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Localization of the gate and selectivity filter of the full-length P2X7 receptor. Proc Natl Acad Sci U S A 2017; 114:E2156-E2165. [PMID: 28235784 DOI: 10.1073/pnas.1610414114] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The P2X7 receptor (P2X7R) belongs to the P2X family of ATP-gated cation channels. P2X7Rs are expressed in epithelial cells, leukocytes, and microglia, and they play important roles in immunological and inflammatory processes. P2X7Rs are obligate homotrimers, with each subunit having two transmembrane helices, TM1 and TM2. Structural and functional data regarding the P2X2 and P2X4 receptors indicate that the central trihelical TM2 bundle forms the intrinsic transmembrane channel of P2X receptors. Here, we studied the accessibility of single cysteines substituted along the pre-TM2 and TM2 helix (residues 327-357) of the P2X7R using as readouts (i) the covalent maleimide fluorescence accessibility of the surface-bound P2X7R and (ii) covalent modulation of macroscopic and single-channel currents using extracellularly and intracellularly applied methanethiosulfonate (MTS) reagents. We found that the channel opening extends from the pre-TM2 region through the outer half of the trihelical TM2 channel. Covalently adducted MTS ethylammonium+ (MTSEA+) strongly increased the probability that the channel was open by delaying channel closing of seven of eight responsive human P2X7R (hP2X7R) mutants. Structural modeling, as supported by experimental probing, suggested that resulting intraluminal hydrogen bonding interactions stabilize the open-channel state. The additional decrease in single-channel conductance by MTSEA+ in five of seven positions identified Y336, S339, L341C, Y343, and G345 as the narrowest part of the channel lumen. The gate and ion-selectivity filter of the P2X7R could be colocalized at and around residue S342. None of our results provided any evidence for dilation of the hP2X7R channel on sustained stimulation with ATP4.
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52
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Freitas HR, Reis RADM. Glutathione induces GABA release through P2X 7R activation on Müller glia. NEUROGENESIS 2017; 4:e1283188. [PMID: 28229088 DOI: 10.1080/23262133.2017.1283188] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/25/2016] [Accepted: 01/10/2017] [Indexed: 01/04/2023]
Abstract
The retinal tissue of warm-blooded vertebrates performs surprisingly complex and accurate transduction of visual information. To achieve precision, a multilayered neuroglia structure is established throughout the embryonic development, and the presence of radial Müller (glial) cells ensure differentiation, growth and survival for the neuronal elements within retinal environment. It is assumed that Müller cells serve as a dynamic reservoir of progenitors, capable of expressing transcription factors, differentiating and proliferating as either neuronal or glial cells depending on extrinsic cues. In the postnatal period, Müller glia may re-enter cell cycle and produce new retinal neurons in response to acute damage. In this context, glutathione (GSH), a virtually ubiquitous tripeptide antioxidant, which is found at milimolar concentrations in central glial cells, plays a vital role as a reducing agent, buffering radical oxygen species (ROS) and preventing cell death in severely injured retinal tissues. Despite its antioxidant role, data also point to GSH as a signaling agent, suggesting that GABA release and P2X7R-mediated calcium inwards occur in Müller cells in a GSH-enriched environment. These phenomena indicate a novel mechanistic response to damage in the vertebrate retinal tissue, particularly in neuron-glia networks.
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Affiliation(s)
- Hércules Rezende Freitas
- Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Brazil
| | - Ricardo A de Melo Reis
- Laboratório de Neuroquímica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Brazil
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53
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Karasawa A, Kawate T. Expression and Purification of a Mammalian P2X7 Receptor from Sf9 Insect Cells. Bio Protoc 2017; 7:e2544. [PMID: 28966946 DOI: 10.21769/bioprotoc.2544] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The P2X7 receptor is an extracellular ATP-gated ion channel found only in eukaryotes (Bartlett et al., 2014). Due to its unique properties among P2X receptors, such as formation of a large conductance pore, the P2X7 receptor has been implicated in devastating diseases like chronic pain (North and Jarvis, 2013). However, mechanisms underlying the P2X7 specific properties remain poorly understood, partly because purification of this eukaryotic membrane protein has been challenging. Here we describe a detailed protocol for expressing and purifying a mammalian P2X7 receptor using an insect cell-baculovirus system. The P2X7 receptor is expressed in Sf9 insect cells as a GFP fusion protein and solubilized with a buffer containing Triton X-100 detergent. The P2X7-GFP fusion protein is then purified in a buffer containing dodecyl maltoside using Strep-Tactin affinity chromatography. Following enzymatic cleavage of the attached GFP and Strep-tag by thrombin, the P2X7 receptor is isolated using size exclusion chromatography. This method typically yields ~2 mg of purified protein from 6 L of Sf9 culture. Purified protein can be stored with a buffer containing 15% glycerol at 4 °C for at least 2 months and used for a variety of functional and structural studies (Karasawa and Kawate, 2016).
