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Groome JR. Historical Perspective of the Characterization of Conotoxins Targeting Voltage-Gated Sodium Channels. Mar Drugs 2023; 21:md21040209. [PMID: 37103349 PMCID: PMC10142487 DOI: 10.3390/md21040209] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 03/21/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023] Open
Abstract
Marine toxins have potent actions on diverse sodium ion channels regulated by transmembrane voltage (voltage-gated ion channels) or by neurotransmitters (nicotinic acetylcholine receptor channels). Studies of these toxins have focused on varied aspects of venom peptides ranging from evolutionary relationships of predator and prey, biological actions on excitable tissues, potential application as pharmacological intervention in disease therapy, and as part of multiple experimental approaches towards an understanding of the atomistic characterization of ion channel structure. This review examines the historical perspective of the study of conotoxin peptides active on sodium channels gated by transmembrane voltage, which has led to recent advances in ion channel research made possible with the exploitation of the diversity of these marine toxins.
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Affiliation(s)
- James R Groome
- Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA
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2
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Voltage-Gated Sodium Channels: A Prominent Target of Marine Toxins. Mar Drugs 2021; 19:md19100562. [PMID: 34677461 PMCID: PMC8537899 DOI: 10.3390/md19100562] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 09/29/2021] [Accepted: 10/02/2021] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are considered to be one of the most important ion channels given their remarkable physiological role. VGSCs constitute a family of large transmembrane proteins that allow transmission, generation, and propagation of action potentials. This occurs by conducting Na+ ions through the membrane, supporting cell excitability and communication signals in various systems. As a result, a wide range of coordination and physiological functions, from locomotion to cognition, can be accomplished. Drugs that target and alter the molecular mechanism of VGSCs’ function have highly contributed to the discovery and perception of the function and the structure of this channel. Among those drugs are various marine toxins produced by harmful microorganisms or venomous animals. These toxins have played a key role in understanding the mode of action of VGSCs and in mapping their various allosteric binding sites. Furthermore, marine toxins appear to be an emerging source of therapeutic tools that can relieve pain or treat VGSC-related human channelopathies. Several studies documented the effect of marine toxins on VGSCs as well as their pharmaceutical applications, but none of them underlined the principal marine toxins and their effect on VGSCs. Therefore, this review aims to highlight the neurotoxins produced by marine animals such as pufferfish, shellfish, sea anemone, and cone snail that are active on VGSCs and discuss their pharmaceutical values.
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3
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Zhorov BS. Structure of Sodium and Calcium Channels
with Ligands. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021020150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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McArthur JR, Munasinghe NR, Finol-Urdaneta RK, Adams DJ, Christie MJ. Spider Venom Peptide Pn3a Inhibition of Primary Afferent High Voltage-Activated Calcium Channels. Front Pharmacol 2021; 11:633679. [PMID: 33584315 PMCID: PMC7875911 DOI: 10.3389/fphar.2020.633679] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 12/30/2020] [Indexed: 11/19/2022] Open
Abstract
Despite potently inhibiting the nociceptive voltage-gated sodium (Nav) channel, Nav1.7, µ-theraphotoxin Pn3a is antinociceptive only upon co-administration with sub-therapeutic opioid agonists, or by itself at doses >3,000-fold greater than its Nav1.7 IC50 by a yet undefined mechanism. Nav channels are structurally related to voltage-gated calcium (Cav) channels, Cav1 and Cav2. These channels mediate the high voltage-activated (HVA) calcium currents (ICa) that orchestrate synaptic transmission in nociceptive dorsal root ganglion (DRG) neurons and are fine-tuned by opioid receptor (OR) activity. Using whole-cell patch clamp recording, we found that Pn3a (10 µM) inhibits ∼55% of rat DRG neuron HVA-ICa and 60–80% of Cav1.2, Cav1.3, Cav2.1, and Cav2.2 mediated currents in HEK293 cells, with no inhibition of Cav2.3. As a major DRG ICa component, Cav2.2 inhibition by Pn3a (IC50 = 3.71 ± 0.21 µM) arises from an 18 mV hyperpolarizing shift in the voltage dependence of inactivation. We observed that co-application of Pn3a and µ-OR agonist DAMGO results in enhanced HVA-ICa inhibition in DRG neurons whereas co-application of Pn3a with the OR antagonist naloxone does not, underscoring HVA channels as shared targets of Pn3a and opioids. We provide evidence that Pn3a inhibits native and recombinant HVA Cavs at previously reportedly antinociceptive concentrations in animal pain models. We show additive modulation of DRG HVA-ICa by sequential application of low Pn3a doses and sub-therapeutic opioids ligands. We propose Pn3a's antinociceptive effects result, at least in part, from direct inhibition of HVA-ICa at high Pn3a doses, or through additive inhibition by low Pn3a and mild OR activation.
