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Singh S, Sarroza D, English A, Whittington D, Dong A, Malamas M, Makriyannis A, van der Stelt M, Li Y, Zweifel L, Bruchas MR, Land BB, Stella N. P2X 7 receptor-dependent increase in endocannabinoid 2-arachidonoyl glycerol production by neuronal cells in culture: Dynamics and mechanism. Br J Pharmacol 2024; 181:2459-2477. [PMID: 38581262 DOI: 10.1111/bph.16348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 01/12/2024] [Accepted: 02/01/2024] [Indexed: 04/08/2024] Open
Abstract
BACKGROUND AND PURPOSE Neurotransmission and neuroinflammation are controlled by local increases in both extracellular ATP and the endocannabinoid 2-arachidonoyl glycerol (2-AG). While it is known that extracellular ATP stimulates 2-AG production in cells in culture, the dynamics and molecular mechanisms that underlie this response remain poorly understood. Detection of real-time changes in eCB levels with the genetically encoded sensor, GRABeCB2.0, can address this shortfall. EXPERIMENTAL APPROACH 2-AG and arachidonoylethanolamide (AEA) levels in Neuro2a (N2a) cells were measured by LC-MS, and GRABeCB2.0 fluorescence changes were detected using live-cell confocal microscopy and a 96-well fluorescence plate reader. KEY RESULTS 2-AG and AEA increased GRABeCB2.0 fluorescence in N2a cells with EC50 values of 81 and 58 nM, respectively; both responses were reduced by the cannabinoid receptor type 1 (CB1R) antagonist SR141617 and absent in cells expressing the mutant-GRABeCB2.0. ATP increased only 2-AG levels in N2a cells, as measured by LC-MS, and induced a transient increase in the GRABeCB2.0 signal within minutes primarily via activation of P2X7 receptors (P2X7R). This response was dependent on diacylglycerol lipase β activity, partially dependent on extracellular calcium and phospholipase C activity, but not controlled by the 2-AG hydrolysing enzyme, α/β-hydrolase domain containing 6 (ABHD6). CONCLUSIONS AND IMPLICATIONS Considering that P2X7R activation increases 2-AG levels within minutes, our results show how these molecular components are mechanistically linked. The specific molecular components in these signalling systems represent potential therapeutic targets for the treatment of neurological diseases, such as chronic pain, that involve dysregulated neurotransmission and neuroinflammation.
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Affiliation(s)
- Simar Singh
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
| | - Dennis Sarroza
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
| | - Anthony English
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
| | - Dale Whittington
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, USA
| | - Ao Dong
- Peking University School of Life Sciences, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Michael Malamas
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Alexandros Makriyannis
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts, USA
| | | | - Yulong Li
- Peking University School of Life Sciences, PKU-IDG/McGovern Institute for Brain Research, Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Larry Zweifel
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
- Center for Cannabis Research, University of Washington, Seattle, Washington, USA
- Center for the Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, Washington, USA
| | - Michael R Bruchas
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Center for Cannabis Research, University of Washington, Seattle, Washington, USA
- Center for the Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, Washington, USA
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, Washington, USA
| | - Benjamin B Land
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Center for Cannabis Research, University of Washington, Seattle, Washington, USA
- Center for the Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, Washington, USA
| | - Nephi Stella
- Department of Pharmacology, University of Washington, Seattle, Washington, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington, USA
- Center for Cannabis Research, University of Washington, Seattle, Washington, USA
- Center for the Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, Washington, USA
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Wong J, Gu BJ, Teoh H, Krupa M, Monif M, Slee M, Wiley JS. Flow Cytometry Identifies an Early Stage of Platelet Apoptosis Produced by Agonists of the P2X1 and P2X7 Receptors. Platelets 2022; 33:621-631. [PMID: 35042433 DOI: 10.1080/09537104.2021.1981844] [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] [Indexed: 01/08/2023]
Abstract
Platelets express P2X1 receptors and our data also show the expression of P2X7 receptors. We studied the role of both receptors in platelet apoptosis by incubation of PRP with P2X agonists, then centrifuged to remove viable platelets, and analyzed the supernatant by flow cytometry to identify a sparse platelet-derived population that stained with MitoTracker dyes and CD41. BzATP, a potent agonist of P2X receptors, and ABT737, an activator of intrinsic apoptosis, produced altered platelets that stained moderately for annexin V and corresponded to an early stage apoptotic platelet (ESAP). Over a range of BzATP concentrations, we observed a dose-dependent formation of ESAPs between 5 and 500 uM BzATP, together with a variable formation of ESAPs at nanomolar ATP or BzATP (50-200 nM). Production of ESAPs occurred with αβ-meATP, while responses with either BzATP or αβ-meATP showed desensitization at a higher agonist concentration. Formation of ESAPs by either 100 nM or 0.5 mM BzATP was inhibited by preincubation of platelets with latrunculin A, an inhibitor of the actin cytoskeleton that prevents apoptosis. ESAP production was totally inhibited by preincubation of platelets with methyl-beta-cyclodextrin, which removes cholesterol from lipid rafts. Our data show that both P2X1 and P2X7 receptors are localized in platelet lipid rafts where P2X-agonists act to produce early stage apoptotic platelets.
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Affiliation(s)
- Joelyn Wong
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Ben J Gu
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Harry Teoh
- College of Medicine and Public Health, Flinders University of South Australia, Bedford Park, Australia
| | - Malgorzata Krupa
- College of Medicine and Public Health, Flinders University of South Australia, Bedford Park, Australia
| | - Mastura Monif
- Department of Neurology, Royal Melbourne Hospital, Parkville, Australia.,Department of Neuroscience, Monash University, Clayton, Australia
| | - Mark Slee
- College of Medicine and Public Health, Flinders University of South Australia, Bedford Park, Australia
| | - James S Wiley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia.,Haematology Department, Box Hill Hospital, Australia
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Abstract
The P2X7 receptor has been proposed as a novel drug target for different types of diseases associated with inflammation, including brain diseases, peripheral inflammation, and cancers. Structurally diverse P2X7 receptor antagonists, mainly negative allosteric modulators (NAMs), have been developed in recent years, and several P2X7 receptor antagonists are currently evaluated in clinical trials. The P2X7 receptor requires high micro- to even millimolar ATP concentrations to be activated. Selective agonists for the P2X7 receptor are not available. Positive allosteric modulators (PAMs) have been described, but PAMs with high potency and selectivity are still lacking. This chapter discusses medicinal chemistry approaches toward the development of P2X7 receptor modulators and presents a selection of recommended tool compounds for studying P2X7 receptors in humans and rodents.
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Affiliation(s)
- Christa E Müller
- Pharmaceutical & Medicinal Chemistry, PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Bonn, Germany.
| | - Vigneshwaran Namasivayam
- Pharmaceutical & Medicinal Chemistry, PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Bonn, Germany
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4
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Collado-Díaz V, Martinez-Cuesta MÁ, Blanch-Ruiz MA, Sánchez-López A, García-Martínez P, Peris JE, Usach I, Ivorra MD, Lacetera A, Martín-Santamaría S, Esplugues JV, Alvarez A. Abacavir Increases Purinergic P2X7 Receptor Activation by ATP: Does a Pro-inflammatory Synergism Underlie Its Cardiovascular Toxicity? Front Pharmacol 2021; 12:613449. [PMID: 33867979 PMCID: PMC8045785 DOI: 10.3389/fphar.2021.613449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/15/2021] [Indexed: 11/15/2022] Open
Abstract
The cardiovascular toxicity of Abacavir is related to its purinergic structure. Purinergic P2X7-receptors (P2X7R), characterized by activation by high concentrations of ATP and with high plasticity, seem implicated. We appraise the nature of the interplay between Abacavir and P2X7R in generating vascular inflammation. The effects of Abacavir on leukocyte-endothelium interactions were compared with those of its metabolite carbovir triphosphate (CBV-TP) or ATP in the presence of apyrase (ATP-ase) or A804598 (P2X7R-antagonist). CBV-TP and ATP levels were evaluated by HPLC, while binding of Abacavir, CBV-TP and ATP to P2X7R was assessed by radioligand and docking studies. Hypersensitivity studies explored a potential allosteric action of Abacavir. Clinical concentrations of Abacavir (20 µmol/L) induced leukocyte-endothelial cell interactions by specifically activating P2X7R, but the drug did not show affinity for the P2X7R ATP-binding site (site 1). CBV-TP levels were undetectable in Abacavir-treated cells, while those of ATP were unaltered. The effects of Abacavir were Apyrase-dependent, implying dependence on endogenous ATP. Exogenous ATP induced a profile of proinflammatory actions similar to Abacavir, but was not entirely P2X7R-dependent. Docking calculations suggested ATP-binding to sites 1 and 2, and Abacavir-binding only to allosteric site 2. A combination of concentrations of Abacavir (1 µmol/L) and ATP (0.1 µmol/L) that had no effect when administered separately induced leukocyte-endothelium interactions mediated by P2X7R and involving Connexin43 channels. Therefore, Abacavir acts as a positive allosteric modulator of P2X7R, turning low concentrations of endogenous ATP themselves incapable of stimulating P2X7R into a functional proinflammatory agonist of the receptor.