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Affiliation(s)
- Akira Karasawa
- Department of Molecular Medicine, Cornell University, Ithaca, NY, USA
| | - Toshimitsu Kawate
- Department of Molecular Medicine, Cornell University, Ithaca, NY, USA
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54
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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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55
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Próchnicki T, Mangan MS, Latz E. Recent insights into the molecular mechanisms of the NLRP3 inflammasome activation. F1000Res 2016; 5. [PMID: 27508077 PMCID: PMC4963208 DOI: 10.12688/f1000research.8614.1] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/17/2016] [Indexed: 12/26/2022] Open
Abstract
Inflammasomes are high-molecular-weight protein complexes that are formed in the cytosolic compartment in response to danger- or pathogen-associated molecular patterns. These complexes enable activation of an inflammatory protease caspase-1, leading to a cell death process called pyroptosis and to proteolytic cleavage and release of pro-inflammatory cytokines interleukin (IL)-1β and IL-18. Along with caspase-1, inflammasome components include an adaptor protein, ASC, and a sensor protein, which triggers the inflammasome assembly in response to a danger signal. The inflammasome sensor proteins are pattern recognition receptors belonging either to the NOD-like receptor (NLR) or to the AIM2-like receptor family. While the molecular agonists that induce inflammasome formation by AIM2 and by several other NLRs have been identified, it is not well understood how the NLR family member NLRP3 is activated. Given that NLRP3 activation is relevant to a range of human pathological conditions, significant attempts are being made to elucidate the molecular mechanism of this process. In this review, we summarize the current knowledge on the molecular events that lead to activation of the NLRP3 inflammasome in response to a range of K (+) efflux-inducing danger signals. We also comment on the reported involvement of cytosolic Ca (2+) fluxes on NLRP3 activation. We outline the recent advances in research on the physiological and pharmacological mechanisms of regulation of NLRP3 responses, and we point to several open questions regarding the current model of NLRP3 activation.
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Affiliation(s)
- Tomasz Próchnicki
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany
| | - Matthew S Mangan
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany; German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Eicke Latz
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany; Department of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA, USA; German Center for Neurodegenerative Diseases, Bonn, Germany; Centre of Molecular Inflammation Research, Norwegian University of Science and Technology, Trondheim, Norway
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56
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Hou Z, Cao J. Comparative study of the P2X gene family in animals and plants. Purinergic Signal 2016; 12:269-81. [PMID: 26874702 PMCID: PMC4854843 DOI: 10.1007/s11302-016-9501-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 02/05/2016] [Indexed: 12/22/2022] Open
Abstract
P2X receptors are ligand-gated ion channels that can bind with the adenosine triphosphate (ATP) and have diverse functional roles in neuropathic pain, inflammation, special sense, and so on. In this study, 180 putative P2X genes, including 176 members in 32 animal species and 4 members in 3 species of lower plants, were identified. These genes were divided into 13 groups, including 7 groups in vertebrates and 6 groups in invertebrates and lower plants, through phylogenetic analysis. Their gene organization and motif composition are conserved in most predicted P2X members, while group-specific features were also found. Moreover, synteny relationships of the putative P2X genes in vertebrates are conserved while simultaneously experiencing a series of gene insertion, inversion, and transposition. Recombination signals were detected in almost all of the vertebrates and invertebrates, suggesting that intragenic recombination may play a significant role in the evolution of P2X genes. Selection analysis also identified some positively selected sites that acted on the evolution of most of the predicted P2X proteins. The phenomenon of alternative splicing occurred commonly in the putative P2X genes of vertebrates. This article explored in depth the evolutional relationship among different subtypes of P2X genes in animal and plants and might serve as a solid foundation for deciphering their functions in further studies.
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Affiliation(s)
- Zhuoran Hou
- School of Medicine, Jiangsu University, Zhenjiang, Jiangsu, People's Republic of China
| | - Jun Cao
- Institute of Life Science, Jiangsu University, Zhenjiang, Jiangsu, People's Republic of China.
