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Platonov M, Maximyuk O, Rayevsky A, Hurmach V, Iegorova O, Naumchyk V, Bulgakov E, Cherninskyi A, Ozheredov D, Ryabukhin SV, Krishtal O, Volochnyuk DM. 4-(Azolyl)-Benzamidines as a Novel Chemotype for ASIC1a Inhibitors. Int J Mol Sci 2024; 25:3584. [PMID: 38612396 PMCID: PMC11011685 DOI: 10.3390/ijms25073584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 03/03/2024] [Accepted: 03/13/2024] [Indexed: 04/14/2024] Open
Abstract
Acid-sensing ion channels (ASICs) play a key role in the perception and response to extracellular acidification changes. These proton-gated cation channels are critical for neuronal functions, like learning and memory, fear, mechanosensation and internal adjustments like synaptic plasticity. Moreover, they play a key role in neuronal degeneration, ischemic neuronal injury, seizure termination, pain-sensing, etc. Functional ASICs are homo or heterotrimers formed with (ASIC1-ASIC3) homologous subunits. ASIC1a, a major ASIC isoform in the central nervous system (CNS), possesses an acidic pocket in the extracellular region, which is a key regulator of channel gating. Growing data suggest that ASIC1a channels are a potential therapeutic target for treating a variety of neurological disorders, including stroke, epilepsy and pain. Many studies were aimed at identifying allosteric modulators of ASIC channels. However, the regulation of ASICs remains poorly understood. Using all available crystal structures, which correspond to different functional states of ASIC1, and a molecular dynamics simulation (MD) protocol, we analyzed the process of channel inactivation. Then we applied a molecular docking procedure to predict the protein conformation suitable for the amiloride binding. To confirm the effect of its sole active blocker against the ASIC1 state transition route we studied the complex with another MD simulation run. Further experiments evaluated various compounds in the Enamine library that emerge with a detectable ASIC inhibitory activity. We performed a detailed analysis of the structural basis of ASIC1a inhibition by amiloride, using a combination of in silico approaches to visualize its interaction with the ion pore in the open state. An artificial activation (otherwise, expansion of the central pore) causes a complex modification of the channel structure, namely its transmembrane domain. The output protein conformations were used as a set of docking models, suitable for a high-throughput virtual screening of the Enamine chemical library. The outcome of the virtual screening was confirmed by electrophysiological assays with the best results shown for three hit compounds.
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Affiliation(s)
- Maksym Platonov
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Zabolotnogo Str., 150, 03143 Kyiv, Ukraine; (M.P.); (V.H.)
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
| | - Oleksandr Maximyuk
- Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine; (O.M.); (O.I.); (A.C.); (O.K.)
| | - Alexey Rayevsky
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Zabolotnogo Str., 150, 03143 Kyiv, Ukraine; (M.P.); (V.H.)
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
- Institute of Food Biotechnology and Genomics, National Academy of Sciences of Ukraine, Osypovskoho Str., 2A, 04123 Kyiv, Ukraine;
| | - Vasyl Hurmach
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Zabolotnogo Str., 150, 03143 Kyiv, Ukraine; (M.P.); (V.H.)
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
| | - Olena Iegorova
- Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine; (O.M.); (O.I.); (A.C.); (O.K.)
| | - Vasyl Naumchyk
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
- Institute of High Technologies, Taras Shevchenko National University of Kyiv, Volodymyrska Street 60, 01601 Kyiv, Ukraine
| | - Elijah Bulgakov
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
- Institute of Food Biotechnology and Genomics, National Academy of Sciences of Ukraine, Osypovskoho Str., 2A, 04123 Kyiv, Ukraine;
| | - Andrii Cherninskyi
- Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine; (O.M.); (O.I.); (A.C.); (O.K.)
| | - Danil Ozheredov
- Institute of Food Biotechnology and Genomics, National Academy of Sciences of Ukraine, Osypovskoho Str., 2A, 04123 Kyiv, Ukraine;
| | - Serhiy V. Ryabukhin
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
- Institute of High Technologies, Taras Shevchenko National University of Kyiv, Volodymyrska Street 60, 01601 Kyiv, Ukraine
- Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Academik Kukhar Str., 02660 Kyiv, Ukraine
| | - Oleg Krishtal
- Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine; (O.M.); (O.I.); (A.C.); (O.K.)
| | - Dmytro M. Volochnyuk
- Enamine Ltd., 78 Winston Churchill Str., 02660 Kyiv, Ukraine; (V.N.); (E.B.); (D.M.V.)
