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Tonggu L, Wisedchaisri G, Gamal El-Din TM, Lenaeus MJ, Logan MM, Toma T, Du Bois J, Zheng N, Catterall WA. Dual receptor-sites reveal the structural basis for hyperactivation of sodium channels by poison-dart toxin batrachotoxin. Nat Commun 2024; 15:2306. [PMID: 38485923 PMCID: PMC10940626 DOI: 10.1038/s41467-024-45958-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 02/08/2024] [Indexed: 03/18/2024] Open
Abstract
The poison dart toxin batrachotoxin is exceptional for its high potency and toxicity, and for its multifaceted modification of the function of voltage-gated sodium channels. By using cryogenic electron microscopy, we identify two homologous, but nonidentical receptor sites that simultaneously bind two molecules of toxin, one at the interface between Domains I and IV, and the other at the interface between Domains III and IV of the cardiac sodium channel. Together, these two bound toxin molecules stabilize α/π helical conformation in the S6 segments that gate the pore, and one of the bound BTX-B molecules interacts with the crucial Lys1421 residue that is essential for sodium conductance and selectivity via an apparent water-bridged hydrogen bond. Overall, our structure provides insight into batrachotoxin's potency, efficacy, and multifaceted functional effects on voltage-gated sodium channels via a dual receptor site mechanism.
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Affiliation(s)
- Lige Tonggu
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA
| | | | | | - Michael J Lenaeus
- Division of General Internal Medicine, Department of Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Matthew M Logan
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- Vividion Therapeutics, Inc., 5820 Nancy Ridge Dr., San Diego, CA, 92121, USA
| | - Tatsuya Toma
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
- PRISM BioLab Co., Ltd., 2-26-1 Muraokahigashi, Fujisawa-shi, Kanagawa, 251-8555, Japan
| | - Justin Du Bois
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Ning Zheng
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA.
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA.
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA.
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2
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Dos Santos Arraes DR, Rodrigues ABL, Sanches PR, Costa Campos CE, Moreira da Silva de Almeida SS, Reis Ferreira Lima J, Dias Lima J, da Silva GA. Bioactive alkaloids from the venom of Dendrobatoidea Cope, 1865: a scoping review. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2024; 27:1-20. [PMID: 37889647 DOI: 10.1080/10937404.2023.2270408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/29/2023]
Abstract
Bioactive compounds derived from secondary metabolism in animals have refined selectivity and potency for certain biological targets. The superfamily Dendrobatoidea is adapted to the dietary sequestration and secretion of toxic alkaloids, which play a role in several biological activities, and thus serve as a potential source for pharmacological and biotechnological applications. This article constitutes a scoping review to understand the trends in experimental research involving bioactive alkaloids derived from Dendrobatoidea based upon scientometric approaches. Forty-eight (48) publications were found in 30 journals in the period of 60 years, between 1962 and 2022. More than 23 structural classes of alkaloids were cited, with 27.63% for batrachotoxins, 13.64% for pyridinics, with an emphasis on epibatidine, 16.36% for pumiliotoxins, and 11.82% for histrionicotoxins. These tests included in vivo (54.9%), in vitro (39.4%), and in silico simulations (5.6%). Most compounds (54.8%) were isolated from skin extracts, whereas the remainder were obtained through molecular synthesis. Thirteen main biological activities were identified, including acetylcholinesterase inhibitors (27.59%), sodium channel inhibitors (12.07%), cardiac (12.07%), analgesic (8.62%), and neuromuscular effects (8.62%). The substances were cited as being of natural origin in the "Dendrobatidae" family, genus "Phyllobates," "Dendrobates," and seven species: Epipedobates tricolor, Phyllobates aurotaenia, Oophaga histrionica, Oophaga pumilio, Phyllobates terribilis, Epipedobates anthonyi, and Ameerega flavopicta. To date, only a few biological activities have been experimentally tested; hence, further studies on the bioprospecting of animal compounds and ecological approaches are needed.
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Affiliation(s)
| | | | | | | | | | - Janaina Reis Ferreira Lima
- Herpetology Laboratory, Institute of Scientific and Technological Research of the State of Amapá, Macapá, Amapá, Brazil
| | - Jucivaldo Dias Lima
- Herpetology Laboratory, Institute of Scientific and Technological Research of the State of Amapá, Macapá, Amapá, Brazil
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Llanos MA, Enrique N, Esteban-López V, Scioli-Montoto S, Sánchez-Benito D, Ruiz ME, Milesi V, López DE, Talevi A, Martín P, Gavernet L. A Combined Ligand- and Structure-Based Virtual Screening To Identify Novel NaV1.2 Blockers: In Vitro Patch Clamp Validation and In Vivo Anticonvulsant Activity. J Chem Inf Model 2023; 63:7083-7096. [PMID: 37917937 DOI: 10.1021/acs.jcim.3c00645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Epilepsy is a neurological disorder characterized by recurrent seizures that arise from abnormal electrical activity in the brain. Voltage-gated sodium channels (NaVs), responsible for the initiation and propagation of action potentials in neurons, play a critical role in the pathogenesis of epilepsy. This study sought to discover potential anticonvulsant compounds that interact with NaVs, specifically, the brain subtype hNaV1.2. A ligand-based QSAR model and a docking model were constructed, validated, and applied in a parallel virtual screening over the DrugBank database. Montelukast, Novobiocin, and Cinnarizine were selected for in vitro testing, using the patch-clamp technique, and all of them proved to inhibit hNaV1.2 channels heterologously expressed in HEK293 cells. Two hits were evaluated in the GASH/Sal model of audiogenic seizures and demonstrated promising activity, reducing the severity of sound-induced seizures at the doses tested. The combination of ligand- and structure-based models presents a valuable approach for identifying potential NaV inhibitors. These findings may provide a basis for further research into the development of new antiseizure drugs for the treatment of epilepsy.
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Affiliation(s)
- Manuel A Llanos
- Laboratory of Bioactive Compounds Research and Development (LIDeB), Department of Biological Sciences, Faculty of Exact Sciences, National University of La Plata (UNLP), La Plata B1900ADU, Argentina
| | - Nicolás Enrique
- Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, La Plata B1900BJW, Buenos Aires, Argentina
| | - Vega Esteban-López
- Institute for Neuroscience of Castilla y León (INCyL), University of Salamanca, Salamanca 37008, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca 37007, Spain
| | - Sebastian Scioli-Montoto
- Laboratory of Bioactive Compounds Research and Development (LIDeB), Department of Biological Sciences, Faculty of Exact Sciences, National University of La Plata (UNLP), La Plata B1900ADU, Argentina
| | - David Sánchez-Benito
- Institute for Neuroscience of Castilla y León (INCyL), University of Salamanca, Salamanca 37008, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca 37007, Spain
| | - María E Ruiz
- Laboratory of Bioactive Compounds Research and Development (LIDeB), Department of Biological Sciences, Faculty of Exact Sciences, National University of La Plata (UNLP), La Plata B1900ADU, Argentina
| | - Veronica Milesi
- Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, La Plata B1900BJW, Buenos Aires, Argentina
| | - Dolores E López
- Institute for Neuroscience of Castilla y León (INCyL), University of Salamanca, Salamanca 37008, Spain
- Institute for Biomedical Research of Salamanca (IBSAL), Salamanca 37007, Spain
| | - Alan Talevi
- Laboratory of Bioactive Compounds Research and Development (LIDeB), Department of Biological Sciences, Faculty of Exact Sciences, National University of La Plata (UNLP), La Plata B1900ADU, Argentina
| | - Pedro Martín
- Facultad de Ciencias Exactas, Departamento de Ciencias Biológicas, Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, La Plata B1900BJW, Buenos Aires, Argentina
| | - Luciana Gavernet
- Laboratory of Bioactive Compounds Research and Development (LIDeB), Department of Biological Sciences, Faculty of Exact Sciences, National University of La Plata (UNLP), La Plata B1900ADU, Argentina
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Modern Photocatalytic Strategies in Natural Product Synthesis. PROGRESS IN THE CHEMISTRY OF ORGANIC NATURAL PRODUCTS 2023; 120:1-104. [PMID: 36587307 DOI: 10.1007/978-3-031-11783-1_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Modern photocatalysis has proven its generality for the development and functionalization of native functionalities. To date, the field has found broad applications in diverse research areas, including the total synthesis of natural products. This contribution covers recent reports of total syntheses involving as a key step a photocatalytic reaction. Among the selected examples, the photocatalytic processes proceed in a highly chemo-, regio-, and stereoselective manner, thereby allowing the rapid access to structurally complex architectures under light-driven conditions.
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Wisedchaisri G, Gamal El-Din TM. Druggability of Voltage-Gated Sodium Channels-Exploring Old and New Drug Receptor Sites. Front Pharmacol 2022; 13:858348. [PMID: 35370700 PMCID: PMC8968173 DOI: 10.3389/fphar.2022.858348] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 03/01/2022] [Indexed: 01/12/2023] Open
Abstract
Voltage-gated ion channels are important drug targets because they play crucial physiological roles in both excitable and non-excitable cells. About 15% of clinical drugs used for treating human diseases target ion channels. However, most of these drugs do not provide sufficient specificity to a single subtype of the channels and their off-target side effects can be serious and sometimes fatal. Recent advancements in imaging techniques have enabled us for the first time to visualize unique and hidden parts of voltage-gated sodium channels in different structural conformations, and to develop drugs that further target a selected functional state in each channel subtype with the potential for high precision and low toxicity. In this review we describe the druggability of voltage-gated sodium channels in distinct functional states, which could potentially be used to selectively target the channels. We review classical drug receptors in the channels that have recently been structurally characterized by cryo-electron microscopy with natural neurotoxins and clinical drugs. We further examine recent drug discoveries for voltage-gated sodium channels and discuss opportunities to use distinct, state-dependent receptor sites in the voltage sensors as unique drug targets. Finally, we explore potential new receptor sites that are currently unknown for sodium channels but may be valuable for future drug discovery. The advancement presented here will help pave the way for drug development that selectively targets voltage-gated sodium channels.
