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Wu Y, Yan Y, Yang Y, Bian S, Rivetta A, Allen K, Sigworth FJ. Cryo-EM structures of Kv1.2 potassium channels, conducting and non-conducting. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.02.543446. [PMID: 37398110 PMCID: PMC10312591 DOI: 10.1101/2023.06.02.543446] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
We present near-atomic-resolution cryo-EM structures of the mammalian voltage-gated potassium channel Kv1.2 in open, C-type inactivated, toxin-blocked and sodium-bound states at 3.2 Å, 2.5 Å, 3.2 Å, and 2.9Å. These structures, all obtained at nominally zero membrane potential in detergent micelles, reveal distinct ion-occupancy patterns in the selectivity filter. The first two structures are very similar to those reported in the related Shaker channel and the much-studied Kv1.2-2.1 chimeric channel. On the other hand, two new structures show unexpected patterns of ion occupancy. First, the toxin α-Dendrotoxin, like Charybdotoxin, is seen to attach to the negatively-charged channel outer mouth, and a lysine residue penetrates into the selectivity filter, with the terminal amine coordinated by carbonyls, partially disrupting the outermost ion-binding site. In the remainder of the filter two densities of bound ions are observed, rather than three as observed with other toxin-blocked Kv channels. Second, a structure of Kv1.2 in Na+ solution does not show collapse or destabilization of the selectivity filter, but instead shows an intact selectivity filter with ion density in each binding site. We also attempted to image the C-type inactivated Kv1.2 W366F channel in Na+ solution, but the protein conformation was seen to be highly variable and only a low-resolution structure could be obtained. These findings present new insights into the stability of the selectivity filter and the mechanism of toxin block of this intensively studied, voltage-gated potassium channel.
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Affiliation(s)
- Yangyu Wu
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Yangyang Yan
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Youshan Yang
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Shumin Bian
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Alberto Rivetta
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Ken Allen
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
| | - Fred J Sigworth
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut USA
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Singh Y, Sarkar D, Duari S, G S, Indra Guru PK, M V H, Singh D, Bhardwaj S, Kalia J. Dissecting the contributions of membrane affinity and bivalency of the spider venom protein DkTx to its sustained mode of TRPV1 activation. J Biol Chem 2023; 299:104903. [PMID: 37302551 PMCID: PMC10404664 DOI: 10.1016/j.jbc.2023.104903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 06/03/2023] [Accepted: 06/05/2023] [Indexed: 06/13/2023] Open
Abstract
The spider venom protein, double-knot toxin (DkTx), partitions into the cellular membrane and binds bivalently to the pain-sensing ion channel, TRPV1, triggering long-lasting channel activation. In contrast, its monovalent single knots membrane partition poorly and invoke rapidly reversible TRPV1 activation. To discern the contributions of the bivalency and membrane affinity of DkTx to its sustained mode of action, here, we developed diverse toxin variants including those containing truncated linkers between individual knots, precluding bivalent binding. Additionally, by appending the single-knot domains to the Kv2.1 channel-targeting toxin, SGTx, we created monovalent double-knot proteins that demonstrated higher membrane affinity and more sustained TRPV1 activation than the single-knots. We also produced hyper-membrane affinity-possessing tetra-knot proteins, (DkTx)2 and DkTx-(SGTx)2, that demonstrated longer-lasting TRPV1 activation than DkTx, establishing the central role of the membrane affinity of DkTx in endowing it with its sustained TRPV1 activation properties. These results suggest that high membrane affinity-possessing TRPV1 agonists can potentially serve as long-acting analgesics.
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Affiliation(s)
- Yashaswi Singh
- Department of Biology, Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Debayan Sarkar
- Department of Biology, Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Subhadeep Duari
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Shashaank G
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Pawas Kumar Indra Guru
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Hrishikesh M V
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Dheerendra Singh
- Department of Biology, Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India
| | - Sahil Bhardwaj
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India
| | - Jeet Kalia
- Department of Biology, Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India; Department of Chemistry, Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India; Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal, Madhya Pradesh, India.
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3
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Deuis JR, Ragnarsson L, Robinson SD, Dekan Z, Chan L, Jin AH, Tran P, McMahon KL, Li S, Wood JN, Cox JJ, King GF, Herzig V, Vetter I. The Tarantula Venom Peptide Eo1a Binds to the Domain II S3-S4 Extracellular Loop of Voltage-Gated Sodium Channel Na V1.8 to Enhance Activation. Front Pharmacol 2022; 12:789570. [PMID: 35095499 PMCID: PMC8795738 DOI: 10.3389/fphar.2021.789570] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 12/20/2021] [Indexed: 12/19/2022] Open
Abstract
Venoms from cone snails and arachnids are a rich source of peptide modulators of voltage-gated sodium (NaV) channels, however relatively few venom-derived peptides with activity at the mammalian NaV1.8 subtype have been isolated. Here, we describe the discovery and functional characterisation of β-theraphotoxin-Eo1a, a peptide from the venom of the Tanzanian black and olive baboon tarantula Encyocratella olivacea that modulates NaV1.8. Eo1a is a 37-residue peptide that increases NaV1.8 peak current (EC50 894 ± 146 nM) and causes a large hyperpolarising shift in both the voltage-dependence of activation (ΔV50-20.5 ± 1.2 mV) and steady-state fast inactivation (ΔV50-15.5 ± 1.8 mV). At a concentration of 10 μM, Eo1a has varying effects on the peak current and channel gating of NaV1.1-NaV1.7, although its activity is most pronounced at NaV1.8. Investigations into the binding site of Eo1a using NaV1.7/NaV1.8 chimeras revealed a critical contribution of the DII S3-S4 extracellular loop of NaV1.8 to toxin activity. Results from this work may form the basis for future studies that lead to the rational design of spider venom-derived peptides with improved potency and selectivity at NaV1.8.
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Affiliation(s)
- Jennifer R. Deuis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Lotten Ragnarsson
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Samuel D. Robinson
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Zoltan Dekan
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Lerena Chan
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Ai-Hua Jin
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Poanna Tran
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Kirsten L. McMahon
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Shengnan Li
- Wolfson Institute for Biomedical Research, University College London, London, United Kingdom
| | - John N. Wood
- Wolfson Institute for Biomedical Research, University College London, London, United Kingdom
| | - James J. Cox
- Wolfson Institute for Biomedical Research, University College London, London, United Kingdom
| | - Glenn F. King
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, Brisbane, QLD, Australia
| | - Volker Herzig
- GeneCology Research Centre, University of the Sunshine Coast, Sippy Downs, QLD, Australia
- School of Science, Technology and Engineering, University of the Sunshine Coast, Sippy Downs, QLD, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD, Australia
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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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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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Mechanism of hERG inhibition by gating-modifier toxin, APETx1, deduced by functional characterization. BMC Mol Cell Biol 2021; 22:3. [PMID: 33413079 PMCID: PMC7791793 DOI: 10.1186/s12860-020-00337-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 12/14/2020] [Indexed: 12/13/2022] Open
Abstract
Background Human ether-à-go-go-related gene potassium channel 1 (hERG) is a voltage-gated potassium channel, the voltage-sensing domain (VSD) of which is targeted by a gating-modifier toxin, APETx1. APETx1 is a 42-residue peptide toxin of sea anemone Anthopleura elegantissima and inhibits hERG by stabilizing the resting state. A previous study that conducted cysteine-scanning analysis of hERG identified two residues in the S3-S4 region of the VSD that play important roles in hERG inhibition by APETx1. However, mutational analysis of APETx1 could not be conducted as only natural resources have been available until now. Therefore, it remains unclear where and how APETx1 interacts with the VSD in the resting state. Results We established a method for preparing recombinant APETx1 and determined the NMR structure of the recombinant APETx1, which is structurally equivalent to the natural product. Electrophysiological analyses using wild type and mutants of APETx1 and hERG revealed that their hydrophobic residues, F15, Y32, F33, and L34, in APETx1, and F508 and I521 in hERG, in addition to a previously reported acidic hERG residue, E518, play key roles in the inhibition of hERG by APETx1. Our hypothetical docking models of the APETx1-VSD complex satisfied the results of mutational analysis. Conclusions The present study identified the key residues of APETx1 and hERG that are involved in hERG inhibition by APETx1. These results would help advance understanding of the inhibitory mechanism of APETx1, which could provide a structural basis for designing novel ligands targeting the VSDs of KV channels.