- Institute of High Technologies, Taras Shevchenko National University of Kyiv, Volodymyrska Street 60, 01601 Kyiv, Ukraine
- Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Academik Kukhar Str., 02660 Kyiv, Ukraine
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Matasic DS, Holland N, Gautam M, Gibbons DD, Kusama N, Harding AMS, Shah VS, Snyder PM, Benson CJ. Paradoxical Potentiation of Acid-Sensing Ion Channel 3 (ASIC3) by Amiloride via Multiple Mechanisms and Sites Within the Channel. Front Physiol 2021; 12:750696. [PMID: 34721074 PMCID: PMC8555766 DOI: 10.3389/fphys.2021.750696] [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: 07/31/2021] [Accepted: 09/20/2021] [Indexed: 11/13/2022] Open
Abstract
Acid-Sensing Ion Channels (ASICs) are proton-gated sodium-selective cation channels that have emerged as metabolic and pain sensors in peripheral sensory neurons and contribute to neurotransmission in the CNS. These channels and their related degenerin/epithelial sodium channel (DEG/ENaC) family are often characterized by their sensitivity to amiloride inhibition. However, amiloride can also cause paradoxical potentiation of ASIC currents under certain conditions. Here we characterized and investigated the determinants of paradoxical potentiation by amiloride on ASIC3 channels. While inhibiting currents induced by acidic pH, amiloride potentiated sustained currents at neutral pH activation. These effects were accompanied by alterations in gating properties including (1) an alkaline shift of pH-dependent activation, (2) inhibition of pH-dependent steady-state desensitization (SSD), (3) prolongation of desensitization kinetics, and (4) speeding of recovery from desensitization. Interestingly, extracellular Ca2+ was required for paradoxical potentiation and it diminishes the amiloride-induced inhibition of SSD. Site-directed mutagenesis within the extracellular non-proton ligand-sensing domain (E79A, E423A) demonstrated that these residues were critical in mediating the amiloride-induced inhibition of SSD. However, disruption of the purported amiloride binding site (G445C) within the channel pore blunted both the inhibition and potentiation of amiloride. Together, our results suggest that the myriad of modulatory and blocking effects of amiloride are the result of a complex competitive interaction between amiloride, Ca2+, and protons at probably more than one site in the channel.
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Affiliation(s)
- Daniel S Matasic
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, United States
| | - Nicholas Holland
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA, United States
| | - Mamta Gautam
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
| | - David D Gibbons
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
| | - Nobuyoshi Kusama
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
| | - Anne M S Harding
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
| | - Viral S Shah
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, United States
| | - Peter M Snyder
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
| | - Christopher J Benson
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, IA, United States.,Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, IA, United States.,Iowa City VA Healthcare System, Iowa City, IA, United States
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3
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Ritter M, Bresgen N, Kerschbaum HH. From Pinocytosis to Methuosis-Fluid Consumption as a Risk Factor for Cell Death. Front Cell Dev Biol 2021; 9:651982. [PMID: 34249909 PMCID: PMC8261248 DOI: 10.3389/fcell.2021.651982] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 04/29/2021] [Indexed: 12/11/2022] Open
Abstract
The volumes of a cell [cell volume (CV)] and its organelles are adjusted by osmoregulatory processes. During pinocytosis, extracellular fluid volume equivalent to its CV is incorporated within an hour and membrane area equivalent to the cell's surface within 30 min. Since neither fluid uptake nor membrane consumption leads to swelling or shrinkage, cells must be equipped with potent volume regulatory mechanisms. Normally, cells respond to outwardly or inwardly directed osmotic gradients by a volume decrease and increase, respectively, i.e., they shrink or swell but then try to recover their CV. However, when a cell death (CD) pathway is triggered, CV persistently decreases in isotonic conditions in apoptosis and it increases in necrosis. One type of CD associated with cell swelling is due to a dysfunctional pinocytosis. Methuosis, a non-apoptotic CD phenotype, occurs when cells accumulate too much fluid by macropinocytosis. In contrast to functional pinocytosis, in methuosis, macropinosomes neither recycle nor fuse with lysosomes but with each other to form giant vacuoles, which finally cause rupture of the plasma membrane (PM). Understanding methuosis longs for the understanding of the ionic mechanisms of cell volume regulation (CVR) and vesicular volume regulation (VVR). In nascent macropinosomes, ion channels and transporters are derived from the PM. Along trafficking from the PM to the perinuclear area, the equipment of channels and transporters of the vesicle membrane changes by retrieval, addition, and recycling from and back to the PM, causing profound changes in vesicular ion concentrations, acidification, and-most importantly-shrinkage of the macropinosome, which is indispensable for its proper targeting and cargo processing. In this review, we discuss ion and water transport mechanisms with respect to CVR and VVR and with special emphasis on pinocytosis and methuosis. We describe various aspects of the complex mutual interplay between extracellular and intracellular ions and ion gradients, the PM and vesicular membrane, phosphoinositides, monomeric G proteins and their targets, as well as the submembranous cytoskeleton. Our aim is to highlight important cellular mechanisms, components, and processes that may lead to methuotic CD upon their derangement.
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Affiliation(s)
- Markus Ritter
- Center for Physiology, Pathophysiology and Biophysics, Institute for Physiology and Pathophysiology, Paracelsus Medical University, Salzburg, Austria
- Institute for Physiology and Pathophysiology, Paracelsus Medical University, Nuremberg, Germany
- Gastein Research Institute, Paracelsus Medical University, Salzburg, Austria
- Ludwig Boltzmann Institute for Arthritis und Rehabilitation, Salzburg, Austria
- Kathmandu University School of Medical Sciences, Dhulikhel, Nepal
| | - Nikolaus Bresgen
- Department of Biosciences, University of Salzburg, Salzburg, Austria
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4
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Flinck M, Kramer SH, Pedersen SF. Roles of pH in control of cell proliferation. Acta Physiol (Oxf) 2018; 223:e13068. [PMID: 29575508 DOI: 10.1111/apha.13068] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/17/2018] [Accepted: 03/19/2018] [Indexed: 02/06/2023]
Abstract
Precise spatiotemporal regulation of intracellular pH (pHi ) is a prerequisite for normal cell function, and changes in pHi or pericellular pH (pHe ) exert important signalling functions. It is well established that proliferation of mammalian cells is dependent on a permissive pHi in the slightly alkaline range (7.0-7.2). It is also clear that mitogen signalling in nominal absence of HCO3- is associated with an intracellular alkalinization (~0.3 pH unit above steady-state pHi ), which is secondary to activation of Na+ /H+ exchange. However, it remains controversial whether this increase in pHi is part of the mitogenic signal cascade leading to cell cycle entry and progression, and whether it is relevant under physiological conditions. Furthermore, essentially all studies of pHi in mammalian cell proliferation have focused on the mitogen-induced G0-G1 transition, and the regulation and roles of pHi during the cell cycle remain poorly understood. The aim of this review is to summarize and critically discuss the possible roles of pHi and pHe in cell cycle progression. While the focus is on the mammalian cell cycle, important insights from studies in lower eukaryotes are also discussed. We summarize current evidence of links between cell cycle progression and pHi and discuss possible pHi - and pHe sensors and signalling pathways relevant to mammalian proliferation control. The possibility that changes in pHi during cell cycle progression may be an integral part of the checkpoint control machinery is explored. Finally, we discuss the relevance of links between pH and proliferation in the context of the perturbed pH homoeostasis and acidic microenvironment of solid tumours.
