1
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Hulme J. COVID-19 and Diarylamidines: The Parasitic Connection. Int J Mol Sci 2023; 24:6583. [PMID: 37047556 PMCID: PMC10094973 DOI: 10.3390/ijms24076583] [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: 03/15/2023] [Revised: 03/28/2023] [Accepted: 03/30/2023] [Indexed: 04/05/2023] Open
Abstract
As emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants (Omicron) continue to outpace and negate combinatorial vaccines and monoclonal antibody therapies targeting the spike protein (S) receptor binding domain (RBD), the appetite for developing similar COVID-19 treatments has significantly diminished, with the attention of the scientific community switching to long COVID treatments. However, treatments that reduce the risk of "post-COVID-19 syndrome" and associated sequelae remain in their infancy, particularly as no established criteria for diagnosis currently exist. Thus, alternative therapies that reduce infection and prevent the broad range of symptoms associated with 'post-COVID-19 syndrome' require investigation. This review begins with an overview of the parasitic-diarylamidine connection, followed by the renin-angiotensin system (RAS) and associated angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSSR2) involved in SARS-CoV-2 infection. Subsequently, the ability of diarylamidines to inhibit S-protein binding and various membrane serine proteases associated with SARS-CoV-2 and parasitic infections are discussed. Finally, the roles of diarylamidines (primarily DIZE) in vaccine efficacy, epigenetics, and the potential amelioration of long COVID sequelae are highlighted.
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Affiliation(s)
- John Hulme
- Department of Bionano Technology, Gachon Bionano Research Institute, Gachon University, 1342 Sungnam-daero, Sujung-gu, Seongnam-si 461-701, Republic of Korea
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2
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The bile acid-sensitive ion channel (BASIC) mediates bile acid-dependent currents in bile duct epithelial cells. Pflugers Arch 2021; 473:1841-1850. [PMID: 34549327 PMCID: PMC8599227 DOI: 10.1007/s00424-021-02622-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 09/07/2021] [Accepted: 09/08/2021] [Indexed: 11/17/2022]
Abstract
The bile acid-sensitive ion channel (BASIC) is a member of the Deg/ENaC family of ion channels that is activated by bile acids. Despite the identification of cholangiocytes in the liver and unipolar brush cells in the cerebellum as sites of expression, the physiological function of BASIC in these cell types is not yet understood. Here we used a cholangiocyte cell line, normal rat cholangiocytes (NRCs), which expresses BASIC to study the role of the channel in epithelial transport using Ussing chamber experiments. Apical application of bile acids induced robust and transient increases in transepithelial currents that were carried by Na+ and partly blocked by the BASIC inhibitor diminazene. Genetic ablation of the BASIC gene in NRC using a CRISPR-cas9 approach resulted in a decrease of the bile acid-mediated response that matched the diminazene-sensitive current in NRC WT cells, suggesting that cholangiocytes respond to bile acids with a BASIC-mediated Na+ influx. Taken together, we have identified BASIC as a component of the cholangiocyte transport machinery, which might mediate a bile acid-dependent modification of the bile and thus control bile flux and composition.
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3
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Sun JF, Xu YJ, Kong XH, Su Y, Wang ZY. Fenamates inhibit human sodium channel Nav1.7 and Nav1.8. Neurosci Lett 2019; 696:67-73. [DOI: 10.1016/j.neulet.2018.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 11/06/2018] [Accepted: 12/04/2018] [Indexed: 11/27/2022]
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4
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Lenzig P, Wirtz M, Wiemuth D. Comparative electrophysiological analysis of the bile acid-sensitive ion channel (BASIC) from different species suggests similar physiological functions. Pflugers Arch 2018; 471:329-336. [PMID: 30353368 DOI: 10.1007/s00424-018-2223-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/11/2018] [Accepted: 10/12/2018] [Indexed: 12/29/2022]
Abstract
Despite the identification of cholangiocytes in the liver and unipolar brush cells in the cerebellum as sites of expression, the physiological function of the bile acid-sensitive ion channel (BASIC) remains unknown. Rat BASIC (rBASIC) and mouse BASIC (mBASIC) share 97% of their amino acid sequence but show strikingly different biophysical properties. rBASIC is inactive at rest while mBASIC is constitutively active, when expressed in Xenopus oocytes. This conundrum rendered the identification of the physiological function even more difficult. In this study, we investigated the electrophysiological and pharmacological properties of BASIC from rat, mouse, and human in Hek293 cells using the patch clamp technique. Surprisingly, in Hek293 cells, rBASIC and mBASIC showed almost completely identical properties. Both are blocked by extracellular Ca2+ and thus are inactive at rest; both are selective for Na+, show similar affinities for extracellular Ca2+, were inhibited by diminazene, and activated by various bile acids. This is in contrast to previous results derived from Xenopus oocytes as expression system and suggests that the cell type is important for shaping the biophysical properties of BASIC. Furthermore, we compared hBASIC with rBASIC and mBASIC and observed similar properties between these channels with one exception: the bile acid sensitivity profile of hBASIC is different from rBASIC and mBASIC; hBASIC is more sensitive to bile acids which are abundant in human bile but not in rodent bile. Taken together, these results suggest similar physiological roles for BASIC in different species.
