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Al-Aqtash R, Collier DM. Ionotropic purinergic receptor 7 (P2X7) channel structure and pharmacology provides insight regarding non-nucleotide agonism. Channels (Austin) 2024; 18:2355150. [PMID: 38762911 PMCID: PMC11110710 DOI: 10.1080/19336950.2024.2355150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 05/10/2024] [Indexed: 05/21/2024] Open
Abstract
P2X7 is a member of the Ionotropic Purinergic Receptor (P2X) family. The P2X family of receptors is composed of seven (P2X1-7), ligand-gated, nonselective cation channels. Changes in P2X expression have been reported in multiple disease models. P2Xs have large complex extracellular domains that function as receptors for a variety of ligands, including endogenous and synthetic agonists and antagonists. ATP is the canonical agonist. ATP affinity ranges from nanomolar to micromolar for most P2XRs, but P2X7 has uniquely poor ATP affinity. In many physiological settings, it may be difficult to achieve the millimolar extracellular ATP concentrations needed for P2X7 channel activation; however, channel function is implicated in pain sensation, immune cell function, cardiovascular disease, cancer, and osteoporosis. Multiple high-resolution P2X7 structures have been solved in apo-, ATP-, and antagonist-bound states. P2X7 structural data reveal distinct allosteric and orthosteric antagonist-binding sites. Both allosteric and orthosteric P2X7 antagonists are well documented to inhibit ATP-evoked channel current. However, a growing body of evidence supports P2X7 activation by non-nucleotide agonists, including extracellular histone proteins and human cathelicidin-derived peptides (LL-37). Interestingly, P2X7 non-nucleotide agonism is not inhibited by allosteric antagonists, but is inhibited by orthosteric antagonists. Herein, we review P2X7 function with a focus on the efficacy of available pharmacology on P2X7 channel current activation by non-nucleotide agonists in effort to understand agonist/antagonist efficacy, and consider the impact of these data on the current understanding of P2X7 in physiology and disease given these limitations of P2X7-selective antagonists and incomplete knockout mouse models.
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Affiliation(s)
- Rua’a Al-Aqtash
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Daniel M. Collier
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
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Thach T, Dhanabalan K, Nandekar PP, Stauffer S, Heisler I, Alvarado S, Snyder J, Subramanian R. A Second Drug Binding Site in P2X3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.10.598171. [PMID: 38915546 PMCID: PMC11195084 DOI: 10.1101/2024.06.10.598171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Purinergic P2X3 receptors form trimeric cation-gated channels, which are activated by extracellular ATP. P2X3 plays a crucial role in chronic cough and affects over 10% of the population. Despite considerable efforts to develop drugs targeting P2X3, the highly conserved structure within the P2X receptor family presents obstacles for achieving selectivity. Camlipixant, a potent and selective P2X3 antagonist, is currently in phase III clinical trials. However, the mechanisms underlying receptor desensitization, ion permeation, principles governing antagonism, and the structure of P2X3 when bound to camlipixant remain elusive. In this study, we established a stable cell line expressing homotrimeric P2X3 and utilized a peptide scaffold to purify the complex and determine its structure using cryo-electron microscopy (cryo-EM). P2X3 binds to camlipixant at a previously unidentified drug-binding site and functions as an allosteric inhibitor. Structure-activity studies combined with modeling and simulations have shed light on the mechanisms underlying the selective targeting and inhibition of P2X3 by camlipixant, distinguishing it from other members of the P2X receptor family.
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Affiliation(s)
- Trung Thach
- Department of Biological Sciences, Purdue University, West Lafayette, IN-47907, USA
| | | | | | - Seth Stauffer
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN-46140, USA
| | - Iring Heisler
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN-46140, USA
| | - Sarah Alvarado
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN-46140, USA
| | - Jonathan Snyder
- Elanco Animal Health, 2500 Innovation Way, Greenfield, IN-46140, USA
| | - Ramaswamy Subramanian
- Department of Biological Sciences, Purdue University, West Lafayette, IN-47907, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN-47907, USA
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Cao B, Xu Q, Shi Y, Zhao R, Li H, Zheng J, Liu F, Wan Y, Wei B. Pathology of pain and its implications for therapeutic interventions. Signal Transduct Target Ther 2024; 9:155. [PMID: 38851750 PMCID: PMC11162504 DOI: 10.1038/s41392-024-01845-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 04/08/2024] [Accepted: 04/25/2024] [Indexed: 06/10/2024] Open
Abstract
Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.
