the purinergic receptors in the gastrointestinal tract and their physiological and pathophysiological role in intestinal inflammation will be reviewed.
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Affiliation(s)
- Vasantha L Kolachala
- Division of Digestive Diseases, Emory University School of Medicine, Atlanta, GA 30322, USA
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6
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Lahiri S, Mitchell CH, Reigada D, Roy A, Cherniack NS. Purines, the carotid body and respiration. Respir Physiol Neurobiol 2007; 157:123-9. [PMID: 17383945 PMCID: PMC1975770 DOI: 10.1016/j.resp.2007.02.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 02/19/2007] [Accepted: 02/21/2007] [Indexed: 10/23/2022]
Abstract
The carotid body is essential to detecting levels of oxygen in the blood and initiating the compensatory response. Increasing evidence suggests that the purines ATP and adenosine make a key contribution to this signaling by the carotid body. The glomus cells release ATP in response to hypoxia. This released ATP can stimulate P2X receptors on the carotid body to elevate intracellular Ca(2+) and to produce an excitatory response. This released ATP can be dephosphorylated to adenosine by a series of extracellular enzymes, which in turn can stimulate A(1), A(2A) and A(2B) adenosine receptors. Levels of extracellular adenosine can also be altered by membrane transporters. Endogenous adenosine stimulates these receptors to increase the ventilation rate and may modulate the catecholamine release from the carotid sinus nerve. Prolonged hypoxic challenge can alter the expression of purinergic receptors, suggesting a role in the adaptation. This review discusses evidence for a key role of ATP and adenosine in the hypoxic response of the carotid body, and emphasizes areas of new contributions likely to be important in the future.
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Affiliation(s)
- S. Lahiri
- Department of Physiology; University of Pennsylvania School of Medicine, Philadelphia, PA
| | - C. H. Mitchell
- Department of Physiology; University of Pennsylvania School of Medicine, Philadelphia, PA
| | - D. Reigada
- Department of Physiology; University of Pennsylvania School of Medicine, Philadelphia, PA
| | - A. Roy
- Department of Physiology; University of Pennsylvania School of Medicine, Philadelphia, PA
| | - N. S. Cherniack
- Departments of Medicine and Physiology, Case Western Reserve School of Medicine, Cleveland, OH
- Department of Medicine University of Medicine and Dentistry of New Jersey, Newark, NJ
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7
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Abbracchio MP, Burnstock G, Boeynaems JM, Barnard EA, Boyer JL, Kennedy C, Knight GE, Fumagalli M, Gachet C, Jacobson KA, Weisman GA. International Union of Pharmacology LVIII: update on the P2Y G protein-coupled nucleotide receptors: from molecular mechanisms and pathophysiology to therapy. Pharmacol Rev 2006; 58:281-341. [PMID: 16968944 PMCID: PMC3471216 DOI: 10.1124/pr.58.3.3] [Citation(s) in RCA: 979] [Impact Index Per Article: 54.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
There have been many advances in our knowledge about different aspects of P2Y receptor signaling since the last review published by our International Union of Pharmacology subcommittee. More receptor subtypes have been cloned and characterized and most orphan receptors de-orphanized, so that it is now possible to provide a basis for a future subdivision of P2Y receptor subtypes. More is known about the functional elements of the P2Y receptor molecules and the signaling pathways involved, including interactions with ion channels. There have been substantial developments in the design of selective agonists and antagonists to some of the P2Y receptor subtypes. There are new findings about the mechanisms underlying nucleotide release and ectoenzymatic nucleotide breakdown. Interactions between P2Y receptors and receptors to other signaling molecules have been explored as well as P2Y-mediated control of gene transcription. The distribution and roles of P2Y receptor subtypes in many different cell types are better understood and P2Y receptor-related compounds are being explored for therapeutic purposes. These and other advances are discussed in the present review.
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Affiliation(s)
- Maria P Abbracchio
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
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8
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Erb L, Liao Z, Seye CI, Weisman GA. P2 receptors: intracellular signaling. Pflugers Arch 2006; 452:552-62. [PMID: 16586093 DOI: 10.1007/s00424-006-0069-2] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2006] [Accepted: 03/06/2006] [Indexed: 10/24/2022]
Abstract
P2 receptors for extracellular nucleotides are divided into two categories: the ion channel receptors (P2X) and the G-protein-coupled receptors (P2Y). For the P2X receptors, signal transduction appears to be relatively simple. Upon activation by extracellular ATP, a channel comprised of P2X receptor subunits opens and allows cations to move across the plasma membrane, resulting in changes in the electrical potential of the cell that, in turn, propagates a signal. This regulated flux of ions across the plasma membrane has important signaling functions, especially in impulse propagation in the nervous system and in muscle contractility. In addition, P2X receptor activation causes the accumulation of calcium ions in the cytoplasm, which is responsible for activating numerous signaling molecules. For the P2Y receptors, signal transduction is more complex. Intracellular signaling cascades are the main routes of communication between G-protein-coupled receptors and regulatory targets within the cell. These signaling cascades operate mainly by the sequential activation or deactivation of heterotrimeric and monomeric G proteins, phospholipases, protein kinases, adenylyl and guanylyl cyclases, and phosphodiesterases that regulate many cellular processes, including proliferation, differentiation, apoptosis, metabolism, secretion, and cell migration. In addition, there are numerous ion channels, cell adhesion molecules and receptor tyrosine kinases that are modulated by P2Y receptors and operate to transmit an extracellular signal to an intracellular response. These intracellular signaling pathways and their regulation by P2 receptors are discussed in this review.
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Affiliation(s)
- Laurie Erb
- Department of Biochemistry, University of Missouri-Columbia, Life Sciences Center, 1201 Rollins Rd., Columbia, MO 65211, USA.
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9
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Stepanyuk GA, Golz S, Markova SV, Frank LA, Lee J, Vysotski ES. Interchange of aequorin and obelin bioluminescence color is determined by substitution of one active site residue of each photoprotein. FEBS Lett 2005; 579:1008-14. [PMID: 15710383 DOI: 10.1016/j.febslet.2005.01.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2004] [Revised: 01/03/2005] [Accepted: 01/06/2005] [Indexed: 11/20/2022]
Abstract
The bioluminescence spectra from the Ca2+-regulated photoproteins aequorin (lambdamax=469 nm) and obelin (lambdamax=482 nm) differ because aequorin has an H-bond from its Tyr82 to the bound coelenteramide, not present in obelin at the corresponding Phe88. Substitutions of this Phe88 by Tyr, Trp, or His shifted the obelin bioluminescence to shorter wavelength with F88Y having lambdamax=453 nm. Removal of the H-bond by the substitution of Y82F in aequorin shifted its bioluminescence to lambdamax=501 nm. All mutants were stable with good activity and were expressible in mammalian cells, thereby demonstrating potential for monitoring multiple events in cells using multi-color detection.
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Affiliation(s)
- Galina A Stepanyuk
- Photobiology Laboratory, Institute of Biophysics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia
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10
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Chow KBS, Jones RL, Wise H. Agonists can discriminate between cloned human and mouse prostacyclin receptors. Prostaglandins Leukot Essent Fatty Acids 2004; 70:423-9. [PMID: 15062844 DOI: 10.1016/j.plefa.2003.08.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2003] [Accepted: 08/28/2003] [Indexed: 12/19/2022]
Abstract
The ability of prostacyclin analogues to stimulate adenylyl cyclase (AC) and phospholipase C (PLC) in Chinese hamster ovary (CHO) cells expressing cloned human (hIP) or cloned mouse (mIP) prostacyclin receptors has been compared. For hIP, the order of potency (pEC(50)) for stimulating AC and PLC pathways was similar: AFP-07 (9.3, 8.4)>cicaprost (8.3, 6.9), iloprost (7.9, 6.8)>taprostene (7.4, 6.8)>carbacyclin (6.9, 6.6), PGE(1) (6.6, 5.1). Although the standard IP agonists cicaprost and iloprost behaved similarly in both hIP and mIP receptor-expressing cells, carbacyclin and PGE(1) showed significantly higher potency at the mIP receptor, suggesting that the agonist recognition sites on hIP and mIP receptors are not identical. A further distinction between hIP and mIP receptors was found with taprostene, which had greater efficacy at hIP receptors (AC 94%, PLC 14%) than at mIP receptors (AC 77%, PLC 0%) (cicaprost=100% in each assay).
