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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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Chen IS, Yasuda J, Notomi T, Nakamura TY. Licorice metabolite 18β-glycyrrhetinic acid activates G protein-gated inwardly rectifying K + channels. Br J Pharmacol 2024; 181:447-463. [PMID: 37642133 DOI: 10.1111/bph.16228] [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: 02/24/2023] [Revised: 08/16/2023] [Accepted: 08/22/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND AND PURPOSE Licorice (liquorice) is a common food additive and is used in Chinese medicine. Excess licorice intake can induce atrial fibrillation. Patients with atrial fibrillation possess constitutively activated G protein-gated inwardly rectifying K+ (GIRK) channels. Whether licorice affects GIRK channel activity is unknown. We aimed to clarify the effects of licorice ingredients on GIRK current and the mechanism of action. EXPERIMENTAL APPROACH A major component of licorice, glycyrrhizic acid (GA), and its metabolite, 18β-glycyrrhetinic acid (18β-GA), were tested. We performed electrophysiological recordings in Xenopus oocytes to examine the effects of GA and 18β-GA on various GIRK subunits (Kir 3.1-Kir 3.4), mutagenesis analyses to identify the crucial residues for drug action and motion analysis in cultured rat atrial myocytes to clarify effects of 18β-GA on atrial functions. KEY RESULTS GA inhibited Kir 3.1-containing channels, while 18β-GA activated all Kir 3.x subunits. A pore helix residue Phe137 in Kir 3.1 was critical for GA-mediated inhibition, and the corresponding Ser148 in Kir 3.2 was critical for 18β-GA-mediated activation. 18β-GA activated GIRK channel in a Gβγ -independent manner, whereas phosphatidylinositol 4,5-bisphosphate (PIP2 ) was essential for activation. Glu236 located at the cytoplasmic pore of Kir 3.2 appeared to be important to interactions with 18β-GA. In rat atrial myocytes, 18β-GA suppressed spontaneous beating via activation of GIRK channels. CONCLUSION AND IMPLICATIONS GA acts as a novel GIRK inhibitor, and 18β-GA acts as a novel GIRK activator. 18β-GA alters atrial function via activation of GIRK channels. This study elucidates the pharmacological activity of licorice ingredients and provides information for drug design.
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Affiliation(s)
- I-Shan Chen
- Department of Pharmacology, Faculty of Medicine, Wakayama Medical University, Wakayama, Japan
| | - Jumpei Yasuda
- Department of Pharmacology, Faculty of Medicine, Wakayama Medical University, Wakayama, Japan
| | - Takuya Notomi
- Department of Pharmacology, Faculty of Medicine, Wakayama Medical University, Wakayama, Japan
| | - Tomoe Y Nakamura
- Department of Pharmacology, Faculty of Medicine, Wakayama Medical University, Wakayama, Japan
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Stojilkovic SS, Balla T. PI(4,5)P2-dependent and -independent roles of PI4P in the control of hormone secretion by pituitary cells. Front Endocrinol (Lausanne) 2023; 14:1118744. [PMID: 36777340 PMCID: PMC9911653 DOI: 10.3389/fendo.2023.1118744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 01/03/2023] [Indexed: 01/28/2023] Open
Abstract
Plasma membrane and organelle membranes are home to seven phosphoinositides, an important class of low-abundance anionic signaling lipids that contribute to cellular functions by recruiting cytoplasmic proteins or interacting with the cytoplasmic domains of membrane proteins. Here, we briefly review the functions of three phosphoinositides, PI4P, PI(4,5)P2, and PI(3,4,5)P3, in cellular signaling and exocytosis, focusing on hormone-producing pituitary cells. PI(4,5)P2, acting as a substrate for phospholipase C, plays a key role in the control of pituitary cell functions, including hormone synthesis and secretion. PI(4,5)P2 also acts as a substrate for class I PI3-kinases, leading to the generation of two intracellular messengers, PI(3,4,5)P3 and PI(3,4)P2, which act through their intracellular effectors, including Akt. PI(4,5)P2 can also influence the release of pituitary hormones acting as an intact lipid to regulate ion channel gating and concomitant calcium signaling, as well as the exocytic pathway. Recent findings also show that PI4P is not only a precursor of PI(4,5)P2, but also a key signaling molecule in many cell types, including pituitary cells, where it controls hormone secretion in a PI(4,5)P2-independent manner.
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Affiliation(s)
- Stanko S. Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Stanko S. Stojilkovic,
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
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Du T, Zhou X, Zhang RDY, Du XF. Roles of Ca2+ activity in injury-induced migration of microglia in zebrafish in vivo. Biochem Biophys Rep 2022; 32:101340. [PMID: 36120493 PMCID: PMC9471311 DOI: 10.1016/j.bbrep.2022.101340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/21/2022] [Accepted: 08/30/2022] [Indexed: 10/28/2022] Open
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P2X4 receptor stimulation enhances MrgprB2-mediated mast cell activation and pseudoallergic reactions in mice. Sci Rep 2022; 12:18613. [PMID: 36329102 PMCID: PMC9633816 DOI: 10.1038/s41598-022-21667-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/29/2022] [Indexed: 11/06/2022] Open
Abstract
Pseudoallergies caused by drugs make disease treatment difficult. Mas-relate G protein-coupled receptor X2 (MRGPRX2), which is specifically expressed in mast cells (MCs), has been implicated in pseudoallergies. High concentrations of therapeutic agents are typically required to stimulate MRGPRX2. Although regulatory mechanisms may enhance this response, the factors involved in this regulation are not well-understood. In this study, the effects of extracellular ATP on MC activation induced by MrgprB2, the mouse ortholog of human MRGPRX2, were examined in mouse peritoneal MCs (PMCs). ATP alone induced minimal PMC degranulation but markedly enhanced degranulation induced by the MrgprB2 agonist compound 48/80 (CP48/80), substance P, PAMP-12, and vancomycin. ATP promoted CP48/80-induced increase in intracellular Ca2+ in PMCs. This enhancement effect of ATP was absent in PMCs prepared from P2X4 receptor (P2X4R)-deficient mice and inhibited by the PI3K inhibitor wortmannin. In addition, P2X4R deficiency reduced the skin-specific and systemic anaphylactic responses to CP48/80 in vivo. In MC-deficient KitW-sh/W-sh mice, reconstitution with MCs obtained from wild-type mice led to a more severe anaphylactic response to CP48/80 compared to that from P2X4R-deficient mice. P2X4R-mediated effect may be involved in MrgprB2-mediated MC activation in vivo and is a potential target for alleviating pseudoallergic reactions.
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Matsuoka I, Yoshida K, Ito MA. Purinergic regulation of mast cell function: P2X4 receptor-mediated enhancement of allergic responses. J Pharmacol Sci 2022; 150:94-99. [PMID: 36055757 DOI: 10.1016/j.jphs.2022.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 07/24/2022] [Accepted: 07/26/2022] [Indexed: 10/15/2022] Open
Abstract
Adenosine triphosphate (ATP) initially attracted attention as a neurotransmitter, with much research conducted on the regulation of neurotransmission in the autonomic and central nervous systems. ATP is also abundant as an energy currency in all living cells and is released into extracellular spaces by various regulated mechanisms. The role of ATP and related purine and pyrimidine nucleotides as extracellular signaling molecules in the regulation of immune cell functions has been reported as evidence for purinergic signaling and has become the focus of attention as therapeutic targets for various diseases. Mast cells (MCs) are distributed in tissues in contact with the outside environment and are the first immune cells to respond to non-microbial environmental antigens. Although extracellular ATP is known as an activator of MCs, the details remain to be investigated. Based on our series of studies, this review describes the unique features of ionotropic P2X4 receptor signals in MC functions. The role of purinergic signaling may exist in combination with various physiological, chemical and physical stimuli. The characteristics of P2X4 receptor-mediated action in MCs described in this article may provide clues to reveal the previously unknown effects induced by purinergic signaling.
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Affiliation(s)
- Isao Matsuoka
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Kazuki Yoshida
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan
| | - Masa-Aki Ito
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan
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de la Cruz L, Kushmerick C, Sullivan JM, Kruse M, Vivas O. Hippocampal neurons maintain a large PtdIns(4)P pool that results in faster PtdIns(4,5)P2 synthesis. J Gen Physiol 2022; 154:213016. [PMID: 35179558 PMCID: PMC8906353 DOI: 10.1085/jgp.202113001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 01/01/2022] [Accepted: 01/24/2022] [Indexed: 12/24/2022] Open
Abstract
PtdIns(4,5)P2 is a signaling lipid central to the regulation of multiple cellular functions. It remains unknown how PtdIns(4,5)P2 fulfills various functions in different cell types, such as regulating neuronal excitability, synaptic release, and astrocytic function. Here, we compared the dynamics of PtdIns(4,5)P2 synthesis in hippocampal neurons and astrocytes with the kidney-derived tsA201 cell line. The experimental approach was to (1) measure the abundance and rate of PtdIns(4,5)P2 synthesis and precursors using specific biosensors, (2) measure the levels of PtdIns(4,5)P2 and its precursors using mass spectrometry, and (3) use a mathematical model to compare the metabolism of PtdIns(4,5)P2 in cell types with different proportions of phosphoinositides. The rate of PtdIns(4,5)P2 resynthesis in hippocampal neurons after depletion by cholinergic or glutamatergic stimulation was three times faster than for tsA201 cells. In tsA201 cells, resynthesis of PtdIns(4,5)P2 was dependent on the enzyme PI4K. In contrast, in hippocampal neurons, the resynthesis rate of PtdIns(4,5)P2 was insensitive to the inhibition of PI4K, indicating that it does not require de novo synthesis of the precursor PtdIns(4)P. Measurement of phosphoinositide abundance indicated a larger pool of PtdIns(4)P, suggesting that hippocampal neurons maintain sufficient precursor to restore PtdIns(4,5)P2 levels. Quantitative modeling indicates that the measured differences in PtdIns(4)P pool size and higher activity of PI4K can account for the experimental findings and indicates that high PI4K activity prevents depletion of PtdIns(4)P. We further show that the resynthesis of PtdIns(4,5)P2 is faster in neurons than astrocytes, providing context to the relevance of cell type–specific mechanisms to sustain PtdIns(4,5)P2 levels.
