51
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Nowodworska A, van den Maagdenberg AMJM, Nistri A, Fabbretti E. In situ imaging reveals properties of purinergic signalling in trigeminal sensory ganglia in vitro. Purinergic Signal 2017; 13:511-520. [PMID: 28822016 PMCID: PMC5714839 DOI: 10.1007/s11302-017-9576-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 08/01/2017] [Indexed: 12/22/2022] Open
Abstract
Chronic pain is supported by sterile inflammation that induces sensitisation of sensory neurons to ambient stimuli including extracellular ATP acting on purinergic P2X receptors. The development of in vitro methods for drug screening would be useful to investigate cell crosstalk and plasticity mechanisms occurring during neuronal sensitisation and sterile neuroinflammation. Thus, we studied, at single-cell level, membrane pore dilation based on the uptake of a fluorescent probe following sustained ATP-gated P2X receptor function in neurons and non-neuronal cells of trigeminal ganglion cultures from wild-type (WT) and R192Q CaV2.1 knock-in (KI) mice, a model of familial hemiplegic migraine type 1 characterised by neuronal sensitisation and higher release of soluble mediators. In WT cultures, pore responses were mainly evoked by ATP rather than benzoyl-ATP (BzATP) and partly inhibited by the P2X antagonist TNP-ATP. P2X7 receptors were expressed in trigeminal ganglia mainly by non-neuronal cells. In contrast, KI cultures showed higher expression of P2X7 receptors, stronger responses to BzATP, an effect largely prevented by prior administration of CaV2.1 blocker ω-agatoxin IVA, small interfering RNA (siRNA)-based silencing of P2X7 receptors or the P2X7 antagonist A-804598. No cell toxicity was detected with the protocols. Calcitonin gene-related peptide (CGRP), a well-known migraine mediator, potentiated BzATP-evoked membrane permeability in WT as well as R192Q KI cultures, demonstrating its modulatory role on trigeminal sensory ganglia. Our results show an advantageous experimental approach to dissect pharmacological properties potentially relevant to chronic pain and suggest that CGRP is a soluble mediator influencing purinergic P2X pore dilation and regulating inflammatory responses.
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Affiliation(s)
- Arletta Nowodworska
- Neuroscience Department, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136, Trieste, Italy
| | | | - Andrea Nistri
- Neuroscience Department, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136, Trieste, Italy
| | - Elsa Fabbretti
- Center for Biomedical Sciences and Engineering, University of Nova Gorica, Vipavska 13, 5000, Nova Gorica, Slovenia.
- Department of Life Sciences, University of Trieste, via Giorgieri 5, 34127, Trieste, Italy.
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52
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Schneider M, Prudic K, Pippel A, Klapperstück M, Braam U, Müller CE, Schmalzing G, Markwardt F. Interaction of Purinergic P2X4 and P2X7 Receptor Subunits. Front Pharmacol 2017; 8:860. [PMID: 29213241 PMCID: PMC5702805 DOI: 10.3389/fphar.2017.00860] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 11/09/2017] [Indexed: 11/13/2022] Open
Abstract
P2X4 and P2X7 are members of the P2X receptor family, comprising seven isoforms (P2X1–P2X7) that form homo- and heterotrimeric non-specific cation channels gated by extracellular ATP. P2X4 and P2X7 are widely coexpressed, particularly in secretory epithelial cells and immune and inflammatory cells, and regulate inflammation and nociception. Although functional heteromerization has been established for P2X2 and P2X3 subunits expressed in sensory neurons, there are contradictory reports regarding a functional interaction between P2X4 and P2X7 subunits. To resolve this issue, we coexpressed P2X4 and P2X7 receptor subunits labeled with green (EGFP) and red (TagRFP) fluorescent proteins in Xenopus laevis oocytes and investigated a putative physical interaction between the fusion proteins by Förster resonance energy transfer (FRET). Coexpression of P2X4 and P2X7 subunits with EGFP and TagRFP located in the extracellular receptor domains led to significant FRET signals. Significant FRET signals were also measured between C-terminally fluorophore-labeled full-length P2X41-384 and C-terminally truncated fluorescent P2X71-408 subunits. We furthermore used the two-electrode voltage clamp technique to investigate whether human P2X4 and P2X7 receptors (hP2X4, hP2X7) functionally interact at the level of ATP-induced whole-cell currents. Concentration–response curves and effects of ivermectin (P2X4-potentiating drug) or BzATP (P2X7-specific agonist) were consistent with a model in which coexpressed hP2X4 and hP2X7 do not interact. Similarly, the effect of adding specific inhibitors of P2X4 (PSB-15417) or P2X7 (oATP, A438079) could be explained by a model in which only homomers exist, and that these are blocked by the respective antagonist. In conclusion, we show that P2X4 and P2X7 subunits can form heterotrimeric P2X4/P2X7 receptors. However, unlike observations for P2X2 and P2X3, coexpression of P2X4 and P2X7 subunits does not result in a novel electrophysiologically discriminable P2X receptor phenotype.
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Affiliation(s)
- Markus Schneider
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany
| | - Kirsten Prudic
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany
| | - Anja Pippel
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany
| | - Manuela Klapperstück
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany
| | - Ursula Braam
- Molecular Pharmacology, RWTH Aachen University, Aachen, Germany
| | - Christa E Müller
- Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, Bonn, Germany
| | | | - Fritz Markwardt
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University, Halle, Germany
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53
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Suurväli J, Boudinot P, Kanellopoulos J, Rüütel Boudinot S. P2X4: A fast and sensitive purinergic receptor. Biomed J 2017; 40:245-256. [PMID: 29179879 PMCID: PMC6138603 DOI: 10.1016/j.bj.2017.06.010] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 06/28/2017] [Accepted: 06/30/2017] [Indexed: 01/31/2023] Open
Abstract
Extracellular nucleotides have been recognized as important mediators of activation, triggering multiple responses via plasma membrane receptors known as P2 receptors. P2 receptors comprise P2X ionotropic receptors and G protein-coupled P2Y receptors. P2X receptors are expressed in many tissues, where they are involved in a number of functions including synaptic transmission, muscle contraction, platelet aggregation, inflammation, macrophage activation, differentiation and proliferation, neuropathic and inflammatory pain. P2X4 is one of the most sensitive purinergic receptors (at nanomolar ATP concentrations), about one thousand times more than the archetypal P2X7. P2X4 is widely expressed in central and peripheral neurons, in microglia, and also found in various epithelial tissues and endothelial cells. It localizes on the plasma membrane, but also in intracellular compartments. P2X4 is preferentially localized in lysosomes, where it is protected from proteolysis by its glycosylation. High ATP concentration in the lysosomes does not activate P2X4 at low pH; P2X4 gets activated by intra-lysosomal ATP only in its fully dissociated tetra-anionic form, when the pH increases to 7.4. Thus, P2X4 is functioning as a Ca2+-channel after the fusion of late endosomes and lysosomes. P2X4 modulates major neurotransmitter systems and regulates alcohol-induced responses in microglia. P2X4 is one of the key receptors mediating neuropathic pain. However, injury-induced upregulation of P2X4 expression is gender dependent and plays a key role in pain difference between males and females. P2X4 is also involved in inflammation. Extracellular ATP being a pro-inflammatory molecule, P2X4 can trigger inflammation in response to high ATP release. It is therefore involved in multiple pathologies, like post-ischemic inflammation, rheumatoid arthritis, airways inflammation in asthma, neurodegenerative diseases and even metabolic syndrome. Although P2X4 remains poorly characterized, more studies are needed as it is likely to be a potential therapeutic target in these multiple pathologies.
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Affiliation(s)
- Jaanus Suurväli
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn, Estonia
| | - Pierre Boudinot
- Virologie et Immunologie Moléculaires, INRA, Université Paris-Saclay, Jouy-en-Josas, France
| | - Jean Kanellopoulos
- Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette cedex, France
| | - Sirje Rüütel Boudinot
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn, Estonia.
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54
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Metzger MW, Walser SM, Aprile-Garcia F, Dedic N, Chen A, Holsboer F, Arzt E, Wurst W, Deussing JM. Genetically dissecting P2rx7 expression within the central nervous system using conditional humanized mice. Purinergic Signal 2017; 13:153-170. [PMID: 27858314 PMCID: PMC5432476 DOI: 10.1007/s11302-016-9546-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 10/26/2016] [Indexed: 12/16/2022] Open
Abstract
The purinergic P2X7 receptor (P2X7R) has attracted considerable interest as a potential target for various central nervous system (CNS) pathologies including affective and neurodegenerative disorders. To date, the distribution and cellular localization of the P2X7R in the brain are not fully resolved and a matter of debate mainly due to the limitations of existing tools. However, this knowledge should be a prerequisite for understanding the contribution of the P2X7R to brain disease. Here, we generated a genetic mouse model by humanizing the P2X7R in the mouse as mammalian model organism. We demonstrated its functionality and revealed species-specific characteristics of the humanized receptor, compared to the murine ortholog, regarding its receptivity to activation and modulation by 2',3'-O-(benzoyl-4-benzoyl)-adenosine 5'-triphosphate (BzATP) and trifluoperazine (TFP). This humanized P2rx7 allele is accessible to spatially and temporally controlled Cre recombinase-mediated inactivation. In contrast to previously generated knockout (KO) mice, none of the described P2rx7 splice variants evade this null allele. By selective disruption and assessment of human P2RX7 expression in different brain regions and cell types, we were able to demonstrate that the P2X7R is specifically expressed in glutamatergic pyramidal neurons of the hippocampus. Also, P2X7R is expressed in major non-neuronal lineages throughout the brain, i.e., astrocytes, oligodendrocytes, and microglia. In conclusion, this humanized mouse model provides the means for detailed assessment of human P2X7R function in vivo including evaluation of agonists or antagonists. In addition, this conditional allele will enable future loss-of-function studies in conjunction with mouse models for CNS disorders.
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Affiliation(s)
| | | | - Fernando Aprile-Garcia
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
- Max Planck Institute of Immunbiology and Epigenetics, 79108, Freiburg, Germany
| | - Nina Dedic
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
| | - Alon Chen
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
- Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Developmental Genetics, 85764, Neuherberg, Germany
| | - Florian Holsboer
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
- HMNC Brain Health, 80539, Munich, Germany
| | - Eduardo Arzt
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Wolfgang Wurst
- German Center for Neurodegenerative Diseases (DZNE), Site Munich, 81377, Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Adolf-Butenandt-Institut, Ludwig-Maximilians-Universität München, 80336, Munich, Germany
- Department of Neurobiology, Weizmann Institute of Science, 7610001, Rehovot, Israel
- Chair of Developmental Genetics c/o Helmholtz Zentrum München, Technische Universität München-Weihenstephan, 85764, Neuherberg, Germany
| | - Jan M Deussing
- Max Planck Institute of Psychiatry, 80804, Munich, Germany.
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55
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Sadovnick AD, Gu BJ, Traboulsee AL, Bernales CQ, Encarnacion M, Yee IM, Criscuoli MG, Huang X, Ou A, Milligan CJ, Petrou S, Wiley JS, Vilariño-Güell C. Purinergic receptors P2RX4 and P2RX7 in familial multiple sclerosis. Hum Mutat 2017; 38:736-744. [PMID: 28326637 DOI: 10.1002/humu.23218] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 03/08/2017] [Accepted: 03/16/2017] [Indexed: 12/11/2022]
Abstract
Genetic variants in the purinergic receptors P2RX4 and P2RX7 have been shown to affect susceptibility to multiple sclerosis (MS). In this study, we set out to evaluate whether rare coding variants of major effect could also be identified in these purinergic receptors. Sequencing analysis of P2RX4 and P2RX7 in 193 MS patients and 100 controls led to the identification of a rare three variant haplotype (P2RX7 rs140915863:C>T [p.T205M], P2RX7 rs201921967:A>G [p.N361S], and P2RX4 rs765866317:G>A [p.G135S]) segregating with disease in a multi-incident family with six family members diagnosed with MS (logarithm of odds = 3.07). Functional analysis of this haplotype in HEK293 cells revealed impaired P2X7 surface expression (P < 0.01), resulting in over 95% inhibition of adenosine triphosphate (ATP)-induced pore function (P < 0.001) and a marked reduction in phagocytic ability (P < 0.05). In addition, transfected cells showed 40% increased peak ATP-induced inward current (P < 0.01), and a greater Ca2+ response to the P2X4 135S variant compared with wild type (P < 0.0001). Our study nominates rare genetic variants in P2RX4 and P2RX7 as major genetic contributors to disease, further supporting a role for these purinergic receptors in MS and the disruption of transmembrane cation channels leading to impairment of phagocytosis as the pathological mechanisms of disease.