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Affiliation(s)
- K B S Chow
- Department of Pharmacology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
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11
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Yaar R, Jones MR, Chen JF, Ravid K. Animal models for the study of adenosine receptor function. J Cell Physiol 2004; 202:9-20. [PMID: 15389588 DOI: 10.1002/jcp.20138] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Adenosine receptors represent a family of G-protein coupled receptors that are ubiquitously expressed in a wide variety of tissues. This family contains four receptor subtypes: A1 and A3, which mediate inhibition of adenylyl cyclase; and A2a and A2b, which mediate stimulation of this enzyme. Currently, all receptor subtypes have been genetically deleted in mouse models except for the A2b adenosine receptor, and some have been overexpressed in selective tissues of transgenic mice. Studies involving these transgenic mice indicated that receptor levels are rate limiting, as effects were amplified upon increases in receptor level. The knockout models pointed to clusters of activities related to the physiologies of the cardiovascular and the nervous systems, which are either reduced or enhanced upon specific receptor deletion. Interestingly, the trend of effects on these systems is similar in the A1 and A3 adenosine receptor knockout mice and opposite to the effects observed in the A2a adenosine receptor knockout model. This review summarizes in vitro studies on pathways affected by each adenosine receptor, and primarily focuses on the above in vivo models generated to investigate the physiologic role of adenosine receptors. Furthermore, it illustrates the need for multiple adenosine receptor subtype deficiency studies in mice and the deletion of the A2b subtype.
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Affiliation(s)
- R Yaar
- Department of Biochemistry, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, USA
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12
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Werry TD, Wilkinson GF, Willars GB. Mechanisms of cross-talk between G-protein-coupled receptors resulting in enhanced release of intracellular Ca2+. Biochem J 2003; 374:281-96. [PMID: 12790797 PMCID: PMC1223610 DOI: 10.1042/bj20030312] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2003] [Revised: 06/03/2003] [Accepted: 06/05/2003] [Indexed: 12/21/2022]
Abstract
Alteration in [Ca(2+)](i) (the intracellular concentration of Ca(2+)) is a key regulator of many cellular processes. To allow precise regulation of [Ca(2+)](i) and a diversity of signalling by this ion, cells possess many mechanisms by which they are able to control [Ca(2+)](i) both globally and at the subcellular level. Among these are many members of the superfamily of GPCRs (G-protein-coupled receptors), which are characterized by the presence of seven transmembrane domains. Typically, those receptors able to activate PLC (phospholipase C) enzymes cause release of Ca(2+) from intracellular stores and influence Ca(2+) entry across the plasma membrane. It has been well documented that Ca(2+) signalling by one type of GPCR can be influenced by stimulation of a different type of GPCR. Indeed, many studies have demonstrated heterologous desensitization between two different PLC-coupled GPCRs. This is not surprising, given our current understanding of negative-feedback regulation and the likely shared components of the signalling pathway. However, there are also many documented examples of interactions between GPCRs, often coupling preferentially to different signalling pathways, which result in a potentiation of Ca(2+) signalling. Such interactions have important implications for both the control of cell function and the interpretation of in vitro cell-based assays. However, there is currently no single mechanism that adequately accounts for all examples of this type of cross-talk. Indeed, many studies either have not addressed this issue or have been unable to determine the mechanism(s) involved. This review seeks to explore a range of possible mechanisms to convey their potential diversity and to provide a basis for further experimental investigation.
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Affiliation(s)
- Tim D Werry
- Department of Cell Physiology and Pharmacology, Medical Sciences Building, University of Leicester, UK
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13
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Abstract
The tubuloglomerular feedback response, the change in afferent arteriolar tone caused by a change in NaCl concentration at the macula densa, is likely initiated by the generation of a vasoactive mediator within the confines of the juxtaglomerular apparatus. Substantial progress has been made in identifying the nature of this mediator and the factors that modulate its effect on vascular tone. In support of earlier studies using P1 purinergic antagonists, the application of the knockout technique has shown that adenosine 1 receptors are absolutely required for eliciting TGF responses. The background level of angiotensin II appears to be an important cofactor determining the efficiency of A1AR-induced vasoconstriction, probably through a synergistic interaction at the level of the G protein-dependent transduction mechanism. The source of the adenosine is still unclear, but it is conceivable that adenosine is generated extracellularly from released ATP through a cascade of ecto-nucleotidases. There is also evidence that ATP may activate P2 receptors in preglomerular vessels, which may contribute to autoregulation of renal vascular resistance. Nitric oxide (NO), generated by the neuronal isoform of nitric oxide synthase in macula densa cells, reduces the constrictor effect of adenosine, but the regulation of NO release and its exact role in states of TGF-induced hyperfiltration are still unclear.
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Affiliation(s)
- Jürgen Schnermann
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-1370, USA.
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14
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Hill KJ, Webber AC, Hill SJ. A role of protein kinase C mu in signalling from the human adenosine A1 receptor to the nucleus. Br J Pharmacol 2003; 139:721-32. [PMID: 12812995 PMCID: PMC1573890 DOI: 10.1038/sj.bjp.0705294] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2002] [Revised: 02/05/2003] [Accepted: 03/25/2003] [Indexed: 11/09/2022] Open
Abstract
1 Stimulation of adenosine A(1) receptors produced a stimulation of c-fos promoter-regulated gene transcription in Chinese hamster ovary (CHO)-A1 cells expressing the human A(1) receptor. Gene transcription was monitored using a luciferase-based reporter gene (pGL3). 2 This response to the A(1) receptor agonist N(6)-cyclopentyladenosine (CPA) was sensitive to inhibition by pertussis toxin, the MEK-1 inhibitor PD 98059 and by the phosphatidylinositol-3-kinase inhibitors wortmannin and LY 294002. The response was also completely abolished by the protein kinase C (PKC) inhibitor Ro-31-8220. 3 Several isoforms of PKC can be detected in CHO-A1 cells (alpha, delta, epsilon, micro, iota, zeta), but only PKC alpha, PKC delta and PKC were downregulated by prolonged treatment with phorbol ester. The c-fos-regulated luciferase response to A(1) agonists was not, however, inhibited by 24 h pretreatment with the phorbol esters phorbol 12,13-dibutyrate (PDBu). This observation, together with the fact that a significant attenuation (40%) of the c-fos-luciferase response to PDBu and A(1) agonist was produced by low concentrations of the PKC inhibitor Gö 6976 suggests a role for PKC micro. 4 Stimulation of CHO-A1 cells with CPA stimulated the activation of endogenous PKC micro as measured by autophosphorylation. This was rapid, occurred within 1-2 min, but returned to basal levels after 30 min. Furthermore, transient expression of a constitutively active form of PKC micro resulted in a significant increase in c-fos-regulated gene expression. 5 Taken together, these data suggest that PKC micro plays an important role in the ability of the adenosine A(1) receptor to signal to the nucleus.