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Affiliation(s)
- Lizbeth de la Cruz
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Christopher Kushmerick
- Department of Physiology and Biophysics, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Jane M Sullivan
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Martin Kruse
- Department of Biology and Program in Neuroscience, Bates College, Lewiston, ME
| | - Oscar Vivas
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
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Nadzirin IB, Fortuny-Gomez A, Ngum N, Richards D, Ali S, Searcey M, Fountain SJ. Taspine is a natural product that suppresses P2X4 receptor activity via phosphoinositide 3-kinase inhibition. Br J Pharmacol 2021; 178:4859-4872. [PMID: 34398973 DOI: 10.1111/bph.15663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 07/28/2021] [Accepted: 08/03/2021] [Indexed: 10/20/2022] Open
Abstract
BACKGROUND & PURPOSE P2X4 is a ligand-gated cation channel activated by extracellular ATP, involved in neuropathic pain, inflammation and arterial tone. EXPERIMENTAL APPROACH Natural products were screened against human or mouse P2X4 activity using fura-2 loaded 1321N1 cells for measurement of intracellular Ca2+ responses; whole-cell currents were measured by patch clamp electrophysiological. Human primary macrophage chemokine release was used to assess effect of taspine on inflammatory cell function. An enzymatic assay was performed to assess the effect of taspine on recombinant PI3-kinase. KEY RESULTS A natural product screen identified taspine as an inhibitor of human P2X4 activity. Taspine inhibits human and mouse P2X4-mediated Ca2+ influx in 1321N1 cells expressing receptors (IC50 1.6±0.4 μM and 1.6±0.3 μM, respectively), but lacked activity at human P2X2, P2X3, P2X2/3 and P2X7 receptors. Taspine inhibited the maximal response at human and mouse P2X4 but had no effect on ATP potency. Taspine has a slow onset rate (~15 mins for half-maximal inhibition), irreversible over 30 minutes of washout. Taspine inhibits P2X4-mediated Ca2+ signalling in mouse BV-2 microglia cells and human primary macrophage. Taspine inhibited P2X4-mediated CXCL5 secretion in human primary macrophage. Taspine reversed ivermectin-induced potentiation of P2X4 currents in 1321N1 stably expressing cells. The known PI3-kinase inhibitor LY294002 mimicked the properties of taspine on P2X4-mediated Ca2+ influx and whole-cell currents. Taspine directly inhibited the enzymatic activity of recombinant PI3-kinase in a competitive manner. CONCLUSIONS AND IMPLICATIONS Taspine is a novel natural product P2X4 inhibitor, mediating its effect through PI3-kinase inhibitor rather than receptor antagonism. Taspine can inhibit the pro-inflammatory signalling by P2X4 in human primary macrophage.
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Affiliation(s)
- Izzuddin Bin Nadzirin
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park.,Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kuantan Campus, Kuantan, Malaysia
| | - Anna Fortuny-Gomez
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park
| | - Neville Ngum
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park
| | - David Richards
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park
| | - Seema Ali
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park
| | - Mark Searcey
- School of Pharmacy, University of East Anglia, Norwich Research Park
| | - Samuel J Fountain
- Biomedical Research Centre, School of Biological Sciences, University of East Anglia, Norwich Research Park
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Ernest James Phillips T, Maguire E. Phosphoinositides: Roles in the Development of Microglial-Mediated Neuroinflammation and Neurodegeneration. Front Cell Neurosci 2021; 15:652593. [PMID: 33841102 PMCID: PMC8032904 DOI: 10.3389/fncel.2021.652593] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 03/08/2021] [Indexed: 12/11/2022] Open
Abstract
Microglia are increasingly recognized as vital players in the pathology of a variety of neurodegenerative conditions including Alzheimer’s (AD) and Parkinson’s (PD) disease. While microglia have a protective role in the brain, their dysfunction can lead to neuroinflammation and contributes to disease progression. Also, a growing body of literature highlights the seven phosphoinositides, or PIPs, as key players in the regulation of microglial-mediated neuroinflammation. These small signaling lipids are phosphorylated derivates of phosphatidylinositol, are enriched in the brain, and have well-established roles in both homeostasis and disease.Disrupted PIP levels and signaling has been detected in a variety of dementias. Moreover, many known AD disease modifiers identified via genetic studies are expressed in microglia and are involved in phospholipid metabolism. One of these, the enzyme PLCγ2 that hydrolyzes the PIP species PI(4,5)P2, displays altered expression in AD and PD and is currently being investigated as a potential therapeutic target.Perhaps unsurprisingly, neurodegenerative conditions exhibiting PIP dyshomeostasis also tend to show alterations in aspects of microglial function regulated by these lipids. In particular, phosphoinositides regulate the activities of proteins and enzymes required for endocytosis, toll-like receptor signaling, purinergic signaling, chemotaxis, and migration, all of which are affected in a variety of neurodegenerative conditions. These functions are crucial to allow microglia to adequately survey the brain and respond appropriately to invading pathogens and other abnormalities, including misfolded proteins. AD and PD therapies are being developed to target many of the above pathways, and although not yet investigated, simultaneous PIP manipulation might enhance the beneficial effects observed. Currently, only limited therapeutics are available for dementia, and although these show some benefits for symptom severity and progression, they are far from curative. Given the importance of microglia and PIPs in dementia development, this review summarizes current research and asks whether we can exploit this information to design more targeted, or perhaps combined, dementia therapeutics. More work is needed to fully characterize the pathways discussed in this review, but given the strength of the current literature, insights in this area could be invaluable for the future of neurodegenerative disease research.
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Affiliation(s)
| | - Emily Maguire
- UK Dementia Research Institute at Cardiff University, Cardiff, United Kingdom
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Yoshida K. [Elucidation of Mast Cell Activation Mechanism Mediated by Purinergic Signaling]. YAKUGAKU ZASSHI 2021; 141:1057-1061. [PMID: 34471006 DOI: 10.1248/yakushi.21-00113] [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] [Indexed: 11/22/2022]
Abstract
Mast cells (MCs) are immune cells that are distributed in all tissues throughout the body, and their cytoplasm is rich in granules containing histamine and tryptase. When MCs recognize antigens through IgE bound to FcεRI, they release these mediators by degranulation. Because degranulation induces various type I allergic reactions, such as anaphylactic shock and hay fever, elucidation of the control mechanism of degranulation is important to the development of a therapeutic strategy for allergic diseases. It is known that the antigen-induced degranulation response is fine-tuned by various humoral factors via the activation of G protein-coupled receptors. We found that extracellular ATP enhanced antigen-dependent and -independent MC degranulation via activation of ionotropic P2X4 receptors. P2X4 receptor activation itself had no effect on MC degranulation, but significantly enhanced antigen-triggered degranulation. Stimulation of the P2X4 receptor potentiated the FcεRI-mediated tyrosine kinase signaling cascade. In addition to antigen-induced responses, P2X4 receptor signaling also affected antigen-independent MC responses. Thus, co-stimulation of ATP and Gi-coupled receptor agonists, such as prostaglandin E2 (PGE2) and adenosine, resulted in synergistic degranulation. The significance of P2X4 receptor signaling in allergic and inflammatory responses in vivo was confirmed by impaired responses of antigen-induced passive anaphylaxis and PGE2-induced increases in vascular permeability in P2rx4 knockout mice compared to that of wild-type mice. These results suggest that the P2X4 receptor is a potential therapeutic target for both antigen-dependent and -independent allergic reactions.
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Affiliation(s)
- Kazuki Yoshida
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare
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Illes P, Müller CE, Jacobson KA, Grutter T, Nicke A, Fountain SJ, Kennedy C, Schmalzing G, Jarvis MF, Stojilkovic SS, King BF, Di Virgilio F. Update of P2X receptor properties and their pharmacology: IUPHAR Review 30. Br J Pharmacol 2020; 178:489-514. [PMID: 33125712 PMCID: PMC8199792 DOI: 10.1111/bph.15299] [Citation(s) in RCA: 164] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 12/20/2022] Open
Abstract
The known seven mammalian receptor subunits (P2X1–7) form cationic channels gated by ATP. Three subunits compose a receptor channel. Each subunit is a polypeptide consisting of two transmembrane regions (TM1 and TM2), intracellular N- and C-termini, and a bulky extracellular loop. Crystallization allowed the identification of the 3D structure and gating cycle of P2X receptors. The agonist-binding pocket is located at the intersection of two neighbouring subunits. In addition to the mammalian P2X receptors, their primitive ligand-gated counterparts with little structural similarity have also been cloned. Selective agonists for P2X receptor subtypes are not available, but medicinal chemistry supplied a range of subtype-selective antagonists, as well as positive and negative allosteric modulators. Knockout mice and selective antagonists helped to identify pathological functions due to defective P2X receptors, such as male infertility (P2X1), hearing loss (P2X2), pain/cough (P2X3), neuropathic pain (P2X4), inflammatory bone loss (P2X5), and faulty immune reactions (P2X7).
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Affiliation(s)
- Peter Illes
- Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.,International Collaborative Centre on Big Science Plan for Purinergic Signalling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Christa E Müller
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, Bonn, Germany
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Thomas Grutter
- University of Strasbourg, Centre National de la Recherche Scientifique, CAMB UMR 7199, Strasbourg, France
| | - Annette Nicke
- Walther Straub Institute for Pharmacology and Toxicology, Ludwig-Maximilians-Universität München, Munich, Germany
| | | | - Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Günther Schmalzing
- Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany
| | | | - Stanko S Stojilkovic
- Section on Cellular Signaling, The Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Brian F King
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Francesco Di Virgilio
- Department of Medical Sciences, Section of Experimental Medicine, University of Ferrara, Ferrara, Italy
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Resolving the Ionotropic P2X4 Receptor Mystery Points Towards a New Therapeutic Target for Cardiovascular Diseases. Int J Mol Sci 2020; 21:ijms21145005. [PMID: 32679900 PMCID: PMC7404342 DOI: 10.3390/ijms21145005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/09/2020] [Accepted: 07/13/2020] [Indexed: 12/18/2022] Open
Abstract
Adenosine triphosphate (ATP) is a primordial versatile autacoid that changes its role from an intracellular energy saver to a signaling molecule once released to the extracellular milieu. Extracellular ATP and its adenosine metabolite are the main activators of the P2 and P1 purinoceptor families, respectively. Mounting evidence suggests that the ionotropic P2X4 receptor (P2X4R) plays pivotal roles in the regulation of the cardiovascular system, yet further therapeutic advances have been hampered by the lack of selective P2X4R agonists. In this review, we provide the state of the art of the P2X4R activity in the cardiovascular system. We also discuss the role of P2X4R activation in kidney and lungs vis a vis their interplay to control cardiovascular functions and dysfunctions, including putative adverse effects emerging from P2X4R activation. Gathering this information may prompt further development of selective P2X4R agonists and its translation to the clinical practice.