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57
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Geraghty NJ, Watson D, Adhikary SR, Sluyter R. P2X7 receptor in skin biology and diseases. World J Dermatol 2016; 5:72-83. [DOI: 10.5314/wjd.v5.i2.72] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/23/2015] [Accepted: 01/29/2016] [Indexed: 02/06/2023] Open
Abstract
The P2X7 receptor is a trimeric ligand-gated cation channel present on immune and other cells. Activation of this receptor by its natural ligand extracellular adenosine triphosphate results in a variety of downstream responses, including the release of pro-inflammatory mediators and cell death. In normal skin, P2X7 is present on keratinocytes, Langerhans cells and fibroblasts, while the presence of this receptor on other cutaneous cells is mainly inferred from studies of equivalent cell types present in other tissues. Mast cells in normal skin however express negligible amounts of P2X7, which can be upregulated in cutaneous disease. This review discusses the potential significance of P2X7 in skin biology, and the role of this receptor in inflammatory skin disorders such as irritant and chronic dermatitis, psoriasis, graft-versus-host disease, as well is in wound healing, transplantation and skin cancer.
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58
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De Bock M, Van Haver V, Vandenbroucke RE, Decrock E, Wang N, Leybaert L. Into rather unexplored terrain-transcellular transport across the blood-brain barrier. Glia 2016; 64:1097-123. [DOI: 10.1002/glia.22960] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 11/16/2015] [Accepted: 12/03/2015] [Indexed: 01/22/2023]
Affiliation(s)
- Marijke De Bock
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Valérie Van Haver
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Roosmarijn E. Vandenbroucke
- Inflammation Research Center, VIB; Ghent Belgium
- Department of Biomedical Molecular Biology; Ghent University; Ghent Belgium
| | - Elke Decrock
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Nan Wang
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences; Ghent University; Ghent Belgium
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59
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Ferreira LGB, Faria RX. TRPing on the pore phenomenon: what do we know about transient receptor potential ion channel-related pore dilation up to now? J Bioenerg Biomembr 2016; 48:1-12. [PMID: 26728159 DOI: 10.1007/s10863-015-9634-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 12/02/2015] [Indexed: 01/06/2023]
Abstract
Ion channels allow for rapid ion diffusion through the plasma membrane. In some conditions, ion channels induce changes in the critical plasma membrane permeability that permit 900-Da solutes to enter cells. This process is known as the pore phenomenon. Some transient receptor potential (TRP) channel subtypes have been highlighted such as the P2X7 receptor, plasma membrane VDAC-1 channel, and pannexin hemichannels. The TRP ion channels are considered multimodal transducers that respond to several kinds of stimuli. In addition, many TRP channel subtypes are involved in physiological and pathophysiological processes such as inflammation, pain, and cancer. The TRPA1, TRPM8, and TRPV1-4 subtypes have been shown to promote large-molecular-weight solute uptake, including impermeable fluorescent dyes, QX-314 hydrophilic lidocaine derivative, gabapentin, and antineoplastic drugs. This review discusses the current knowledge of TRP-associated pores and encourages scientists to study their features and explore them as novel therapeutic tools.
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Affiliation(s)
- L G B Ferreira
- Laboratory of Inflammation, Oswaldo Cruz Institute, FIOCRUZ, Av. Brasil, n° 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil.
| | - R X Faria
- Laboratory of Cellular Communication, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, n° 4365, Manguinhos, CEP 21045-900, Rio de Janeiro, Brazil
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60
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Zimmermann H. Extracellular ATP and other nucleotides-ubiquitous triggers of intercellular messenger release. Purinergic Signal 2015; 12:25-57. [PMID: 26545760 DOI: 10.1007/s11302-015-9483-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 10/29/2015] [Indexed: 12/21/2022] Open
Abstract
Extracellular nucleotides, and ATP in particular, are cellular signal substances involved in the control of numerous (patho)physiological mechanisms. They provoke nucleotide receptor-mediated mechanisms in select target cells. But nucleotides can considerably expand their range of action. They function as primary messengers in intercellular communication by stimulating the release of other extracellular messenger substances. These in turn activate additional cellular mechanisms through their own receptors. While this applies also to other extracellular messengers, its omnipresence in the vertebrate organism is an outstanding feature of nucleotide signaling. Intercellular messenger substances released by nucleotides include neurotransmitters, hormones, growth factors, a considerable variety of other proteins including enzymes, numerous cytokines, lipid mediators, nitric oxide, and reactive oxygen species. Moreover, nucleotides activate or co-activate growth factor receptors. In the case of hormone release, the initially paracrine or autocrine nucleotide-mediated signal spreads through to the entire organism. The examples highlighted in this commentary suggest that acting as ubiquitous triggers of intercellular messenger release is one of the major functional roles of extracellular nucleotides. While initiation of messenger release by nucleotides has been unraveled in many contexts, it may have been overlooked in others. It can be anticipated that additional nucleotide-driven messenger functions will be uncovered with relevance for both understanding physiology and development of therapy.