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Affiliation(s)
- Bo Cao
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
| | - Qixuan Xu
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Yajiao Shi
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China
| | - Ruiyang Zhao
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Hanghang Li
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China
- Medical School of Chinese PLA, Beijing, 100853, China
| | - Jie Zheng
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China
| | - Fengyu Liu
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China.
| | - You Wan
- Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, 100191, China.
| | - Bo Wei
- Department of General Surgery, First Medical Center, Chinese PLA General Hospital, Beijing, 100853, China.
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Nagel J, Törmäkangas O, Kuokkanen K, El-Tayeb A, Messinger J, Abdelrahman A, Bous C, Schiedel AC, Müller CE. Preparation and preliminary evaluation of a tritium-labeled allosteric P2X4 receptor antagonist. Purinergic Signal 2024:10.1007/s11302-024-10005-2. [PMID: 38795223 DOI: 10.1007/s11302-024-10005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 03/26/2024] [Indexed: 05/27/2024] Open
Abstract
P2X4 receptors are ATP-gated cation channels that were proposed as novel drug targets due to their role in inflammation and neuropathic pain. Only few potent and selective P2X4 receptor antagonists have been described to date. Labeled tool compounds suitable for P2X4 receptor binding studies are lacking. Here, we present a novel allosteric P2X4 receptor antagonist possessing high potency in the low nanomolar range. We describe its tritium-labeling resulting in the P2X4-selective radiotracer [3H]PSB-OR-2020 with high specific activity (45 Ci/mmol; 1.67 TBq/mmol). A radioligand binding assay was developed using human embryonic kidney (HEK293) cell membranes recombinantly expressing the human P2X4 receptor. Competition binding studies with structurally diverse P2X4 receptor antagonists revealed different allosteric binding sites indicating that the new class of P2X4 receptor antagonists, to which PSB-OR-2020 belongs, interacts with an unprecedented allosteric site. [3H]PSB-OR-2020 may become a useful tool for research on P2X4 receptors and for promoting drug development.
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Affiliation(s)
- Jessica Nagel
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany
| | - Olli Törmäkangas
- Orion Pharma, Orion Corporation, Tengströminkatu 8, FI-20360 Turku, and Orionintie 1A, Espoo, FI- 02200, Finland
| | - Katja Kuokkanen
- Orion Pharma, Orion Corporation, Tengströminkatu 8, FI-20360 Turku, and Orionintie 1A, Espoo, FI- 02200, Finland
| | - Ali El-Tayeb
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany
| | - Josef Messinger
- Orion Pharma, Orion Corporation, Tengströminkatu 8, FI-20360 Turku, and Orionintie 1A, Espoo, FI- 02200, Finland
| | - Aliaa Abdelrahman
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany
| | - Christiane Bous
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany
| | - Anke C Schiedel
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany
| | - Christa E Müller
- PharmaCenter Bonn, Pharmaceutical Institute, University of Bonn, Pharmaceutical & Medicinal Chemistry, An der Immenburg 4, Bonn, 53121, Germany.