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Affiliation(s)
- Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - Monika Wirtz
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany
| | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany.
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5
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Krauson AJ, Rooney JG, Carattino MD. Molecular basis of inhibition of acid sensing ion channel 1A by diminazene. PLoS One 2018; 13:e0196894. [PMID: 29782492 PMCID: PMC5962070 DOI: 10.1371/journal.pone.0196894] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/20/2018] [Indexed: 11/18/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are trimeric proton-gated cation permeable ion channels expressed primarily in neurons. Here we employed site-directed mutagenesis and electrophysiology to investigate the mechanism of inhibition of ASIC1a by diminazene. This compound inhibits mouse ASIC1a with a half-maximal inhibitory concentration (IC50) of 2.4 μM. At first, we examined whether neutralizing mutations of Glu79 and Glu416 alter diminazene block. These residues form a hexagonal array in the lower palm domain that was previously shown to contribute to pore opening in response to extracellular acidification. Significantly, single Gln substitutions at positions 79 and 416 in ASIC1a reduced diminazene apparent affinity by 6-7 fold. This result suggests that diminazene inhibits ASIC1a in part by limiting conformational rearrangement in the lower palm domain. Because diminazene is charged at physiological pHs, we assessed whether it inhibits ASIC1a by blocking the ion channel pore. Consistent with the notion that diminazene binds to a site within the membrane electric field, diminazene block showed a strong dependence with the membrane potential. Moreover, a Gly to Ala mutation at position 438, in the ion conduction pathway of ASIC1a, increased diminazene IC50 by one order of magnitude and eliminated the voltage dependence of block. Taken together, our results indicate that the inhibition of ASIC1a by diminazene involves both allosteric modulation and blocking of ion flow through the conduction pathway. Our findings provide a foundation for the development of more selective and potent ASIC pore blockers.
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Affiliation(s)
- Aram J Krauson
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - James G Rooney
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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6
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Schmidt A, Bauknecht P, Williams EA, Augustinowski K, Gründer S, Jékely G. Dual signaling of Wamide myoinhibitory peptides through a peptide‐gated channel and a GPCR in
Platynereis. FASEB J 2018; 32:5338-5349. [DOI: 10.1096/fj.201800274r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Axel Schmidt
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | | | | | - Katrin Augustinowski
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | - Stefan Gründer
- Institute of Physiology, Rheinisch‐Westfälische Technische Hochschule (RWTH) Aachen UniversityAachenGermany
| | - Gáspár Jékely
- Living Systems Institute, University of ExeterExeterUnited Kingdom
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7
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The degenerin region of the human bile acid-sensitive ion channel (BASIC) is involved in channel inhibition by calcium and activation by bile acids. Pflugers Arch 2018; 470:1087-1102. [PMID: 29589117 DOI: 10.1007/s00424-018-2142-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 02/12/2018] [Accepted: 03/13/2018] [Indexed: 12/22/2022]
Abstract
The bile acid-sensitive ion channel (BASIC) is a member of the ENaC/degenerin family of ion channels. It is activated by bile acids and inhibited by extracellular Ca2+. The aim of this study was to explore the molecular mechanisms mediating these effects. The modulation of BASIC function by extracellular Ca2+ and tauro-deoxycholic acid (t-DCA) was studied in Xenopus laevis oocytes heterologously expressing human BASIC using the two-electrode voltage-clamp and outside-out patch-clamp techniques. Substitution of aspartate D444 to alanine or cysteine in the degenerin region of BASIC, a region known to be critically involved in channel gating, resulted in a substantial reduction of BASIC Ca2+ sensitivity. Moreover, mutating D444 or the neighboring alanine (A443) to cysteine significantly reduced the t-DCA-mediated BASIC stimulation. A combined molecular docking/simulation approach demonstrated that t-DCA may temporarily form hydrogen bonds with several amino acid residues including D444 in the outer vestibule of the BASIC pore or in the inter-subunit space. By these interactions, t-DCA may stabilize the open state of the channel. Indeed, single-channel recordings provided evidence that t-DCA activates BASIC by stabilizing the open state of the channel, whereas extracellular Ca2+ inhibits BASIC by stabilizing its closed state. In conclusion, our results highlight the potential role of the degenerin region as a critical regulatory site involved in the functional interaction of Ca2+ and t-DCA with BASIC.
