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Zhang F, Wu Y, Zou X, Tang Q, Zhao F, Cao Z. BmK AEP, an Anti-Epileptic Peptide Distinctly Affects the Gating of Brain Subtypes of Voltage-Gated Sodium Channels. Int J Mol Sci 2019; 20:ijms20030729. [PMID: 30744067 PMCID: PMC6387193 DOI: 10.3390/ijms20030729] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 01/26/2019] [Accepted: 01/31/2019] [Indexed: 12/12/2022] Open
Abstract
BmK AEP, a scorpion peptide purified form the venom of Buthus martensii Karsch, has been reported to display anti-epileptic activity. Voltage-gated sodium channels (VGSCs) are responsible for the rising phase of action potentials (APs) in neurons and, therefore, controlling neuronal excitability. To elucidate the potential molecular mechanisms responsible for its anti-epileptic activity, we examined the influence of BmK AEP on AP firing in cortical neurons and how BmK AEP influences brain subtypes of VGSCs (Nav1.1–1.3 and Nav1.6). BmK AEP concentration-dependently suppresses neuronal excitability (AP firing) in primary cultured cortical neurons. Consistent with its inhibitory effect on AP generation, BmK AEP inhibits Na+ peak current in cortical neurons with an IC50 value of 2.12 µM by shifting the half-maximal voltage of activation of VGSC to hyperpolarized direction by ~7.83 mV without affecting the steady-state inactivation. Similar to its action on Na+ currents in cortical neurons, BmK AEP concentration-dependently suppresses the Na+ currents of Nav1.1, Nav1.3, and Nav1.6, which were heterologously expressed in HEK-293 cells, with IC50 values of 3.20, 1.46, and 0.39 µM with maximum inhibition of 82%, 56%, and 93%, respectively. BmK AEP shifts the voltage-dependent activation in the hyperpolarized direction by ~15.60 mV, ~9.97 mV, and ~6.73 mV in Nav1.1, Nav1.3, and Nav1.6, respectively, with minimal effect on steady-state inactivation. In contrast, BmK AEP minimally suppresses Nav1.2 currents (~15%) but delays the inactivation of the channel with an IC50 value of 1.69 µM. Considered together, these data demonstrate that BmK AEP is a relatively selective Nav1.6 gating modifier which distinctly affects the gating of brain subtypes of VGSCs.
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Affiliation(s)
- Fan Zhang
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
| | - Ying Wu
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
| | - Xiaohan Zou
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
| | - Qinglian Tang
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
| | - Fang Zhao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
| | - Zhengyu Cao
- State Key Laboratory of Natural Medicines and Jiangsu Provincial Key Laboratory for TCM Evaluation and Translational Development, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing 211198, China.
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Martin-Eauclaire MF, Bougis PE, de Lima ME. Ts1 from the Brazilian scorpion Tityus serrulatus: A half-century of studies on a multifunctional beta like-toxin. Toxicon 2018; 152:106-120. [PMID: 30059695 DOI: 10.1016/j.toxicon.2018.07.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 12/19/2022]
Abstract
The Tityus serrulatus scorpion species represents a serious human health threat to in Brazil because it is among the animals that produces the most dangerous venoms for mammals in South America. Its venom has provided several highly selective ligands that specifically interact with sodium and potassium channels. During the past decades, several international groups published an increasing amount of data on the isolation and the chemical, pharmacological and immunological characterisation of its main β-toxin, Ts1. In this review, we compiled the best available past and recent knowledge on Ts1. Aside from its intricate purification, the state-of-the-art understanding concerning its pharmacological activities is presented. Its solved three-dimensional structure is shown, as well as the possible surface areas of contact between Ts1 and its diverse voltage-gated Na+ channel targets. Organisations of the gene and the precursor encoding Ts1 are also tackled based on available cDNA clones or on information obtained from polymerase chain reactions of stretches of scorpion DNA. At last, the immunological studies complete with Ts1 to set up an efficient immunotherapy against the Tityus serrulatus venom are summarized.
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Affiliation(s)
| | - Pierre E Bougis
- Aix Marseille Univ, CNRS, LNC, UMR 7291, 13003, Marseille, France.
| | - Maria Elena de Lima
- Laboratório de Venenos e Toxinas Animais, Depto de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil; Instituto de Ensino e Pesquisa da Santa Casa de Belo Horizonte - IEP/SCBH, 30150-240, Belo Horizonte, MG, Brazil.