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13
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Villalba-Galea CA. Modulation of K V7 Channel Deactivation by PI(4,5)P 2. Front Pharmacol 2020; 11:895. [PMID: 32636742 PMCID: PMC7318307 DOI: 10.3389/fphar.2020.00895] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 06/02/2020] [Indexed: 01/16/2023] Open
Abstract
The activity of KV7 channels critically contributes to the regulation of cellular electrical excitability in many cell types. In the central nervous system, the heteromeric KV7.2/KV7.3 channel is thought to be the chief molecular entity giving rise to M-currents. These K+-currents as so called because they are inhibited by the activation of Gq protein-coupled muscarinic receptors. In general, activation of Gq protein-coupled receptors (GqPCRs) decreases the concentration of the phosphoinositide PI(4,5)P2 which is required for KV7 channel activity. It has been recently reported that the deactivation rate of KV7.2/KV7.3 channels decreases as a function of activation. This suggests that the activated/open channel stabilizes as activation persists. This property has been regarded as evidence for the existence of modal behavior in the activity of these channels. In particular, it has been proposed that the heteromeric KV7.2/KV7.3 channel has at least two modes of activity that can be distinguished by both their deactivation kinetics and sensitivity to Retigabine. The current study was aimed at understanding the effect of PI(4,5)P2 depletion on the modal behavior of KV7.2/KV7.3 channels. Here, it was hypothesized that depleting the membrane of P(4,5)P2 would hamper the stabilization of the activated/open channel, resulting in higher rates of deactivation of the heteromeric KV7.2/KV7.3 channel. In addressing this question, it was found that the activity-dependent slowdown of the deactivation was not as prominent when channels were co-expressed with the chimeric phosphoinositide-phosphatase Ci-VS-TPIP or when cells were treated with the phosphoinositide kinase inhibitor Wortmannin. Further, it was observed that either of these approaches to deplete PI(4,5)P2 had a higher impact on the kinetic of deactivation following prolonged activation, while having little or no effect when activation was short-lived. Furthermore, it was observed that the action of either Ci-VS-TPIP or Wortmannin reduced the effect of Retigabine on the kinetics of deactivation, having a higher impact when activation was prolonged. These combined observations led to the conclusion that the deactivation kinetic of KV7.2/KV7.3 channels was sensitive to PI(4,5)P2 depletion in an activation-dependent manner, displaying a stronger effect on deactivation following prolonged activation.
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Affiliation(s)
- Carlos A. Villalba-Galea
- Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy, University of the Pacific, Stockton, CA, United States
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14
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Stokes L, Bidula S, Bibič L, Allum E. To Inhibit or Enhance? Is There a Benefit to Positive Allosteric Modulation of P2X Receptors? Front Pharmacol 2020; 11:627. [PMID: 32477120 PMCID: PMC7235284 DOI: 10.3389/fphar.2020.00627] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/21/2020] [Indexed: 12/15/2022] Open
Abstract
The family of ligand-gated ion channels known as P2X receptors were discovered several decades ago. Since the cloning of the seven P2X receptors (P2X1-P2X7), a huge research effort has elucidated their roles in regulating a range of physiological and pathophysiological processes. Transgenic animals have been influential in understanding which P2X receptors could be new therapeutic targets for disease. Furthermore, understanding how inherited mutations can increase susceptibility to disorders and diseases has advanced this knowledge base. There has been an emphasis on the discovery and development of pharmacological tools to help dissect the individual roles of P2X receptors and the pharmaceutical industry has been involved in pushing forward clinical development of several lead compounds. During the discovery phase, a number of positive allosteric modulators have been described for P2X receptors and these have been useful in assigning physiological roles to receptors. This review will consider the major physiological roles of P2X1-P2X7 and discuss whether enhancement of P2X receptor activity would offer any therapeutic benefit. We will review what is known about identified compounds acting as positive allosteric modulators and the recent identification of drug binding pockets for such modulators.
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Affiliation(s)
- Leanne Stokes
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Stefan Bidula
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Lučka Bibič
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
| | - Elizabeth Allum
- School of Pharmacy, University of East Anglia, Norwich, United Kingdom
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15
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Zhang WJ, Zhu ZM, Liu ZX. The role of P2X4 receptor in neuropathic pain and its pharmacological properties. Pharmacol Res 2020; 158:104875. [PMID: 32407956 DOI: 10.1016/j.phrs.2020.104875] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 03/02/2020] [Accepted: 04/24/2020] [Indexed: 12/21/2022]
Abstract
Neuropathic pain (NPP) is a common symptom of most diseases in clinic, which seriously affects the mental health of patients and brings certain pain to patients. Due to its pathological mechanism is very complicated, and thus, its treatment has been one of the challenges in the field of medicine. Therefore, exploring the pathogenesis and treatment approach of NPP has aroused the interest of many researchers. ATP is an important energy information substance, which participates in the signal transmission in the body. The P2 × 4 receptor (P2 × 4R) is dependent on ATP ligand-gated cationic channel receptor, which can be activated by ATP and plays an important role in the transmission of information in the nervous system and the formation of pain. In this paper, we provide a comprehensive review of the structure and function of the P2 × 4R gene. We also discuss the pathogenesis of NPP and the intrinsic relationship between P2 × 4R and NPP. Moreover, we explore the pharmacological properties of P2 × 4R antagonists or inhibitors used as targeted therapies for NPP.
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Affiliation(s)
- Wen-Jun Zhang
- The Second Affiliated Hospital, Nanchang University, Nanchang City, Jiangxi province, 343000, China.
| | - Zheng-Ming Zhu
- The Second Affiliated Hospital, Nanchang University, Nanchang City, Jiangxi province, 343000, China.
| | - Zeng-Xu Liu
- Basic Medicine, Nanchang University, Nanchang City, Jiangxi province, 343000, China
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16
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Soto P, Gaete PS, Fuentes C, Lozano B, Naulin PA, Figueroa XF, Barrera NP. Function of P2X4 Receptors Is Directly Modulated by a 1:1 Stoichiometric Interaction With 5-HT 3A Receptors. Front Cell Neurosci 2020; 14:106. [PMID: 32431598 PMCID: PMC7214622 DOI: 10.3389/fncel.2020.00106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/07/2020] [Indexed: 12/30/2022] Open
Abstract
Interacting receptors at the neuronal plasma membrane represent an additional regulatory mode for intracellular transduction pathways. P2X4 receptor triggers fast neurotransmission responses via a transient increase in intracellular Ca2+ levels. It has been proposed that the P2X4 receptor interacts with the 5-HT3A receptor in hippocampal neurons, but their binding stoichiometry and the role of P2X4 receptor activation by ATP on this crosstalking system remains unknown. Via pull-down assays, total internal reflection fluorescence (TIRF) microscopy measurements of the receptors colocalization and expression at the plasma membrane, and atomic force microscopy (AFM) imaging, we have demonstrated that P2X4/5-HT3A receptor complexes can interact with each other in a 1:1 stoichiometric manner that is preserved after ATP binding. Also, macromolecular docking followed by 100 ns molecular dynamics (MD) simulations suggested that the interaction energy of the P2X4 receptor with 5-HT3A receptor is similar at the holo and the apo state of the P2X4 receptor, and the interacting 5-HT3A receptor decreased the ATP binding energy of P2X4 receptor. Finally, the P2X4 receptor-dependent Ca2+ mobilization is inhibited by the 5-HT3A interacting receptor. Altogether, these findings provide novel molecular insights into the allosteric regulation of P2X4/5-HT3A receptor complex in lipid bilayers of living cells via stoichiometric association, rather than accumulation or unspecific clustering of complexes.
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Affiliation(s)
- Paola Soto
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo S Gaete
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christian Fuentes
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Benjamin Lozano
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pamela A Naulin
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Xavier F Figueroa
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nelson Patricio Barrera
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
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17
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Yoshida K, Tajima M, Nagano T, Obayashi K, Ito M, Yamamoto K, Matsuoka I. Co-Stimulation of Purinergic P2X4 and Prostanoid EP3 Receptors Triggers Synergistic Degranulation in Murine Mast Cells. Int J Mol Sci 2019; 20:E5157. [PMID: 31627451 PMCID: PMC6829402 DOI: 10.3390/ijms20205157] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 10/16/2019] [Accepted: 10/16/2019] [Indexed: 01/21/2023] Open
Abstract
Mast cells (MCs) recognize antigens (Ag) via IgE-bound high affinity IgE receptors (FcεRI) and trigger type I allergic reactions. FcεRI-mediated MC activation is regulated by various G protein-coupled receptor (GPCR) agonists. We recently reported that ionotropic P2X4 receptor (P2X4R) stimulation enhanced FcεRI-mediated degranulation. Since MCs are involved in Ag-independent hypersensitivity, we investigated whether co-stimulation with ATP and GPCR agonists in the absence of Ag affects MC degranulation. Prostaglandin E2 (PGE2) induced synergistic degranulation when bone marrow-derived MCs (BMMCs) were co-stimulated with ATP, while pharmacological analyses revealed that the effects of PGE2 and ATP were mediated by EP3 and P2X4R, respectively. Consistently, this response was absent in BMMCs prepared from P2X4R-deficient mice. The effects of ATP and PGE2 were reduced by PI3 kinase inhibitors but were insensitive to tyrosine kinase inhibitors which suppressed the enhanced degranulation induced by Ag and ATP. MC-dependent PGE2-triggered vascular hyperpermeability was abrogated in a P2X4R-deficient mouse ear edema model. Collectively, our results suggest that P2X4R signaling enhances EP3R-mediated MC activation via a different mechanism to that involved in enhancing Ag-induced responses. Moreover, the cooperative effects of the common inflammatory mediators ATP and PGE2 on MCs may be involved in Ag-independent hypersensitivity in vivo.
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Affiliation(s)
- Kazuki Yoshida
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Makoto Tajima
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Tomoki Nagano
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Kosuke Obayashi
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Masaaki Ito
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
| | - Kimiko Yamamoto
- Department of Biomedical Engineering, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
| | - Isao Matsuoka
- Laboratory of Pharmacology, Faculty of Pharmacy, Takasaki University of Health and Welfare, Takasaki-shi, Gunma 370-0033, Japan.
