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Schroder RV, Cohen LS, Wang P, Arizala JD, Poget SF. Expression, Purification and Refolding of a Human Na V1.7 Voltage Sensing Domain with Native-like Toxin Binding Properties. Toxins (Basel) 2021; 13:toxins13100722. [PMID: 34679015 PMCID: PMC8541342 DOI: 10.3390/toxins13100722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/04/2021] [Accepted: 10/04/2021] [Indexed: 01/28/2023] Open
Abstract
The voltage-gated sodium channel NaV1.7 is an important target for drug development due to its role in pain perception. Recombinant expression of full-length channels and their use for biophysical characterization of interactions with potential drug candidates is challenging due to the protein size and complexity. To overcome this issue, we developed a protocol for the recombinant expression in E. coli and refolding into lipids of the isolated voltage sensing domain (VSD) of repeat II of NaV1.7, obtaining yields of about 2 mg of refolded VSD from 1 L bacterial cell culture. This VSD is known to be involved in the binding of a number of gating-modifier toxins, including the tarantula toxins ProTx-II and GpTx-I. Binding studies using microscale thermophoresis showed that recombinant refolded VSD binds both of these toxins with dissociation constants in the high nM range, and their relative binding affinities reflect the relative IC50 values of these toxins for full-channel inhibition. Additionally, we expressed mutant VSDs incorporating single amino acid substitutions that had previously been shown to affect the activity of ProTx-II on full channel. We found decreases in GpTx-I binding affinity for these mutants, consistent with a similar binding mechanism for GpTx-I as compared to that of ProTx-II. Therefore, this recombinant VSD captures many of the native interactions between NaV1.7 and tarantula gating-modifier toxins and represents a valuable tool for elucidating details of toxin binding and specificity that could help in the design of non-addictive pain medication acting through NaV1.7 inhibition.
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Affiliation(s)
- Ryan V. Schroder
- Department of Chemistry, College of Staten Island, University of New York, 2800 Victory Blvd., Staten Island, NY 10314, USA; (R.V.S.); (L.S.C.); (P.W.); (J.D.A.)
- The Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Leah S. Cohen
- Department of Chemistry, College of Staten Island, University of New York, 2800 Victory Blvd., Staten Island, NY 10314, USA; (R.V.S.); (L.S.C.); (P.W.); (J.D.A.)
| | - Ping Wang
- Department of Chemistry, College of Staten Island, University of New York, 2800 Victory Blvd., Staten Island, NY 10314, USA; (R.V.S.); (L.S.C.); (P.W.); (J.D.A.)
| | - Joekeem D. Arizala
- Department of Chemistry, College of Staten Island, University of New York, 2800 Victory Blvd., Staten Island, NY 10314, USA; (R.V.S.); (L.S.C.); (P.W.); (J.D.A.)
- The Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Sébastien F. Poget
- Department of Chemistry, College of Staten Island, University of New York, 2800 Victory Blvd., Staten Island, NY 10314, USA; (R.V.S.); (L.S.C.); (P.W.); (J.D.A.)
- The Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- The Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- Correspondence:
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Matsumura K, Yokogawa M, Osawa M. Peptide Toxins Targeting KV Channels. Handb Exp Pharmacol 2021; 267:481-505. [PMID: 34117930 DOI: 10.1007/164_2021_500] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
A number of peptide toxins isolated from animals target potassium ion (K+) channels. Many of them are particularly known to inhibit voltage-gated K+ (KV) channels and are mainly classified into pore-blocking toxins or gating-modifier toxins. Pore-blocking toxins directly bind to the ion permeation pores of KV channels, thereby physically occluding them. In contrast, gating-modifier toxins bind to the voltage-sensor domains of KV channels, modulating their voltage-dependent conformational changes. These peptide toxins are useful molecular tools in revealing the structure-function relationship of KV channels and have potential for novel treatments for diseases related to KV channels. This review focuses on the inhibition mechanism of pore-blocking and gating-modifier toxins that target KV channels.
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Affiliation(s)
- Kazuki Matsumura
- Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
| | - Mariko Yokogawa
- Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan
| | - Masanori Osawa
- Graduate School of Pharmaceutical Sciences, Keio University, Tokyo, Japan.
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3
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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: 31] [Impact Index Per Article: 10.3] [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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Cardoso FC, Castro J, Grundy L, Schober G, Garcia-Caraballo S, Zhao T, Herzig V, King GF, Brierley SM, Lewis RJ. A spider-venom peptide with multitarget activity on sodium and calcium channels alleviates chronic visceral pain in a model of irritable bowel syndrome. Pain 2021; 162:569-581. [PMID: 32826759 DOI: 10.1097/j.pain.0000000000002041] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 08/04/2020] [Indexed: 12/19/2022]
Abstract
ABSTRACT Chronic pain is a serious debilitating condition that affects ∼20% of the world's population. Currently available drugs fail to produce effective pain relief in many patients and have dose-limiting side effects. Several voltage-gated sodium (NaV) and calcium (CaV) channels are implicated in the etiology of chronic pain, particularly NaV1.1, NaV1.3, NaV1.7-NaV1.9, CaV2.2, and CaV3.2. Numerous NaV and CaV modulators have been described, but with few exceptions, they display poor potency and/or selectivity for pain-related channel subtypes. Here, we report the discovery and characterization of 2 novel tarantula-venom peptides (Tap1a and Tap2a) isolated from Theraphosa apophysis venom that modulate the activity of both NaV and CaV3 channels. Tap1a and Tap2a inhibited on-target NaV and CaV3 channels at nanomolar to micromolar concentrations and displayed moderate off-target selectivity for NaV1.6 and weak affinity for NaV1.4 and NaV1.5. The most potent inhibitor, Tap1a, nearly ablated neuronal mechanosensitivity in afferent fibers innervating the colon and the bladder, with in vivo intracolonic administration reversing colonic mechanical hypersensitivity in a mouse model of irritable bowel syndrome. These findings suggest that targeting a specific combination of NaV and CaV3 subtypes provides a novel route for treatment of chronic visceral pain.
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Affiliation(s)
- Fernanda C Cardoso
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Joel Castro
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Luke Grundy
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Gudrun Schober
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Sonia Garcia-Caraballo
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Tianjiao Zhao
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Volker Herzig
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
- School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland, Australia
| | - Glenn F King
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, College of Medicine and Public Health, Flinders Health and Medical Research Institute, Flinders University, South Australia, Australia
- Hopwood Centre for Neurobiology, Lifelong Health Theme, South Australian Health and Medical Research Institute (SAHMRI), North Terrace, Adelaide, South Australia, Australia
| | - Richard J Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
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Armstrong DA, Jin AH, Braga Emidio N, Lewis RJ, Alewood PF, Rosengren KJ. Chemical Synthesis and NMR Solution Structure of Conotoxin GXIA from Conus geographus. Mar Drugs 2021; 19:md19020060. [PMID: 33530397 PMCID: PMC7912261 DOI: 10.3390/md19020060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/07/2021] [Accepted: 01/19/2021] [Indexed: 12/30/2022] Open
Abstract
Conotoxins are disulfide-rich peptides found in the venom of cone snails. Due to their exquisite potency and high selectivity for a wide range of voltage and ligand gated ion channels they are attractive drug leads in neuropharmacology. Recently, cone snails were found to have the capability to rapidly switch between venom types with different proteome profiles in response to predatory or defensive stimuli. A novel conotoxin, GXIA (original name G117), belonging to the I3-subfamily was identified as the major component of the predatory venom of piscivorous Conus geographus. Using 2D solution NMR spectroscopy techniques, we resolved the 3D structure for GXIA, the first structure reported for the I3-subfamily and framework XI family. The 32 amino acid peptide is comprised of eight cysteine residues with the resultant disulfide connectivity forming an ICK+1 motif. With a triple stranded β-sheet, the GXIA backbone shows striking similarity to several tarantula toxins targeting the voltage sensor of voltage gated potassium and sodium channels. Supported by an amphipathic surface, the structural evidence suggests that GXIA is able to embed in the membrane and bind to the voltage sensor domain of a putative ion channel target.
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Affiliation(s)
- David A. Armstrong
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD 4072, Australia;
| | - Ai-Hua Jin
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (A.-H.J.); (N.B.E.); (R.J.L.); (P.F.A.)
| | - Nayara Braga Emidio
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (A.-H.J.); (N.B.E.); (R.J.L.); (P.F.A.)
| | - Richard J. Lewis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (A.-H.J.); (N.B.E.); (R.J.L.); (P.F.A.)
| | - Paul F. Alewood
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia; (A.-H.J.); (N.B.E.); (R.J.L.); (P.F.A.)
| | - K. Johan Rosengren
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD 4072, Australia;
- Correspondence:
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Montandon GG, Cassoli JS, Peigneur S, Verano-Braga T, Santos DMD, Paiva ALB, Moraes ÉRD, Kushmerick C, Borges MH, Richardson M, Pimenta AMDC, Kjeldsen F, Diniz MRV, Tytgat J, Lima MED. GiTx1(β/κ-theraphotoxin-Gi1a), a novel toxin from the venom of Brazilian tarantula Grammostola iheringi (Mygalomorphae, Theraphosidae): Isolation, structural assessments and activity on voltage-gated ion channels. Biochimie 2020; 176:138-149. [PMID: 32717411 DOI: 10.1016/j.biochi.2020.07.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 06/30/2020] [Accepted: 07/08/2020] [Indexed: 12/14/2022]
Abstract
Spider venoms, despite their toxicity, represent rich sources of pharmacologically active compounds with biotechnological potential. However, in view of the large diversity of the spider species, the full potential of their venom molecules is still far from being known. In this work, we report the purification and structural and functional characterization of GiTx1 (β/κ-TRTX-Gi1a), the first toxin purified from the venom of the Brazilian tarantula spider Grammostola iheringi. GiTx1 was purified by chromatography, completely sequenced through automated Edman degradation and tandem mass spectrometry and its structure was predicted by molecular modeling. GiTx1 has a MW of 3.585 Da, with the following amino acid sequence: SCQKWMWTCDQKRPCCEDMVCKLWCKIIK. Pharmacological activity of GiTx1 was characterized by electrophysiology using whole-cell patch clamp on dorsal root ganglia neurons (DRG) and two-electrode voltage-clamp on voltage-gated sodium and potassium channels subtypes expressed in Xenopus laevis oocytes. GiTx1, at 2 μM, caused a partial block of inward (∼40%) and outward (∼20%) currents in DRG cells, blocked rNav1.2, rNav1.4 and mNav1.6 and had a significant effect on VdNav, an arachnid sodium channel isoform. IC50 values of 156.39 ± 14.90 nM for Nav1.6 and 124.05 ± 12.99 nM for VdNav, were obtained. In addition, this toxin was active on rKv4.3 and hERG potassium channels, but not Shaker IR or rKv2.1 potassium channels. In summary, GiTx1 is a promiscuous toxin with multiple effects on different types of ion channels.