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Affiliation(s)
- Jeffrey R McArthur
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Nehan R Munasinghe
- Discipline of Pharmacology, University of Sydney, Sydney, NSW, Australia
| | - Rocio K Finol-Urdaneta
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia.,Electrophysiology Facility for Cell Phenotyping and Drug Discovery, IHMRI, Wollongong, NSW, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
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5
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Finol-Urdaneta RK, McArthur JR, Korkosh VS, Huang S, McMaster D, Glavica R, Tikhonov DB, Zhorov BS, French RJ. Extremely Potent Block of Bacterial Voltage-Gated Sodium Channels by µ-Conotoxin PIIIA. Mar Drugs 2019; 17:md17090510. [PMID: 31470595 PMCID: PMC6780087 DOI: 10.3390/md17090510] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 08/13/2019] [Accepted: 08/24/2019] [Indexed: 12/15/2022] Open
Abstract
µ-Conotoxin PIIIA, in the sub-picomolar, range inhibits the archetypal bacterial sodium channel NaChBac (NavBh) in a voltage- and use-dependent manner. Peptide µ-conotoxins were first recognized as potent components of the venoms of fish-hunting cone snails that selectively inhibit voltage-gated skeletal muscle sodium channels, thus preventing muscle contraction. Intriguingly, computer simulations predicted that PIIIA binds to prokaryotic channel NavAb with much higher affinity than to fish (and other vertebrates) skeletal muscle sodium channel (Nav 1.4). Here, using whole-cell voltage clamp, we demonstrate that PIIIA inhibits NavBac mediated currents even more potently than predicted. From concentration-response data, with [PIIIA] varying more than 6 orders of magnitude (10−12 to 10−5 M), we estimated an IC50 = ~5 pM, maximal block of 0.95 and a Hill coefficient of 0.81 for the inhibition of peak currents. Inhibition was stronger at depolarized holding potentials and was modulated by the frequency and duration of the stimulation pulses. An important feature of the PIIIA action was acceleration of macroscopic inactivation. Docking of PIIIA in a NaChBac (NavBh) model revealed two interconvertible binding modes. In one mode, PIIIA sterically and electrostatically blocks the permeation pathway. In a second mode, apparent stabilization of the inactivated state was achieved by PIIIA binding between P2 helices and trans-membrane S5s from adjacent channel subunits, partially occluding the outer pore. Together, our experimental and computational results suggest that, besides blocking the channel-mediated currents by directly occluding the conducting pathway, PIIIA may also change the relative populations of conducting (activated) and non-conducting (inactivated) states.
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Affiliation(s)
- Rocio K Finol-Urdaneta
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia.
- Department of Biochemistry, Brandeis University, Waltham, MA 0254-9110, USA.
| | - Jeffrey R McArthur
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Vyacheslav S Korkosh
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg 194223, Russia
| | - Sun Huang
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Denis McMaster
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Robert Glavica
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Denis B Tikhonov
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg 194223, Russia
| | - Boris S Zhorov
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg 194223, Russia
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 4K1, Canada
| | - Robert J French
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
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6
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Paul George AA, Heimer P, Leipold E, Schmitz T, Kaufmann D, Tietze D, Heinemann SH, Imhof D. Effect of Conformational Diversity on the Bioactivity of µ-Conotoxin PIIIA Disulfide Isomers. Mar Drugs 2019; 17:E390. [PMID: 31269696 PMCID: PMC6669574 DOI: 10.3390/md17070390] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 06/21/2019] [Accepted: 06/25/2019] [Indexed: 12/25/2022] Open
Abstract
Cyclic µ-conotoxin PIIIA, a potent blocker of skeletal muscle voltage-gated sodium channel NaV1.4, is a 22mer peptide stabilized by three disulfide bonds. Combining electrophysiological measurements with molecular docking and dynamic simulations based on NMR solution structures, we investigated the 15 possible 3-disulfide-bonded isomers of µ-PIIIA to relate their blocking activity at NaV1.4 to their disulfide connectivity. In addition, three µ-PIIIA mutants derived from the native disulfide isomer, in which one of the disulfide bonds was omitted (C4-16, C5-C21, C11-C22), were generated using a targeted protecting group strategy and tested using the aforementioned methods. The 3-disulfide-bonded isomers had a range of different conformational stabilities, with highly unstructured, flexible conformations with low or no channel-blocking activity, while more constrained molecules preserved 30% to 50% of the native isomer's activity. This emphasizes the importance and direct link between correct fold and function. The elimination of one disulfide bond resulted in a significant loss of blocking activity at NaV1.4, highlighting the importance of the 3-disulfide-bonded architecture for µ-PIIIA. µ-PIIIA bioactivity is governed by a subtle interplay between an optimally folded structure resulting from a specific disulfide connectivity and the electrostatic potential of the conformational ensemble.