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Affiliation(s)
- Kathryn J Hill
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, Nottingham NG7 2UH
| | - Anne C Webber
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, Nottingham NG7 2UH
| | - Stephen J Hill
- Institute of Cell Signalling, Medical School, Queen's Medical Centre, Nottingham NG7 2UH
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McCormack K. A New Perspective on Signal Transduction in Neuropathic Pain The Emerging Role of the G Protein By Dimer in Transducing and Modulating Opioid Signaling. Pain 2003. [DOI: 10.1201/9780203911259.ch5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Wise H, Chow KBS, Wing KY, Kobayashi T, Tse DLY, Cheng CHK. Properties of chimeric prostacyclin/prostaglandin D2 receptors: site-directed mutagenesis reveals the significance of the isoleucine residue at position 323. J Recept Signal Transduct Res 2003; 23:83-97. [PMID: 12680591 DOI: 10.1081/rrs-120018762] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Mouse prostacyclin (mIP) receptors transiently expressed in Chinese hamster ovary (CHO) cells activated both adenylyl cyclase and phospholipase C, with a 33-fold preference for signaling through Gs. The prostacyclin (IP) receptor agonists cicaprost, iloprost, carbacyclin, and prostaglandin E1 showed a similar order of potency for activation of both signaling pathways in cells transiently transfected with the mIP and the chimeric prostacyclin/prostaglandin D2 (IPN-VII/DPC and IPN-V/DPVI-C) receptors. Substitution of the carboxyl-terminal tail of the prostacyclin receptor with the corresponding region of the mDP receptor (IPN-VII/DPC) produced a receptor with increased coupling to both Gs and Gq. However, this increased G-protein coupling was lost in the IPN-V/DPVI-C receptor. The observation that both these chimeric receptors can activate phospholipase C indicates that the carboxyl-terminal tail of the IP receptor is not entirely responsible for its ability to couple to Gq. Site-directed mutagenesis studies suggest that isoleucine at position 323 in the IPN-VII/DPC receptor plays an important role in mediating the increased potency of this chimeric receptor.
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Affiliation(s)
- Helen Wise
- Department of Pharmacology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
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Fong AY, Krstew EV, Barden J, Lawrence AJ. Immunoreactive localisation of P2Y1 receptors within the rat and human nodose ganglia and rat brainstem: comparison with [alpha 33P]deoxyadenosine 5'-triphosphate autoradiography. Neuroscience 2002; 113:809-23. [PMID: 12182888 DOI: 10.1016/s0306-4522(02)00237-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The present study employed standard peroxidase immunohistochemistry to map the distribution of P2Y(1) receptors in the rat brainstem and nodose ganglia and characterised the binding profile of [alpha(33)P]dATP. Binding of [alpha(33)P]dATP was fully displaceable by adenosine 5'-triphosphate (ATP), and was found on both human and rat nodose ganglia, and throughout the rat brainstem, including the nucleus tractus solitarius and ventrolateral medulla. [Alpha(33)P]dATP binding in the human nodose ganglia was significantly displaced by both 2-methylthio ATP and alpha,beta-methylene ATP, but not by uridine 5'-triphosphate, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid, 8,8'-(carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino))bis(1,3,5-naphtalenetrisulfonic) acid (NF279) or N-ethylcarboxamidoadenosine. [Alpha(33)P]dATP binding in the rat nodose ganglia and brainstem was significantly displaced by only 2-methylthio ATP, suggesting that [alpha(33)P]dATP is binding to P2Y receptors in the rat. Binding of [alpha(33)P]dATP was also significantly displaced by alpha,beta-methylene adenosine 5'-diphosphate, suggesting a component of the binding is to endogenous ecto-5'-nucleotidase, however, almost all binding could be displaced by a combination of receptor agonists (2-methylthio ATP, uridine 5'-triphosphate and alpha,beta-methylene ATP), suggesting preferential binding to receptors. Immunoreactivity to P2Y(1) receptor (P2Y(1)-IR) exhibited similar distribution patterns to [alpha(33)P]dATP binding, with a clear topographic profile. Particularly dense P2Y(1)-IR labeling was evident in cells and fibres of the dorsal vagal complex. Immunolabeling was also present in the dorsal motor nucleus of the vagus and nucleus ambiguus, indicating the possibility of P2Y(1) receptors on vagal efferents. Unilateral vagal ligation was also performed to examine the transport of P2Y(1) receptor, using both immunohistochemistry and [alpha(33)P]dATP autoradiography. Accumulations of both P2Y(1)-IR and [alpha(33)P]dATP binding were apparent adjacent to both ligatures, suggesting bi-directional transport of P2Y(1) receptors along the rat vagus nerve. This current study represents the first description of P2Y(1) receptor distribution within the rodent brainstem and nodose ganglion and also characterises [alpha(33)P]dATP binding to P2Y receptors.
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Affiliation(s)
- A Y Fong
- Department of Pharmacology, P.O. Box 13E, Monash University, Wellington Road, Clayton, Vic 3800, Australia
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18
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Godwin SL, Soltoff SP. Calcium-sensing receptor-mediated activation of phospholipase C-gamma1 is downstream of phospholipase C-beta and protein kinase C in MC3T3-E1 osteoblasts. Bone 2002; 30:559-66. [PMID: 11934646 DOI: 10.1016/s8756-3282(01)00700-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Elevated extracellular calcium (Ca(e)) stimulates both chemotaxis and mitogenesis of MC3T3-E1 osteoblasts via a calcium-sensing receptor (CasR). Ca(e)-mediated chemotaxis of these bone-forming cells is dependent on phospholipase C (PLC) and blocked by the Gi-protein inhibitor pertussis toxin. In this study, we examine the signaling mechanisms by which the CasR stimulates PLC activity in MC3T3-E1 osteoblasts. We found that elevated Ca(e) stimulated PLC-gamma1 tyrosine phosphorylation in a time-dependent and Ca(e)-concentration-dependent manner. The maximal increase in PLC-gamma1 tyrosine phosphorylation was observed 3-5 min after increasing Ca(e) by 3.2 mmol/L from 1.8 mmol/L. Elevated Ca(e) also promoted a rapid increase in both inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], a second messenger formed by PLC-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate, and cytosolic free calcium ([Ca+2]i). The kinetics of the CasR-mediated increases in Ins(1,4,5)P3 and [Ca+2]i and the sensitivity of the Ca(e)-stimulated elevation in [Ca+2]i to U73122 (a PLC inhibitor) together suggest that the osteoblast CasR is coupled via Gq to PLC-beta. U73122 blocked the Ca(e)-promoted, but not PDGF-promoted, PLC-gamma1 tyrosine phosphorylation, suggesting that the activation of PLC-beta is upstream of PLC-gamma1 activation. Inhibition of protein kinase C (PKC) disrupted Ca(e)-stimulated tyrosine phosphorylation of PLC-gamma1. In addition, exposure to pertussis toxin or exogenous activation of protein kinase A (PKA) inhibited PLC-gamma1 tyrosine phosphorylation in response to Ca(e). The results indicate that: (a) the osteoblast CasR activates PLC-gamma1 downstream of PLC-beta in a PKC-dependent manner; (b) PKA is a negative regulator of Ca(e)-promoted PLC-gamma1 phosphorylation; and (c) Gq and Gi are both involved in the CasR-mediated phosphorylation of PLC-gamma1.
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Affiliation(s)
- S L Godwin
- Department of Orthodontics, University of Connecticut Health Center, Farmington, CT 06030, USA.
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19
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Werry TD, Christie MI, Dainty IA, Wilkinson GF, Willars GB. Ca(2+) signalling by recombinant human CXCR2 chemokine receptors is potentiated by P2Y nucleotide receptors in HEK cells. Br J Pharmacol 2002; 135:1199-208. [PMID: 11877327 PMCID: PMC1573230 DOI: 10.1038/sj.bjp.0704566] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Human embryonic kidney (HEK)-293 cells expressing recombinant G alpha(i)-coupled, human CXC chemokine receptor 2 (CXCR2) were used to study the elevation of the intracellular [Ca(2+)] ([Ca(2+)](i)) in response to interleukin-8 (IL-8) following pre-stimulation of endogenously expressed P2Y1 or P2Y2 nucleotide receptors. 2. Pre-stimulation of cells with adenosine 5'-triphosphate (ATP) revealed a substantial Ca(2+) signalling component mediated by IL-8 (E(max)=83 +/- 8% of maximal ATP response, pEC(50) of IL-8 response=9.7 +/- 0.1). 3. 1 microM 2-methylthioadenosine 5'-diphosphate (2MeSADP; P2Y1 selective) and 100 microM uridine 5'-triphosphate (UTP; P2Y2 selective) stimulated equivalent maximal increases in [Ca(2+)](i) elevation. However, UTP caused a sustained elevation, whilst following 2MeSADP [Ca(2+)](i) rapidly returned to basal levels. 4. Both UTP and 2MeSADP increased the potency and magnitude of IL-8-mediated [Ca(2+)](i) elevation but the effects of UTP (E(max) of IL-8 response increased to 50 +/- 1% of the maximal response to ATP, pEC(50) increased to 9.8 +/- 0.1) were greater than those of 2MeSADP (E(max) increased to 36 +/- 2%, pEC(50) increased to 8.7 +/- 0.2). 5. 5. The potentiation of IL-8-mediated Ca(2+) signalling by UTP was not dependent upon the time of IL-8 addition following UTP but was dependent on the continued presence of UTP. Potentiated IL-8 Ca(2+) signalling was apparent in the absence of extracellular Ca(2+), demonstrating the release of Ca(2+) from intracellular stores. 6. Activation of P2Y1 and P2Y2 receptors also revealed Ca(2+) signalling by an endogenously expressed, G alpha(s)-coupled beta-adrenoceptor. 7. In conclusion, pre-stimulation of P2Y nucleotide receptors, particularly P2Y2, facilitates Ca(2+) signalling by either recombinant CXCR2 or endogenous beta-adrenoceptors.