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Affiliation(s)
- A Dessa Sadovnick
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada.,Division of Neurology, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Ben J Gu
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Anthony L Traboulsee
- Division of Neurology, Faculty of Medicine, University of British Columbia, Vancouver, Canada
| | - Cecily Q Bernales
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Mary Encarnacion
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Irene M Yee
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Maria G Criscuoli
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
| | - Xin Huang
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Amber Ou
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Carol J Milligan
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Steven Petrou
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - James S Wiley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
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56
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Abstract
The P2X7 receptor is a trimeric ion channel gated by extracellular adenosine 5'-triphosphate. The receptor is present on an increasing number of different cells types including stem, blood, glial, neural, ocular, bone, dental, exocrine, endothelial, muscle, renal and skin cells. The P2X7 receptor induces various downstream events in a cell-specific manner, including inflammatory molecule release, cell proliferation and death, metabolic events, and phagocytosis. As such this receptor plays important roles in heath and disease. Increasing knowledge about the P2X7 receptor has been gained from studies of, but not limited to, protein chemistry including cloning, site-directed mutagenesis, crystal structures and atomic modeling, as well as from studies of primary tissues and transgenic mice. This chapter focuses on the P2X7 receptor itself. This includes the P2RX7 gene and its products including splice and polymorphic variants. This chapter also reviews modulators of P2X7 receptor activation and inhibition, as well as the transcriptional regulation of the P2RX7 gene via its promoter and enhancer regions, and by microRNA and long-coding RNA. Furthermore, this chapter discusses the post-translational modification of the P2X7 receptor by N-linked glycosylation, adenosine 5'-diphosphate ribosylation and palmitoylation. Finally, this chapter reviews interaction partners of the P2X7 receptor, and its cellular localisation and trafficking within cells.
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Affiliation(s)
- Ronald Sluyter
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia. .,Centre for Medical and Molecular Bioscience, University of Wollongong, Wollongong, NSW, 2522, Australia. .,Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia.
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57
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Gicquel T, Le Daré B, Boichot E, Lagente V. Purinergic receptors: new targets for the treatment of gout and fibrosis. Fundam Clin Pharmacol 2016; 31:136-146. [PMID: 27885718 DOI: 10.1111/fcp.12256] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 11/02/2016] [Accepted: 11/18/2016] [Indexed: 12/11/2022]
Abstract
Adenosine triphosphate is involved in many metabolic reactions, but it has also a role as a cellular danger signal transmitted through purinergic receptors (PRs). Indeed, adenosine 5'-triphosphate (ATP) can bind to PRs which are found in the membrane of many cell types, although the relative proportions of the receptor subtypes differ. PRs are classified according to genetic and pharmacological criteria and especially their affinities for agonists and their transduction mechanism (i.e. as metabotropic P2YRs or ionotropic P2XRs). Extracellular ATP release by activated or necrotic cells may activate various PRs and especially P2X7R, the best-characterized PR, on immune cells. P2X7R is known to regulate the activation of the Nod-like receptor (NLR)-family protein, NLRP3 inflammasome, which permit the release of IL-1β, a potent pro-inflammatory cytokine. The P2X7R/NLRP3 pathway is involved in many inflammatory diseases, such as gout, and in fibrosis diseases associated with inflammatory process, liver or lung fibrosis. Some authors imaging also a real promising therapeutic potential of P2X7R blockage. Thus, several pharmaceutical companies have developed P2X7R antagonists as novel anti-inflammatory drug candidates. Clinical trials of the efficacy of these antagonists are now underway. A better understanding of the P2X7R/NLRP3 signalling pathways permits the identification of targets and the development of a new class of drugs able to inhibit the fibrogenesis process and collagen deposition.
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Affiliation(s)
- Thomas Gicquel
- Laboratoire de toxicologie biologique et médico-légale, CHU Rennes, F-35033, Rennes, France.,UMR991 INSERM, Faculté de Pharmacie, Université Rennes 1, F-35043, Rennes, France
| | - Brendan Le Daré
- UMR991 INSERM, Faculté de Pharmacie, Université Rennes 1, F-35043, Rennes, France.,CHU Rennes, Pôle Pharmacie, F-35033, Rennes, France
| | - Elisabeth Boichot
- UMR991 INSERM, Faculté de Pharmacie, Université Rennes 1, F-35043, Rennes, France
| | - Vincent Lagente
- UMR991 INSERM, Faculté de Pharmacie, Université Rennes 1, F-35043, Rennes, France
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58
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Yoshida K, Ito M, Matsuoka I. Divergent regulatory roles of extracellular ATP in the degranulation response of mouse bone marrow-derived mast cells. Int Immunopharmacol 2016; 43:99-107. [PMID: 27988461 DOI: 10.1016/j.intimp.2016.12.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/25/2016] [Accepted: 12/09/2016] [Indexed: 02/06/2023]
Abstract
Mast cells (MCs) play a critical role in allergic inflammation. Although purinergic signalling is implicated in the regulation of various immune responses, its role in MC function is not fully understood. In this study, we investigated the regulatory role of purinergic signalling in MC degranulation, using mouse bone marrow-derived mast cells (BMMCs). Notably, BMMCs expressed various functional P2 adenosine triphosphate (ATP) receptors, including ionotropic P2X4 and P2X7, involved in the regulation of BMMC degranulation. Thus, P2X7 receptor activation induced a marked degranulation from BMMCs directly. Although P2X4 receptor activation did not independently induce degranulation, it significantly potentiated the degranulation triggered by antigen-induced, high-affinity IgE receptor (FcεRI) stimulation. In addition, ATP synergistically augmented degranulation induced by adenosine A3 receptor activation. Moreover, BMMCs highly expressed ecto-nucleotidase CD39, but not ecto-5'-nucleotidase (CD73), and were therefore unable to directly convert ATP to adenosine. However, in the presence of CD73-expressing cells, ATP-mediated BMMC stimulation caused a marked degranulation in a CD73- and adenosine-dependent manner. These results demonstrate that purinergic signalling plays an important role in MC degranulation through at least three distinct mechanisms: (1) higher ATP concentrations directly induce degranulation via P2X7 receptor activation, (2) lower ATP concentrations augment FcεRI-mediated degranulation via P2X4 receptor activation, and (3) in an ecto-nucleotidase-enrich environment, ATP and the converted product adenosine induce a synergistic degranulation by P1 and P2 receptor co-activation.
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Affiliation(s)
- Kazuki Yoshida
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, 60 Nakaorui-machi, Takasaki-shi, Gunma 370-0033, Japan
| | - Masaaki Ito
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, 60 Nakaorui-machi, Takasaki-shi, Gunma 370-0033, Japan
| | - Isao Matsuoka
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, 60 Nakaorui-machi, Takasaki-shi, Gunma 370-0033, Japan.
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59
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Purinergic signalling in autoimmunity: A role for the P2X7R in systemic lupus erythematosus? Biomed J 2016; 39:326-338. [PMID: 27884379 PMCID: PMC6138817 DOI: 10.1016/j.bj.2016.08.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 07/29/2016] [Accepted: 08/08/2016] [Indexed: 12/11/2022] Open
Abstract
Purinergic signalling plays a crucial role in immunity and autoimmunity. Among purinergic receptors, the P2X7 receptor (P2X7R) has an undisputed role as it is expressed to high level by immune cells, triggers cytokine release and modulates immune cell differentiation. In this review, we focus on evidence supporting a possible role of the P2X7R in the pathogenesis of systemic lupus erythematosus (SLE).
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60
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Menzies RI, Tam FW, Unwin RJ, Bailey MA. Purinergic signaling in kidney disease. Kidney Int 2016; 91:315-323. [PMID: 27780585 DOI: 10.1016/j.kint.2016.08.029] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 08/10/2016] [Accepted: 08/15/2016] [Indexed: 02/04/2023]
Abstract
Nucleotides are key subunits for nucleic acids and provide energy for intracellular metabolism. They can also be released from cells to act physiologically as extracellular messengers or pathologically as danger signals. Extracellular nucleotides stimulate membrane receptors in the P2 and P1 family. P2X are ATP-activated cation channels; P2Y and P1 are G-protein coupled receptors activated by ATP, ADP, UTP, and UDP in the case of P2 or adenosine for P1. Renal P2 receptors influence both vascular contractility and tubular function. Renal cells also express ectonucleotidases that rapidly hydrolyze extracellular nucleotides. These enzymes integrate this multireceptor purinergic-signaling complex by determining the nucleotide milieu to titrate receptor activation. Purinergic signaling also regulates immune cell function by modulating the synthesis and release of various cytokines such as IL1-β and IL-18 as part of inflammasome activation. Abnormal or excessive stimulation of this intricate paracrine system can be pro- or anti-inflammatory, and is also linked to necrosis and apoptosis. Kidney tissue injury causes a localized increase in ATP concentration, and sustained activation of P2 receptors can lead to renal glomerular, tubular, and vascular cell damage. Purinergic receptors also regulate the activity and proliferation of fibroblasts, promoting both inflammation and fibrosis in chronic disease. In this short review we summarize some of the recent findings related to purinergic signaling in the kidney. We focus predominantly on the P2X7 receptor, discussing why antagonists have so far disappointed in clinical trials and how advances in our understanding of purinergic signaling might help to reposition these compounds as potential treatments for renal disease.
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Affiliation(s)
- Robert I Menzies
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, Edinburgh, Scotland, UK
| | - Frederick W Tam
- Imperial College Renal and Transplant Centre, Department of Medicine, Imperial College London, UK
| | - Robert J Unwin
- Cardiovascular and Metabolic Diseases Biotech Unit, AstraZeneca Gothenburg, Sweden; UCL Centre for Nephrology, University College London, London, UK.
| | - Matthew A Bailey
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, Edinburgh, Scotland, UK
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61
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Davis CJ, Taishi P, Honn KA, Koberstein JN, Krueger JM. P2X7 receptors in body temperature, locomotor activity, and brain mRNA and lncRNA responses to sleep deprivation. Am J Physiol Regul Integr Comp Physiol 2016; 311:R1004-R1012. [PMID: 27707719 DOI: 10.1152/ajpregu.00167.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/30/2016] [Accepted: 09/30/2016] [Indexed: 12/17/2022]
Abstract
The ionotropic purine type 2X7 receptor (P2X7R) is a nonspecific cation channel implicated in sleep regulation and brain cytokine release. Many endogenous rhythms covary with sleep, including locomotor activity and core body temperature. Furthermore, brain-hypothalamic cytokines and purines play a role in the regulation of these physiological parameters as well as sleep. We hypothesized that these parameters are also affected by the absence of the P2X7 receptor. Herein, we determine spontaneous expression of body temperature and locomotor activity in wild-type (WT) and P2X7R knockout (KO) mice and how they are affected by sleep deprivation (SD). We also compare hypothalamic, hippocampal, and cortical cytokine- and purine-related receptor and enzyme mRNA expressions before and after SD in WT and P2X7RKO mice. Next, in a hypothesis-generating survey of hypothalamic long noncoding (lnc) RNAs, we compare lncRNA expression levels between strains and after SD. During baseline conditions, P2X7RKO mice had attenuated temperature rhythms compared with WT mice, although locomotor activity patterns were similar in both strains. After 6 h of SD, body temperature and locomotion were enhanced to a greater extent in P2X7RKO mice than in WT mice during the initial 2-3 h after SD. Baseline mRNA levels of cortical TNF-α and P2X4R were higher in the KO mice than WT mice. In response to SD, the KO mice failed to increase hypothalamic adenosine deaminase and P2X4R mRNAs. Further, hypothalamic lncRNA expressions varied by strain, and with SD. Current data are consistent with a role for the P2X7R in thermoregulation and lncRNA involvement in purinergic signaling.