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Affiliation(s)
- M. Flinck
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - S. H. Kramer
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
| | - S. F. Pedersen
- Section for Cell Biology and Physiology; Department of Biology; Faculty of Science; University of Copenhagen; Copenhagen Denmark
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5
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Elias SO, Sofola OA, Jaja SI. Epithelial sodium channel blockade and new β-ENaC polymorphisms among normotensive and hypertensive adult Nigerians. Clin Exp Hypertens 2018; 41:144-151. [PMID: 29580127 DOI: 10.1080/10641963.2018.1451538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We sought to determine the effect of amiloride on blood pressure (BP) and the presence of polymorphisms of the β-subunit of the epithelial sodium channel (ENaC) among normotensive (NT) and hypertensive (HT) Nigerians. Healthy volunteers-47 NT and 53 age-matched HT were recruited after giving informed consent. Subjects were salt-loaded with 200 mmol of NaCl daily for 5 days. Following a week washout period, salt-loading was repeated in addition to the administration of 5 mg amiloride daily for five days. Blood pressure, plasma and urine electrolytes were measured at baseline, after salt-loading and after salt-loading plus amiloride. PCR amplicons were sequenced for β-ENaC polymorphisms. Salt-loading led to a significant increase (p < 0.05) in SBP among NT and HT and in DBP (p < 0.001) only among HT. Amiloride reduced SBP and DBP to below baseline levels in NT (p < 0.05) and HT (p < 0.001) subjects. Five of the subjects had the β-T594M polymorphism, HT 3/53; NT 2/47 (p = 0.75). Four previously unreported β-ENaC mutations were recorded: E632V and E636V, respectively, among two HT subjects, D638Y in another HT and L628Q in one NT subject. We showed the presence of β-ENaC polymorphisms among our populace and the possible usefulness of amiloride as a single antihypertensive among Nigerians.
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Affiliation(s)
- Simiat O Elias
- Department of Physiology, Lagos State University College of Medicine, Lagos, Nigeria
| | - Olusoga A Sofola
- Department of Physiology, College of Medicine University of Lagos, Lagos, Nigeria
| | - Smith I Jaja
- Department of Physiology, College of Medicine University of Lagos, Lagos, Nigeria
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6
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Besson T, Lingueglia E, Salinas M. Pharmacological modulation of Acid-Sensing Ion Channels 1a and 3 by amiloride and 2-guanidine-4-methylquinazoline (GMQ). Neuropharmacology 2017; 125:429-440. [DOI: 10.1016/j.neuropharm.2017.08.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/27/2017] [Accepted: 08/07/2017] [Indexed: 11/28/2022]
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7
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Lynagh T, Romero-Rojo JL, Lund C, Pless SA. Molecular Basis for Allosteric Inhibition of Acid-Sensing Ion Channel 1a by Ibuprofen. J Med Chem 2017; 60:8192-8200. [PMID: 28949138 DOI: 10.1021/acs.jmedchem.7b01072] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A growing body of evidence links certain aspects of nonsteroidal anti-inflammatory drug (NSAID) pharmacology with acid-sensing ion channels (ASICs), a small family of excitatory neurotransmitter receptors implicated in pain and neuroinflammation. The molecular basis of NSAID inhibition of ASICs has remained unknown, hindering the exploration of this line of therapy. Here, we characterized the mechanism of inhibition, explored the molecular determinants of sensitivity, and sought to establish informative structure-activity relationships, using electrophysiology, site-directed mutagenesis, and voltage-clamp fluorometry. Our results show that ibuprofen is an allosteric inhibitor of ASIC1a, which binds to a crucial site in the agonist transduction pathway and causes conformational changes that oppose channel activation. Ibuprofen inhibits several ASIC subtypes, but certain ibuprofen derivatives show some selectivity for ASIC1a over ASIC2a and vice versa. These results thus define the NSAID/ASIC interaction and pave the way for small-molecule drug design targeting pain and inflammation.