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Housley DM, Housley GD, Liddell MJ, Jennings EA. Scorpion toxin peptide action at the ion channel subunit level. Neuropharmacology 2016; 127:46-78. [PMID: 27729239 DOI: 10.1016/j.neuropharm.2016.10.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/06/2016] [Accepted: 10/06/2016] [Indexed: 12/19/2022]
Abstract
This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- David M Housley
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Michael J Liddell
- Centre for Tropical Environmental and Sustainability Science and College of Science & Engineering, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia
| | - Ernest A Jennings
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Queensland 4878, Australia; Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, QLD, Australia
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Tianpei X, Li D, Qiu P, Luo J, Zhu Y, Li S. Scorpion peptide LqhIT2 activates phenylpropanoid pathways via jasmonate to increase rice resistance to rice leafrollers. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 230:1-11. [PMID: 25480003 DOI: 10.1016/j.plantsci.2014.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 10/07/2014] [Accepted: 10/09/2014] [Indexed: 05/09/2023]
Abstract
LqhIT2 is an insect-specific toxin peptide identified in Leiurus quinquestriatus hebraeus that can be toxic to lepidoptera pests. However, whether LqhIT2 induces insect resistance in rice, and how the LqhIT2 influences the biochemical metabolism of rice plants remains unknown. Here, purified LqhIT2-GST fusion protein had toxicity to rice leafrollers. Meanwhile, in vitro and field trials showed that LqhIT2 transgenic rice plants were less damaged by rice leafrollers compared to the wild type plants. Introducing LqhIT2 primed the elevated expression of lipoxygenase, a key component of the jasmonic acid biosynthetic pathway, together with enhanced linolenic acid, cis-(+)-12-oxophytodienoic acid, jasmonic acid, and jasmonic acid-isoleucine levels. In addition, phenylalanine ammonia-lyase, a key gene of the phenylpropanoid pathway, was up-regulated. Correspondingly, the contents of downstream products of the phenylpropanoid pathway such as flavonoids and lignins, were also increased in LqhIT2 transgenic plants. These changes were paralleled by decreased starch, glucose, and glucose-6-phosphate accumulation, the key metabolites of glycolysis pathway that supplies the raw material and intermediate carbon products for phenylpropanoids biosyntheses. These findings suggest that, in addition to its own toxicity against pests, LqhIT2 activate the phenylpropanoid pathway via jasmonate-mediated priming, which subsequently increases flavonoid and lignin content and improves insect resistance in rice.
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Affiliation(s)
- Xiuzi Tianpei
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Dong Li
- National Key Laboratory of Genetic Crop Improvement, Huazhong Agriculture University, Wuhan 430070, China
| | - Ping Qiu
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Jie Luo
- National Key Laboratory of Genetic Crop Improvement, Huazhong Agriculture University, Wuhan 430070, China.
| | - Yingguo Zhu
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Shaoqing Li
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China.
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Silver KS, Du Y, Nomura Y, Oliveira EE, Salgado VL, Zhorov BS, Dong K. Voltage-Gated Sodium Channels as Insecticide Targets. ADVANCES IN INSECT PHYSIOLOGY 2014; 46:389-433. [PMID: 29928068 PMCID: PMC6005695 DOI: 10.1016/b978-0-12-417010-0.00005-7] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Voltage-gated sodium channels are critical for the generation and propagation of action potentials. They are the primary target of several classes of insecticides, including DDT, pyrethroids and sodium channel blocker insecticides (SCBIs). DDT and pyrethroids preferably bind to open sodium channels and stabilize the open state, causing prolonged currents. In contrast, SCBIs block sodium channels by binding to the inactivated state. Many sodium channel mutations are associated with knockdown resistance (kdr) to DDT and pyrethroids in diverse arthropod pests. Functional characterization of kdr mutations together with computational modelling predicts dual pyrethroid receptor sites on sodium channels. In contrast, the molecular determinants of the SCBI receptor site remain largely unknown. In this review, we summarize current knowledge about the molecular mechanisms of action of pyrethroids and SCBIs, and highlight the differences in the molecular interaction of these insecticides with insect versus mammalian sodium channels.