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Affiliation(s)
- Ajay Abisheck Paul George
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Pascal Heimer
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Enrico Leipold
- Department of Anesthesiology and Intensive Care, University of Lübeck, Ratzeburger Allee 160, D-23562 Lübeck, Germany
| | - Thomas Schmitz
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Desiree Kaufmann
- Eduard Zintl Institute of Inorganic and Physical Chemistry, Darmstadt University of Technology, Alarich-Weiss-Str. 4, D-64287 Darmstadt, Germany
| | - Daniel Tietze
- Eduard Zintl Institute of Inorganic and Physical Chemistry, Darmstadt University of Technology, Alarich-Weiss-Str. 4, D-64287 Darmstadt, Germany
| | - Stefan H Heinemann
- Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena and Jena University Hospital, Hans-Knöll-Str. 2, D-07745 Jena, Germany
| | - Diana Imhof
- Pharmaceutical Biochemistry and Bioanalytics, Pharmaceutical Institute, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany.
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7
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In Silico Analysis of the Subtype Selective Blockage of KCNA Ion Channels through the µ-Conotoxins PIIIA, SIIIA, and GIIIA. Mar Drugs 2019; 17:md17030180. [PMID: 30893914 PMCID: PMC6471588 DOI: 10.3390/md17030180] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 03/12/2019] [Accepted: 03/15/2019] [Indexed: 12/12/2022] Open
Abstract
Understanding subtype specific ion channel pore blockage by natural peptide-based toxins is crucial for developing such compounds into promising drug candidates. Herein, docking and molecular dynamics simulations were employed in order to understand the dynamics and binding states of the µ-conotoxins, PIIIA, SIIIA, and GIIIA, at the voltage-gated potassium channels of the KV1 family, and they were correlated with their experimental activities recently reported by Leipold et al. Their different activities can only adequately be understood when dynamic information about the toxin-channel systems is available. For all of the channel-bound toxins investigated herein, a certain conformational flexibility was observed during the molecular dynamic simulations, which corresponds to their bioactivity. Our data suggest a similar binding mode of µ-PIIIA at KV1.6 and KV1.1, in which a plethora of hydrogen bonds are formed by the Arg and Lys residues within the α-helical core region of µ-PIIIA, with the central pore residues of the channel. Furthermore, the contribution of the K+ channel’s outer and inner pore loops with respect to the toxin binding. and how the subtype specificity is induced, were proposed.
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8
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Tikhonov DB, Zhorov BS. Predicting Structural Details of the Sodium Channel Pore Basing on Animal Toxin Studies. Front Pharmacol 2018; 9:880. [PMID: 30131702 PMCID: PMC6090064 DOI: 10.3389/fphar.2018.00880] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 07/20/2018] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic voltage-gated sodium channels play key roles in physiology and are targets for many toxins and medically important drugs. Physiology, pharmacology, and general architecture of the channels has long been the subject of intensive research in academia and industry. In particular, animal toxins such as tetrodotoxin, saxitoxin, and conotoxins have been used as molecular probes of the channel structure. More recently, X-ray structures of potassium and prokaryotic sodium channels allowed elaborating models of the toxin-channel complexes that integrated data from biophysical, electrophysiological, and mutational studies. Atomic level cryo-EM structures of eukaryotic sodium channels, which became available in 2017, show that the selectivity filter structure and other important features of the pore domain have been correctly predicted. This validates further employments of toxins and other small molecules as sensitive probes of fine structural details of ion channels.