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Rupasinghe DB, Herzig V, Vetter I, Dekan Z, Gilchrist J, Bosmans F, Alewood PF, Lewis RJ, King GF. Mutational analysis of ProTx-I and the novel venom peptide Pe1b provide insight into residues responsible for selective inhibition of the analgesic drug target Na V1.7. Biochem Pharmacol 2020; 181:114080. [PMID: 32511987 DOI: 10.1016/j.bcp.2020.114080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/30/2020] [Accepted: 06/03/2020] [Indexed: 12/19/2022]
Abstract
Management of chronic pain presents a major challenge, since many currently available treatments lack efficacy and have problems such as addiction and tolerance. Loss of function mutations in the SCN9A gene lead to a congenital inability to feel pain, with no other sensory deficits aside from anosmia. SCN9A encodes the voltage-gated sodium (NaV) channel 1.7 (NaV1.7), which has been identified as a primary pain target. However, in developing NaV1.7-targeted analgesics, extreme care must to be taken to avoid off-target activity on other NaV subtypes that are critical for survival. Since spider venoms are an excellent source of NaV channel modulators, we screened a panel of spider venoms to identify selective NaV1.7 inhibitors. This led to identification of two novel NaV modulating venom peptides (β/μ-theraphotoxin-Pe1a and β/μ-theraphotoxin-Pe1b (Pe1b) from the arboreal tarantula Phormingochilus everetti. A third peptide isolated from the tarantula Bumba pulcherrimaklaasi was identical to the well-known ProTx-I (β/ω-theraphotoxin-Tp1a) from the tarantula Thrixopelma pruriens. A tethered toxin (t-toxin)-based alanine scanning strategy was used to determine the NaV1.7 pharmacophore of ProTx-I. We designed several ProTx-I and Pe1b analogues, and tested them for activity and NaV channel subtype selectivity. Several analogues had improved potency against NaV1.7, and altered specificity against other NaV channels. These analogues provide a foundation for development of Pe1b as a lead molecule for therapeutic inhibition of NaV1.7.
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Affiliation(s)
- Darshani B Rupasinghe
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Volker Herzig
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4105, Australia
| | - Zoltan Dekan
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - John Gilchrist
- Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Frank Bosmans
- Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia
| | - Richard J Lewis
- 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.
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Mueller A, Dekan Z, Kaas Q, Agwa AJ, Starobova H, Alewood PF, Schroeder CI, Mobli M, Deuis JR, Vetter I. Mapping the Molecular Surface of the Analgesic Na V1.7-Selective Peptide Pn3a Reveals Residues Essential for Membrane and Channel Interactions. ACS Pharmacol Transl Sci 2020; 3:535-546. [PMID: 32566918 DOI: 10.1021/acsptsci.0c00002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Indexed: 12/18/2022]
Abstract
Compelling human genetic studies have identified the voltage-gated sodium channel NaV1.7 as a promising therapeutic target for the treatment of pain. The analgesic spider-venom-derived peptide μ-theraphotoxin-Pn3a is an exceptionally potent and selective inhibitor of NaV1.7; however, little is known about the structure-activity relationships or channel interactions that define this activity. We rationally designed 17 Pn3a analogues and determined their activity at hNaV1.7 using patch-clamp electrophysiology. The positively charged amino acids K22 and K24 were identified as crucial for Pn3a activity, with molecular modeling identifying interactions of these residues with the S3-S4 loop of domain II of hNaV1.7. Removal of hydrophobic residues Y4, Y27, and W30 led to a loss of potency (>250-fold), while replacement of negatively charged D1 and D8 residues with a positively charged lysine led to increased potencies (>13-fold), likely through alterations in membrane lipid interactions. Mutating D8 to an asparagine led to the greatest improvement in Pn3a potency at NaV1.7 (20-fold), while maintaining >100-fold selectivity over the major off-targets NaV1.4, NaV1.5, and NaV1.6. The Pn3a[D8N] mutant retained analgesic activity in vivo, significantly attenuating mechanical allodynia in a clinically relevant mouse model of postsurgical pain at doses 3-fold lower than those with wild-type Pn3a, without causing motor-adverse effects. Results from this study will facilitate future rational design of potent and selective peptidic NaV1.7 inhibitors for the development of more efficacious and safer analgesics as well as to further investigate the involvement of NaV1.7 in pain.
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Affiliation(s)
- Alexander Mueller
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Zoltan Dekan
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Quentin Kaas
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Akello J Agwa
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Hana Starobova
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Christina I Schroeder
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Jennifer R Deuis
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, Queensland 4072, Australia.,School of Pharmacy, The University of Queensland, Woolloongabba, Queensland 4102, Australia
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Spider Knottin Pharmacology at Voltage-Gated Sodium Channels and Their Potential to Modulate Pain Pathways. Toxins (Basel) 2019; 11:toxins11110626. [PMID: 31671792 PMCID: PMC6891507 DOI: 10.3390/toxins11110626] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/24/2019] [Accepted: 10/24/2019] [Indexed: 12/15/2022] Open
Abstract
Voltage-gated sodium channels (NaVs) are a key determinant of neuronal signalling. Neurotoxins from diverse taxa that selectively activate or inhibit NaV channels have helped unravel the role of NaV channels in diseases, including chronic pain. Spider venoms contain the most diverse array of inhibitor cystine knot (ICK) toxins (knottins). This review provides an overview on how spider knottins modulate NaV channels and describes the structural features and molecular determinants that influence their affinity and subtype selectivity. Genetic and functional evidence support a major involvement of NaV subtypes in various chronic pain conditions. The exquisite inhibitory properties of spider knottins over key NaV subtypes make them the best lead molecules for the development of novel analgesics to treat chronic pain.
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10
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Tabakmakher VM, Krylov NA, Kuzmenkov AI, Efremov RG, Vassilevski AA. Kalium 2.0, a comprehensive database of polypeptide ligands of potassium channels. Sci Data 2019; 6:73. [PMID: 31133708 PMCID: PMC6536513 DOI: 10.1038/s41597-019-0074-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 03/29/2019] [Indexed: 12/31/2022] Open
Abstract
Potassium channels are the most diverse group of ion channels in humans. They take vital parts in numerous physiological processes and their malfunction gives rise to a range of pathologies. In addition to small molecules, there is a wide selection of several hundred polypeptide ligands binding to potassium channels, the majority of which have been isolated from animal venoms. Until recently, only scorpion toxins received focused attention being systematically assembled in the manually curated Kalium database, but there is a diversity of well-characterized potassium channel ligands originating from other sources. To address this issue, here we present the updated and improved Kalium 2.0 that covers virtually all known polypeptide ligands of potassium channels and reviews all available pharmacological data. In addition to an expansion, we have introduced several new features to the database including posttranslational modification annotation, indication of ligand mode of action, BLAST search, and possibility of data export.
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Affiliation(s)
- Valentin M Tabakmakher
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
- School of Biomedicine, Far Eastern Federal University, Vladivostok, 690950, Russia
| | - Nikolay A Krylov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
- National Research University Higher School of Economics, Moscow, 101000, Russia
| | - Alexey I Kuzmenkov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - Roman G Efremov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
- National Research University Higher School of Economics, Moscow, 101000, Russia
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Oblast, 141700, Russia
| | - Alexander A Vassilevski
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia.
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Oblast, 141700, Russia.
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11
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Zhang Y, Luo J, He J, Rong M, Zeng X. JZTX-V Targets the Voltage Sensor in Kv4.2 to Inhibit I to Potassium Channels in Cardiomyocytes. Front Pharmacol 2019; 10:357. [PMID: 31040778 PMCID: PMC6476928 DOI: 10.3389/fphar.2019.00357] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 03/21/2019] [Indexed: 12/16/2022] Open
Abstract
Kv4 potassium channels are responsible for transient outward K+ currents in the cardiac action potential (AP). Previous experiments by our group demonstrated that Jingzhaotoxin-V (JZTX-V) selectively inhibits A-type potassium channels. However, the specific effects of JZTX-V on the transient outward (Ito) current of cardiomyocytes and underlying mechanism of action remain unclear. In the current study, 100 nM JZTX-V effectively inhibited the Ito current and extended the action potential duration (APD) of neonatal rat ventricular myocytes (NRVM). We further analyzed the effects of JZTX-V on Kv4.2, a cloned channel believed to underlie the Ito current in rat cardiomyocytes. JZTX-V inhibited the Kv4.2 current with a half-maximal inhibitory concentration (IC50) of 13 ± 1.7 nM. To establish the molecular mechanism underlying the inhibitory action of JZTX-V on Kv4.2, we performed alanine scanning mutagenesis of Kv4.2 and JZTX-V and assessed the effects of the mutations on binding activities of the proteins. Interestingly, the Kv4.2 mutations V285A, F289A, and V290A reduced the affinity for JZTX-V while I275A and L277A increased the affinity for JZTX-V. Moreover, mutation of positively charged residues (R20 and K22) of JZTX-V and the hydrophobic patch (formed by W5, M6, and W7) led to a significant reduction in toxin sensitivity, indicating that the hydrophobic patch and electrostatic interactions played key roles in the binding of JZTX-V with Kv4.2. Data from our study have shed light on the specific roles and molecular mechanisms of JZTX-V in the regulation of Ito potassium channels and supported its utility as a potential novel antiarrhythmic drug.