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Affiliation(s)
- Christopher J Davis
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University-Spokane, Spokane, Washington; .,Sleep and Performance Research Center, Washington State University-Spokane, Spokane, Washington.,Program in Neuroscience, Washington State University-Spokane, Spokane, Washington; and
| | - Ping Taishi
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University-Spokane, Spokane, Washington
| | - Kimberly A Honn
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University-Spokane, Spokane, Washington.,Sleep and Performance Research Center, Washington State University-Spokane, Spokane, Washington.,Elson S. Floyd College of Medicine, Department of Medical Education and Clinical Sciences, Washington State University-Spokane, Spokane, Washington
| | - John N Koberstein
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University-Spokane, Spokane, Washington
| | - James M Krueger
- Elson S. Floyd College of Medicine, Department of Biomedical Sciences, Washington State University-Spokane, Spokane, Washington.,Program in Neuroscience, Washington State University-Spokane, Spokane, Washington; and
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62
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Role of the purinergic signaling in epilepsy. Pharmacol Rep 2016; 69:130-138. [PMID: 27915186 DOI: 10.1016/j.pharep.2016.09.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/20/2016] [Accepted: 09/21/2016] [Indexed: 01/19/2023]
Abstract
Adenine nucleotides and adenosine are signaling molecules that activate purinergic receptors P1 and P2. Activation of A1 adenosine receptors has an anticonvulsant action, whereas activation of A2A receptors might initiate seizures. Therefore, a significant limitation to the use of A1 receptor agonists as drugs in the CNS might be their peripheral side effects. The anti-epileptic activity of adenosine is related to its increased concentration outside the cell. This increase might result from the inhibition of the equilibrative nucleoside transporters (ENTs). Moreover, the implantation of implants or stem cells into the brain might cause slow and persistent increases in adenosine concentrations in the extracellular spaces of the brain. The role of adenosine in seizure inhibition has been confirmed by results demonstrating that in patients with epilepsy, the adenosine kinase (ADK) present in astrocytes is the only purine-metabolizing enzyme that exhibits increased expression. Increased ADK activity causes intensified phosphorylation of adenosine to 5'-AMP, which therefore lowers the adenosine level in the extracellular spaces. These changes might initiate astrogliosis and epileptogenesis, which are the manifestations of epilepsy. Seizures might induce inflammatory processes and vice versa. Activation of P2X7 receptors causes intensified release of pro-inflammatory cytokines (IL-1β and TNF-α) and activates metabolic pathways that induce inflammatory processes in the CNS. Therefore, antagonists of P2X7 and the interleukin 1β receptor might be efficient drugs for recurring seizures and prolonged status epilepticus. Inhibitors of ADK would simultaneously inhibit the seizures, prevent the astrogliosis and epileptogenesis processes and prevent the formation of new epileptogenic foci. Therefore, these drugs might become beneficial seizure-suppressing drugs.
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63
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Aprile-Garcia F, Metzger MW, Paez-Pereda M, Stadler H, Acuña M, Liberman AC, Senin SA, Gerez J, Hoijman E, Refojo D, Mitkovski M, Panhuysen M, Stühmer W, Holsboer F, Deussing JM, Arzt E. Co-Expression of Wild-Type P2X7R with Gln460Arg Variant Alters Receptor Function. PLoS One 2016; 11:e0151862. [PMID: 26986975 PMCID: PMC4795689 DOI: 10.1371/journal.pone.0151862] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 03/04/2016] [Indexed: 01/04/2023] Open
Abstract
The P2X7 receptor is a member of the P2X family of ligand-gated ion channels. A single-nucleotide polymorphism leading to a glutamine (Gln) by arginine (Arg) substitution at codon 460 of the purinergic P2X7 receptor (P2X7R) has been associated with mood disorders. No change in function (loss or gain) has been described for this SNP so far. Here we show that although the P2X7R-Gln460Arg variant per se is not compromised in its function, co-expression of wild-type P2X7R with P2X7R-Gln460Arg impairs receptor function with respect to calcium influx, channel currents and intracellular signaling in vitro. Moreover, co-immunoprecipitation and FRET studies show that the P2X7R-Gln460Arg variant physically interacts with P2X7R-WT. Specific silencing of either the normal or polymorphic variant rescues the heterozygous loss of function phenotype and restores normal function. The described loss of function due to co-expression, unique for mutations in the P2RX7 gene so far, explains the mechanism by which the P2X7R-Gln460Arg variant affects the normal function of the channel and may represent a mechanism of action for other mutations.
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Affiliation(s)
- Fernando Aprile-Garcia
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
- Departamento de Fisiología y Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | | | | | - Matías Acuña
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Ana C. Liberman
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Sergio A. Senin
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Juan Gerez
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
| | - Esteban Hoijman
- Centro de Microscopías Avanzadas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Damian Refojo
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
| | - Mišo Mitkovski
- Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | | | - Walter Stühmer
- Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Florian Holsboer
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
- HMNC Brain Health, Munich, Germany
| | | | - Eduardo Arzt
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA)-CONICET- Partner Institute of the Max Planck Society, Buenos Aires, Argentina
- Departamento de Fisiología y Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
- Max Planck Institute of Psychiatry, 80804, Munich, Germany
- * E-mail:
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64
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Mittal R, Chan B, Grati M, Mittal J, Patel K, Debs LH, Patel AP, Yan D, Chapagain P, Liu XZ. Molecular Structure and Regulation of P2X Receptors With a Special Emphasis on the Role of P2X2 in the Auditory System. J Cell Physiol 2015; 231:1656-70. [PMID: 26627116 DOI: 10.1002/jcp.25274] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 12/01/2015] [Indexed: 12/23/2022]
Abstract
The P2X purinergic receptors are cation-selective channels gated by extracellular adenosine 5'-triphosphate (ATP). These purinergic receptors are found in virtually all mammalian cell types and facilitate a number of important physiological processes. Within the past few years, the characterization of crystal structures of the zebrafish P2X4 receptor in its closed and open states has provided critical insights into the mechanisms of ligand binding and channel activation. Understanding of this gating mechanism has facilitated to design and interpret new modeling and structure-function experiments to better elucidate how different agonists and antagonists can affect the receptor with differing levels of potency. This review summarizes the current knowledge on the structure, activation, allosteric modulators, function, and location of the different P2X receptors. Moreover, an emphasis on the P2X2 receptors has been placed in respect to its role in the auditory system. In particular, the discovery of three missense mutations in P2X2 receptors could become important areas of study in the field of gene therapy to treat progressive and noise-induced hearing loss. J. Cell. Physiol. 231: 1656-1670, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Rahul Mittal
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Brandon Chan
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - M'hamed Grati
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Jeenu Mittal
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Kunal Patel
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Luca H Debs
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Amit P Patel
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Denise Yan
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida
| | - Prem Chapagain
- Department of Physics, Florida International University, Miami, Florida.,Biomolecular Science Institute, Florida International University, Miami, Florida
| | - Xue Zhong Liu
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, Florida.,Department of Human Genetics, University of Miami Miller School of Medicine, Miami, Florida.,Department of Biochemistry, University of Miami Miller School of Medicine, Miami, Florida
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65
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Crain JM, Watters JJ. Microglial P2 Purinergic Receptor and Immunomodulatory Gene Transcripts Vary By Region, Sex, and Age in the Healthy Mouse CNS. ACTA ACUST UNITED AC 2015; 3. [PMID: 26949719 DOI: 10.4172/2329-8936.1000124] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Inflammatory damage in many neurodegenerative diseases is restricted to certain regions of the CNS, and while microglia have long been implicated in the pathology of many of these disorders, information comparing their gene expression in different CNS regions is lacking. Here we tested the hypothesis that the expression of purinergic receptors, estrogen receptors and other neuroprotective and pro-inflammatory genes differed among CNS regions in healthy mice. Because neurodegenerative diseases vary in incidence by sex and age, we also examined the regional distribution of these genes in male and female mice of four different ages between 21 days and 12 months. We postulated that pro-inflammatory gene expression would be higher in older animals, and lower in young adult females. We found that microglial gene expression differed across the CNS. Estrogen receptor alpha (Esr1) mRNA levels were often lower in microglia from the brainstem/spinal cord than from the cortex, whereas tumor necrosis factor alpha (Tnfα) expression was several times higher. In addition, the regional pattern of gene expression often changed with animal age; for example, no regional differences in P2X7 mRNA levels were detected in 21 day-old animals, but at 7 weeks and older, expression was highest in cerebellar microglia. Lastly, the expression of some genes was sexually dimorphic. In microglia from 12 month-old animals, mRNA levels of inducible nitric oxide synthase, but not Tnfα, were higher in females than males. These data suggest that microglial gene expression is not uniformly more pro-inflammatory in males or older animals. Moreover, microglia from CNS regions in which neuronal damage predominates in neurodegenerative disease do not generally express more pro-inflammatory genes than microglia from regions less frequently affected. This study provides an in-depth assessment of regional-, sex- and age-dependent differences in key microglial transcripts from the healthy mouse CNS.
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Affiliation(s)
- Jessica M Crain
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI 53706; Center for Women's Health Research, University of Wisconsin, Madison, WI 53706
| | - Jyoti J Watters
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI 53706; Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI 53706; Center for Women's Health Research, University of Wisconsin, Madison, WI 53706
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66
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Pérez-Flores G, Lévesque SA, Pacheco J, Vaca L, Lacroix S, Pérez-Cornejo P, Arreola J. The P2X7/P2X4 interaction shapes the purinergic response in murine macrophages. Biochem Biophys Res Commun 2015; 467:484-90. [DOI: 10.1016/j.bbrc.2015.10.025] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 10/05/2015] [Indexed: 01/01/2023]
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67
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Li Q, Fu W, Yao J, Ji Z, Wang Y, Zhou Z, Yan J, Li W. Heme induces IL-1β secretion through activating NLRP3 in kidney inflammation. Cell Biochem Biophys 2015; 69:495-502. [PMID: 24464629 DOI: 10.1007/s12013-014-9823-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To produce proinflammatory master cytokine IL-1β in macrophages, two stimulation pathways are needed including TLRs-NF-κB axis and NLRPs/ASC-caspase-1 axis. Different signals including exogenous and endogenous trigger inflammatory response distinctly. Among them, the role of endogenous stimulators of inflammation is poorly understood. As a component of hemoglobin, free heme is released when hemolysis or extensive cell damage occur which results in inflammatory response. Here, we find that heme induces IL-1β secretion through activating NLRP3 inflammasome in macrophages. Heme activates NLRP3 through P2X receptors, especially the P2X7R and P2X4R. Most importantly, significantly enhancement of heme level and activation of NLRPs/ASC-caspase-1 axis were observed in mice kidney after unilateral ureteral obstruction which could be inhibited by enforced expression of heme oxygenase-1 (HO-1). Our study proves that heme is a potential danger activator of NLRP3 inflammasome that plays an essential role in IL-1β secretion during kidney inflammation and provides new insight into the mechanism of innate immune initiation. Further investigation will be beneficial to develop new molecular target and molecular diagnosis indicator in therapy of kidney inflammation.