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Affiliation(s)
- Kristopher S Silver
- Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas, USA
| | - Yuzhe Du
- Department of Entomology, Neuroscience and Genetics Programs, Michigan State University, East Lansing, Michigan, USA
| | - Yoshiko Nomura
- Department of Entomology, Neuroscience and Genetics Programs, Michigan State University, East Lansing, Michigan, USA
| | - Eugenio E Oliveira
- Departamento de Entomologia, Universidade Federal de Vic¸osa, Vic¸osa, Minas Gerais, Brasil
| | - Vincent L Salgado
- BASF Agricultural Products, BASF Corporation, Research Triangle Park, North Carolina, USA
| | - Boris S Zhorov
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Ke Dong
- Department of Entomology, Neuroscience and Genetics Programs, Michigan State University, East Lansing, Michigan, USA
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Peigneur S, Sevcik C, Tytgat J, Castillo C, D'Suze G. Subtype specificity interaction of bactridines with mammalian, insect and bacterial sodium channels under voltage clamp conditions. FEBS J 2012; 279:4025-38. [PMID: 22925163 DOI: 10.1111/j.1742-4658.2012.08808.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 08/15/2012] [Accepted: 08/20/2012] [Indexed: 11/28/2022]
Abstract
The present work demonstrates that bactridines (Bacts) possess different selectivities for neuronal and muscular voltage-dependent sodium (Na(V) ) channels, with subtle differences on channel isoforms. Bacts 2, 3, 4, 5 and 6 (100 nm) reduced the peak current of several skeletal and neuronal channel isoforms selectively. Bacts 2 and 3 were more potent on Na(V) 1.4, Bacts 4 and 6 on Na(V) 1.3 and Bact 5 on Na(V) 1.7. Bactridines (except Bacts 1 and 5) caused a hyperpolarizing shift in the V(1/2) of activation and inactivation of Na(V) 1.3, Na(V) 1.4 and Na(V) 1.6. Voltage shifts of Boltzmann curves fitted to activation and inactivation occurred with a decrease in κ. Since the slope is proportional to κ = RT/zF, changes in κ probably express changes in z, the valence, in a voltage-dependent manner. Changes in z may express toxin-induced changes in the channel ionic environment, perhaps due to surface charges of the molecules. Bact 2 induced a Na(V) 1.2 voltage shift of the activation curves but no shift of the mutant Na(V) 1.2 IFM/QQQ; peak I(N) (a) was reduced in both channel forms, suggesting that channel blockage resulted from toxin binding to a site partially distinct from the α subunit binding site 4. Bactridines emerge as potential research tools to understand sodium channel isoform structure-function relationships and also as pharmacologically interesting peptides.
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Affiliation(s)
- Steve Peigneur
- Laboratory of Toxicology, University of Leuven (K.U. Leuven), Belgium
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Leipold E, Borges A, Heinemann SH. Scorpion β-toxin interference with NaV channel voltage sensor gives rise to excitatory and depressant modes. ACTA ACUST UNITED AC 2012; 139:305-19. [PMID: 22450487 PMCID: PMC3315148 DOI: 10.1085/jgp.201110720] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Scorpion β toxins, peptides of ∼70 residues, specifically target voltage-gated sodium (NaV) channels to cause use-dependent subthreshold channel openings via a voltage–sensor trapping mechanism. This excitatory action is often overlaid by a not yet understood depressant mode in which NaV channel activity is inhibited. Here, we analyzed these two modes of gating modification by β-toxin Tz1 from Tityus zulianus on heterologously expressed NaV1.4 and NaV1.5 channels using the whole cell patch-clamp method. Tz1 facilitated the opening of NaV1.4 in a use-dependent manner and inhibited channel opening with a reversed use dependence. In contrast, the opening of NaV1.5 was exclusively inhibited without noticeable use dependence. Using chimeras of NaV1.4 and NaV1.5 channels, we demonstrated that gating modification by Tz1 depends on the specific structure of the voltage sensor in domain 2. Although residue G658 in NaV1.4 promotes the use-dependent transitions between Tz1 modification phenotypes, the equivalent residue in NaV1.5, N803, abolishes them. Gating charge neutralizations in the NaV1.4 domain 2 voltage sensor identified arginine residues at positions 663 and 669 as crucial for the outward and inward movement of this sensor, respectively. Our data support a model in which Tz1 can stabilize two conformations of the domain 2 voltage sensor: a preactivated outward position leading to NaV channels that open at subthreshold potentials, and a deactivated inward position preventing channels from opening. The results are best explained by a two-state voltage–sensor trapping model in that bound scorpion β toxin slows the activation as well as the deactivation kinetics of the voltage sensor in domain 2.