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Affiliation(s)
- Gabriela Gontijo Montandon
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
| | - Juliana Silva Cassoli
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil; Pharmacology and Toxicology, University of Leuven (KULeuven) - Campus Gasthuisberg, PO Box 922, Herestraat 49, 3000, Leuven, Belgium
| | - Steve Peigneur
- Pharmacology and Toxicology, University of Leuven (KULeuven) - Campus Gasthuisberg, PO Box 922, Herestraat 49, 3000, Leuven, Belgium
| | - Thiago Verano-Braga
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil; Protein Research Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Daniel Moreira Dos Santos
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
| | - Ana Luiza Bittencourt Paiva
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Rua Conde Pereira Carneiro 80, 30510-010, Belo Horizonte, MG, Brazil
| | - Éder Ricardo de Moraes
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
| | - Christopher Kushmerick
- Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
| | - Márcia Helena Borges
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Rua Conde Pereira Carneiro 80, 30510-010, Belo Horizonte, MG, Brazil
| | - Michael Richardson
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Rua Conde Pereira Carneiro 80, 30510-010, Belo Horizonte, MG, Brazil
| | - Adriano Monteiro de Castro Pimenta
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil
| | - Frank Kjeldsen
- Protein Research Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - Marcelo Ribeiro Vasconcelos Diniz
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias, Rua Conde Pereira Carneiro 80, 30510-010, Belo Horizonte, MG, Brazil
| | - Jan Tytgat
- Pharmacology and Toxicology, University of Leuven (KULeuven) - Campus Gasthuisberg, PO Box 922, Herestraat 49, 3000, Leuven, Belgium
| | - Maria Elena de Lima
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais - UFMG, Av. Antônio Carlos 6627, 31270-901, Belo Horizonte, MG, Brazil; Santa Casa de Belo Horizonte, Instituto de Ensino e Pesquisa, Rua Domingos Vieira, 590, 30150-240, Belo Horizonte, MG, Brazil.
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Liu X, Tao J, Zhang S, Lan W, Wang C, Ji Y, Cao C. Selective Blockade of Neuronal BK (α + β4) Channels Preventing Epileptic Seizure. J Med Chem 2019; 63:216-230. [DOI: 10.1021/acs.jmedchem.9b01241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Xinlian Liu
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
- University of Chinese Academy of Science, No. 19A, Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Jie Tao
- Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, 164 Lanxi Road, Putuo District, Shanghai 200062, China
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
| | - Shuzhang Zhang
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
| | - Wenxian Lan
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Chunxi Wang
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Yonghua Ji
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, 99 Shangda Road,
BaoShan District, Shanghai 200444, China
- Xinhua Hospital (Chongming) Affiliated to Shanghai JiaoTong University School of Medicine, Shanghai Chongming Xinhua Translational Medical Institute for Cancer Pain, 25 Nanmen Port Street, Chongming Branch, Shanghai 202150, China
| | - Chunyang Cao
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
- University of Chinese Academy of Science, No. 19A, Yuquan Road, Shijingshan District, Beijing 100049, China
- Institute of Drug Discovery Technology, Ningbo University, No 818 Fenghua Road, Ningbo, Zhejiang 313211, China
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The membrane protein KCNQ1 potassium ion channel: Functional diversity and current structural insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183148. [PMID: 31825788 DOI: 10.1016/j.bbamem.2019.183148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 11/15/2019] [Accepted: 12/04/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND Ion channels play crucial roles in cellular biology, physiology, and communication including sensory perception. Voltage-gated potassium (Kv) channels execute their function by sensor activation, pore-coupling, and pore opening leading to K+ conductance. SCOPE OF REVIEW This review focuses on a voltage-gated K+ ion channel KCNQ1 (Kv 7.1). Firstly, discussing its positioning in the human ion chanome, and the role of KCNQ1 in the multitude of cellular processes. Next, we discuss the overall channel architecture and current structural insights on KCNQ1. Finally, the gating mechanism involving members of the KCNE family and its interaction with non-KCNE partners. MAJOR CONCLUSIONS KCNQ1 executes its important physiological functions via interacting with KCNE1 and non-KCNE1 proteins/molecules: calmodulin, PIP2, PKA. Although, KCNQ1 has been studied in great detail, several aspects of the channel structure and function still remain unexplored. This review emphasizes the structural and biophysical studies of KCNQ1, its interaction with KCNE1 and non-KCNE1 proteins and focuses on several seminal findings showing the role of VSD and the pore domain in the channel activation and gating properties. GENERAL SIGNIFICANCE KCNQ1 mutations can result in channel defects and lead to several diseases including atrial fibrillation and long QT syndrome. Therefore, a thorough structure-function understanding of this channel complex is essential to understand its role in both normal and disease biology. Moreover, unraveling the molecular mechanisms underlying the regulation of this channel complex will help to find therapeutic strategies for several diseases.
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Chen H, Pan J, Gandhi DM, Dockendorff C, Cui Q, Chanda B, Henzler-Wildman KA. NMR Structural Analysis of Isolated Shaker Voltage-Sensing Domain in LPPG Micelles. Biophys J 2019; 117:388-398. [PMID: 31301804 DOI: 10.1016/j.bpj.2019.06.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 06/20/2019] [Indexed: 11/25/2022] Open
Abstract
The voltage-sensing domain (VSD) is a conserved structural module that regulates the gating of voltage-dependent ion channels in response to a change in membrane potential. Although the structures of many VSD-containing ion channels are now available, our understanding of the structural dynamics associated with gating transitions remains limited. To probe dynamics with site-specific resolution, we utilized NMR spectroscopy to characterize the VSD derived from Shaker potassium channel in 1-palmitoyl-2-hydroxy-sn-glycero-3-phospho-(1'-rac-glycerol) (LPPG) micelles. The backbone dihedral angles predicted based on secondary chemical shifts using torsion angle likeliness obtained from shift (TALOS+) showed that the Shaker-VSD shares many structural features with the homologous Kv1.2/2.1 chimera, including a transition from α-helix to 310 helix in the C-terminal portion of the fourth transmembrane helix. Nevertheless, there are clear differences between the Shaker-VSD and Kv1.2/2.1 chimera in the S2-S3 linker and S3 transmembrane region, where the organization of secondary structure elements in Shaker-VSD appears to more closely resemble the KvAP-VSD. Comparison of microsecond-long molecular dynamics simulations of Kv 1.2-VSD in LPPG micelles and a 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) bilayer showed that LPPG micelles do not induce significant structural distortion in the isolated voltage sensor. To assess the integrity of the tertiary fold, we directly probed the binding of BrMT analog 2-[2-({[3-(2-amino-ethyl)-6-bromo-1H-indol-2-yl]methoxy}k7methyl)-6-bromo-1H-indol-3-yl]ethan-1-amine (BrET), a gating modifier toxin, and identified the location of the putative binding site. Our results suggest that the Shaker-VSD in LPPG micelles is in a native-like fold and is likely to provide valuable insights into the dynamics of voltage-gating and its regulation.
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Affiliation(s)
- Hongbo Chen
- Graduate Program in Biophysics, Madison, Wisconsin; Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin
| | - Junkun Pan
- Department of Neuroscience, Madison, Wisconsin; Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin
| | - Disha M Gandhi
- Departments of Chemistry, Marquette University, Milwaukee, Wisconsin
| | - Chris Dockendorff
- Departments of Chemistry, Marquette University, Milwaukee, Wisconsin
| | - Qiang Cui
- Departments of Chemistry, Physics, Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Baron Chanda
- Graduate Program in Biophysics, Madison, Wisconsin; Department of Neuroscience, Madison, Wisconsin; Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin.
| | - Katherine A Henzler-Wildman
- Graduate Program in Biophysics, Madison, Wisconsin; Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin.