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Affiliation(s)
- Yiya Zhang
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, China.,Key Laboratory of Organ Injury, Aging and Regenerative Medicine of Hunan Province, Central South University, Changsha, China.,The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Ji Luo
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Juan He
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Mingqiang Rong
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Xiongzhi Zeng
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
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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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Agwa AJ, Peigneur S, Chow CY, Lawrence N, Craik DJ, Tytgat J, King GF, Henriques ST, Schroeder CI. Gating modifier toxins isolated from spider venom: Modulation of voltage-gated sodium channels and the role of lipid membranes. J Biol Chem 2018; 293:9041-9052. [PMID: 29703751 DOI: 10.1074/jbc.ra118.002553] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 04/25/2018] [Indexed: 11/06/2022] Open
Abstract
Gating modifier toxins (GMTs) are venom-derived peptides isolated from spiders and other venomous creatures and modulate activity of disease-relevant voltage-gated ion channels and are therefore being pursued as therapeutic leads. The amphipathic surface profile of GMTs has prompted the proposal that some GMTs simultaneously bind to the cell membrane and voltage-gated ion channels in a trimolecular complex. Here, we examined whether there is a relationship among spider GMT amphipathicity, membrane binding, and potency or selectivity for voltage-gated sodium (NaV) channels. We used NMR spectroscopy and in silico calculations to examine the structures and physicochemical properties of a panel of nine GMTs and deployed surface plasmon resonance to measure GMT affinity for lipids putatively found in proximity to NaV channels. Electrophysiology was used to quantify GMT activity on NaV1.7, an ion channel linked to chronic pain. Selectivity of the peptides was further examined against a panel of NaV channel subtypes. We show that GMTs adsorb to the outer leaflet of anionic lipid bilayers through electrostatic interactions. We did not observe a direct correlation between GMT amphipathicity and affinity for lipid bilayers. Furthermore, GMT-lipid bilayer interactions did not correlate with potency or selectivity for NaVs. We therefore propose that increased membrane binding is unlikely to improve subtype selectivity and that the conserved amphipathic GMT surface profile is an adaptation that facilitates simultaneous modulation of multiple NaVs.
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Affiliation(s)
- Akello J Agwa
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - Steve Peigneur
- Laboratory of Toxicology and Pharmacology, University of Leuven (KU Leuven), 3000 Leuven, Belgium
| | - Chun Yuen Chow
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - Nicole Lawrence
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - David J Craik
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - Jan Tytgat
- Laboratory of Toxicology and Pharmacology, University of Leuven (KU Leuven), 3000 Leuven, Belgium
| | - Glenn F King
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - Sónia Troeira Henriques
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
| | - Christina I Schroeder
- From the Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia and
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14
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Jiménez-Vargas JM, Possani LD, Luna-Ramírez K. Arthropod toxins acting on neuronal potassium channels. Neuropharmacology 2017; 127:139-160. [PMID: 28941737 DOI: 10.1016/j.neuropharm.2017.09.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 01/01/2023]
Abstract
Arthropod venoms are a rich mixture of biologically active compounds exerting different physiological actions across diverse phyla and affecting multiple organ systems including the central nervous system. Venom compounds can inhibit or activate ion channels, receptors and transporters with high specificity and affinity providing essential insights into ion channel function. In this review, we focus on arthropod toxins (scorpions, spiders, bees and centipedes) acting on neuronal potassium channels. A brief description of the K+ channels classification and structure is included and a compendium of neuronal K+ channels and the arthropod toxins that modify them have been listed. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Juana María Jiménez-Vargas
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Lourival D Possani
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Karen Luna-Ramírez
- Illawarra Health and Medical Research Institute, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
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15
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Moreels L, Peigneur S, Galan DT, De Pauw E, Béress L, Waelkens E, Pardo LA, Quinton L, Tytgat J. APETx4, a Novel Sea Anemone Toxin and a Modulator of the Cancer-Relevant Potassium Channel K V10.1. Mar Drugs 2017; 15:md15090287. [PMID: 28902151 PMCID: PMC5618426 DOI: 10.3390/md15090287] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/05/2017] [Accepted: 09/07/2017] [Indexed: 12/31/2022] Open
Abstract
The human ether-à-go-go channel (hEag1 or KV10.1) is a cancer-relevant voltage-gated potassium channel that is overexpressed in a majority of human tumors. Peptides that are able to selectively inhibit this channel can be lead compounds in the search for new anticancer drugs. Here, we report the activity-guided purification and electrophysiological characterization of a novel KV10.1 inhibitor from the sea anemone Anthopleura elegantissima. Purified sea anemone fractions were screened for inhibitory activity on KV10.1 by measuring whole-cell currents as expressed in Xenopus laevis oocytes using the two-microelectrode voltage clamp technique. Fractions that showed activity on Kv10.1 were further purified by RP-HPLC. The amino acid sequence of the peptide was determined by a combination of MALDI- LIFT-TOF/TOF MS/MS and CID-ESI-FT-ICR MS/MS and showed a high similarity with APETx1 and APETx3 and was therefore named APETx4. Subsequently, the peptide was electrophysiologically characterized on KV10.1. The selectivity of the toxin was investigated on an array of voltage-gated ion channels, including the cardiac human ether-à-go-go-related gene potassium channel (hERG or Kv11.1). The toxin inhibits KV10.1 with an IC50 value of 1.1 μM. In the presence of a similar toxin concentration, a shift of the activation curve towards more positive potentials was observed. Similar to the effect of the gating modifier toxin APETx1 on hERG, the inhibition of Kv10.1 by the isolated toxin is reduced at more positive voltages and the peptide seems to keep the channel in a closed state. Although the peptide also induces inhibitory effects on other KV and NaV channels, it exhibits no significant effect on hERG. Moreover, APETx4 induces a concentration-dependent cytotoxic and proapoptotic effect in various cancerous and noncancerous cell lines. This newly identified KV10.1 inhibitor can be used as a tool to further characterize the oncogenic channel KV10.1 or as a scaffold for the design and synthesis of more potent and safer anticancer drugs.
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Affiliation(s)
- Lien Moreels
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Diogo T Galan
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
| | - Edwin De Pauw
- Laboratory of Mass Spectrometry-MolSys, University of Liege, Liege 4000, Belgium.
| | - Lászlo Béress
- Immunology and Rheumatology, Section of Peptide Chemistry, Hannover Medical School (MHH), Hannover 30625, Germany.
| | - Etienne Waelkens
- Laboratory of Protein Phosphorylation and Proteomics, KU Leuven, Leuven 3000, Belgium.
| | - Luis A Pardo
- Oncophysiology Group, Max Planck Institute for Experimental Medicine; Göttingen 37075, Germany.
| | - Loïc Quinton
- Laboratory of Mass Spectrometry-MolSys, University of Liege, Liege 4000, Belgium.
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Leuven 3000, Belgium.
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16
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Cardoso FC, Dekan Z, Smith JJ, Deuis JR, Vetter I, Herzig V, Alewood PF, King GF, Lewis RJ. Modulatory features of the novel spider toxin μ-TRTX-Df1a isolated from the venom of the spider Davus fasciatus. Br J Pharmacol 2017; 174:2528-2544. [PMID: 28542706 DOI: 10.1111/bph.13865] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 05/01/2017] [Accepted: 05/02/2017] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND AND PURPOSE Naturally occurring dysfunction of voltage-gated sodium (NaV ) channels results in complex disorders such as chronic pain, making these channels an attractive target for new therapies. In the pursuit of novel NaV modulators, we investigated spider venoms for new inhibitors of NaV channels. EXPERIMENTAL APPROACH We used high-throughput screens to identify a NaV modulator in venom of the spider Davus fasciatus. Further characterization of this venom peptide was undertaken using fluorescent and electrophysiological assays, molecular modelling and a rodent pain model. KEY RESULTS We identified a potent NaV inhibitor named μ-TRTX-Df1a. This 34-residue peptide fully inhibited responses mediated by NaV 1.7 endogenously expressed in SH-SY5Y cells. Df1a also inhibited voltage-gated calcium (CaV 3) currents but had no activity against the voltage-gated potassium (KV 2) channel. The modelled structure of Df1a, which contains an inhibitor cystine knot motif, is reminiscent of the NaV channel toxin ProTx-I. Electrophysiology revealed that Df1a inhibits all NaV subtypes tested (hNaV 1.1-1.7). Df1a also slowed fast inactivation of NaV 1.1, NaV 1.3 and NaV 1.5 and modified the voltage-dependence of activation and inactivation of most of the NaV subtypes. Df1a preferentially binds to the domain II voltage-sensor and has additional interactions with the voltage sensors domains III and IV, which probably explains its modulatory features. Df1a was analgesic in vivo, reversing the spontaneous pain behaviours induced by the NaV activator OD1. CONCLUSION AND IMPLICATIONS μ-TRTX-Df1a shows potential as a new molecule for the development of drugs to treat pain disorders mediated by voltage-gated ion channels.