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Affiliation(s)
- Enrico Leipold
- Department of Biophysics, Center for Molecular Biomedicine, Friedrich Schiller University of Jena and Jena University Hospital, Jena D-07745, Germany
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Cologna CT, Peigneur S, Rustiguel JK, Nonato MC, Tytgat J, Arantes EC. Investigation of the relationship between the structure and function of Ts2, a neurotoxin from Tityus serrulatus venom. FEBS J 2012; 279:1495-504. [PMID: 22356164 DOI: 10.1111/j.1742-4658.2012.08545.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Scorpion toxins targeting voltage-gated sodium (Na(V)) channels are peptides that comprise 60-76 amino acid residues cross-linked by four disulfide bridges. These toxins can be divided in two groups (α and β toxins), according to their binding properties and mode of action. The scorpion α-toxin Ts2, previously described as a β-toxin, was purified from the venom of Tityus serrulatus, the most dangerous Brazilian scorpion. In this study, seven mammalian Na(V) channel isoforms (rNa(V)1.2, rNa(V)1.3, rNa(V)1.4, hNa(V)1.5, mNa(V)1.6, rNa(V)1.7 and rNa(V)1.8) and one insect Na(V) channel isoform (DmNa(V)1) were used to investigate the subtype specificity and selectivity of Ts2. The electrophysiology assays showed that Ts2 inhibits rapid inactivation of Na(V)1.2, Na(V)1.3, Na(V)1.5, Na(V)1.6 and Na(V)1.7, but does not affect Na(V)1.4, Na(V)1.8 or DmNa(V)1. Interestingly, Ts2 significantly shifts the voltage dependence of activation of Na(V)1.3 channels. The 3D structure of this toxin was modeled based on the high sequence identity (72%) shared with Ts1, another T. serrulatus toxin. The overall fold of the Ts2 model consists of three β-strands and one α-helix, and is arranged in a triangular shape forming a cysteine-stabilized α-helix/β-sheet (CSαβ) motif.
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Affiliation(s)
- Camila T Cologna
- Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
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Stevens M, Peigneur S, Tytgat J. Neurotoxins and their binding areas on voltage-gated sodium channels. Front Pharmacol 2011; 2:71. [PMID: 22084632 PMCID: PMC3210964 DOI: 10.3389/fphar.2011.00071] [Citation(s) in RCA: 179] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/24/2011] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Therefore, genetic defects in sodium channel genes can cause a wide variety of diseases, generally called “channelopathies.” The first insights into the mechanism of action potentials and the involvement of sodium channels originated from Hodgkin and Huxley for which they were awarded the Nobel Prize in 1963. These concepts still form the basis for understanding the function of VGSCs. When VGSCs sense a sufficient change in membrane potential, they are activated and consequently generate a massive influx of sodium ions. Immediately after, channels will start to inactivate and currents decrease. In the inactivated state, channels stay refractory for new stimuli and they must return to the closed state before being susceptible to a new depolarization. On the other hand, studies with neurotoxins like tetrodotoxin (TTX) and saxitoxin (STX) also contributed largely to our today’s understanding of the structure and function of ion channels and of VGSCs specifically. Moreover, neurotoxins acting on ion channels turned out to be valuable lead compounds in the development of new drugs for the enormous range of diseases in which ion channels are involved. A recent example of a synthetic neurotoxin that made it to the market is ziconotide (Prialt®, Elan). The original peptide, ω-MVIIA, is derived from the cone snail Conus magus and now FDA/EMA-approved for the management of severe chronic pain by blocking the N-type voltage-gated calcium channels in pain fibers. This review focuses on the current status of research on neurotoxins acting on VGSC, their contribution to further unravel the structure and function of VGSC and their potential as novel lead compounds in drug development.