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8
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Lee JYP, Saez NJ, Cristofori-Armstrong B, Anangi R, King GF, Smith MT, Rash LD. Inhibition of acid-sensing ion channels by diminazene and APETx2 evoke partial and highly variable antihyperalgesia in a rat model of inflammatory pain. Br J Pharmacol 2018; 175:2204-2218. [PMID: 29134638 DOI: 10.1111/bph.14089] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 10/22/2017] [Accepted: 10/31/2017] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Acid-sensing ion channels (ASICs) are primary acid sensors in mammals, with the ASIC1b and ASIC3 subtypes being involved in peripheral nociception. The antiprotozoal drug diminazene is a moderately potent ASIC inhibitor, but its analgesic activity has not been assessed. EXPERIMENTAL APPROACH We determined the ASIC subtype selectivity of diminazene and the mechanism by which it inhibits ASICs using voltage-clamp electrophysiology of Xenopus oocytes expressing ASICs 1-3. Its peripheral analgesic activity was then assessed relative to APETx2, an ASIC3 inhibitor, and morphine, in a Freund's complete adjuvant (FCA)-induced rat model of inflammatory pain. KEY RESULTS Diminazene inhibited homomeric rat ASICs with IC50 values of ~200-800 nM, via an open channel and subtype-dependent mechanism. In rats with FCA-induced inflammatory pain in one hindpaw, diminazene and APETx2 evoked more potent peripheral antihyperalgesia than morphine, but the effect was partial for APETx2. APETx2 potentiated rat ASIC1b at concentrations 30-fold to 100-fold higher than the concentration inhibiting ASIC3, which may have implications for its use in in vivo experiments. CONCLUSIONS AND IMPLICATIONS Diminazene and APETx2 are moderately potent ASIC inhibitors, both inducing peripheral antihyperalgesia in a rat model of chronic inflammatory pain. APETx2 has a more complex ASIC pharmacology, which must be considered when it is used as a supposedly selective ASIC3 inhibitor in vivo. Our use of outbred rats revealed responders and non-responders when ASIC inhibition was used to alleviate inflammatory pain, which is aligned with the concept of number-needed-to-treat in human clinical studies. 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)
- Jia Yu Peppermint Lee
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia
| | - Natalie J Saez
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | | | - Raveendra Anangi
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Maree T Smith
- UQ Centre for Clinical Research, Faculty of Medicine, The University of Queensland, St Lucia, QLD, Australia.,School of Pharmacy, The University of Queensland, St Lucia, QLD, Australia
| | - Lachlan D Rash
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia.,School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia
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9
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Schmidt A, Rossetti G, Joussen S, Gründer S. Diminazene Is a Slow Pore Blocker of Acid-Sensing Ion Channel 1a (ASIC1a). Mol Pharmacol 2017; 92:665-675. [PMID: 29025967 DOI: 10.1124/mol.117.110064] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 10/10/2017] [Indexed: 01/01/2023] Open
Abstract
Acid-sensing ion channels (ASICs) are neuronal receptors for extracellular protons. They contribute to the excitatory postsynaptic current and to the detection of painful acidosis. Moreover, they are activated during peripheral inflammation and acidosis associated with various neuronal disorders, such as stroke and neuroinflammation, rendering them interesting drug targets. Diminazene aceturate is a small-molecule inhibitor of ASICs with a reported apparent affinity in the low micromolar range, making it an interesting lead compound. It was reported that diminazene accelerates desensitization of ASICs, which was, however, not explained mechanistically. Furthermore, a binding site in a groove of the extracellular domain was proposed but not experimentally verified. In this study, we revisited the mechanism of inhibition by diminazene and its binding site on ASIC1a, the ASIC subunit with the greatest importance in the central nervous system. We show that diminazene slowly blocks ASIC1a, leading to the apparent acceleration of desensitization and underestimating its potency; we show that diminazene indeed has a submicromolar potency at ASIC1a (IC50 0.3 μM). Moreover, we show that the inhibition is voltage-dependent and competes with that by amiloride, a pore blocker of ASICs. Finally, we identify by molecular docking a binding site in the ion pore that we confirm by site-directed mutagenesis. In summary, our results show that diminazene blocks ASIC1a by a slow open-channel block and suggest that diminazene is an interesting lead compound for high-affinity blockers of ASICs.
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Affiliation(s)
- Axel Schmidt
- Institute of Physiology (A.S., S.J., S.G.), and Department of Oncology, Hematology and Stem Cell Transplantation (G.R.), RWTH Aachen University, Aachen, Germany; and Computational Biomedicine - Institute for Advanced Simulation/Institute of Neuroscience and Medicine, and Jülich Supercomputing Centre, Jülich, Germany (G.R.)
| | - Giulia Rossetti
- Institute of Physiology (A.S., S.J., S.G.), and Department of Oncology, Hematology and Stem Cell Transplantation (G.R.), RWTH Aachen University, Aachen, Germany; and Computational Biomedicine - Institute for Advanced Simulation/Institute of Neuroscience and Medicine, and Jülich Supercomputing Centre, Jülich, Germany (G.R.)
| | - Sylvia Joussen
- Institute of Physiology (A.S., S.J., S.G.), and Department of Oncology, Hematology and Stem Cell Transplantation (G.R.), RWTH Aachen University, Aachen, Germany; and Computational Biomedicine - Institute for Advanced Simulation/Institute of Neuroscience and Medicine, and Jülich Supercomputing Centre, Jülich, Germany (G.R.)
| | - Stefan Gründer
- Institute of Physiology (A.S., S.J., S.G.), and Department of Oncology, Hematology and Stem Cell Transplantation (G.R.), RWTH Aachen University, Aachen, Germany; and Computational Biomedicine - Institute for Advanced Simulation/Institute of Neuroscience and Medicine, and Jülich Supercomputing Centre, Jülich, Germany (G.R.)