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Affiliation(s)
- Denis B Tikhonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Boris S Zhorov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, Saint Petersburg, Russia.,Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
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9
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Patel D, Mahdavi S, Kuyucak S. Computational Study of Binding of μ-Conotoxin GIIIA to Bacterial Sodium Channels NaVAb and NaVRh. Biochemistry 2016; 55:1929-38. [PMID: 26959170 DOI: 10.1021/acs.biochem.5b01324] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Structures of several voltage-gated sodium (NaV) channels from bacteria have been determined recently, but the same feat might not be achieved for the mammalian counterparts in the near future. Thus, at present, computational studies of the mammalian NaV channels have to be performed using homology models based on the bacterial crystal structures. A successful homology model for the mammalian NaV1.4 channel was recently constructed using the extensive mutation data for binding of μ-conotoxin GIIIA to NaV1.4, which was further validated through studies of binding of other μ-conotoxins and ion permeation. Understanding the similarities and differences between the bacterial and mammalian NaV channels is an important issue, and the NaV1.4-GIIIA system provides a good opportunity for such a comparison. To this end, we study the binding of GIIIA to the bacterial channels NaVAb and NaVRh. The complex structures are obtained using docking and molecular dynamics simulations, and the dissociation of GIIIA is studied through umbrella sampling simulations. The results are compared to those obtained from the NaV1.4-GIIIA system, and the differences in the binding modes arising from the changes in the selectivity filters are highlighted.
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Affiliation(s)
- Dharmeshkumar Patel
- School of Physics, University of Sydney , Sydney, New South Wales 2006, Australia
| | - Somayeh Mahdavi
- School of Physics, University of Sydney , Sydney, New South Wales 2006, Australia
| | - Serdar Kuyucak
- School of Physics, University of Sydney , Sydney, New South Wales 2006, Australia
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10
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Green BR, Gajewiak J, Chhabra S, Skalicky JJ, Zhang MM, Rivier JE, Bulaj G, Olivera BM, Yoshikami D, Norton RS. Structural Basis for the Inhibition of Voltage-gated Sodium Channels by Conotoxin μO§-GVIIJ. J Biol Chem 2016; 291:7205-20. [PMID: 26817840 DOI: 10.1074/jbc.m115.697672] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 11/06/2022] Open
Abstract
Cone snail toxins are well known blockers of voltage-gated sodium channels, a property that is of broad interest in biology and therapeutically in treating neuropathic pain and neurological disorders. Although most conotoxin channel blockers function by direct binding to a channel and disrupting its normal ion movement, conotoxin μO§-GVIIJ channel blocking is unique, using both favorable binding interactions with the channel and a direct tether via an intermolecular disulfide bond. Disulfide exchange is possible because conotoxin μO§-GVIIJ contains anS-cysteinylated Cys-24 residue that is capable of exchanging with a free cysteine thiol on the channel surface. Here, we present the solution structure of an analog of μO§-GVIIJ (GVIIJ[C24S]) and the results of structure-activity studies with synthetic μO§-GVIIJ variants. GVIIJ[C24S] adopts an inhibitor cystine knot structure, with two antiparallel β-strands stabilized by three disulfide bridges. The loop region linking the β-strands (loop 4) presents residue 24 in a configuration where it could bind to the proposed free cysteine of the channel (Cys-910, rat NaV1.2 numbering; at site 8). The structure-activity study shows that three residues (Lys-12, Arg-14, and Tyr-16) located in loop 2 and spatially close to residue 24 were also important for functional activity. We propose that the interaction of μO§-GVIIJ with the channel depends on not only disulfide tethering via Cys-24 to a free cysteine at site 8 on the channel but also the participation of key residues of μO§-GVIIJ on a distinct surface of the peptide.
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Affiliation(s)
- Brad R Green
- From the Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia, the Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Joanna Gajewiak
- the Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Sandeep Chhabra
- From the Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | | | - Min-Min Zhang
- the Department of Biology, University of Utah, Salt Lake City, Utah 84112
| | - Jean E Rivier
- the Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, La Jolla, California 92037
| | - Grzegorz Bulaj
- the Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, Utah 84108, and
| | | | - Doju Yoshikami
- the Department of Biology, University of Utah, Salt Lake City, Utah 84112,
| | - Raymond S Norton
- From the Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia,
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11
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Zhorov B, Tikhonov D. Computational Structural Pharmacology and Toxicology of Voltage-Gated Sodium Channels. NA CHANNELS FROM PHYLA TO FUNCTION 2016; 78:117-44. [DOI: 10.1016/bs.ctm.2015.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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12
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Computational approaches for designing potent and selective analogs of peptide toxins as novel therapeutics. Future Med Chem 2015; 6:1645-58. [PMID: 25406005 DOI: 10.4155/fmc.14.98] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Peptide toxins provide valuable therapeutic leads for many diseases. As they bind to their targets with high affinity, potency is usually ensured. However, toxins also bind to off-target receptors, causing potential side effects. Thus, a major challenge in generating drugs from peptide toxins is ensuring their specificity for their intended targets. Computational methods can play an important role in solving such design problems through construction of accurate models of receptor-toxin complexes and calculation of binding free energies. Here we review the computational methods used for this purpose and their application to toxins targeting ion channels. We describe ShK and HsTX1 toxins, high-affinity blockers of the voltage-gated potassium channel Kv1.3, which could be developed as therapeutic agents for autoimmune diseases.