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Affiliation(s)
- Marijke Stevens
- Lab of Toxicology, Katholieke Universiteit Leuven Leuven, Belgium
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Suthisut D, Fields PG, Chandrapatya A. Contact toxicity, feeding reduction, and repellency of essential oils from three plants from the ginger family (Zingiberaceae) and their major components against Sitophilus zeamais and Tribolium castaneum. JOURNAL OF ECONOMIC ENTOMOLOGY 2011; 104:1445-1454. [PMID: 21882715 DOI: 10.1603/ec11050] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The essential oils from rhizomes of Alpinia conchigera Griff, Zingiber zerumbet Smitt, Curcuma zedoaria (Berg.) Roscoe; their major compounds (camphene, camphor, 1,8-cineole, alpha-humulene, isoborneol, alpha-pinene, beta-pinene and terpinen-4-ol); and synthetic essential oils comprised of mixtures of major pure compounds in the same ratios as the extracted essential oils were tested for contact, feeding reduction, and repellency against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) adults. Via topical applications, the three extracted oils had similar toxicity against S. zeamais (LD50 fiducial limits: 18-24 microg oil/mg insect). T. castaneum had similar sensitivity to all three oils (35-58 microg/mg), and it was less sensitive than S. zeamais. The LD50 values of synthetic A. conchigera and synthetic Z. zerumbet oils were similar to those of their corresponding extracted essential oils. The synthetic C. zedoaria oils showed lower contact toxicity than the extracted C. zedoaria oils to both insects. Sitophilus zeamais and T. castaneum were sensitive to terpinen-4-ol and isoborneol in contact toxicity tests. In antifeedant tests, the three extracted oils were able to decrease the consumption of flour disks, especially Z. zerumbet oils, whereas both insect species could feed on the flour disks treated with three synthetic essential oils. Only terpinen-4-ol deterred feeding in both insects. In repellency tests, A. conchigera oils at highest concentration repelled S. zeamais and T. castaneum. None of the synthetic essential oils repelled S. zeamais (315 microl/cm2) and T. castaneum (31 microl/cm2) Only terpinen-4-ol showed repellent activity against both insects.
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Affiliation(s)
- Duangsamorn Suthisut
- Cereal Research Centre, Agriculture & Agri-Food Canada, 195 Dafoe Rd., Winnipeg, MB, R3T 2M9, Canada
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He H, Liu Z, Dong B, Zhang J, Shu X, Zhou J, Ji Y. Localization of receptor site on insect sodium channel for depressant β-toxin BmK IT2. PLoS One 2011; 6:e14510. [PMID: 21264295 PMCID: PMC3021515 DOI: 10.1371/journal.pone.0014510] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 12/05/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND BmK IT2 is regarded as a receptor site-4 modulator of sodium channels with depressant insect toxicity. It also displays anti-nociceptive and anti-convulsant activities in rat models. In this study, the potency and efficacy of BmK IT2 were for the first time assessed and compared among four sodium channel isoforms expressed in Xenopus oocytes. Combined with molecular approach, the receptor site of BmK IT2 was further localized. PRINCIPAL FINDINGS 2 µM BmK IT2 strongly shifted the activation of DmNa(v)1, the sodium channel from Drosophila, to more hyperpolarized potentials; whereas it hardly affected the gating properties of rNa(v)1.2, rNa(v)1.3 and mNa(v)1.6, three mammalian central neuronal sodium channel subtypes. (1) Mutations of Glu(896), Leu(899), Gly(904) in extracellular loop Domain II S3-S4 of DmNa(v)1 abolished the functional action of BmK IT2. (2) BmK IT2-preference for DmNa(v)1 could be conferred by Domain III. Analysis of subsequent DmNa(v)1 mutants highlighted the residues in Domain III pore loop, esp. Ile(1529) was critical for recognition and binding of BmK IT2. CONCLUSIONS/SIGNIFICANCE In this study, BmK IT2 displayed total insect-selectivity. Two binding regions, comprising domains II and III of DmNa(v)1, play separated but indispensable roles in the interaction with BmK IT2. The insensitivity of Na(v)1.2, Na(v)1.3 and Na(v)1.6 to BmK IT2 suggests other isoforms or mechanism might be involved in the suppressive activity of BmK IT2 in rat pathological models.