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Affiliation(s)
- Timothy Lynagh
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
| | - José Luis Romero-Rojo
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
| | - Camilla Lund
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
| | - Stephan A Pless
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
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8
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Singh D, Silakari O. Sodium hydrogen exchanger inhibitory activity of benzotriazole derivatives. Eur J Med Chem 2017; 126:183-189. [DOI: 10.1016/j.ejmech.2016.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/01/2016] [Accepted: 10/03/2016] [Indexed: 12/14/2022]
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9
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Esteves S, Duarte-Silva S, Maciel P. Discovery of Therapeutic Approaches for Polyglutamine Diseases: A Summary of Recent Efforts. Med Res Rev 2016; 37:860-906. [PMID: 27870126 DOI: 10.1002/med.21425] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 10/01/2016] [Accepted: 10/05/2016] [Indexed: 12/19/2022]
Abstract
Polyglutamine (PolyQ) diseases are a group of neurodegenerative disorders caused by the expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats in the coding region of specific genes. This leads to the production of pathogenic proteins containing critically expanded tracts of glutamines. Although polyQ diseases are individually rare, the fact that these nine diseases are irreversibly progressive over 10 to 30 years, severely impairing and ultimately fatal, usually implicating the full-time patient support by a caregiver for long time periods, makes their economic and social impact quite significant. This has led several researchers worldwide to investigate the pathogenic mechanism(s) and therapeutic strategies for polyQ diseases. Although research in the field has grown notably in the last decades, we are still far from having an effective treatment to offer patients, and the decision of which compounds should be translated to the clinics may be very challenging. In this review, we provide a comprehensive and critical overview of the most recent drug discovery efforts in the field of polyQ diseases, including the most relevant findings emerging from two different types of approaches-hypothesis-based candidate molecule testing and hypothesis-free unbiased drug screenings. We hereby summarize and reflect on the preclinical studies as well as all the clinical trials performed to date, aiming to provide a useful framework for increasingly successful future drug discovery and development efforts.
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Affiliation(s)
- Sofia Esteves
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal.,ICVS/3B's PT Government Associate Laboratory, University of Minho, Guimarães, Braga, Portugal
| | - Sara Duarte-Silva
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal.,ICVS/3B's PT Government Associate Laboratory, University of Minho, Guimarães, Braga, Portugal
| | - Patrícia Maciel
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal.,ICVS/3B's PT Government Associate Laboratory, University of Minho, Guimarães, Braga, Portugal
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10
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Matthewman C, Miller-Fleming TW, Miller DM, Bianchi L. Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels. Am J Physiol Cell Physiol 2016; 311:C920-C930. [PMID: 27760755 DOI: 10.1152/ajpcell.00247.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/12/2016] [Indexed: 12/22/2022]
Abstract
Hyperactivated DEG/ENaC channels cause neuronal death mediated by intracellular Ca2+ overload. Mammalian ASIC1a channels and MEC-4(d) neurotoxic channels in Caenorhabditis elegans both conduct Na+ and Ca2+, raising the possibility that direct Ca2+ influx through these channels contributes to intracellular Ca2+ overload. However, we showed that the homologous C. elegans DEG/ENaC channel UNC-8(d) is not Ca2+ permeable, yet it is neurotoxic, suggesting that Na+ influx is sufficient to induce cell death. Interestingly, UNC-8(d) shows small currents due to extracellular Ca2+ block in the Xenopus oocyte expression system. Thus, MEC-4(d) and UNC-8(d) differ both in current amplitude and Ca2+ permeability. Given that these two channels show a striking difference in toxicity, we wondered how Na+ conductance vs. Ca2+ permeability contributes to cell death. To address this question, we built an UNC-8/MEC-4 chimeric channel that retains the calcium permeability of MEC-4 and characterized its properties in Xenopus oocytes. Our data support the hypothesis that for Ca2+-permeable DEG/ENaC channels, both Ca2+ permeability and Na+ conductance contribute to toxicity. However, for Ca2+-impermeable DEG/ENaCs (e.g., UNC-8), our evidence shows that constitutive Na+ conductance is sufficient to induce toxicity, and that this effect is enhanced as current amplitude increases. Our work further refines the contribution of different channel properties to cellular toxicity induced by hyperactive DEG/ENaC channels.
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Affiliation(s)
- Cristina Matthewman
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida.,Neuroscience Program, University of Miami, Miller School of Medicine, Miami, Florida
| | | | - David M Miller
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee; and.,Neuroscience Program, Vanderbilt University, Nashville, Tennessee
| | - Laura Bianchi
- Department of Physiology and Biophysics, University of Miami, Miller School of Medicine, Miami, Florida; .,Neuroscience Program, University of Miami, Miller School of Medicine, Miami, Florida
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11
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Nagaeva EI, Potapieva NN, Nikolaev MV, Gmiro VE, Magazanik LG, Tikhonov DB. Determinants of action of hydrophobic amines on ASIC1a and ASIC2a. Eur J Pharmacol 2016; 788:75-83. [DOI: 10.1016/j.ejphar.2016.06.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 06/03/2016] [Accepted: 06/08/2016] [Indexed: 11/16/2022]
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12
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α-Dendrotoxin inhibits the ASIC current in dorsal root ganglion neurons from rat. Neurosci Lett 2015; 606:42-7. [PMID: 26314509 DOI: 10.1016/j.neulet.2015.08.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/11/2015] [Accepted: 08/19/2015] [Indexed: 11/23/2022]
Abstract
Dendrotoxins are a group of peptide toxins purified from the venom of several mamba snakes. α-Dendrotoxin (α-DTx, from the Eastern green mamba Dendroaspis angusticeps) is a well-known blocker of voltage-gated K(+) channels and specifically of K(v)1.1, K(v)1.2 and K(v)1.6. In this work we show that α-DTx inhibited the ASIC currents in DRG neurons (IC50=0.8 μM) when continuously perfused during 25 s (including a 5 s pulse to pH 6.1), but not when co-applied with the pH drop. Additionally, we show that α-DTx abolished a transient component of the outward current that, in some experiments, appeared immediately after the end of the acid pulse. Our data indicate that α-DTx inhibits ASICs in the high nM range while some Kv are inhibited in the low nM range. The α-DTx selectivity and its potential interaction with ASICs should be taken in consideration when DTx is used in the high nM range.