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Affiliation(s)
- Goragot Wisedchaisri
- Department of Pharmacology, University of Washington, Seattle, WA, United States
| | - Tamer M Gamal El-Din
- Department of Pharmacology, University of Washington, Seattle, WA, United States
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6
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MacKenzie TMG, Abderemane-Ali F, Garrison CE, Minor DL, Bois JD. Differential effects of modified batrachotoxins on voltage-gated sodium channel fast and slow inactivation. Cell Chem Biol 2021; 29:615-624.e5. [PMID: 34963066 PMCID: PMC9035044 DOI: 10.1016/j.chembiol.2021.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 09/14/2021] [Accepted: 11/29/2021] [Indexed: 11/19/2022]
Abstract
Voltage-gated sodium channels (NaVs) are targets for a number of acute poisons. Many of these agents act as allosteric modulators of channel activity and serve as powerful chemical tools for understanding channel function. Herein, we detail studies with batrachotoxin (BTX), a potent steroidal amine, and three ester derivatives prepared through de novo synthesis against recombinant NaV subtypes (rNaV1.4 and hNaV1.5). Two of these compounds, BTX-B and BTX-cHx, are functionally equivalent to BTX, hyperpolarizing channel activation and blocking both fast and slow inactivation. BTX-yne-a C20-n-heptynoate ester-is a conspicuous outlier, eliminating fast but not slow inactivation. This property differentiates BTX-yne among other NaV modulators as a unique reagent that separates inactivation processes. These findings are supported by functional studies with bacterial NaVs (BacNaVs) that lack a fast inactivation gate. The availability of BTX-yne should advance future efforts aimed at understanding NaV gating mechanisms and designing allosteric regulators of NaV activity.
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Affiliation(s)
- Tim M G MacKenzie
- Department of Chemistry, Stanford University, 337 Campus Drive, Stanford, CA 94305, USA
| | - Fayal Abderemane-Ali
- Cardiovascular Research Institute, University of California, San Francisco, Box 3122, 555 Mission Bay Boulevard South, Rm. 452Z, San Francisco, CA 94158-9001, USA
| | - Catherine E Garrison
- Department of Chemistry, Stanford University, 337 Campus Drive, Stanford, CA 94305, USA
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California, San Francisco, Box 3122, 555 Mission Bay Boulevard South, Rm. 452Z, San Francisco, CA 94158-9001, USA; Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158-9001, USA; California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA 94158-9001, USA; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, CA 94158-9001, USA; Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - J Du Bois
- Department of Chemistry, Stanford University, 337 Campus Drive, Stanford, CA 94305, USA.
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Affiliation(s)
- Roberto Márquez
- Department of Ecology and Evolution, University of Chicago, Chicago, IL.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI
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8
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Structural Pharmacology of Voltage-Gated Sodium Channels. J Mol Biol 2021; 433:166967. [PMID: 33794261 DOI: 10.1016/j.jmb.2021.166967] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium (NaV) channels initiate and propagate action potentials in excitable tissues to mediate key physiological processes including heart contraction and nervous system function. Accordingly, NaV channels are major targets for drugs, toxins and disease-causing mutations. Recent breakthroughs in cryo-electron microscopy have led to the visualization of human NaV1.1, NaV1.2, NaV1.4, NaV1.5 and NaV1.7 channel subtypes at high-resolution. These landmark studies have greatly advanced our structural understanding of channel architecture, ion selectivity, voltage-sensing, electromechanical coupling, fast inactivation, and the molecular basis underlying NaV channelopathies. NaV channel structures have also been increasingly determined in complex with toxin and small molecule modulators that target either the pore module or voltage sensor domains. These structural studies have provided new insights into the mechanisms of pharmacological action and opportunities for subtype-selective NaV channel drug design. This review will highlight the structural pharmacology of human NaV channels as well as the potential use of engineered and chimeric channels in future drug discovery efforts.
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Van Theemsche KM, Van de Sande DV, Snyders DJ, Labro AJ. Hydrophobic Drug/Toxin Binding Sites in Voltage-Dependent K + and Na + Channels. Front Pharmacol 2020; 11:735. [PMID: 32499709 PMCID: PMC7243439 DOI: 10.3389/fphar.2020.00735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/04/2020] [Indexed: 12/26/2022] Open
Abstract
In the Nav channel family the lipophilic drugs/toxins binding sites and the presence of fenestrations in the channel pore wall are well defined and categorized. No such classification exists in the much larger Kv channel family, although certain lipophilic compounds seem to deviate from binding to well-known hydrophilic binding sites. By mapping different compound binding sites onto 3D structures of Kv channels, there appear to be three distinct lipid-exposed binding sites preserved in Kv channels: the front and back side of the pore domain, and S2-S3/S3-S4 clefts. One or a combination of these sites is most likely the orthologous equivalent of neurotoxin site 5 in Nav channels. This review describes the different lipophilic binding sites and location of pore wall fenestrations within the Kv channel family and compares it to the knowledge of Nav channels.
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Affiliation(s)
- Kenny M Van Theemsche
- Laboratory of Molecular, Cellular, and Network Excitability, University of Antwerp, Antwerp, Belgium
| | - Dieter V Van de Sande
- Laboratory of Molecular, Cellular, and Network Excitability, University of Antwerp, Antwerp, Belgium
| | - Dirk J Snyders
- Laboratory of Molecular, Cellular, and Network Excitability, University of Antwerp, Antwerp, Belgium
| | - Alain J Labro
- Laboratory of Molecular, Cellular, and Network Excitability, University of Antwerp, Antwerp, Belgium
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Guo Y, Guo Z, Lu JT, Fang R, Chen SC, Luo T. Total Synthesis of (-)-Batrachotoxinin A: A Local-Desymmetrization Approach. J Am Chem Soc 2020; 142:3675-3679. [PMID: 32036656 DOI: 10.1021/jacs.9b12882] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
An enantioselective total synthesis of (-)-batrachotoxinin A is accomplished based on a key photoredox coupling reaction and the subsequent local-desymmetrization operation. After the expedient assembly of the highly oxidized steroid skeleton, a delicate sequence of redox manipulations was carried out to deliver a late-stage intermediate on gram scale-and ultimately (-)-batrachotoxinin A in an efficient manner.
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Affiliation(s)
- Yinliang Guo
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Zhixian Guo
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Jia-Tian Lu
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Runting Fang
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Si-Cong Chen
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Tuoping Luo
- Key Laboratory of Bioorganic Chemistry and Molecular Engineering, Ministry of Education and Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
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11
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Liu J, Bayer JD, Aschar-Sobbi R, Wauchop M, Spears D, Gollob M, Vigmond EJ, Tsushima R, Backx PH, Chauhan VS. Complex interactions in a novel SCN5A compound mutation associated with long QT and Brugada syndrome: Implications for Na+ channel blocking pharmacotherapy for de novo conduction disease. PLoS One 2018; 13:e0197273. [PMID: 29791480 PMCID: PMC5965851 DOI: 10.1371/journal.pone.0197273] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 04/30/2018] [Indexed: 11/29/2022] Open
Abstract
Background The SCN5A mutation, P1332L, is linked to a malignant form of congenital long QT syndrome, type 3 (LQT3), and affected patients are highly responsive to the Na+ channel blocking drug, mexiletine. In contrast, A647D is an atypical SCN5A mutation causing Brugada syndrome. An asymptomatic male with both P1332L and A647D presented with varying P wave/QRS aberrancy and mild QTc prolongation which did not shorten measurably with mexiletine. Objective We characterized the biophysical properties of P1332L, A647D and wild-type (WT) Na+ channels as well as their combinations in order to understand our proband’s phenotype and to guide mexilitine therapy. Methods Na+ channel biophysics and mexilitine-binding kinetics were assessed using heterologous expression studies in CHO-K1 cells and human ventricular myocyte modeling. Results Compared to WT, P1332L channels displayed a hyperpolarizing shift in inactivation, slower inactivation and prominent late Na+ currents (INa). While A647D had no effect on the biophysical properties of INa, it reduced peak and late INa density when co-expressed with either WT or P1332L. Additionally, while P1332L channels had greater sensitivity to block by mexiletine compared to WT, this was reduced in the presence of A647D. Modelling studies revealed that mixing P1332L with A647D channels, action potential durations were shortened compared to P1332L, while peak INa was reduced compared to either A647D coexpressing with WT or WT alone. Conclusions While A647D mitigates the lethal LQT3 phenotype seen with P1332L, it also reduces mexilitine sensitivity and decreases INa density. These results explain our proband’s mild repolarization abnormality and prominent conduction defect in the atria and ventricles, but also suggest that expression of P1332L with A647D yields a novel disease phenotype for which mexiletine pharmacotherapy is no longer suitable.
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Affiliation(s)
- Jie Liu
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Jason D. Bayer
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University Foundation, Pessac, France
- University of Bordeaux, IMB, UMR 5251, Talance, France
| | | | - Marianne Wauchop
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Danna Spears
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
| | - Michael Gollob
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
| | - Edward J. Vigmond
- Electrophysiology and Heart Modeling Institute (LIRYC), Bordeaux University Foundation, Pessac, France
- University of Bordeaux, IMB, UMR 5251, Talance, France
| | - Robert Tsushima
- Department of Biology, York University, Toronto, Ontario, Canada
| | - Peter H. Backx
- Department of Biology, York University, Toronto, Ontario, Canada
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
- * E-mail: (PB); (VC)
| | - Vijay S. Chauhan
- Peter Munk Cardiac Center, Division of Cardiology, University Health Network, Toronto, Ontario, Canada
- * E-mail: (PB); (VC)
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Abstract
Voltage-gated sodium channels (VGSCs) are critical in generation and conduction of electrical signals in multiple excitable tissues. Natural toxins, produced by animal, plant, and microorganisms, target VGSCs through diverse strategies developed over millions of years of evolutions. Studying of the diverse interaction between VGSC and VGSC-targeting toxins has been contributing to the increasing understanding of molecular structure and function, pharmacology, and drug development potential of VGSCs. This chapter aims to summarize some of the current views on the VGSC-toxin interaction based on the established receptor sites of VGSC for natural toxins.