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Li H, Xu J, Shen ZS, Wang GM, Tang M, Du XR, Lv YT, Wang JJ, Zhang FF, Qi Z, Zhang Z, Sokabe M, Tang QY. The neuropeptide GsMTx4 inhibits a mechanosensitive BK channel through the voltage-dependent modification specific to mechano-gating. J Biol Chem 2019; 294:11892-11909. [PMID: 31201274 DOI: 10.1074/jbc.ra118.005511] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 06/06/2019] [Indexed: 12/12/2022] Open
Abstract
The cardiac mechanosensitive BK (Slo1) channels are gated by Ca2+, voltage, and membrane stretch. The neuropeptide GsMTx4 is a selective inhibitor of mechanosensitive (MS) channels. It has been reported to suppress stretch-induced cardiac fibrillation in the heart, but the mechanism underlying the specificity and even the targeting channel(s) in the heart remain elusive. Here, we report that GsMTx4 inhibits a stretch-activated BK channel (SAKcaC) in the heart through a modulation specific to mechano-gating. We show that membrane stretching increases while GsMTx4 decreases the open probability (P o) of SAKcaC. These effects were mostly abolished by the deletion of the STREX axis-regulated (STREX) exon located between RCK1 and RCK2 domains in BK channels. Single-channel kinetics analysis revealed that membrane stretch activates SAKcaC by prolonging the open-time duration (τO) and shortening the closed-time constant (τC). In contrast, GsMTx4 reversed the effects of membrane stretch, suggesting that GsMTx4 inhibits SAKcaC activity by interfering with mechano-gating of the channel. Moreover, GsMTx4 exerted stronger efficacy on SAKcaC under membrane-hyperpolarized/resting conditions. Molecular dynamics simulation study revealed that GsMTx4 appeared to have the ability to penetrate deeply within the bilayer, thus generating strong membrane deformation under the hyperpolarizing/resting conditions. Immunostaining results indicate that BK variants containing STREX are also expressed in mouse ventricular cardiomyocytes. Our results provide common mechanisms of peptide actions on MS channels and may give clues to therapeutic suppression of cardiac arrhythmias caused by excitatory currents through MS channels under hyper-mechanical stress in the heart.
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Affiliation(s)
- Hui Li
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Jie Xu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Zhong-Shan Shen
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Guang-Ming Wang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Mingxi Tang
- Department of Pathology, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province 646000, China
| | - Xiang-Rong Du
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Yan-Tian Lv
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Jing-Jing Wang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Fei-Fei Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Zhi Qi
- Department of Basic Medical Sciences, Medical College of Xiamen University, Xiamen 361102, China
| | - Zhe Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China
| | - Masahiro Sokabe
- ICORP Cell Mechanosensing, Japan Science and Technology Agency, Nagoya 466-8550, Japan .,Mechanobiology Laboratory, Nagoya University, Graduate School of Medicine, Nagoya 466-8550, Japan.,Department of Physiology, Nagoya University, Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Qiong-Yao Tang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province 221004, China .,ICORP Cell Mechanosensing, Japan Science and Technology Agency, Nagoya 466-8550, Japan
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11
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Dixit G, Sahu ID, Reynolds WD, Wadsworth TM, Harding BD, Jaycox CK, Dabney-Smith C, Sanders CR, Lorigan GA. Probing the Dynamics and Structural Topology of the Reconstituted Human KCNQ1 Voltage Sensor Domain (Q1-VSD) in Lipid Bilayers Using Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2019; 58:965-973. [PMID: 30620191 DOI: 10.1021/acs.biochem.8b01042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
KCNQ1 (Kv7.1 or KvLQT1) is a potassium ion channel protein found in the heart, ear, and other tissues. In complex with the KCNE1 accessory protein, it plays a role during the repolarization phase of the cardiac action potential. Mutations in the channel have been associated with several diseases, including congenital deafness and long QT syndrome. Nuclear magnetic resonance (NMR) structural studies in detergent micelles and a cryo-electron microscopy structure of KCNQ1 from Xenopus laevis have shown that the voltage sensor domain (Q1-VSD) of the channel has four transmembrane helices, S1-S4, being overall structurally similar with other VSDs. In this study, we describe a reliable method for the reconstitution of Q1-VSD into (POPC/POPG) lipid bilayer vesicles. Site-directed spin labeling electron paramagnetic resonance spectroscopy was used to probe the structural dynamics and topology of several residues of Q1-VSD in POPC/POPG lipid bilayer vesicles. Several mutants were probed to determine their location and corresponding immersion depth (in angstroms) with respect to the membrane. The dynamics of the bilayer vesicles upon incorporation of Q1-VSD were studied using 31P solid-state NMR spectroscopy by varying the protein:lipid molar ratios confirming the interaction of the protein with the bilayer vesicles. Circular dichroism spectroscopic data showed that the α-helical content of Q1-VSD is higher for the protein reconstituted in vesicles than in previous studies using DPC detergent micelles. This study provides insight into the structural topology and dynamics of Q1-VSD reconstituted in a lipid bilayer environment, forming the basis for more advanced structural and functional studies.
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Affiliation(s)
- Gunjan Dixit
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Indra D Sahu
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Warren D Reynolds
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Tessa M Wadsworth
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Benjamin D Harding
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Colleen K Jaycox
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology , Vanderbilt University , Nashville , Tennessee 37240 , United States
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
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12
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Tilley DC, Angueyra JM, Eum KS, Kim H, Chao LH, Peng AW, Sack JT. The tarantula toxin GxTx detains K + channel gating charges in their resting conformation. J Gen Physiol 2018; 151:292-315. [PMID: 30397012 PMCID: PMC6400525 DOI: 10.1085/jgp.201812213] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 10/01/2018] [Indexed: 11/20/2022] Open
Abstract
Allosteric ligands modulate protein activity by altering the energy landscape of conformational space in ligand-protein complexes. Here we investigate how ligand binding to a K+ channel's voltage sensor allosterically modulates opening of its K+-conductive pore. The tarantula venom peptide guangxitoxin-1E (GxTx) binds to the voltage sensors of the rat voltage-gated K+ (Kv) channel Kv2.1 and acts as a partial inverse agonist. When bound to GxTx, Kv2.1 activates more slowly, deactivates more rapidly, and requires more positive voltage to reach the same K+-conductance as the unbound channel. Further, activation kinetics are more sigmoidal, indicating that multiple conformational changes coupled to opening are modulated. Single-channel current amplitudes reveal that each channel opens to full conductance when GxTx is bound. Inhibition of Kv2.1 channels by GxTx results from decreased open probability due to increased occurrence of long-lived closed states; the time constant of the final pore opening step itself is not impacted by GxTx. When intracellular potential is less than 0 mV, GxTx traps the gating charges on Kv2.1's voltage sensors in their most intracellular position. Gating charges translocate at positive voltages, however, indicating that GxTx stabilizes the most intracellular conformation of the voltage sensors (their resting conformation). Kinetic modeling suggests a modulatory mechanism: GxTx reduces the probability of voltage sensors activating, giving the pore opening step less frequent opportunities to occur. This mechanism results in K+-conductance activation kinetics that are voltage-dependent, even if pore opening (the rate-limiting step) has no inherent voltage dependence. We conclude that GxTx stabilizes voltage sensors in a resting conformation, and inhibits K+ currents by limiting opportunities for the channel pore to open, but has little, if any, direct effect on the microscopic kinetics of pore opening. The impact of GxTx on channel gating suggests that Kv2.1's pore opening step does not involve movement of its voltage sensors.
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Affiliation(s)
- Drew C Tilley
- Department of Physiology & Membrane Biology, University of California, Davis, Davis, CA
| | - Juan M Angueyra
- Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA
| | - Kenneth S Eum
- Department of Physiology & Membrane Biology, University of California, Davis, Davis, CA.,Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA
| | - Heesoo Kim
- Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA
| | - Luke H Chao
- Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA
| | - Anthony W Peng
- Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA
| | - Jon T Sack
- Department of Physiology & Membrane Biology, University of California, Davis, Davis, CA .,Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA
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13
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Polido G, Shi X, Xu D, Guo C, Thai R, Patterson JP, Gianneschi NC, Suchyna TM, Sachs F, Holland GP. Investigating the interaction of Grammostola rosea venom peptides and model lipid bilayers with solid-state NMR and electron microscopy techniques. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:151-160. [PMID: 30463698 DOI: 10.1016/j.bbamem.2018.08.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 07/19/2018] [Accepted: 08/07/2018] [Indexed: 10/28/2022]
Abstract
Spider venom contains a number of small peptides that can control the gating properties of a wide range of ion channels with high affinity and specificity. These ion channels are responsible for coordination and control of many bodily functions such as transducing signals into sensory functions, smooth muscle contractions as well as serving as sensors in volume regulation. Hence, these peptides have been the topic of many research efforts in hopes that they can be used as biomedical therapeutics. Several peptides are known to control the gating properties of ion channels by involving the lipid membrane. GsMTx4, originally isolated from the Chilean Rose tarantula (Grammostola rosea), is known to selectively inhibit mechanosensitive ion channels by partitioning into the lipid bilayer. To further understand this indirect gating mechanism, we investigated the interactions between native GsAF2, VsTx1 and a synthetic form of GsMTx4 with model DMPC lipid bilayers using 31P solid-state NMR, 13C CP-MAS NMR, NS-TEM and cryo-TEM. The results reveal that these inhibitor cystine knot peptides perforate the DMPC lipid vesicles similarly with some subtle differences and ultimately create small spherical vesicles and anisotropic cylindrical and discoidal vesicles at concentrations near 1.0-1.5 mol% peptide. The anisotropic components align with their long axes along the NMR static B0 magnetic field, a property that should be useful in future NMR structural investigations of these systems. These findings move us forward in our understanding of how these peptides bind and interact with the lipid bilayer.
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Affiliation(s)
- Geraldine Polido
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA
| | - Xiangyan Shi
- Department of Chemistry and Biochemistry, Magnetic Resonance Research Center, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Dian Xu
- Department of Chemistry and Biochemistry, Magnetic Resonance Research Center, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Chengchen Guo
- Department of Chemistry and Biochemistry, Magnetic Resonance Research Center, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Rich Thai
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA
| | - Joseph P Patterson
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92037, USA
| | - Nathan C Gianneschi
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92037, USA
| | - Thomas M Suchyna
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
| | - Frederick Sachs
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
| | - Gregory P Holland
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 92182-1030, USA.