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13
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Rodríguez AA, Salceda E, Garateix AG, Zaharenko AJ, Peigneur S, López O, Pons T, Richardson M, Díaz M, Hernández Y, Ständker L, Tytgat J, Soto E. A novel sea anemone peptide that inhibits acid-sensing ion channels. Peptides 2014; 53:3-12. [PMID: 23764262 DOI: 10.1016/j.peptides.2013.06.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 06/01/2013] [Accepted: 06/03/2013] [Indexed: 12/19/2022]
Abstract
Sea anemones produce ion channels peptide toxins of pharmacological and biomedical interest. However, peptides acting on ligand-gated ion channels, including acid-sensing ion channel (ASIC) toxins, remain poorly explored. PhcrTx1 is the first compound characterized from the sea anemone Phymanthus crucifer, and it constitutes a novel ASIC inhibitor. This peptide was purified by gel filtration, ion-exchange and reversed-phase chromatography followed by biological evaluation on ion channels of isolated rat dorsal root ganglia (DRG) neurons using patch clamp techniques. PhcrTx1 partially inhibited ASIC currents (IC50∼100 nM), and also voltage-gated K(+) currents but the effects on the peak and on the steady state currents were lower than 20% in DRG neurons, at concentrations in the micromolar range. No significant effect was observed on Na(+) voltage-gated currents in DRG neurons. The N-terminal sequencing yielded 32 amino acid residues, with a molecular mass of 3477 Da by mass spectrometry. No sequence identity to other sea anemone peptides was found. Interestingly, the bioinformatic analysis of Cys-pattern and secondary structure arrangement suggested that this peptide presents an Inhibitor Cystine Knot (ICK) scaffold, which has been found in other venomous organisms such as spider, scorpions and cone snails. Our results show that PhcrTx1 represents the first member of a new structural group of sea anemones toxins acting on ASIC and, with much lower potency, on Kv channels. Moreover, this is the first report of an ICK peptide in cnidarians, suggesting that the occurrence of this motif in venomous animals is more ancient than expected.
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Affiliation(s)
| | - Emilio Salceda
- Instituto de Fisiología, Universidad Autónoma de Puebla, 14 sur 6301, CU, San Manuel, Puebla, Puebla CP 72750, Mexico.
| | | | | | - Steve Peigneur
- Laboratory of Toxicology, University of Leuven (KU Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium.
| | - Omar López
- Instituto de Fisiología, Universidad Autónoma de Puebla, 14 sur 6301, CU, San Manuel, Puebla, Puebla CP 72750, Mexico.
| | - Tirso Pons
- Centro Nacional de Investigaciones Oncológicas (CNIO), C/ Melchor Fernández Almagro 3, 28029 Madrid, Spain.
| | - Michael Richardson
- Fundação Ezequiel Dias-FUNED, Rua Conde Pereira Carneiro 80, CEP 30510-010 Belo Horizonte, MG, Brazil.
| | - Maylín Díaz
- Centro de Bioproductos Marinos (CEBIMAR), Loma y 37, Alturas del Vedado, CP 10400 Habana, Cuba.
| | - Yasnay Hernández
- Centro de Bioproductos Marinos (CEBIMAR), Loma y 37, Alturas del Vedado, CP 10400 Habana, Cuba.
| | - Ludger Ständker
- Kompetenzzentrum Ulm Peptide Pharmaceuticals (U-PEP), Universität Ulm (West), Albert-Einstein Allee 47, 89081 Ulm, Germany.
| | - Jan Tytgat
- Laboratory of Toxicology, University of Leuven (KU Leuven), Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium.
| | - Enrique Soto
- Instituto de Fisiología, Universidad Autónoma de Puebla, 14 sur 6301, CU, San Manuel, Puebla, Puebla CP 72750, Mexico.
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14
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Baconguis I, Bohlen CJ, Goehring A, Julius D, Gouaux E. X-ray structure of acid-sensing ion channel 1-snake toxin complex reveals open state of a Na(+)-selective channel. Cell 2014; 156:717-29. [PMID: 24507937 DOI: 10.1016/j.cell.2014.01.011] [Citation(s) in RCA: 221] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 11/20/2013] [Accepted: 01/07/2014] [Indexed: 12/25/2022]
Abstract
Acid-sensing ion channels (ASICs) detect extracellular protons produced during inflammation or ischemic injury and belong to the superfamily of degenerin/epithelial sodium channels. Here, we determine the cocrystal structure of chicken ASIC1a with MitTx, a pain-inducing toxin from the Texas coral snake, to define the structure of the open state of ASIC1a. In the MitTx-bound open state and in the previously determined low-pH desensitized state, TM2 is a discontinuous α helix in which the Gly-Ala-Ser selectivity filter adopts an extended, belt-like conformation, swapping the cytoplasmic one-third of TM2 with an adjacent subunit. Gly 443 residues of the selectivity filter provide a ring of three carbonyl oxygen atoms with a radius of ∼3.6 Å, presenting an energetic barrier for hydrated ions. The ASIC1a-MitTx complex illuminates the mechanism of MitTx action, defines the structure of the selectivity filter of voltage-independent, sodium-selective ion channels, and captures the open state of an ASIC.