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Affiliation(s)
- Víctor Collado-Díaz
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain
| | - Maria Ángeles Martinez-Cuesta
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.,CIBERehd, Valencia, Spain
| | | | - Ainhoa Sánchez-López
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain
| | | | - José E Peris
- Departamento de Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Valencia, Valencia, Spain
| | - Iris Usach
- Departamento de Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Valencia, Valencia, Spain
| | - Maria Dolores Ivorra
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain
| | - Alessandra Lacetera
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Sonsoles Martín-Santamaría
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Juan V Esplugues
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.,CIBERehd, Valencia, Spain.,FISABIO- Fundación Hospital Universitario Dr. Peset, Valencia, Spain
| | - Angeles Alvarez
- Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.,CIBERehd, Valencia, Spain
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Martínez-Cuesta MÁ, Blanch-Ruiz MA, Ortega-Luna R, Sánchez-López A, Álvarez Á. Structural and Functional Basis for Understanding the Biological Significance of P2X7 Receptor. Int J Mol Sci 2020; 21:ijms21228454. [PMID: 33182829 PMCID: PMC7696479 DOI: 10.3390/ijms21228454] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 11/04/2020] [Accepted: 11/06/2020] [Indexed: 12/11/2022] Open
Abstract
The P2X7 receptor (P2X7R) possesses a unique structure associated to an as yet not fully understood mechanism of action that facilitates cell permeability to large ionic molecules through the receptor itself and/or nearby membrane proteins. High extracellular adenosine triphosphate (ATP) levels—inexistent in physiological conditions—are required for the receptor to be triggered and contribute to its role in cell damage signaling. The inconsistent data on its activation pathways and the few studies performed in natively expressed human P2X7R have led us to review the structure, activation pathways, and specific cellular location of P2X7R in order to analyze its biological relevance. The ATP-gated P2X7R is a homo-trimeric receptor channel that is occasionally hetero-trimeric and highly polymorphic, with at least nine human splice variants. It is localized predominantly in the cellular membrane and has a characteristic plasticity due to an extended C-termini, which confers it the capacity of interacting with membrane structural compounds and/or intracellular signaling messengers to mediate flexible transduction pathways. Diverse drugs and a few endogenous molecules have been highlighted as extracellular allosteric modulators of P2X7R. Therefore, studies in human cells that constitutively express P2X7R need to investigate the precise endogenous mediator located nearby the activation/modulation domains of the receptor. Such research could help us understand the possible physiological ATP-mediated P2X7R homeostasis signaling.
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Affiliation(s)
- María Ángeles Martínez-Cuesta
- Departamento de Farmacología, Facultad de Medicina y Odontología, Universidad de Valencia, 46010 Valencia, Spain; (M.A.B.-R.); (R.O.-L.); (A.S.-L.)
- CIBERehd, Valencia, Spain
- Correspondence: (M.Á.M.-C.); (Á.Á.); Tel.: +34-963983716 (M.Á.M.-C.); +34-963864898 (Á.Á.)
| | - María Amparo Blanch-Ruiz
- Departamento de Farmacología, Facultad de Medicina y Odontología, Universidad de Valencia, 46010 Valencia, Spain; (M.A.B.-R.); (R.O.-L.); (A.S.-L.)
| | - Raquel Ortega-Luna
- Departamento de Farmacología, Facultad de Medicina y Odontología, Universidad de Valencia, 46010 Valencia, Spain; (M.A.B.-R.); (R.O.-L.); (A.S.-L.)
| | - Ainhoa Sánchez-López
- Departamento de Farmacología, Facultad de Medicina y Odontología, Universidad de Valencia, 46010 Valencia, Spain; (M.A.B.-R.); (R.O.-L.); (A.S.-L.)
| | - Ángeles Álvarez
- Departamento de Farmacología, Facultad de Medicina y Odontología, Universidad de Valencia, 46010 Valencia, Spain; (M.A.B.-R.); (R.O.-L.); (A.S.-L.)
- CIBERehd, Valencia, Spain
- Correspondence: (M.Á.M.-C.); (Á.Á.); Tel.: +34-963983716 (M.Á.M.-C.); +34-963864898 (Á.Á.)
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6
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Lara R, Adinolfi E, Harwood CA, Philpott M, Barden JA, Di Virgilio F, McNulty S. P2X7 in Cancer: From Molecular Mechanisms to Therapeutics. Front Pharmacol 2020; 11:793. [PMID: 32581786 PMCID: PMC7287489 DOI: 10.3389/fphar.2020.00793] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 05/13/2020] [Indexed: 12/18/2022] Open
Abstract
P2X7 is a transmembrane receptor expressed in multiple cell types including neurons, dendritic cells, macrophages, monocytes, B and T cells where it can drive a wide range of physiological responses from pain transduction to immune response. Upon activation by its main ligand, extracellular ATP, P2X7 can form a nonselective channel for cations to enter the cell. Prolonged activation of P2X7, via high levels of extracellular ATP over an extended time period can lead to the formation of a macropore, leading to depolarization of the plasma membrane and ultimately to cell death. Thus, dependent on its activation state, P2X7 can either drive cell survival and proliferation, or induce cell death. In cancer, P2X7 has been shown to have a broad range of functions, including playing key roles in the development and spread of tumor cells. It is therefore unsurprising that P2X7 has been reported to be upregulated in several malignancies. Critically, ATP is present at high extracellular concentrations in the tumor microenvironment (TME) compared to levels observed in normal tissues. These high levels of ATP should present a survival challenge for cancer cells, potentially leading to constitutive receptor activation, prolonged macropore formation and ultimately to cell death. Therefore, to deliver the proven advantages for P2X7 in driving tumor survival and metastatic potential, the P2X7 macropore must be tightly controlled while retaining other functions. Studies have shown that commonly expressed P2X7 splice variants, distinct SNPs and post-translational receptor modifications can impair the capacity of P2X7 to open the macropore. These receptor modifications and potentially others may ultimately protect cancer cells from the negative consequences associated with constitutive activation of P2X7. Significantly, the effects of both P2X7 agonists and antagonists in preclinical tumor models of cancer demonstrate the potential for agents modifying P2X7 function, to provide innovative cancer therapies. This review summarizes recent advances in understanding of the structure and functions of P2X7 and how these impact P2X7 roles in cancer progression. We also review potential therapeutic approaches directed against P2X7.