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14
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Oz M, El Nebrisi EG, Yang KHS, Howarth FC, Al Kury LT. Cellular and Molecular Targets of Menthol Actions. Front Pharmacol 2017; 8:472. [PMID: 28769802 PMCID: PMC5513973 DOI: 10.3389/fphar.2017.00472] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/03/2017] [Indexed: 02/04/2023] Open
Abstract
Menthol belongs to monoterpene class of a structurally diverse group of phytochemicals found in plant-derived essential oils. Menthol is widely used in pharmaceuticals, confectionary, oral hygiene products, pesticides, cosmetics, and as a flavoring agent. In addition, menthol is known to have antioxidant, anti-inflammatory, and analgesic effects. Recently, there has been renewed awareness in comprehending the biological and pharmacological effects of menthol. TRP channels have been demonstrated to mediate the cooling actions of menthol. There has been new evidence demonstrating that menthol can significantly influence the functional characteristics of a number of different kinds of ligand and voltage-gated ion channels, indicating that at least some of the biological and pharmacological effects of menthol can be mediated by alterations in cellular excitability. In this article, we examine the results of earlier studies on the actions of menthol with voltage and ligand-gated ion channels.
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Affiliation(s)
- Murat Oz
- Department of Pharmacology, College of Medicine and Health Sciences, United Arab Emirates UniversityAl Ain, United Arab Emirates.,Department of Basic Medical Sciences, College of Medicine, Qatar UniversityDoha, Qatar
| | - Eslam G El Nebrisi
- Department of Pharmacology, College of Medicine and Health Sciences, United Arab Emirates UniversityAl Ain, United Arab Emirates
| | - Keun-Hang S Yang
- Department of Biological Sciences, Schmid College of Science and Technology, Chapman UniversityOrange, CA, United States
| | - Frank C Howarth
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates UniversityAl Ain, United Arab Emirates
| | - Lina T Al Kury
- Department of Health Sciences, College of Natural and Health Sciences, Zayed UniversityAbu Dhabi, United Arab Emirates
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15
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Hsieh MH, Shiau YS, Liou HH, Jeng US, Lee MT, Lou KL. Measurement of Hanatoxin-Induced Membrane Thinning with Lamellar X-ray Diffraction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:2885-2889. [PMID: 28260386 DOI: 10.1021/acs.langmuir.7b00064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Membrane perturbation induced by cysteine-rich peptides is a crucial biological phenomenon but scarcely investigated, in particular with effective biophysical-chemical methodologies. Hanatoxin (HaTx), a 35-residue polypeptide from spider venom, works as an inhibitor of drk1 (Kv2.1) channels, most likely by interacting with the voltage-sensor. However, how this water-soluble peptide modifies the gating remains poorly understood, as the voltage sensor was proposed to be deeply embedded within the bilayer. To see how HaTx interacts with phospholipid bilayers, we observe the toxin-induced perturbation on POPC/DOPG-membranes through measurements of the change in membrane thickness. Lamellar X-ray diffraction (LXD) was applied on stacked planar bilayers in the near-fully hydrated state. The results provide quantitative evidence for the membrane thinning in a concentration-dependent manner, leading to novel and direct combinatory approaches by discovering how to investigate such a biologically relevant interaction between gating-modifier toxins and phospholipid bilayers.
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Affiliation(s)
- Meng-Hsuan Hsieh
- Institute of Biotechnology, National Taiwan University , Taipei 10672, Taiwan
| | - Yu-Shuan Shiau
- Membrane Protein Research Core, Center for Biotechnology, National Taiwan University , Taipei 10672, Taiwan
| | - Horng-Huei Liou
- Division of Neurology, National Taiwan University Hospital , Taipei 10002, Taiwan
- Institute of Pharmacology, National Taiwan University , Taipei 10051, Taiwan
| | - U-Ser Jeng
- National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan
| | - Ming-Tao Lee
- National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan
- Department of Physics, National Central University , Jhongli 32001, Taiwan
| | - Kuo-Long Lou
- Institute of Biotechnology, National Taiwan University , Taipei 10672, Taiwan
- Membrane Protein Research Core, Center for Biotechnology, National Taiwan University , Taipei 10672, Taiwan
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16
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Hanatoxin inserts into phospholipid membranes without pore formation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:917-923. [PMID: 28143758 DOI: 10.1016/j.bbamem.2017.01.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 01/21/2017] [Accepted: 01/26/2017] [Indexed: 11/23/2022]
Abstract
Hanatoxin (HaTx), a 35-residue polypeptide from spider venom, functions as an inhibitor of Kv2.1 channels by interacting with phospholipids prior to affecting the voltage-sensor. However, how this water-soluble peptide modifies the gating remains poorly understood, as the voltage-sensor is deeply embedded within the bilayer. To determine how HaTx interacts with phospholipid bilayers, in this study, we examined the toxin-induced partitioning of liposomal membranes. HPLC-results from high-speed spin-down vesicles with HaTx demonstrated direct binding. Dynamic light scattering (DLS) and leakage assay results further indicated that neither membrane pores nor membrane fragmentations were observed in the presence of HaTx. To clarify the binding details, Langmuir trough experiments were performed with phospholipid monolayers by mimicking the external leaflet of membrane bilayers, indicating the involvement of acyl chains in such interactions between HaTx and phospholipids. Our current study thus describes the interaction pattern of HaTx with vesicle membranes, defining a membrane-partitioning mechanism for peptide insertion involving the membrane hydrocarbon core without pore formation.
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17
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Lau CHY, King GF, Mobli M. Molecular basis of the interaction between gating modifier spider toxins and the voltage sensor of voltage-gated ion channels. Sci Rep 2016; 6:34333. [PMID: 27677715 PMCID: PMC5039624 DOI: 10.1038/srep34333] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 09/12/2016] [Indexed: 01/02/2023] Open
Abstract
Voltage-sensor domains (VSDs) are modular transmembrane domains of voltage-gated ion channels that respond to changes in membrane potential by undergoing conformational changes that are coupled to gating of the ion-conducting pore. Most spider-venom peptides function as gating modifiers by binding to the VSDs of voltage-gated channels and trapping them in a closed or open state. To understand the molecular basis underlying this mode of action, we used nuclear magnetic resonance to delineate the atomic details of the interaction between the VSD of the voltage-gated potassium channel KvAP and the spider-venom peptide VSTx1. Our data reveal that the toxin interacts with residues in an aqueous cleft formed between the extracellular S1-S2 and S3-S4 loops of the VSD whilst maintaining lipid interactions in the gaps formed between the S1-S4 and S2-S3 helices. The resulting network of interactions increases the energetic barrier to the conformational changes required for channel gating, and we propose that this is the mechanism by which gating modifier toxins inhibit voltage-gated ion channels.
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Affiliation(s)
- Carus H Y Lau
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, QLD 4072, Australia
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18
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Salari A, Vega BS, Milescu LS, Milescu M. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels. Sci Rep 2016; 6:23894. [PMID: 27045173 PMCID: PMC4820701 DOI: 10.1038/srep23894] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/16/2016] [Indexed: 01/26/2023] Open
Abstract
Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b–S4 “paddle motif,” which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple toxin binding sites. We show here that the S3–S4 segments within Cav3.1 can be transplanted into Kv2.1 to examine their individual contributions to voltage sensing and pharmacology. With these results, we now have a more complete picture of the conserved nature of the paddle motif in all three major voltage-gated ion channel types (Kv, Nav, and Cav). When screened with tarantula toxins, the four paddle sequences display distinct toxin binding properties, demonstrating that gating-modifier toxins can bind to Cav channels in a domain specific fashion. Domain III was the most commonly and strongly targeted, and mutagenesis revealed an acidic residue that is important for toxin binding. We also measured the lipid partitioning strength of all toxins tested and observed a positive correlation with their inhibition of Cav3.1, suggesting a key role for membrane partitioning.
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Affiliation(s)
- Autoosa Salari
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Benjamin S Vega
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Lorin S Milescu
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Mirela Milescu
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
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19
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Beurg M, Kim KX, Fettiplace R. Conductance and block of hair-cell mechanotransducer channels in transmembrane channel-like protein mutants. ACTA ACUST UNITED AC 2015; 144:55-69. [PMID: 24981230 PMCID: PMC4076520 DOI: 10.1085/jgp.201411173] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Proteins other than TMC1 and TMC2 must contribute to the pore of the mechanotransducer channel of cochlear hair cells; an external vestibule subject to disruption in Tmc mutants may influence the channel’s properties. Transmembrane channel–like (TMC) proteins TMC1 and TMC2 are crucial to the function of the mechanotransducer (MT) channel of inner ear hair cells, but their precise function has been controversial. To provide more insight, we characterized single MT channels in cochlear hair cells from wild-type mice and mice with mutations in Tmc1, Tmc2, or both. Channels were recorded in whole-cell mode after tip link destruction with BAPTA or after attenuating the MT current with GsMTx-4, a peptide toxin we found to block the channels with high affinity. In both cases, the MT channels in outer hair cells (OHCs) of wild-type mice displayed a tonotopic gradient in conductance, with channels from the cochlear base having a conductance (110 pS) nearly twice that of those at the apex (62 pS). This gradient was absent, with channels at both cochlear locations having similar small conductances, with two different Tmc1 mutations. The conductance of MT channels in inner hair cells was invariant with cochlear location but, as in OHCs, was reduced in either Tmc1 mutant. The gradient of OHC conductance also disappeared in Tmc1/Tmc2 double mutants, in which a mechanically sensitive current could be activated by anomalous negative displacements of the hair bundle. This “reversed stimulus–polarity” current was seen with two different Tmc1/Tmc2 double mutants, and with Tmc1/Tmc2/Tmc3 triple mutants, and had a pharmacological sensitivity comparable to that of native MT currents for most antagonists, except dihydrostreptomycin, for which the affinity was less, and for curare, which exhibited incomplete block. The existence in the Tmc1/Tmc2 double mutants of MT channels with most properties resembling those of wild-type channels indicates that proteins other than TMCs must be part of the channel pore. We suggest that an external vestibule of the MT channel may partly account for the channel’s large unitary conductance, high Ca2+ permeability, and pharmacological profile, and that this vestibule is disrupted in Tmc mutants.