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Affiliation(s)
- Yonghua Ji
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, China.
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13
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Single rat muscle Na + channel mutation confers batrachotoxin autoresistance found in poison-dart frog Phyllobates terribilis. Proc Natl Acad Sci U S A 2017; 114:10491-10496. [PMID: 28874544 DOI: 10.1073/pnas.1707873114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Poison-dart Phyllobates terribilis frogs sequester lethal amounts of steroidal alkaloid batrachotoxin (BTX) in their skin as a defense mechanism against predators. BTX targets voltage-gated Na+ channels and enables them to open persistently. How BTX autoresistance arises in such frogs remains a mystery. The BTX receptor has been delineated along the Na+ channel inner cavity, which is formed jointly by four S6 transmembrane segments from domains D1 to D4. Within the P. terribilis muscle Na+ channel, five amino acid (AA) substitutions have been identified at D1/S6 and D4/S6. We therefore investigated the role of these naturally occurring substitutions in BTX autoresistance by introducing them into rat Nav1.4 muscle Na+ channel, both individually and in combination. Our results showed that combination mutants containing an N1584T substitution all conferred a complete BTX-resistant phenotype when expressed in mammalian HEK293t cells. The single N1584T mutant also retained its functional integrity and became exceptionally resistant to 5 µM BTX, aside from a small residual BTX effect. Single and combination mutants with the other four S6 residues (S429A, I433V, A445D, and V1583I) all remained highly BTX sensitive. These findings, along with diverse BTX phenotypes of N1584K/A/D/T mutant channels, led us to conclude that the conserved N1584 residue is indispensable for BTX actions, probably functioning as an integral part of the BTX receptor. Thus, complete BTX autoresistance found in P. terribilis muscle Na+ channels could emerge primarily from a single AA substitution (asparagine→threonine) via a single nucleotide mutation (AAC→ACC).
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Tsukamoto T, Chiba Y, Nakazaki A, Ishikawa Y, Nakane Y, Cho Y, Yotsu-Yamashita M, Nishikawa T, Wakamori M, Konoki K. Inhibition of veratridine-induced delayed inactivation of the voltage-sensitive sodium channel by synthetic analogs of crambescin B. Bioorg Med Chem Lett 2017; 27:1247-1251. [PMID: 28143690 DOI: 10.1016/j.bmcl.2017.01.054] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 12/19/2022]
Abstract
Crambescin B carboxylic acid, a synthetic analog of crambescin B, was recently found to inhibit the voltage-sensitive sodium channels (VSSC) in a cell-based assay using neuroblastoma Neuro 2A cells. In the present study, whole-cell patch-clamp recordings were conducted with three heterologously expressed VSSC subtypes, Nav1.2, Nav1.6 and Nav1.7, in a human embryonic kidney cell line HEK293T to further characterize the inhibition of VSSC by crambescin B carboxylic acid. Contrary to the previous observation, crambescin B carboxylic acid did not inhibit peak current evoked by depolarization from the holding potential of -100mV to the test potential of -10mV in the absence or presence of veratridine (VTD). In the presence of VTD, however, crambescin B carboxylic acid diminished VTD-induced sustained and tail currents through the three VSSC subtypes in a dose-dependent manner, whereas TTX inhibited both the peak current and the VTD-induced sustained and tail currents through all subtypes of VSSC tested. We thus concluded that crambescin B carboxylic acid does not block VSSC in a similar manner to TTX but modulate the action of VTD, thereby causing an apparent block of VSSC in the cell-based assay.
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Affiliation(s)
- Tadaaki Tsukamoto
- Graduate School of Agricultural Science, Tohoku University, Aoba, Sendai 981-8555, Japan
| | - Yukie Chiba
- Graduate School of Agricultural Science, Tohoku University, Aoba, Sendai 981-8555, Japan
| | - Atsuo Nakazaki
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Yuki Ishikawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Yoshiki Nakane
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Yuko Cho
- Graduate School of Dentistry, Tohoku University, Aoba, Sendai 980-8575, Japan
| | - Mari Yotsu-Yamashita
- Graduate School of Agricultural Science, Tohoku University, Aoba, Sendai 981-8555, Japan
| | - Toshio Nishikawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Minoru Wakamori
- Graduate School of Dentistry, Tohoku University, Aoba, Sendai 980-8575, Japan
| | - Keiichi Konoki
- Graduate School of Agricultural Science, Tohoku University, Aoba, Sendai 981-8555, Japan.
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15
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Israel MR, Tay B, Deuis JR, Vetter I. Sodium Channels and Venom Peptide Pharmacology. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2017; 79:67-116. [PMID: 28528674 DOI: 10.1016/bs.apha.2017.01.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Venomous animals including cone snails, spiders, scorpions, anemones, and snakes have evolved a myriad of components in their venoms that target the opening and/or closing of voltage-gated sodium channels to cause devastating effects on the neuromuscular systems of predators and prey. These venom peptides, through design and serendipity, have not only contributed significantly to our understanding of sodium channel pharmacology and structure, but they also represent some of the most phyla- and isoform-selective molecules that are useful as valuable tool compounds and drug leads. Here, we review our understanding of the basic function of mammalian voltage-gated sodium channel isoforms as well as the pharmacology of venom peptides that act at these key transmembrane proteins.
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Affiliation(s)
- Mathilde R Israel
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Bryan Tay
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Jennifer R Deuis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia.
| | - Irina Vetter
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia; School of Pharmacy, The University of Queensland, Brisbane, QLD, Australia.
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16
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Toma T, Logan MM, Menard F, Devlin AS, Du Bois J. Inhibition of Sodium Ion Channel Function with Truncated Forms of Batrachotoxin. ACS Chem Neurosci 2016; 7:1463-1468. [PMID: 27501251 DOI: 10.1021/acschemneuro.6b00212] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A novel family of small molecule inhibitors of voltage-gated sodium channels (NaVs) based on the structure of batrachotoxin (BTX), a well-known channel agonist, is described. Protein mutagenesis and electrophysiology experiments reveal the binding site as the inner pore region of the channel, analogous to BTX, alkaloid toxins, and local anesthetics. Homology modeling of the eukaryotic channel based on recent crystallographic analyses of bacterial NaVs suggests a mechanism of action for ion conduction block.
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Affiliation(s)
- Tatsuya Toma
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Matthew M. Logan
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Frederic Menard
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - A. Sloan Devlin
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - J. Du Bois
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
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17
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Ahern CA, Payandeh J, Bosmans F, Chanda B. The hitchhiker's guide to the voltage-gated sodium channel galaxy. ACTA ACUST UNITED AC 2016; 147:1-24. [PMID: 26712848 PMCID: PMC4692491 DOI: 10.1085/jgp.201511492] [Citation(s) in RCA: 217] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Eukaryotic voltage-gated sodium (Nav) channels contribute to the rising phase of action potentials and served as an early muse for biophysicists laying the foundation for our current understanding of electrical signaling. Given their central role in electrical excitability, it is not surprising that (a) inherited mutations in genes encoding for Nav channels and their accessory subunits have been linked to excitability disorders in brain, muscle, and heart; and (b) Nav channels are targeted by various drugs and naturally occurring toxins. Although the overall architecture and behavior of these channels are likely to be similar to the more well-studied voltage-gated potassium channels, eukaryotic Nav channels lack structural and functional symmetry, a notable difference that has implications for gating and selectivity. Activation of voltage-sensing modules of the first three domains in Nav channels is sufficient to open the channel pore, whereas movement of the domain IV voltage sensor is correlated with inactivation. Also, structure–function studies of eukaryotic Nav channels show that a set of amino acids in the selectivity filter, referred to as DEKA locus, is essential for Na+ selectivity. Structures of prokaryotic Nav channels have also shed new light on mechanisms of drug block. These structures exhibit lateral fenestrations that are large enough to allow drugs or lipophilic molecules to gain access into the inner vestibule, suggesting that this might be the passage for drug entry into a closed channel. In this Review, we will synthesize our current understanding of Nav channel gating mechanisms, ion selectivity and permeation, and modulation by therapeutics and toxins in light of the new structures of the prokaryotic Nav channels that, for the time being, serve as structural models of their eukaryotic counterparts.
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Affiliation(s)
- Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242
| | - Jian Payandeh
- Department of Structural Biology, Genentech, Inc., South San Francisco, CA 94080
| | - Frank Bosmans
- Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205 Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
| | - Baron Chanda
- Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705 Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705
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18
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Korkosh VS, Zhorov BS, Tikhonov DB. Folding similarity of the outer pore region in prokaryotic and eukaryotic sodium channels revealed by docking of conotoxins GIIIA, PIIIA, and KIIIA in a NavAb-based model of Nav1.4. ACTA ACUST UNITED AC 2015; 144:231-44. [PMID: 25156117 PMCID: PMC4144674 DOI: 10.1085/jgp.201411226] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Analyses of toxin binding to a homology model of Nav1.4 indicate similar folding of the outer pore region in eukaryotic and prokaryotic sodium channels. Voltage-gated sodium channels are targets for many drugs and toxins. However, the rational design of medically relevant channel modulators is hampered by the lack of x-ray structures of eukaryotic channels. Here, we used a homology model based on the x-ray structure of the NavAb prokaryotic sodium channel together with published experimental data to analyze interactions of the μ-conotoxins GIIIA, PIIIA, and KIIIA with the Nav1.4 eukaryotic channel. Using Monte Carlo energy minimizations and published experimentally defined pairwise contacts as distance constraints, we developed a model in which specific contacts between GIIIA and Nav1.4 were readily reproduced without deformation of the channel or toxin backbones. Computed energies of specific interactions between individual residues of GIIIA and the channel correlated with experimental estimates. The predicted complexes of PIIIA and KIIIA with Nav1.4 are consistent with a large body of experimental data. In particular, a model of Nav1.4 interactions with KIIIA and tetrodotoxin (TTX) indicated that TTX can pass between Nav1.4 and channel-bound KIIIA to reach its binding site at the selectivity filter. Our models also allowed us to explain experimental data that currently lack structural interpretations. For instance, consistent with the incomplete block observed with KIIIA and some GIIIA and PIIIA mutants, our computations predict an uninterrupted pathway for sodium ions between the extracellular space and the selectivity filter if at least one of the four outer carboxylates is not bound to the toxin. We found a good correlation between computational and experimental data on complete and incomplete channel block by native and mutant toxins. Thus, our study suggests similar folding of the outer pore region in eukaryotic and prokaryotic sodium channels.