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Affiliation(s)
- Romain Lara
- Biosceptre (UK) Limited, Cambridge, United Kingdom
| | - Elena Adinolfi
- Department of Medical Sciences, University of Ferrara, Ferrara, Italy
| | - Catherine A Harwood
- Centre for Cell Biology and Cutaneous Research, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Mike Philpott
- Centre for Cutaneous Research, Blizard Institute, Bart's & The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | | | - Francesco Di Virgilio
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, University of Ferrara, Ferrara, Italy
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Zhao TV, Li Y, Liu X, Xia S, Shi P, Li L, Chen Z, Yin C, Eriguchi M, Chen Y, Bernstein EA, Giani JF, Bernstein KE, Shen XZ. ATP release drives heightened immune responses associated with hypertension. Sci Immunol 2020; 4:4/36/eaau6426. [PMID: 31253642 DOI: 10.1126/sciimmunol.aau6426] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 05/30/2019] [Indexed: 12/12/2022]
Abstract
The cause of most hypertensive disease is unclear, but inflammation appears critical in disease progression. However, how elevated blood pressure initiates inflammation is unknown, as are the effects of high blood pressure on innate and adaptive immune responses. We now report that hypertensive mice have increased T cell responses to antigenic challenge and develop more severe T cell-mediated immunopathology. A root cause for this is hypertension-induced erythrocyte adenosine 5'-triphosphate (ATP) release, leading to an increase in plasma ATP levels, which begins soon after the onset of hypertension and stimulates P2X7 receptors on antigen-presenting cells (APCs), increasing APC expression of CD86. Hydrolyzing ATP or blocking the P2X7 receptor eliminated hypertension-induced T cell hyperactivation. In addition, pharmacologic or genetic blockade of P2X7 receptor activity suppressed the progression of hypertension. Consistent with the results in mice, we also found that untreated human hypertensive patients have significantly elevated plasma ATP levels compared with treated hypertensive patients or normotensive controls. Thus, a hypertension-induced increase in extracellular ATP triggers augmented APC and T cell function and contributes to the immune-mediated pathologic changes associated with hypertensive disease.
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Affiliation(s)
- Tuantuan V Zhao
- Department of Physiology and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yu Li
- Department of Physiology and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xiaoli Liu
- Department of Neurology, Zhejiang Hospital, Hangzhou, Zhejiang, China
| | - Shudong Xia
- Department of Cardiology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang, China
| | - Peng Shi
- Department of Cardiology of the Second Affiliated Hospital, and Institute of Translational Medicine, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Li Li
- Department of Pharmacy, Zhejiang Hospital, Hangzhou, Zhejiang, China
| | - Zexin Chen
- Center of Clinical Epidemiology & Biostatistics, Department of Science and Education, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Chunyou Yin
- Department of Physiology and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Masahiro Eriguchi
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA.,Department of Nephrology, Nara Medical University, Kashihara, Nara, Japan
| | - Yayu Chen
- Department of Cardiology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang, China
| | - Ellen A Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Jorge F Giani
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA.,Department of Pathology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Kenneth E Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA.,Department of Pathology, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Xiao Z Shen
- Department of Physiology and Department of Cardiology of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
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8
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Stokes L, Bidula S, Bibič L, Allum E. To Inhibit or Enhance? Is There a Benefit to Positive Allosteric Modulation of P2X Receptors? Front Pharmacol 2020; 11:627. [PMID: 32477120 PMCID: PMC7235284 DOI: 10.3389/fphar.2020.00627] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/21/2020] [Indexed: 12/15/2022] Open
Abstract
The family of ligand-gated ion channels known as P2X receptors were discovered several decades ago. Since the cloning of the seven P2X receptors (P2X1-P2X7), a huge research effort has elucidated their roles in regulating a range of physiological and pathophysiological processes. Transgenic animals have been influential in understanding which P2X receptors could be new therapeutic targets for disease. Furthermore, understanding how inherited mutations can increase susceptibility to disorders and diseases has advanced this knowledge base. There has been an emphasis on the discovery and development of pharmacological tools to help dissect the individual roles of P2X receptors and the pharmaceutical industry has been involved in pushing forward clinical development of several lead compounds. During the discovery phase, a number of positive allosteric modulators have been described for P2X receptors and these have been useful in assigning physiological roles to receptors. This review will consider the major physiological roles of P2X1-P2X7 and discuss whether enhancement of P2X receptor activity would offer any therapeutic benefit. We will review what is known about identified compounds acting as positive allosteric modulators and the recent identification of drug binding pockets for such modulators.
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Affiliation(s)
- Leanne Stokes
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Stefan Bidula
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Lučka Bibič
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Elizabeth Allum
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
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Chen Z, He L, Li L, Chen L. The P2X7 purinergic receptor: An emerging therapeutic target in cardiovascular diseases. Clin Chim Acta 2018; 479:196-207. [PMID: 29366837 DOI: 10.1016/j.cca.2018.01.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/19/2018] [Accepted: 01/19/2018] [Indexed: 10/24/2022]
Abstract
The P2X7 purinergic receptor, a calcium permeable cationic channel, is activated by extracellular ATP. Most studies show that P2X7 receptor plays an important role in the nervous system diseases, immune response, osteoporosis and cancer. Mounting evidence indicates that P2X7 receptor is also associated with cardiovascular disease. For example, the P2X7 receptor activated by ATP can attenuate myocardial ischemia-reperfusion injury. By contrast, inhibition of P2X7 receptor decreases arrhythmia after myocardial infarction, prolongs cardiac survival after a long term heart transplant, alleviates the dilated cardiomyopathy and the autoimmune myocarditis process. The P2X7 receptor also mitigates vascular diseases including atherosclerosis, hypertension, thrombosis and diabetic retinopathy. This review focuses on the latest research on the role and therapeutic potential of P2X7 receptor in cardiovascular diseases.
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Affiliation(s)
- Zhe Chen
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China
| | - Lu He
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China
| | - Lanfang Li
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China.
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China.
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10
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Murrell-Lagnado RD. Regulation of P2X Purinergic Receptor Signaling by Cholesterol. CURRENT TOPICS IN MEMBRANES 2017; 80:211-232. [PMID: 28863817 DOI: 10.1016/bs.ctm.2017.05.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
P2X receptors are cation-selective channels that are activated by the binding of extracellular ATP. They have a high permeability to Ca2+, Na+, and K+ and are expressed widely throughout the nervous, immune, cardiovascular, skeletal, gastrointestinal, respiratory, and endocrine systems. Seven mammalian subtypes of P2X receptor subunits have been identified, P2X1-7, and those that function as homotrimeric receptors (P2X1, 2, 3, 4, and 7) are targeted to lipid rafts, although they show limited resistance to solubilization by Triton X-100. Recent crystal structures of P2X3 and P2X4 receptors have provided considerable high-resolution information about the architecture of this family of receptors and yet the molecular details of how they are regulated by cholesterol are unknown. Currents mediated by the P2X1-4 receptors are either inhibited or relatively insensitive to cholesterol depletion, but there is no clear evidence to support the direct binding of cholesterol to these receptors. In contrast, the activity of the low-affinity, proinflammatory P2X7 receptor is potentiated by cholesterol depletion and regions within the proximal C-terminus play an important role in coupling changes in cholesterol to the gating of the pore. Based upon our understanding of the lipid signaling events that are triggered downstream of P2X7 receptor activation, a change in the levels of cholesterol may contribute to the sensitization of receptor currents and the dilation of the pore that occurs following prolonged, high-level stimulation. This chapter focuses on the regulation of P2X7 receptor signaling by cholesterol and our current understanding of the mechanisms that underlie this.
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Affiliation(s)
- Ruth D Murrell-Lagnado
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, United Kingdom.