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Affiliation(s)
- Qianwei Li
- Department of Urology, Southwest Hospital, Third Military Medical University, 30, Gao TanYan, Chongqing, 400038, People's Republic of China
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68
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Cao Q, Zhong XZ, Zou Y, Murrell-Lagnado R, Zhu MX, Dong XP. Calcium release through P2X4 activates calmodulin to promote endolysosomal membrane fusion. J Cell Biol 2015; 209:879-94. [PMID: 26101220 PMCID: PMC4477861 DOI: 10.1083/jcb.201409071] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
P2X4 and calmodulin form a signaling complex in late endosomes and lysosomes that promotes fusion and vacuolation in a Ca2+-dependent fashion. Intra-endolysosomal Ca2+ release is required for endolysosomal membrane fusion with intracellular organelles. However, the molecular mechanisms for intra-endolysosomal Ca2+ release and the downstream Ca2+ targets involved in the fusion remain elusive. Previously, we demonstrated that endolysosomal P2X4 forms channels activated by luminal adenosine triphosphate in a pH-dependent manner. In this paper, we show that overexpression of P2X4, as well as increasing endolysosomal P2X4 activity by alkalinization of endolysosome lumen, promoted vacuole enlargement in cells and endolysosome fusion in a cell-free assay. These effects were prevented by inhibiting P2X4, expressing a dominant-negative P2X4 mutant, and disrupting the P2X4 gene. We further show that P2X4 and calmodulin (CaM) form a complex at endolysosomal membrane where P2X4 activation recruits CaM to promote fusion and vacuolation in a Ca2+-dependent fashion. Moreover, P2X4 activation-triggered fusion and vacuolation were suppressed by inhibiting CaM. Our data thus suggest a new molecular mechanism for endolysosomal membrane fusion involving P2X4-mediated endolysosomal Ca2+ release and subsequent CaM activation.
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Affiliation(s)
- Qi Cao
- Department of Physiology and Biophysics, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
| | - Xi Zoë Zhong
- Department of Physiology and Biophysics, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
| | - Yuanjie Zou
- Department of Physiology and Biophysics, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
| | - Ruth Murrell-Lagnado
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
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69
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Kowalski M, Hausmann R, Schmid J, Dopychai A, Stephan G, Tang Y, Schmalzing G, Illes P, Rubini P. Flexible subunit stoichiometry of functional human P2X2/3 heteromeric receptors. Neuropharmacology 2015; 99:115-30. [PMID: 26184350 DOI: 10.1016/j.neuropharm.2015.07.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 07/01/2015] [Accepted: 07/09/2015] [Indexed: 11/27/2022]
Abstract
The aim of the present work was to clarify whether heterotrimeric P2X2/3 receptors have a fixed subunit stoichiometry consisting of one P2X2 and two P2X3 subunits as previously suggested, or a flexible stoichiometry containing also the inverse subunit composition. For this purpose we transfected HEK293 cells with P2X2 and P2X3 encoding cDNA at the ratios of 1:2 and 4:1, and analysed the biophysical and pharmacological properties of the generated receptors by means of the whole-cell patch-clamp technique. The concentration-response curves for the selective agonist α,β-meATP did not differ from each other under the two transfection ratios. However, co-expression of an inactive P2X2 mutant and the wild type P2X3 subunit and vice versa resulted in characteristic distortions of the α,β-meATP concentration-response relationships, depending on which subunit was expressed in excess, suggesting that HEK293 cells express mixtures of (P2X2)1/(P2X3)2 and (P2X2)2/(P2X3)1 receptors. Whereas the allosteric modulators H+ and Zn2+ failed to discriminate between the two possible heterotrimeric receptor variants, the α,β-meATP-induced responses were blocked more potently by the competitive antagonist A317491, when the P2X2 subunit was expressed in deficit of the P2X3 subunit. Furthermore, blue-native PAGE analysis of P2X2 and P2X3 subunits co-expressed in Xenopus laevis oocytes and HEK293 cells revealed that plasma membrane-bound P2X2/3 receptors appeared in two clearly distinct heterotrimeric complexes: a (P2X2-GFP)2/(P2X3)1 complex and a (P2X2-GFP)1/(P2X3)2 complex. These data strongly indicate that the stoichiometry of the heteromeric P2X2/3 receptor is not fixed, but determined in a permutational manner by the relative availability of P2X2 and P2X3 subunits.
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Affiliation(s)
- Maria Kowalski
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Ralf Hausmann
- Molecular Pharmacology, RWTH Aachen University, 52074 Aachen, Germany
| | - Julia Schmid
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Anke Dopychai
- Molecular Pharmacology, RWTH Aachen University, 52074 Aachen, Germany
| | - Gabriele Stephan
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Yong Tang
- Acupuncture and Tuina School, Chengdu University of Traditional Chinese Medicine, 610075 Chengdu, China
| | | | - Peter Illes
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Patrizia Rubini
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany.
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70
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Gicquel T, Robert S, Loyer P, Victoni T, Bodin A, Ribault C, Gleonnec F, Couillin I, Boichot E, Lagente V. ILr1β production is dependent on the activation of purinergic receptors and NLRP3 pathway in human macrophages. FASEB J 2015; 29:4162-73. [DOI: 10.1096/fj.14-267393] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 06/15/2015] [Indexed: 01/01/2023]
Affiliation(s)
- Thomas Gicquel
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
- Laboratoire de Toxicologie Biologique et Médico‐LégaleCentre Hospitalier Universitaire de RennesRennesFrance
| | - Sacha Robert
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Pascal Loyer
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Tatiana Victoni
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Aude Bodin
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Catherine Ribault
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Florence Gleonnec
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Isabelle Couillin
- Experimental and Molecular Immunology and NeurogeneticsCentre National de la Recherche Scientifique, Unité Mixte de Recherche 7355, Université d'OrleansOrleansFrance
| | - Elisabeth Boichot
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
| | - Vincent Lagente
- Unité Mixte de Recherche 991Institut National de la Santé et de la Recherche MédicaleUniversité de Rennes 1RennesFrance
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71
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Howarth AR, Conway BR, Bailey MA. Vascular and inflammatory actions of P2X receptors in renal injury. Auton Neurosci 2015; 191:135-40. [PMID: 25998687 DOI: 10.1016/j.autneu.2015.05.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
P2 purinergic receptors are activated by extracellular ATP and subserve a plethora of roles in the body, including metabolism, inflammation and neuronal signalling. This review focuses on renal purinergic receptors and how different roles that they play may contribute to renal dysfunction and the progression of chronic kidney disease. Numerous studies have linked P2 receptors, particularly the P2X4R and P2X7R subtypes, to kidney injury and damage. However, the mechanisms underlying this association are not fully defined. Several studies show that activation of P2X4R and particularly P2X7R can have a pro-inflammatory effect, causing or exacerbating damage to renal tissue. However, clinical trials aiming to utilise P2X7R antagonists to treat inflammatory disease have been unsuccessful, and it is possible that other mechanisms besides inflammation tie P2X7R activation to disease progression. In this context, purinergic signalling is also involved in the control of vascular tone and our recent studies suggest that activation of P2X4R/P2X7R causes renal vascular dysfunction and contributes to chronic kidney disease. This brief review aims to summarise the complementary inflammatory and vascular roles of P2X receptors in the kidney, with emphasis on the subtypes P2X4R and P27XR, and how each contributes to and presents therapeutic targets in the progression of chronic kidney disease.
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Affiliation(s)
- Amelia R Howarth
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, United Kingdom
| | - Bryan R Conway
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, United Kingdom
| | - Matthew A Bailey
- British Heart Foundation Centre for Cardiovascular Science, The University of Edinburgh, United Kingdom.
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72
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Pippel A, Beßler B, Klapperstück M, Markwardt F. Inhibition of antigen receptor-dependent Ca(2+) signals and NF-AT activation by P2X7 receptors in human B lymphocytes. Cell Calcium 2015; 57:275-89. [PMID: 25678443 DOI: 10.1016/j.ceca.2015.01.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/19/2015] [Accepted: 01/21/2015] [Indexed: 12/22/2022]
Abstract
One of the first intracellular signals after antigen binding by the antigen receptor of B lymphocytes is the increased intracellular Ca(2+) concentration ([Ca(2+)]i), which is followed by several intracellular signaling events like the nuclear translocation of the transcription factor NF-AT controlling the fate of B lymphocytes after their activation. Extracellular ATP, which is released from cells under several pathological conditions, is considered a danger-associated signal serving as an immunomodulator. We investigated the interaction of antigen receptor (BCR) and P2X7 receptor (P2X7R) activation on [Ca(2+)]i signaling and on nuclear translocation of the transcription factor NF-AT in human B lymphocytes. Although the P2X7R is an ATP-gated Ca(2+)-permeable ion channel, P2X7R activation inhibits the BCR-mediated [Ca(2+)]i responses. This effect is mimicked by cell membrane depolarization induced by an increase in the extracellular K(+) concentration or by application of the Na(+) ionophore gramicidin, but is abolished by stabilization of the membrane potential using the K(+) ionophore valinomycin, by extracellular Mg(2+), which is known to inhibit P2X7R-dependent effects, or by replacing Na(+) by the less P2X7R-permeable Tris(+) ion. Furthermore, P2X7R activation by ATP inhibits the BCR-dependent translocation of the transcription factor NF-ATc1 to the nucleus. We therefore conclude that extracellular ATP via the P2X7R mediates inhibitory effects on B cell activation. This may be of relevance for understanding of the activation of the BCR under pathological conditions and for the development of therapeutic strategies targeting human B lymphocytes or P2X7 receptors.
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Affiliation(s)
- Anja Pippel
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Straße 6, D-06097 Halle (Saale), Germany
| | - Björn Beßler
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Straße 6, D-06097 Halle (Saale), Germany
| | - Manuela Klapperstück
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Straße 6, D-06097 Halle (Saale), Germany
| | - Fritz Markwardt
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Straße 6, D-06097 Halle (Saale), Germany.
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73
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Ase AR, Honson NS, Zaghdane H, Pfeifer TA, Séguéla P. Identification and characterization of a selective allosteric antagonist of human P2X4 receptor channels. Mol Pharmacol 2015; 87:606-16. [PMID: 25597706 DOI: 10.1124/mol.114.096222] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
P2X4 is an ATP-gated nonselective cation channel highly permeable to calcium. There is increasing evidence that this homomeric purinoceptor, which is expressed in several neuronal and immune cell types, is involved in chronic pain and inflammation. The current paucity of unambiguous pharmacological tools available to interrogate or modulate P2X4 function led us to pursue the search for selective antagonists. In the high-throughput screen of a compound library, we identified the phenylurea BX430 (1-(2,6-dibromo-4-isopropyl-phenyl)-3-(3-pyridyl)urea, molecular weight = 413), with antagonist properties on human P2X4-mediated calcium uptake. Patch-clamp electrophysiology confirmed direct inhibition of P2X4 currents by extracellular BX430, with submicromolar potency (IC50 = 0.54 µM). BX430 is highly selective, having virtually no functional impact on all other P2X subtypes, namely, P2X1-P2X3, P2X5, and P2X7, at 10-100 times its IC50. Unexpected species differences were noticed, as BX430 is a potent antagonist of zebrafish P2X4 but has no effect on rat and mouse P2X4 orthologs. The concentration-response curve for ATP on human P2X4 in the presence of BX430 shows an insurmountable blockade, indicating a noncompetitive allosteric mechanism of action. Using a fluorescent dye uptake assay, we observed that BX430 also effectively suppresses ATP-evoked and ivermectin-potentiated membrane permeabilization induced by P2X4 pore dilation. Finally, in single-cell calcium imaging, we validated its selective inhibitory effects on native P2X4 channels at the surface of human THP-1 cells that were differentiated into macrophages. In summary, this ligand provides a novel molecular probe to assess the specific role of P2X4 in inflammatory and neuropathic conditions, where ATP signaling has been shown to be dysfunctional.