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13
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Korkosh VS, Zhorov BS, Tikhonov DB. Folding similarity of the outer pore region in prokaryotic and eukaryotic sodium channels revealed by docking of conotoxins GIIIA, PIIIA, and KIIIA in a NavAb-based model of Nav1.4. ACTA ACUST UNITED AC 2015; 144:231-44. [PMID: 25156117 PMCID: PMC4144674 DOI: 10.1085/jgp.201411226] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Analyses of toxin binding to a homology model of Nav1.4 indicate similar folding of the outer pore region in eukaryotic and prokaryotic sodium channels. Voltage-gated sodium channels are targets for many drugs and toxins. However, the rational design of medically relevant channel modulators is hampered by the lack of x-ray structures of eukaryotic channels. Here, we used a homology model based on the x-ray structure of the NavAb prokaryotic sodium channel together with published experimental data to analyze interactions of the μ-conotoxins GIIIA, PIIIA, and KIIIA with the Nav1.4 eukaryotic channel. Using Monte Carlo energy minimizations and published experimentally defined pairwise contacts as distance constraints, we developed a model in which specific contacts between GIIIA and Nav1.4 were readily reproduced without deformation of the channel or toxin backbones. Computed energies of specific interactions between individual residues of GIIIA and the channel correlated with experimental estimates. The predicted complexes of PIIIA and KIIIA with Nav1.4 are consistent with a large body of experimental data. In particular, a model of Nav1.4 interactions with KIIIA and tetrodotoxin (TTX) indicated that TTX can pass between Nav1.4 and channel-bound KIIIA to reach its binding site at the selectivity filter. Our models also allowed us to explain experimental data that currently lack structural interpretations. For instance, consistent with the incomplete block observed with KIIIA and some GIIIA and PIIIA mutants, our computations predict an uninterrupted pathway for sodium ions between the extracellular space and the selectivity filter if at least one of the four outer carboxylates is not bound to the toxin. We found a good correlation between computational and experimental data on complete and incomplete channel block by native and mutant toxins. Thus, our study suggests similar folding of the outer pore region in eukaryotic and prokaryotic sodium channels.
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Affiliation(s)
- Viacheslav S Korkosh
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia
| | - Boris S Zhorov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S4L8, Canada
| | - Denis B Tikhonov
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia
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14
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Systematic study of binding of μ-conotoxins to the sodium channel NaV1.4. Toxins (Basel) 2014; 6:3454-70. [PMID: 25529306 PMCID: PMC4280544 DOI: 10.3390/toxins6123454] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/01/2014] [Accepted: 12/10/2014] [Indexed: 01/25/2023] Open
Abstract
Voltage-gated sodium channels (NaV) are fundamental components of the nervous system. Their dysfunction is implicated in a number of neurological disorders, such as chronic pain, making them potential targets for the treatment of such disorders. The prominence of the NaV channels in the nervous system has been exploited by venomous animals for preying purposes, which have developed toxins that can block the NaV channels, thereby disabling their function. Because of their potency, such toxins could provide drug leads for the treatment of neurological disorders associated with NaV channels. However, most toxins lack selectivity for a given target NaV channel, and improving their selectivity profile among the NaV1 isoforms is essential for their development as drug leads. Computational methods will be very useful in the solution of such design problems, provided accurate models of the protein-ligand complex can be constructed. Using docking and molecular dynamics simulations, we have recently constructed a model for the NaV1.4-μ-conotoxin-GIIIA complex and validated it with the ample mutational data available for this complex. Here, we use the validated NaV1.4 model in a systematic study of binding other μ-conotoxins (PIIIA, KIIIA and BuIIIB) to NaV1.4. The binding mode obtained for each complex is shown to be consistent with the available mutation data and binding constants. We compare the binding modes of PIIIA, KIIIA and BuIIIB to that of GIIIA and point out the similarities and differences among them. The detailed information about NaV1.4-μ-conotoxin interactions provided here will be useful in the design of new NaV channel blocking peptides.