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Lordén G, Sanjuán-García I, de Pablo N, Meana C, Alvarez-Miguel I, Pérez-García MT, Pelegrín P, Balsinde J, Balboa MA. Lipin-2 regulates NLRP3 inflammasome by affecting P2X7 receptor activation. J Exp Med 2016; 214:511-528. [PMID: 28031477 PMCID: PMC5294860 DOI: 10.1084/jem.20161452] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/23/2016] [Accepted: 12/12/2016] [Indexed: 01/31/2023] Open
Abstract
Lordén et al. show that the phosphatidic acid phosphatase lipin-2 is a key regulator of the cellular machinery that generates IL-1β in macrophages. This work provides a molecular explanation for the development of the autoinflammatory disease known as Majeed syndrome. Mutations in human LPIN2 produce a disease known as Majeed syndrome, the clinical manifestations of which are ameliorated by strategies that block IL-1β or its receptor. However the role of lipin-2 during IL-1β production remains elusive. We show here that lipin-2 controls excessive IL-1β formation in primary human and mouse macrophages by several mechanisms, including activation of the inflammasome NLRP3. Lipin-2 regulates MAPK activation, which mediates synthesis of pro–IL-1β during inflammasome priming. Lipin-2 also inhibits the activation and sensitization of the purinergic receptor P2X7 and K+ efflux, apoptosis-associated speck-like protein with a CARD domain oligomerization, and caspase-1 processing, key events during inflammasome activation. Reduced levels of lipin-2 in macrophages lead to a decrease in cellular cholesterol levels. In fact, restoration of cholesterol concentrations in cells lacking lipin-2 decreases ion currents through the P2X7 receptor, and downstream events that drive IL-1β production. Furthermore, lipin-2–deficient mice exhibit increased sensitivity to high lipopolysaccharide doses. Collectively, our results unveil lipin-2 as a critical player in the negative regulation of NLRP3 inflammasome.
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Affiliation(s)
- Gema Lordén
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
| | - Itziar Sanjuán-García
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
| | - Nagore de Pablo
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
| | - Clara Meana
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
| | - Inés Alvarez-Miguel
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Departamento de Fisiología, Facultad de Medicina, Universidad de Valladolid, 47003 Valladolid, Spain
| | - M Teresa Pérez-García
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Departamento de Fisiología, Facultad de Medicina, Universidad de Valladolid, 47003 Valladolid, Spain
| | - Pablo Pelegrín
- Molecular Inflammation Group, Murcia Biomedical Research Institute, Hospital Virgen de la Arrixaca, Carretera Buenavista, 30120 Murcia, Spain
| | - Jesús Balsinde
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
| | - María A Balboa
- Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid, 47003 Valladolid, Spain .,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, 28029 Madrid, Spain
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12
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Verjans ET, Zels S, Luyten W, Landuyt B, Schoofs L. Molecular mechanisms of LL-37-induced receptor activation: An overview. Peptides 2016; 85:16-26. [PMID: 27609777 DOI: 10.1016/j.peptides.2016.09.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/01/2016] [Accepted: 09/03/2016] [Indexed: 12/30/2022]
Abstract
The human cathelicidin peptide LL-37 plays a crucial role in the immune system on many levels, from the first line of defense in epithelial cells to restoring the tissue after infection. On host cells, the majority of the LL-37-induced effects are mediated via the direct or indirect activation of several structurally unrelated cell surface receptors or intracellular targets. How LL-37 is able to affect multiple receptors is currently not well understood. So far, the mechanistic details underlying receptor activation are poorly investigated and evidence for a conventional ligand/receptor interaction is scarce. Over the past few decades, a large number of studies have reported on the activation of a receptor and/or components of the downstream signal transduction pathway induced by LL-37. This review summarizes the current knowledge on molecular mechanisms underlying LL-37-induced receptor activation.
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Affiliation(s)
- Eddy-Tim Verjans
- KU Leuven, Department of Biology, Division of Neurobiology and Animal Physiology, Naamsestraat 59, 3000 Leuven, Belgium.
| | - Sven Zels
- KU Leuven, Department of Biology, Division of Neurobiology and Animal Physiology, Naamsestraat 59, 3000 Leuven, Belgium
| | - Walter Luyten
- KU Leuven, Department of Biology, Division of Neurobiology and Animal Physiology, Naamsestraat 59, 3000 Leuven, Belgium
| | - Bart Landuyt
- KU Leuven, Department of Biology, Division of Neurobiology and Animal Physiology, Naamsestraat 59, 3000 Leuven, Belgium
| | - Liliane Schoofs
- KU Leuven, Department of Biology, Division of Neurobiology and Animal Physiology, Naamsestraat 59, 3000 Leuven, Belgium
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13
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Sathanoori R, Swärd K, Olde B, Erlinge D. The ATP Receptors P2X7 and P2X4 Modulate High Glucose and Palmitate-Induced Inflammatory Responses in Endothelial Cells. PLoS One 2015; 10:e0125111. [PMID: 25938443 PMCID: PMC4418812 DOI: 10.1371/journal.pone.0125111] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/20/2015] [Indexed: 12/20/2022] Open
Abstract
Endothelial cells lining the blood vessels are principal players in vascular inflammatory responses. Dysregulation of endothelial cell function caused by hyperglycemia, dyslipidemia, and hyperinsulinemia often result in impaired vasoregulation, oxidative stress, inflammation, and altered barrier function. Various stressors including high glucose stimulate the release of nucleotides thus initiating signaling via purinergic receptors. However, purinergic modulation of inflammatory responses in endothelial cells caused by high glucose and palmitate remains unclear. In the present study, we investigated whether the effect of high glucose and palmitate is mediated by P2X7 and P2X4 and if they play a role in endothelial cell dysfunction. Transcript and protein levels of inflammatory genes as well as reactive oxygen species production, endothelial-leukocyte adhesion, and cell permeability were investigated in human umbilical vein endothelial cells exposed to high glucose and palmitate. We report high glucose and palmitate to increase levels of extracellular ATP, expression of P2X7 and P2X4, and inflammatory markers. Both P2X7 and P2X4 antagonists inhibited high glucose and palmitate-induced interleukin-6 levels with the former having a significant effect on interleukin-8 and cyclooxygenase-2. The effect of the antagonists was confirmed with siRNA knockdown of the receptors. In addition, P2X7 mediated both high glucose and palmitate-induced increase in reactive oxygen species levels and decrease in endothelial nitric oxide synthase. Blocking P2X7 inhibited high glucose and palmitate-induced expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 as well as leukocyte-endothelial cell adhesion. Interestingly, high glucose and palmitate enhanced endothelial cell permeability that was dependent on both P2X7 and P2X4. Furthermore, antagonizing the P2X7 inhibited high glucose and palmitate-mediated activation of p38-mitogen activated protein kinase. These findings support a novel role for P2X7 and P2X4 coupled to induction of inflammatory molecules in modulating high glucose and palmitate-induced endothelial cell activation and dysfunction.
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Affiliation(s)
- Ramasri Sathanoori
- Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
- * E-mail:
| | - Karl Swärd
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Björn Olde
- Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
| | - David Erlinge
- Department of Cardiology, Clinical Sciences, Lund University, Lund, Sweden
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14
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Bartlett R, Stokes L, Sluyter R. The P2X7 receptor channel: recent developments and the use of P2X7 antagonists in models of disease. Pharmacol Rev 2015; 66:638-75. [PMID: 24928329 DOI: 10.1124/pr.113.008003] [Citation(s) in RCA: 316] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The P2X7 receptor is a trimeric ATP-gated cation channel found predominantly, but not exclusively, on immune cells. P2X7 activation results in a number of downstream events, including the release of proinflammatory mediators and cell death and proliferation. As such, P2X7 plays important roles in various inflammatory, immune, neurologic and musculoskeletal disorders. This review focuses on the use of P2X7 antagonists in rodent models of neurologic disease and injury, inflammation, and musculoskeletal and other disorders. The cloning and characterization of human, rat, mouse, guinea pig, dog, and Rhesus macaque P2X7, as well as recent observations regarding the gating and permeability of P2X7, are discussed. Furthermore, this review discusses polymorphic and splice variants of P2X7, as well as the generation and use of P2X7 knockout mice. Recent evidence for emerging signaling pathways downstream of P2X7 activation and the growing list of negative and positive modulators of P2X7 activation and expression are also described. In addition, the use of P2X7 antagonists in numerous rodent models of disease is extensively summarized. Finally, the use of P2X7 antagonists in clinical trials in humans and future directions exploring P2X7 as a therapeutic target are described.