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Lu Y, Lin Y, Wang J. Progress on functions of intracellular domain of trimeric ligand-gated ion channels. Zhejiang Da Xue Xue Bao Yi Xue Ban 2024; 53:221-230. [PMID: 38310082 PMCID: PMC11057991 DOI: 10.3724/zdxbyxb-2023-0472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 11/11/2023] [Indexed: 02/05/2024]
Abstract
Ligand-gated ion channels are a large category of essential ion channels, modulating their state by binding to specific ligands to allow ions to pass through the cell membrane. Purinergic ligand-gated ion channel receptors (P2XRs) and acid-sensitive ion channels (ASICs) are representative members of trimeric ligand-gated ion channel. Recent studies have shown that structural differences in the intracellular domain of P2XRs may determine the desensitization process. The lateral fenestrations of P2XRs potentially serve as a pathway for ion conductance and play a decisive role in ion selectivity. Phosphorylation of numerous amino acid residues in the P2XRs are involved in regulating the activity of ion channels. Additionally, the P2XRs interact with other ligand-gated ion channels including N-methyl-D-aspartate receptors, γ-aminobutyric acid receptors, 5-hydroxytryptamin receptors and nicotinic acetylcholine receptors, mediating physiological processes such as synaptic plasticity. Conformational changes in the intracellular domain of the ASICs expose binding sites of intracellular signal partners, facilitating metabolic signal transduction. Amino acids such as Val16, Ser17, Ile18, Gln19 and Ala20 in the ASICs participate in channel opening and membrane expression. ASICs can also bind to intracellular proteins, such as CIPP and p11, to regulate channel function. Many phosphorylation sites at the C-terminus and N-terminus of ASICs are involved in the regulation of receptors. Furthermore, ASICs are involved in various physiological and pathophysiological processes, which include pain, ischemic stroke, psychiatric disorders, and neurodegenerative disease. In this article, we review the roles of the intracellular domains of these trimeric ligand-gated ion channels in channel gating as well as their physiological and pathological functions, in order to provide new insights into the discovery of related drugs.
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Affiliation(s)
- Yan Lu
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing 210009, China.
| | - Yiyu Lin
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing 210009, China
| | - Jin Wang
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing 210009, China.
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Sheng D, Yue CX, Jin F, Wang Y, Ichikawa M, Yu Y, Guo CR, Hattori M. Structural insights into the orthosteric inhibition of P2X receptors by non-ATP analog antagonists. eLife 2024; 12:RP92829. [PMID: 38578670 PMCID: PMC10997329 DOI: 10.7554/elife.92829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024] Open
Abstract
P2X receptors are extracellular ATP-gated ion channels that form homo- or heterotrimers and consist of seven subtypes. They are expressed in various tissues, including neuronal and nonneuronal cells, and play critical roles in physiological processes such as neurotransmission, inflammation, pain, and cancer. As a result, P2X receptors have attracted considerable interest as drug targets, and various competitive inhibitors have been developed. However, although several P2X receptor structures from different subtypes have been reported, the limited structural information of P2X receptors in complex with competitive antagonists hampers the understanding of orthosteric inhibition, hindering the further design and optimization of those antagonists for drug discovery. We determined the cryogenic electron microscopy (cryo-EM) structures of the mammalian P2X7 receptor in complex with two classical competitive antagonists of pyridoxal-5'-phosphate derivatives, pyridoxal-5'-phosphate-6-(2'-naphthylazo-6'-nitro-4',8'-disulfonate) (PPNDS) and pyridoxal phosphate-6-azophenyl-2',5'-disulfonic acid (PPADS), and performed structure-based mutational analysis by patch-clamp recording as well as molecular dynamics (MD) simulations. Our structures revealed the orthosteric site for PPADS/PPNDS, and structural comparison with the previously reported apo- and ATP-bound structures showed how PPADS/PPNDS binding inhibits the conformational changes associated with channel activation. In addition, structure-based mutational analysis identified key residues involved in the PPNDS sensitivity of P2X1 and P2X3, which are known to have higher affinity for PPADS/PPNDS than other P2X subtypes.