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10
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Schmidt A, Löhrer D, Alsop RJ, Lenzig P, Oslender-Bujotzek A, Wirtz M, Rheinstädter MC, Gründer S, Wiemuth D. A Cytosolic Amphiphilic α-Helix Controls the Activity of the Bile Acid-sensitive Ion Channel (BASIC). J Biol Chem 2016; 291:24551-24565. [PMID: 27679529 DOI: 10.1074/jbc.m116.756437] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 09/19/2016] [Indexed: 12/22/2022] Open
Abstract
The bile acid-sensitive ion channel (BASIC) is a member of the degenerin/epithelial Na+ channel (Deg/ENaC) family of ion channels. It is mainly found in bile duct epithelial cells, the intestinal tract, and the cerebellum and is activated by alterations of its membrane environment. Bile acids, one class of putative physiological activators, exert their effect by changing membrane properties, leading to an opening of the channel. The physiological function of BASIC, however, is unknown. Deg/ENaC channels are characterized by a trimeric subunit composition. Each subunit is composed of two transmembrane segments, which are linked by a large extracellular domain. The termini of the channels protrude into the cytosol. Many Deg/ENaC channels contain regulatory domains and sequence motifs within their cytosolic domains. In this study, we show that BASIC contains an amphiphilic α-helical structure within its N-terminal domain. This α-helix binds to the cytosolic face of the plasma membrane and stabilizes a closed state. Truncation of this domain renders the channel hyperactive. Collectively, we identify a cytoplasmic domain, unique to BASIC, that controls channel activity via membrane interaction.
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Affiliation(s)
- Axel Schmidt
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and
| | - Daniel Löhrer
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and
| | - Richard J Alsop
- the Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Pia Lenzig
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and
| | | | - Monika Wirtz
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and
| | - Maikel C Rheinstädter
- the Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Stefan Gründer
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and
| | - Dominik Wiemuth
- From the Institute of Physiology, RWTH Aachen University, D-52074 Aachen, Germany and.
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11
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Chen D, Xing G, Yao J, Zhou H. Construction of highly functionalized naphthalenes using an in situ ene–allene strategy. RSC Adv 2016. [DOI: 10.1039/c6ra21889j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Construction of highly functionalized naphthalene derivatives remains a challenging task for organic chemists because of the effect of the substituent.
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Affiliation(s)
- Dianpeng Chen
- College of Biological
- Chemical Sciences and Engineering
- Jiaxing University
- Jiaxing 314001
- People's Republic of China
| | - Gangdong Xing
- Department of Chemistry
- Zhejiang University (Campus Xixi)
- Hangzhou 310028
- People's Republic of China
| | - Jinzhong Yao
- College of Biological
- Chemical Sciences and Engineering
- Jiaxing University
- Jiaxing 314001
- People's Republic of China
| | - Hongwei Zhou
- College of Biological
- Chemical Sciences and Engineering
- Jiaxing University
- Jiaxing 314001
- People's Republic of China
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12
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Hendriks CMM, Penning TM, Zang T, Wiemuth D, Gründer S, Sanhueza IA, Schoenebeck F, Bolm C. Pentafluorosulfanyl-containing flufenamic acid analogs: Syntheses, properties and biological activities. Bioorg Med Chem Lett 2015; 25:4437-40. [PMID: 26372652 PMCID: PMC4599580 DOI: 10.1016/j.bmcl.2015.09.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Revised: 09/04/2015] [Accepted: 09/06/2015] [Indexed: 01/15/2023]
Abstract
Pentafluorosulfanyl-containing analogs of flufenamic acid have been synthesized in high yields. Computationally, pKa, LogP and LogD values have been determined. Initial bioactivity studies reveal effects as ion channel modulators and inhibitory activities on aldo-keto reductase 1C3 (AKR1C3) as well as COX-1 and COX-2.