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Affiliation(s)
- Isabelle Baconguis
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Christopher J Bohlen
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - April Goehring
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - David Julius
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Eric Gouaux
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA; Howard Hughes Medical Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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15
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Hendus-Altenburger R, Kragelund BB, Pedersen SF. Structural dynamics and regulation of the mammalian SLC9A family of Na⁺/H⁺ exchangers. CURRENT TOPICS IN MEMBRANES 2014; 73:69-148. [PMID: 24745981 DOI: 10.1016/b978-0-12-800223-0.00002-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mammalian Na⁺/H⁺ exchangers of the SLC9A family are widely expressed and involved in numerous essential physiological processes. Their primary function is to mediate the 1:1 exchange of Na⁺ for H⁺ across the membrane in which they reside, and they play central roles in regulation of body, cellular, and organellar pH. Their function is tightly regulated through mechanisms involving interactions with multiple protein and lipid-binding partners, phosphorylations, and other posttranslational modifications. Biochemical and mutational analyses indicate that the SLC9As have a short intracellular N-terminus, 12 transmembrane (TM) helices necessary and sufficient for ion transport, and a C-terminal cytoplasmic tail region with essential regulatory roles. No high-resolution structures of the SLC9As exist; however, models based on crystal structures of the bacterial NhaAs support the 12 TM organization and suggest that TMIV and XI may form a central part of the ion-translocation pathway, whereas pH sensing may involve TMII, TMIX, and several intracellular loops. Similar to most ion transporters studied, SLC9As likely exist as coupled dimers in the membrane, and this appears to be important for the well-studied cooperativity of H⁺ binding. The aim of this work is to summarize and critically discuss the currently available evidence on the structural dynamics, regulation, and binding partner interactions of SLC9As, focusing in particular on the most widely studied isoform, SLC9A1/NHE1. Further, novel bioinformatic and structural analyses are provided that to some extent challenge the existing paradigm on how ions are transported by mammalian SLC9As.
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Affiliation(s)
- Ruth Hendus-Altenburger
- Section for Biomolecular Sciences, Department of Biology, University of Copenhagen, Copenhagen, Denmark; Section for Cell and Developmental Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Birthe B Kragelund
- Section for Biomolecular Sciences, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Stine Falsig Pedersen
- Section for Cell and Developmental Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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16
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Abstract
Why do neurons sense extracellular acid? In large part, this question has driven increasing investigation on acid-sensing ion channels (ASICs) in the CNS and the peripheral nervous system for the past two decades. Significant progress has been made in understanding the structure and function of ASICs at the molecular level. Studies aimed at clarifying their physiological importance have suggested roles for ASICs in pain, neurological and psychiatric disease. This Review highlights recent findings linking these channels to physiology and disease. In addition, it discusses some of the implications for therapy and points out questions that remain unanswered.
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17
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Gordon D, Chen R, Chung SH. Computational methods of studying the binding of toxins from venomous animals to biological ion channels: theory and applications. Physiol Rev 2013; 93:767-802. [PMID: 23589832 PMCID: PMC3768100 DOI: 10.1152/physrev.00035.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The discovery of new drugs that selectively block or modulate ion channels has great potential to provide new treatments for a host of conditions. One promising avenue revolves around modifying or mimicking certain naturally occurring ion channel modulator toxins. This strategy appears to offer the prospect of designing drugs that are both potent and specific. The use of computational modeling is crucial to this endeavor, as it has the potential to provide lower cost alternatives for exploring the effects of new compounds on ion channels. In addition, computational modeling can provide structural information and theoretical understanding that is not easily derivable from experimental results. In this review, we look at the theory and computational methods that are applicable to the study of ion channel modulators. The first section provides an introduction to various theoretical concepts, including force-fields and the statistical mechanics of binding. We then look at various computational techniques available to the researcher, including molecular dynamics, brownian dynamics, and molecular docking systems. The latter section of the review explores applications of these techniques, concentrating on pore blocker and gating modifier toxins of potassium and sodium channels. After first discussing the structural features of these channels, and their modes of block, we provide an in-depth review of past computational work that has been carried out. Finally, we discuss prospects for future developments in the field.
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Affiliation(s)
- Dan Gordon
- Research School of Biology, The Australian National University, Acton, ACT 0200, Australia.
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18
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Guardiani C, Procacci P. The conformational landscape of tartrate-based inhibitors of the TACE enzyme as revealed by Hamiltonian Replica Exchange simulation. Phys Chem Chem Phys 2013; 15:9186-96. [DOI: 10.1039/c3cp00108c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Eastwood AL, Goodman MB. Insight into DEG/ENaC channel gating from genetics and structure. Physiology (Bethesda) 2012; 27:282-90. [PMID: 23026751 PMCID: PMC4012085 DOI: 10.1152/physiol.00006.2012] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The founding members of the superfamily of DEG/ENaC ion channel proteins are C. elegans proteins that form mechanosensitive channels in touch and pain receptors. For more than a decade, the research community has used mutagenesis to identify motifs that regulate gating. This review integrates insight derived from unbiased in vivo mutagenesis screens with recent crystal structures to develop new models for activation of mechanically gated DEGs.