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Affiliation(s)
- Tim D Werry
- Department of Cell Physiology and Pharmacology, Maurice Shock Medical Sciences Building, University Road, Leicester, LE1 9HN, UK.
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20
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Chow KB, Wong YH, Wise H. Prostacyclin receptor-independent inhibition of phospholipase C activity by non-prostanoid prostacyclin mimetics. Br J Pharmacol 2001; 134:1375-84. [PMID: 11724742 PMCID: PMC1573079 DOI: 10.1038/sj.bjp.0704388] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Chinese hamster ovary (CHO) cells were transiently transfected with the mouse prostacyclin (mIP) receptor to examine IP agonist-mediated stimulation of [(3)H]-cyclic AMP and [(3)H]-inositol phosphate production. 2. The prostacyclin analogues, cicaprost, iloprost, carbacyclin and prostaglandin E(1), stimulated adenylyl cyclase activity with EC(50) values of 5, 6, 25 and 95 nM, respectively. These IP agonists also stimulated the phospholipase C pathway with 10 - 40 fold lower potency than stimulation of adenylyl cyclase. 3. The non-prostanoid prostacyclin mimetics, octimibate, BMY 42393 and BMY 45778, also stimulated adenylyl cyclase activity, with EC(50) values of 219, 166 and 398 nM, respectively, but failed to stimulate [(3)H]-inositol phosphate production. 4. Octimibate, BMY 42393 and BMY 45778 inhibited iloprost-stimulated [(3)H]-inositol phosphate production in a non-competitive manner. 5. Activation of the endogenously-expressed P(2) purinergic receptor by ATP led to an increase in [(3)H]-inositol phosphate production which was inhibited by the non-prostanoid prostacyclin mimetics in non-transfected CHO cells. Prostacyclin analogues and other prostanoid receptor ligands failed to inhibit ATP-stimulated [(3)H]-inositol phosphate production. 6. A comparison between the IP receptor-specific non-prostanoid ONO-1310 and the structurally-related EP(3) receptor-specific agonist ONO-AP-324, indicated that the inhibitory effect of non-prostanoids was specific for those compounds known to activate IP receptors. 7. The non-prostanoid prostacyclin mimetics also inhibited phospholipase C activity when stimulated by constitutively-active mutant Galpha(q)RC, Galpha(14)RC and Galpha(16)QL transiently expressed in CHO cells. These drugs did not inhibit adenylyl cyclase activity when stimulated by the constitutively-active mutant Galpha(s)QL. 8. These results suggest that non-prostanoid prostacyclin mimetics can specifically inhibit [(3)H]-inositol phosphate production by targeting G(q/11) and/or phospholipase C in CHO cells, and that this effect is independent of IP receptors.
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Affiliation(s)
- K B Chow
- Department of Pharmacology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong S.A.R., China
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21
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Abstract
Agonist stimulation of adenosine A(1) receptors has been consistently shown to result in reduction of brain damage following experimentally induced global and focal brain ischaemia in animals. Unsurprisingly, the use of adenosine A(1) receptors as targets for the development of clinical therapeutics suitable for treatment of ischaemic brain disorders has been suggested by many authors. The latest studies of adenosine and its receptors indicate that adenosine-mediated actions might be far more complex than originally anticipated, casting some doubt about the rapid development of stroke treatment based on adenosine. This review discusses the possible role of adenosine receptor subtypes (A(1), A(2) and A(3)) in the context of their potential as therapeutics in stroke.
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Affiliation(s)
- D K von Lubitz
- Emergency Medicine Research Laboratories, Department of Emergency Medicine, University of Michigan Medical Center, TC/B1354/0303, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-0303, USA.
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Cordeaux Y, Briddon SJ, Megson AE, McDonnell J, Dickenson JM, Hill SJ. Influence of receptor number on functional responses elicited by agonists acting at the human adenosine A(1) receptor: evidence for signaling pathway-dependent changes in agonist potency and relative intrinsic activity. Mol Pharmacol 2000; 58:1075-84. [PMID: 11040056 DOI: 10.1124/mol.58.5.1075] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of A(1) adenosine receptors leads to the inhibition of cAMP accumulation and the stimulation of inositol phosphate accumulation via pertussis toxin-sensitive G-proteins. In this study we have investigated the signaling of the A(1) adenosine receptor in Chinese hamster ovary (CHO) cells, when expressed at approximately 203 fmol/mg (CHOA1L) and at approximately 3350 fmol/mg (CHOA1H). In CHOA1L cells, the agonists N(6)-cyclopentyladenosine (CPA), (R)-N(6)-(2-phenylisopropyl)adenosine, and 5'-(N-ethylcarboxamido)adenosine (NECA) inhibited cAMP production in a concentration-dependent manner. After pertussis toxin treatment, the agonist NECA produced a stimulation of cAMP production, whereas CPA and (R)-N(6)-(2-phenylisopropyl)adenosine were ineffective. In CHOAIH cells, however, all three agonists produced both an inhibition of adenylyl cyclase and a pertussis toxin-insensitive stimulation of adenylyl cyclase. All three agonists were more potent at inhibiting adenylyl cyclase in CHOA1H cells than in CHOA1L cells. In contrast, A(1) agonists (and particularly NECA) were less potent at stimulating inositol phosphate accumulation in CHOA1H cells than in CHOA1L cells. After pertussis toxin treatment, agonist-stimulated inositol phosphate accumulation was reduced in CHOA1H cells and abolished in CHOA1L cells. The relative intrinsic activity of NECA in stimulating inositol phosphate accumulation, compared to CPA (100%), was much greater in the presence of pertussis toxin (289.6%) than in the absence of pertussis toxin (155.2%). These data suggest that A(1) adenosine receptors can couple to both pertussis toxin-sensitive and -insensitive G-proteins in an expression level-dependent manner. These data also suggest that the ability of this receptor to activate different G-proteins is dependent on the agonist present.
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Affiliation(s)
- Y Cordeaux
- Institute of Cell Signalling and School of Biomedical Sciences, Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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23
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Morales B, Barrera N, Uribe P, Mora C, Villalón M. Functional cross talk after activation of P2 and P1 receptors in oviductal ciliated cells. Am J Physiol Cell Physiol 2000; 279:C658-69. [PMID: 10942716 DOI: 10.1152/ajpcell.2000.279.3.c658] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The presence of ATP and adenosine receptors and their role in controlling ciliary activity in oviductal ciliated cells was studied by measuring the ciliary beat frequency (CBF) in oviductal tissue cultures. ATP, adenosine, and related compounds increased the CBF in a dose-dependent manner. We established that P2 receptors of subtype 2Y(2) and P1 receptors of subtype A(2a) mediated the responses to ATP and adenosine, respectively. We found evidence to suggest that stimulation of ciliary activity by ATP requires D-myo-inositol 1,4, 5-trisphosphate [Ins(1,4,5)P(3)] metabolism, intracellular Ca(2+) mobilization, and protein kinase C activation. On the other hand, the adenosine effect is mediated by activation of a G(s) protein-dependent pathway that enhances cAMP intracellular levels. To study the interaction between P2 and P1 receptors, cells were stimulated simultaneously with both agonists. We observed a synergistic increase of the CBF even at agonist concentrations (100 nM) that did not produce a significant response when added separately to the culture. Furthermore, a blocker of the cAMP pathway produced a reduction of the ATP response, whereas a blocker of the Ins(1,4,5)P(3) pathway also produced an inhibition of the adenosine response. Our evidence demonstrates that both ATP and adenosine receptors are present in a single ciliated cell and that a mechanism of cross talk could operate in the transduction pathways to control ciliary activity.