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18
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McCarthy AE, Yoshioka C, Mansoor SE. Full-Length P2X 7 Structures Reveal How Palmitoylation Prevents Channel Desensitization. Cell 2019; 179:659-670.e13. [PMID: 31587896 DOI: 10.1016/j.cell.2019.09.017] [Citation(s) in RCA: 149] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 07/30/2019] [Accepted: 09/13/2019] [Indexed: 12/24/2022]
Abstract
P2X receptors are trimeric, non-selective cation channels activated by extracellular ATP. The P2X7 receptor subtype is a pharmacological target because of involvement in apoptotic, inflammatory, and tumor progression pathways. It is the most structurally and functionally distinct P2X subtype, containing a unique cytoplasmic domain critical for the receptor to initiate apoptosis and not undergo desensitization. However, lack of structural information about the cytoplasmic domain has hindered understanding of the molecular mechanisms underlying these processes. We report cryoelectron microscopy structures of full-length rat P2X7 receptor in apo and ATP-bound states. These structures reveal how one cytoplasmic element, the C-cys anchor, prevents desensitization by anchoring the pore-lining helix to the membrane with palmitoyl groups. They show a second cytoplasmic element with a unique fold, the cytoplasmic ballast, which unexpectedly contains a zinc ion complex and a guanosine nucleotide binding site. Our structures provide first insights into the architecture and function of a P2X receptor cytoplasmic domain.
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Affiliation(s)
- Alanna E McCarthy
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA; Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR 97201, USA
| | - Steven E Mansoor
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA; Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR 97239, USA.
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19
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Robinson CV, Rohacs T, Hansen SB. Tools for Understanding Nanoscale Lipid Regulation of Ion Channels. Trends Biochem Sci 2019; 44:795-806. [PMID: 31060927 PMCID: PMC6729126 DOI: 10.1016/j.tibs.2019.04.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/23/2019] [Accepted: 04/01/2019] [Indexed: 11/17/2022]
Abstract
Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in particular phosphatidylinositol 4,5-bisphosphate (PIP2), initially suggested they act as channel cofactors. However, recent technologies have established an emerging system of nanoscale signaling to ion channels based on lipid compartmentalization (clustering), direct lipid binding, and local lipid dynamics that allow cells to harness lipid heterogeneity to gate ion channels. The new tools to study lipid binding are set to transform our view of the membrane and answer important questions surrounding ion channel-delimited processes such as mechanosensation.
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Affiliation(s)
- Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Scott B Hansen
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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20
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Schmidt A, Alsop RJ, Rimal R, Lenzig P, Joussen S, Gervasi NN, Khondker A, Gründer S, Rheinstädter MC, Wiemuth D. Modulation of DEG/ENaCs by Amphiphiles Suggests Sensitivity to Membrane Alterations. Biophys J 2019; 114:1321-1335. [PMID: 29590590 DOI: 10.1016/j.bpj.2018.01.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 01/22/2018] [Accepted: 01/26/2018] [Indexed: 12/25/2022] Open
Abstract
The bile acid-sensitive ion channel is activated by amphiphilic substances such as bile acids or artificial detergents via membrane alterations; however, the mechanism of membrane sensitivity of the bile acid-sensitive ion channel is not known. It has also not been systematically investigated whether other members of the degenerin/epithelial Na+ channel (DEG/ENaC) gene family are affected by amphiphilic compounds. Here, we show that DEG/ENaCs ASIC1a, ASIC3, ENaC, and the purinergic receptor P2X2 are modulated by a large number of different, structurally unrelated amphiphilic substances, namely the detergents N-lauroylsarcosine, Triton X-100, and β-octylglucoside; the fenamate flufenamic acid; the antipsychotic drug chlorpromazine; the natural phenol resveratrol; the chili pepper compound capsaicin; the loop diuretic furosemide; and the antiarrythmic agent verapamil. We determined the modification of membrane properties using large-angle x-ray diffraction experiments on model lipid bilayers, revealing that the amphiphilic compounds are positioned in a characteristic fashion either in the lipid tail group region or in the lipid head group region, demonstrating that they perturbed the membrane structure. Collectively, our results show that DEG/ENaCs and structurally related P2X receptors are modulated by diverse amphiphilic molecules. Furthermore, they suggest alterations of membrane properties by amphiphilic compounds as a mechanism contributing to modulation.
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Affiliation(s)
- Axel Schmidt
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Rick J Alsop
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Rahul Rimal
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Sylvia Joussen
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Natalie N Gervasi
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Adree Khondker
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
| | - Stefan Gründer
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | | | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Aachen, Germany.
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21
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Peverini L, Beudez J, Dunning K, Chataigneau T, Grutter T. New Insights Into Permeation of Large Cations Through ATP-Gated P2X Receptors. Front Mol Neurosci 2018; 11:265. [PMID: 30108481 PMCID: PMC6080412 DOI: 10.3389/fnmol.2018.00265] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/13/2018] [Indexed: 11/28/2022] Open
Abstract
The permeability of large cations through the P2X pore has remained arguably the most controversial and complicated topic in P2X-related research, with the emergence of conflicting studies on the existence, mechanism and physiological relevance of a so-called “dilated” state. Due to the important role of several “dilating” P2X subtypes in numerous diseases, a clear and detailed understanding of this phenomenon represents a research priority. Recent advances, however, have challenged the existence of a progressive, ATP-induced pore dilation, by demonstrating that this phenomenon is an artifact of the method employed. Here, we discuss briefly the history of this controversial and enigmatic dilated state, from its initial discovery to its recent reconsideration. We will discuss the literature in which mechanistic pathways to a large cation-permeable state are proposed, as well as important advances in the methodology employed to study this elusive state. Considering recent literature, we will also open the discussion as to whether an intrinsically dilating P2X pore exists, as well as the physiological relevance of such a large cation-permeable pore and its potential use as therapeutic pathway.
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Affiliation(s)
- Laurie Peverini
- CNRS, CAMB UMR 7199, Équipe de Chimie et Neurobiologie Moléculaire, Université de Strasbourg, Strasbourg, France
| | - Juline Beudez
- CNRS, CAMB UMR 7199, Équipe de Chimie et Neurobiologie Moléculaire, Université de Strasbourg, Strasbourg, France
| | - Kate Dunning
- CNRS, CAMB UMR 7199, Équipe de Chimie et Neurobiologie Moléculaire, Université de Strasbourg, Strasbourg, France
| | - Thierry Chataigneau
- CNRS, CAMB UMR 7199, Équipe de Chimie et Neurobiologie Moléculaire, Université de Strasbourg, Strasbourg, France
| | - Thomas Grutter
- CNRS, CAMB UMR 7199, Équipe de Chimie et Neurobiologie Moléculaire, Université de Strasbourg, Strasbourg, France
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22
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Bernier L, Ase AR, Séguéla P. P2X receptor channels in chronic pain pathways. Br J Pharmacol 2018; 175:2219-2230. [PMID: 28728214 PMCID: PMC5980614 DOI: 10.1111/bph.13957] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 07/05/2017] [Accepted: 07/10/2017] [Indexed: 12/18/2022] Open
Abstract
Chronic pain is a highly prevalent debilitating condition for which treatment options remain limited for many patients. Ionotropic ATP signalling through excitatory and calcium-permeable P2X receptor channels is now rightfully considered as a critical player in pathological pain generation and maintenance; therefore, their selective targeting represents a therapeutic opportunity with promising yet untapped potential. Recent advances in the structural, functional and pharmacological characterization of rodent and human ATP-gated P2X receptor channels have shed brighter light on the role of specific subtypes in the pathophysiology of chronic inflammatory, neuropathic or cancer pain. Here, we will review the contribution of P2X3, P2X4 and P2X7 receptors to chronic pain and discuss the opportunities and challenges associated with the pharmacological manipulation of their function. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
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Affiliation(s)
- Louis‐Philippe Bernier
- Department of Psychiatry, Djavad Mowafaghian Centre for Brain HealthUniversity of British ColumbiaVancouverBCCanada
| | - Ariel R Ase
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on PainMcGill UniversityMontréalQCCanada
| | - Philippe Séguéla
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on PainMcGill UniversityMontréalQCCanada
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23
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Rokic MB, Castro P, Leiva-Salcedo E, Tomic M, Stojilkovic SS, Coddou C. Opposing Roles of Calcium and Intracellular ATP on Gating of the Purinergic P2X2 Receptor Channel. Int J Mol Sci 2018; 19:ijms19041161. [PMID: 29641486 PMCID: PMC5979340 DOI: 10.3390/ijms19041161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 03/30/2018] [Accepted: 04/03/2018] [Indexed: 11/16/2022] Open
Abstract
P2X2 receptors (P2X2R) exhibit a slow desensitization during the initial ATP application and a progressive, calcium-dependent increase in rates of desensitization during repetitive stimulation. This pattern is observed in whole-cell recordings from cells expressing recombinant and native P2X2R. However, desensitization is not observed in perforated-patched cells and in two-electrode voltage clamped oocytes. Addition of ATP, but not ATPγS or GTP, in the pipette solution also abolishes progressive desensitization, whereas intracellular injection of apyrase facilitates receptor desensitization. Experiments with injection of alkaline phosphatase or addition of staurosporine and ATP in the intracellular solution suggest a role for a phosphorylation-dephosphorylation in receptor desensitization. Mutation of residues that are potential phosphorylation sites identified a critical role of the S363 residue in the intracellular ATP action. These findings indicate that intracellular calcium and ATP have opposing effects on P2X2R gating: calcium allosterically facilitates receptor desensitization and ATP covalently prevents the action of calcium. Single cell measurements further revealed that intracellular calcium stays elevated after washout in P2X2R-expressing cells and the blockade of mitochondrial sodium/calcium exchanger lowers calcium concentrations during washout periods to basal levels, suggesting a role of mitochondria in this process. Therefore, the metabolic state of the cell can influence P2X2R gating.
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Affiliation(s)
- Milos B Rokic
- Section on Cellular Signaling, National Institutes of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
| | - Patricio Castro
- Departamento de Ciencias Biomédicas, Facultad de Medicina, Universidad Católica del Norte, Coquimbo 1781421, Chile.
- Laboratory of Developmental Physiology, Department of Physiology, Faculty of Biological Sciences, Universidad de Concepción, Concepción 4030000, Chile.
| | - Elias Leiva-Salcedo
- Section on Cellular Signaling, National Institutes of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago 9170022, Chile.
- Centro para el Desarrollo de Nanociencias y Nanotecnología (CEDENNA), Santiago 9170022, Chile.
| | - Melanija Tomic
- Section on Cellular Signaling, National Institutes of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
| | - Stanko S Stojilkovic
- Section on Cellular Signaling, National Institutes of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
| | - Claudio Coddou
- Section on Cellular Signaling, National Institutes of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
- Departamento de Ciencias Biomédicas, Facultad de Medicina, Universidad Católica del Norte, Coquimbo 1781421, Chile.