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Affiliation(s)
- Rachael Bartlett
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
| | - Leanne Stokes
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
| | - Ronald Sluyter
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
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15
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Inose Y, Kato Y, Kitagawa K, Uchiyama S, Shibata N. Activated microglia in ischemic stroke penumbra upregulate MCP-1 and CCR2 expression in response to lysophosphatidylcholine derived from adjacent neurons and astrocytes. Neuropathology 2014; 35:209-23. [DOI: 10.1111/neup.12182] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 10/16/2014] [Accepted: 10/17/2014] [Indexed: 12/19/2022]
Affiliation(s)
- Yuri Inose
- Graduate School of Medicine; Tokyo Women's Medical University; Tokyo Japan
- Department of Pathology; Tokyo Women's Medical University; Tokyo Japan
- Department of Neurology; Tokyo Women's Medical University; Tokyo Japan
| | - Yoichiro Kato
- Department of Pathology; Tokyo Women's Medical University; Tokyo Japan
| | - Kazuo Kitagawa
- Department of Neurology; Tokyo Women's Medical University; Tokyo Japan
| | - Shinichiro Uchiyama
- Department of Neurology; Tokyo Women's Medical University; Tokyo Japan
- Clinical Research Center for Medicine; International University of Health and Welfare; Tokyo Japan
- Center for Brain and Cerebral Vessels; Sanno Hospital and Sanno Medical Center; Tokyo Japan
| | - Noriyuki Shibata
- Department of Pathology; Tokyo Women's Medical University; Tokyo Japan
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16
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Robinson LE, Shridar M, Smith P, Murrell-Lagnado RD. Plasma membrane cholesterol as a regulator of human and rodent P2X7 receptor activation and sensitization. J Biol Chem 2014; 289:31983-31994. [PMID: 25281740 PMCID: PMC4231676 DOI: 10.1074/jbc.m114.574699] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
P2X7 receptors are nonselective cation channels gated by high extracellular ATP, but with sustained activation, receptor sensitization occurs, whereby the intrinsic pore dilates, making the cell permeable to large organic cations, which eventually leads to cell death. P2X7 receptors associate with cholesterol-rich lipid rafts, but it is unclear how this affects the properties of the receptor channel. Here we show that pore-forming properties of human and rodent P2X7 receptors are sensitive to perturbations of cholesterol levels. Acute depletion of cholesterol with 5 mm methyl-β-cyclodextrin (MCD) caused a substantial increase in the rate of agonist-evoked pore formation, as measured by the uptake of ethidium dye, whereas cholesterol loading inhibited this process. Patch clamp analysis of P2X7 receptor currents carried by Na+ and N-methyl-d-glucamine (NMDG+) showed enhanced activation and current facilitation following cholesterol depletion. This contrasts with the inhibitory effect of methyl-β-cyclodextrin reported for other P2X subtypes. Mutational analysis suggests the involvement of an N-terminal region and a proximal C-terminal region that comprises multiple cholesterol recognition amino acid consensus (CRAC) motifs, in the cholesterol sensitivity of channel gating. These results reveal cholesterol as a negative regulator of P2X7 receptor pore formation, protecting cells from P2X7-mediated cell death.
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Affiliation(s)
- Lucy E Robinson
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Mitesh Shridar
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Philip Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Ruth D Murrell-Lagnado
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
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17
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Kuhny M, Hochdörfer T, Ayata CK, Idzko M, Huber M. CD39 is a negative regulator of P2X7-mediated inflammatory cell death in mast cells. Cell Commun Signal 2014; 12:40. [PMID: 25184735 PMCID: PMC4110707 DOI: 10.1186/s12964-014-0040-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 06/13/2014] [Indexed: 02/08/2023] Open
Abstract
Background Mast cells (MCs) are major contributors to an inflammatory milieu. One of the most potent drivers of inflammation is the cytokine IL-1β, which is produced in the cytoplasm in response to danger signals like LPS. Several controlling mechanisms have been reported which limit the release of IL-1β. Central to this regulation is the NLRP3 inflammasome, activation of which requires a second danger signal with the capacity to subvert the homeostasis of lysosomes and mitochondria. High concentrations of extracellular ATP have the capability to perturb the plasma membrane by activation of P2X7 channels and serve as such a danger signal. In this study we investigate the role of P2X7 channels and the ecto-5´-nucleotidase CD39 in ATP-triggered release of IL-1β from LPS-treated mast cells. Results We report that in MCs CD39 sets an activation threshold for the P2X7-dependent inflammatory cell death and concomitant IL-1β release. Knock-out of CD39 or stimulation with non-hydrolysable ATP led to a lower activation threshold for P2X7-dependent responses. We found that stimulation of LPS-primed MCs with high doses of ATP readily induced inflammatory cell death. Yet, cell death-dependent release of IL-1β yielded only minute amounts of IL-1β. Intriguingly, stimulation with low ATP concentrations augmented the production of IL-1β in LPS-primed MCs in a P2X7-independent but caspase-1-dependent manner. Conclusion Our study demonstrates that the fine-tuned interplay between ATP and different surface molecules recognizing or modifying ATP can control inflammatory and cell death decisions.
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18
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Luheshi NM, Giles JA, Lopez-Castejon G, Brough D. Sphingosine regulates the NLRP3-inflammasome and IL-1β release from macrophages. Eur J Immunol 2011; 42:716-25. [PMID: 22105559 PMCID: PMC3491674 DOI: 10.1002/eji.201142079] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 11/14/2011] [Indexed: 12/20/2022]
Abstract
Interleukin-1β (IL-1β) is a pro-inflammatory cytokine that regulates inflammatory responses to injury and infection. IL-1β secretion requires the protease caspase-1, which is activated following recruitment to inflammasomes. Endogenous danger-associated molecular patterns (DAMPs) released from necrotic cells activate caspase-1 through an NLRP3-inflammasome. Here, we show that the endogenous lipid metabolite sphingosine (Sph) acts as a DAMP by inducing the NLRP3-inflammasome-dependent secretion of IL-1β from macrophages. This process was dependent upon serine/threonine protein phosphatases since the PP1/PP2A inhibitors okadaic acid and calyculin A inhibited Sph-induced IL-1β release. IL-1β release induced by other well-characterized NLRP3-inflammasome activators, such as ATP and uric acid crystals, in addition to NLRC4 and AIM2 inflammasome activators was also blocked by these inhibitors. Thus, we propose Sph as a new DAMP, and that a serine/threonine phosphatase (PP1/PP2A)-dependent signal is central to the endogenous host mechanism through which diverse stimuli regulate inflammasome activation.
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Affiliation(s)
- Nadia M Luheshi
- Faculty of Life Sciences, University of Manchester, Manchester, UK
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19
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Lipopolysaccharide inhibits the channel activity of the P2X7 receptor. Mediators Inflamm 2011; 2011:152625. [PMID: 21941410 PMCID: PMC3173735 DOI: 10.1155/2011/152625] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 06/03/2011] [Accepted: 06/20/2011] [Indexed: 11/29/2022] Open
Abstract
The purinergic P2X7 receptor (P2X7R) plays an important role during the immune response, participating in several events such as cytokine release, apoptosis, and necrosis. The bacterial endotoxin lipopolysaccharide (LPS) is one of the strongest stimuli of the immune response, and it has been shown that P2X7R activation can modulate LPS-induced responses. Moreover, a C-terminal binding site for LPS has been proposed. In order to evaluate if LPS can directly modulate the activity of the P2X7R, we tested several signaling pathways associated with P2X7R activation in HEK293 cells that do not express the TLR-4 receptor. We found that LPS alone was unable to induce any P2X7R-related activity, suggesting that the P2X7R is not directly activated by the endotoxin. On the other hand, preapplication of LPS inhibited ATP-induced currents, intracellular calcium increase, and ethidium bromide uptake and had no effect on ERK activation in HEK293 cells. In splenocytes-derived T-regulatory cells, in which ATP-induced apoptosis is driven by the P2X7R, LPS inhibited ATP-induced apoptosis. Altogether, these results demonstrate that LPS modulates the activity of the P2X7R and suggest that this effect could be of physiological relevance.