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Affiliation(s)
- Ariel R Ase
- Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada (A.R.A., P.S.); Screening Division, The Centre for Drug Research and Discovery, Vancouver, Canada (N.S.H., T.A.P.); and Zamboni Chemical Solutions, Department of Chemistry, McGill University, Montreal, Canada (H.Z.)
| | - Nicolette S Honson
- Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada (A.R.A., P.S.); Screening Division, The Centre for Drug Research and Discovery, Vancouver, Canada (N.S.H., T.A.P.); and Zamboni Chemical Solutions, Department of Chemistry, McGill University, Montreal, Canada (H.Z.)
| | - Helmi Zaghdane
- Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada (A.R.A., P.S.); Screening Division, The Centre for Drug Research and Discovery, Vancouver, Canada (N.S.H., T.A.P.); and Zamboni Chemical Solutions, Department of Chemistry, McGill University, Montreal, Canada (H.Z.)
| | - Tom A Pfeifer
- Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada (A.R.A., P.S.); Screening Division, The Centre for Drug Research and Discovery, Vancouver, Canada (N.S.H., T.A.P.); and Zamboni Chemical Solutions, Department of Chemistry, McGill University, Montreal, Canada (H.Z.)
| | - Philippe Séguéla
- Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, Department of Neurology and Neurosurgery, McGill University, Montreal, Canada (A.R.A., P.S.); Screening Division, The Centre for Drug Research and Discovery, Vancouver, Canada (N.S.H., T.A.P.); and Zamboni Chemical Solutions, Department of Chemistry, McGill University, Montreal, Canada (H.Z.)
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Sperlágh B, Illes P. P2X7 receptor: an emerging target in central nervous system diseases. Trends Pharmacol Sci 2014; 35:537-47. [PMID: 25223574 DOI: 10.1016/j.tips.2014.08.002] [Citation(s) in RCA: 288] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 08/07/2014] [Accepted: 08/14/2014] [Indexed: 12/19/2022]
Abstract
The ATP-sensitive homomeric P2X7 receptor (P2X7R) has received particular attention as a potential drug target because of its widespread involvement in inflammatory diseases as a key regulatory element of the inflammasome complex. However, it has only recently become evident that P2X7Rs also play a pivotal role in central nervous system (CNS) pathology. There is an explosion of data indicating that genetic deletion and pharmacological blockade of P2X7Rs alter responsiveness in animal models of neurological disorders, such as stroke, neurotrauma, epilepsy, neuropathic pain, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease. Moreover, recent studies suggest that P2X7Rs regulate the pathophysiology of psychiatric disorders, including mood disorders, implicating P2X7Rs as drug targets in a variety of CNS pathology.
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Affiliation(s)
- Beáta Sperlágh
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1450 Budapest, Hungary.
| | - Peter Illes
- Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, D-04107 Leipzig, Germany
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75
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The purinergic system and glial cells: emerging costars in nociception. BIOMED RESEARCH INTERNATIONAL 2014; 2014:495789. [PMID: 25276794 PMCID: PMC4168030 DOI: 10.1155/2014/495789] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 07/08/2014] [Indexed: 12/23/2022]
Abstract
It is now well established that glial cells not only provide mechanical and trophic support to neurons but can directly contribute to neurotransmission, for example, by release and uptake of neurotransmitters and by secreting pro- and anti-inflammatory mediators. This has greatly changed our attitude towards acute and chronic disorders, paving the way for new therapeutic approaches targeting activated glial cells to indirectly modulate and/or restore neuronal functions. A deeper understanding of the molecular mechanisms and signaling pathways involved in neuron-to-glia and glia-to-glia communication that can be pharmacologically targeted is therefore a mandatory step toward the success of this new healing strategy. This holds true also in the field of pain transmission, where the key involvement of astrocytes and microglia in the central nervous system and satellite glial cells in peripheral ganglia has been clearly demonstrated, and literally hundreds of signaling molecules have been identified. Here, we shall focus on one emerging signaling system involved in the cross talk between neurons and glial cells, the purinergic system, consisting of extracellular nucleotides and nucleosides and their membrane receptors. Specifically, we shall summarize existing evidence of novel “druggable” glial purinergic targets, which could help in the development of innovative analgesic approaches to chronic pain states.
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76
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Immunolocalization of the P2X4 receptor on neurons and glia in the mammalian retina. Neuroscience 2014; 277:55-71. [DOI: 10.1016/j.neuroscience.2014.06.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 06/23/2014] [Accepted: 06/24/2014] [Indexed: 02/07/2023]
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Huang P, Zou Y, Zhong XZ, Cao Q, Zhao K, Zhu MX, Murrell-Lagnado R, Dong XP. P2X4 forms functional ATP-activated cation channels on lysosomal membranes regulated by luminal pH. J Biol Chem 2014; 289:17658-67. [PMID: 24817123 DOI: 10.1074/jbc.m114.552158] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P2X receptors are commonly known as plasma membrane cation channels involved in a wide variety of cell functions. The properties of these channels have been extensively studied on the plasma membrane. However, studies in amoeba suggest that P2X receptors are also present intracellularly and involved in vesicle fusion with the plasma membrane. Recently, it was shown that in addition to plasma membrane expression, mammalian P2X4 was also localized intracellularly in lysosomes. However, it was not clear whether the lysosomal P2X4 receptors function as channels and how they are activated and regulated. In this paper, we show that both P2X4 and its natural ligand, ATP, are enriched in lysosomes of COS1 and HEK293 cells. By directly recording membrane currents from enlarged lysosomal vacuoles, we demonstrated that lysosomal P2X4 formed channels activated by ATP from the luminal side in a pH-dependent manner. While the acidic pH at the luminal side inhibited P2X4 activity, increasing the luminal pH in the presence of ATP caused P2X4 activation. We further showed that, as for the plasma membrane P2X4, the lysosomal P2X4 was potentiated by ivermectin but insensitive to suramin and PPADS, and it permeated the large cation N-methyl-d-glucamine upon activation. Our data suggest that P2X4 forms functional ATP-activated cation channels on lysosomal membranes regulated by luminal pH. Together with the reported fusion effect of intracellular P2X in lower organisms, we speculate that the lysosome-localized P2X4 may play specific roles in membrane trafficking of acidic organelles in mammalian cells.
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Affiliation(s)
- Peng Huang
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada
| | - Yuanjie Zou
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada
| | - Xi Zoë Zhong
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada
| | - Qi Cao
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada
| | - Kexin Zhao
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada
| | - Michael X Zhu
- the Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, and
| | - Ruth Murrell-Lagnado
- the Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | - Xian-Ping Dong
- From the Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia B3H 4R2, Canada,
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78
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Kim MJ, Turner CM, Hewitt R, Smith J, Bhangal G, Pusey CD, Unwin RJ, Tam FWK. Exaggerated renal fibrosis in P2X4 receptor-deficient mice following unilateral ureteric obstruction. Nephrol Dial Transplant 2014; 29:1350-61. [PMID: 24574541 PMCID: PMC4071051 DOI: 10.1093/ndt/gfu019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background The ATP-sensitive P2X7 receptor (P2X7R) has been shown to contribute to renal injury in nephrotoxic nephritis, a rodent model of acute glomerulonephritis, and in unilateral ureteric obstruction (UUO), a rodent model of chronic interstitial inflammation and fibrosis. Renal tubular cells, endothelial cells and macrophages also express the closely related P2X4 receptor (P2X4R), which is chromosomally co-located with P2X7R and has 40% homology; it is also pro-inflammatory and has been shown to interact with P2X7R to modulate its pro-apoptotic and pro-inflammatory effects. Therefore, we chose to explore the function of P2X4R in the UUO model of renal injury using knockout mice. We hypothesized that UUO-induced tubulointerstitial damage and fibrosis would also be attenuated in P2X4R−/− mice. Method P2X4R−/− and wild-type (WT) mice were subjected to either UUO or sham operation. Kidney samples taken on Days 7 and 14 were evaluated for renal inflammation and fibrosis, and expression of pro-fibrotic factors. Results To our surprise, the obstructed kidney in P2X4R−/− mice showed more severe renal injury, more collagen deposition (picrosirius red staining, increase of 53%; P < 0.05) and more type I collagen staining (increase of 107%; P < 0.01), as well as increased mRNA for TGF-β (increase of 102%, P < 0.0005) and CTGF (increase of 157%; P < 0.05) by Day 14, compared with the UUO WT mice. Conclusion These findings showed that lack of P2X4R expression leads to increased renal fibrosis, and increased expression of TGF-β and CTGF in the UUO model.
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Affiliation(s)
- Min Jeong Kim
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK Clinic for Transplantations immunology and Nephrology, University Hospital Basel, Basel, Switzerland Department of Biomedicine, Molecular Nephrology, University Hospital Basel, Basel, Switzerland
| | - Clare M Turner
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
| | - Reiko Hewitt
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
| | - Jennifer Smith
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
| | - Gurjeet Bhangal
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
| | - Charles D Pusey
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
| | - Robert J Unwin
- UCL Centre for Nephrology, University College London, London, UK
| | - Frederick W K Tam
- Imperial College Renal and Transplant Centre, Hammersmith Hospital, Imperial College London, London, UK
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79
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Shieh CH, Heinrich A, Serchov T, van Calker D, Biber K. P2X7-dependent, but differentially regulated release of IL-6, CCL2, and TNF-α in cultured mouse microglia. Glia 2014; 62:592-607. [PMID: 24470356 DOI: 10.1002/glia.22628] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/20/2013] [Accepted: 12/23/2013] [Indexed: 01/04/2023]
Abstract
ATP is an important regulator of microglia and its effects on microglial cytokine release are currently discussed as important contributors in a variety of brain diseases. We here analyzed the effects of ATP on the production of six inflammatory mediators (IL-6, IL-10, CCL2, IFN-γ, TNF-α, and IL-12p70) in cultured mouse primary microglia. Stimulation of P2X7 receptor by ATP (1 mM) or BzATP (500 µM) evoked the mRNA expression and release of proinflammatory cytokines IL-6, TNF-α, and the chemokine CCL2 in WT cells but not in P2X7(-/-) cells. The effects of ATP and BzATP were inhibited by the nonselective P2 receptor antagonists PPADs and suramin. Various selective P2X7 receptor antagonists blocked the P2X7-dependent release of IL-6 and CCL2, but, surprisingly, had no effect on BzATP-induced release of TNF-α in microglia. Calcium measurements confirmed that P2X7 is the main purine receptor activated by BzATP in microglia and showed that all P2X7 antagonists were functional. It is also presented that pannexin-1 hemichannel function and potential P2X4/P2X7 heterodimers are not involved in P2X7-dependent release of IL-6, CCL2, and TNF-α in microglia. How P2X7-specific antagonists only affect P2X7-dependent IL-6 and CCL2 release, but not TNF-α release is at the moment unclear, but indicates that the P2X7-dependent release of cytokines in microglia is differentially regulated.
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Affiliation(s)
- Chu-Hsin Shieh
- Department of Psychiatry and Psychotherapy, University Hospital of Freiburg, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany
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Saul A, Hausmann R, Kless A, Nicke A. Heteromeric assembly of P2X subunits. Front Cell Neurosci 2013; 7:250. [PMID: 24391538 PMCID: PMC3866589 DOI: 10.3389/fncel.2013.00250] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 11/21/2013] [Indexed: 12/01/2022] Open
Abstract
Transcripts and/or proteins of P2X receptor (P2XR) subunits have been found in virtually all mammalian tissues. Generally more than one of the seven known P2X subunits have been identified in a given cell type. Six of the seven cloned P2X subunits can efficiently form functional homotrimeric ion channels in recombinant expression systems. This is in contrast to other ligand-gated ion channel families, such as the Cys-loop or glutamate receptors, where homomeric assemblies seem to represent the exception rather than the rule. P2XR mediated responses recorded from native tissues rarely match exactly the biophysical and pharmacological properties of heterologously expressed homomeric P2XRs. Heterotrimerization of P2X subunits is likely to account for this observed diversity. While the existence of heterotrimeric P2X2/3Rs and their role in physiological processes is well established, the composition of most other P2XR heteromers and/or the interplay between distinct trimeric receptor complexes in native tissues is not clear. After a description of P2XR assembly and the structure of the intersubunit ATP-binding site, this review summarizes the distribution of P2XR subunits in selected mammalian cell types and the biochemically and/or functionally characterized heteromeric P2XRs that have been observed upon heterologous co-expression of P2XR subunits. We further provide examples where the postulated heteromeric P2XRs have been suggested to occur in native tissues and an overview of the currently available pharmacological tools that have been used to discriminate between homo- and heteromeric P2XRs.