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Affiliation(s)
- B Morales
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
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24
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Abstract
Numerous studies have consistently shown that agonist stimulation of adenosine A1 receptors results in a significant reduction of morbidity and mortality associated with global and focal brain ischemia in animals. Based on these observations, several authors have suggested utilization of adenosine A1 receptors as targets for the development of clinically viable drugs against ischemic brain disorders. Recent advent of adenosine A1 receptor agonists characterized by lowered cardiovascular effects added additional strength to this argument. On the other hand, although cardioprotective, adenosine A3 receptor agonists proved severely cerebrodestructive when administered prior to global ischemia in gerbils. Moreover, stimulation of adenosine A3 receptors appears to reduce the efficacy of some of the neuroprotective actions mediated by adenosine A1 receptors. The review discusses the possible role of adenosine receptor subtypes (A1, A2, and A3) in the context of their involvement in the pathology of cerebral ischemia, and analyzes putative strategies for the development of clinically useful strategies based on adenosine and its receptors. It also stresses the need for further experimental studies before definitive conclusions on the usefulness of the adenosine concept in the treatment of brain ischemia can be made.
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Affiliation(s)
- D K von Lubitz
- Department of Emergency Medicine, University of Michigan Medical Center, Ann Arbor 48109-0303, USA.
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25
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Abstract
Numerous studies have consistently shown that agonist stimulation of adenosine A1 receptors results in a significant reduction of morbidity and mortality associated with global and focal brain ischemia in animals. Based on these observations, several authors have suggested utilization of adenosine A1 receptors as targets for the development of clinically viable drugs against ischemic brain disorders. Recent advent of adenosine A1 receptor agonists characterized by lowered cardiovascular effects added additional strength to this argument. On the other hand, although cardioprotective, adenosine A3 receptor agonists proved severely cerebrodestructive when administered prior to global ischemia in gerbils. Moreover, stimulation of adenosine A3 receptors appears to reduce the efficacy of some of the neuroprotective actions mediated by adenosine A receptors. The review discusses the possible role of adenosine receptor subtypes (A1, A2, and A3) in the context of their involvement in the pathology of cerebral ischemia, and analyzes putative strategies for the development of clinically useful strategies based on adenosine and its receptors. It also stresses the need for further experimental studies before definitive conclusions on the usefulness of the adenosine concept in the treatment of brain ischemia can be made.
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Affiliation(s)
- D K Von Lubitz
- Department of Emergency Medicine, University of Michigan Medical Center, Ann Arbor 48109-0303, USA.
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26
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Dickenson JM, Hill SJ. Potentiation of adenosine A1 receptor-mediated inositol phospholipid hydrolysis by tyrosine kinase inhibitors in CHO cells. Br J Pharmacol 1998; 125:1049-57. [PMID: 9846644 PMCID: PMC1565676 DOI: 10.1038/sj.bjp.0702170] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The effect of protein tyrosine kinase inhibitors on human adenosine A1 receptor-mediated [3H]-inositol phosphate ([3H]-IP) accumulation has been studied in transfected Chinese hamster ovary cells (CHO-A1) cells. 2. In agreement with our previous studies the selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) stimulated the accumulation of [3H]-IPs in CHO-A1 cells. Pre-treatment with the broad spectrum tyrosine kinase inhibitor genistein (100 microM; 30 min) potentiated the responses elicited by 1 microM (199+/-17% of control CPA response) and 10 microM CPA (234+/-15%). Similarly, tyrphostin A47 (100 microM) potentiated the accumulation of [3H]-IPs elicited by 1 microM CPA (280+/-32%). 3. Genistein (EC50 = 13.7+/-1.2 microM) and tyrphostin A47 (EC50 = 10.4+/-3.9 microM) potentiated the [3H]-IP response to 1 microM CPA in a concentration-dependent manner. 4. Pre-incubation with the inactive analogues of genistein and tyrphostin A47, daidzein (100 microM; 30 min) and tyrphostin A1 (100 microM; 30 min), respectively, had no significant effect on the accumulation of [3H]-IPs elicited by 1 microM CPA. 5. Genistein (100 microM) had no significant effect on the accumulation of [3H]-IPs produced by the endogenous thrombin receptor (1 u ml(-1); 100+/-10% of control response). In contrast, tyrphostin A47 produced a small augmentation of the thrombin [3H]-IP response (148+/-13%). 6. Genistein (100 microM) had no effect on the [3H]-IP response produced by activation of the endogenous Gq-protein coupled CCK(A) receptor with the sulphated C-terminal octapeptide of cholecystokinin (1 microM CCK-8; 96+/-6% of control). In contrast, tyrphostin A47 (100 microM) caused a small but significant increase in the response to 1 microM CCK-8 (113+/-3% of control). 7. The phosphatidylinositol 3-kinase inhibitor LY 294002 (30 microM) and the MAP kinase kinase inhibitor PD 98059 (50 microM) had no significant effect on the [3H]-IP responses produced by 1 microM CPA and 1 microM CCK-8. 8. These observations suggest that a tyrosine kinase-dependent pathway may be involved in the regulation of human adenosine A1 receptor mediated [3H]-IP responses in CHO-A1 cells.
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Affiliation(s)
- J M Dickenson
- Institute of Cell Signalling and School of Biomedical Sciences, Queen's Medical Centre, Nottingham
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Dickenson JM, Hill SJ. Involvement of G-protein betagamma subunits in coupling the adenosine A1 receptor to phospholipase C in transfected CHO cells. Eur J Pharmacol 1998; 355:85-93. [PMID: 9754942 DOI: 10.1016/s0014-2999(98)00468-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In transfected Chinese hamster ovary (CHO-A1) cells the human adenosine A1 receptor directly stimulates pertussis toxin-sensitive increases in inositol phosphate production and potentiates (synergistically) the inositol phosphate responses mediated by Gq-coupled P2Y2 purinoceptor and CCK(A) receptors. In the present study we have investigated the role of Gbetagamma subunits in mediating adenosine A1 receptor effects on phospholipase C activation (both direct and synergistic) by transiently transfecting CHO-A1 cells with a scavenger of Gbetagamma subunits: the C-terminus of beta-adrenoceptor kinase 1 (beta ark1 residues 495-689). [3H]inositol phosphate responses to the selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA; 1 microM) were inhibited (41 +/- 1%) in CHO-A1 cells transiently transfected with the Gbetagamma scavenger, beta ark1 (495-689). Expression of beta ark1 (495-689) protein was confirmed by Western blotting. In contrast, adenosine A1 receptor-mediated inhibition of forskolin stimulated [3H]cyclic AMP accumulation was unaffected by transient expression of beta ark1 (495-689). Beta ark1 (495-689) expression had no significant effect on the [3H]inositol phosphate responses produced by activation of the endogenous P2Y2 purinoceptor (100 microM UTP; 92 +/- 0.8% of control). [3H]inositol phosphate accumulation in response to adenosine A receptor activation was also attenuated in CHO-K1 cells co-transfected with the beta ark1 (495-689) minigene (59 +/- 4% inhibition of control response to 1 microM CPA). Finally, transient expression of beta ark1 (495-689) in CHO-A1 cells inhibited the augmentation of [3H]inositol phosphate responses resulting from co-activation of adenosine A1 receptors and P2Y2 purinoceptors. These experiments indicate that Gbetagamma subunits are involved in the direct coupling the adenosine A1 receptor to phospholipase C and that they also participate in the augmentation of P2Y2 purinoceptor-mediated [3H]inositol phosphate responses by the adenosine A1 receptor.