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15
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Green BR, Zhang MM, Chhabra S, Robinson SD, Wilson MJ, Redding A, Olivera BM, Yoshikami D, Bulaj G, Norton RS. Interactions of disulfide-deficient selenocysteine analogs of μ-conotoxin BuIIIB with the α-subunit of the voltage-gated sodium channel subtype 1.3. FEBS J 2014; 281:2885-98. [PMID: 24814369 DOI: 10.1111/febs.12835] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 04/18/2014] [Accepted: 05/05/2014] [Indexed: 12/17/2022]
Abstract
Inhibitors of the α-subunit of the voltage-gated sodium channel subtype 1.3 (NaV 1.3) are of interest as pharmacological tools for the study of neuropathic pain associated with spinal cord injury and have potential therapeutic applications. The recently described μ-conotoxin BuIIIB (μ-BuIIIB) from Conus bullatus was shown to block NaV 1.3 with submicromolar potency (Kd = 0.2 μm), making it one of the most potent peptidic inhibitors of this subtype described to date. However, oxidative folding of μ-BuIIIB results in numerous folding isoforms, making it difficult to obtain sufficient quantities of the active form of the peptide for detailed structure-activity studies. In the present study, we report the synthesis and characterization of μ-BuIIIB analogs incorporating a disulfide-deficient, diselenide-containing scaffold designed to simplify synthesis and facilitate structure-activity studies directed at identifying amino acid residues involved in NaV 1.3 blockade. Our results indicate that, similar to other μ-conotoxins, the C-terminal residues (Trp16, Arg18 and His20) are most crucial for NaV 1 blockade. At the N-terminus, replacement of Glu3 by Ala resulted in an analog with an increased potency for NaV 1.3 (Kd = 0.07 μm), implicating this position as a potential site for modification for increased potency and/or selectivity. Further examination of this position showed that increased negative charge, through γ-carboxyglutamate replacement, decreased potency (Kd = 0.33 μm), whereas replacement with positively-charged 2,4-diamonobutyric acid increased potency (Kd = 0.036 μm). These results provide a foundation for the design and synthesis of μ-BuIIIB-based analogs with increased potency against NaV 1.3.
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Affiliation(s)
- Brad R Green
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia; Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, USA
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Mechanism of μ-conotoxin PIIIA binding to the voltage-gated Na+ channel NaV1.4. PLoS One 2014; 9:e93267. [PMID: 24676211 PMCID: PMC3968119 DOI: 10.1371/journal.pone.0093267] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/03/2014] [Indexed: 12/19/2022] Open
Abstract
Several subtypes of voltage-gated Na+ (NaV) channels are important targets for pain management. μ-Conotoxins isolated from venoms of cone snails are potent and specific blockers of different NaV channel isoforms. The inhibitory effect of μ-conotoxins on NaV channels has been examined extensively, but the mechanism of toxin specificity has not been understood in detail. Here the known structure of μ-conotoxin PIIIA and a model of the skeletal muscle channel NaV1.4 are used to elucidate elements that contribute to the structural basis of μ-conotoxin binding and specificity. The model of NaV1.4 is constructed based on the crystal structure of the bacterial NaV channel, NaVAb. Six different binding modes, in which the side chain of each of the basic residues carried by the toxin protrudes into the selectivity filter of NaV1.4, are examined in atomic detail using molecular dynamics simulations with explicit solvent. The dissociation constants (Kd) computed for two selected binding modes in which Lys9 or Arg14 from the toxin protrudes into the filter of the channel are within 2 fold; both values in close proximity to those determined from dose response data for the block of NaV currents. To explore the mechanism of PIIIA specificity, a double mutant of NaV1.4 mimicking NaV channels resistant to μ-conotoxins and tetrodotoxin is constructed and the binding of PIIIA to this mutant channel examined. The double mutation causes the affinity of PIIIA to reduce by two orders of magnitude.