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Affiliation(s)
- Viacheslav S Korkosh
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia
| | - Boris S Zhorov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S4L8, Canada
| | - Denis B Tikhonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia
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Zapata-Morin PA, Sierra-Valdez FJ, Ruiz-Suárez JC. The interaction of local anesthetics with lipid membranes. J Mol Graph Model 2014; 53:200-205. [PMID: 25181454 DOI: 10.1016/j.jmgm.2014.08.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Revised: 08/11/2014] [Accepted: 08/12/2014] [Indexed: 11/28/2022]
Abstract
Molecular Dynamic Simulations are performed to evaluate the interaction of lidocaine, procaine and tetracaine with a lipid membrane. The main interest is to evaluate the structural changes produced by these local anesthetics in the bilayers. Penetration trajectories, interaction energies, entropy changes and an order parameter are calculated to quantify the destabilization of the lipid configurations. We show that such structural parameters give important information to understand how anesthetic agents influence the structure of plasma membranes. Graphic processing units (GPUs) are used in our simulations.
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20
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Wang GK, Wang SY. Block of human cardiac sodium channels by lacosamide: evidence for slow drug binding along the activation pathway. Mol Pharmacol 2014; 85:692-702. [PMID: 24563546 DOI: 10.1124/mol.113.091173] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lacosamide is an anticonvulsant hypothesized to enhance slow inactivation of neuronal Na(+) channels for its therapeutic action. Cardiac Na(+) channels display less and incomplete slow inactivation, but their sensitivity toward lacosamide remains unknown. We therefore investigated the action of lacosamide in human cardiac Nav1.5 and Nav1.5-CW inactivation-deficient Na(+) channels. Lacosamide showed little effect on hNav1.5 Na(+) currents at 300 µM when cells were held at -140 mV. With 30-second conditioning pulses from -90 to -50 mV; however, hNav1.5 Na(+) channels became sensitive to lacosamide with IC50 (50% inhibitory concentration) around 70-80 µM. Higher IC50 values were found at -110 and -30 mV. The development of lacosamide block at -70 mV was slow in wild-type Na(+) channels (τ; 8.04 ± 0.39 seconds, n = 8). This time constant was significantly accelerated in hNav1.5-CW inactivation-deficient counterparts. The recovery from lacosamide block at -70 mV for 10 seconds was relatively rapid in wild-type Na(+) channels (τ; 639 ± 90 milliseconds, n = 8). This recovery was accelerated further in hNav1.5-CW counterparts. Unexpectedly, lacosamide elicited a time-dependent block of persistent hNav1.5-CW Na(+) currents with an IC50 of 242 ± 19 µM (n = 5). Furthermore, both hNav1.5-CW/F1760K mutant and batrachotoxin-activated hNav1.5 Na(+) channels became completely lacosamide resistant, indicating that the lacosamide receptor overlaps receptors for local anesthetics and batrachotoxin. Our results together suggest that lacosamide targets the intermediate preopen and open states of hNav1.5 Na(+) channels. Lacosamide may thus track closely the conformational changes at the hNav1.5-F1760 region along the activation pathway.
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Affiliation(s)
- Ging Kuo Wang
- Department of Anesthesiology, Perioperative, Pain Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts (G.K.W.); and Department of Biological Sciences, SUNY at Albany, Albany, New York (S.-Y.W.)
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21
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Abstract
Voltage-gated sodium (Nav) channels are essential contributors to neuronal excitability, making them the most commonly targeted ion channel family by toxins found in animal venoms. These molecules can be used to probe the functional aspects of Nav channels on a molecular level and to explore their physiological role in normal and diseased tissues. This chapter summarizes our existing knowledge of the mechanisms by which animal toxins influence Nav channels as well as their potential application in designing therapeutic drugs.
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22
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Small-fiber neuropathy Nav1.8 mutation shifts activation to hyperpolarized potentials and increases excitability of dorsal root ganglion neurons. J Neurosci 2013; 33:14087-97. [PMID: 23986244 DOI: 10.1523/jneurosci.2710-13.2013] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Idiopathic small-fiber neuropathy (I-SFN), clinically characterized by burning pain in distal extremities and autonomic dysfunction, is a disorder of small-caliber nerve fibers of unknown etiology with limited treatment options. Functional variants of voltage-gated sodium channel Nav1.7, encoded by SCN9A, have been identified in approximately one-third of I-SFN patients. These variants render dorsal root ganglion (DRG) neurons hyperexcitable. Sodium channel Nav1.8, encoded by SCN10A, is preferentially expressed in small-diameter DRG neurons, and produces most of the current underlying the upstroke of action potentials in these neurons. We previously demonstrated two functional variants of Nav1.8 that either enhance ramp current or shift activation in a hyperpolarizing direction, and render DRG neurons hyperexcitable, in I-SFN patients with no mutations of SCN9A. We have now evaluated additional I-SFN patients with no mutations in SCN9A, and report a novel I-SFN-related Nav1.8 mutation I1706V in a patient with painful I-SFN. Whole-cell voltage-clamp recordings in small DRG neurons demonstrate that the mutation hyperpolarizes activation and the response to slow ramp depolarizations. However, it decreases fractional channels resistant to fast inactivation and reduces persistent currents. Current-clamp studies reveal that mutant channels decrease current threshold and increase the firing frequency of evoked action potentials within small DRG neurons. These observations suggest that the effects of this mutation on activation and ramp current are dominant over the reduced persistent current, and show that these pro-excitatory gating changes confer hyperexcitability on peripheral sensory neurons, which may contribute to pain in this individual with I-SFN.
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23
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Nardi A, Damann N, Hertrampf T, Kless A. Advances in targeting voltage-gated sodium channels with small molecules. ChemMedChem 2012; 7:1712-40. [PMID: 22945552 DOI: 10.1002/cmdc.201200298] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 07/30/2012] [Indexed: 12/19/2022]
Abstract
Blockade of voltage-gated sodium channels (VGSCs) has been used successfully in the clinic to enable control of pathological firing patterns that occur in conditions as diverse as chronic pain, epilepsy, and arrhythmias. Herein we review the state of the art in marketed sodium channel inhibitors, including a brief compendium of their binding sites and of the cellular and molecular biology of sodium channels. Despite the preferential action of this drug class toward over-excited cells, which significantly limits potential undesired side effects on other cells, the need to develop a second generation of sodium channel inhibitors to overcome their critical clinical shortcomings is apparent. Current approaches in drug discovery to deliver novel and truly innovative sodium channel inhibitors is next presented by surveying the most recent medicinal chemistry breakthroughs in the field of small molecules and developments in automated patch-clamp platforms. Various strategies aimed at identifying small molecules that target either particular isoforms of sodium channels involved in specific diseases or anomalous sodium channel currents, irrespective of the isoform by which they have been generated, are critically discussed and revised.
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Affiliation(s)
- Antonio Nardi
- Global Drug Discovery, Department of Medicinal Chemistry, Grünenthal, Zieglerstrasse 6, 52078 Aachen, Germany.
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24
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Walls TH, Grindrod SC, Beraud D, Zhang L, Baheti AR, Dakshanamurthy S, Patel MK, Brown ML, MacArthur LH. Synthesis and biological evaluation of a fluorescent analog of phenytoin as a potential inhibitor of neuropathic pain and imaging agent. Bioorg Med Chem 2012; 20:5269-76. [PMID: 22863530 DOI: 10.1016/j.bmc.2012.06.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 06/18/2012] [Accepted: 06/25/2012] [Indexed: 11/16/2022]
Abstract
Here we report on a novel fluorescent analog of phenytoin as a potential inhibitor of neuropathic pain with potential use as an imaging agent. Compound 2 incorporated a heptyl side chain and dansyl moiety onto the parent compound phenytoin and produced greater displacement of BTX from sodium channels and greater functional blockade with greatly reduced toxicity. Compound 2 reduced mechano-allodynia in a rat model of neuropathic pain and was visualized ex vivo in sensory neuron axons with two-photon microscopy. These results suggest a promising strategy for developing novel sodium channel inhibitors with imaging capabilities.
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Affiliation(s)
- Thomas H Walls
- Drug Discovery Program, Department of Oncology, Georgetown University Medical Center, 3970 Reservoir Rd., NW, Washington, DC 20057, USA
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25
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Yoshinaka-Niitsu A, Yamagaki T, Harada M, Tachibana K. Solution NMR analysis of the binding mechanism of DIVS6 model peptides of voltage-gated sodium channels and the lipid soluble alkaloid veratridine. Bioorg Med Chem 2012; 20:2796-802. [PMID: 22483840 DOI: 10.1016/j.bmc.2012.03.034] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 03/14/2012] [Accepted: 03/15/2012] [Indexed: 10/28/2022]
Abstract
Voltage-gated sodium channels (VGSCs) are responsible for generating action potentials in nervous systems. Veratridine (VTD), a lipid soluble alkaloid isolated from sabadilla lily seed, is believed to bind to segment 6 of VGSCs and act as a partial agonist. However, high resolution structural interaction mechanism between VGSCs and VTD is difficult to elucidate because of the large size and membrane localization of VGSCs. Here, the authors designed model peptides corresponding to domain IV segment 6 (DIVS6) of rat skeletal muscle Na(v)1.4 and analyzed the complex of the model peptides and VTD by solution NMR analysis to obtain structural information of the interaction. The model peptides successfully formed an α-helices, which is the suspected native conformation of DIVS6, in aqueous 2,2,2-trifluoroethanol, a membrane-mimicking solvent. The VTD binding residues of the model peptide were identified using the NMR titration experiments with VTD, including a newly discovered VTD binding residue Leu14 (μ1-L1580 in Na(v)1.4), which has not been reported by point mutation studies. Mapping of VTD binding residues on the model peptide revealed the hydrophobic interaction surface. NMR titration experiments with a non-toxic analog of VTD, veracevine, also indicated that the steroidal backbone of VTD interacts with the hydrophobic interaction surface of DIVS6 and that the 3-acyl group of VTD possibly causes neurotoxicity by interacting with domain I segment 6 and/or domain IV segment 4.