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24
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Phan TK, Lay FT, Hulett MD. Importance of phosphoinositide binding by human β-defensin 3 for Akt-dependent cytokine induction. Immunol Cell Biol 2017; 96:54-67. [PMID: 29359392 DOI: 10.1111/imcb.1017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 09/15/2017] [Accepted: 09/15/2017] [Indexed: 12/11/2022]
Abstract
Host defense peptides (HDPs) are well-characterized for their antimicrobial activities but also variously display potent immunomodulatory effects. Human β-defensin 3 (HBD-3) belongs to a well-known HDP family known as defensins and is able to induce leukocyte chemotactic recruitment, leukocyte activation/maturation, proinflammatory cytokine release, and co-stimulatory marker expression. HBD-3-stimulated cytokine induction is NF-κB-dependent and was initially suggested to act via G protein-coupled C-C chemokine receptor phospholipase C (PLC) and/or Toll-like receptor signaling. Subsequent pharmacological inhibition, however, revealed that NF-κB activation by HBD-3 is receptor-independent and instead involves the phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) pathway, the mechanism of which remains undetermined. Recently, we have shown that HBD-3 can enter mammalian cells and bind to inner membrane phosphoinositide 4,5-bisphosphate [PI(4,5)P2], an important second lipid messenger of PLC and PI3K-Akt pathways. In this study, we report that the interaction of HBD-3 with PI(4,5)P2 is important for PI3K-Akt-NF-κΒ-mediated induction of tumor necrosis factor and interleukin-6. These data provide insights into the mechanism of immunomodulation by HBD-3, and more generally, highlight the complex multifaceted signaling roles of HDPs in innate defense. Furthermore, it is suggested that the proposed mode of action may be conserved in other HDPs.
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Affiliation(s)
- Thanh Kha Phan
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Fung T Lay
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
| | - Mark D Hulett
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Australia
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25
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Murrell-Lagnado RD. Regulation of P2X Purinergic Receptor Signaling by Cholesterol. CURRENT TOPICS IN MEMBRANES 2017; 80:211-232. [PMID: 28863817 DOI: 10.1016/bs.ctm.2017.05.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
P2X receptors are cation-selective channels that are activated by the binding of extracellular ATP. They have a high permeability to Ca2+, Na+, and K+ and are expressed widely throughout the nervous, immune, cardiovascular, skeletal, gastrointestinal, respiratory, and endocrine systems. Seven mammalian subtypes of P2X receptor subunits have been identified, P2X1-7, and those that function as homotrimeric receptors (P2X1, 2, 3, 4, and 7) are targeted to lipid rafts, although they show limited resistance to solubilization by Triton X-100. Recent crystal structures of P2X3 and P2X4 receptors have provided considerable high-resolution information about the architecture of this family of receptors and yet the molecular details of how they are regulated by cholesterol are unknown. Currents mediated by the P2X1-4 receptors are either inhibited or relatively insensitive to cholesterol depletion, but there is no clear evidence to support the direct binding of cholesterol to these receptors. In contrast, the activity of the low-affinity, proinflammatory P2X7 receptor is potentiated by cholesterol depletion and regions within the proximal C-terminus play an important role in coupling changes in cholesterol to the gating of the pore. Based upon our understanding of the lipid signaling events that are triggered downstream of P2X7 receptor activation, a change in the levels of cholesterol may contribute to the sensitization of receptor currents and the dilation of the pore that occurs following prolonged, high-level stimulation. This chapter focuses on the regulation of P2X7 receptor signaling by cholesterol and our current understanding of the mechanisms that underlie this.
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Affiliation(s)
- Ruth D Murrell-Lagnado
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, United Kingdom.
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26
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Gilbert DF, Stebbing MJ, Kuenzel K, Murphy RM, Zacharewicz E, Buttgereit A, Stokes L, Adams DJ, Friedrich O. Store-Operated Ca 2+ Entry (SOCE) and Purinergic Receptor-Mediated Ca 2+ Homeostasis in Murine bv2 Microglia Cells: Early Cellular Responses to ATP-Mediated Microglia Activation. Front Mol Neurosci 2016; 9:111. [PMID: 27840602 PMCID: PMC5083710 DOI: 10.3389/fnmol.2016.00111] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 10/14/2016] [Indexed: 12/31/2022] Open
Abstract
Microglia activation is a neuroinflammatory response to parenchymal damage with release of intracellular metabolites, e.g., purines, and signaling molecules from damaged cells. Extracellular purines can elicit Ca2+-mediated microglia activation involving P2X/P2Y receptors with metabotropic (P2Y) and ionotropic (P2X) cell signaling in target cells. Such microglia activation results in increased phagocytic activity, activation of their inflammasome and release of cytokines to sustain neuroinflammatory (so-called M1/M2 polarization). ATP-induced activation of ionotropic P2X4 and P2X7 receptors differentially induces receptor-operated Ca2+ entry (ROCE). Although store-operated Ca2+ entry (SOCE) was identified to modulate ROCE in primary microglia, its existence and role in one of the most common murine microglia cell line, BV2, is unknown. To dissect SOCE from ROCE in BV2 cells, we applied high-resolution multiphoton Ca2+ imaging. After depleting internal Ca2+ stores, SOCE was clearly detectable. High ATP concentrations (1 mM) elicited sustained increases in intracellular [Ca2+]i whereas lower concentrations (≤100 μM) also induced Ca2+ oscillations. These differential responses were assigned to P2X7 and P2X4 activation, respectively. Pharmacologically inhibiting P2Y and P2X responses did not affect SOCE, and in fact, P2Y-responses were barely detectable in BV2 cells. STIM1S content was significantly upregulated by 1 mM ATP. As P2X-mediated Ca2+ oscillations were rare events in single cells, we implemented a high-content screening approach that allows to record Ca2+ signal patterns from a large number of individual cells at lower optical resolution. Using automated classifier analysis, several drugs (minocycline, U73122, U73343, wortmannin, LY294002, AZ10606120) were tested on their profile to act on Ca2+ oscillations (P2X4) and sustained [Ca2+]i increases. We demonstrate specific drug effects on purinergic Ca2+ pathways and provide new pharmacological insights into Ca2+ oscillations in BV2 cells. For example, minocycline inhibits both P2X7- and P2X4-mediated Ca2+-responses, and this may explain its anti-inflammatory action in neuroinflammatory disease. As a technical result, our novel automated bio-screening approach provides a biomedical engineering platform to allow high-content drug library screens to study neuro-inflammation in vitro.
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Affiliation(s)
- Daniel F Gilbert
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany
| | - Martin J Stebbing
- Health Innovations Research Institute, Royal Melbourne Institute of Technology University, Melbourne VIC, Australia
| | - Katharina Kuenzel
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany
| | - Robyn M Murphy
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne VIC, Australia
| | - Evelyn Zacharewicz
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne VIC, Australia
| | - Andreas Buttgereit
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-Nürnberg Erlangen, Germany
| | - Leanne Stokes
- Health Innovations Research Institute, Royal Melbourne Institute of Technology University, Melbourne VIC, Australia
| | - David J Adams
- Health Innovations Research Institute, Royal Melbourne Institute of Technology University, Melbourne VIC, Australia
| | - Oliver Friedrich
- Department of Chemical and Biological Engineering, Institute of Medical Biotechnology, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-Universität Erlangen-NürnbergErlangen, Germany; Health Innovations Research Institute, Royal Melbourne Institute of Technology University, MelbourneVIC, Australia
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27
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Inhibition of P2X Receptors Protects Human Monocytes against Damage by Leukotoxin from Aggregatibacter actinomycetemcomitans and α-Hemolysin from Escherichia coli. Infect Immun 2016; 84:3114-3130. [PMID: 27528275 DOI: 10.1128/iai.00674-16] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 08/05/2016] [Indexed: 01/14/2023] Open
Abstract
α-Hemolysin (HlyA) from Escherichia coli and leukotoxin A (LtxA) from Aggregatibacter actinomycetemcomitans are important virulence factors in ascending urinary tract infections and aggressive periodontitis, respectively. The extracellular signaling molecule ATP is released immediately after insertion of the toxins into plasma membranes and, via P2X receptors, is essential for the erythrocyte damage inflicted by these toxins. Moreover, ATP signaling is required for the ensuing recognition and phagocytosis of damaged erythrocytes by the monocytic cell line THP-1. Here, we investigate how these toxins affect THP-1 monocyte function. We demonstrate that both toxins trigger early ATP release and a following increase in the intracellular Ca2+ concentration ([Ca2+]i) in THP-1 monocytes. The HlyA- and LtxA-induced [Ca2+]i response is diminished by the P2 receptor antagonist in a pattern that fits the functional P2 receptor expression in these cells. Both toxins are capable of lysing THP-1 cells, with LtxA being more aggressive. Either desensitization or blockage of P2X1, P2X4, or P2X7 receptors markedly reduces toxin-induced cytolysis. This pattern is paralleled in freshly isolated human monocytes from healthy volunteers. Interestingly, only a minor fraction of the toxin-damaged THP-1 monocytes eventually lyse. P2X7 receptor inhibition generally prevents cell damage, except from a distinct cell shrinkage that prevails in response to the toxins. Moreover, we find that preexposure to HlyA preserves the capacity of THP-1 monocytes to phagocytose damaged erythrocytes and may induce readiness to discriminate between damaged and healthy erythrocytes. These findings suggest a new pharmacological target for protecting monocytes during exposure to pore-forming cytolysins during infection or injury.
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Abstract
Fluid shear stress is an important environmental cue that governs vascular physiology and pathology, but the molecular mechanisms that mediate endothelial responses to flow are only partially understood. Gating of ion channels by flow is one mechanism that may underlie many of the known responses. Here, we review the literature on endothelial ion channels whose activity is modulated by flow with an eye toward identifying important questions for future research.
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Affiliation(s)
- Kristin A Gerhold
- Department of Internal Medicine (Cardiology), Yale Cardiovascular Research Center, Yale University, New Haven, Connecticut; and
| | - Martin A Schwartz
- Department of Internal Medicine (Cardiology), Yale Cardiovascular Research Center, Yale University, New Haven, Connecticut; and Departments of Cell Biology and Biomedical Engineering, Yale University, New Haven, Connecticut
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Rohacs T. Phosphoinositide signaling in somatosensory neurons. Adv Biol Regul 2016; 61:2-16. [PMID: 26724974 PMCID: PMC4884561 DOI: 10.1016/j.jbior.2015.11.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 11/06/2015] [Accepted: 11/07/2015] [Indexed: 02/03/2023]
Abstract
Somatosensory neurons of the dorsal root ganglia (DRG) and trigeminal ganglia (TG) are responsible for detecting thermal and tactile stimuli. They are also the primary neurons mediating pain and itch. A large number of cell surface receptors in these neurons couple to phospholipase C (PLC) enzymes leading to the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and the generation of downstream signaling molecules. These neurons also express many different ion channels, several of which are regulated by phosphoinositides. This review will summarize the knowledge on phosphoinositide signaling in DRG neurons, with special focus on effects on sensory and other ion channels.