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Affiliation(s)
- Christine M M Hendriks
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
| | - Trevor M Penning
- Center of Excellence in Environmental Toxicology, Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, 1315 BRBII/III, 421 Curie Blvd, Philadelphia, PA 19104-6160, United States
| | - Tianzhu Zang
- Center of Excellence in Environmental Toxicology, Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, 1315 BRBII/III, 421 Curie Blvd, Philadelphia, PA 19104-6160, United States
| | - Dominik Wiemuth
- Institute of Physiology, Universitätsklinikum Aachen, RWTH Aachen University, Pauwelsstraße 30, D-52074 Aachen, Germany
| | - Stefan Gründer
- Institute of Physiology, Universitätsklinikum Aachen, RWTH Aachen University, Pauwelsstraße 30, D-52074 Aachen, Germany
| | - Italo A Sanhueza
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
| | - Franziska Schoenebeck
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
| | - Carsten Bolm
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
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13
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Schmidt A, Lenzig P, Oslender-Bujotzek A, Kusch J, Dias Lucas S, Gründer S, Wiemuth D. The bile acid-sensitive ion channel (BASIC) is activated by alterations of its membrane environment. PLoS One 2014; 9:e111549. [PMID: 25360526 PMCID: PMC4216111 DOI: 10.1371/journal.pone.0111549] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 10/06/2014] [Indexed: 01/26/2023] Open
Abstract
The bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC family of ion channels. Channels of this family are characterized by a common structure, their physiological functions and modes of activation, however, are diverse. Rat BASIC is expressed in brain, liver and intestinal tract and activated by bile acids. The physiological function of BASIC and its mechanism of bile acid activation remain a puzzle. Here we addressed the question whether amphiphilic bile acids activate BASIC by directly binding to the channel or indirectly by altering the properties of the surrounding membrane. We show that membrane-active substances other than bile acids also affect the activity of BASIC and that activation by bile acids and other membrane-active substances is non-additive, suggesting that BASIC is sensitive for changes in its membrane environment. Furthermore based on results from chimeras between BASIC and ASIC1a, we show that the extracellular and the transmembrane domains are important for membrane sensitivity.
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Affiliation(s)
- Axel Schmidt
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Pia Lenzig
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | | | - Jana Kusch
- Institute of Physiology II, University Hospital Jena, Friedrich-Schiller-University Jena, Jena, Germany
| | - Susana Dias Lucas
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Lisboa, Portugal
| | - Stefan Gründer
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Aachen, Germany
- * E-mail:
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14
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Assmann M, Kuhn A, Dürrnagel S, Holstein TW, Gründer S. The comprehensive analysis of DEG/ENaC subunits in Hydra reveals a large variety of peptide-gated channels, potentially involved in neuromuscular transmission. BMC Biol 2014; 12:84. [PMID: 25312679 PMCID: PMC4212090 DOI: 10.1186/s12915-014-0084-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 10/03/2014] [Indexed: 11/17/2022] Open
Abstract
Background It is generally the case that fast transmission at neural synapses is mediated by small molecule neurotransmitters. The simple nervous system of the cnidarian Hydra, however, contains a large repertoire of neuropeptides and it has been suggested that neuropeptides are the principal transmitters of Hydra. An ion channel directly gated by Hydra-RFamide neuropeptides has indeed been identified in Hydra – the Hydra Na+ channel (HyNaC) 2/3/5, which is expressed at the oral side of the tentacle base. Hydra-RFamides are more widely expressed, however, being found in neurons of the head and peduncle region. Here, we explore whether further peptide-gated HyNaCs exist, where in the animal they are expressed, and whether they are all gated by Hydra-RFamides. Results We report molecular cloning of seven new HyNaC subunits – HyNaC6 to HyNaC12, all of which are members of the DEG/ENaC gene family. In Xenopus oocytes, these subunits assemble together with the four already known subunits into thirteen different ion channels that are directly gated by Hydra-RFamide neuropeptides with high affinity (up to 40 nM). In situ hybridization suggests that HyNaCs are expressed in epitheliomuscular cells at the oral and the aboral side of the tentacle base and at the peduncle. Moreover, diminazene, an inhibitor of HyNaCs, delayed tentacle movement in live Hydra. Conclusions Our results show that Hydra has a large variety of peptide-gated ion channels that are activated by a restricted number of related neuropeptides. The existence and expression pattern of these channels, and behavioral effects induced by channel blockers, suggests that Hydra co-opted neuropeptides for fast neuromuscular transmission. Electronic supplementary material The online version of this article (doi:10.1186/s12915-014-0084-2) contains supplementary material, which is available to authorized users.
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Kellenberger S, Schild L. International Union of Basic and Clinical Pharmacology. XCI. Structure, Function, and Pharmacology of Acid-Sensing Ion Channels and the Epithelial Na+ Channel. Pharmacol Rev 2014; 67:1-35. [DOI: 10.1124/pr.114.009225] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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In silico determination of the effect of multi-target drugs on calcium dynamics signaling network underlying sea urchin spermatozoa motility. PLoS One 2014; 9:e104451. [PMID: 25162222 PMCID: PMC4146467 DOI: 10.1371/journal.pone.0104451] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2014] [Accepted: 07/08/2014] [Indexed: 11/19/2022] Open
Abstract
The motility of spermatozoa of both Lytechinus pictus and Strongylocentrotus purpuratus sea urchin species is modulated by the egg-derived decapeptide speract via an oscillatory [Ca2+]-dependent signaling pathway. Comprehension of this pathway is hence directly related to the understanding of regulated sperm swimming. Niflumic acid (NFA), a nonsteroidal anti-inflammatory drug alters several ion channels. Though unspecific, NFA profoundly affects how sea urchin sperm respond to speract, increasing the [Ca2+]i oscillation period, amplitude, peak and average level values of the responses in immobilized and swimming cells. A previous logical network model we developed for the [Ca2+] dynamics of speract signaling cascade in sea urchin sperm allows integrated dissection of individual and multiple actions of NFA. Among the channels affected by NFA are: hyperpolarization-activated and cyclic nucleotide gated Na+ channels (HCN), [Ca2+]-dependent Cl- channels (CaCC) and [Ca2+]-dependent K+ channels (CaKC), all present in the sea urchin genome. Here, using our model we investigated the effect of blocking in silico HCN and CaCC channels suggested by experiments. Regarding CaKC channels, arguments can be provided for either their blockage or activation by NFA. Our study yielded two scenarios compliant with experimental observations: i) under CaKC inhibition, this [Ca2+]-dependent K+ channel should be different from the Slo1 channel and ii) under activation of the CaKC channel, another [Ca2+] channel not considered previously in the network is required, such as the pH-dependent CatSper channel. Additionally, our findings predict cause-effect relations resulting from a selective inhibition of those channels. Knowledge of these relations may be of consequence for a variety of electrophysiological studies and have an impact on drug related investigations. Our study contributes to a better grasp of the network dynamics and suggests further experimental work.