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20
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Lemaire I, Falzoni S, Zhang B, Pellegatti P, Di Virgilio F. The P2X7 receptor and Pannexin-1 are both required for the promotion of multinucleated macrophages by the inflammatory cytokine GM-CSF. THE JOURNAL OF IMMUNOLOGY 2011; 187:3878-87. [PMID: 21865551 DOI: 10.4049/jimmunol.1002780] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The P2X(7) receptor (P2X(7)R), an ATP-gated ion channel, has been implicated in the process of cell-to-cell fusion into multinucleated macrophages (MA), but its contribution to MA fusion driven by physiological/pathological stimuli is not clearly established. Based on several lines of evidence, we demonstrate that P2X(7)R is critical for the induction of multinucleated MA by the inflammatory cytokine GM-CSF: 1) pharmacological inhibition of P2X(7)R with oxidized ATP (oATP), KN-62, and the selective antagonist A740003 abrogated GM-CSF action on rat alveolar MA and murine peritoneal MA; 2) a murine J774 P2X(7) low MA clone, selected for defective P2X(7)R function, was unresponsive; 3) MA from mice lacking P2X(7)R failed to respond to GM-CSF, in contrast to wild-type. GM-CSF also stimulated ATP-induced membrane permeabilization in J774 P2X(7) high MA and rat alveolar MA, an effect absent in the P2X(7) low MA clone and inhibited by the P2X(7) blockers oATP and KN-62. Notably, the stimulatory effects of GM-CSF on pore formation and MA fusion were both inhibited by blocking functional Pannexin-1 (Panx-1), and GM-CSF failed to stimulate MA fusion in cells from Panx-1 knockout mice. We provide further evidence that extracellular ATP release from peritoneal MA is dependent on P2X(7) but not on Panx-1 expression and that its metabolism to adenosine mediates P2X(7)-dependent MA fusion. These data demonstrate that both P2X(7) and Panx-1 are required for GM-CSF promotion of MA fusion but likely act independently through different signaling pathway(s).
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Affiliation(s)
- Irma Lemaire
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
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21
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Coddou C, Yan Z, Obsil T, Huidobro-Toro JP, Stojilkovic SS. Activation and regulation of purinergic P2X receptor channels. Pharmacol Rev 2011; 63:641-83. [PMID: 21737531 DOI: 10.1124/pr.110.003129] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mammalian ATP-gated nonselective cation channels (P2XRs) can be composed of seven possible subunits, denoted P2X1 to P2X7. Each subunit contains a large ectodomain, two transmembrane domains, and intracellular N and C termini. Functional P2XRs are organized as homomeric and heteromeric trimers. This review focuses on the binding sites involved in the activation (orthosteric) and regulation (allosteric) of P2XRs. The ectodomains contain three ATP binding sites, presumably located between neighboring subunits and formed by highly conserved residues. The detection and coordination of three ATP phosphate residues by positively charged amino acids are likely to play a dominant role in determining agonist potency, whereas an AsnPheArg motif may contribute to binding by coordinating the adenine ring. Nonconserved ectodomain histidines provide the binding sites for trace metals, divalent cations, and protons. The transmembrane domains account not only for the formation of the channel pore but also for the binding of ivermectin (a specific P2X4R allosteric regulator) and alcohols. The N- and C- domains provide the structures that determine the kinetics of receptor desensitization and/or pore dilation and are critical for the regulation of receptor functions by intracellular messengers, kinases, reactive oxygen species and mercury. The recent publication of the crystal structure of the zebrafish P2X4.1R in a closed state provides a major advance in the understanding of this family of receptor channels. We will discuss data obtained from numerous site-directed mutagenesis experiments accumulated during the last 15 years with reference to the crystal structure, allowing a structural interpretation of the molecular basis of orthosteric and allosteric ligand actions.
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Affiliation(s)
- Claudio Coddou
- Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Developmant, National Institutes of Health, Bethesda, MD 20892-4510, USA
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22
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Nörenberg W, Hempel C, Urban N, Sobottka H, Illes P, Schaefer M. Clemastine potentiates the human P2X7 receptor by sensitizing it to lower ATP concentrations. J Biol Chem 2011; 286:11067-81. [PMID: 21262970 PMCID: PMC3064161 DOI: 10.1074/jbc.m110.198879] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 01/10/2011] [Indexed: 01/08/2023] Open
Abstract
P2X7 receptors have emerged as potential drug targets for the treatment of medical conditions such as e.g. rheumatoid arthritis and neuropathic pain. To assess the impact of pharmaceuticals on P2X7, we screened a compound library comprising approved or clinically tested drugs and identified several compounds that augment the ATP-triggered P2X7 activity in a stably transfected HEK293 cell line. Of these, clemastine markedly sensitized Ca(2+) entry through P2X7 to lower ATP concentrations. Extracellularly but not intracellularly applied clemastine rapidly and reversibly augmented P2X7-mediated whole-cell currents evoked by non-saturating ATP concentrations. Clemastine also accelerated the ATP-induced pore formation and Yo-Pro-1 uptake, increased the fractional NMDG(+) permeability, and stabilized the open channel conformation of P2X7. Thus, clemastine is an extracellularly binding allosteric modulator of P2X7 that sensitizes P2X7 to lower ATP concentrations and facilitates its pore dilation. The activity of clemastine on native P2X7 receptors, Ca(2+) entry, and whole-cell currents was confirmed in human monocyte-derived macrophages. Similar effects were observed in murine bone marrow-derived macrophages. Consistent with the data on recombinant P2X7, clemastine augmented the ATP-induced cation entry and Yo-Pro-1 uptake. In accordance with the observation that P2X7 controls the cytokine release from LPS-primed macrophages, we found that clemastine augmented the IL-1β release from LPS-primed human macrophages. Collectively, these data point to a sensitization of the recombinantly or natively expressed human P2X7 receptor toward its physiological activator, ATP, possibly leading to a modulation of macrophage-dependent immune responses.
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Affiliation(s)
- Wolfgang Nörenberg
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Christoph Hempel
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Nicole Urban
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Helga Sobottka
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Peter Illes
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Michael Schaefer
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
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23
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Abstract
Seven mammalian purinergic receptor subunits, denoted P2X1-P2X7, and several spliced forms of these subunits have been cloned. When heterologously expressed, these cDNAs encode ATP-gated non-selective cation channels organized as trimers. All activated receptors produce cell depolarization and promote Ca(2+) influx through their pores and indirectly by activating voltage-gated calcium channels. However, the biophysical and pharmacological properties of these receptors differ considerably, and the majority of these subunits are also capable of forming heterotrimers with other members of the P2X receptor family, which confers further different properties. These channels have three ATP binding domains, presumably located between neighboring subunits, and occupancy of at least two binding sites is needed for their activation. In addition to the orthosteric binding sites for ATP, these receptors have additional allosteric sites that modulate the agonist action at receptors, including sites for trace metals, protons, neurosteroids, reactive oxygen species and phosphoinositides. The allosteric regulation of P2X receptors is frequently receptor-specific and could be a useful tool to identify P2X members in native tissues and their roles in signaling. The focus of this review is on common and receptor-specific allosteric modulation of P2X receptors and the molecular base accounting for allosteric binding sites.
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Affiliation(s)
- Claudio Coddou
- Section on Cellular Signaling, Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-4510, USA.
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Mycobacterium tuberculosis synergizes with ATP to induce release of microvesicles and exosomes containing major histocompatibility complex class II molecules capable of antigen presentation. Infect Immun 2010; 78:5116-25. [PMID: 20837713 DOI: 10.1128/iai.01089-09] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Major histocompatibility complex class II (MHC-II) molecules are released by murine macrophages upon lipopolysaccharide (LPS) stimulation and ATP signaling through the P2X7 receptor. These studies show that infection of macrophages with Mycobacterium tuberculosis or M. bovis strain BCG enhances MHC-II release in synergy with ATP. Shed MHC-II was contained in two distinct organelles, exosomes and plasma membrane-derived microvesicles, which were both able to present exogenous antigenic peptide to T hybridoma cells. Furthermore, microvesicles from mycobacterium-infected macrophages were able to directly present M. tuberculosis antigen (Ag) 85B(241-256)-I-A(b) complexes that were generated by the processing of M. tuberculosis Ag 85B in infected cells to both M. tuberculosis-specific T hybridoma cells and naïve P25 M. tuberculosis T-cell receptor (TCR)-transgenic T cells. In the presence of prefixed macrophages, exosomes from mycobacterium-infected macrophages provided weak stimulation to M. tuberculosis-specific T hybridoma cells but not naïve P25 T cells. Thus, infection with M. tuberculosis primes macrophages for the increased release of exosomes and microvesicles bearing M. tuberculosis peptide-MHC-II complexes that may generate antimicrobial T-cell responses.