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Affiliation(s)
- Herbert Zimmermann
- Institute of Cell Biology and Neuroscience, Molecular and Cellular Neurobiology, Goethe University, Max-von-Laue-Str. 13, Frankfurt am Main, Germany.
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61
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Ferreira L, Pereira L, Faria R. Fluorescent dyes as a reliable tool in P2X7 receptor-associated pore studies. J Bioenerg Biomembr 2015; 47:283-307. [PMID: 26076670 DOI: 10.1007/s10863-015-9613-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 05/27/2015] [Indexed: 01/09/2023]
Abstract
Since the nineteenth century, a great amount of different biological structures and processes have been assessed by fluorescent dyes. Along with the uses of these compounds as vital and histological dyes, some fluorescent dyes have become valuable tools for the study of the pore phenomenon in plasma membranes. Some ion channels capable of forming large conductance channels, such as P2X7, TRPV1, VDAC-1 and the maxi-anion channels transiently alter the plasma membrane permeability, producing pores, which permit the passage of molecules of up to 1,000 Da. In this review, we discuss the uses of the fluorescent dyes chosen in diverse studies of this topic up to now.
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Affiliation(s)
- Leonardo Ferreira
- Laboratory of Cellular Communication, Oswaldo Cruz Foundation, Av. Brazil 4365, pavilion 108, room 28B Manguinhos, Rio de Janeiro, Brazil, CEP 21040-360,
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62
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An Improved Method for P2X7R Antagonist Screening. PLoS One 2015; 10:e0123089. [PMID: 25993132 PMCID: PMC4437783 DOI: 10.1371/journal.pone.0123089] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 02/27/2015] [Indexed: 11/19/2022] Open
Abstract
ATP physiologically activates the P2X7 receptor (P2X7R), a member of the P2X ionotropic receptor family. When activated by high concentrations of ATP (i.e., at inflammation sites), this receptor is capable of forming a pore that allows molecules of up to 900 Da to pass through. This receptor is upregulated in several diseases, particularly leukemia, rheumatoid arthritis and Alzheimer's disease. A selective antagonist of this receptor could be useful in the treatment of P2X7R activation-related diseases. In the present study, we have evaluated several parameters using in vitro protocols to validate a high-throughput screening (HTS) method to identify P2X7R antagonists. We generated dose-response curves to determine the EC50 value of the known agonist ATP and the ICs50 values for the known antagonists Brilliant Blue G (BBG) and oxidized ATP (OATP). The values obtained were consistent with those found in the literature (0.7 ± 0.07 mM, 1.3-2.6 mM and 173-285 μM for ATP, BBG and OATP, respectively). The Z-factor, an important statistical tool that can be used to validate the robustness and suitability of an HTS assay, was 0.635 for PI uptake and 0.867 for LY uptake. No inter-operator variation was observed, and the results obtained using our improved method were reproducible. Our data indicate that our assay is suitable for the selective and reliable evaluation of P2X7 activity in multiwell plates using spectrophotometry-based methodology. This method might improve the high-throughput screening of conventional chemical or natural product libraries for possible candidate P2X7R antagonist or agonist
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63
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Falk S, Schwab S, Frøsig-Jørgensen M, Clausen R, Dickenson A, Heegaard AM. P2X7 receptor-mediated analgesia in cancer-induced bone pain. Neuroscience 2015; 291:93-105. [DOI: 10.1016/j.neuroscience.2015.02.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 01/19/2015] [Accepted: 02/05/2015] [Indexed: 11/28/2022]
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64
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Schitine CS, Mendez-Flores OG, Santos LE, Ornelas I, Calaza KC, Pérez-Toledo K, López-Bayghen E, Ortega A, Gardino PF, de Mello FG, Reis RA. Functional plasticity of GAT-3 in avian Müller cells is regulated by neurons via a glutamatergic input. Neurochem Int 2015; 82:42-51. [DOI: 10.1016/j.neuint.2015.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 02/09/2015] [Accepted: 02/15/2015] [Indexed: 10/24/2022]
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