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Affiliation(s)
- J M Dickenson
- Institute of Cell Signalling, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, UK
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28
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Dickenson JM, Blank JL, Hill SJ. Human adenosine A1 receptor and P2Y2-purinoceptor-mediated activation of the mitogen-activated protein kinase cascade in transfected CHO cells. Br J Pharmacol 1998; 124:1491-9. [PMID: 9723963 PMCID: PMC1565535 DOI: 10.1038/sj.bjp.0701977] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The mitogen-activated protein (MAP) kinase signalling pathway can be activated by a variety of heterotrimeric Gi/Go protein-coupled and Gq/G11 protein-coupled receptors. The aims of the current study were: (i) to investigate whether the Gi/Go protein-coupled adenosine A1 receptor activates the MAP kinase pathway in transfected Chinese hamster ovary cells (CHO-A1) and (ii) to determine whether adenosine A1 receptor activation would modulate the MAP kinase response elicited by the endogenous P2Y2 purinoceptor. 2. The selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) stimulated time and concentration-dependent increases in MAP kinase activity in CHO-A1 cells (EC50 7.1+/-0.4 nM). CPA-mediated increases in MAP kinase activity were blocked by PD 98059 (50 microM; 89+/-4% inhibition), an inhibitor of MAP kinase kinase 1 (MEKI) activation, and by pre-treating cells with pertussis toxin (to block Gi/Go-dependent pathways). 3. Adenosine A1 receptor-mediated activation of MAP kinase was abolished by pre-treatment with the protein tyrosine inhibitor, genistein (100 microM; 6+/-10% of control). In contrast, daidzein (100 microM), the inactive analogue of genistein had no significant effect (96+/-12 of control). MAP kinase responses to CPA (1 microM) were also sensitive to the phosphatidylinositol 3-kinase inhibitors wortmannin (100 nM; 55+/-8% inhibition) and LY 294002 (30 microM; 40+/-5% inhibition) but not to the protein kinase C (PKC) inhibitor Ro 31-8220 (10 microM). 4. Activation of the endogenous P2Y2 purinoceptor with UTP also stimulated time and concentration-dependent increases in MAP kinase activity in CHO-A1 cells (EC50=1.6+/-0.3 microM). The MAP kinase response to UTP was partially blocked by pertussis toxin (67+/-3% inhibition) and by the PKC inhibitor Ro 31-8220 (10 microm; 45+/-5% inhibition), indicating the possible involvement of both Gi/Go protein and Gq protein-dependent pathways in the overall response to UTP. 5. CPA and UTP stimulated concentration-dependent increases in the phosphorylation state of the 42 kDa and 44 kDa forms of MAP kinase as demonstrated by Western blotting. 6. Co-activation of CHO-A1 cells with CPA (10 nM) and UTP (1 microM) produced synergistic increases in MAP kinase activity which were not blocked by the PKC inhibitor Ro 31-8220 (10 microM). 7. Adenosine A1 and P2Y2 purinoceptor activation increased the expression of luciferase in CHO cells transfected with a luciferase reporter gene containing the c-fos promoter. However, co-activating these two receptors produced only additive increases in luciferase expression. 8. In conclusion, our studies have shown that the transfected adenosine A1 receptor and the endogenous P2Y2 purinoceptor couple to the MAP kinase signalling pathway in CHO-A1 cells. Furthermore, co-stimulation of the adenosine A1 receptor and the P2Y2 purinoceptor produced synergistic increases in MAP kinase activity but not c-fos mediated luciferase expression.
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Affiliation(s)
- J M Dickenson
- Institute of Cell Signalling and School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre
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Dickenson JM, Hill SJ. Human 5-HT1B receptor stimulated inositol phospholipid hydrolysis in CHO cells: synergy with Gq-coupled receptors. Eur J Pharmacol 1998; 348:279-85. [PMID: 9652344 DOI: 10.1016/s0014-2999(98)00148-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We have previously reported that the transfected Gi/Go protein-coupled human adenosine A1 receptor (expressed at 200 fmol/mg of protein) and the endogenous 5-HT1B receptor (not detectable using radioligand binding) suppress forskolin-stimulated cyclic AMP accumulation and stimulate increases in [Ca2+]i in Chinese hamster ovary cells (CHO). In addition, co-activation of the adenosine A1 receptor (but not the 5-HT1B receptor) potentiates the hydrolysis of inositol phospholipids elicited by receptors coupled to Gq-proteins (Dickenson and Hill, 1996. Eur. J. Pharmacol. 320, 141-151). In order to establish whether this difference in ability to modulate Gq-coupled receptor responses is a consequence of low 5-HT1B receptor density, we have stably transfected CHO-KI cells with the human 5-HT1Dbeta cDNA (the human homologue of the rodent 5-HT1B receptor). We initially isolated a clonal cell line (designated CHO5-HT1B cells) displaying moderate specific [3H]5-HT binding (pKd of 8.17+/-0.07 and a Bmax of 140 fmol/mg protein). In CHO5-HT1B cells, the selective human 5-HT1B/1D receptor agonist sumatriptan produced a concentration-dependent inhibition of forskolin-stimulated cyclic AMP accumulation (pEC50=7.92+/-0.04). Sumatriptan also elicited a moderate and pertussis toxin-sensitive increase in [3H]inositol phosphate formation in CHO-5HT1B cells (pEC50=6.51+/-0.05). Finally, sumatriptan synergistically enhanced P2U purinoceptor stimulated [3H]inositol phosphate accumulation through a pertussis toxin-sensitive mechanism. These findings clearly show the significance of 5-HT1B receptor expression level in determining whether 5-HT1B receptor activation can modulate the accumulation of [3H]inositol phosphates elicited by a Gq-protein coupled receptor. The observation that 5-HT1B receptor activation can potentiate Gq-coupled receptor stimulated second messenger responses may have an important physiological role in the regulation of vascular smooth muscle contraction.
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Affiliation(s)
- J M Dickenson
- Institute of Cell Signalling, School of Biomedical Sciences, Queen's Medical Centre, Nottingham, UK
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Selbie LA, Hill SJ. G protein-coupled-receptor cross-talk: the fine-tuning of multiple receptor-signalling pathways. Trends Pharmacol Sci 1998; 19:87-93. [PMID: 9584624 DOI: 10.1016/s0165-6147(97)01166-8] [Citation(s) in RCA: 236] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Signalling via the large family of G protein-coupled receptors (GPCRs) can lead to many cellular responses, ranging from regulation of intracellular levels of cAMP to stimulation of gene transcription. Members of this receptor family have been grouped into different categories dependent on the particular G protein subtypes that they predominantly interact with. Thus, receptors that couple to GS proteins will stimulate adenylate cyclase in many cells, while Gq/11-coupled receptors can mobilize intracellular Ca2+ via activation of phospholipase C. There is accumulating evidence, however, that activation of one particular signalling pathway by a GPCR can amplify intracellular signalling within a parallel but separate pathway. In this article Lisa Selbie and Stephen Hill review some of the evidence for these synergistic interactions and suggest that they may have an important role in finetuning signals from multiple receptor signalling pathways.