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Affiliation(s)
- Maryline Beurg
- Department of Neuroscience, University of Wisconsin Medical School, Madison, WI 53706
| | - Kyunghee X Kim
- Department of Neuroscience, University of Wisconsin Medical School, Madison, WI 53706
| | - Robert Fettiplace
- Department of Neuroscience, University of Wisconsin Medical School, Madison, WI 53706
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20
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Ozawa SI, Kimura T, Nozaki T, Harada H, Shimada I, Osawa M. Structural basis for the inhibition of voltage-dependent K+ channel by gating modifier toxin. Sci Rep 2015; 5:14226. [PMID: 26382304 PMCID: PMC4585561 DOI: 10.1038/srep14226] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 08/20/2015] [Indexed: 01/24/2023] Open
Abstract
Voltage-dependent K+ (Kv) channels play crucial roles in nerve and muscle action potentials. Voltage-sensing domains (VSDs) of Kv channels sense changes in the transmembrane potential, regulating the K+-permeability across the membrane. Gating modifier toxins, which have been used for the functional analyses of Kv channels, inhibit Kv channels by binding to VSD. However, the structural basis for the inhibition remains elusive. Here, fluorescence and NMR analyses of the interaction between VSD derived from KvAP channel and its gating modifier toxin, VSTx1, indicate that VSTx1 recognizes VSD under depolarized condition. We identified the VSD-binding residues of VSTx1 and their proximal residues of VSD by the cross-saturation (CS) and amino acid selective CS experiments, which enabled to build a docking model of the complex. These results provide structural basis for the specific binding and inhibition of Kv channels by gating modifier toxins.
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Affiliation(s)
- Shin-ichiro Ozawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tomomi Kimura
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tomohiro Nozaki
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hitomi Harada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ichio Shimada
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masanori Osawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.,Keio University Faculty of Pharmacy, Shibakoen, Minato-ku, Tokyo 105-8512, Japan
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21
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Effects of monoterpenes on ion channels of excitable cells. Pharmacol Ther 2015; 152:83-97. [PMID: 25956464 DOI: 10.1016/j.pharmthera.2015.05.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 04/23/2015] [Indexed: 11/20/2022]
Abstract
Monoterpenes are a structurally diverse group of phytochemicals and a major constituent of plant-derived 'essential oils'. Monoterpenes such as menthol, carvacrol, and eugenol have been utilized for therapeutical purposes and food additives for centuries and have been reported to have anti-inflammatory, antioxidant and analgesic actions. In recent years there has been increasing interest in understanding the pharmacological actions of these molecules. There is evidence indicating that monoterpenes can modulate the functional properties of several types of voltage and ligand-gated ion channels, suggesting that some of their pharmacological actions may be mediated by modulations of ion channel function. In this report, we review the literature concerning the interaction of monoterpenes with various ion channels.
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22
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Klint JK, Smith JJ, Vetter I, Rupasinghe DB, Er SY, Senff S, Herzig V, Mobli M, Lewis RJ, Bosmans F, King GF. Seven novel modulators of the analgesic target NaV 1.7 uncovered using a high-throughput venom-based discovery approach. Br J Pharmacol 2015; 172:2445-58. [PMID: 25754331 DOI: 10.1111/bph.13081] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 11/08/2014] [Accepted: 12/08/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Chronic pain is a serious worldwide health issue, with current analgesics having limited efficacy and dose-limiting side effects. Humans with loss-of-function mutations in the voltage-gated sodium channel NaV 1.7 (hNaV 1.7) are indifferent to pain, making hNaV 1.7 a promising target for analgesic development. Since spider venoms are replete with NaV channel modulators, we examined their potential as a source of hNaV 1.7 inhibitors. EXPERIMENTAL APPROACH We developed a high-throughput fluorescent-based assay to screen spider venoms against hNaV 1.7 and isolate 'hit' peptides. To examine the binding site of these peptides, we constructed a panel of chimeric channels in which the S3b-S4 paddle motif from each voltage sensor domain of hNaV 1.7 was transplanted into the homotetrameric KV 2.1 channel. KEY RESULTS We screened 205 spider venoms and found that 40% contain at least one inhibitor of hNaV 1.7. By deconvoluting 'hit' venoms, we discovered seven novel members of the NaSpTx family 1. One of these peptides, Hd1a (peptide μ-TRTX-Hd1a from venom of the spider Haplopelma doriae), inhibited hNaV 1.7 with a high level of selectivity over all other subtypes, except hNaV 1.1. We showed that Hd1a is a gating modifier that inhibits hNaV 1.7 by interacting with the S3b-S4 paddle motif in channel domain II. The structure of Hd1a, determined using heteronuclear NMR, contains an inhibitor cystine knot motif that is likely to confer high levels of chemical, thermal and biological stability. CONCLUSION AND IMPLICATIONS Our data indicate that spider venoms are a rich natural source of hNaV 1.7 inhibitors that might be useful leads for the development of novel analgesics.
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Affiliation(s)
- Julie K Klint
- Centre for Pain Research, Institute for Molecular Bioscience, St. Lucia, Qld, Australia
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23
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Chemoselective tarantula toxins report voltage activation of wild-type ion channels in live cells. Proc Natl Acad Sci U S A 2014; 111:E4789-96. [PMID: 25331865 DOI: 10.1073/pnas.1406876111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Electrically excitable cells, such as neurons, exhibit tremendous diversity in their firing patterns, a consequence of the complex collection of ion channels present in any specific cell. Although numerous methods are capable of measuring cellular electrical signals, understanding which types of ion channels give rise to these signals remains a significant challenge. Here, we describe exogenous probes which use a novel mechanism to report activity of voltage-gated channels. We have synthesized chemoselective derivatives of the tarantula toxin guangxitoxin-1E (GxTX), an inhibitory cystine knot peptide that binds selectively to Kv2-type voltage gated potassium channels. We find that voltage activation of Kv2.1 channels triggers GxTX dissociation, and thus GxTX binding dynamically marks Kv2 activation. We identify GxTX residues that can be replaced by thiol- or alkyne-bearing amino acids, without disrupting toxin folding or activity, and chemoselectively ligate fluorophores or affinity probes to these sites. We find that GxTX-fluorophore conjugates colocalize with Kv2.1 clusters in live cells and are released from channels activated by voltage stimuli. Kv2.1 activation can be detected with concentrations of probe that have a trivial impact on cellular currents. Chemoselective GxTX mutants conjugated to dendrimeric beads likewise bind live cells expressing Kv2.1, and the beads are released by channel activation. These optical sensors of conformational change are prototype probes that can indicate when ion channels contribute to electrical signaling.
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24
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Kalia J, Milescu M, Salvatierra J, Wagner J, Klint JK, King GF, Olivera BM, Bosmans F. From foe to friend: using animal toxins to investigate ion channel function. J Mol Biol 2014; 427:158-175. [PMID: 25088688 DOI: 10.1016/j.jmb.2014.07.027] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/18/2014] [Accepted: 07/18/2014] [Indexed: 12/19/2022]
Abstract
Ion channels are vital contributors to cellular communication in a wide range of organisms, a distinct feature that renders this ubiquitous family of membrane-spanning proteins a prime target for toxins found in animal venom. For many years, the unique properties of these naturally occurring molecules have enabled researchers to probe the structural and functional features of ion channels and to define their physiological roles in normal and diseased tissues. To illustrate their considerable impact on the ion channel field, this review will highlight fundamental insights into toxin-channel interactions and recently developed toxin screening methods and practical applications of engineered toxins.