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Huang TL, Mayence A, Vanden Eynde JJ. Some non-conventional biomolecular targets for diamidines. A short survey. Bioorg Med Chem 2014; 22:1983-92. [DOI: 10.1016/j.bmc.2014.02.049] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/19/2014] [Accepted: 02/24/2014] [Indexed: 12/24/2022]
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Wiemuth D, Assmann M, Gründer S. The bile acid-sensitive ion channel (BASIC), the ignored cousin of ASICs and ENaC. Channels (Austin) 2013; 8:29-34. [PMID: 24365967 DOI: 10.4161/chan.27493] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The DEG/ENaC gene family of ion channels is characterized by a high degree of structural similarity and an equally high degree of diversity concerning the physiological function. In humans and rodents, the DEG/ENaC family comprises 2 main subgroups: the subunits of the epithelial Na(+) channel (ENaC) and the subunits of the acid sensing ion channels (ASICs). The bile acid-sensitive channel (BASIC), previously known as BLINaC or INaC, represents a third subgroup within the DEG/ENaC family. Although BASIC was identified more than a decade ago, very little is known about its physiological function. Recent progress in the characterization of this neglected member of the DEG/ENaC family, which is summarized in this focused review, includes the discovery of surprising species differences, its pharmacological characterization, and the identification of bile acids as putative natural activators.
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Affiliation(s)
- Dominik Wiemuth
- Institute of Physiology; RWTH University Aachen; Aachen, Germany
| | - Marc Assmann
- Institute of Physiology; RWTH University Aachen; Aachen, Germany
| | - Stefan Gründer
- Institute of Physiology; RWTH University Aachen; Aachen, Germany
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Wiemuth D, Lefèvre CMT, Heidtmann H, Gründer S. Bile acids increase the activity of the epithelial Na+ channel. Pflugers Arch 2013; 466:1725-33. [PMID: 24292109 DOI: 10.1007/s00424-013-1403-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 10/29/2013] [Accepted: 11/07/2013] [Indexed: 01/08/2023]
Abstract
The epithelial Na(+) channel (ENaC) is a key regulator of Na(+) absorption in various epithelia including the distal nephron and the distal colon. ENaC is a constitutively active channel, but its activity is modulated by a number of mechanisms. These include proteolytic activation, ubiquitination and cell surface expression, phosphorylation, intracellular Na(+) concentration, and shear stress. ENaC is related to the bile acid-sensitive ion channel (BASIC), a channel that is expressed in the epithelial cells of bile ducts. BASIC is activated by millimolar concentrations of extracellular bile acids. Bile acids are synthesized by the liver and secreted into the duodenum to aid lipolysis. A large fraction of the secreted bile acids is absorbed by the ileum and recirculated into the liver, but a small fraction passes the colon and is excreted. Bile acids can influence the ion transport processes in the intestinal tract including the colon. In this study, we show that various bile acids present in rat bile potently and reversibly increase the activity of rat ENaC expressed in Xenopus oocytes, suggesting that bile acids are natural modulators of ENaC activity.
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Affiliation(s)
- Dominik Wiemuth
- Institute of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074, Aachen, Germany,
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20
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Denton JS, Pao AC, Maduke M. Novel diuretic targets. Am J Physiol Renal Physiol 2013; 305:F931-42. [PMID: 23863472 PMCID: PMC3798746 DOI: 10.1152/ajprenal.00230.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 07/12/2013] [Indexed: 01/11/2023] Open
Abstract
As the molecular revolution continues to inform a deeper understanding of disease mechanisms and pathways, there exist unprecedented opportunities for translating discoveries at the bench into novel therapies for improving human health. Despite the availability of several different classes of antihypertensive medications, only about half of the 67 million Americans with hypertension manage their blood pressure appropriately. A broader selection of structurally diverse antihypertensive drugs acting through different mechanisms would provide clinicians with greater flexibility in developing effective treatment regimens for an increasingly diverse and aging patient population. An emerging body of physiological, genetic, and pharmacological evidence has implicated several renal ion-transport proteins, or regulators thereof, as novel, yet clinically unexploited, diuretic targets. These include the renal outer medullary potassium channel, ROMK (Kir1.1), Kir4.1/5.1 potassium channels, ClC-Ka/b chloride channels, UTA/B urea transporters, the chloride/bicarbonate exchanger pendrin, and the STE20/SPS1-related proline/alanine-rich kinase (SPAK). The molecular pharmacology of these putative targets is poorly developed or lacking altogether; however, recent efforts by a few academic and pharmaceutical laboratories have begun to lessen this critical barrier. Here, we review the evidence in support of the aforementioned proteins as novel diuretic targets and highlight examples where progress toward developing small-molecule pharmacology has been made.