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Affiliation(s)
- L A Selbie
- Institute of Cell Signalling, University of Nottingham, Queen's Medical Centre, Medical School, UK
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Marsh KA, Draper LM, Rubin PC, Hill SJ. Receptor-stimulated phospholipase C activity in human umbilical artery cultured endothelial cells grown in a low oxygen environment. Biochem Pharmacol 1997; 54:1351-9. [PMID: 9393678 DOI: 10.1016/s0006-2952(97)00324-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Endothelial cells of the human umbilical blood vessels are widely cultured in an oxygen tension (21%) far above that in which they exist in vivo (3%). This study investigates the effect of the long term culture (ca. 1 month) of human umbilical artery endothelial cells in a reduced oxygen environment (3%: HUAEC3) in comparison to cells grown in a 'normoxic' environment (21%: HUAEC21). Despite reports of altered metabolic pathways and reduced membrane integrity in other cell types, the characteristics of HUAEC3 were found to be similar to those of HUAEC21 with respect to morphology, immunocytochemical profile and in vitro growth rates. Cellular glutathione was maintained in these cells although ATP levels in HUAEC3 were found to be significantly lower than those observed in HUAEC21. The phosphoinositide responses of the HUAEC3 to a variety of agonists were also found to be of similar magnitude to those observed in HUAEC21. In addition, the pharmacological characteristics of the phospholipase C-linked histamine H1 and P2y2 (P2U) receptors were not changed by culture of cells in a low oxygen environment.
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Affiliation(s)
- K A Marsh
- Department of Physiology & Pharmacology, Queen's Medical Centre, Nottingham, UK
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Selbie LA, King NV, Dickenson JM, Hill SJ. Role of G-protein beta gamma subunits in the augmentation of P2Y2 (P2U)receptor-stimulated responses by neuropeptide Y Y1 Gi/o-coupled receptors. Biochem J 1997; 328 ( Pt 1):153-8. [PMID: 9359846 PMCID: PMC1218899 DOI: 10.1042/bj3280153] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Neuropeptide Y (NPY) significantly potentiates the constrictor actions of noradrenaline and ATP on blood vessels via a pertussis toxin (PTX)-sensitive mechanism involving Gi/o (alpha beta gamma) protein subunits (Gi/o, GTP-binding proteins sensitive to PTX). In Chinese hamster ovary K1 (CHO K1) cells expressing specific receptors for these neurotransmitters, stimulation of Gi/o protein-coupled receptors for NPY and other neurotransmitters can augment the Gq/11-coupled (Gq/11, GTP-binding proteins insensitive to PTX) alpha 1B adrenoceptor- or ATP receptor-induced arachidonic acid (AA) release and inositol phosphate (IP) production (early events which may precede vasoconstriction). In this study, we have assessed the role of G beta gamma subunits in the synergistic interaction between Gi/o- (NPY Y1, 5-hydroxytryptamine 5-HT1B, adenosine A1) and Gq/11- [ATP P2Y2 (P2U)]-coupled receptors on AA release by using the specific abilities of regions of the beta-adrenergic receptor kinase (beta ARK1 residues 495-689) and the transducin alpha subunit to associate with G-protein beta gamma subunit dimers and to act as G beta gamma subunit scavengers. Transient expression of beta ARK1(495-689) in CHO K1 cells heterologously expressing NPY Y1 receptors had no significant effect on the PTX-insensitive ability of ATP to stimulate AA release. Stimulation of NPY Y1 receptors (as well as the endogenous 5-hydroxytryptamine 5-HT1B receptor and the transiently expressed human adenosine A1 receptor) resulted in a PTX-sensitive augmentation of ATP-stimulated AA release, which was inhibited by expression of both G beta gamma subunit scavengers. Expression of beta ARK1(495-689) similarly inhibited NPY Y1 receptor augmentation of ATP-stimulated IP production (a measure of phospholipase C activity), a step thought to precede the NPY Y1 receptor-augmented protein kinase C-dependent AA release previously observed in these cells. These experiments demonstrate that G beta gamma subunits, as inhibited by two different G beta gamma scavengers, significantly contribute to the synergistic interaction between NPY Y1 Gi/o- and Gq/11-coupled receptor activity, and are required for the augmentation of IP production and AA release observed in this model cell system.
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Affiliation(s)
- L A Selbie
- Department of Physiology and Pharmacology, Queen's Medical Centre, University of Nottingham, U.K
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Dickenson JM, Hill SJ. Transfected adenosine A1 receptor-mediated modulation of thrombin-stimulated phospholipase C and phospholipase A2 activity in CHO cells. Eur J Pharmacol 1997; 321:77-86. [PMID: 9083789 DOI: 10.1016/s0014-2999(96)00917-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Thrombin receptor activation in Chinese hamster ovary (CHO) cells stimulates the hydrolysis of inositol phospholipids and the release of arachidonic acid. Our previous studies have shown that activation of the human transfected adenosine A1 receptor in CHO cells (CHO-A1) potentiates the accumulation of inositol phosphates elicited by endogenous P2U purinoceptors and CCKA receptors. In this study we have investigated whether adenosine A1 receptor activation can modulate thrombin-stimulated arachidonic acid release and/or inositol phospholipid hydrolysis in CHO-A1 cells. Thrombin stimulated [3H]arachidonic acid release and total [3H]inositol phosphate accumulation in CHO-A1 cells. Both these responses to thrombin were were insensitive to pertussis toxin. The protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), potentiated thrombin-stimulated [3H]arachidonic acid. In marked contrast, PMA inhibited thrombin-stimulated [3H]inositol phosphate accumulation. The selective protein kinase C inhibitor Ro 31-8220 (3-¿1-[3-(2-isothioureido)propyl] indol-3-yl¿-4-(1-methylindol-3-yl)-3-pyrrolin-2,5-dione) had no effect on thrombin-stimulated [3H]arachidonic acid release but reversed the potentiation of thrombin-stimulated [3H]arachidonic acid release elicited by PMA. The selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) augmented the release of [3H]arachidonic acid produced by thrombin. Co-activation of the adenosine A1 receptor also potentiated thrombin-stimulated [3H]inositol phosphate accumulation. The synergistic interactions between the adenosine A1 receptor and thrombin were abolished in pertussis-toxin-treated cells. The potentiation of [3H]arachidonic acid release by CPA was blocked by the protein kinase C inhibitors Ro 31-8220 and GF 109203X (3-[1-[3-(dimethylamino)propyl]-1 H-indol-3-yl]-4-(1 H-indol-3-yl)- 1H-pyrrole-2,5-dione). In conclusion, thrombin receptor activation in CHO-A1 cells stimulates the accumulation of [3H]inositol phosphates and the release of [3H]arachidonic acid through pertussis-toxin-insensitive G-proteins. Experiments using PMA suggest that protein kinase C differentially regulates thrombin receptor activation of phospholipase C and phospholipase A2. Co-activation of the transfected human adenosine A1 receptor augments thrombin-stimulated phospholipase C and phospholipase A2 activity. Finally, the augmentation of phospholipase A2 activity by the adenosine A1 receptor is inhibited by selective protein kinase C inhibitors, suggesting the involvement of protein kinase C.
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Affiliation(s)
- J M Dickenson
- Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, UK. mqzjmd@mqn 1.phpharm.nottingham.ac.uk
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Spence S, Rena G, Sullivan M, Erdogan S, Houslay MD. Receptor-mediated stimulation of lipid signalling pathways in CHO cells elicits the rapid transient induction of the PDE1B isoform of Ca2+/calmodulin-stimulated cAMP phosphodiesterase. Biochem J 1997; 321 ( Pt 1):157-63. [PMID: 9003415 PMCID: PMC1218050 DOI: 10.1042/bj3210157] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chinese hamster ovary cells (CHO cells) do not exhibit any Ca2+/calmodulin-stimulated cAMP phosphodiesterase (PDE1) activity. Challenge of CHO cells with agonists for endogenous P2-purinoceptors, lysophosphatidic acid receptors and thrombin receptors caused a similar rapid transient induction of PDE1 activity in each instance. This was also evident on noradrenaline challenge of a cloned CHO cell line transfected so as to overexpress alpha 1B-adrenoceptors. This novel PDE1 activity appeared within about 15 min of exposure to ligands, rose to a maximum value within 30 min to 1 h and then rapidly decreased. In each case, the expression of novel PDE1 activity was blocked by the transcriptional inhibitor actinomycin D. Challenge with insulin of either native CHO cells or a CHO cell line transfected so as to overexpress the human insulin receptor failed to induce PDE1 activity. Reverse transcriptase-PCR analyses, using degenerate primers able to detect the PDE1C isoform, did not amplify any fragment from RNA preparations of CHO cells expressing PDE1 activity, although they did so from the human thyroid carcinoma FTC133 cell line. Reverse transcriptase-PCR analyses, using degenerate primers able to detect the PDE1A and PDE1B isoforms, successfully amplified a fragment of the predicted size from RNA preparations of both CHO cells expressing PDE1 activity and human Jurkat T-cells. Sequencing of the PCR products, generated using the PDE1A/B primers, yielded a novel sequence which, by analogy with sequences reported for bovine and murine PDE1B forms, suggests that the PDE1 species induced in CHO cells through protein kinase C activation and that expressed in Jurkat T-cells are PDE1B forms.