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Affiliation(s)
- Jeet Kalia
- Indian Institute of Science Education and Research Pune; Pune, Maharashtra 411 008 India
| | - Mirela Milescu
- Division of Biological Sciences; University of Missouri, Columbia, MO 65211 USA
| | - Juan Salvatierra
- Department of Physiology; Johns Hopkins University, School of Medicine, Baltimore, MD 21205 USA
| | - Jordan Wagner
- Department of Physiology; Johns Hopkins University, School of Medicine, Baltimore, MD 21205 USA
| | - Julie K Klint
- Institute for Molecular Bioscience; The University of Queensland, St. Lucia, QLD 4072 Australia
| | - Glenn F King
- Institute for Molecular Bioscience; The University of Queensland, St. Lucia, QLD 4072 Australia
| | | | - Frank Bosmans
- Department of Physiology; Johns Hopkins University, School of Medicine, Baltimore, MD 21205 USA.,Solomon H. Snyder Department of Neuroscience; Johns Hopkins University, School of Medicine, Baltimore, MD 21205 USA
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25
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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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26
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Cherki RS, Kolb E, Langut Y, Tsveyer L, Bajayo N, Meir A. Two tarantula venom peptides as potent and differential NaV channels blockers. Toxicon 2014; 77:58-67. [DOI: 10.1016/j.toxicon.2013.10.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 10/10/2013] [Accepted: 10/29/2013] [Indexed: 10/26/2022]
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27
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González C, Baez-Nieto D, Valencia I, Oyarzún I, Rojas P, Naranjo D, Latorre R. K(+) channels: function-structural overview. Compr Physiol 2013; 2:2087-149. [PMID: 23723034 DOI: 10.1002/cphy.c110047] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Potassium channels are particularly important in determining the shape and duration of the action potential, controlling the membrane potential, modulating hormone secretion, epithelial function and, in the case of those K(+) channels activated by Ca(2+), damping excitatory signals. The multiplicity of roles played by K(+) channels is only possible to their mammoth diversity that includes at present 70 K(+) channels encoding genes in mammals. Today, thanks to the use of cloning, mutagenesis, and the more recent structural studies using x-ray crystallography, we are in a unique position to understand the origins of the enormous diversity of this superfamily of ion channels, the roles they play in different cell types, and the relations that exist between structure and function. With the exception of two-pore K(+) channels that are dimers, voltage-dependent K(+) channels are tetrameric assemblies and share an extremely well conserved pore region, in which the ion-selectivity filter resides. In the present overview, we discuss in the function, localization, and the relations between function and structure of the five different subfamilies of K(+) channels: (a) inward rectifiers, Kir; (b) four transmembrane segments-2 pores, K2P; (c) voltage-gated, Kv; (d) the Slo family; and (e) Ca(2+)-activated SK family, SKCa.
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Affiliation(s)
- Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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28
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Milescu M, Lee HC, Bae CH, Kim JI, Swartz KJ. Opening the shaker K+ channel with hanatoxin. ACTA ACUST UNITED AC 2013; 141:203-16. [PMID: 23359283 PMCID: PMC3557313 DOI: 10.1085/jgp.201210914] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that hanatoxin shifts the conductance–voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin–channel interaction with mutations in the S3b helix of the S1-S4 domain enhances toxin affinity and causes large shifts in the conductance–voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b–S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that the actions of tarantula toxins are not simply a product of where they bind to the channel, but that fine structural details of the toxin–channel interface determine whether a toxin is an inhibitor or opener.
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Affiliation(s)
- Mirela Milescu
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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29
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Binding of hanatoxin to the voltage sensor of Kv2.1. Toxins (Basel) 2012; 4:1552-64. [PMID: 23250329 PMCID: PMC3528262 DOI: 10.3390/toxins4121552] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 12/10/2012] [Accepted: 12/14/2012] [Indexed: 02/06/2023] Open
Abstract
Hanatoxin 1 (HaTx1) is a polypeptide toxin isolated from spider venoms. HaTx1 inhibits the voltage-gated potassium channel kv2.1 potently with nanomolar affinities. Its receptor site has been shown to contain the S3b-S4a paddle of the voltage sensor (VS). Here, the binding of HaTx1 to the VSs of human Kv2.1 in the open and resting states are examined using a molecular docking method and molecular dynamics. Molecular docking calculations predict two distinct binding modes for the VS in the resting state. In the two binding modes, the toxin binds the S3b-S4a from S2 and S3 helices, or from S1 and S4 helices. Both modes are found to be stable when embedded in a lipid bilayer. Only the mode in which the toxin binds the S3b-S4a paddle from S2 and S3 helices is consistent with mutagenesis experiments, and considered to be correct. The toxin is then docked to the VS in the open state, and the toxin-VS interactions are found to be less favorable. Computational mutagenesis calculations performed on F278R and E281K mutant VSs show that the mutations may reduce toxin binding affinity by weakening the non-bonded interactions between the toxin and the VS. Overall, our calculations reproduce a wide range of experimental data, and suggest that HaTx1 binds to the S3b-S4a paddle of Kv2.1 from S2 and S3 helices.
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30
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Structure of the Acid-sensing ion channel 1 in complex with the gating modifier Psalmotoxin 1. Nat Commun 2012; 3:936. [DOI: 10.1038/ncomms1917] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 05/18/2012] [Indexed: 01/13/2023] Open
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31
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Abstract
Piezo ion channels have been found to be essential for mechanical responses in cells. These channels were first shown to exist in Neuro2A cells, and the gene was identified by siRNAs that diminished the mechanical response. Piezo channels are approximately 2500 amino acids long, have between 24-32 transmembrane regions, and appear to assemble into tetramers and require no other proteins for activity. They have a reversal potential around 0 mV and show voltage dependent inactivation. The channel is constitutively active in liposomes, indicating that no cytoskeletal elements are required. Heterologous expression of the Piezo protein can create mechanical sensitivity in otherwise insensitive cells. Piezo1 currents in outside-out patches were blocked by the extracellular MSC inhibitor peptide GsMTx4. Both enantiomeric forms of GsMTx4 inhibited channel activity in a manner similar to endogenous mechanical channels. Piezo1 can adopt a tonic (non-inactivating) form with repeated stimulation. The transition to the non-inactivating form generally occurs in large groups of channels, indicating that the channels exist in domains, and once the domain is compromised, the members simultaneously adopt new properties. Piezo proteins are associated with physiological responses in cells, such as the reaction to noxious stimulus of Drosophila larvae. Recent work measuring cell crowding, shows that Piezo1 is essential for the removal of extra cells without apoptosis. Piezo1 mutations have also been linked to the pathological response of red blood cells in a genetic disease called Xerocytosis. These finding suggest that Piezo1 is a key player in cells' responses to mechanical stimuli.
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32
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Bähring R, Barghaan J, Westermeier R, Wollberg J. Voltage sensor inactivation in potassium channels. Front Pharmacol 2012; 3:100. [PMID: 22654758 PMCID: PMC3358694 DOI: 10.3389/fphar.2012.00100] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 05/04/2012] [Indexed: 12/15/2022] Open
Abstract
In voltage-gated potassium (Kv) channels membrane depolarization causes movement of a voltage sensor domain. This conformational change of the protein is transmitted to the pore domain and eventually leads to pore opening. However, the voltage sensor domain may interact with two distinct gates in the pore domain: the activation gate (A-gate), involving the cytoplasmic S6 bundle crossing, and the pore gate (P-gate), located externally in the selectivity filter. How the voltage sensor moves and how tightly it interacts with these two gates on its way to adopt a relaxed conformation when the membrane is depolarized may critically determine the mode of Kv channel inactivation. In certain Kv channels, voltage sensor movement leads to a tight interaction with the P-gate, which may cause conformational changes that render the selectivity filter non-conductive (“P/C-type inactivation”). Other Kv channels may preferably undergo inactivation from pre-open closed-states during voltage sensor movement, because the voltage sensor temporarily uncouples from the A-gate. For this behavior, known as “preferential” closed-state inactivation, we introduce the term “A/C-type inactivation”. Mechanistically, P/C- and A/C-type inactivation represent two forms of “voltage sensor inactivation.”
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Affiliation(s)
- Robert Bähring
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf Hamburg, Germany
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33
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Park JH, Carlin KP, Wu G, Ilyin VI, Kyle DJ. Cysteine racemization during the Fmoc solid phase peptide synthesis of the Nav1.7-selective peptide - protoxin II. J Pept Sci 2012; 18:442-8. [DOI: 10.1002/psc.2407] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 02/01/2012] [Accepted: 02/17/2012] [Indexed: 12/16/2022]
Affiliation(s)
- Jae H. Park
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Kevin P. Carlin
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Gang Wu
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Victor I. Ilyin
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Donald J. Kyle
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
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34
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Jiménez-Vargas JM, Restano-Cassulini R, Possani LD. Toxin modulators and blockers of hERG K(+) channels. Toxicon 2012; 60:492-501. [PMID: 22497787 DOI: 10.1016/j.toxicon.2012.03.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 03/27/2012] [Indexed: 12/24/2022]
Abstract
The K(+) channel encoded by the Ether-á-go-go-Related Gene (ERG) is expressed in different tissues of different animal species. There are at least three subtypes of this channel, being the sub-type 1 (ERG1) crucial in the repolarization phase of the cardiac action potential. Mutations in this gene can affect the properties of the channel producing the type II long QT syndrome (LQTS2) and many drugs are also known to affect this channel with a similar side effect. Various scorpion, spider and sea anemone toxins affect the ERG currents by blocking the ion-conducting pore from the external side or by modulating channel gating through binding to the voltage-sensor domain. By doing so, these toxins become very useful tools for better understanding the structural and functional characteristics of these ion channels. This review discusses the interaction between the ERG channels and the peptides isolated from venoms of these animals. Special emphasis is placed on scorpion toxins, although the effects of several spider venom toxins and anemone toxins will be also revised.
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Affiliation(s)
- J M Jiménez-Vargas
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Av. Universidad 2001, P.O. Box 501-3, Cuernavaca 62210, Mexico.
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35
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Lipid-dependent gating of a voltage-gated potassium channel. Nat Commun 2011; 2:250. [PMID: 21427721 PMCID: PMC3072105 DOI: 10.1038/ncomms1254] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 02/23/2011] [Indexed: 12/31/2022] Open
Abstract
Recent studies hypothesized that phospholipids stabilize two voltage-sensing arginine residues of certain voltage-gated potassium channels in activated conformations. It remains unclear how lipids directly affect these channels. Here, by examining the conformations of the KvAP in different lipids, we showed that without voltage change, the voltage-sensor domains switched from the activated to the resting state when their surrounding lipids were changed from phospholipids to nonphospholipids. Such lipid-determined conformational change was coupled to the ion-conducting pore, suggesting that parallel to voltage gating, the channel is gated by its annular lipids. Our measurements recognized that the energetic cost of lipid-dependent gating approaches that of voltage gating, but kinetically it appears much slower. Our data support that a channel and its surrounding lipids together constitute a functional unit, and natural nonphospholipids such as cholesterol should exert strong effects on voltage-gated channels. Our first observation of lipid-dependent gating may have general implications to other membrane proteins. Lipid phosphodiesters affect the conformation of certain potassium channels, but the details of the lipid-channel interactions are unclear. Here, the KvAP channel is found to switch from an active to a resting state when the channels are transferred from a phospholipid membrane to a bilayer lacking phosphodiesters.