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Affiliation(s)
- Amy L. Eastwood
- Dept of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305-5345,
| | - Miriam B. Goodman
- Dept of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305-5345,
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20
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Bhattacharya P, Pandey AK, Paul S, Patnaik R. Neuroprotective potential of Piroxicam in cerebral ischemia: An in silico evaluation of the hypothesis to explore its therapeutic efficacy by inhibition of aquaporin-4 and acid sensing ion channel1a. Med Hypotheses 2012; 79:352-7. [DOI: 10.1016/j.mehy.2012.05.033] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 05/02/2012] [Accepted: 05/21/2012] [Indexed: 11/17/2022]
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21
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Sherwood TW, Frey EN, Askwith CC. Structure and activity of the acid-sensing ion channels. Am J Physiol Cell Physiol 2012; 303:C699-710. [PMID: 22843794 DOI: 10.1152/ajpcell.00188.2012] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The acid-sensing ion channels (ASICs) are a family of proton-sensing channels expressed throughout the nervous system. Their activity is linked to a variety of complex behaviors including fear, anxiety, pain, depression, learning, and memory. ASICs have also been implicated in neuronal degeneration accompanying ischemia and multiple sclerosis. As a whole, ASICs represent novel therapeutic targets for several clinically important disorders. An understanding of the correlation between ASIC structure and function will help to elucidate their mechanism of action and identify potential therapeutics that specifically target these ion channels. Despite the seemingly simple nature of proton binding, multiple studies have shown that proton-dependent gating of ASICs is quite complex, leading to activation and desensitization through distinct structural components. This review will focus on the structural aspects of ASIC gating in response to both protons and the newly discovered activators GMQ and MitTx. ASIC modulatory compounds and their action on proton-dependent gating will also be discussed. This review is dedicated to the memory of Dale Benos, who made a substantial contribution to our understanding of ASIC activity.
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Affiliation(s)
- Thomas W Sherwood
- Dept. of Neuroscience, The Ohio State Univ. Wexner Medical Center, Columbus, OH 43210, USA
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22
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Balderas E, Ateaga-Tlecuitl R, Rivera M, Gomora JC, Darszon A. Niflumic acid blocks native and recombinant T-type channels. J Cell Physiol 2012; 227:2542-55. [PMID: 21898399 DOI: 10.1002/jcp.22992] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Voltage-dependent calcium channels are widely distributed in animal cells, including spermatozoa. Calcium is fundamental in many sperm functions such as: motility, capacitation, and the acrosome reaction (AR), all essential for fertilization. Pharmacological evidence has suggested T-type calcium channels participate in the AR. Niflumic acid (NA), a non-steroidal anti-inflammatory drug commonly used as chloride channel blocker, blocks T-currents in mouse spermatogenic cells and Cl(-) channels in testicular sperm. Here we examine the mechanism of NA blockade and explore if it can be used to separate the contribution of different Ca(V)3 members previously detected in these cells. Electrophysiological patch-clamp recordings were performed in isolated mouse spermatogenic cells and in HEK cells heterologously expressing Ca(V)3 channels. NA blocks mouse spermatogenic cell T-type currents with an IC(50) of 73.5 µM, without major voltage-dependent effects. The NA blockade is more potent in the open and in the inactivated state than in the closed state of the T-type channels. Interestingly, we found that heterologously expressed Ca(V)3.1 and Ca(V)3.3 channels were more sensitive to NA than Ca(V)3.2 channels, and this drug substantially slowed the recovery from inactivation of the three isoforms. Molecular docking modeling of drug-channel binding predicts that NA binds preferentially to the extracellular face of Ca(V)3.1 channels. The biophysical characteristics of mouse spermatogenic cell T-type currents more closely resemble those from heterologously expressed Ca(V)3.1 channels, including their sensitivity to NA. As Ca(V)3.1 null mice maintain their spermatogenic cell T-currents, it is likely that a novel Ca(V)3.2 isoform is responsible for them.
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Affiliation(s)
- Enrique Balderas
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Avenida Universidad 2001, Col. Chamilpa, Cuernavaca Mor., Mexico
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23
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Fernández-Ballester G, Fernández-Carvajal A, González-Ros JM, Ferrer-Montiel A. Ionic channels as targets for drug design: a review on computational methods. Pharmaceutics 2011; 3:932-53. [PMID: 24309315 PMCID: PMC3857065 DOI: 10.3390/pharmaceutics3040932] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2011] [Revised: 10/26/2011] [Accepted: 11/30/2011] [Indexed: 01/21/2023] Open
Abstract
Ion channels are involved in a broad range of physiological and pathological processes. The implications of ion channels in a variety of diseases, including diabetes, epilepsy, hypertension, cancer and even chronic pain, have signaled them as pivotal drug targets. Thus far, drugs targeting ion channels were developed without detailed knowledge of the molecular interactions between the lead compounds and the target channels. In recent years, however, the emergence of high-resolution structures for a plethora of ion channels paves the way for computer-assisted drug design. Currently, available functional and structural data provide an attractive platform to generate models that combine substrate-based and protein-based approaches. In silico approaches include homology modeling, quantitative structure-activity relationships, virtual ligand screening, similarity and pharmacophore searching, data mining, and data analysis tools. These strategies have been frequently used in the discovery and optimization of novel molecules with enhanced affinity and specificity for the selected therapeutic targets. In this review we summarize recent applications of in silico methods that are being used for the development of ion channel drugs.