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Affiliation(s)
- S Spence
- Division of Biochemistry and Molecular Biology, University of Glasgow, Scotland, U.K
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Communications. Br J Pharmacol 1996. [DOI: 10.1111/j.1476-5381.1996.tb17246.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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ORAL COMMUNICATIONS. Br J Pharmacol 1996. [DOI: 10.1111/j.1476-5381.1996.tb17243.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Dickenson JM, Hill SJ. Coupling of an endogenous 5-HT1B-like receptor to increases in intracellular calcium through a pertussis toxin-sensitive mechanism in CHO-K1 cells. Br J Pharmacol 1995; 116:2889-96. [PMID: 8680721 PMCID: PMC1909226 DOI: 10.1111/j.1476-5381.1995.tb15941.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
1. Chinese hamster ovary cells (CHO-K1) express an endogenous 5-hydroxytryptamine (5-HT)1B-like receptor that is negatively coupled to adenylyl cyclase through a pertussis toxin (PTX)-sensitive mechanism. Furthermore, the human adenosine A1 receptor when expressed in CHO-K1 cells (CHO-A1) has been shown to mobilize intracellular Ca2+ through a PTX-sensitive mechanism. Therefore the aim of this investigation was to determine whether the endogenous 5-HT1B-like receptor was able to stimulate increases in intracellular free [Ca2+] ([Ca2+]i) in CHO-A1 cells. 2. In agreement with previous studies using CHO cells, 5-hydroxytryptamine (5-HT) elicited a concentration-dependent inhibition of forskolin-stimulated [3H]-cyclic AMP production in CHO-A1 cells (p[EC50] = 7.73 +/- 0.13). 5-HT (1 microM) inhibited 47 +/- 5% of the [3H]-cyclic AMP accumulation induced by 3 microM forskolin. Forskolin stimulated [3H]-cyclic AMP accumulation was also inhibited by the 5-HT1 receptor agonists (p[EC50] values) 5-carboxyamidotryptamine (5-CT; 8.07 +/- 0.08), RU 24969 (8.12 +/- 0.33) and sumatriptan (5.80 +/- 0.31). 3. 5-HT elicited a concentration-dependent increase in [Ca2+]i in CHO-A1 cells (p[EC50] = 8.07 +/- 0.05). In the presence of 2 mM extracellular Ca2+, 5-HT (1 microM) increased [Ca2+]i from 174 +/- 17 nM to 376 +/- 22 nM. The 5-HT1 receptor agonists (p[EC50] values), 5-carboxyamidotryptamine (5-CT; 7.9 +/- 0.02), RU 24969 (8.1 +/- 0.07) and sumatriptan (5.9 +/- 0.11) all elicited concentration-dependent increases in [Ca2+]i. Similar maximal increases in [Ca2+]i were obtained with each agonist. The selective 5-HT1A receptor agonist, 8-OH-DPAT (10 microM) did not stimulate increases in [Ca2+]i. 5-HT (100 microM) and 5-CT (10 microM) did not stimulate a measurable increase in [3H]-inositol phosphate accumulation in CHO-A1 cells. 4. 5-HT (1 microM)-mediated increases in [Ca2+]i were insensitive to the 5-HT receptor antagonist, ritanserin (5-HT2; 100 nM), ketanserin (5-HT2; 100 nM), LY-278,584 (5-HT3; 1 microM) and WAY 100635 (5-HT1A; 1 microM). The response to 5-HT (100 nM) was antagonized by the non-selective 5-HT1 antagonist, methiothepin (pKb = 8.90 +/- 0.09) and the 5-HT1D antagonist GR 127935 (pKb = 10.44 +/- 0.06). 5. Pretreatment with PTX (200 ng ml-1 for 4 h) completely attenuated the Ca2+ response to 100 microM 5-HT. 6. In untransfected CHO-K1 cells, 5-HT (1 microM), RU 24969 (1 microM), and 5-CT (1 microM) elicited increases in [Ca2+]i similar to those observed in CHO-A1 cells. 7. These data demonstrate that in CHO-K1 cells the endogenously expressed 5-HT1B-like receptor couples to the phospholipase C/Ca2+ signalling pathway through a PTX-sensitive pathway, suggesting the involvement of Gi/Go protein(s).
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Affiliation(s)
- J M Dickenson
- Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham
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Peakman MC, Hill SJ. Adenosine A1 receptor-mediated changes in basal and histamine-stimulated levels of intracellular calcium in primary rat astrocytes. Br J Pharmacol 1995; 115:801-10. [PMID: 8548180 PMCID: PMC1908518 DOI: 10.1111/j.1476-5381.1995.tb15004.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
1. The effects of adenosine A1 receptor stimulation on basal and histamine-stimulated levels of intracellular free calcium ion concentration ([Ca2+]i) have been investigated in primary astrocyte cultures derived from neonatal rat forebrains. 2. Histamine (0.1 microM-1 mM) caused rapid, concentration-dependent increases in [Ca2+]i over basal levels in single type-2 astrocytes in the presence of extracellular calcium. A maximum mean increase of 1,468 +/- 94 nM over basal levels was recorded in 90% of type-2 cells treated with 1 mM histamine (n = 49). The percentage of type-2 cells exhibiting calcium increases in response to histamine appeared to vary in a concentration-dependent manner. However, the application of 1 mM histamine to type-1 astrocytes had less effect, eliciting a mean increase in [Ca2+]i of 805 +/- 197 nM over basal levels in only 30% of the cells observed (n = 24). 3. In the presence of extracellular calcium, the A1 receptor-selective agonist, N6-cyclopentyladenosine (CPA, 10 microM), caused a maximum mean increase in [Ca2+]i of 1,110 +/- 181 nM over basal levels in 30% of type-2 astrocytes observed (n = 53). The size of this response was concentration-dependent; however, the percentage of type-2 cells exhibiting calcium increases in response to CPA did not appear to vary in a concentration-dependent manner. A mean calcium increase of 605 +/- 89 nM over basal levels was also recorded in 23% of type-1 astrocytes treated with 10 microM CPA (n = 30). 4. In the absence of extracellular calcium, in medium containing 0.1 mM EGTA, a mean increase in [Ca2+]i of 504 +/- 67 nM over basal levels was recorded in 41% of type-2 astrocytes observed (n = 41) after stimulation with 1 microM CPA. However, in the presence of extracellular calcium, pretreatment with the A1 receptor-selective antagonist, 8-cyclopentyl-1,3-dipropylxanthine, for 5-10 min before stimulation with 1 microM CPA, completely antagonized the response in 100% of the cells observed. 5. In type-2 astrocytes, prestimulation with 10 nM CPA significantly increased the size of the calcium response produced by 0.1 microM histamine and the percentage of responding cells. Treatment with 0.1 microM histamine alone caused a mean calcium increase of 268 +/- 34 nM in 41% of the cells observed (n = 34). After treatment with 10 nM CPA, mean calcium increase of 543 +/- 97 nM was recorded in 100% of the cells observed (n = 33). 6. These data indicate that adenosine Al receptors couple to intracellular calcium mobilization and extracellular calcium influx in type-1 and type-2 astrocytes in primary culture. In addition, the simultaneous activation of adenosine Al receptors on type-2 astrocytes results in an augmentation of the calcium response to histamine H1 receptor stimulation.
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Affiliation(s)
- M C Peakman
- Department of Physiology & Pharmacology, Medical School, Queen's Medical Centre, Nottingham
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