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Affiliation(s)
- Ai Yoshinaka-Niitsu
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
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26
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Vickery RG, Amagasu SM, Chang R, Mai N, Kaufman E, Martin J, Hembrador J, O'Keefe MD, Gee C, Marquess D, Smith JAM. Comparison of the Pharmacological Properties of Rat NaV1.8 with Rat NaV1.2a and Human NaV1.5 Voltage-Gated Sodium Channel Subtypes Using a Membrane Potential Sensitive Dye and FLIPRR. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820490270410] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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27
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Worley JF, Main MJ. An Industrial Perspective on Utilizing Functional Ion Channel Assays for High Throughput Screening. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820214643] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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28
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Stevens M, Peigneur S, Tytgat J. Neurotoxins and their binding areas on voltage-gated sodium channels. Front Pharmacol 2011; 2:71. [PMID: 22084632 PMCID: PMC3210964 DOI: 10.3389/fphar.2011.00071] [Citation(s) in RCA: 179] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/24/2011] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Therefore, genetic defects in sodium channel genes can cause a wide variety of diseases, generally called “channelopathies.” The first insights into the mechanism of action potentials and the involvement of sodium channels originated from Hodgkin and Huxley for which they were awarded the Nobel Prize in 1963. These concepts still form the basis for understanding the function of VGSCs. When VGSCs sense a sufficient change in membrane potential, they are activated and consequently generate a massive influx of sodium ions. Immediately after, channels will start to inactivate and currents decrease. In the inactivated state, channels stay refractory for new stimuli and they must return to the closed state before being susceptible to a new depolarization. On the other hand, studies with neurotoxins like tetrodotoxin (TTX) and saxitoxin (STX) also contributed largely to our today’s understanding of the structure and function of ion channels and of VGSCs specifically. Moreover, neurotoxins acting on ion channels turned out to be valuable lead compounds in the development of new drugs for the enormous range of diseases in which ion channels are involved. A recent example of a synthetic neurotoxin that made it to the market is ziconotide (Prialt®, Elan). The original peptide, ω-MVIIA, is derived from the cone snail Conus magus and now FDA/EMA-approved for the management of severe chronic pain by blocking the N-type voltage-gated calcium channels in pain fibers. This review focuses on the current status of research on neurotoxins acting on VGSC, their contribution to further unravel the structure and function of VGSC and their potential as novel lead compounds in drug development.
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Affiliation(s)
- Marijke Stevens
- Lab of Toxicology, Katholieke Universiteit Leuven Leuven, Belgium
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29
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Davis GC, Kong Y, Paige M, Li Z, Merrick EC, Hansen T, Suy S, Wang K, Dakshanamurthy S, Cordova A, McManus OB, Williams BS, Chruszcz M, Minor W, Patel MK, Brown ML. Asymmetric synthesis and evaluation of a hydroxyphenylamide voltage-gated sodium channel blocker in human prostate cancer xenografts. Bioorg Med Chem 2011; 20:2180-8. [PMID: 22364743 DOI: 10.1016/j.bmc.2011.08.061] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 08/26/2011] [Accepted: 08/28/2011] [Indexed: 10/17/2022]
Abstract
Voltage-gated sodium channels are known to be expressed in neurons and other excitable cells. Recently, voltage-gated sodium channels have been found to be expressed in human prostate cancer cells. α-Hydroxy-α-phenylamides are a new class of small molecules that have demonstrated potent inhibition of voltage-gated sodium channels. The hydroxyamide motif, an isostere of a hydantoin ring, provides an active scaffold from which several potent racemic sodium channel blockers have been derived. With little known about chiral preferences, the development of chiral syntheses to obtain each pure enantiomer for evaluation as sodium channel blockers is important. Using Seebach and Frater's chiral template, cyclocondensation of (R)-3-chloromandelic acid with pivaldehyde furnished both the cis- and trans-2,5-disubsituted dioxolanones. Using this chiral template, we synthesized both enantiomers of 2-(3-chlorophenyl)-2-hydroxynonanamide, and evaluated their ability to functionally inhibit hNa(v) isoforms, human prostate cancer cells and xenograft. Enantiomers of lead demonstrated significant ability to reduce prostate cancer in vivo.
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Affiliation(s)
- Gary C Davis
- University of Virginia, Department of Chemistry, Charlottesville, VA 22901, USA
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30
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Inhibition of human Nav1.5 sodium channels by strychnine and its analogs. Biochem Pharmacol 2011; 82:350-7. [DOI: 10.1016/j.bcp.2011.05.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 04/15/2011] [Accepted: 05/09/2011] [Indexed: 11/19/2022]
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31
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Du Y, Khambay B, Dong K. An important role of a pyrethroid-sensing residue F1519 in the action of the N-alkylamide insecticide BTG 502 on the cockroach sodium channel. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 41:446-50. [PMID: 21426938 PMCID: PMC3118982 DOI: 10.1016/j.ibmb.2011.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/14/2011] [Accepted: 03/14/2011] [Indexed: 05/15/2023]
Abstract
Deltamethrin, a pyrethroid insecticide, and BTG 502, an alkylamide insecticide, target voltage-gated sodium channels. Deltamethrin binds to a unique receptor site and causes prolonged opening of sodium channels by inhibiting deactivation and inactivation. Previous (22)Na(+) influx and receptor binding assays using mouse brain synaptoneurosomes showed that BTG 502 antagonized the binding and action of batrachotoxin (BTX), a site 2 sodium channel neurotoxin. However, the effect of BTG 502 has not been examined directly on sodium channels expressed in Xenopus oocytes. In this study, we examined the effect of BTG 502 on wild-type and mutant cockroach sodium channels expressed in Xenopus oocytes. Toxin competition experiments confirmed that BTG 502 antagonizes the action of BTX and possibly shares a common receptor site with BTX. However, unlike BTX which causes persistent activation of sodium channels, BTG 502 reduces the amplitude of peak sodium current. A previous study showed that BTG 502 was more toxic to pyrethroid-resistant house flies possessing a super-kdr (knockdown resistance) mechanism than to pyrethroid-susceptible house flies. However, we found that the cockroach sodium channels carrying the equivalent super-kdr mutations (M918T and L1014F) were not more sensitive to BTG 502 than the wild-type channel. Instead, a kdr mutation, F1519I, which reduces pyrethroid binding, abolished the action of BTG 502. These results provide evidence the actions of alkylamide and pyrethroid insecticides require a common sodium channel residue.
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Affiliation(s)
- Yuzhe Du
- Department of Entomology, Genetics program and Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
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32
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McArthur JR, Singh G, McMaster D, Winkfein R, Tieleman DP, French RJ. Interactions of Key Charged Residues Contributing to Selective Block of Neuronal Sodium Channels by μ-Conotoxin KIIIA. Mol Pharmacol 2011; 80:573-84. [DOI: 10.1124/mol.111.073460] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Du Y, Garden D, Khambay B, Zhorov BS, Dong K. Batrachotoxin, pyrethroids, and BTG 502 share overlapping binding sites on insect sodium channels. Mol Pharmacol 2011; 80:426-33. [PMID: 21680776 DOI: 10.1124/mol.111.072504] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Batrachotoxin (BTX), a steroidal alkaloid, and pyrethroid insecticides bind to distinct but allosterically coupled receptor sites on voltage-gated sodium channels and cause persistent channel activation. BTX presumably binds in the inner pore, whereas pyrethroids are predicted to bind at the lipid-exposed cavity formed by the short intracellular linker-helix IIS4-S5 and transmembrane helices IIS5 and IIIS6. The alkylamide insecticide (2E,4E)-N-(1,2-dimethylpropyl)-6-(5-bromo-2-naphthalenyl)-2,4-hexadienamide (BTG 502) reduces sodium currents and antagonizes the action of BTX on cockroach sodium channels, suggesting that it also binds inside the pore. However, a pyrethroid-sensing residue, Phe(3i17) in IIIS6, which does not face the pore, is essential for the activity of BTG 502 but not for BTX. In this study, we found that three additional deltamethrin-sensing residues in IIIS6, Ile(3i12), Gly(3i14), and Phe(3i16) (the latter two are also BTX-sensing), and three BTX-sensing residues, Ser(3i15) and Leu(3i19) in IIIS6 and Phe(4i15) in IVS6, are all critical for BTG 502 action on cockroach sodium channels. Using these data as constraints, we constructed a BTG 502 binding model in which BTG 502 wraps around IIIS6, probably making direct contacts with all of the above residues on the opposite faces of the IIIS6 helix, except for the putative gating hinge Gly(3i14). BTG 502 and its inactive analog DAP 1855 antagonize the action of deltamethrin. The antagonism was eliminated by mutations of Ser(3i15), Phe(3i17), Leu(3i19), and Phe(4i15) but not by mutations of Ile(3i12), Gly(3i14), and Phe(3i16). Our analysis revealed a unique mode of action of BTG 502, its receptor site overlapping with those of both BTX and deltamethrin.