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Affiliation(s)
- Fernanda C Cardoso
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Zoltan Dekan
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Jennifer J Smith
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Jennifer R Deuis
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia.,School of Pharmacy, The University of Queensland, Woolloongabba, QLD, Australia
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia.,School of Pharmacy, The University of Queensland, Woolloongabba, QLD, Australia
| | - Volker Herzig
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
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17
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Agwa AJ, Henriques ST, Schroeder CI. Gating modifier toxin interactions with ion channels and lipid bilayers: Is the trimolecular complex real? Neuropharmacology 2017; 127:32-45. [PMID: 28400258 DOI: 10.1016/j.neuropharm.2017.04.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 11/15/2022]
Abstract
Spider peptide toxins have attracted attention because of their ability to target voltage-gated ion channels, which are involved in several pathologies including chronic pain and some cardiovascular conditions. A class of these peptides acts by modulating the gating mechanism of voltage-gated ion channels and are thus called gating modifier toxins (GMTs). In addition to their interactions with voltage-gated ion channels, some GMTs have affinity for lipid bilayers. This review discusses the potential importance of the cell membrane on the mode of action of GMTs. We propose that peptide-membrane interactions can anchor GMTs at the cell surface, thereby increasing GMT concentration in the vicinity of the channel binding site. We also propose that modulating peptide-membrane interactions might be useful for increasing the therapeutic potential of spider toxins. Furthermore, we explore the advantages and limitations of the methodologies currently used to examine peptide-membrane interactions. Although GMT-lipid membrane binding does not appear to be a requirement for the activity of all GMTs, it is an important feature, and future studies with GMTs should consider the trimolecular peptide-lipid membrane-channel complex. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Akello J Agwa
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Sónia T Henriques
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
| | - Christina I Schroeder
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
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18
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Gnanasambandam R, Ghatak C, Yasmann A, Nishizawa K, Sachs F, Ladokhin AS, Sukharev SI, Suchyna TM. GsMTx4: Mechanism of Inhibiting Mechanosensitive Ion Channels. Biophys J 2017; 112:31-45. [PMID: 28076814 PMCID: PMC5231890 DOI: 10.1016/j.bpj.2016.11.013] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 10/12/2016] [Accepted: 11/03/2016] [Indexed: 12/21/2022] Open
Abstract
GsMTx4 is a spider venom peptide that inhibits cationic mechanosensitive channels (MSCs). It has six lysine residues that have been proposed to affect membrane binding. We synthesized six analogs with single lysine-to-glutamate substitutions and tested them against Piezo1 channels in outside-out patches and independently measured lipid binding. Four analogs had ∼20% lower efficacy than the wild-type (WT) peptide. The equilibrium constants calculated from the rates of inhibition and washout did not correlate with the changes in inhibition. The lipid association strength of the WT GsMTx4 and the analogs was determined by tryptophan autofluorescence quenching and isothermal calorimetry with membrane vesicles and showed no significant differences in binding energy. Tryptophan fluorescence-quenching assays showed that both WT and analog peptides bound superficially near the lipid-water interface, although analogs penetrated deeper. Peptide-lipid association, as a function of lipid surface pressure, was investigated in Langmuir monolayers. The peptides occupied a large fraction of the expanded monolayer area, but that fraction was reduced by peptide expulsion as the pressure approached the monolayer-bilayer equivalence pressure. Analogs with compromised efficacy had pressure-area isotherms with steeper slopes in this region, suggesting tighter peptide association. The pressure-dependent redistribution of peptide between "deep" and "shallow" binding modes was supported by molecular dynamics (MD) simulations of the peptide-monolayer system under different area constraints. These data suggest a model placing GsMTx4 at the membrane surface, where it is stabilized by the lysines, and occupying a small fraction of the surface area in unstressed membranes. When applied tension reduces lateral pressure in the lipids, the peptides penetrate deeper acting as "area reservoirs" leading to partial relaxation of the outer monolayer, thereby reducing the effective magnitude of stimulus acting on the MSC gate.
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Affiliation(s)
| | - Chiranjib Ghatak
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas
| | - Anthony Yasmann
- Department of Biology, University of Maryland, College Park, Maryland
| | - Kazuhisa Nishizawa
- Clinical Laboratory Science, Teikyo University School of Medical Technology, Tokyo, Japan
| | - Frederick Sachs
- Department of Physiology and Biophysics, State University of New York, Buffalo, New York
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas
| | - Sergei I Sukharev
- Department of Biology, University of Maryland, College Park, Maryland
| | - Thomas M Suchyna
- Department of Physiology and Biophysics, State University of New York, Buffalo, New York.
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19
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Tao H, Chen X, Deng M, Xiao Y, Wu Y, Liu Z, Zhou S, He Y, Liang S. Interaction site for the inhibition of tarantula Jingzhaotoxin-XI on voltage-gated potassium channel Kv2.1. Toxicon 2016; 124:8-14. [PMID: 27810559 DOI: 10.1016/j.toxicon.2016.10.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 10/25/2016] [Accepted: 10/27/2016] [Indexed: 01/27/2023]
Abstract
Jingzhaotoxin-XI (JZTX-XI) is a 34-residue peptide from the Chinese tarantula Chilobrachys jingzhao venom that potently inhibits both voltage-gated sodium channel Nav1.5 and voltage-gated potassium channel Kv2.1. In the present study, we further showed that JZTX-XI blocked Kv2.1 currents with the IC50 value of 0.39 ± 0.06 μM. JZTX-XI significantly shifted the current-voltage (I-V) curves and normalized conductance-voltage (G-V) curves of Kv2.1 channel to more depolarized voltages. Ala-scanning mutagenesis analyses demonstrated that mutants I273A, F274A, and E277A reduced toxin binding affinity by 10-, 16-, and 18-fold, respectively, suggesting that three common residues (I273, F274, E277) in the Kv2.1 S3b segment contribute to the formation of JZTX-XI receptor site, and the acidic residue Glu at the position 277 in Kv2.1 is the most important residue for JZTX-XI sensitivity. A single replacement of E277 with Asp(D) increased toxin inhibitory activity. These results establish that JZTX-XI inhibits Kv2.1 activation by trapping the voltage sensor in the rested state through a similar mechanism to that of HaTx1, but these two toxins have small differences in the most crucial molecular determinant. Furthermore, the in-depth investigation of the subtle differences in molecular determinants may be useful for increasing our understanding of the molecular details regarding toxin-channel interactions.
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Affiliation(s)
- Huai Tao
- Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China; Division of Stem Cell Regulation and Application, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China.
| | - Xia Chen
- Department of Orthopedics, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, China
| | - Meichun Deng
- State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, Hunan 410013, China
| | - Yucheng Xiao
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Yuanyuan Wu
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Zhonghua Liu
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Sainan Zhou
- Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Yingchun He
- Department of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China; Division of Stem Cell Regulation and Application, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Songping Liang
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China.
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20
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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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21
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Feng J, Xie Z, Yang W, Zhao Y, Xiang F, Cao Z, Li W, Chen Z, Wu Y. Human beta-defensin 1, a new animal toxin-like blocker of potassium channel. Toxicon 2016; 113:1-6. [PMID: 26854370 DOI: 10.1016/j.toxicon.2016.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/26/2016] [Accepted: 02/03/2016] [Indexed: 10/22/2022]
Abstract
The discovery of human β-defensin 2 (hBD2), as a Kv1.3 channel inhibitor with the unique molecular mechanism and novel immune modulatory function, suggests that human β-defensins are a novel class of channel ligands. Here, the function and mechanism of the human β-defensin 1 (hBD1) binding to potassium channels was investigated. Based on the structural similarity between hBD1 and Kv1.3 channel-sensitive hBD2, hBD1 was found to selectively inhibit human and mouse Kv1.3 channels with IC50 values of 11.8 ± 3.1 μM and 13.2 ± 4.0 μM, respectively. Different from hBD2 modifying Kv1.3 channel activation and increasing activation time constant, hBD1 did not affect the activation feature of both human and mouse Kv1.3 channels. In comparison with hBD2 simultaneously interacting with the extracellular S1-S2 linker and pore region of Kv1.3 channel, the chimeric channel and mutagenesis experiments showed that hBD1 only bound to the extracellular pore region of Kv1.3 channel instead of extracellular S1-S2 linker or S3-S4 linker. Together, these findings enhance knowledge of hBD1 as a new immune-related Kv1.3 channel blocker and highlight the major functional differences between hBD1 and hBD2 to explore in future research.
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Affiliation(s)
- Jing Feng
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Zili Xie
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Weishan Yang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Yonghui Zhao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Fang Xiang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Zhijian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Wenxin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China
| | - Zongyun Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
| | - Yingliang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China; Center for BioDrug Research, Wuhan University, Wuhan 430072, China.