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Affiliation(s)
- Huiqiong He
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
- Graduate School of Chinese Academy of Sciences, Shanghai Institute of Physiology, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Zhirui Liu
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Bangqian Dong
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Jianwei Zhang
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Xueqin Shu
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Jingjing Zhou
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
| | - Yonghua Ji
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, People's Republic of China
- * E-mail:
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Martin-Eauclaire MF, Abbas N, Sauze N, Mercier L, Berge-Lefranc JL, Condo J, Bougis PE, Guieu R. Involvement of endogenous opioid system in scorpion toxin-induced antinociception in mice. Neurosci Lett 2010; 482:45-50. [DOI: 10.1016/j.neulet.2010.06.090] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/11/2010] [Accepted: 06/29/2010] [Indexed: 10/19/2022]
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Zhu S, Gao B, Deng M, Yuan Y, Luo L, Peigneur S, Xiao Y, Liang S, Tytgat J. Drosotoxin, a selective inhibitor of tetrodotoxin-resistant sodium channels. Biochem Pharmacol 2010; 80:1296-302. [PMID: 20637738 DOI: 10.1016/j.bcp.2010.07.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Revised: 07/06/2010] [Accepted: 07/06/2010] [Indexed: 12/24/2022]
Abstract
The design of animal toxins with high target selectivity has long been a goal in protein engineering. Based on evolutionary relationship between the Drosophila antifungal defensin (drosomycin) and scorpion depressant Na(+) channel toxins, we exploited a strategy to create a novel chimeric molecule (named drosotoxin) with high selectivity for channel subtypes, which was achieved by using drosomycin to substitute the structural core of BmKITc, a depressant toxin acting on both insect and mammalian Na(+) channels. Recombinant drosotoxin selectively inhibited tetrodotoxin-resistant (TTX-R) Na(+) channels in rat dorsal root ganglion (DRG) neurons with a 50% inhibitory concentration (IC(50)) of 2.6+/-0.5muM. This chimeric peptide showed no activity on K(+), Ca(2+) and TTX-sensitive (TTX-S) Na(+) channels in rat DRG neurons and Drosophila para/tipE channels at micromolar concentrations. Drosotoxin represents the first chimeric toxin and example of a non-toxic core scaffold with high selectivity on mammalian TTX-R Na(+) channels.
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Affiliation(s)
- Shunyi Zhu
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing 100101, China.
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14
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Yuan Y, Luo L, Peigneur S, Tytgat J, Zhu S. Two recombinant depressant scorpion neurotoxins differentially affecting mammalian sodium channels. Toxicon 2010; 55:1425-33. [DOI: 10.1016/j.toxicon.2010.02.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 02/16/2010] [Accepted: 02/18/2010] [Indexed: 11/17/2022]
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15
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Isolation and characterization of two novel scorpion toxins: The alpha-toxin-like CeII8, specific for Na(v)1.7 channels and the classical anti-mammalian CeII9, specific for Na(v)1.4 channels. Toxicon 2010; 56:613-23. [PMID: 20600228 DOI: 10.1016/j.toxicon.2010.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 06/08/2010] [Accepted: 06/11/2010] [Indexed: 11/23/2022]
Abstract
Scorpion beta-toxins represent a particular pharmacological group of voltage-gated sodium channel (VGSC) neurotoxins. They typically shift the voltage dependence of activation to more hyperpolarizing potentials and reduce the peak current amplitude by binding to receptor-site 4. Here, we report the purification and functional characterization of the first voltage-gated sodium channel toxins, CeII8 and CeII9, isolated from the scorpion Centruroides elegans (Thorell, 1876), which is responsible for deadly cases of intoxication in Mexico. The soluble venom was fractionated by gel filtration and ion-exchange chromatography, followed by reversed-phase HPLC. The toxins CeII8 and CeII9 were further purified and both their amino acid sequence and molecular weight were determined. Both toxins were electrophysiologically characterized on four mammalian VGSCs (rNa(v)1.2, rNa(v)1.4, hNa(v)1.5 and rNa(v)1.7) expressed heterologously in Xenopus laevis oocytes, using the two-electrode voltage-clamp technique. Although CeII8 has the highest sequence similarity with scorpion alpha-toxins, inhibiting the inactivation of VGSCs, 300 nM toxin had a clear beta-toxin effect and was selective towards Na(v)1.7, involved in short-term and inflammatory pain. To the best of our knowledge, CeII8 is the first beta-toxin active on Na(v)1.7. CeII9, a typical anti-mammalian beta-toxin, selectively modulated Na(v)1.4 at a concentration of 700 nM and was, in contrast to CeII8, found to be lethal to mice. Interestingly, both toxins, despite their differences in amino acid sequence, only altered the biophysical properties of a fraction of the expressed sodium channels. Since these effects have also been reported for the beta-toxin CssIV, the bioactive surfaces of the toxins have been compared to each other.