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36
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Kamaraju K, Gottlieb PA, Sachs F, Sukharev S. Effects of GsMTx4 on bacterial mechanosensitive channels in inside-out patches from giant spheroplasts. Biophys J 2011; 99:2870-8. [PMID: 21044584 DOI: 10.1016/j.bpj.2010.09.022] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 09/07/2010] [Accepted: 09/13/2010] [Indexed: 01/13/2023] Open
Abstract
GsMTx4 is a 34-residue peptide isolated from the tarantula Grammostola spatulata folded into an inhibitory cysteine knot and it selectively affects gating of some mechanosensitive channels. Here we report the effects of cytoplasmic GsMTx4 on the two bacterial channels, MscS and MscL, in giant Escherichia coli spheroplasts. In excised inside-out patches, GsMTx4 sensitized both channels to tension by increasing the opening rate and decreasing the closing rate. With ascending and descending pressure ramps, GsMTx4 increased the gating hysteresis for MscS, a consequence of slower gating kinetics. Quantitative kinetic analysis of the primary C↔O transition showed that the hysteresis is a result of the decreased closing rate. The gating barrier location relative to the open state energy well was unaffected by GsMTx4. A reconstructed energy profile suggests that the peptide prestresses the resting state of MscS, lowering the net barrier to opening and stabilizes the open conformation by ∼8 kT. In excised patches, both MscL and MscS exhibit reversible adaptation, a process separable from inactivation for MscS. GsMTx4 decreased the rate of reversible adaptation for both channels and the MscS recovery rate from the inactivation. These measurements support a mechanism where GsMTx4 binds to the lipid interface of the channel, increasing the local stress that is sensed by the channels and stabilizing the expanded conformations.
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Affiliation(s)
- Kishore Kamaraju
- Department of Biology, University of Maryland, College Park, Maryland, USA
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37
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Butterwick JA, MacKinnon R. Solution structure and phospholipid interactions of the isolated voltage-sensor domain from KvAP. J Mol Biol 2010; 403:591-606. [PMID: 20851706 DOI: 10.1016/j.jmb.2010.09.012] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Revised: 09/04/2010] [Accepted: 09/07/2010] [Indexed: 10/19/2022]
Abstract
Voltage-sensor domains (VSDs) are specialized transmembrane segments that confer voltage sensitivity to many proteins such as ion channels and enzymes. The activities of these domains are highly dependent on both the chemical properties and the physical properties of the surrounding membrane environment. To learn about VSD-lipid interactions, we used nuclear magnetic resonance spectroscopy to determine the structure and phospholipid interface of the VSD from the voltage-dependent K(+) channel KvAP (prokaryotic Kv from Aeropyrum pernix). The solution structure of the KvAP VSD solubilized within phospholipid micelles is similar to a previously determined crystal structure solubilized by a nonionic detergent and complexed with an antibody fragment. The differences observed include a previously unidentified short amphipathic α-helix that precedes the first transmembrane helix and a subtle rigid-body repositioning of the S3-S4 voltage-sensor paddle. Using (15)N relaxation experiments, we show that much of the VSD, including the pronounced kink in S3 and the S3-S4 paddle, is relatively rigid on the picosecond-to-nanosecond timescale. In contrast, the kink in S3 is mobile on the microsecond-to-millisecond timescale and may act as a hinge in the movement of the paddle during channel gating. We characterized the VSD-phospholipid micelle interactions using nuclear Overhauser effect spectroscopy and showed that the micelle uniformly coats the KvAP VSD and approximates the chemical environment of a phospholipid bilayer. Using paramagnetically labeled phospholipids, we show that bilayer-forming lipids interact with the S3 and S4 helices more strongly than with S1 and S2.
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Affiliation(s)
- Joel A Butterwick
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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38
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Schow EV, Freites JA, Gogna K, White SH, Tobias DJ. Down-state model of the voltage-sensing domain of a potassium channel. Biophys J 2010; 98:2857-66. [PMID: 20550898 DOI: 10.1016/j.bpj.2010.03.031] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 02/14/2010] [Accepted: 03/02/2010] [Indexed: 11/30/2022] Open
Abstract
Voltage-sensing domains (VSDs) of voltage-gated potassium (Kv) channels undergo a series of conformational changes upon membrane depolarization, from a down state when the channel is at rest to an up state, all of which lead to the opening of the channel pore. The crystal structures reported to date reveal the pore in an open state and the VSDs in an up state. To gain insights into the structure of the down state, we used a set of experiment-based restraints to generate a model of the down state of the KvAP VSD using molecular-dynamics simulations of the VSD in a lipid bilayer in excess water. The equilibrated VSD configuration is consistent with the biotin-avidin accessibility and internal salt-bridge data used to generate it, and with additional biotin-avidin accessibility data. In the model, both the S3b and S4 segments are displaced approximately 10 A toward the intracellular side with respect to the up-state configuration, but they do not move as a rigid body. Arginine side chains that carry the majority of the gating charge also make large excursions between the up and down states. In both states, arginines interact with water and participate in salt bridges with acidic residues and lipid phosphate groups. An important feature that emerges from the down-state model is that the N-terminal half of the S4 segment adopts a 3(10)-helical conformation, which appears to be necessary to satisfy a complex salt-bridge network.
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Affiliation(s)
- Eric V Schow
- Department of Physics and Astronomy, University of California, Irvine, California, USA
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39
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Wee CL, Gavaghan D, Sansom MSP. Interactions between a voltage sensor and a toxin via multiscale simulations. Biophys J 2010; 98:1558-65. [PMID: 20409475 PMCID: PMC2856169 DOI: 10.1016/j.bpj.2009.12.4321] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 12/29/2009] [Accepted: 12/30/2009] [Indexed: 02/07/2023] Open
Abstract
Gating-modifier toxins inhibit voltage-gated ion channels by binding the voltage sensors (VS) and altering the energetics of voltage-dependent gating. These toxins are thought to gain access to the VS via the membrane (i.e., by partitioning from water into the membrane before binding the VS). We used serial multiscale molecular-dynamics (MD) simulations, via a combination of coarse-grained (CG) and atomistic (AT) simulations, to study how the toxin VSTx1, which inhibits the archeabacterial voltage-gated potassium channel KvAP, interacts with an isolated membrane-embedded VS domain. In the CG simulations, VSTx1, which was initially located in water, partitioned into the headgroup/water interface of the lipid bilayer before binding the VS. The CG configurations were used to generate AT representations of the system, which were subjected to AT-MD to further evaluate the stability of the complex and refine the predicted VS/toxin interface. VSTx1 interacted with a binding site on the VS formed by the C-terminus of S1, the S1-S2 linker, and the N-terminus of S4. The predicted VS/toxin interactions are suggestive of toxin-mediated perturbations of the interaction between the VS and the pore domain of Kv channels, and of the membrane. Our simulations support a membrane-access mechanism of inhibition of Kv channels by VS toxins. Overall, the results show that serial multiscale MD simulations may be used to model a two-stage process of protein-bilayer and protein-protein interactions within a membrane.
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Affiliation(s)
- Chze Ling Wee
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Finol-Urdaneta RK, McArthur JR, Juranka PF, French RJ, Morris CE. Modulation of KvAP unitary conductance and gating by 1-alkanols and other surface active agents. Biophys J 2010; 98:762-72. [PMID: 20197029 DOI: 10.1016/j.bpj.2009.10.053] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 10/23/2009] [Accepted: 10/26/2009] [Indexed: 11/18/2022] Open
Abstract
The actions of alcohols and anesthetics on ion channels are poorly understood. Controversy continues about whether bilayer restructuring is relevant to the modulatory effects of these surface active agents (SAAs). Some voltage-gated K channels (Kv), but not KvAP, have putative low affinity alcohol-binding sites, and because KvAP structures have been determined in bilayers, KvAP could offer insights into the contribution of bilayer mechanics to SAA actions. We monitored KvAP unitary conductance and macroscopic activation and inactivation kinetics in PE:PG/decane bilayers with and without exposure to classic SAAs (short-chain 1-alkanols, cholesterol, and selected anesthetics: halothane, isoflurane, chloroform). At levels that did not measurably alter membrane specific capacitance, alkanols caused functional changes in KvAP behavior including lowered unitary conductance, modified kinetics, and shifted voltage dependence for activation. A simple explanation is that the site of SAA action on KvAP is its entire lateral interface with the PE:PG/decane bilayer, with SAA-induced changes in surface tension and bilayer packing order combining to modulate the shape and stability of various conformations. The KvAP structural adjustment to diverse bilayer pressure profiles has implications for understanding desirable and undesirable actions of SAA-like drugs and, broadly, predicts that channel gating, conductance and pharmacology may differ when membrane packing order differs, as in raft versus nonraft domains.