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Affiliation(s)
- Anika Saul
- Department of Molecular Biology of Neuronal Signals, Max Planck Institute for Experimental Medicine Göttingen, Germany
| | - Ralf Hausmann
- Molecular Pharmacology, RWTH Aachen University Aachen, Germany
| | - Achim Kless
- Department of Discovery Informatics, Grünenthal GmbH, Global Drug Discovery Aachen, Germany
| | - Annette Nicke
- Department of Molecular Biology of Neuronal Signals, Max Planck Institute for Experimental Medicine Göttingen, Germany
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81
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Sorrell ME, Hauser KF. Ligand-gated purinergic receptors regulate HIV-1 Tat and morphine related neurotoxicity in primary mouse striatal neuron-glia co-cultures. J Neuroimmune Pharmacol 2013; 9:233-44. [PMID: 24158495 DOI: 10.1007/s11481-013-9507-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Accepted: 10/04/2013] [Indexed: 12/20/2022]
Abstract
Emerging evidence suggests that opioid drugs, such as morphine and heroin, can exacerbate neuroAIDS. Microglia are the principal neuroimmune effectors thought to be responsible for neuron damage in HIV-infected individuals, and evidence suggests that opioid drugs acting via μ opioid receptors in microglia aggravate the neuropathophysiological effects of HIV. Key aspects of microglial function are regulated by the P2X family of ATP activated ligand-gated ion channels. In addition, opioid-dependent microglial activation has been reported to be mediated through P2X4 signaling, which prompted us to investigate whether the cation-permeable P2X receptors contribute to the neurotoxic effects of HIV and morphine. To address this question, neuron survival, as well as other endpoints including changes in dendritic length, extracellular ATP levels, and intracellular calcium levels, were assayed in primary neuron-glia co-cultures from mouse striatum. Treatment with TNP-ATP, a non-selective P2X antagonist, prevented the neurotoxic effects of exposure to morphine and/or HIV Tat, or ATP alone, suggesting P2X receptors mediate the neurotoxic effects of these insults in striatal neurons. Although P2X7, and perhaps P2X1, receptor activation decreases neuron survival, neither P2X1, P2X3, nor P2X7 selective receptor antagonists prevented Tat and/or morphine-induced neurotoxicity. These and other experiments indicate the P2X receptor family contributes to Tat- and morphine- related neuronal injury, and provide circumstantial evidence implicating P2X4 receptors in particular. Our findings reveal that members of the P2X receptor family, especially P2X4, may be novel therapeutic targets for restricting the synaptodendritic injury and neurodegeneration that accompanies neuroAIDS and opiate abuse.
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Affiliation(s)
- Mary E Sorrell
- Department of Pharmacology & Toxicology, Virginia Commonwealth University School of Medicine, 1217 East Marshall Street, Richmond, VA, 23298-0613, USA
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82
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Rosenthal AK, Gohr CM, Mitton-Fitzgerald E, Lutz MK, Dubyak GR, Ryan LM. The progressive ankylosis gene product ANK regulates extracellular ATP levels in primary articular chondrocytes. Arthritis Res Ther 2013; 15:R154. [PMID: 24286344 PMCID: PMC3978574 DOI: 10.1186/ar4337] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 10/02/2013] [Indexed: 02/06/2023] Open
Abstract
Introduction Extracellular ATP (eATP) is released by articular chondrocytes under physiological and pathological conditions. High eATP levels cause pathologic calcification, damage cartilage, and mediate pain. We recently showed that stable over-expression of the progressive ankylosis gene product, ANK, increased chondrocyte eATP levels, but the mechanisms of this effect remained unexplored. The purpose of this work was to further investigate mechanisms of eATP efflux in primary articular chondrocytes and to better define the role of ANK in this process. Methods We measured eATP levels using a bioluminescence-based assay in adult porcine articular chondrocyte media with or without a 10 minute exposure to hypotonic stress. siRNAs for known ATP membrane transporters and pharmacologic inhibitors of ATP egress pathways were used to identify participants involved in chondrocyte eATP release. Results eATP levels increased after exposure to hypotonic media in a calcium-dependent manner in monolayer and 3-dimensional agarose gel cultures (p < 0.001). A potent transient receptor potential vanilloid 4 (TRPV4) agonist mimicked the effects of hypotonic media. ANK siRNA suppressed basal (p < 0.01) and hypotonically-stressed (p < 0.001) ATP levels. This effect was not mediated by altered extracellular pyrophosphate (ePPi) levels, and was mimicked by the ANK inhibitor, probenecid (p < 0.001). The P2X7/4 receptor inhibitor Brilliant Blue G also suppressed eATP efflux induced by hypotonic media (p < 0.001), while ivermectin, a P2X4 receptor stimulant, increased eATP levels (p < 0.001). Pharmacologic inhibitors of hemichannels, maxianion channels and other volume-sensitive eATP efflux pathways did not suppress eATP levels. Conclusions These findings implicate ANK and P2X7/4 receptors in chondrocyte eATP efflux. Understanding the mechanisms of eATP efflux may result in novel therapies for calcium crystal arthritis and osteoarthritis.
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83
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Young CNJ, Sinadinos A, Gorecki DC. P2X receptor signaling in skeletal muscle health and disease. ACTA ACUST UNITED AC 2013. [DOI: 10.1002/wmts.96] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Anthony Sinadinos
- School of Pharmacy and Biomedical Sciences; University of Portsmouth; Portsmouth PO1 2DT UK
| | - Dariusz C. Gorecki
- School of Pharmacy and Biomedical Sciences; University of Portsmouth; Portsmouth PO1 2DT UK
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Subtype-specific control of P2X receptor channel signaling by ATP and Mg2+. Proc Natl Acad Sci U S A 2013; 110:E3455-63. [PMID: 23959888 DOI: 10.1073/pnas.1308088110] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The identity and forms of activating ligands for ion channels are fundamental to their physiological roles in rapid electrical signaling. P2X receptor channels are ATP-activated cation channels that serve important roles in sensory signaling and inflammation, yet the active forms of the nucleotide are unknown. In physiological solutions, ATP is ionized and primarily found in complex with Mg(2+). Here we investigated the active forms of ATP and found that the action of MgATP(2-) and ATP(4-) differs between subtypes of P2X receptors. The slowly desensitizing P2X2 receptor can be activated by free ATP, but MgATP(2-) promotes opening with very low efficacy. In contrast, both free ATP and MgATP(2-) robustly open the rapidly desensitizing P2X3 subtype. A further distinction between these two subtypes is the ability of Mg(2+) to regulate P2X3 through a distinct allosteric mechanism. Importantly, heteromeric P2X2/3 channels present in sensory neurons exhibit a hybrid phenotype, characterized by robust activation by MgATP(2-) and weak regulation by Mg(2+). These results reveal the existence of two classes of homomeric P2X receptors with differential sensitivity to MgATP(2-) and regulation by Mg(2+), and demonstrate that both restraining mechanisms can be disengaged in heteromeric channels to form fast and sensitive ATP signaling pathways in sensory neurons.
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P2X7 receptors regulate engulfing activity of non-stimulated resting astrocytes. Biochem Biophys Res Commun 2013; 439:90-5. [PMID: 23958305 DOI: 10.1016/j.bbrc.2013.08.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 08/08/2013] [Indexed: 12/24/2022]
Abstract
We previously demonstrated that P2X7 receptors (P2X7Rs) expressed by cultured mouse astrocytes were activated without any exogenous stimuli, but its roles in non-stimulated resting astrocytes remained unknown. It has been reported that astrocytes exhibit engulfing activity, and that the basal activity of P2X7Rs regulates the phagocytic activity of macrophages. In this study, therefore, we investigated whether P2X7Rs regulate the engulfing activity of mouse astrocytes. Uptake of non-opsonized beads by resting astrocytes derived from ddY-mouse cortex time-dependently increased, and the uptaken beads were detected in the intracellular space. The bead uptake was inhibited by cytochalasin D (CytD), an F-actin polymerization inhibitor, and agonists and antagonists of P2X7Rs apparently decreased the uptake. Spontaneous YO-PRO-1 uptake by ddY-mouse astrocytes was reduced by the agonists and antagonists of P2X7Rs, but not by CytD. Down-regulation of P2X7Rs using siRNA decreased the bead uptake by ddY-mouse astrocytes. In addition, compared to in the case of ddY-mouse astrocytes, SJL-mouse astrocytes exhibited higher YO-PRO-1 uptake activity, and their bead uptake was significantly greater. These findings suggest that resting astrocytes exhibit engulfing activity and that the activity is regulated, at least in part, by their P2X7Rs.
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Craigie E, Birch RE, Unwin RJ, Wildman SS. The relationship between P2X4 and P2X7: a physiologically important interaction? Front Physiol 2013; 4:216. [PMID: 23966951 PMCID: PMC3744038 DOI: 10.3389/fphys.2013.00216] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 07/27/2013] [Indexed: 11/24/2022] Open
Abstract
Purinergic signaling within the kidney is becoming an important focus in the study of renal health and disease. The effectors of ATP signaling, the P2Y and P2X receptors, are expressed to varying extents in and along the nephron. There are many studies demonstrating the importance of the P2Y2 receptor on kidney function, and other P2 receptors are now emerging as participants in renal regulation. The P2X4 receptor has been linked to epithelial sodium transport in the nephron and expression levels of the P2X7 receptor are up-regulated in certain pathophysiological states. P2X7 antagonism has been shown to ameliorate rodent models of DOCA salt-induced hypertension and P2X4 null mice are hypertensive. Interestingly, polymorphisms in the genetic loci of P2X4 and P2X7 have been linked to blood pressure variation in human studies. In addition to the increasing evidence linking these two P2X receptors to renal function and health, a number of studies link the two receptors in terms of physical associations between their subunits, demonstrated both in vitro and in vivo. This review will analyze the current literature regarding interactions between P2X4 and P2X7 and assess the potential impact of these with respect to renal function.
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Affiliation(s)
- Eilidh Craigie
- Centre for Nephrology, UCL Medical School, University College London London, UK
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Smith SMC, Mitchell GS, Friedle SA, Sibigtroth CM, Vinit S, Watters JJ. Hypoxia Attenuates Purinergic P2X Receptor-Induced Inflammatory Gene Expression in Brainstem Microglia. HYPOXIA 2013; 2013. [PMID: 24377098 PMCID: PMC3873144 DOI: 10.2147/hp.s45529] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hypoxia and increased extracellular nucleotides are frequently coincident in the brainstem. Extracellular nucleotides are potent modulators of microglial inflammatory gene expression via P2X purinergic receptor activation. Although hypoxia is also known to modulate inflammatory gene expression, little is known about how hypoxia or P2X receptor activation alone affects inflammatory molecule production in brainstem microglia, nor how hypoxia and P2X receptor signaling interact when they occur together. In the study reported here, we investigated the ability of a brief episode of hypoxia (2 hours) in the presence and absence of the nonselective P2X receptor agonist 2′(3′)-O-(4-benzoylbenzoyl)adenosine-5′-triphosphate (BzATP) to promote inflammatory gene expression in brainstem microglia in adult rats. We evaluated inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNFα), and interleukin (IL)-6 messenger RNA levels in immunomagnetically isolated brainstem microglia. While iNOS and IL-6 gene expression increased with hypoxia and BzATP alone, TNFα expression was unaffected. Surprisingly, BzATP-induced inflammatory effects were lost after hypoxia, suggesting that hypoxia impairs proinflammatory P2X-receptor signaling. We also evaluated the expression of key P2X receptors activated by BzATP, namely P2X1, P2X4, and P2X7. While hypoxia did not alter their expression, BzATP upregulated P2X4 and P2X7 mRNAs; these effects were ablated in hypoxia. Although both P2X4 and P2X7 receptor expression correlated with increased microglial iNOS and IL-6 levels in microglia from normoxic rats, in hypoxia, P2X7 only correlated with IL-6, and P2X4 correlated only with iNOS. In addition, correlations between P2X7 and P2X4 were lost following hypoxia, suggesting that P2X4 and P2X7 receptor signaling differs in normoxia and hypoxia. Together, these data suggest that hypoxia suppresses P2X receptor-induced inflammatory gene expression, indicating a potentially immunosuppressive role of extracellular nucleotides in brainstem microglia following exposure to hypoxia.