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22
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Kuzmenkov AI, Grishin EV, Vassilevski AA. Diversity of Potassium Channel Ligands: Focus on Scorpion Toxins. BIOCHEMISTRY (MOSCOW) 2016; 80:1764-99. [DOI: 10.1134/s0006297915130118] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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23
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Wee CL, Ulmschneider MB, Sansom MSP. Membrane/Toxin Interaction Energetics via Serial Multiscale Molecular Dynamics Simulations. J Chem Theory Comput 2015; 6:966-76. [PMID: 26613320 DOI: 10.1021/ct900652s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Computing free energies of complex biomolecular systems via atomistic (AT) molecular dynamics (MD) simulations remains a challenge due to the need for adequate sampling and convergence. Recent coarse-grained (CG) methodology allows simulations of significantly larger systems (∼10(6) to 10(8) atoms) over longer (μs/ms) time scales. Such CG models appear to be capable of making semiquantitative predictions. However, their ability to reproduce accurate thermodynamic quantities remains uncertain. We have recently used CG MD simulations to compute the potential of mean force (PMF) or free energy profile of a small peptide toxin interacting with a lipid bilayer along a 1D reaction coordinate. The toxin studied was VSTx1 (Voltage Sensor Toxin 1) from spider venom which inhibits the archeabacterial voltage-gated potassium (Kv) channel KvAP by binding to the voltage-sensor (VS) domains. Here, we re-estimate this PMF profile using (i) AT MD simulations with explicit membrane and solvent and (ii) an implicit membrane and solvent (generalized Born; GBIM) model where only the peptide was explicit. We used the CG MD free energy simulations to guide the setup of the corresponding AT MD simulations. The aim was to avoid local minima in the AT simulations which would be difficult over shorter AT time scales. A cross-comparison of the PMF profiles revealed a conserved topology, although there were differences in the magnitude of the free energies. The CG and AT simulations predicted a membrane/water interface free energy well of -27 and -23 kcal/mol, respectively (with respect to water). The GBIM model, however, gave a reduced interfacial free energy well (-12 kcal/mol). In addition, the CG and GBIM models predicted a free energy barrier of +61 and +96 kcal/mol, respectively, for positioning the toxin at the center of the bilayer, which was considerably smaller in the AT simulations (+26 kcal/mol). Thus, we present a framework for serially combining CG and AT simulations to estimate the free energy of peptide/membrane interactions. Such approaches for combining simulations at different levels of granularity will become increasingly important in future studies of complex membrane/protein systems.
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Affiliation(s)
- Chze Ling Wee
- Department of Biochemistry and Oxford Centre for Integrative Systems Biology, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Martin B Ulmschneider
- Department of Biochemistry and Oxford Centre for Integrative Systems Biology, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Mark S P Sansom
- Department of Biochemistry and Oxford Centre for Integrative Systems Biology, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
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24
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Computational Studies of Venom Peptides Targeting Potassium Channels. Toxins (Basel) 2015; 7:5194-211. [PMID: 26633507 PMCID: PMC4690127 DOI: 10.3390/toxins7124877] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 11/13/2015] [Accepted: 11/20/2015] [Indexed: 01/18/2023] Open
Abstract
Small peptides isolated from the venom of animals are potential scaffolds for ion channel drug discovery. This review article mainly focuses on the computational studies that have advanced our understanding of how various toxins interfere with the function of K+ channels. We introduce the computational tools available for the study of toxin-channel interactions. We then discuss how these computational tools have been fruitfully applied to elucidate the mechanisms of action of a wide range of venom peptides from scorpions, spiders, and sea anemone.
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25
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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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26
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Gupta K, Zamanian M, Bae C, Milescu M, Krepkiy D, Tilley DC, Sack JT, Yarov-Yarovoy V, Kim JI, Swartz KJ. Tarantula toxins use common surfaces for interacting with Kv and ASIC ion channels. eLife 2015; 4:e06774. [PMID: 25948544 PMCID: PMC4423116 DOI: 10.7554/elife.06774] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/16/2015] [Indexed: 12/14/2022] Open
Abstract
Tarantula toxins that bind to voltage-sensing domains of voltage-activated ion channels are thought to partition into the membrane and bind to the channel within the bilayer. While no structures of a voltage-sensor toxin bound to a channel have been solved, a structural homolog, psalmotoxin (PcTx1), was recently crystalized in complex with the extracellular domain of an acid sensing ion channel (ASIC). In the present study we use spectroscopic, biophysical and computational approaches to compare membrane interaction properties and channel binding surfaces of PcTx1 with the voltage-sensor toxin guangxitoxin (GxTx-1E). Our results show that both types of tarantula toxins interact with membranes, but that voltage-sensor toxins partition deeper into the bilayer. In addition, our results suggest that tarantula toxins have evolved a similar concave surface for clamping onto α-helices that is effective in aqueous or lipidic physical environments.
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Affiliation(s)
- Kanchan Gupta
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Maryam Zamanian
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Chanhyung Bae
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Mirela Milescu
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
- Biology Division, University of Missouri, Columbia, United States
| | - Dmitriy Krepkiy
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Drew C Tilley
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Jae Il Kim
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea
| | - Kenton J Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Health, Bethesda, United States
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
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27
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Structural interactions of a voltage sensor toxin with lipid membranes. Proc Natl Acad Sci U S A 2014; 111:E5463-70. [PMID: 25453087 DOI: 10.1073/pnas.1415324111] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein toxins from tarantula venom alter the activity of diverse ion channel proteins, including voltage, stretch, and ligand-activated cation channels. Although tarantula toxins have been shown to partition into membranes, and the membrane is thought to play an important role in their activity, the structural interactions between these toxins and lipid membranes are poorly understood. Here, we use solid-state NMR and neutron diffraction to investigate the interactions between a voltage sensor toxin (VSTx1) and lipid membranes, with the goal of localizing the toxin in the membrane and determining its influence on membrane structure. Our results demonstrate that VSTx1 localizes to the headgroup region of lipid membranes and produces a thinning of the bilayer. The toxin orients such that many basic residues are in the aqueous phase, all three Trp residues adopt interfacial positions, and several hydrophobic residues are within the membrane interior. One remarkable feature of this preferred orientation is that the surface of the toxin that mediates binding to voltage sensors is ideally positioned within the lipid bilayer to favor complex formation between the toxin and the voltage sensor.
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28
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Jingzhaotoxin-35, a novel gating-modifier toxin targeting both Nav1.5 and Kv2.1 channels. Toxicon 2014; 92:90-6. [DOI: 10.1016/j.toxicon.2014.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 10/02/2014] [Accepted: 10/07/2014] [Indexed: 11/24/2022]
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29
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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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30
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Abstract
SNX-482, a peptide toxin isolated from tarantula venom, has become widely used as an inhibitor of Cav2.3 voltage-gated calcium channels. Unexpectedly, we found that SNX-482 dramatically reduced the A-type potassium current in acutely dissociated dopamine neurons from mouse substantia nigra pars compacta. The inhibition persisted when calcium was replaced by cobalt, showing that it was not secondary to a reduction of calcium influx. Currents from cloned Kv4.3 channels expressed in HEK-293 cells were inhibited by SNX-482 with an IC50 of <3 nM, revealing substantially greater potency than for SNX-482 inhibition of Cav2.3 channels (IC50 20-60 nM). At sub-saturating concentrations, SNX-482 produced a depolarizing shift in the voltage dependence of activation of Kv4.3 channels and slowed activation kinetics. Similar effects were seen on gating of cloned Kv4.2 channels, but the inhibition was less pronounced and required higher toxin concentrations. These results reveal SNX-482 as the most potent inhibitor of Kv4.3 channels yet identified. Because of the effects on both Kv4.3 and Kv4.2 channels, caution is needed when interpreting the effects of SNX-482 on cells and circuits where these channels are present.
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31
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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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32
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Nguyen TTN, Folch B, Létourneau M, Truong NH, Doucet N, Fournier A, Chatenet D. Design of a truncated cardiotoxin-I analogue with potent insulinotropic activity. J Med Chem 2014; 57:2623-33. [PMID: 24552570 DOI: 10.1021/jm401904q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Insulin secretion by pancreatic β-cells in response to glucose or other secretagogues is tightly coupled to membrane potential. Various studies have highlighted the prospect of enhancing insulin secretion in a glucose-dependent manner by blocking voltage-gated potassium channels (K(v)) and calcium-activated potassium channels (K(Ca)). Such strategy is expected to present a lower risk for hypoglycemic events compared to KATP channel blockers. Our group recently reported the discovery of a new insulinotropic agent, cardiotoxin-I (CTX-I), from the Naja kaouthia snake venom. In the present study, we report the design and synthesis of [Lys(52)]CTX-I(41-60) via structure-guided modification, a truncated, equipotent analogue of CTX-I, and demonstrate, using various pharmacological inhibitors, that this derivative probably exerts its action through Kv channels. This new analogue could represent a useful pharmacological tool to study β-cell physiology or even open a new therapeutic avenue for the treatment of type 2 diabetes.