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Affiliation(s)
- Yuzhe Du
- Department of Entomology, Genetics and Neuroscience Programs, Michigan State University, East Lansing, MI 48824, USA
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Bregman H, Berry L, Buchanan JL, Chen A, Du B, Feric E, Hierl M, Huang L, Immke D, Janosky B, Johnson D, Li X, Ligutti J, Liu D, Malmberg A, Matson D, McDermott J, Miu P, Nguyen HN, Patel VF, Waldon D, Wilenkin B, Zheng XM, Zou A, McDonough SI, DiMauro EF. Identification of a Potent, State-Dependent Inhibitor of Nav1.7 with Oral Efficacy in the Formalin Model of Persistent Pain. J Med Chem 2011; 54:4427-45. [DOI: 10.1021/jm200018k] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Howard Bregman
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Loren Berry
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - John L. Buchanan
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - April Chen
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Bingfan Du
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Elma Feric
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Markus Hierl
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Liyue Huang
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - David Immke
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Brett Janosky
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Danielle Johnson
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Xingwen Li
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Joseph Ligutti
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Dong Liu
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Annika Malmberg
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - David Matson
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Jeff McDermott
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Peter Miu
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Hanh Nho Nguyen
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Vinod F. Patel
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Daniel Waldon
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Ben Wilenkin
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Xiao Mei Zheng
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Anruo Zou
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Stefan I. McDonough
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
| | - Erin F. DiMauro
- Department of Chemistry Research and Discovery, ‡Department of Pharmacokinetics and Drug Metabolism, and §Department of Neuroscience, Amgen Inc., 360 Binney Street, Cambridge, Massachusetts 02142, United States
- Department of Lead Discovery, and ⊥Department of Neuroscience, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, United States
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Du Y, Garden DP, Wang L, Zhorov BS, Dong K. Identification of new batrachotoxin-sensing residues in segment IIIS6 of the sodium channel. J Biol Chem 2011; 286:13151-60. [PMID: 21303907 PMCID: PMC3075662 DOI: 10.1074/jbc.m110.208496] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ion permeation through voltage-gated sodium channels is modulated by various drugs and toxins. The atomistic mechanisms of action of many toxins are poorly understood. A steroidal alkaloid batrachotoxin (BTX) causes persistent channel activation by inhibiting inactivation and shifting the voltage dependence of activation to more negative potentials. Traditionally, BTX is considered to bind at the channel-lipid interface and allosterically modulate the ion permeation. However, amino acid residues critical for BTX action are found in the inner helices of all four repeats, suggesting that BTX binds in the pore. In the octapeptide segment IFGSFFTL in IIIS6 of a cockroach sodium channel BgNa(V), besides Ser_3i15 and Leu_3i19, which correspond to known BTX-sensing residues of mammalian sodium channels, we found that Gly_3i14 and Phe_3i16 are critical for BTX action. Using these data along with published data as distance constraints, we docked BTX in the Kv1.2-based homology model of the open BgNa(V) channel. We arrived at a model in which BTX adopts a horseshoe conformation with the horseshoe plane normal to the pore axis. The BTX ammonium group is engaged in cation-π interactions with Phe_3i16 and BTX moieties interact with known BTX-sensing residues in all four repeats. Oxygen atoms at the horseshoe inner surface constitute a transient binding site for permeating cations, whereas the bulky BTX molecule would resist the pore closure, thus causing persistent channel activation. Our study reinforces the concept that steroidal sodium channel agonists bind in the inner pore of sodium channels and elaborates the atomistic mechanism of BTX action.
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Affiliation(s)
- Yuzhe Du
- Department of Entomology, Genetics and Neuroscience Programs, Michigan State University, East Lansing, Michigan 48824, USA
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36
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McArthur JR, Ostroumov V, Al-Sabi A, McMaster D, French RJ. Multiple, distributed interactions of μ-conotoxin PIIIA associated with broad targeting among voltage-gated sodium channels. Biochemistry 2010; 50:116-24. [PMID: 21110521 DOI: 10.1021/bi101316y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The first μ-conotoxin studied, μCTX GIIIA, preferentially blocked voltage-gated skeletal muscle sodium channels, Na(v)1.4, while μCTX PIIIA was the first to show significant blocking action against neuronal voltage-gated sodium channels. PIIIA shares >60% sequence identity with the well-studied GIIIA, and both toxins preferentially block the skeletal muscle sodium channel isoform. Two important features of blocking by wild-type GIIIA are the toxin's high binding affinity and the completeness of block of a single channel by a bound toxin molecule. With GIIIA, neutral replacement of the critical residue, Arg-13, allows a residual single-channel current (~30% of the unblocked, unitary amplitude) when the mutant toxin is bound to the channel and reduces the binding affinity of the toxin for Na(v)1.4 (~100-fold) [Becker, S., et al. (1992) Biochemistry 31, 8229-8238]. The homologous residue in PIIIA, Arg-14, is also essential for completeness of block but less important in the toxin's binding affinity (~55% residual current and ~11-fold decrease in affinity when substituted with alanine or glutamine). The weakened dominance of this key arginine in PIIIA is also seen in the fact that there is not just one (R13 in GIIIA) but three basic residues (R12, R14, and K17) for which individual neutral replacement enables a substantial residual current through the bound channel. We suggest that, despite a high degree of sequence conservation between GIIIA and PIIIA, the weaker dependence of PIIIA's action on its key arginine and the presence of a nonconserved histidine near the C-terminus may contribute to the greater promiscuity of its interactions with different sodium channel isoforms.
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Affiliation(s)
- Jeff R McArthur
- Department of Physiology and Pharmacology, and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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Yang YC, Hsieh JY, Kuo CC. The external pore loop interacts with S6 and S3-S4 linker in domain 4 to assume an essential role in gating control and anticonvulsant action in the Na(+) channel. ACTA ACUST UNITED AC 2009; 134:95-113. [PMID: 19635852 PMCID: PMC2717694 DOI: 10.1085/jgp.200810158] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Carbamazepine, phenytoin, and lamotrigine are widely prescribed anticonvulsants in neurological clinics. These drugs bind to the same receptor site, probably with the diphenyl motif in their structure, to inhibit the Na+ channel. However, the location of the drug receptor remains controversial. In this study, we demonstrate close proximity and potential interaction between an external aromatic residue (W1716 in the external pore loop) and an internal aromatic residue (F1764 in the pore-lining part of the sixth transmembrane segment, S6) of domain 4 (D4), both being closely related to anticonvulsant and/or local anesthetic binding to the Na+ channel. Double-mutant cycle analysis reveals significant cooperativity between the two phenyl residues for anticonvulsant binding. Concomitant F1764C mutation evidently decreases the susceptibility of W1716C to external Cd2+ and membrane-impermeable methanethiosulfonate reagents. Also, the W1716E/F1764R and G1715E/F1764R double mutations significantly alter the selectivity for Na+ over K+ and markedly shift the activation curve, respectively. W1716 and F1764 therefore very likely form a link connecting the outer and inner compartments of the Na+ channel pore (in addition to the selectivity filter). Anticonvulsants and local anesthetics may well traverse this “S6 recess” without trespassing on the selectivity filter. Furthermore, we found that Y1618K, a point mutation in the S3-4 linker (the extracellular extension of D4S4), significantly alters the consequences of carbamazepine binding to the Na+ channel. The effect of Y1618K mutation, however, is abolished by concomitant point mutations in the vicinity of Y1618, but not by those in the internally located inactivation machinery, supporting a direct local rather than a long-range allosteric action. Moreover, Y1618 could interact with D4 pore residues W1716 and L1719 to have a profound effect on both channel gating and anticonvulsant action. We conclude that there are direct interactions among the external S3-4 linker, the external pore loop, and the internal S6 segment in D4, making the external pore loop a pivotal point critically coordinating ion permeation, gating, and anticonvulsant binding in the Na+ channel.
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Affiliation(s)
- Ya-Chin Yang
- Department of Life Science, Chang-Gung University, Tao-Yuan, Taiwan
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38
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Lou BS, Lin TH, Lo CZ. The interactions of phenytoin and its binding site in DI-S6 segment of Na+ channel voltage-gated peptide by NMR spectroscopy and molecular modeling study. ACTA ACUST UNITED AC 2008; 66:27-38. [PMID: 15946193 DOI: 10.1111/j.1399-3011.2005.00269.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nuclear magnetic resonance (NMR) spectra of a model peptide (BL-DIS6), in the presence of anticonvulsant diphenyl drug, phenytoin (DPH), were measured to obtain the interactions between the selected drug and the model peptide. BL-DIS6's sequence corresponds to the S6 segment in domain I of rat brain type IIA Na+-channel. NMR studies have demonstrated that the magnitude of the chemical shifts of amide- and alpha-protons can be used as a measurement of the complex stability and binding site of the peptide. Our NMR results propose a 3(10)-helical structure for BL-DIS6, and suggest a binding cavity for DPH that involves the hydrophobic particles of residues Ans-7, Leu-8, Val-11, and Val-12. Furthermore, molecular modeling was performed to provide a possible complex conformation that the phenyl portion of DPH is accommodated in the proximity of the C-terminal residues Ala-11 and Val-12, and simultaneously the heterocyclic amine ring of DPH is perching at the residue Asn-7 periphery and stabilizing the phenyl portion deep insertion into the peptide.
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Affiliation(s)
- B-S Lou
- Chemistry Division, Center for General Education, Chang Gung University, Tao-Yuan, Taiwan.
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Tikhonov DB. Mechanisms of action of ligands of potential-dependent sodium channels. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2008; 38:461-9. [PMID: 18636331 DOI: 10.1007/s11055-008-9003-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Indexed: 10/21/2022]
Abstract
Potential-dependent sodium channels play a leading role in generating action potentials in excitable cells. Sodium channels are the site of action of a variety of modulator ligands. Despite numerous studies, the mechanisms of action of many modulators remain incompletely understood. The main reason that many important questions cannot be resolved is that there is a lack of precise data on the structures of the channels themselves. Structurally, potential-dependent sodium channels are members of the P-loop channel superfamily, which also include potassium and calcium channels and glutamate receptor channels. Crystallization of a series of potassium channels showed that it was possible to analyze the structures of different members of the superfamily using the "homologous modeling" method. The present study addresses model investigations of the actions of ligands of sodium channels, including tetrodotoxin and batrachotoxin, as well as local anesthetics. Comparison of experimental data on sodium channel ligands with x-ray analysis data allowed us to reach a new level of understanding of the mechanisms of channel modulation and to propose a series of experimentally verifiable hypotheses.