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Affiliation(s)
- Rocio K Finol-Urdaneta
- Hotchkiss Brain Institute and Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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Targeting voltage sensors in sodium channels with spider toxins. Trends Pharmacol Sci 2010; 31:175-82. [PMID: 20097434 DOI: 10.1016/j.tips.2009.12.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 12/15/2009] [Accepted: 12/17/2009] [Indexed: 12/19/2022]
Abstract
Voltage-activated sodium (Nav) channels are essential in generating and propagating nerve impulses, placing them amongst the most widely targeted ion channels by toxins from venomous organisms. An increasing number of spider toxins have been shown to interfere with the voltage-driven activation process of mammalian Nav channels, possibly by interacting with one or more of their voltage sensors. This review focuses on our existing knowledge of the mechanism by which spider toxins affect Nav channel gating and the possible applications of these toxins in the drug discovery process.
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Schmidt D, Cross SR, MacKinnon R. A gating model for the archeal voltage-dependent K(+) channel KvAP in DPhPC and POPE:POPG decane lipid bilayers. J Mol Biol 2009; 390:902-12. [PMID: 19481093 DOI: 10.1016/j.jmb.2009.05.062] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 05/18/2009] [Accepted: 05/19/2009] [Indexed: 10/20/2022]
Abstract
Voltage-dependent K(+) (Kv) channels form the basis of the excitability of nerves and muscles. KvAP is a well-characterized archeal Kv channel that has been widely used to investigate many aspects of Kv channel biochemistry, biophysics, and structure. In this study, a minimal kinetic gating model for KvAP function in two different phospholipid decane bilayers is developed. In most aspects, KvAP gating is similar to the well-studied eukaryotic Shaker Kv channel: conformational changes occur within four voltage sensors, followed by pore opening. Unlike the Shaker Kv channel, KvAP possesses an inactivated state that is accessible from the pre-open state of the channel. Changing the lipid composition of the membrane influences multiple gating transitions in the model, but, most dramatically, the rate of recovery from inactivation. Inhibition by the voltage sensor toxin VSTx1 is most easily explained if VSTx1 binds only to the depolarized conformation of the voltage sensor. By delaying the voltage sensor's return to the hyperpolarized conformation, VSTx1 favors the inactivated state of KvAP.
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Affiliation(s)
- Daniel Schmidt
- Howard Hughes Medical Institute, Rockefeller University, New York, NY 10065, USA
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Diochot S. Precious Natural Peptides from Spider Venoms: New Tools for Studying Potassium Channels. TOXIN REV 2008. [DOI: 10.1080/07313830500237059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Lipid bilayer deformation and the free energy of interaction of a Kv channel gating-modifier toxin. Biophys J 2008; 95:3816-26. [PMID: 18621840 DOI: 10.1529/biophysj.108.130971] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A number of membrane proteins act via binding at the water/lipid bilayer interface. An important example of such proteins is provided by the gating-modifier toxins that act on voltage-gated potassium (Kv) channels. They are thought to partition to the headgroup region of lipid bilayers, and so provide a good system for probing the nature of interactions of a protein with the water/bilayer interface. We used coarse-grained molecular dynamics simulations to compute the one-dimensional potential of mean force (i.e., free energy) profile that governs the interaction between a Kv channel gating-modifier toxin (VSTx1) and model phospholipid bilayers. The reaction coordinate sampled corresponds to the position of the toxin along the bilayer normal. The course-grained representation of the protein and lipids enabled us to explore extended time periods, revealing aspects of toxin/bilayer dynamics and energetics that would be difficult to observe on the timescales currently afforded by atomistic molecular dynamics simulations. In particular, we show for this model system that the bilayer deforms as it interacts with the toxin, and that such deformations perturb the free energy profile. Bilayer deformation therefore adds an additional layer of complexity to be addressed in investigations of membrane/protein systems. In particular, one should allow for local deformations that may arise due to the spatial array of charged and hydrophobic elements of an interfacially located membrane protein.
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Tao X, MacKinnon R. Functional analysis of Kv1.2 and paddle chimera Kv channels in planar lipid bilayers. J Mol Biol 2008; 382:24-33. [PMID: 18638484 DOI: 10.1016/j.jmb.2008.06.085] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 06/26/2008] [Accepted: 06/30/2008] [Indexed: 10/21/2022]
Abstract
Voltage-dependent K(+) (Kv) channels play key roles in shaping electrical signaling in both excitable and nonexcitable cells. These channels open and close in response to the voltage changes across the cell membrane. Many studies have been carried out in order to understand the voltage-sensing mechanism. Our laboratory recently determined the atomic structures of a mammalian Kv channel Kv1.2 and a mutant of Kv1.2 named the 'paddle chimera' channel, in which the voltage sensor paddle was transferred from Kv2.1 to Kv1.2. These two structures provide atomic descriptions of voltage-dependent channels with unprecedented clarity. Until now, the functional integrity of these two channels biosynthesized in yeast cells has not been assessed. Here, we report the electrophysiological and pharmacological properties of Kv1.2 and the paddle chimera channels in planar lipid bilayers. We demonstrate that Pichia yeast produce 'normally functioning' mammalian Kv channels with qualitatively similar features to the Shaker K(+) channel in the absence of the N-terminal inactivation gate and that the paddle chimera mutant channel functions as well as Kv1.2. We find, however, that in several respects, the Kv1.2 channel exhibits functional properties that are distinct from Kv1.2 channels reported in the literature.
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Affiliation(s)
- Xiao Tao
- Howard Hughes Medical Institute, Department of Molecular Neurobiology and Biophysics, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
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Chakrapani S, Cuello LG, Cortes DM, Perozo E. Structural dynamics of an isolated voltage-sensor domain in a lipid bilayer. Structure 2008; 16:398-409. [PMID: 18334215 DOI: 10.1016/j.str.2007.12.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 11/30/2007] [Accepted: 12/16/2007] [Indexed: 10/22/2022]
Abstract
A strong interplay between the voltage-sensor domain (VSD) and the pore domain (PD) underlies voltage-gated channel functions. In a few voltage-sensitive proteins, the VSD has been shown to function without a canonical PD, although its structure and oligomeric state remain unknown. Here, using EPR spectroscopy, we show that the isolated VSD of KvAP can remain monomeric in a reconstituted bilayer and retain a transmembrane conformation. We find that water-filled crevices extending deep into the membrane around S3, a scaffold conducive to transport of protons/cations, are intrinsic to the VSD. Differences in solvent accessibility in comparison to the full-length KvAP allowed us to define an interacting footprint of the PD on the VSD. This interaction is centered around S1 and S2 and suggests a rotation of 70 degrees -100 degrees relative to Kv1.2-Kv2.1 chimera. Sequence-conservation patterns in Kv channels, Hv channels, and voltage-sensitive phosphatases reveal several near-universal features suggesting a common molecular architecture for all VSDs.
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Affiliation(s)
- Sudha Chakrapani
- Institute for Biophysical Dynamics, Center for Integrative Science, University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
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Wee CL, Sansom MSP, Reich S, Akhmatskaya E. Improved Sampling for Simulations of Interfacial Membrane Proteins: Application of Generalized Shadow Hybrid Monte Carlo to a Peptide Toxin/Bilayer System. J Phys Chem B 2008; 112:5710-7. [DOI: 10.1021/jp076712u] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Vamvouka M, Cieslak J, Van Eps N, Hubbell W, Gross A. The structure of the lipid-embedded potassium channel voltage sensor determined by double-electron-electron resonance spectroscopy. Protein Sci 2008; 17:506-17. [PMID: 18287283 DOI: 10.1110/ps.073310008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
A four-pulse electron paramagnetic resonance experiment was used to measure long-range inter-subunit distances in reconstituted KvAP, a voltage-dependent potassium (Kv) channel. The measurements have allowed us to reach the following five conclusions about the native structure of the voltage sensor of KvAP. First, the S1 helix of the voltage sensor engages in a helix packing interaction with the pore domain. Second, the crystallographically observed antiparallel helix-turn-helix motif of the voltage-sensing paddle is retained in the membrane-embedded voltage sensor. Third, the paddle is oriented in such a way as to expose one face to the pore domain and the opposite face to the membrane. Fourth, the paddle and the pore domain appear to be separated by a gap that is sufficiently wide for lipids to penetrate between the two domains. Fifth, the critical voltage-sensing arginine residues on the paddle appear to be lipid exposed. These results demonstrate the importance of the membrane for the native structure of Kv channels, suggest that lipids are an integral part of their native structure, and place the voltage-sensing machinery into a complex lipid environment near the pore domain.
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Affiliation(s)
- Magdalini Vamvouka
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Chicago, Illinois 60611, USA
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Portability of paddle motif function and pharmacology in voltage sensors. Nature 2007; 450:370-5. [PMID: 18004375 DOI: 10.1038/nature06266] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 09/17/2007] [Indexed: 01/28/2023]
Abstract
Voltage-sensing domains enable membrane proteins to sense and react to changes in membrane voltage. Although identifiable S1-S4 voltage-sensing domains are found in an array of conventional ion channels and in other membrane proteins that lack pore domains, the extent to which their voltage-sensing mechanisms are conserved is unknown. Here we show that the voltage-sensor paddle, a motif composed of S3b and S4 helices, can drive channel opening with membrane depolarization when transplanted from an archaebacterial voltage-activated potassium channel (KvAP) or voltage-sensing domain proteins (Hv1 and Ci-VSP) into eukaryotic voltage-activated potassium channels. Tarantula toxins that partition into membranes can interact with these paddle motifs at the protein-lipid interface and similarly perturb voltage-sensor activation in both ion channels and proteins with a voltage-sensing domain. Our results show that paddle motifs are modular, that their functions are conserved in voltage sensors, and that they move in the relatively unconstrained environment of the lipid membrane. The widespread targeting of voltage-sensor paddles by toxins demonstrates that this modular structural motif is an important pharmacological target.
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