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Bruzzone S, Basile G, Chothi MP, Nobbio L, Usai C, Jacchetti E, Schenone A, Guse AH, Di Virgilio F, De Flora A, Zocchi E. Diadenosine homodinucleotide products of ADP-ribosyl cyclases behave as modulators of the purinergic receptor P2X7. J Biol Chem 2010; 285:21165-74. [PMID: 20439466 DOI: 10.1074/jbc.m109.097964] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
ADP-ribosyl cyclases from both vertebrates and invertebrates were previously shown to produce two isomers of P1,P2 diadenosine 5',5'"-P1, P2-diphosphate, P18 and P24, from cyclic ADP-ribose (cADPR) and adenine. P18 and P24 are characterized by an unusual N-glycosidic linkage in one of the adenylic mononucleotides (Basile, G., Taglialatela-Scafati, O., Damonte, G., Armirotti, A., Bruzzone, S., Guida, L., Franco, L., Usai, C., Fattorusso, E., De Flora, A., and Zocchi, E. (2005) Proc. Natl. Acad. Sci. U.S.A. 102, 14509-14514). P24, but not P18, proved to increase the intracellular Ca(2+) concentration ([Ca(2+)](i)) in HeLa cells and to negatively affect mitochondrial function. Here we show that micromolar P24, but not P18, triggers a slow and sustained influx of extracellular Ca(2+) through the opening of the purinergic receptor/channel P2X7. On the other hand, P18 inhibits the Ca(2+) influx induced by 0.6 mm ATP in HEK293 cells stably transfected with P2X7, with an IC(50) of approximately 1 mum. Thus, P18 is devoid of intrinsic P2X7 stimulatory activity and behaves as an ATP antagonist. A P2X7-mediated increase of the basal [Ca(2+)](i) has been demonstrated to negatively affect Schwann cell (SC) function in rats with the inherited, peripheral neuropathy Charcot-Marie-Tooth 1A (CMT1A) (Nobbio, L., Sturla, L., Fiorese, F., Usai, C., Basile, G., Moreschi, I., Benvenuto, F., Zocchi, E., De Flora, A., Schenone, A., and Bruzzone S. (2009) J. Biol. Chem. 284, 23146-23158). Preincubation of CMT1A SC with 200 nm P18 restored the basal [Ca(2+)](i) to values similar to those recorded in wild-type SC. These results identify P18 as a new P2X7 antagonist, potentially useful in the treatment of CMT1A.
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Affiliation(s)
- Santina Bruzzone
- Department of Experimental Medicine, Section of Biochemistry, and Center of Excellence for Biomedical Research (CEBR), University of Genova, Viale Benedetto XV/1, 16132 Genova, Italy.
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Roman S, Cusdin FS, Fonfria E, Goodwin JA, Reeves J, Lappin SC, Chambers L, Walter DS, Clay WC, Michel AD. Cloning and pharmacological characterization of the dog P2X7 receptor. Br J Pharmacol 2009; 158:1513-26. [PMID: 19814727 DOI: 10.1111/j.1476-5381.2009.00425.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND AND PURPOSE Human and rodent P2X7 receptors exhibit differences in their sensitivity to antagonists. In this study we have cloned and characterized the dog P2X7 receptor to determine if its antagonist sensitivity more closely resembles the human or rodent orthologues. EXPERIMENTAL APPROACH A cDNA encoding the dog P2X7 receptor was isolated from a dog heart cDNA library, expressed in U-2 OS cells using the BacMam viral expression system and characterized in electrophysiological, ethidium accumulation and radioligand binding studies. Native P2X7 receptors were examined by measuring ATP-stimulated interleukin-1beta release in dog and human whole blood. KEY RESULTS The dog P2X7 receptor was 595 amino acids long and exhibited high homology (>70%) to the human and rodent orthologues although it contained an additional threonine at position 284 and an amino acid deletion at position 538. ATP possessed low millimolar potency at dog P2X7 receptors. 2'-&3'-O-(4benzoylbenzoyl) ATP had slightly higher potency but was a partial agonist. Dog P2X7 receptors possessed relatively high affinity for a number of selective antagonists of the human P2X7 receptor although there were some differences in potency between the species. Compound affinities in human and dog blood exhibited a similar rank order of potency as observed in studies on the recombinant receptor although absolute potency was considerably lower. CONCLUSIONS AND IMPLICATIONS Dog recombinant and native P2X7 receptors display a number of pharmacological similarities to the human P2X7 receptor. Thus, dog may be a suitable species for assessing target-related toxicity of antagonists intended for evaluation in the clinic.
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Affiliation(s)
- S Roman
- Neurology Centre of Excellence for Drug Discovery, GlaxoSmithKline Research & Development Limited, New Frontiers Science Park, Harlow, Essex, UK.
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Hong S, Schwarz N, Brass A, Seman M, Haag F, Koch-Nolte F, Schilling WP, Dubyak GR. Differential regulation of P2X7 receptor activation by extracellular nicotinamide adenine dinucleotide and ecto-ADP-ribosyltransferases in murine macrophages and T cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:578-92. [PMID: 19542469 DOI: 10.4049/jimmunol.0900120] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Extracellular NAD induces the ATP-independent activation of the ionotropic P2X(7) purinergic receptor (P2X(7)R) in murine T lymphocytes via a novel covalent pathway involving ADP-ribosylation of arginine residues on the P2X(7)R ectodomain. This modification is catalyzed by ART2.2, a GPI-anchored ADP-ribosyltransferase (ART) that is constitutively expressed in murine T cells. We previously reported that ART2.1, a related ecto-ART, is up-regulated in inflammatory murine macrophages that constitutively express P2X(7)R. Thus, we tested the hypothesis that extracellular NAD acts via ART2.1 to regulate P2X(7)R function in murine macrophages. Coexpression of the cloned murine P2X(7)R with ART2.1 or ART2.2 in HEK293 cells verified that P2X(7)R is an equivalent substrate for ADP-ribosylation by either ART2.1 or ART2.2. However, in contrast with T cells, the stimulation of macrophages or HEK293 cells with NAD alone did not activate the P2X(7)R. Rather, NAD potentiated ATP-dependent P2X(7)R activation as indicated by a left shift in the ATP dose-response relationship. Thus, extracellular NAD regulates the P2X(7)R in both macrophages and T cells but via distinct mechanisms. Although ADP-ribosylation is sufficient to gate a P2X(7)R channel opening in T cells, this P2X(7)R modification in macrophages does not gate the channel but decreases the threshold for gating in response to ATP binding. These findings indicate that extracellular NAD and ATP can act synergistically to regulate P2X(7)R signaling in murine macrophages and also suggest that the cellular context in which P2X(7)R signaling occurs differs between myeloid and lymphoid leukocytes.