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Affiliation(s)
- D B Tikhonov
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 M. Torez Prospekt, St. Petersburg, Russia
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Chen Y, Yu FH, Sharp EM, Beacham D, Scheuer T, Catterall WA. Functional properties and differential neuromodulation of Na(v)1.6 channels. Mol Cell Neurosci 2008; 38:607-15. [PMID: 18599309 DOI: 10.1016/j.mcn.2008.05.009] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 03/25/2008] [Accepted: 05/07/2008] [Indexed: 12/19/2022] Open
Abstract
The voltage-gated sodium channel Na(v)1.6 plays unique roles in the nervous system, but its functional properties and neuromodulation are not as well established as for Na(V)1.2 channels. We found no significant differences in voltage-dependent activation or fast inactivation between Na(V)1.6 and Na(V)1.2 channels expressed in non-excitable cells. In contrast, the voltage dependence of slow inactivation was more positive for Na(v)1.6 channels, they conducted substantially larger persistent sodium currents than Na(v)1.2 channels, and they were much less sensitive to inhibition by phosphorylation by cAMP-dependent protein kinase and protein kinase C. Resurgent sodium current, a hallmark of Na(v)1.6 channels in neurons, was not observed for Na(V)1.6 expressed alone or with the auxiliary beta(4) subunit. The unique properties of Na(V)1.6 channels, together with the resurgent currents that they conduct in neurons, make these channels well-suited to provide the driving force for sustained repetitive firing, a crucial property of neurons.
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Affiliation(s)
- Yuan Chen
- Department of Pharmacology, Mailstop 357280, University of Washington, Seattle, WA 98195, USA
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Lee JH, Lee BH, Choi SH, Yoon IS, Shin TJ, Pyo MK, Lee SM, Kim HC, Nah SY. Involvement of batrachotoxin binding sites in ginsenoside-mediated voltage-gated Na+ channel regulation. Brain Res 2008; 1203:61-7. [PMID: 18321475 DOI: 10.1016/j.brainres.2008.01.078] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 12/18/2007] [Accepted: 01/04/2008] [Indexed: 11/19/2022]
Abstract
Recently, we showed that the 20(S)-ginsenoside Rg3 (Rg3), an active ingredient of Panax ginseng, inhibits rat brain NaV1.2 channel peak currents (INa). Batrachotoxin (BTX) is a steroidal alkaloid neurotoxin and activates NaV channels through interacting with transmembrane domain-I-segment 6 (IS6) of channels. Recent report shows that ginsenoside inhibits BTX binding in rat brain membrane fractions. However, it needs to be confirmed whether biochemical mechanism is relevant physiologically and which residues of the BTX binding sites are important for ginsenoside regulations. Here, we demonstrate that mutations of BTX binding sites such as N418K and L421K of rat brain NaV1.2 and L437K of mouse skeletal muscle NaV1.4 channel reduce or abolish Rg3 inhibition of I(Na) and attenuate Rg3-mediated depolarizing shift of the activation voltage and use-dependent inhibition. These results indicate that BTX binding sites play an important role in modifying Rg3-mediated Na+ channel properties.
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Affiliation(s)
- Jun-Ho Lee
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul Korea, 143-701
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Sites and molecular mechanisms of modulation of Na(v)1.2 channels by Fyn tyrosine kinase. J Neurosci 2007; 27:11543-51. [PMID: 17959797 DOI: 10.1523/jneurosci.1743-07.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Voltage-gated sodium channels are important targets for modulation of electrical excitability by neurotransmitters and neurotrophins acting through protein phosphorylation. Fast inactivation of Na(V)1.2 channels is regulated via tyrosine phosphorylation by Fyn kinase and dephosphorylation by receptor phosphoprotein tyrosine phosphatase-beta, which are associated in a signaling complex. Here we have identified the amino acid residues on Na(V)1.2 channels that coordinate binding of Fyn kinase and mediate inhibition of sodium currents by enhancing fast inactivation. Fyn kinase binds to a Src homology 3 (SH3)-binding motif in the second half of the intracellular loop connecting domains I and II (L(I-II)) of Na(V)1.2, and mutation of that SH3-binding motif prevents Fyn binding and Fyn enhancement of fast inactivation of sodium currents. Analysis of tyrosine phosphorylation sites by mutagenesis and functional expression revealed a multisite regulatory mechanism. Y66 and Y1893, which are in consensus sequences appropriate for binding to the Fyn SH2 domain after phosphorylation, are both required for optimal binding and regulation by Fyn. Y730, which is located near the SH3-binding motif in L(I-II), and Y1497 and Y1498 in the inactivation gate in L(III-IV), are also required for optimal regulation. Phosphorylation of these sites likely promotes fast inactivation. Fast inactivation of the closely related Na(V)1.1 channels is not modulated by Fyn, and these channels do not contain an SH3-binding motif in L(I-II). Subtype-selective modulation by tyrosine phosphorylation/dephosphorylation provides a mechanism for differential regulation of sodium channels by neurotrophins and tyrosine phosphorylation in unmyelinated axons and dendrites, where Na(V)1.2 channels are expressed in brain neurons.
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43
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Fredj S, Sampson KJ, Liu H, Kass RS. Molecular basis of ranolazine block of LQT-3 mutant sodium channels: evidence for site of action. Br J Pharmacol 2007; 148:16-24. [PMID: 16520744 PMCID: PMC1617037 DOI: 10.1038/sj.bjp.0706709] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
1 We studied the effects of ranolazine, an antianginal agent with promise as an antiarrhythmic drug, on wild-type (WT) and long QT syndrome variant 3 (LQT-3) mutant Na(+) channels expressed in human embryonic kidney (HEK) 293 cells and knock-in mouse cardiomyocytes and used site-directed mutagenesis to probe the site of action of the drug. 2 We find preferential ranolazine block of sustained vs peak Na(+) channel current for LQT-3 mutant (DeltaKPQ and Y1795C) channels (IC(50)=15 vs 135 microM) with similar results obtained in HEK 293 cells and knock-in myocytes. 3 Ranolazine block of both peak and sustained Na(+) channel current is significantly reduced by mutation (F1760A) of a single residue previously shown to contribute critically to the binding site for local anesthetic (LA) molecules in the Na(+) channel. 4 Ranolazine significantly decreases action potential duration (APD) at 50 and 90% repolarization by 23+/-5 and 27+/-3%, respectively, in DeltaKPQ mouse ventricular myocytes but has little effect on APD of WT myocytes. 5 Computational modeling of human cardiac myocyte electrical activity that incorporates our voltage-clamp data predicts marked ranolazine-induced APD shortening in cells expressing LQT-3 mutant channels. 6 Our results demonstrate for the first time the utility of ranolazine as a blocker of sustained Na(+) channel activity induced by inherited mutations that cause human disease and further, that these effects are very likely due to interactions of ranolazine with the receptor site for LA molecules in the sodium channel.
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Affiliation(s)
- Sandra Fredj
- Department of Pharmacology, Columbia University Medical Center, 630 W. 168th S., New York, NY 10032, U.S.A
| | - Kevin J Sampson
- Department of Pharmacology, Columbia University Medical Center, 630 W. 168th S., New York, NY 10032, U.S.A
| | - Huajun Liu
- Department of Pharmacology, Columbia University Medical Center, 630 W. 168th S., New York, NY 10032, U.S.A
| | - Robert S Kass
- Department of Pharmacology, Columbia University Medical Center, 630 W. 168th S., New York, NY 10032, U.S.A
- Author for correspondence:
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44
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Catterall WA, Cestèle S, Yarov-Yarovoy V, Yu FH, Konoki K, Scheuer T. Voltage-gated ion channels and gating modifier toxins. Toxicon 2007; 49:124-41. [PMID: 17239913 DOI: 10.1016/j.toxicon.2006.09.022] [Citation(s) in RCA: 447] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Voltage-gated sodium, calcium, and potassium channels generate electrical signals required for action potential generation and conduction and are the molecular targets for a broad range of potent neurotoxins. These channels are built on a common structural motif containing six transmembrane segments and a pore loop. Their pores are formed by the S5/S6 segments and the pore loop between them, and they are gated by bending of the S6 segments at a hinge glycine or proline residue. The voltage sensor domain consists of the S1-S4 segments, with positively charged residues in the S4 segment serving as gating charges. The diversity of toxin action on these channels is illustrated by sodium channels, which are the molecular targets for toxins that act at six or more distinct receptor sites on the channel protein. Both hydrophilic low molecular weight toxins and larger polypeptide toxins physically block the pore and prevent sodium conductance. Hydrophobic alkaloid toxins and related lipid-soluble toxins act at intramembrane sites and alter voltage-dependent gating of sodium channels via an allosteric mechanism. In contrast, polypeptide toxins alter channel gating by voltage-sensor trapping through binding to extracellular receptor sites, and this toxin interaction has now been modeled at the atomic level for a beta-scorpion toxin. The voltage-sensor trapping mechanism may be a common mode of action for polypeptide gating modifier toxins acting on all of the voltage-gated ion channels.
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA.
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45
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Wang SY, Tikhonov DB, Zhorov BS, Mitchell J, Wang GK. Serine-401 as a batrachotoxin- and local anesthetic-sensing residue in the human cardiac Na+ channel. Pflugers Arch 2007; 454:277-87. [PMID: 17205354 DOI: 10.1007/s00424-006-0202-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Accepted: 12/12/2006] [Indexed: 11/26/2022]
Abstract
Sequence alignment of four S6 segments in the human cardiac Na+ channel suggests that serine-401 (hNav1.5-S401) at D1S6 along with asparagine-927 (N927) at D2S6, serine-1458 (S1458) at D3S6, and phenylalanine-1760 (F1760) at D4S6 may jointly form a pore-facing S(401)N(927)S(1458)F(1760) ring. Importantly, this pore-facing structure is adjacent to the putative gating-hinge (G(400)G(926)G(1457)S(1759)) and close to the selectivity filter. Within this SNSF ring, only S401 has not yet been identified as a batrachotoxin (BTX) sensing residue. We therefore created S401 mutants with 12 substitutions (S401C,W,P,A,K,F,R,E,L,N,D,G) and assayed their BTX sensitivity. All S401 mutants expressed Na+ currents but often with altered gating characteristics. Ten mutants were found sensitive to 5 muM BTX, which eliminated Na+ channel fast inactivation after repetitive pulses. However, S401K and S401R became BTX resistant. In addition, the block of open and inactivated hNav1.5-S401K Na+ channels by local anesthetic bupivacaine was reduced by approximately 8-10-fold, but not the block of resting Na+ channels. Qualitatively, these ligand-sensing phenotypes of hNav1.5-S401K channels resemble those of S1458K and F1760K channels reported earlier. Together, our results support that residue hNav1.5-S401 at D1S6 is facing the inner cavity and is in close proximity to the receptor sites for BTX and for local anesthetics.