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17
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Goldschen-Ohm MP, Chanda B. Probing gating mechanisms of sodium channels using pore blockers. Handb Exp Pharmacol 2014; 221:183-201. [PMID: 24737237 DOI: 10.1007/978-3-642-41588-3_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Several classes of small molecules and peptides bind at the central pore of voltage-gated sodium channels either from the extracellular or intracellular side of the membrane and block ion conduction through the pore. Biophysical studies that shed light on the chemical nature, accessibility, and kinetics of binding of these naturally occurring and synthetic compounds reveal a wealth of information about how these channels gate. Here, we discuss insights into the structural underpinnings of gating of the channel pore and its coupling to the voltage sensors obtained from pore blockers including site 1 neurotoxins and local anesthetics.
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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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Walewska A, Han TS, Zhang MM, Yoshikami D, Bulaj G, Rolka K. Expanding chemical diversity of conotoxins: peptoid-peptide chimeras of the sodium channel blocker μ-KIIIA and its selenopeptide analogues. Eur J Med Chem 2013; 65:144-50. [PMID: 23707919 DOI: 10.1016/j.ejmech.2013.04.041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 04/19/2013] [Accepted: 04/20/2013] [Indexed: 12/19/2022]
Abstract
The μ-conotoxin KIIIA is a three disulfide-bridged blocker of voltage-gated sodium channels (VGSCs). The Lys(7) residue in KIIIA is an attractive target for manipulating the selectivity and efficacy of this peptide. Here, we report the design and chemical synthesis of μ-conopeptoid analogues (peptomers) in which we replaced Lys(7) with peptoid monomers of increasing side-chain size: N-methylglycine, N-butylglycine and N-octylglycine. In the first series of analogues, the peptide core contained all three disulfide bridges; whereas in the second series, a disulfide-depleted selenoconopeptide core was used to simplify oxidative folding. The analogues were tested for functional activity in blocking the Nav1.2 subtype of mammalian VGSCs exogenously expressed in Xenopus oocytes. All six analogues were active, with the N-methylglycine analogue, [Sar(7)]KIIIA, the most potent in blocking the channels while favouring lower efficacy. Our findings demonstrate that the use of N-substituted Gly residues in conotoxins show promise as a tool to optimize their pharmacological properties as potential analgesic drug leads.
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Affiliation(s)
- Aleksandra Walewska
- Faculty of Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk, Poland.
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Knapp O, McArthur JR, Adams DJ. Conotoxins targeting neuronal voltage-gated sodium channel subtypes: potential analgesics? Toxins (Basel) 2012. [PMID: 23202314 PMCID: PMC3509706 DOI: 10.3390/toxins4111236] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSC) are the primary mediators of electrical signal amplification and propagation in excitable cells. VGSC subtypes are diverse, with different biophysical and pharmacological properties, and varied tissue distribution. Altered VGSC expression and/or increased VGSC activity in sensory neurons is characteristic of inflammatory and neuropathic pain states. Therefore, VGSC modulators could be used in prospective analgesic compounds. VGSCs have specific binding sites for four conotoxin families: μ-, μO-, δ- and ί-conotoxins. Various studies have identified that the binding site of these peptide toxins is restricted to well-defined areas or domains. To date, only the μ- and μO-family exhibit analgesic properties in animal pain models. This review will focus on conotoxins from the μ- and μO-families that act on neuronal VGSCs. Examples of how these conotoxins target various pharmacologically important neuronal ion channels, as well as potential problems with the development of drugs from conotoxins, will be discussed.
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Affiliation(s)
- Oliver Knapp
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia.
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Stevens M, Peigneur S, Dyubankova N, Lescrinier E, Herdewijn P, Tytgat J. Design of bioactive peptides from naturally occurring μ-conotoxin structures. J Biol Chem 2012; 287:31382-92. [PMID: 22773842 DOI: 10.1074/jbc.m112.375733] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To date, cone snail toxins ("conotoxins") are of great interest in the pursuit of novel subtype-selective modulators of voltage-gated sodium channels (Na(v)s). Na(v)s participate in a wide range of electrophysiological processes. Consequently, their malfunctioning has been associated with numerous diseases. The development of subtype-selective modulators of Na(v)s remains highly important in the treatment of such disorders. In current research, a series of novel, synthetic, and bioactive compounds were designed based on two naturally occurring μ-conotoxins that target Na(v)s. The initial designed peptide contains solely 13 amino acids and was therefore named "Mini peptide." It was derived from the μ-conotoxins KIIIA and BuIIIC. Based on this Mini peptide, 10 analogues were subsequently developed, comprising 12-16 amino acids with two disulfide bridges. Following appropriate folding and mass verification, blocking effects on Na(v)s were investigated. The most promising compound established an IC(50) of 34.1 ± 0.01 nM (R2-Midi on Na(v)1.2). An NMR structure of one of our most promising compounds was determined. Surprisingly, this structure does not reveal an α-helix. We prove that it is possible to design small peptides based on known pharmacophores of μ-conotoxins without losing their potency and selectivity. These data can provide crucial material for further development of conotoxin-based therapeutics.