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Affiliation(s)
- Thi Tuyet Nhung Nguyen
- INRS-Institut Armand-Frappier , Université du Québec , 531 Boulevard des Prairies Ville de Laval, Québec H7 V 1B7, Québec Canada
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33
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Gui J, Liu B, Cao G, Lipchik AM, Perez M, Dekan Z, Mobli M, Daly NL, Alewood PF, Parker LL, King GF, Zhou Y, Jordt SE, Nitabach MN. A tarantula-venom peptide antagonizes the TRPA1 nociceptor ion channel by binding to the S1-S4 gating domain. Curr Biol 2014; 24:473-83. [PMID: 24530065 DOI: 10.1016/j.cub.2014.01.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/22/2013] [Accepted: 01/08/2014] [Indexed: 01/01/2023]
Abstract
BACKGROUND The venoms of predators have been an excellent source of diverse highly specific peptides targeting ion channels. Here we describe the first known peptide antagonist of the nociceptor ion channel transient receptor potential ankyrin 1 (TRPA1). RESULTS We constructed a recombinant cDNA library encoding ∼100 diverse GPI-anchored peptide toxins (t-toxins) derived from spider venoms and screened this library by coexpression in Xenopus oocytes with TRPA1. This screen resulted in identification of protoxin-I (ProTx-I), a 35-residue peptide from the venom of the Peruvian green-velvet tarantula, Thrixopelma pruriens, as the first known high-affinity peptide TRPA1 antagonist. ProTx-I was previously identified as an antagonist of voltage-gated sodium (NaV) channels. We constructed a t-toxin library of ProTx-I alanine-scanning mutants and screened this library against NaV1.2 and TRPA1. This revealed distinct partially overlapping surfaces of ProTx-I by which it binds to these two ion channels. Importantly, this mutagenesis yielded two novel ProTx-I variants that are only active against either TRPA1or NaV1.2. By testing its activity against chimeric channels, we identified the extracellular loops of the TRPA1 S1-S4 gating domain as the ProTx-I binding site. CONCLUSIONS These studies establish our approach, which we term "toxineering," as a generally applicable method for isolation of novel ion channel modifiers and design of ion channel modifiers with altered specificity. They also suggest that ProTx-I will be a valuable pharmacological reagent for addressing biophysical mechanisms of TRPA1 gating and the physiology of TRPA1 function in nociceptors, as well as for potential clinical application in the context of pain and inflammation.
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Affiliation(s)
- Junhong Gui
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Genetics, Yale School of Medicine, New Haven, CT 06520, USA; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, CT 06520, USA
| | - Boyi Liu
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Guan Cao
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Genetics, Yale School of Medicine, New Haven, CT 06520, USA; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, CT 06520, USA
| | - Andrew M Lipchik
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA
| | - Minervo Perez
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA
| | - Zoltan Dekan
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Norelle L Daly
- Centre for Biodiscovery and Molecular Development of Therapeutics, Queensland Tropical Health Alliance, James Cook University, Cairns, QLD 4870, Australia
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Laurie L Parker
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yufeng Zhou
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Sven-Eric Jordt
- Department of Pharmacology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Michael N Nitabach
- Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA; Department of Genetics, Yale School of Medicine, New Haven, CT 06520, USA; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale School of Medicine, New Haven, CT 06520, USA.
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34
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Chen M, Li J, Zhang F, Liu Z. Isolation and characterization of SsmTx-I, a Specific Kv2.1 blocker from the venom of the centipede Scolopendra Subspinipes Mutilans
L. Koch. J Pept Sci 2014; 20:159-64. [DOI: 10.1002/psc.2588] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/20/2013] [Accepted: 10/21/2013] [Indexed: 01/24/2023]
Affiliation(s)
- Minzhi Chen
- College of Life Science; Hunan Normal University; Changsha 410081 China
| | - Jing Li
- College of Life Science; Hunan Normal University; Changsha 410081 China
| | - Fan Zhang
- College of Life Science; Hunan Normal University; Changsha 410081 China
| | - Zhonghua Liu
- College of Life Science; Hunan Normal University; Changsha 410081 China
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35
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Tao H, Chen JJ, Xiao YC, Wu YY, Su HB, Li D, Wang HY, Deng MC, Wang MC, Liu ZH, Liang SP. Analysis of the Interaction of Tarantula Toxin Jingzhaotoxin-III (β-TRTX-Cj1α) with the Voltage Sensor of Kv2.1 Uncovers the Molecular Basis for Cross-Activities on Kv2.1 and Nav1.5 Channels. Biochemistry 2013; 52:7439-48. [DOI: 10.1021/bi4006418] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Huai Tao
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
- Department
of Biochemistry and Molecular Biology, Hunan University of Chinese Medicine, Changsha, Hunan 410208, China
| | - Jin J. Chen
- College
of Biology Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Yu C. Xiao
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Yuan Y. Wu
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Hai B Su
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Dan Li
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Heng Y. Wang
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Mei C. Deng
- Department
of Biochemistry, School of Biological Science and Technology, Central South University, Changsha, Hunan 410013, China
| | - Mei C. Wang
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Zhong H. Liu
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
| | - Song P. Liang
- Key
Laboratory of Protein Chemistry and Developmental Biology of Ministry
of Education, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, China
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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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37
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Minassian NA, Gibbs A, Shih AY, Liu Y, Neff RA, Sutton SW, Mirzadegan T, Connor J, Fellows R, Husovsky M, Nelson S, Hunter MJ, Flinspach M, Wickenden AD. Analysis of the structural and molecular basis of voltage-sensitive sodium channel inhibition by the spider toxin huwentoxin-IV (μ-TRTX-Hh2a). J Biol Chem 2013; 288:22707-20. [PMID: 23760503 DOI: 10.1074/jbc.m113.461392] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are essential to the normal function of the vertebrate nervous system. Aberrant function of VGSCs underlies a variety of disorders, including epilepsy, arrhythmia, and pain. A large number of animal toxins target these ion channels and may have significant therapeutic potential. Most of these toxins, however, have not been characterized in detail. Here, by combining patch clamp electrophysiology and radioligand binding studies with peptide mutagenesis, NMR structure determination, and molecular modeling, we have revealed key molecular determinants of the interaction between the tarantula toxin huwentoxin-IV and two VGSC isoforms, Nav1.7 and Nav1.2. Nine huwentoxin-IV residues (F6A, P11A, D14A, L22A, S25A, W30A, K32A, Y33A, and I35A) were important for block of Nav1.7 and Nav1.2. Importantly, molecular dynamics simulations and NMR studies indicated that folding was normal for several key mutants, suggesting that these amino acids probably make specific interactions with sodium channel residues. Additionally, we identified several amino acids (F6A, K18A, R26A, and K27A) that are involved in isoform-specific VGSC interactions. Our structural and functional data were used to model the docking of huwentoxin-IV into the domain II voltage sensor of Nav1.7. The model predicts that a hydrophobic patch composed of Trp-30 and Phe-6, along with the basic Lys-32 residue, docks into a groove formed by the Nav1.7 S1-S2 and S3-S4 loops. These results provide new insight into the structural and molecular basis of sodium channel block by huwentoxin-IV and may provide a basis for the rational design of toxin-based peptides with improved VGSC potency and/or selectivity.
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Affiliation(s)
- Natali A Minassian
- Department of Neuroscience Discovery, Janssen Research & Development, LLC, San Diego, California 92121, USA
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Synthesis and biological characterization of synthetic analogs of Huwentoxin-IV (Mu-theraphotoxin-Hh2a), a neuronal tetrodotoxin-sensitive sodium channel inhibitor. Toxicon 2013; 71:57-65. [PMID: 23726857 DOI: 10.1016/j.toxicon.2013.05.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 05/12/2013] [Accepted: 05/15/2013] [Indexed: 11/22/2022]
Abstract
Huwentoxin-IV (HWTX-IV, also named Mu-theraphotoxin-Hh2a) is a typical inhibitor cystine knot peptide isolated from the venom of Chinese tarantula Ornithoctonus huwena and is found to inhibit tetrodotoxin-sensitive (TTX-S) sodium channels from mammalian sensory neurons. This peptide binds to neurotoxin receptor site 4 located at the extracellular S3-S4 linker of domain II in neuronal sodium channels. However, the molecular surface of HWTX-IV interaction with sodium channels remains unknown. In this study, we synthesized HWTX-IV and three mutants (T28D, R29A and Q34D) and characterized their functions on TTX-S sodium channels from adult rat dorsal root ganglion (DRG) neurons. Analysis of liquid chromatography, mass spectrometry and circular dichroism spectrum indicated that all four synthetic peptides are properly folded. Synthetic HWTX-IV exhibited the same activity as native HWTX-IV, while three mutations reduced toxin binding affinities by 10-200 fold, indicating that the basic or vicinal polar residues Thr²⁸, Arg²⁹, and Gln³⁴ in C-terminus might play critical roles in the interaction of HWTX-IV with TTX-S sodium channels.