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Affiliation(s)
- Sho-Ya Wang
- Department of Biology, State University of New York at Albany, Albany, NY 12222, USA.
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46
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Williams WR. Voltage-gated Na+ channel ligands and ATP: relative molecular similarity and implications for channel function. J Pharm Pharmacol 2006; 58:1235-41. [PMID: 16945182 DOI: 10.1211/jpp.58.9.0010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The voltage-gated sodium channel (VGNC) is targeted by naturally occurring ligands and drugs of diverse structure. ATP modulates VGNC current in-vitro but is given little prominence in models describing channel function. This computational study uses superimposition and molecular fitting to investigate relative molecular similarity within the structures of ATP and VGNC ligands. A motif of 3 linked atoms (C-N-C) in the adenine ring of ATP satisfies the fitting of a wide range of anticonvulsant structures. An alternative group (N-C-N) provides one fitting motif for the ester and amide groups of local anaesthetic drugs; protonated amine and aromatic groups in the same conformers fit to a second motif in the adenine ring. Analogous structures from other drug classes with VGNC blocking activity give the same molecular fits to ATP. Structures fitted to the adenine ring of ATP occlude the intra-molecular space between the nucleoside and triphosphate chain in approximation to their established blocking, activating or neutral effects on Na+ current. The findings are discussed in terms of drug preferences for VGNC states and channel requirements for ATP.
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Affiliation(s)
- W R Williams
- School of Care Sciences, University of Glamorgan, Pontypridd CF37 1DL, UK.
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47
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Popa MO, Lerche H. Cu2+ (1,10 phenanthroline)3 is an open-channel blocker of the human skeletal muscle sodium channel. Br J Pharmacol 2006; 147:808-14. [PMID: 16432503 PMCID: PMC1751503 DOI: 10.1038/sj.bjp.0706667] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The formation of disulfide bridges is a classical approach used to study the mobility, proximity and distances of residues in a variety of proteins, including ligand- and voltage-gated ion channels. We performed patch-clamp studies to investigate the interaction of a pair of cysteines introduced into the human skeletal muscle voltage-gated Na+ channel (hNa(v)1.4) using the oxidation catalyst, Cu2+ (1,10-phenanthroline)3 (CuPhen). Our experiments resulted in a surprising finding, a reversible current inhibition of the mutant I1160C/L1482C containing two cysteines in the D3/and D4/S4-S5 loops, subjected to oxidative cross-linking in the presence of CuPhen. We report here that CuPhen is an open channel blocker of both mutant and wild-type (WT) hNa(v)1.4 channels, however, for WT channels a more than 10-fold higher concentration was needed to induce the same effect. Moreover, 1,10-phenanthroline was capable of blocking Na+ channels in the absence of Cu2+ ions. Our results indicate a use- and voltage-dependent binding and unbinding of CuPhen, reminiscent of the lidocaine quaternary derivative QX-314 and the neurotoxin batrachotoxin. Care should be taken when using CuPhen as an oxidizing reagent in cross-linking experiments, since it may directly affect channel activity. Our results identify CuPhen (and phenantroline) as a novel use-dependent inhibitor of Na+ channels, a mechanism that is shared by drugs widely used in the treatment of epilepsy, neuropathic pain, cardiac arrhythmia and myotonia. We hypothesize that I1160C in D3/S4-S5 and the corresponding L1482C mutation in D4/S4-S5 could allosterically affect a binding site located in the inner pore region of the channel.
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Affiliation(s)
- Mariana Oana Popa
- Departments of Neurology and Applied Physiology, University of Ulm, D-89069 Ulm, Germany
| | - Holger Lerche
- Departments of Neurology and Applied Physiology, University of Ulm, D-89069 Ulm, Germany
- Author for correspondence:
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48
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Wang GK, Edrich T, Wang SY. Time-dependent block and resurgent tail currents induced by mouse beta4(154-167) peptide in cardiac Na+ channels. ACTA ACUST UNITED AC 2006; 127:277-89. [PMID: 16505148 PMCID: PMC2151501 DOI: 10.1085/jgp.200509399] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Resurgent tail Na+ currents were first discovered in cerebellar Purkinje neurons. A recent study showed that a 14-mer fragment of a mouse β4 subunit, β4154–167, acts as an intracellular open-channel blocker and elicits resurgent currents in Purkinje neurons (Grieco, T.M., J.D. Malhotra, C. Chen, L.L. Isom, and I.M. Raman. 2005. Neuron. 45:233–244). To explore these phenotypes in vitro, we characterized β4154–167 actions in inactivation-deficient cardiac hNav1.5 Na+ channels expressed in human embryonic kidney 293t cells. Intracellular β4154–167 from 25–250 μM elicited a conspicuous time-dependent block of inactivation-deficient Na+ currents at 50 mV in a concentration-dependent manner. On and off rates for β4154–167 binding were estimated at 10.1 μM−1s−1 and 49.1 s−1, respectively. Upon repolarization, large tail currents emerged with a slight delay at −140 mV, probably as a result of the rapid unblocking of β4154–167. Near the activation threshold (approximately −70 mV), resurgent tail currents were robust and long lasting. Likewise, β4154–167 induces resurgent currents in wild-type hNav1.5 Na+ channels, although to a lesser extent. The inactivation peptide acetyl-KIFMK-amide not only restored the fast inactivation phenotype in hNav1.5 inactivation-deficient Na+ channels but also elicited robust resurgent currents. When modified by batrachotoxin (BTX), wild-type hNav1.5 Na+ channels opened persistently but became resistant to β4154–167 and acetyl-KIFMK-amide block. Finally, a lysine substitution of a phenylalanine residue at D4S6, F1760, which forms a part of receptors for local anesthetics and BTX, rendered cardiac Na+ channels resistant to β4154–167. Together, our in vitro studies identify a putative S6-binding site for β4154–167 within the inner cavity of hNav1.5 Na+ channels. Such an S6 receptor readily explains (1) why β4154–167 gains access to its receptor as an open-channel blocker, (2), why bound β4154–167 briefly prevents the activation gate from closing by a “foot-in-the-door” mechanism during deactivation, (3) why BTX inhibits β4154–167 binding by physical exclusion, and (4) why a lysine substitution of residue F1760 eliminates β4154–167 binding.
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Affiliation(s)
- Ging Kuo Wang
- Department of Anesthesia, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA.
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49
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Chen Y, Yu FH, Surmeier DJ, Scheuer T, Catterall WA. Neuromodulation of Na+ channel slow inactivation via cAMP-dependent protein kinase and protein kinase C. Neuron 2006; 49:409-20. [PMID: 16446144 DOI: 10.1016/j.neuron.2006.01.009] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 10/07/2005] [Accepted: 01/05/2006] [Indexed: 12/14/2022]
Abstract
Neurotransmitters modulate sodium channel availability through activation of G protein-coupled receptors, cAMP-dependent protein kinase (PKA), and protein kinase C (PKC). Voltage-dependent slow inactivation also controls sodium channel availability, synaptic integration, and neuronal firing. Here we show by analysis of sodium channel mutants that neuromodulation via PKA and PKC enhances intrinsic slow inactivation of sodium channels, making them unavailable for activation. Mutations in the S6 segment in domain III (N1466A,D) either enhance or block slow inactivation, implicating S6 segments in the molecular pathway for slow inactivation. Modulation of N1466A channels by PKC or PKA is increased, whereas modulation of N1466D is nearly completely blocked. These results demonstrate that neuromodulation by PKA and PKC is caused by their enhancement of intrinsic slow inactivation gating. Modulation of slow inactivation by neurotransmitters acting through G protein-coupled receptors, PKA, and PKC is a flexible mechanism of cellular plasticity controlling the firing behavior of central neurons.
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Affiliation(s)
- Yuan Chen
- Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA
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50
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Mantegazza M, Yu FH, Powell AJ, Clare JJ, Catterall WA, Scheuer T. Molecular determinants for modulation of persistent sodium current by G-protein betagamma subunits. J Neurosci 2006; 25:3341-9. [PMID: 15800189 PMCID: PMC6724911 DOI: 10.1523/jneurosci.0104-05.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels are responsible for the upstroke of the action potential in most excitable cells, and their fast inactivation is essential for controlling electrical signaling. In addition, a noninactivating, persistent component of sodium current, I(NaP), has been implicated in integrative functions of neurons including threshold for firing, neuronal bursting, and signal integration. G-protein betagamma subunits increase I(NaP), but the sodium channel subtypes that conduct I(NaP) and the target site(s) on the sodium channel molecule required for modulation by Gbetagamma are poorly defined. Here, we show that I(NaP) conducted by Na(v)1.1 and Na(v)1.2 channels (Na(v)1.1 > Na(v)1.2) is modulated by Gbetagamma; Na(v)1.4 and Na(v)1.5 channels produce smaller I(NaP) that is not regulated by Gbetagamma. These qualitative differences in modulation by Gbetagamma are determined by the transmembrane body of the sodium channels rather than their cytoplasmic C-terminal domains, which have been implicated previously in modulation by Gbetagamma. However, the C-terminal domains determine the quantitative extent of modulation of Na(v)1.2 channels by Gbetagamma. Studies of chimeric and truncated Na(v)1.2 channels identify molecular determinants that affect modulation of I(NaP) located between amino acid residue 1890 and the C terminus at residue 2005. The last 28 amino acid residues of the C terminus are sufficient to support modulation by Gbetagamma when attached to the proximal C-terminal domain. Our results further define the sodium channel subtypes that generate I(NaP) and identify crucial molecular determinants in the C-terminal domain required for modulation by Gbetagamma when attached to the transmembrane body of a responsive sodium channel.
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Affiliation(s)
- Massimo Mantegazza
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington 98195-7280, USA
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