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Affiliation(s)
- Stephanie M C Smith
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA 53706 ; Comparative Biomedical Sciences Training Program, University of Wisconsin, Madison, WI, USA 53706
| | - Gordon S Mitchell
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA 53706 ; Comparative Biomedical Sciences Training Program, University of Wisconsin, Madison, WI, USA 53706
| | - Scott A Friedle
- Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI, USA 53706
| | | | - Stéphane Vinit
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA 53706
| | - Jyoti J Watters
- Department of Comparative Biosciences, University of Wisconsin, Madison, WI, USA 53706 ; Comparative Biomedical Sciences Training Program, University of Wisconsin, Madison, WI, USA 53706 ; Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI, USA 53706
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Hung SC, Choi CH, Said-Sadier N, Johnson L, Atanasova KR, Sellami H, Yilmaz Ö, Ojcius DM. P2X4 assembles with P2X7 and pannexin-1 in gingival epithelial cells and modulates ATP-induced reactive oxygen species production and inflammasome activation. PLoS One 2013; 8:e70210. [PMID: 23936165 PMCID: PMC3723664 DOI: 10.1371/journal.pone.0070210] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/17/2013] [Indexed: 01/17/2023] Open
Abstract
We have previously reported that Porphyromonas gingivalis infection of gingival epithelial cells (GEC) requires an exogenous danger signal such as ATP to activate an inflammasome and caspase-1, thereby inducing secretion of interleukin (IL)-1β. Stimulation with extracellular ATP also stimulates production of reactive oxygen species (ROS) in GEC. However, the mechanism by which ROS is generated in response to ATP, and the role that different purinergic receptors may play in inflammasome activation, is still unclear. In this study, we revealed that the purinergic receptor P2X4 is assembled with the receptor P2X7 and its associated pore, pannexin-1. ATP induces ROS production through a complex consisting of the P2X4, P2X7, and pannexin-1. P2X7−mediated ROS production can activate the NLRP3 inflammasome and caspase-1. Furthermore, separate depletion or inhibition of P2X4, P2X7, or pannexin-1 complex blocks IL-1β secretion in P. gingivalis-infected GEC following ATP treatment. However, activation via P2X4 alone induces ROS generation but not inflammasome activation. These results suggest that ROS is generated through stimulation of a P2X4/P2X7/pannexin-1 complex, and reveal an unexpected role for P2X4, which acts as a positive regulator of inflammasome activation during microbial infection.
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Affiliation(s)
- Shu-Chen Hung
- Department of Molecular Cell Biology, University of California Merced, Merced, California, United States of America
- Health Sciences Research Institute, University of California Merced, Merced, California, United States of America
| | - Chul Hee Choi
- Department of Periodontology, University of Florida, Gainesville, Florida, United States of America
| | - Najwane Said-Sadier
- Department of Molecular Cell Biology, University of California Merced, Merced, California, United States of America
- Health Sciences Research Institute, University of California Merced, Merced, California, United States of America
| | - Larry Johnson
- Department of Molecular Cell Biology, University of California Merced, Merced, California, United States of America
- Health Sciences Research Institute, University of California Merced, Merced, California, United States of America
| | | | - Hanen Sellami
- Department of Molecular Cell Biology, University of California Merced, Merced, California, United States of America
- Health Sciences Research Institute, University of California Merced, Merced, California, United States of America
- Department of Microbiology, Habib Bourguiba University Hospital, Medical School of Sfax, University of Sfax, Sfax, Tunisia
| | - Özlem Yilmaz
- Department of Periodontology, University of Florida, Gainesville, Florida, United States of America
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - David M. Ojcius
- Department of Molecular Cell Biology, University of California Merced, Merced, California, United States of America
- Health Sciences Research Institute, University of California Merced, Merced, California, United States of America
- * E-mail:
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89
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Pharmacological insights into the role of P2X4 receptors in behavioural regulation: lessons from ivermectin. Int J Neuropsychopharmacol 2013; 16:1059-70. [PMID: 23174033 PMCID: PMC3593990 DOI: 10.1017/s1461145712000909] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Purinergic ionotropic P2X receptors are a family of cation-permeable channels that bind extracellular adenosine 5'-triphosphate. In particular, convergent lines of evidence have recently highlighted P2X(4) receptors as a potentially critical target in the regulation of multiple nervous and behavioural functions, including pain, neuroendocrine regulation and hippocampal plasticity. Nevertheless, the role of the P2X(4) receptor in behavioural organization remains poorly investigated. To study the effects of P2X(4) activation, we tested the acute effects of its potent positive allosteric modulator ivermectin (IVM, 2.5-10 mg/kg i.p.) on a broad set of paradigms capturing complementary aspects of perceptual, emotional and cognitive regulation in mice. In a novel open field, IVM did not induce significant changes in locomotor activity, but increased the time spent in the peripheral zone. In contrast, IVM produced anxiolytic-like effects in the elevated plus maze and marble burying tasks, as well as depression-like behaviours in the tail-suspension and forced swim tests. The agent induced no significant behavioural changes in the conditioned place preference test and in the novel object recognition task. Finally, the drug induced a dose-dependent decrease in sensorimotor gating, as assessed by pre-pulse inhibition (PPI) of the acoustic startle reflex. In P2X(4) knockout mice, the effects of IVM in the open field and elevated plus maze were similar to those observed in wild type mice; conversely, the drug significantly increased startle amplitude and failed to reduce PPI. Taken together, these results suggest that P2X(4) receptors may play a role in the regulation of sensorimotor gating.
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90
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Oxidative stress induced by P2X7 receptor stimulation in murine macrophages is mediated by c-Src/Pyk2 and ERK1/2. Biochim Biophys Acta Gen Subj 2013; 1830:4650-9. [PMID: 23711511 DOI: 10.1016/j.bbagen.2013.05.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 05/11/2013] [Accepted: 05/15/2013] [Indexed: 12/20/2022]
Abstract
BACKGROUND Activation of ATP-gated P2X7 receptors (P2X7R) in macrophages leads to production of reactive oxygen species (ROS) by a mechanism that is partially characterized. Here we used J774 cells to identify the signaling cascade that couples ROS production to receptor stimulation. METHODS J774 cells and mP2X7-transfected HEK293 cells were stimulated with Bz-ATP in the presence and absence of extracellular calcium. Protein inhibitors were used to evaluate the physiological role of various kinases in ROS production. In addition, phospho-antibodies against ERK1/2 and Pyk2 were used to determine activation of these two kinases. RESULTS ROS generation in either J774 or HEK293 cells (expressing P2X7, NOX2, Rac1, p47phox and p67phox) was strictly dependent on calcium entry via P2X7R. Stimulation of P2X7R activated Pyk2 but not calmodulin. Inhibitors of MEK1/2 and c-Src abolished ERK1/2 activation and ROS production but inhibitors of PI3K and p38 MAPK had no effect on ROS generation. PKC inhibitors abolished ERK1/2 activation but barely reduced the amount of ROS produced by Bz-ATP. In agreement, the amount of ROS produced by PMA was about half of that produced by Bz-ATP. CONCLUSIONS Purinergic stimulation resulted in calcium entry via P2X7R and subsequent activation of the PKC/c-Src/Pyk2/ERK1/2 pathway to produce ROS. This signaling mechanism did not require PI3K, p38 MAPK or calmodulin. GENERAL SIGNIFICANCE ROS is generated in order to kill invading pathogens, thus elucidating the mechanism of ROS production in macrophages and other immune cells allow us to understand how our body copes with microbial infections.
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91
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Nieto-Pescador MG, Guerrero-Alba R, Valdez-Morales E, Espinosa-Luna R, Jiménez-Vargas N, Liñan-Rico Andrómeda A, Ramos-Lomas TL, Díaz-Hernández Verónica V, Montaño LM, Barajas-López C. P2X4 subunits are part of P2X native channels in murine myenteric neurons. Eur J Pharmacol 2013; 709:93-102. [PMID: 23567069 DOI: 10.1016/j.ejphar.2013.03.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 03/27/2013] [Accepted: 03/28/2013] [Indexed: 02/06/2023]
Abstract
The aim of the present study was to investigate if P2X4 receptors are expressed in murine myenteric neurons and if these receptors contribute to form functional channels in the neuronal membrane by using molecular and electrophysiological techniques. The whole-cell recording technique was used to measure membrane currents induced by ATP (I(ATP)) in myenteric neurons. Compared with recombinant P2X4 receptor-channels (reported by others in a previous study), native myenteric P2X receptors have a relative lower sensitivity for ATP (EC₅₀=102 µM) and α,β methylene ATP (not effect at 30 or 100 µM). BzATP was a weak agonist for native P2X receptors. KN-62 had no effect on myenteric P2X channels whereas PPADS (IC₅₀=0.54 µM) or suramin (IC₅₀=134 µM) were more potent antagonists than on P2X4 homomeric channels. I(ATP) were potentiated by ivermectin (effect that is specific on P2X4 receptors) and zinc. Western blotting shows the presence of P2X4 protein and RT-PCR the corresponding mRNA transcript in the small intestine. Immunoreactivity for P2X4 receptors was found in most myenteric neurons in culture. Single-cell RT-PCR shows the presence of P2X4 mRNA in 90% of myenteric neurons. Our results indicate that P2X4 receptors are expressed in the majority of myenteric neurons, contribute to the membrane currents activated by ATP, and because most properties of I(ATP) does not correspond to P2X4 homomeric channels it is proposed that P2X4 are forming heteromeric channels in these neurons. P2X4 subunits have a widespread distribution within the myenteric plexus and would be expected to play an important role in cell signaling.
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Affiliation(s)
- María G Nieto-Pescador
- División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica, San Luis Potosí, SLP 78216, Mexico
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92
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Purinergic mechanisms and pain--an update. Eur J Pharmacol 2013; 716:24-40. [PMID: 23524093 DOI: 10.1016/j.ejphar.2013.01.078] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 12/11/2012] [Accepted: 01/09/2013] [Indexed: 12/12/2022]
Abstract
There is a brief summary of the background literature about purinergic signalling. The review then considers purinergic mechanosensory transduction involved in visceral, cutaneous and musculoskeletal nociception and on the roles played by P2X3, P2X2/3, P2X4, P2X7 and P2Y₁₂ receptors in neuropathic and inflammatory pain. Current developments of compounds for the therapeutic treatment of both visceral and neuropathic pain are discussed.
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93
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Lowe M, Park SJ, Nurse CA, Campanucci VA. Purinergic stimulation of carotid body efferent glossopharyngeal neurones increases intracellular Ca2+ and nitric oxide production. Exp Physiol 2013; 98:1199-212. [PMID: 23525247 DOI: 10.1113/expphysiol.2013.072058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mammalian carotid body (CB) is a peripheral chemosensory organ that controls ventilation and is innervated by both afferent and efferent nerve fibres. The afferent pathway is stimulated by chemoexcitants, such as hypoxia, hypercapnia and acidosis. The efferent pathway causes inhibition of the sensory discharge via release of NO that originates mainly from neuronal nitric oxide synthase (nNOS)-positive autonomic neurones within the glossopharyngeal nerve (GPN). Recent studies in the rat indicate that these inhibitory GPN neurones and their processes express purinergic P2X receptors and can be activated by ATP, a key excitatory CB neurotransmitter. Here we tested the hypothesis that purinergic agonists stimulate a rise in [Ca(2+)]i, leading to nNOS activation and NO production in isolated GPN neurones, using the fluorescent probes fura-2 and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA), respectively. ATP caused a dose-dependent increase in [Ca(2+)]i in GPN neurones (EC50 ≈ 1.92 μm) that was markedly inhibited by a combination of 100 μm suramin (a non-specific P2X blocker) and 100 nm Brilliant Blue G (a selective P2X7 blocker). ATP also stimulated NO production in GPN neurones, as revealed by an increase in DAF fluorescence; this NO signal was inhibited by purinergic blockers, chelators of extracellular Ca(2+), the nNOS inhibitor l-NAME and the NO scavenger carboxy-PTIO. The P2X2/3 and P2X7 agonists α,β,-methylene ATP and benzoyl ATP mimicked the effects of ATP. Taken together, these data indicate that ATP may contribute to negative feedback inhibition of CB sensory discharge via purinergic stimulation of NO production in efferent fibres.