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Affiliation(s)
- Tibor Rohacs
- Rutgers, New Jersey Medical School, Newark, NJ, USA.
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30
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Structural Insights into Divalent Cation Modulations of ATP-Gated P2X Receptor Channels. Cell Rep 2016; 14:932-944. [PMID: 26804916 DOI: 10.1016/j.celrep.2015.12.087] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 11/03/2015] [Accepted: 12/18/2015] [Indexed: 02/03/2023] Open
Abstract
P2X receptors are trimeric ATP-gated cation channels involved in physiological processes ranging widely from neurotransmission to pain and taste signal transduction. The modulation of the channel gating, including that by divalent cations, contributes to these diverse physiological functions of P2X receptors. Here, we report the crystal structure of an invertebrate P2X receptor from the Gulf Coast tick Amblyomma maculatum in the presence of ATP and Zn(2+) ion, together with electrophysiological and computational analyses. The structure revealed two distinct metal binding sites, M1 and M2, in the extracellular region. The M1 site, located at the trimer interface, is responsible for Zn(2+) potentiation by facilitating the structural change of the extracellular domain for pore opening. In contrast, the M2 site, coupled with the ATP binding site, might contribute to regulation by Mg(2+). Overall, our work provides structural insights into the divalent cation modulations of P2X receptors.
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31
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Jacobson KA, Müller CE. Medicinal chemistry of adenosine, P2Y and P2X receptors. Neuropharmacology 2015; 104:31-49. [PMID: 26686393 DOI: 10.1016/j.neuropharm.2015.12.001] [Citation(s) in RCA: 184] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 11/30/2015] [Accepted: 12/01/2015] [Indexed: 12/13/2022]
Abstract
Pharmacological tool compounds are now available to define action at the adenosine (ARs), P2Y and P2X receptors. We present a selection of the most commonly used agents to study purines in the nervous system. Some of these compounds, including A1 and A3 AR agonists, P2Y1R and P2Y12R antagonists, and P2X3, P2X4 and P2X7 antagonists, are potentially of clinical use in treatment of disorders of the nervous system, such as chronic pain, neurodegeneration and brain injury. Agonists of the A2AAR and P2Y2R are already used clinically, P2Y12R antagonists are widely used antithrombotics and an antagonist of the A2AAR is approved in Japan for treating Parkinson's disease. The selectivity defined for some of the previously introduced compounds has been revised with updated pharmacological characterization, for example, various AR agonists and antagonists were deemed A1AR or A3AR selective based on human data, but species differences indicated a reduction in selectivity ratios in other species. Also, many of the P2R ligands still lack bioavailability due to charged groups or hydrolytic (either enzymatic or chemical) instability. X-ray crystallographic structures of AR and P2YRs have shifted the mode of ligand discovery to structure-based approaches rather than previous empirical approaches. The X-ray structures can be utilized either for in silico screening of chemically diverse libraries for the discovery of novel ligands or for enhancement of the properties of known ligands by chemical modification. Although X-ray structures of the zebrafish P2X4R have been reported, there is scant structural information about ligand recognition in these trimeric ion channels. In summary, there are definitive, selective agonists and antagonists for all of the ARs and some of the P2YRs; while the pharmacochemistry of P2XRs is still in nascent stages. The therapeutic potential of selectively modulating these receptors is continuing to gain interest in such fields as cancer, inflammation, pain, diabetes, ischemic protection and many other conditions. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Key Words
- 2-MeSADP, (PubChem CID: 121990)
- A-740003, (PubChem CID: 23232014)
- ATP
- Agonists
- Antagonists
- DPCPX, (PubChem CID: 1329)
- GPCR
- IB-MECA, (PubChem CID: 123683)
- Ion channel
- LUF6000, (PubChem CID: 11711282)
- MRS2500, (PubChem CID: 44448831)
- Nucleosides
- Nucleotides
- PPTN, (PubChem CID: 42611190)
- PSB-1114, (PubChem CID: 52952605)
- PSB-603, (PubChem CID: 44185871)
- SCH442416, (PubChem CID: 10668061)
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Affiliation(s)
- Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 20892, Bethesda, USA.
| | - Christa E Müller
- PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, Bonn, Germany
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32
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Habermacher C, Dunning K, Chataigneau T, Grutter T. Molecular structure and function of P2X receptors. Neuropharmacology 2015; 104:18-30. [PMID: 26231831 DOI: 10.1016/j.neuropharm.2015.07.032] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 07/23/2015] [Accepted: 07/26/2015] [Indexed: 12/22/2022]
Abstract
ATP-gated P2X receptors are trimeric ion channels selective to cations. Recent progress in the molecular biophysics of these channels enables a better understanding of their function. In particular, data obtained from biochemical, electrophysiogical and molecular engineering in the light of recent X-ray structures now allow delineation of the principles of ligand binding, channel opening and allosteric modulation. However, although a picture emerges as to how ATP triggers channel opening, there are a number of intriguing questions that remain to be answered, in particular how the pore itself opens in response to ATP and how the intracellular domain, for which structural information is limited, moves during activation. In this review, we provide a summary of functional studies in the context of the post-structure era, aiming to clarify our understanding of the way in which P2X receptors function in response to ATP binding, as well as the mechanism by which allosteric modulators are able to regulate receptor function. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Chloé Habermacher
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7199, Laboratoire de Conception et Application de Molécules Bioactives, Équipe de Chimie et Neurobiologie Moléculaire, F-67400, Illkirch, France; Université de Strasbourg, Faculté de Pharmacie, F-67400, Illkirch, France
| | - Kate Dunning
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7199, Laboratoire de Conception et Application de Molécules Bioactives, Équipe de Chimie et Neurobiologie Moléculaire, F-67400, Illkirch, France; Université de Strasbourg, Faculté de Pharmacie, F-67400, Illkirch, France
| | - Thierry Chataigneau
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7199, Laboratoire de Conception et Application de Molécules Bioactives, Équipe de Chimie et Neurobiologie Moléculaire, F-67400, Illkirch, France; Université de Strasbourg, Faculté de Pharmacie, F-67400, Illkirch, France
| | - Thomas Grutter
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7199, Laboratoire de Conception et Application de Molécules Bioactives, Équipe de Chimie et Neurobiologie Moléculaire, F-67400, Illkirch, France; Université de Strasbourg, Faculté de Pharmacie, F-67400, Illkirch, France.
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33
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Hille B, Dickson EJ, Kruse M, Vivas O, Suh BC. Phosphoinositides regulate ion channels. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1851:844-56. [PMID: 25241941 PMCID: PMC4364932 DOI: 10.1016/j.bbalip.2014.09.010] [Citation(s) in RCA: 462] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/09/2014] [Accepted: 09/10/2014] [Indexed: 11/29/2022]
Abstract
Phosphoinositides serve as signature motifs for different cellular membranes and often are required for the function of membrane proteins. Here, we summarize clear evidence supporting the concept that many ion channels are regulated by membrane phosphoinositides. We describe tools used to test their dependence on phosphoinositides, especially phosphatidylinositol 4,5-bisphosphate, and consider mechanisms and biological meanings of phosphoinositide regulation of ion channels. This lipid regulation can underlie changes of channel activity and electrical excitability in response to receptors. Since different intracellular membranes have different lipid compositions, the activity of ion channels still in transit towards their final destination membrane may be suppressed until they reach an optimal lipid environment. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Eamonn J Dickson
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Oscar Vivas
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195-7290, USA.
| | - Byung-Chang Suh
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Republic of Korea.
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King BF. Purinergic signalling in the enteric nervous system (An overview of current perspectives). Auton Neurosci 2015; 191:141-7. [PMID: 26049261 DOI: 10.1016/j.autneu.2015.05.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Purinergic Signalling in the Enteric Nervous System involves the regulated release of ATP (or a structurally-related nucleotide) which activates an extensive suite of membrane-inserted receptors (P2X and P2Y subtypes) on a variety of cell types in the gastrointestinal tract. P2X receptors are gated ion-channels permeable to sodium, potassium and calcium. They depolarise cells, act as a pathway for calcium influx to activate calcium-dependent processes and initiate gene transcription, interact at a molecular level as a form of self-regulation with lipids within the cell wall (e.g. PIP2) and cross-react with other membrane-inserted receptors to regulate their activity (e.g. nAChRs). P2Y receptors are metabotropic receptors that couple to G-proteins. They may release calcium ions from intracellular stores to activate calcium-dependent processes, but also may activate calcium-independent signalling pathways and influence gene transcription. Originally ATP was a candidate only for NANC neurotransmission, for inhibitory motoneurons supplying the muscularis externa of the gastrointestinal tract and bringing about the fast IJP. Purinergic signalling later included neuron-neuron signalling in the ENS, via the production of either fast or slow EPSPs. Later still, purinergic signalling included the neuro-epithelial synapse-for efferent signalling to epithelia cells participating in secretion and absorption, and afferent signalling for chemoreception and mechanoreception at the surface of the mucosa. Many aspects of purinergic signalling have since been addressed in a series of highly-focussed and authoritative reviews. In this overview however, the current focus is on key aspects of purinergic signalling where there remains uncertainty and ambiguity, with the view to stimulating further research in these areas.
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Affiliation(s)
- Brian F King
- University College London (UCL), Department of Neuroscience, Physiology and Pharmacology (NPP), Royal Free Campus, Rowland Hill Street, Hampstead, London NW3 2PF, United Kingdom.
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35
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Hansen SB. Lipid agonism: The PIP2 paradigm of ligand-gated ion channels. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1851:620-8. [PMID: 25633344 PMCID: PMC4540326 DOI: 10.1016/j.bbalip.2015.01.011] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/05/2015] [Accepted: 01/17/2015] [Indexed: 01/08/2023]
Abstract
The past decade, membrane signaling lipids emerged as major regulators of ion channel function. However, the molecular nature of lipid binding to ion channels remained poorly described due to a lack of structural information and assays to quantify and measure lipid binding in a membrane. How does a lipid-ligand bind to a membrane protein in the plasma membrane, and what does it mean for a lipid to activate or regulate an ion channel? How does lipid binding compare to activation by soluble neurotransmitter? And how does the cell control lipid agonism? This review focuses on lipids and their interactions with membrane proteins, in particular, ion channels. I discuss the intersection of membrane lipid biology and ion channel biophysics. A picture emerges of membrane lipids as bona fide agonists of ligand-gated ion channels. These freely diffusing signals reside in the plasma membrane, bind to the transmembrane domain of protein, and cause a conformational change that allosterically gates an ion channel. The system employs a catalog of diverse signaling lipids ultimately controlled by lipid enzymes and raft localization. I draw upon pharmacology, recent protein structure, and electrophysiological data to understand lipid regulation and define inward rectifying potassium channels (Kir) as a new class of PIP2 lipid-gated ion channels.