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Affiliation(s)
- Danqi Sheng
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan UniversityShanghaiChina
| | - Chen-Xi Yue
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical UniversityNanjingChina
| | - Fei Jin
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan UniversityShanghaiChina
| | - Yao Wang
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan UniversityShanghaiChina
| | - Muneyoshi Ichikawa
- State Key Laboratory of Genetic Engineering, Department of Biochemistry and Biophysics, School of Life Sciences, Fudan UniversityShanghaiChina
| | - Ye Yu
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical UniversityNanjingChina
| | - Chang-Run Guo
- School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical UniversityNanjingChina
| | - Motoyuki Hattori
- State Key Laboratory of Genetic Engineering, Shanghai Key Laboratory of Bioactive Small Molecules, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Neurobiology, School of Life Sciences, Fudan UniversityShanghaiChina
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Witkin JM, Shafique H, Smith JL, Cerne R. Is there a biochemical basis for purinergic P2X3 and P2X4 receptor antagonists to be considered as anti-seizure medications? Biochem Pharmacol 2024; 222:116046. [PMID: 38341001 DOI: 10.1016/j.bcp.2024.116046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 12/15/2023] [Accepted: 02/05/2024] [Indexed: 02/12/2024]
Abstract
Patients with epilepsy require improved medications. Purinergic receptors were identified as late as 1976 and are slowly emerging as potential drug targets for the discovery of antiseizure medications. While compounds interacting with these receptors have been approved for use as medicines (e.g., gefapixant for cough) and continue to be explored for a number of diseases (e.g., pain, cancer), there have been no purinergic receptor antagonists that have been advanced for epilepsy. There are very few studies on the channel conducting receptors, P2X3 and P2X4, that suggest their possible role in seizure generation or control. However, the limited data available provides some compelling reasons to believe that they could be valuable antiseizure medication drug targets. The data implicating P2X3 and P2X4 receptors in epilepsy includes the role played by ATP in neuronal excitability and seizures, receptor localization, increased receptor expression in epileptic brain, the involvement of these receptors in seizure-associated inflammation, crosstalk between these purinergic receptors and neuronal processes involved in seizures (GABAergic and glutamatergic neurotransmission), and the significant attenuation of seizures and seizure-like activity with P2X receptor blockade. The discovery of new and selective antagonists for P2X3 and P2X4 receptors is ongoing, armed with new structural data to guide rational design. The availability of safe, brain-penetrant compounds will likely encourage the clinical exploration of epilepsy as a disease entity.
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Affiliation(s)
- Jeffrey M Witkin
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN, USA; Department of Neuroscience and Trauma Research, Ascension St. Vincent, Indianapolis, IN, USA; Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
| | | | - Jodi L Smith
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN, USA
| | - Rok Cerne
- Laboratory of Antiepileptic Drug Discovery, Ascension St. Vincent, Indianapolis, IN, USA; Department of Anatomy and Cell Biology, Indiana University/Purdue University, Indianapolis, IN, USA; Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
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Sluyter R, McEwan TBD, Sophocleous RA, Stokes L. Methods for studying P2X4 receptor ion channels in immune cells. J Immunol Methods 2024; 526:113626. [PMID: 38311008 DOI: 10.1016/j.jim.2024.113626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 01/28/2024] [Accepted: 02/01/2024] [Indexed: 02/06/2024]
Abstract
The P2X4 receptor is a trimeric ligand-gated ion channel activated by adenosine 5'-triphosphate (ATP). P2X4 is present in immune cells with emerging roles in inflammation and immunity, and related disorders. This review aims to provide an overview of the methods commonly used to study P2X4 in immune cells, focusing on those methods used to assess P2RX4 gene expression, the presence of the P2X4 protein, and P2X4 ion channel activity in these cells from humans, dogs, mice and rats. P2RX4 gene expression in immune cells is commonly assessed using semi-quantitative and quantitative reverse-transcriptase-PCR. The presence of P2X4 protein in immune cells is mainly assessed using anti-P2X4 polyclonal antibodies with immunoblotting or immunochemistry, but the use of these antibodies, as well as monoclonal antibodies and nanobodies to detect P2X4 with flow cytometry is increasing. Notably, use of an anti-P2X4 monoclonal antibody and flow cytometry has revealed that P2X4 is present on immune cells with a rank order of expression in eosinophils, then neutrophils and monocytes, then basophils and B cells, and finally T cells. P2X4 ion channel activity has been assessed mainly by Ca2+ flux assays using the cell permeable Ca2+-sensitive dyes Fura-2 and Fluo-4 with fluorescence microscopy, spectrophotometry, or flow cytometry. However, other methods including electrophysiology, and fluorescence assays measuring Na+ flux (using sodium green tetra-acetate) and dye uptake (using YO-PRO-12+) have been applied. Collectively, these methods have demonstrated the presence of functional P2X4 in monocytes and macrophages, microglia, eosinophils, mast cells and CD4+ T cells, with other evidence suggestive of functional P2X4 in dendritic cells, neutrophils, B cells and CD8+ T cells.
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Affiliation(s)
- Ronald Sluyter
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia.
| | - Tahnee B-D McEwan
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Reece A Sophocleous
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Leanne Stokes
- School of Pharmacy, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK
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