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16
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Tian C, Yuan Y, Zhu S. Positively selected sites of scorpion depressant toxins: possible roles in toxin functional divergence. Toxicon 2007; 51:555-62. [PMID: 18177911 DOI: 10.1016/j.toxicon.2007.11.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/07/2007] [Accepted: 11/14/2007] [Indexed: 02/04/2023]
Abstract
Scorpion depressant toxins represent a distinct pharmacological group of sodium channel neurotoxins, identified by their preferential ability in induction of depressant and flaccid paralysis of insects. However, recent observations that some members in this group exhibit anti-mammal activity raise an interesting evolutionary question of whether it is a consequence of adaptive evolution to the early radiation of mammals on earth. By employing the maximum likelihood method, we provided convincing statistical evidence in favor of positive selection driving the evolution of the depressant toxins, and found that two of three positively selected sites are located on the functional surface of the toxins. A complex model of the scorpion depressant toxin LqhIT2 binding to insect sodium channel alpha-subunit (DmNav1) was constructed by structural bioinformatics approaches which highlights a possible direct interaction between these two sites and insect sodium channels. Our work presented here thus suggests that accelerated substitutions in these site residues could offer an evolutionary advantage for these toxins to adapt different channels from diverse origins.
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Affiliation(s)
- Caihuan Tian
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China
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17
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Cohen L, Troub Y, Turkov M, Gilles N, Ilan N, Benveniste M, Gordon D, Gurevitz M. Mammalian Skeletal Muscle Voltage-Gated Sodium Channels Are Affected by Scorpion Depressant “Insect-Selective” Toxins when Preconditioned. Mol Pharmacol 2007; 72:1220-7. [PMID: 17720763 DOI: 10.1124/mol.107.039057] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Among scorpion beta- and alpha-toxins that modify the activation and inactivation of voltage-gated sodium channels (Na(v)s), depressant beta-toxins have traditionally been classified as anti-insect selective on the basis of toxicity assays and lack of binding and effect on mammalian Na(v)s. Here we show that the depressant beta-toxins LqhIT2 and Lqh-dprIT3 from Leiurus quinquestriatus hebraeus (Lqh) bind with nanomolar affinity to receptor site 4 on rat skeletal muscle Na(v)s, but their effect on the gating properties can be viewed only after channel preconditioning, such as that rendered by a long depolarizing prepulse. This observation explains the lack of toxicity when depressant toxins are injected in mice. However, when the muscle channel rNa(v)1.4, expressed in Xenopus laevis oocytes, was modulated by the site 3 alpha-toxin LqhalphaIT, LqhIT2 was capable of inducing a negative shift in the voltage-dependence of activation after a short prepulse, as was shown for other beta-toxins. These unprecedented results suggest that depressant toxins may have a toxic impact on mammals in the context of the complete scorpion venom. To assess whether LqhIT2 and Lqh-dprIT3 interact with the insect and rat muscle channels in a similar manner, we examined the role of Glu24, a conserved "hot spot" at the bioactive surface of beta-toxins. Whereas substitutions E24A/N abolished the activity of both LqhIT2 and Lqh-dprIT3 at insect Na(v)s, they increased the affinity of the toxins for rat skeletal muscle channels. This result implies that depressant toxins interact differently with the two channel types and that substitution of Glu24 is essential for converting toxin selectivity.
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Affiliation(s)
- Lior Cohen
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
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18
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De Lima ME, Figueiredo SG, Pimenta AMC, Santos DM, Borges MH, Cordeiro MN, Richardson M, Oliveira LC, Stankiewicz M, Pelhate M. Peptides of arachnid venoms with insecticidal activity targeting sodium channels. Comp Biochem Physiol C Toxicol Pharmacol 2007; 146:264-279. [PMID: 17218159 DOI: 10.1016/j.cbpc.2006.10.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 10/19/2006] [Accepted: 10/21/2006] [Indexed: 12/18/2022]
Abstract
Arachnids have a venom apparatus and secrete a complex chemical mixture of low molecular mass organic molecules, enzymes and polypeptide neurotoxins designed to paralyze or kill their prey. Most of these toxins are specific for membrane voltage-gated sodium channels, although some may also target calcium or potassium channels and other membrane receptors. Scorpions and spiders have provided the greatest number of the neurotoxins studied so far, for which, a good number of primary and 3D structures have been obtained. Structural features, comprising a folding that determines a similar spatial distribution of charged and hydrophobic side chains of specific amino acids, are strikingly common among the toxins from spider and scorpion venoms. Such similarities are, in turn, the key feature to target and bind these proteins to ionic channels. The search for new insecticidal compounds, as well as the study of their modes of action, constitutes a current approach to rationally design novel insecticides. This goal tends to be more relevant if the resistance to the conventional chemical products is considered. A promising alternative seems to be the biotechnological approach using toxin-expressing recombinant baculovirus. Spider and scorpion toxins having insecticidal activity are reviewed here considering their structures, toxicities and action mechanisms in sodium channels of excitable membranes.