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Affiliation(s)
- Jerod S Denton
- T4208 Medical Center North, 1161 21st Ave. South, Nashville, TN 37232.
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21
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Pharmacological and electrophysiological characterization of the human bile acid-sensitive ion channel (hBASIC). Pflugers Arch 2013; 466:253-63. [PMID: 23842738 DOI: 10.1007/s00424-013-1310-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/07/2013] [Accepted: 06/10/2013] [Indexed: 01/23/2023]
Abstract
The human bile acid-sensitive ion channel (hBASIC) is a cation channel of the degenerin/epithelial Na(+) channel gene family that is expressed in the intestinal tract and can be activated by bile acids. Here, we show that in addition to its sensitivity for bile acids, hBASIC shares further key features with its rat ortholog: it is blocked by extracellular divalent cations, is inhibited by micromolar concentrations of the diarylamidine diminazene, and activated by millimolar concentrations of flufenamic acid. Furthermore, we demonstrate that two major bile acids present in human bile, chenodeoxycholic acid and deoxycholic acid, activate hBASIC in a synergistic manner. In addition, we determined the single-channel properties of hBASIC in outside-out patch clamp recordings, revealing a single-channel conductance of about 11 pS and a high Na(+) selectivity. Deoxycholic acid activates hBASIC in patch clamp recordings mainly by reducing the single-channel closed time. In summary, we provide a thorough functional characterization of hBASIC.
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22
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Boiko N, Kucher V, Eaton BA, Stockand JD. Inhibition of neuronal degenerin/epithelial Na+ channels by the multiple sclerosis drug 4-aminopyridine. J Biol Chem 2013; 288:9418-27. [PMID: 23404498 DOI: 10.1074/jbc.m112.449413] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The voltage-gated K(+) (Kv) channel blocker 4-aminopyridine (4-AP) is used to target symptoms of the neuroinflammatory disease multiple sclerosis (MS). By blocking Kv channels, 4-AP facilitates action potential conduction and neurotransmitter release in presynaptic neurons, lessening the effects of demyelination. Because they conduct inward Na(+) and Ca(2+) currents that contribute to axonal degeneration in response to inflammatory conditions, acid-sensing ion channels (ASICs) contribute to the pathology of MS. Consequently, ASICs are emerging as disease-modifying targets in MS. Surprisingly, as first demonstrated here, 4-AP inhibits neuronal degenerin/epithelial Na(+) (Deg/ENaC) channels, including ASIC and BLINaC. This effect is specific for 4-AP compared with its heterocyclic base, pyridine, and the related derivative, 4-methylpyridine; and akin to the actions of 4-AP on the structurally unrelated Kv channels, dose- and voltage-dependent. 4-AP has differential actions on distinct ASICs, strongly inhibiting ASIC1a channels expressed in central neurons but being without effect on ASIC3, which is enriched in peripheral sensory neurons. The voltage dependence of the 4-AP block and the single binding site for this inhibitor are consistent with 4-AP binding in the pore of Deg/ENaC channels as it does Kv channels, suggesting a similar mechanism of inhibition in these two classes of channels. These findings argue that effects on both Kv and Deg/ENaC channels should be considered when evaluating the actions of 4-AP. Importantly, the current results are consistent with 4-AP influencing the symptoms of MS as well as the course of the disease because of inhibitory actions on Kv and ASIC channels, respectively.
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Affiliation(s)
- Nina Boiko
- Department of Physiology, University of Texas Health Sciences Center, San Antonio, TX 78229, USA
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Guinamard R, Simard C, Del Negro C. Flufenamic acid as an ion channel modulator. Pharmacol Ther 2013; 138:272-84. [PMID: 23356979 DOI: 10.1016/j.pharmthera.2013.01.012] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 12/26/2012] [Indexed: 12/29/2022]
Abstract
Flufenamic acid has been known since the 1960s to have anti-inflammatory properties attributable to the reduction of prostaglandin synthesis. Thirty years later, flufenamic acid appeared to be an ion channel modulator. Thus, while its use in medicine diminished, its use in ionic channel research expanded. Flufenamic acid commonly not only affects non-selective cation channels and chloride channels, but also modulates potassium, calcium and sodium channels with effective concentrations ranging from 10(-6)M in TRPM4 channel inhibition to 10(-3)M in two-pore outwardly rectifying potassium channel activation. Because flufenamic acid effects develop and reverse rapidly, it is a convenient and widely used tool. However, given the broad spectrum of its targets, experimental results have to be interpreted cautiously. Here we provide an overview of ion channels targeted by flufenamic acid to aid in interpreting its effects at the molecular, cellular, and system levels. If it is used with good practices, flufenamic acid remains a useful tool for ion channel research. Understanding the targets of FFA may help reevaluate its physiological impacts and revive interest in its therapeutic potential.