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24
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Li WG, Yu Y, Huang C, Cao H, Xu TL. Nonproton ligand sensing domain is required for paradoxical stimulation of acid-sensing ion channel 3 (ASIC3) channels by amiloride. J Biol Chem 2011; 286:42635-42646. [PMID: 21998313 DOI: 10.1074/jbc.m111.289058] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Acid-sensing ion channels (ASICs), which belong to the epithelial sodium channel/degenerin family, are activated by extracellular protons and are inhibited by amiloride (AMI), an important pharmacological tool for studying all known members of epithelial sodium channel/degenerin. In this study, we reported that AMI paradoxically opened homomeric ASIC3 and heteromeric ASIC3 plus ASIC1b channels at neutral pH and synergistically enhanced channel activation induced by mild acidosis (pH 7.2 to 6.8). The characteristic profile of AMI stimulation of ASIC3 channels was reminiscent of the channel activation by the newly identified nonproton ligand, 2-guanidine-4-methylquinazoline. Using site-directed mutagenesis, we showed that ASIC3 activation by AMI, but not its inhibitory effect, was dependent on the integrity of the nonproton ligand sensing domain in ASIC3 channels. Moreover, the structure-activity relationship study demonstrated the differential requirement of the 5-amino group in AMI for the stimulation or inhibition effect, strengthening the different interactions within ASIC3 channels that confer the paradoxical actions of AMI. Furthermore, using covalent modification analyses, we provided strong evidence supporting the nonproton ligand sensing domain is required for the stimulation of ASIC3 channels by AMI. Finally, we showed that AMI causes pain-related behaviors in an ASIC3-dependent manner. These data reinforce the idea that ASICs can sense nonproton ligands in addition to protons. The results also indicate caution in the use of AMI for studying ASIC physiology and in the development of AMI-derived ASIC inhibitors for treating pain syndromes.
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Affiliation(s)
- Wei-Guang Li
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031; Departments of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Ye Yu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031; Department of Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Chen Huang
- Departments of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Hui Cao
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031; Departments of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Tian-Le Xu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031; Departments of Biochemistry and Molecular Cell Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
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25
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Santos-Torres J, Ślimak MA, Auer S, Ibañez-Tallon I. Cross-reactivity of acid-sensing ion channel and Na⁺-H⁺ exchanger antagonists with nicotinic acetylcholine receptors. J Physiol 2011; 589:5109-23. [PMID: 21911609 DOI: 10.1113/jphysiol.2011.213272] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the mammalian central and peripheral nervous systems, where they contribute to neuronal excitability and synaptic communication. It has been reported that nAChRs are modulated by BK channels and that BK channels, in turn, are inhibited by acid-sensing ion channels (ASICs). Here we investigate the possible functional interaction between these channels in medial habenula (MHb) neurones. We report that selective antagonists of large-conductance calcium-activated potassium channels and ASIC1a channels, paxilline and psalmotoxin 1, respectively, did not induce detectable changes in nicotine-evoked currents. In contrast, the non-selective ASIC and Na(+)-H(+) exchanger (NHE1) antagonists, amiloride and its analogues, suppressed nicotine-evoked responses in MHb neurones of wild-type and ASIC2 null mice, excluding a possible involvement of ASIC2 in the nAChR inhibition by amiloride. Zoniporide, a more selective inhibitor of NHE1, reversibly inhibited α3β4-, α7- and α4-containing (*) nAChRs in Xenopus oocytes and in brain slices, as well as in PS120 cells deficient in NHE1 and virally transduced with nAChRs, suggesting a generalized effect of zoniporide in most neuronal nAChR subtypes. Independently from nAChR antagonism, zoniporide profoundly blocked synaptic transmission onto MHb neurones without affecting glutamatergic and GABA receptors. Taken together, these results indicate that amiloride and zoniporide, which are clinically used to treat hypertension and cardiovascular disease, have an inhibitory effect on neuronal nAChRs when used experimentally at high doses. The possible cross-reactivity of these compounds with nAChRs in vivo will require further investigation.
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Affiliation(s)
- Julio Santos-Torres
- Molecular Neurobiology Group, Department of Neuroscience, Max-Delbrück-Centrum, Berlin, Germany
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26
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Abstract
The distal nephron plays a critical role in the renal control of homeostasis. Until very recently most studies focused on the control of Na(+), K(+), and water balance by principal cells of the collecting duct and the regulation of solute and water by hormones from the renin-angiotensin-aldosterone system and by antidiuretic hormone. However, recent studies have revealed the unexpected importance of renal intercalated cells, a subtype of cells present in the connecting tubule and collecting ducts. Such cells were thought initially to be involved exclusively in acid-base regulation. However, it is clear now that intercalated cells absorb NaCl and K(+) and hence may participate in the regulation of blood pressure and potassium balance. The second paradigm-challenging concept we highlight is the emerging importance of local paracrine factors that play a critical role in the renal control of water and electrolyte balance.
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Affiliation(s)
- Dominique Eladari
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
- Département de Physiologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015, Paris, France
| | - Régine Chambrey
- Centre de Recherche des Cordeliers, Université Paris Descartes, INSERM UMRS 872, Equipe 3, F-75006, Paris, France; ,
- Université Pierre et Marie Curie, CNRS ERL7226, F-75006, Paris, France
| | - Janos Peti-Peterdi
- Department of Physiology and Biophysics, Keck School of Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California 90033;
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