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Affiliation(s)
- Scott B Hansen
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter FL 33458, USA.
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36
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Navarrete LC, Barrera NP, Huidobro-Toro JP. Vas deferens neuro-effector junction: from kymographic tracings to structural biology principles. Auton Neurosci 2014; 185:8-28. [PMID: 24956963 DOI: 10.1016/j.autneu.2014.05.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 05/14/2014] [Accepted: 05/20/2014] [Indexed: 11/29/2022]
Abstract
The vas deferens is a simple bioassay widely used to study the physiology of sympathetic neurotransmission and the pharmacodynamics of adrenergic drugs. The role of ATP as a sympathetic co-transmitter has gained increasing attention and furthered our understanding of its role in sympathetic reflexes. In addition, new information has emerged on the mechanisms underlying the storage and release of ATP. Both noradrenaline and ATP concur to elicit the tissue smooth muscle contractions following sympathetic reflexes or electrical field stimulation of the sympathetic nerve terminals. ATP and adenosine (its metabolic byproduct) are powerful presynaptic regulators of co-transmitter actions. In addition, neuropeptide Y, the third member of the sympathetic triad, is an endogenous modulator. The peptide plus ATP and/or adenosine play a significant role as sympathetic modulators of transmitter's release. This review focuses on the physiological principles that govern sympathetic co-transmitter activity, with special interest in defining the motor role of ATP. In addition, we intended to review the recent structural biology findings related to the topology of the P2X1R based on the crystallized P2X4 receptor from Danio rerio, or the crystallized adenosine A2A receptor as a member of the G protein coupled family of receptors as prototype neuro modulators. This review also covers structural elements of ectonucleotidases, since some members are found in the vas deferens neuro-effector junction. The allosteric principles that apply to purinoceptors are also reviewed highlighting concepts derived from receptor theory at the light of the current available structural elements. Finally, we discuss clinical applications of these concepts.
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Affiliation(s)
- L Camilo Navarrete
- Laboratorio de Estructura de Proteínas de Membrana y Señalización, Núcleo Milenio de Biología Estructural, NuBEs, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Chile
| | - Nelson P Barrera
- Laboratorio de Estructura de Proteínas de Membrana y Señalización, Núcleo Milenio de Biología Estructural, NuBEs, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Chile
| | - J Pablo Huidobro-Toro
- Laboratorio de Nucleótidos, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Chile.
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Bourinet E, Altier C, Hildebrand ME, Trang T, Salter MW, Zamponi GW. Calcium-permeable ion channels in pain signaling. Physiol Rev 2014; 94:81-140. [PMID: 24382884 DOI: 10.1152/physrev.00023.2013] [Citation(s) in RCA: 208] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.
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38
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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: 153] [Impact Index Per Article: 15.3] [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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Bernier LP, Ase AR, Séguéla P. Post-translational regulation of P2X receptor channels: modulation by phospholipids. Front Cell Neurosci 2013; 7:226. [PMID: 24324400 PMCID: PMC3838964 DOI: 10.3389/fncel.2013.00226] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 11/04/2013] [Indexed: 01/14/2023] Open
Abstract
P2X receptor channels mediate fast excitatory signaling by ATP and play major roles in sensory transduction, neuro-immune communication and inflammatory response. P2X receptors constitute a gene family of calcium-permeable ATP-gated cation channels therefore the regulation of P2X signaling is critical for both membrane potential and intracellular calcium homeostasis. Phosphoinositides (PIPn) are anionic signaling phospholipids that act as functional regulators of many types of ion channels. Direct PIPn binding was demonstrated for several ligand- or voltage-gated ion channels, however no generic motif emerged to accurately predict lipid-protein binding sites. This review presents what is currently known about the modulation of the different P2X subtypes by phospholipids and about critical determinants underlying their sensitivity to PIPn levels in the plasma membrane. All functional mammalian P2X subtypes tested, with the notable exception of P2X5, have been shown to be positively modulated by PIPn, i.e., homomeric P2X1, P2X2, P2X3, P2X4, and P2X7, as well as heteromeric P2X1/5 and P2X2/3 receptors. Based on various results reported on the aforementioned subtypes including mutagenesis of the prototypical PIPn-sensitive P2X4 and PIPn-insensitive P2X5 receptor subtypes, an increasing amount of functional, biochemical and structural evidence converges on the modulatory role of a short polybasic domain located in the proximal C-terminus of P2X subunits. This linear motif, semi-conserved in the P2X family, seems necessary and sufficient for encoding direct modulation of ATP-gated channels by PIPn. Furthermore, the physiological impact of the regulation of ionotropic purinergic responses by phospholipids on pain pathways was recently revealed in the context of native crosstalks between phospholipase C (PLC)-linked metabotropic receptors and P2X receptor channels in dorsal root ganglion sensory neurons and microglia.
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Affiliation(s)
- Louis-Philippe Bernier
- Department of Psychiatry, Brain Research Centre, University of British Columbia Vancouver, BC, Canada
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Bernier LP, Ase AR, Boué-Grabot É, Séguéla P. Inhibition of P2X4 function by P2Y6 UDP receptors in microglia. Glia 2013; 61:2038-49. [PMID: 24123515 DOI: 10.1002/glia.22574] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 07/24/2013] [Accepted: 08/21/2013] [Indexed: 12/24/2022]
Abstract
ATP-gated P2X4 receptor channels expressed in spinal microglia actively participate in central sensitization, making their functional regulation a key process in chronic pain pathologies. P2Y6 metabotropic Gq -coupled receptors, also expressed in microglia, are involved in the initial response to nerve injury, triggering phagocytosis upon activation by UDP. It has been reported recently that expression of both P2X4 and P2Y6 is upregulated in activated microglia following nerve injury. We show here, in resting as well as LPS-activated primary microglia, that P2Y6 decreases P2X4-mediated calcium entry and inhibits the dilation of P2X4 channels into a large-conductance pore measured with a YO-PRO-1 uptake assay. Furthermore, P2Y6 activation modulates the ATP-dependent migration of microglia, a process likely involved in their shift from migratory to phagocytic phenotype. Reconstituting the P2X4-P2Y6 interaction in recombinant systems shows that P2Y6 activation decreases P2X4 current amplitude, activation and desensitization rates, and reduces P2X4 channel permeability to the large cation NMDG(+) . Phospholipase C-mediated hydrolysis of the phosphoinositide PI(4,5)P2 , a necessary cofactor for P2X4 channel function, underlies this inhibitory crosstalk. As extracellular levels of both ATP and UDP are increased in the spinal cord following nerve injury, the control of P2X4 activity by P2Y6 might play a critical role in regulating neuropathic pain-inducing microglial responses.
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Affiliation(s)
- Louis-Philippe Bernier
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Center for Research on Pain, McGill University, Montréal, Québec, H3A 2B4, Canada
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Chen KH, Lin CR, Cheng JT, Cheng JK, Liao WT, Yang CH. Altered mitochondrial ATP synthase expression in the rat dorsal root ganglion after sciatic nerve injury and analgesic effects of intrathecal ATP. Cell Mol Neurobiol 2013; 34:51-9. [PMID: 24048632 DOI: 10.1007/s10571-013-9986-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 09/06/2013] [Indexed: 11/29/2022]
Abstract
Mitochondrial ATP synthase has multiple interdependent biological functions in neurons. Among them, ATP generation and regulation are the most important. The present study investigated whether the expression of mitochondrial ATP synthase correlates with symptoms of neuropathic pain in adult rats after axotomy, and whether intrathecal ATP administration is therapeutic in these neuropathic rats. Male Sprague-Dawley rats received left sciatic nerve transection (axotomy) and were randomly designated to a control (sham-operated) group, a neuropathic pain group (axotomy), a neuropathic pain and intrathecal sterile saline group, and a neuropathic pain and intrathecal ATP group. The thermal and mechanical sensitivity tests were performed at 1, 3, 5, and 7 days after axotomy. Left L4-L5 dorsal root ganglions (DRGs) were harvested to assess mitochondrial ATP synthase by immunoblotting and immunohistochemistry. After nerve injury, the expression of mitochondrial ATP synthase was decreased in protein extracts and was found mainly in C-fiber and A-δ fiber neurons of the DRGs. The decreased expression of mitochondrial ATP synthase and its subcellular localization were related to thermal and mechanical hyperalgesia. Administration of intrathecal ATP significantly attenuated thermal and mechanical hypersensitivity throughout the experimental period, which suggests its potential role in the treatment of neuropathic pain.
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Affiliation(s)
- Kuan-Hung Chen
- Department of Anesthesiology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, No. 123 Dapi Rd., Niaosong District, Kaohsiung, 833, Taiwan (R.O.C.)
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Hattori M, Hibbs RE, Gouaux E. A fluorescence-detection size-exclusion chromatography-based thermostability assay for membrane protein precrystallization screening. Structure 2012; 20:1293-9. [PMID: 22884106 DOI: 10.1016/j.str.2012.06.009] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 06/07/2012] [Accepted: 06/13/2012] [Indexed: 10/28/2022]
Abstract
Optimization of membrane protein stability under different solution conditions is essential for obtaining crystals that diffract to high resolution. Traditional methods that evaluate protein stability require large amounts of material and are, therefore, ill suited for medium- to high-throughput screening of membrane proteins. Here we present a rapid and efficient fluorescence-detection size-exclusion chromatography-based thermostability assay (FSEC-TS). In this method, the target protein is fused to GFP. Heated protein samples, treated with a panel of additives, are then analyzed by FSEC. FSEC-TS allows one to evaluate the thermostability of nanogram-to-microgram amounts of the target protein under a variety of conditions without purification. We applied this method to the Danio rerio P2X4 receptor and Caenorhabditis elegans GluCl to screen ligands, ions, and lipids, including newly designed cholesterol derivatives. In the case of GluCl, the screening results were used to obtain crystals of the receptor in the presence of lipids.