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39
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Gordon D, Chen R, Chung SH. Computational methods of studying the binding of toxins from venomous animals to biological ion channels: theory and applications. Physiol Rev 2013; 93:767-802. [PMID: 23589832 PMCID: PMC3768100 DOI: 10.1152/physrev.00035.2012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The discovery of new drugs that selectively block or modulate ion channels has great potential to provide new treatments for a host of conditions. One promising avenue revolves around modifying or mimicking certain naturally occurring ion channel modulator toxins. This strategy appears to offer the prospect of designing drugs that are both potent and specific. The use of computational modeling is crucial to this endeavor, as it has the potential to provide lower cost alternatives for exploring the effects of new compounds on ion channels. In addition, computational modeling can provide structural information and theoretical understanding that is not easily derivable from experimental results. In this review, we look at the theory and computational methods that are applicable to the study of ion channel modulators. The first section provides an introduction to various theoretical concepts, including force-fields and the statistical mechanics of binding. We then look at various computational techniques available to the researcher, including molecular dynamics, brownian dynamics, and molecular docking systems. The latter section of the review explores applications of these techniques, concentrating on pore blocker and gating modifier toxins of potassium and sodium channels. After first discussing the structural features of these channels, and their modes of block, we provide an in-depth review of past computational work that has been carried out. Finally, we discuss prospects for future developments in the field.
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Affiliation(s)
- Dan Gordon
- Research School of Biology, The Australian National University, Acton, ACT 0200, Australia.
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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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Molecular determinants for the tarantula toxin jingzhaotoxin-I interacting with potassium channel Kv2.1. Toxicon 2012; 63:129-36. [PMID: 23246579 DOI: 10.1016/j.toxicon.2012.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 12/01/2012] [Accepted: 12/05/2012] [Indexed: 11/24/2022]
Abstract
With high binding affinity and distinct pharmacological functions, animal toxins are powerful ligands to investigate the structure-function relationships of voltage-gated ion channels. Jingzhaotoxin-I (JZTX-I) is an important neurotoxin from the tarantula Chilobrachys jingzhao venom that inhibits both sodium and potassium channels. In our previous work, JZTX-I, as a gating modifier, is able to inhibit activation of the potassium channel subtype Kv2.1. However, its binding site on Kv2.1 remains unknown. In this study, using Ala-scanning mutagenesis strategy, we demonstrated that four residues (I273, F274, E277, and K280) in S3b-S4 motif contributed to the formation of JZTX-I binding site. The mutations I273A, F274A, E277A, and K280A reduced toxin binding affinity by 6-, 10-, 8-, and 7-fold, respectively. Taken together with our previous data that JZTX-I accelerated channel deactivation, these results suggest that JZTX-I inhibits Kv2.1 activation by docking onto the voltage sensor paddle and trapping the voltage sensor in the closed state.
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Bae C, Kalia J, Song I, Yu J, Kim HH, Swartz KJ, Kim JI. High yield production and refolding of the double-knot toxin, an activator of TRPV1 channels. PLoS One 2012; 7:e51516. [PMID: 23240036 PMCID: PMC3519854 DOI: 10.1371/journal.pone.0051516] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 10/24/2012] [Indexed: 11/19/2022] Open
Abstract
A unique peptide toxin, named double-knot toxin (DkTx), was recently purified from the venom of the tarantula Ornithoctonus huwena and was found to stably activate TRPV1 channels by targeting the outer pore domain. DkTx has been shown to consist of two inhibitory cysteine-knot (ICK) motifs, referred to as K1 and K2, each containing six cysteine residues. Beyond this initial characterization, however, the structural and functional details about DkTx remains elusive in large part due to the lack of a high yielding methodology for the synthesis and folding of this cysteine-rich peptide. Here, we overcome this obstacle by generating pure DkTx in quantities sufficient for structural and functional analyses. Our methodology entails expression of DkTx in E. coli followed by oxidative folding of the isolated linear peptide. Upon screening of various oxidative conditions for optimizing the folding yield of the toxin, we observed that detergents were required for efficient folding of the linear peptide. Our synthetic DkTx co-eluted with the native toxin on HPLC, and irreversibly activated TRPV1 in a manner identical to native DkTx. Interestingly, we find that DkTx has two interconvertible conformations present in a 1∶6 ratio at equilibrium. Kinetic analysis of DkTx folding suggests that the K1 and K2 domains influence each other during the folding process. Moreover, the CD spectra of the toxins shows that the secondary structures of K1 and K2 remains intact even after separating the two knots. These findings provide a starting point for detailed studies on the structural and functional characterization of DkTx and utilization of this toxin as a tool to explore the elusive mechanisms underlying the polymodal gating of TRPV1.
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Affiliation(s)
- Chanhyung Bae
- School of Life Science, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Jeet Kalia
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Inhye Song
- School of Life Science, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - JeongHeon Yu
- School of Life Science, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Ha Hyung Kim
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
| | - Kenton J. Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jae Il Kim
- School of Life Science, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
- * E-mail:
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43
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Nguyen TTN, Folch B, Létourneau M, Vaudry D, Truong NH, Doucet N, Chatenet D, Fournier A. Cardiotoxin-I: an unexpectedly potent insulinotropic agent. Chembiochem 2012; 13:1805-12. [PMID: 22807058 DOI: 10.1002/cbic.201200081] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Indexed: 12/17/2022]
Abstract
Insulin secretion from pancreatic β-cells is a complex process, involving the integration and interaction of multiple external and internal stimuli, in which glucose plays a major role. Understanding the physiology leading to insulin release is a crucial step toward the identification of new targets. In this study, we evaluated the presence of insulinotropic metabolites in Naja kaouthia snake venom. Only one fraction, identified as cardiotoxin-I (CTX-I) was able to induce insulin secretion from INS-1E cells without affecting cell viability and integrity, as assessed by MTT and LDH assays. Interestingly, CTX-I was also able to stimulate insulin secretion from INS-1E cells even in the absence of glucose. Although cardiotoxins have been characterized as potent hemolytic agents and vasoconstrictors, CTX-I was unable to induce direct hemolysis of human erythrocytes or to induce potent vasoconstriction. As such, this newly identified insulin-releasing toxin will surely enrich the pool of existing tools to study β-cell physiology or even open a new therapeutic avenue.
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Affiliation(s)
- Thi Tuyet Nhung Nguyen
- INRS-Institut Armand-Frappier, Université du Québec, 531 Boulevard des Prairies, Ville de Laval, Québec H7V 1B7, Canada
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44
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Lee CW, Bae C, Lee J, Ryu JH, Kim HH, Kohno T, Swartz KJ, Kim JI. Solution structure of kurtoxin: a gating modifier selective for Cav3 voltage-gated Ca(2+) channels. Biochemistry 2012; 51:1862-73. [PMID: 22329781 PMCID: PMC3295331 DOI: 10.1021/bi201633j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kurtoxin is a 63-amino acid polypeptide isolated from the venom of the South African scorpion Parabuthus transvaalicus. It is the first and only peptide ligand known to interact with Cav3 (T-type) voltage-gated Ca(2+) channels with high affinity and to modify the voltage-dependent gating of these channels. Here we describe the nuclear magnetic resonance (NMR) solution structure of kurtoxin determined using two- and three-dimensional NMR spectroscopy with dynamical simulated annealing calculations. The molecular structure of the toxin was highly similar to those of scorpion α-toxins and contained an α-helix, three β-strands, and several turns stabilized by four disulfide bonds. This so-called "cysteine-stabilized α-helix and β-sheet (CSαβ)" motif is found in a number of functionally varied small proteins. A detailed comparison of the backbone structure of kurtoxin with those of the scorpion α-toxins revealed that three regions [first long loop (Asp(8)-Ile(15)), β-hairpin loop (Gly(39)-Leu(42)), and C-terminal segment (Arg(57)-Ala(63))] in kurtoxin significantly differ from the corresponding regions in scorpion α-toxins, suggesting that these regions may be important for interacting with Cav3 (T-type) Ca(2+) channels. In addition, the surface profile of kurtoxin shows a larger and more focused electropositive patch along with a larger hydrophobic surface compared to those seen on scorpion α-toxins. These distinct surface properties of kurtoxin could explain its binding to Cav3 (T-type) voltage-gated Ca(2+) channels.