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Affiliation(s)
- Shiyuan Hong
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44120, USA
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Takenouchi T, Iwamaru Y, Sugama S, Sato M, Hashimoto M, Kitani H. Lysophospholipids and ATP mutually suppress maturation and release of IL-1 beta in mouse microglial cells using a Rho-dependent pathway. THE JOURNAL OF IMMUNOLOGY 2008; 180:7827-39. [PMID: 18523246 DOI: 10.4049/jimmunol.180.12.7827] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The P2X7 receptor (P2X7R), an ATP-gated ion channel, plays essential roles in the release and maturation of IL-1beta in microglial cells in the brain. Previously, we found that lysophosphatidylcholine (LPC) potentiated P2X7R-mediated intracellular signals in microglial cells. In this study, we determined whether the lysophospholipids, i.e., LPC and sphingosylphosphorylcholine (SPC), modulate the ATP-induced release and processing of IL-1beta mediated by P2X7R in mouse MG6 microglial cells. LPC or SPC alone induced the release of precursor (pro-IL-1beta) and mature IL-1beta (mIL-1beta) from LPS-primed MG6 cells, possibly due to lytic functions. However, these lysophospholipids inhibited ATP-induced caspase-1 activation that is usually followed by the release of mIL-1beta. Conversely, ATP inhibited the release of pro-IL-1beta and mIL-1beta induced by LPC/SPC. This suggests that lysophospholipids and ATP mutually suppressed each function to release IL-1beta. P2X7R activation resulted in microtubule reorganization in the MG6 cells that was blocked in the presence of LPC and SPC. LPC/SPC reduced the amount of activated RhoA after stimulation with ATP, implying that these lysophospholipids block ATP-induced microtubule reorganization by interfering with RhoA activation. In addition, the microtubule inhibitor colchicine inhibited ATP-induced release of mIL-1beta similar to that of LPC and SPC. This suggests that the impairment of the microtubule reassembly may be associated with the inhibitory effects of LPC/SPC on ATP-induced mIL-1beta release. Mutual suppression by ATP and LPC/SPC on the maturation of IL-1beta was observed in LPS-primed primary microglia. Collectively, these data suggest opposing functions by lysophospholipids, either proinflammatory or anti-inflammatory, in regard to the maturation and release of IL-1beta from microglial cells.
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Affiliation(s)
- Takato Takenouchi
- Transgenic Animal Research Center, National Institute of Agrobiological Sciences, Tsukuba, Japan
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Tomasinsig L, Pizzirani C, Skerlavaj B, Pellegatti P, Gulinelli S, Tossi A, Di Virgilio F, Zanetti M. The human cathelicidin LL-37 modulates the activities of the P2X7 receptor in a structure-dependent manner. J Biol Chem 2008; 283:30471-81. [PMID: 18765670 DOI: 10.1074/jbc.m802185200] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Extracellular ATP, released at sites of inflammation or tissue damage, activates the P2X(7) receptor, which in turn triggers a range of responses also including cell proliferation. In this study the ability of the human cathelicidin LL-37 to stimulate fibroblast growth was inhibited by commonly used P2X(7) blockers. We investigated the structural requirements of the growth-promoting activity of LL-37 and found that it did not depend on helix sense (the all-d analog was active) but did require a strong helix-forming propensity in aqueous solution (a scrambled analog and primate LL-37 orthologs devoid of this property were inactive). The involvement of P2X(7) was analyzed using P2X(7)-expressing HEK293 cells. LL-37 induced proliferation of these cells, triggered Ca(2+) influx, promoted ethidium bromide uptake, and synergized with benzoyl ATP to enhance the pore and channel functions of P2X(7). The activity of LL-37 had an absolute requirement for P2X(7) expression as it was blocked by the P2X(7) inhibitor KN-62, was absent in cells lacking P2X(7), and was restored by P2X(7) transfection. Of particular interest, LL-37 led to pore-forming activity in cells expressing a truncated P2X(7) receptor unable to generate the non-selective pore typical of the full-length receptor. Our results indicate that P2X(7) is involved in the proliferative cell response to LL-37 and that the structural/aggregational properties of LL-37 determine its capacity to modulate the activation state of P2X(7).
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Affiliation(s)
- Linda Tomasinsig
- Department of Biomedical Sciences and Technology, University of Udine, 33100 Udine, Italy
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Michel AD, Clay WC, Ng SW, Roman S, Thompson K, Condreay JP, Hall M, Holbrook J, Livermore D, Senger S. Identification of regions of the P2X(7) receptor that contribute to human and rat species differences in antagonist effects. Br J Pharmacol 2008; 155:738-51. [PMID: 18660826 DOI: 10.1038/bjp.2008.306] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND AND PURPOSE Several P2X(7) receptor antagonists are allosteric inhibitors and exhibit species difference in potency. Furthermore, N(2)-(3,4-difluorophenyl)-N(1)-(2-methyl-5-(1-piperazinylmethyl)phenyl)glycinamide dihydrochloride (GW791343) exhibits negative allosteric effects at the human P2X(7) receptor but is a positive allosteric modulator of the rat P2X(7) receptor. In this study we have identified several regions of the P2X(7) receptor that contribute to the species differences in antagonist effects. EXPERIMENTAL APPROACH Chimeric human-rat P2X(7) receptors were constructed with regions of the rat receptor being inserted into the human receptor. Antagonist effects at these receptors were measured in ethidium accumulation and radioligand binding studies. KEY RESULTS Exchanging regions of the P2X(7) receptor close to transmembrane domain 1 modified the effects of KN62, 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580) and GW791343. Further studies, in which single amino acids were exchanged, identified amino acid 95 as being primarily responsible for the differential allosteric effects of GW791343 and, to varying degrees, the species differences in potency of SB203580 and KN62. The species selectivity of pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid was affected by multiple regions of the receptor, with potency being particularly affected by the amino acid 126 but not by amino acid 95. A further region of the rat receptor (amino acids 154-183) was identified that, when inserted into the corresponding position in the human receptor, increased ATP potency 10-fold. CONCLUSIONS This study has identified several key residues responsible for the species differences in antagonist effects at the P2X(7) receptor and also identified a further region of the P2X(7) receptor that can significantly affect agonist potency at the P2X(7) receptor.
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Affiliation(s)
- A D Michel
- Neurology Centre of Excellence for Drug Discovery, GlaxoSmithKline Research & Development Limited, New Frontiers Science Park, Harlow, Essex, UK.
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Michel AD, Chambers LJ, Walter DS. Negative and positive allosteric modulators of the P2X(7) receptor. Br J Pharmacol 2007; 153:737-50. [PMID: 18071294 DOI: 10.1038/sj.bjp.0707625] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND AND PURPOSE Antagonist effects at the P2X(7) receptor are complex with many behaving in a non-competitive manner. In this study, the effects of N-[2-({2-[(2-hydroxyethyl)amino]ethyl}amino)-5-quinolinyl]-2-tricyclo[3.3.1.1(3,7)]dec-1-ylacetamide (compound-17) and N (2)-(3,4-difluorophenyl)-N (1)-[2-methyl-5-(1-piperazinylmethyl)phenyl]glycinamide dihydrochloride (GW791343) on P2X(7) receptors were examined and their mechanism of action explored. EXPERIMENTAL APPROACH Antagonist effects were studied by measuring agonist-stimulated ethidium accumulation in cells expressing human or rat recombinant P2X(7) receptors and in radioligand binding studies. KEY RESULTS Compound-17 and GW791343 were non-competitive inhibitors of human P2X(7) receptors. Receptor protection studies using decavanadate and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) showed that neither compound-17 nor GW791343 competitively interacted at the ATP binding site and so were probably negative allosteric modulators of the P2X(7) receptor. GW791343 prevented the slowly reversible blockade of the human P2X(7) receptor produced by compound-17 and inhibited [(3)H]-compound-17 binding to the P2X(7) receptor suggesting they may bind to similar or interacting sites. At rat P2X(7) receptors, compound-17 was a negative allosteric modulator but the predominant effect of GW791343 was to increase agonist responses. Antagonist interaction and radioligand binding studies revealed that GW791343 did not interact at the ATP binding site but did interact with the compound-17 binding site suggesting that GW791343 is a positive allosteric modulator of the rat P2X(7) receptor. CONCLUSIONS Compound-17 was a negative allosteric modulator of human and rat P2X(7) receptors. GW791343 was a negative allosteric modulator of the human P2X(7) receptor but at the rat P2X(7) receptor its predominant effect was positive allosteric modulation. These compounds should provide valuable tools for mechanistic studies on P2X(7) receptors.
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Affiliation(s)
- A D Michel
- Neurology Centre of Excellence for Drug Discovery, GlaxoSmithKline Research & Development Limited, Harlow, Essex, UK.
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