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Affiliation(s)
- Motoyuki Hattori
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA
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Mo G, Peleshok JC, Cao CQ, Ribeiro-da-Silva A, Séguéla P. Control of P2X3 channel function by metabotropic P2Y2 utp receptors in primary sensory neurons. Mol Pharmacol 2012; 83:640-7. [PMID: 23249537 DOI: 10.1124/mol.112.082099] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Purinergic signaling contributes significantly to pain mechanisms, and the nociceptor-specific P2X3 ATP receptor channel is considered a target in pain therapeutics. Recent findings suggesting the coexpression of metabotropic P2Y receptors with P2X3 implies that ATP release triggers the activation of both ionotropic and metabotropic purinoceptors, with strong potential for functional interaction. Modulation of native P2X3 function by P2Y receptor activation was investigated in rat dorsal root ganglia (DRG) neurons using whole cell patch-clamp recordings. Application of the selective P2Y receptor agonist UTP decreased peak amplitudes of α,β-meATP-evoked homomeric P2X3-mediated currents, but had no effect on heteromeric P2X2/3-mediated currents. Treatment with phospholipase C inhibitor U73122 significantly reversed P2X3 current inhibition induced by UTP-sensitive P2Y receptor activation. We previously reported the modulation of P2X receptors by phospholipids in DRG neurons and injection of exogenous phosphatidylinositol-4,5-bisphosphate (PIP(2)) fully reverses UTP-mediated regulation of P2X3 channel activity. Pharmacological as well as functional screening of P2Y receptor subtypes indicates the predominant involvement of P2Y2 receptor in P2X3 inhibition, and immunolocalization confirms a significant cellular coexpression of P2X3 and P2Y2 in rat DRG neurons. In summary, the function of P2X3 ATP receptor can be inhibited by P2Y2-mediated depletion of PIP(2). We propose that expression of P2Y2 purinoceptor in nociceptive sensory neurons provides an homeostatic mechanism to prevent excessive ATP signaling through P2X3 receptor channels.
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Affiliation(s)
- Gary Mo
- Alan Edwards Research Centre on Pain, Montreal, Quebec, Canada
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Roberts JA, Bottrill AR, Mistry S, Evans RJ. Mass spectrometry analysis of human P2X1 receptors; insight into phosphorylation, modelling and conformational changes. J Neurochem 2012; 123:725-35. [PMID: 22971236 PMCID: PMC3532615 DOI: 10.1111/jnc.12012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 08/23/2012] [Accepted: 08/28/2012] [Indexed: 11/30/2022]
Abstract
Recombinant FlagHis6 tagged Human P2X1 receptors expressed in HEK293 cells were purified, digested with trypsin and analysed by mass spectroscopy (96% coverage following de-glycosylation and reduction). The receptor was basally phosphorylated at residues S387, S388 and T389 in the carboxyl terminus, a triple alanine mutant of these residues had a modest ∼ 25% increase in current amplitude and recovery from desensitization. Chemical modification showed that intracellular lysine residues close to the transmembrane domains and the membrane stabilization motif are accessible to the aqueous environment. The membrane-impermeant cross-linking reagent 3,3′-Dithiobis (sulfosuccinimidylpropionate) (DTSSP) reduced agonist binding and P2X1 receptor currents by > 90%, and modified lysine residues were identified by mass spectroscopy. Mutation to remove reactive lysine residues around the ATP-binding pocket had no effect on inhibtion of agonist evoked currents following DTSSP. However, agonist evoked currents were ∼ 10-fold higher than for wild type following DTSSP treatment for mutants K199R, K221R and K199R-K221R. These mutations remove reactive residues distant from the agonist binding pocket that are close enough to cross-link adjacent subunits. These results suggest that conformational change in the P2X1 receptor is required for co-ordination of ATP action.
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Affiliation(s)
- Jonathan A Roberts
- Department of Cell Physiology & Pharmacology, University of Leicester, Leicester, UK
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Phosphatidylinositol 4-Kinases and PI4P Metabolism in the Nervous System: Roles in Psychiatric and Neurological Diseases. Mol Neurobiol 2012; 47:361-72. [DOI: 10.1007/s12035-012-8358-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 09/27/2012] [Indexed: 01/18/2023]
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Bernier LP, Blais D, Boué-Grabot É, Séguéla P. A dual polybasic motif determines phosphoinositide binding and regulation in the P2X channel family. PLoS One 2012; 7:e40595. [PMID: 22792379 PMCID: PMC3394732 DOI: 10.1371/journal.pone.0040595] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 06/11/2012] [Indexed: 01/05/2023] Open
Abstract
Phosphoinositides modulate the function of several ion channels, including most ATP-gated P2X receptor channels in neurons and glia, but little is known about the underlying molecular mechanism. We identified a phosphoinositide-binding motif formed of two clusters of positively charged amino acids located on the P2X cytosolic C-terminal domain, proximal to the second transmembrane domain. For all known P2X subtypes, the specific arrangement of basic residues in these semi-conserved clusters determines their sensitivity to membrane phospholipids. Neutralization of these positive charges disrupts the functional properties of the prototypical phosphoinositide-binding P2X4 subtype, mimicking wortmannin-induced phosphoinositide depletion, whereas adding basic residues at homologous positions to the natively insensitive P2X5 subtype establishes de novo phosphoinositide-mediated regulation. Moreover, biochemical evidence of in vitro P2X subunit-phospholipid interaction and functional intracellular phosphoinositide-binding assays demonstrate that the dual polybasic cluster is necessary and sufficient for regulation of P2X signaling by phospholipids.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Binding Sites
- Binding, Competitive
- Cell Line
- Conserved Sequence
- Humans
- Molecular Sequence Data
- Mutation
- Oocytes/metabolism
- Phenotype
- Phosphatidylinositols/metabolism
- Protein Binding
- Protein Interaction Domains and Motifs
- Protein Subunits/chemistry
- Protein Subunits/metabolism
- Rats
- Receptors, Purinergic P2X/chemistry
- Receptors, Purinergic P2X/genetics
- Receptors, Purinergic P2X/metabolism
- Receptors, Purinergic P2X1/chemistry
- Receptors, Purinergic P2X1/metabolism
- Receptors, Purinergic P2X5/chemistry
- Receptors, Purinergic P2X5/metabolism
- Receptors, Purinergic P2X7/chemistry
- Receptors, Purinergic P2X7/metabolism
- Sequence Alignment
- Signal Transduction
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Affiliation(s)
- Louis-Philippe Bernier
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montréal, Québec, Canada
| | - Dominique Blais
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montréal, Québec, Canada
| | - Éric Boué-Grabot
- Institut des Maladies Neurodégénératives, Université Bordeaux Segalen, CNRS UMR 5293, Bordeaux, France
| | - Philippe Séguéla
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, Alan Edwards Centre for Research on Pain, McGill University, Montréal, Québec, Canada
- * E-mail:
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Brain-derived neurotrophic factor from microglia: a molecular substrate for neuropathic pain. ACTA ACUST UNITED AC 2012; 7:99-108. [PMID: 22613083 DOI: 10.1017/s1740925x12000087] [Citation(s) in RCA: 145] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
One of the most significant advances in pain research is the realization that neurons are not the only cell type involved in the etiology of chronic pain. This realization has caused a radical shift from the previous dogma that neuronal dysfunction alone accounts for pain pathologies to the current framework of thinking that takes into account all cell types within the central nervous system (CNS). This shift in thinking stems from growing evidence that glia can modulate the function and directly shape the cellular architecture of nociceptive networks in the CNS. Microglia, in particular, are increasingly recognized as active principal players that respond to changes in physiological homeostasis by extending their processes toward the site of neural damage, and by releasing specific factors that have profound consequences on neuronal function and that contribute to CNS pathologies caused by disease or injury. A key molecule that modulates microglia activity is ATP, an endogenous ligand of the P2 receptor family. Microglia expresses several P2 receptor subtypes, and of these the P2X4 receptor subtype has emerged as a core microglia-neuron signaling pathway: activation of this receptor drives the release of brain-derived neurotrophic factor (BDNF), a cellular substrate that causes disinhibition of pain-transmitting spinal lamina I neurons. Converging evidence points to BDNF from spinal microglia as being a critical microglia-neuron signaling molecule that gates aberrant nociceptive processing in the spinal cord. The present review highlights recent advances in our understanding of P2X4 receptor-mediated signaling and regulation of BDNF in microglia, as well as the implications for microglia-neuron interactions in the pathobiology of neuropathic pain.
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P2X4 purinoceptor signaling in chronic pain. Purinergic Signal 2012; 8:621-8. [PMID: 22528681 DOI: 10.1007/s11302-012-9306-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 02/14/2012] [Indexed: 01/19/2023] Open
Abstract
ATP, acting via P2 purinergic receptors, is a known mediator of inflammatory and neuropathic pain. There is increasing evidence that the ATP-gated P2X4 receptor (P2X4R) subtype is a locus through which activity of spinal microglia and peripheral macrophages instigate pain hypersensitivity caused by inflammation or by injury to a peripheral nerve. The present article highlights the recent advances in our understanding of microglia-neuron interactions in neuropathic pain by focusing on the signaling and regulation of the P2X4R. We will also develop a framework for understanding converging lines of evidence for involvement of P2X4Rs expressed on macrophages in peripheral inflammatory pain.
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New insights in the activity of voltage sensitive phosphatases. Cell Signal 2012; 24:1541-7. [PMID: 22481094 DOI: 10.1016/j.cellsig.2012.03.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/13/2012] [Accepted: 03/20/2012] [Indexed: 11/23/2022]
Abstract
The Ciona intestinalis voltage sensitive phosphatase (Ci-VSP) was the first proven enzyme to be under direct control of the membrane potential. Ci-VSP belongs to a family of proteins known as Protein Tyrosine Phosphatases (PTP), which are a group of enzymes that catalyze the removal of phosphate groups from phosphatidylinositides and phosphorylated tyrosine residues on proteins. What makes Ci-VSP and similar phosphatases unique is the presence of a Voltage Sensing Domain (VSD) in their N-terminus. The VSD of Ci-VSP shares high homology with those from voltage-gated channels and confers voltage sensitivity to these enzymes. The catalytic domain of Ci-VSP displays extraordinary structural and functional similarities to PTEN. This latter protein is encoded by the Phosphatase and Tensin homolog deleted from chromosome 10 gene, thus its name, and it is known as a tumor suppressor. The resemblance between these proteins has prompted the use of PTEN as a template for the study of Ci-VSP and produced a rapid advance in our understanding of the mechanism of activity of Ci-VSP. This review will be focused on discussing recent advances in the understanding of the activation mechanism for these molecules known as electrochemical coupling.
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