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Affiliation(s)
- Marijke Stevens
- Laboratory of Toxicology, Katholieke Universiteit (KU) Leuven, Campus Gasthuisberg O and N2, Herestraat 49 Box 922, 3000 Leuven, Belgium
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Chen R, Chung SH. Binding modes of μ-conotoxin to the bacterial sodium channel (NaVAb). Biophys J 2012; 102:483-8. [PMID: 22325270 DOI: 10.1016/j.bpj.2011.12.041] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 12/14/2011] [Accepted: 12/27/2011] [Indexed: 12/19/2022] Open
Abstract
Polypeptide toxins isolated from the venom of cone snails, known as μ-conotoxins, block voltage-gated sodium channels by physically occluding the ion-conducting pathway. Using molecular dynamics, we show that one subtype of μ-conotoxins, PIIIA, effectively blocks the bacterial voltage-gated sodium channel Na(V)Ab, whose crystal structure has recently been elucidated. The spherically shaped toxin, carrying a net charge of +6 e with six basic residues protruding from its surface, is attracted by the negatively charged residues on the vestibular wall and the selectivity filter of the channel. The side chain of each of these six arginine and lysine residues can wedge into the selectivity filter, whereas the side chains of other basic residues form electrostatic complexes with two acidic residues on the channel. We construct the profile of potential of mean force for the unbinding of PIIIA from the channel, and predict that PIIIA blocks the bacterial sodium channel with subnanomolar affinity.
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Affiliation(s)
- Rong Chen
- Computational Biophysics Group, Research School of Biology, Australian National University, Canberra, Australia.
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McArthur JR, Singh G, McMaster D, Winkfein R, Tieleman DP, French RJ. Interactions of Key Charged Residues Contributing to Selective Block of Neuronal Sodium Channels by μ-Conotoxin KIIIA. Mol Pharmacol 2011; 80:573-84. [DOI: 10.1124/mol.111.073460] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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McArthur JR, Singh G, O'Mara ML, McMaster D, Ostroumov V, Tieleman DP, French RJ. Orientation of μ-conotoxin PIIIA in a sodium channel vestibule, based on voltage dependence of its binding. Mol Pharmacol 2011; 80:219-27. [PMID: 21521769 DOI: 10.1124/mol.111.071779] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mutant cycle analysis has been used in previous studies to constrain possible docking orientations for various toxins. As an independent test of the bound orientation of μ-conotoxin PIIIA, a selectively targeted sodium channel pore blocker, we determined the contributions to binding voltage dependence of specific residues on the surface of the toxin. A change in the "apparent valence" (zδ) of the block, which is associated with a change of a specific toxin charge, reflects a change in the charge movement within the transmembrane electric field as the toxin binds. Toxin derivatives with charge-conserving mutations (R12K, R14K, and K17R) showed zδ values similar to those of wild type (0.61 ± 0.01, mean ± S.E.M.). Charge-changing mutations produced a range of responses. Neutralizing substitutions for Arg14 and Lys17 showed the largest reductions in zδ values, to 0.18 ± 0.06 and 0.20 ± 0.06, respectively, whereas unit charge-changing substitutions for Arg12, Ser13, and Arg20 gave intermediate values (0.24 ± 0.07, 0.33 ± 0.04, and 0.32 ± 0.05), which suggests that each of these residues contributes to the dependence of binding on the transmembrane voltage. Two mutations, R2A and G6K, yielded no significant change in zδ. These observations suggest that the toxin binds with Arg2 and Gly6 facing the extracellular solution, and Arg14 and Lys17 positioned most deeply in the pore. In this study, we used molecular dynamics to simulate toxin docking and performed Poisson-Boltzmann calculations to estimate the changes in local electrostatic potential when individual charges were substituted on the toxin's surface. Consideration of two limiting possibilities suggests that most of the charge movement associated with toxin binding reflects sodium redistribution within the narrow part of the pore.
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Affiliation(s)
- J R McArthur
- Physiology and Biophysics, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1.
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