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Affiliation(s)
- Michael Lowe
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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94
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Nörenberg W, Sobottka H, Hempel C, Plötz T, Fischer W, Schmalzing G, Schaefer M. Positive allosteric modulation by ivermectin of human but not murine P2X7 receptors. Br J Pharmacol 2013; 167:48-66. [PMID: 22506590 DOI: 10.1111/j.1476-5381.2012.01987.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND PURPOSE In mammalian cells, the anti-parasitic drug ivermectin is known as a positive allosteric modulator of the ATP-activated ion channel P2X4 and is used to discriminate between P2X4- and P2X7-mediated cellular responses. In this paper we provide evidence that the reported isoform selectivity of ivermectin is a species-specific phenomenon. EXPERIMENTAL APPROACH Complementary electrophysiological and fluorometric methods were applied to evaluate the effect of ivermectin on recombinantly expressed and on native P2X7 receptors. A biophysical characterization of ionic currents and of the pore dilation properties is provided. KEY RESULTS Unexpectedly, ivermectin potentiated currents in human monocyte-derived macrophages that endogenously express hP2X7 receptors. Likewise, currents and [Ca(2+) ](i) influx through recombinant human (hP2X7) receptors were potently enhanced by ivermectin at submaximal or saturating ATP concentrations. Since intracellular ivermectin did not mimic or prevent its activity when applied to the bath solution, the binding site of ivermectin on hP2X7 receptors appears to be accessible from the extracellular side. In contrast to currents through P2X4 receptors, ivermectin did not cause a delay in hP2X7 current decay upon ATP removal. Interestingly, NMDG(+) permeability and Yo-Pro-1 uptake were not affected by ivermectin. On rat or mouse P2X7 receptors, ivermectin was only poorly effective, suggesting a species-specific mode of action. CONCLUSIONS AND IMPLICATIONS The data indicate a previously unrecognized species-specific modulation of human P2X7 receptors by ivermectin that should be considered when using this cell-biological tool in human cells and tissues.
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Affiliation(s)
- W Nörenberg
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, Medical Faculty, University of Leipzig, Leipzig, Germany
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95
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Kobayashi K, Yamanaka H, Noguchi K. Expression of ATP receptors in the rat dorsal root ganglion and spinal cord. Anat Sci Int 2012. [PMID: 23179910 DOI: 10.1007/s12565-012-0163-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Extracellular purine nucleotides and nucleosides play important roles in the nervous system, e.g., neurotransmission, neuromodulation, chemoattraction and acute inflammation. Extracellular nucleotides act through ATP receptors (P2 receptors). P2 receptors are classified into two families: the P2X receptors are ionotropic ligand-gated ion channels and the P2Y receptors are metabotropic G-protein-coupled receptors. Currently, seven P2X receptors (P2X1-7) and eight P2Y receptors (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13 and P2Y14) are recognized. In the sensory nervous system, ATP is suggested to be one of first mediators of tissue damage, which activates primary afferents. Nerve injury often leads to neuropathic pain, such as mechanical allodynia and painful responses to normally innocuous stimuli. Peripheral nerve injury induces the upregulation of molecules in activated microglia in the spinal cord. Microglia in the spinal cord may play an important role in the development and maintenance of neuropathic pain. A prominent signaling pathway in the development of neuropathic pain involves ATP acting on microglial purinergic receptors. This review focuses on the expression of P2X and P2Y receptors mRNAs in the pain transmission pathway, i.e., in the dorsal root ganglion (DRG) and spinal cord. Furthermore, we suggest that the multiple microglial P2Y receptors activated by peripheral nerve injury may play a key role in the development of neuropathic pain.
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Affiliation(s)
- Kimiko Kobayashi
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo, Japan.
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96
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Microglia proliferation is controlled by P2X7 receptors in a Pannexin-1-independent manner during early embryonic spinal cord invasion. J Neurosci 2012; 32:11559-73. [PMID: 22915101 DOI: 10.1523/jneurosci.1042-12.2012] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Microglia are known to invade the mammalian spinal cord (SC) at an early embryonic stage. While the mechanisms underlying this early colonization of the nervous system are still unknown, we recently found that it is associated, at least partially, with the ability of microglia to proliferate at the onset of motoneuron developmental cell death and of synaptogenesis in mouse embryo (E13.5). In vitro studies have shown that the proliferation and activation of adult microglia can be influenced by the purinergic ionotropic receptor P2X7 via a coupling with Pannexin-1. By performing patch-clamp recordings in situ using a whole-mouse embryonic SC preparation, we show here that embryonic microglia already express functional P2X7R. P2X7R activation evoked a biphasic current in embryonic microglia, which is supposed to reflect large plasma membrane pore opening. However, although embryonic microglia express pannexin-1, this biphasic current was still recorded in microglia of pannexin-1 knock-out embryos, indicating that it rather reflected P2X7R intrinsic pore dilatation. More important, we found that proliferation of embryonic SC microglia, but not their activation state, depends almost entirely on P2X7R by comparing wild-type and P2X7R-/- embryos. Absence of P2X7R led also to a decrease in microglia density. Pannexin-1-/- embryos did not exhibit any difference in microglial proliferation, showing that the control of embryonic microglial proliferation by P2X7R does not depend on pannexin-1 expression. These results reveal a developmental role of P2X7R by controlling embryonic SC microglia proliferation at a critical developmental state in the SC of mouse embryos.
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97
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Masin M, Young C, Lim K, Barnes SJ, Xu XJ, Marschall V, Brutkowski W, Mooney ER, Gorecki DC, Murrell-Lagnado R. Expression, assembly and function of novel C-terminal truncated variants of the mouse P2X7 receptor: re-evaluation of P2X7 knockouts. Br J Pharmacol 2012; 165:978-93. [PMID: 21838754 DOI: 10.1111/j.1476-5381.2011.01624.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Splice variants of P2X7 receptor transcripts contribute to the diversity of receptor-mediated responses. Here, we investigated expression and function of C-terminal truncated (ΔC) variants of the mP2X7 receptor, which are predicted to escape inactivation in one strain of P2X7(-/-) mice (Pfizer KO). EXPERIMENTAL APPROACH Expression in wild-type (WT) and Pfizer KO tissue was investigated by reverse transcription (RT)-PCR and Western blot analysis. ΔC variants were also cloned and expressed in HEK293 cells to investigate their assembly, trafficking and function. KEY RESULTS RT-PCR indicates expression of a ΔC splice variant in brain, salivary gland (SG) and spleen from WT and Pfizer KO mice. An additional ΔC hybrid transcript, containing sequences of P2X7 upstream of exon 12, part of exon 13 followed in-frame by the sequence of the vector used to disrupt the P2X7 gene, was also identified in the KO mice. By blue native (BN) PAGE analysis and the use of cross linking reagents followed by SDS-PAGE, P2X7 trimers, dimers and monomers were detected in the spleen and SG of Pfizer KO mice. The molecular mass was reduced compared with P2X7 in WT mice tissue, consistent with a ΔC variant. When expressed in HEK293 cells the ΔC variants were inefficiently trafficked to the cell surface and agonist-evoked whole cell currents were small. Co-expressed with P2X7A, the ΔC splice variant acted in a dominant negative fashion to inhibit function. CONCLUSIONS AND IMPLICATIONS Pfizer KO mice are not null for P2X7 receptor expression but express ΔC variants with reduced function.
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Affiliation(s)
- Marianela Masin
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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98
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Xu XJ, Boumechache M, Robinson LE, Marschall V, Gorecki DC, Masin M, Murrell-Lagnado RD. Splice variants of the P2X7 receptor reveal differential agonist dependence and functional coupling with pannexin-1. J Cell Sci 2012; 125:3776-89. [PMID: 22553206 DOI: 10.1242/jcs.099374] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
P2X7 receptors function as ATP-gated cation channels but also interact with other proteins as part of a larger signalling complex to mediate a variety of downstream responses that are dependent upon the cell type in which they are expressed. Receptor-mediated membrane permeabilization to large molecules precedes the induction of cell death, but remains poorly understood. The mechanisms that underlie differential sensitivity to NAD are also unknown. By studying alternative variants of the mouse P2X7 receptor we show that sensitivity to NAD is mediated through the P2X7k variant, which has a much more restricted distribution than the P2X7a receptor, but is expressed in T lymphocytes. The altered N-terminus and TM1 of the P2X7k receptor enhances the stability of the active state of this variant compared with P2X7a, thereby increasing the efficacy of NAD-dependent ADP ribosylation as measured by ethidium uptake, a rise in intracellular Ca(2+) and the activation of inward currents. Co-expression of P2X7k and P2X7a receptors reduced NAD sensitivity. P2X7k-receptor-mediated ethidium uptake was also triggered by much lower BzATP concentrations and was insensitive to the P451L single nucleotide polymorphism. P2X7k-receptor-mediated ethidium uptake occurred independently of pannexin-1 suggesting a pathway intrinsic to the receptor. Only for the P2X7aL451 receptor could we resolve a component of dye uptake dependent upon pannexin-1. Signalling occurred downstream of the activation of caspases rather than involving direct cross talk between the channels. However, an in situ proximity assay showed close association between P2X7 receptors and pannexin-1, which would facilitate ATP efflux through pannexin-1 acting in an autocrine manner.
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Affiliation(s)
- Xing Jian Xu
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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99
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Kaczmarek-Hájek K, Lörinczi E, Hausmann R, Nicke A. Molecular and functional properties of P2X receptors--recent progress and persisting challenges. Purinergic Signal 2012; 8:375-417. [PMID: 22547202 PMCID: PMC3360091 DOI: 10.1007/s11302-012-9314-7] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 10/18/2011] [Indexed: 12/16/2022] Open
Abstract
ATP-gated P2X receptors are trimeric ion channels that assemble as homo- or heteromers from seven cloned subunits. Transcripts and/or proteins of P2X subunits have been found in most, if not all, mammalian tissues and are being discovered in an increasing number of non-vertebrates. Both the first crystal structure of a P2X receptor and the generation of knockout (KO) mice for five of the seven cloned subtypes greatly advanced our understanding of their molecular and physiological function and their validation as drug targets. This review summarizes the current understanding of the structure and function of P2X receptors and gives an update on recent developments in the search for P2X subtype-selective ligands. It also provides an overview about the current knowledge of the regulation and modulation of P2X receptors on the cellular level and finally on their physiological roles as inferred from studies on KO mice.
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Affiliation(s)
- Karina Kaczmarek-Hájek
- Max Planck Institute for Experimental Medicine, Hermann Rein Str. 3, 37075, Göttingen, Germany
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100
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Abstract
P2X(4) and P2X(7) are the predominant purinergic P2X receptor subtypes expressed on immune and neural cells. These receptor subtypes traffic between intracellular compartments and the plasma membrane and form protein interactions with each other to regulate ATP-dependent signaling. Our recent studies have shown that P2X(7) receptors in neurons and astrocytes activate NLRP1 inflammasomes, but whether P2X(4) receptors regulate inflammasome signaling is essentially unknown. Here, we demonstrate that P2X(4) receptors are expressed in neurons of the spinal cord. We provide direct evidence that spinal cord injury (SCI) induces an innate inflammatory response that leads to increased caspase-l cleavage and production of IL-1β but not IL-18. Consistent with these findings, P2X(4) knock-out mice showed impaired inflammasome signaling in the cord, resulting in decreased levels of IL-1β and reduced infiltration of neutrophils and monocyte-derived M1 macrophages, resulting in significant tissue sparing and improvement in functional outcomes. These results indicate that P2X(4) receptors influence inflammasome signaling involving caspase-1 activation and IL-1β processing in neurons after SCI. P2X(4) might thus represent a potential therapeutic target to limit inflammatory responses associated with SCI and neurodegenerative disorders.
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