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Wiemuth D, Sahin H, Lefèvre CMT, Wasmuth HE, Gründer S. Strong activation of bile acid-sensitive ion channel (BASIC) by ursodeoxycholic acid. Channels (Austin) 2012; 7:38-42. [PMID: 23064163 PMCID: PMC3589280 DOI: 10.4161/chan.22406] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Bile acid-sensitive ion channel (BASIC) is a member of the DEG/ENaC gene family of unknown function. Rat BASIC (rBASIC) is inactive at rest. We have recently shown that cholangiocytes, the epithelial cells lining the bile ducts, are the main site of BASIC expression in the liver and identified bile acids, in particular hyo- and chenodeoxycholic acid, as agonists of rBASIC. Moreover, it seems that extracellular divalent cations stabilize the resting state of rBASIC, because removal of extracellular divalent cations opens the channel. In this addendum, we demonstrate that removal of extracellular divalent cations potentiates the activation of rBASIC by bile acids, suggesting an allosteric mechanism. Furthermore, we show that rBASIC is strongly activated by the anticholestatic bile acid ursodeoxycholic acid (UDCA), suggesting that BASIC might mediate part of the therapeutic effects of UDCA.
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Affiliation(s)
- Dominik Wiemuth
- Department of Physiology, RWTH Aachen University, Aachen, Germany.
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25
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Garg P, Sanguinetti MC. Structure-activity relationship of fenamates as Slo2.1 channel activators. Mol Pharmacol 2012; 82:795-802. [PMID: 22851714 DOI: 10.1124/mol.112.079194] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Niflumic acid, 2-{[3-(trifluoromethyl)phenyl]amino}pyridine-3-carboxylic acid (NFA), a nonsteroidal anti-inflammatory drug that blocks cyclooxygenase (COX), was shown previously to activate [Na(+)](i)-regulated Slo2.1 channels. In this study, we report that other fenamates, including flufenamic acid, mefenamic acid, tolfenamic acid, meclofenamic acid, and a phenyl acetic acid derivative, diclofenac, also are low-potency (EC(50) = 80 μM to 2.1 mM), partial agonists of human Slo2.1 channels heterologously expressed in Xenopus oocytes. Substituent analysis determined that N-phenylanthranilic acid was the minimal pharmacophore for fenamate activation of Slo2.1 channels. The effects of fenamates were biphasic, with an initial rapid activation phase followed by a slow phase of current inhibition. Ibuprofen, a structurally dissimilar COX inhibitor, did not activate Slo2.1. Preincubation of oocytes with ibuprofen did not significantly alter the effects of NFA, suggesting that neither channel activation nor inhibition is associated with COX activity. A point mutation (A278R) in the pore-lining S6 segment of Slo2.1 increased the sensitivity to activation and reduced the inhibition induced by NFA. Together, our results suggest that fenamates bind to two sites on Slo2.1 channels: an extracellular accessible site to activate and a cytoplasmic accessible site in the pore to inhibit currents.
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Affiliation(s)
- Priyanka Garg
- Nora Eccles Harrison Cardiovascular Research and Training Institute, Department of Physiology, University of Utah, Salt Lake City, Utah 84112, USA
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Wiemuth D, Sahin H, Falkenburger BH, Lefèvre CMT, Wasmuth HE, Gründer S. BASIC--a bile acid-sensitive ion channel highly expressed in bile ducts. FASEB J 2012; 26:4122-30. [PMID: 22735174 DOI: 10.1096/fj.12-207043] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Brain liver intestine Na+ channel (BLINaC) is an ion channel of the DEG/ENaC gene family of unknown function. BLINaC from rats (rBLINaC) and humans (INaC) is inactive at rest, and its mode of activation has remained unclear. Here, we show that the BLINaC protein localizes to cholangiocytes, epithelial cells that line bile ducts. Moreover, we provide evidence that rBLINaC and INaC are robustly activated by bile acids, in particular chenodeoxycholic acid and hyodeoxycholic acid (EC50=2.1±0.05 mM). Thus, BLINaC appears to be an epithelial cation channel of bile ducts sensitive to physiological concentrations of bile acids. BLINaC is related to acid-sensing ion channels (ASICs) and to the epithelial Na+ channel (ENaC) and shares ligand activation with ASICs and epithelial localization with ENaC. Therefore, based on the close homology of BLINaC to ASICs and its activation by bile acids, we propose to rename BLINaC bile acid-sensitive ion channel (BASIC).
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Affiliation(s)
- Dominik Wiemuth
- Department of Physiology, RWTH Aachen University, Pauwelsstrasse 30, 52074 Aachen, Germany.
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