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Affiliation(s)
- Chul Won Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
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45
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Kozminsky-Atias A, Zilberberg N. Molding the business end of neurotoxins by diversifying evolution. FASEB J 2011; 26:576-86. [PMID: 22009937 DOI: 10.1096/fj.11-187179] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A diverse range of organisms utilize neurotoxins that target specific ion channels and modulate their activity. Typically, toxins are clustered into several multigene families, providing an organism with the upper hand in the never-ending predator-prey arms race. Several gene families, including those encoding certain neurotoxins, have been subject to diversifying selection forces, resulting in rapid gene evolution. Here we sought a spatial pattern in the distribution of both diversifying and purifying selection forces common to neurotoxin gene families. Utilizing the mechanistic empirical combination model, we analyzed various toxin families from different phyla affecting various receptors and relying on diverse modes of action. Through this approach, we were able to detect clear correlations between the pharmacological surface of a toxin and rapidly evolving domains, rich in positively selected residues. On the other hand, patches of negatively selected residues were restricted to the nontoxic face of the molecule and most likely help in stabilizing the tertiary structure of the toxin. We thus propose a mutual evolutionary strategy of venomous animals in which adaptive molecular evolution is directed toward the toxin active surface. Furthermore, we propose that the binding domains of unstudied toxins could be readily predicted using evolutionary considerations.
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Affiliation(s)
- Adi Kozminsky-Atias
- Department of Life Sciences, Ben Gurion University of the Negev, Beer-Sheva, Israel
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46
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Rong M, Chen J, Tao H, Wu Y, Jiang P, Lu M, Su H, Chi Y, Cai T, Zhao L, Zeng X, Xiao Y, Liang S. Molecular basis of the tarantula toxin jingzhaotoxin-III (β-TRTX-Cj1α) interacting with voltage sensors in sodium channel subtype Nav1.5. FASEB J 2011; 25:3177-85. [PMID: 21665957 DOI: 10.1096/fj.10-178848] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
With conserved structural scaffold and divergent electrophysiological functions, animal toxins are considered powerful tools for investigating the basic structure-function relationship of voltage-gated sodium channels. Jingzhaotoxin-III (β-TRTX-Cj1α) is a unique sodium channel gating modifier from the tarantula Chilobrachys jingzhao, because the toxin can selectively inhibit the activation of cardiac sodium channel but not neuronal subtypes. However, the molecular basis of JZTX-III interaction with sodium channels remains unknown. In this study, we showed that JZTX-III was efficiently expressed by the secretory pathway in yeast. Alanine-scanning analysis indicated that 2 acidic residues (Asp1, Glu3) and an exposed hydrophobic patch, formed by 4 Trp residues (residues 8, 9, 28 and 30), play important roles in the binding of JZTX-III to Nav1.5. JZTX-III docked to the Nav1.5 DIIS3-S4 linker. Mutations S799A, R800A, and L804A could additively reduce toxin sensitivity of Nav1.5. We also demonstrated that the unique Arg800, not emerging in other sodium channel subtypes, is responsible for JZTX-III selectively interacting with Nav1.5. The reverse mutation D816R in Nav1.7 greatly increased the sensitivity of the neuronal subtype to JZTX-III. Conversely, the mutation R800D in Nav1.5 decreased JZTX-III's IC₅₀ by 72-fold. Therefore, our results indicated that JZTX-III is a site 4 toxin, but does not possess the same critical residues on sodium channels as other site 4 toxins. Our data also revealed the underlying mechanism for JZTX-III to be highly specific for the cardiac sodium channel.
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Affiliation(s)
- Mingqiang Rong
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha, China
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47
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Jung HH, Jung HJ, Milescu M, Lee CW, Lee S, Lee JY, Eu YJ, Kim HH, Swartz KJ, Kim JI. Structure and orientation of a voltage-sensor toxin in lipid membranes. Biophys J 2010; 99:638-46. [PMID: 20643084 DOI: 10.1016/j.bpj.2010.04.061] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 04/16/2010] [Accepted: 04/20/2010] [Indexed: 10/19/2022] Open
Abstract
Amphipathic protein toxins from tarantula venom inhibit voltage-activated potassium (Kv) channels by binding to a critical helix-turn-helix motif termed the voltage sensor paddle. Although these toxins partition into membranes to bind the paddle motif, their structure and orientation within the membrane are unknown. We investigated the interaction of a tarantula toxin named SGTx with membranes using both fluorescence and NMR spectroscopy. Depth-dependent fluorescence-quenching experiments with brominated lipids suggest that Trp30 in SGTx is positioned approximately 9 A from the center of the bilayer. NMR spectra reveal that the inhibitor cystine knot structure of the toxin does not radically change upon membrane partitioning. Transferred cross-saturation NMR experiments indicate that the toxin's hydrophobic protrusion contacts the hydrophobic core of the membrane, whereas most surrounding polar residues remain at interfacial regions of the bilayer. The inferred orientation of the toxin reveals a twofold symmetry in the arrangement of basic and hydrophobic residues, a feature that is conserved among tarantula toxins. These results have important implications for regions of the toxin involved in recognizing membranes and voltage-sensor paddles, and for the mechanisms by which tarantula toxins alter the activity of different types of ion channels.
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Affiliation(s)
- Hyun Ho Jung
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, Korea
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48
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Lee S, Milescu M, Jung HH, Lee JY, Bae CH, Lee CW, Kim HH, Swartz KJ, Kim JI. Solution structure of GxTX-1E, a high-affinity tarantula toxin interacting with voltage sensors in Kv2.1 potassium channels . Biochemistry 2010; 49:5134-42. [PMID: 20509680 DOI: 10.1021/bi100246u] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
GxTX-1E is a neurotoxin recently isolated from Plesiophrictus guangxiensis venom that inhibits the Kv2.1 channel in pancreatic beta-cells. The sequence of the toxin is related to those of previously studied tarantula toxins that interact with the voltage sensors in Kv channels, and GxTX-1E interacts with the Kv2.1 channel with unusually high affinity, making it particularly useful for structural and mechanistic studies. Here we determined the three-dimensional solution structure of GxTX-1E using NMR spectroscopy and compared it to that of several related tarantula toxins. The molecular structure of GxTX-1E is similar to those of tarantula toxins that target voltage sensors in Kv channels in that it contains an ICK motif, composed of beta-strands, and contains a prominent cluster of solvent-exposed hydrophobic residues surrounded by polar residues. When compared with the structure of SGTx1, a toxin for which mutagenesis data are available, the residue compositions of the two toxins are distinct in regions that are critical for activity, suggesting that their modes of binding to voltage sensors may be different. Interestingly, the structural architecture of GxTX-1E is also similar to that of JZTX-III, a tarantula toxin that interacts with Kv2.1 with low affinity. The most striking structural differences between GxTX-1E and JZTX-III are found in the orientation between the first and second cysteine loops and the C-terminal region of the toxins, suggesting that these regions of GxTX-1E are responsible for its high affinity.
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Affiliation(s)
- Seungkyu Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, South Korea
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49
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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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50
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Edgerton GB, Blumenthal KM, Hanck DA. Inhibition of the activation pathway of the T-type calcium channel Ca(V)3.1 by ProTxII. Toxicon 2010; 56:624-36. [PMID: 20600227 DOI: 10.1016/j.toxicon.2010.06.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 06/12/2010] [Accepted: 06/15/2010] [Indexed: 11/18/2022]
Abstract
Toxins have been used extensively to probe the gating mechanisms of voltage-gated ion channels. Relatively few such tools are available to study the low-voltage activated T-type Ca channels, which underlie thalamic neuron firing and affect sleep, resistance to seizures, and weight gain. Here we show that ProTxII, a peptide toxin recently isolated from the venom of the tarantula spider Thrixopelma pruriens, dose-dependently inhibited Ca(V)3.1 causing a decrease in current (81.6% +/- 3.1% at -30 mV in 5 microM toxin) and a positive shift in the voltage range of activation (+34.5 mV +/- 4.4 mV). Toxin-modified currents were slower to activate and faster to deactivate and they displayed a longer lag in the onset of current, i.e. the Cole-Moore shift, consistent with the inhibition of gating transitions along the activation pathway, particularly the final opening transition. Single-channel current amplitude and total gating charge were unaffected by toxin, ruling out a change in ion flux or channel dropout as mechanisms for the decrease in macroscopic conductance. A positive shift in the voltage range of gating charge movement (+30.6 mV +/- 2.6 mV shift in the voltage of half maximal charge movement in the presence of 5 microM toxin) confirmed that ProTxII-induced gating perturbations in this channel occur at the level of the voltage sensors, and kinetic modeling based on these findings suggested that reductions in current magnitude could be largely accounted for by kinetic perturbations of activation.
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Affiliation(s)
- Gabrielle B Edgerton
- Committee on Neurobiology, University of Chicago, 5841 S. Maryland Avenue, MC6094, Chicago, IL 60637, USA
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