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Affiliation(s)
- M E De Lima
- Lab. Venenos e Toxinas Animais, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil; Núcleo de Biomoléculas - Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil.
| | - S G Figueiredo
- Centro de Ciências Fisiológicas, CBM - Universidade Federal do Espírito Santo, Vitória, ES, Brasil
| | - A M C Pimenta
- Lab. Venenos e Toxinas Animais, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil; Núcleo de Biomoléculas - Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil
| | - D M Santos
- Lab. Venenos e Toxinas Animais, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil; Núcleo de Biomoléculas - Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil
| | - M H Borges
- Lab. Venenos e Toxinas Animais, Universidade Federal de Minas Gerais, 31.270-901, Belo Horizonte, MG, Brasil; Centro de Pesquisa Prof. Carlos R. Diniz, Fundação Ezequiel Dias, Belo Horizonte, MG, Brasil
| | - M N Cordeiro
- Centro de Pesquisa Prof. Carlos R. Diniz, Fundação Ezequiel Dias, Belo Horizonte, MG, Brasil
| | - M Richardson
- Centro de Pesquisa Prof. Carlos R. Diniz, Fundação Ezequiel Dias, Belo Horizonte, MG, Brasil
| | - L C Oliveira
- Departamento de Farmácia Bioquímica - Universidade Federal dos Vales do Jequitinhonha e Mucuri, 39100-000, Diamantina, MG, Brasil
| | - M Stankiewicz
- Laboratory of Biophysics - Institute of General and Molecular Biology, N. Copernicus University, 87-100, Torun, Poland
| | - M Pelhate
- Lab. Récepteurs et Canaux Ioniques Membranaires, Université d'Angers, 49045, Angers, France
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Dong K. Insect sodium channels and insecticide resistance. INVERTEBRATE NEUROSCIENCE : IN 2007; 7:17-30. [PMID: 17206406 PMCID: PMC3052376 DOI: 10.1007/s10158-006-0036-9] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 12/12/2006] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels are essential for the generation and propagation of action potentials (i.e., electrical impulses) in excitable cells. Although most of our knowledge about sodium channels is derived from decades of studies of mammalian isoforms, research on insect sodium channels is revealing both common and unique aspects of sodium channel biology. In particular, our understanding of the molecular dynamics and pharmacology of insect sodium channels has advanced greatly in recent years, thanks to successful functional expression of insect sodium channels in Xenopus oocytes and intensive efforts to elucidate the molecular basis of insect resistance to insecticides that target sodium channels. In this review, I discuss recent literature on insect sodium channels with emphases on the prominent role of alternative splicing and RNA editing in the generation of functionally diverse sodium channels in insects and the current understanding of the interactions between insect sodium channels and insecticides.
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Affiliation(s)
- Ke Dong
- Department of Entomology, Genetics Program and Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA.
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20
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Gurevitz M, Karbat I, Cohen L, Ilan N, Kahn R, Turkov M, Stankiewicz M, Stühmer W, Dong K, Gordon D. The insecticidal potential of scorpion β-toxins. Toxicon 2007; 49:473-89. [PMID: 17197009 DOI: 10.1016/j.toxicon.2006.11.015] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 11/20/2006] [Indexed: 11/28/2022]
Abstract
Voltage-gated sodium channels are a major target for toxins and insecticides due to their central role in excitability, but due to the conservation of these channels in Animalia most insecticides do not distinguish between those of insects and mammals, thereby imposing risks to humans and livestock. Evidently, as long as modern agriculture depends heavily on the use of insecticides there is a great need for new substances capable of differentiating between sodium channel subtypes. Such substances exist in venomous animals, but ways for their exploitation have not yet been developed due to problems associated with manufacturing, degradation, and delivery to the target channels. Engineering of plants for expression of anti-insect toxins or use of natural vectors that express toxins near their target site (e.g. baculoviruses) are still problematic and raise public concern. In this problematic reality a rational approach might be to learn from nature how to design highly selective anti-insect compounds preferably in the form of peptidomimetics. This is a complex task that requires the elucidation of the face of interaction between insect-selective toxins and their sodium channel receptor sites. This review delineates current progress in: (i) elucidation of the bioactive surfaces of scorpion beta-toxins, especially the excitatory and depressant groups, which show high preference for insects and bind insect sodium channels with high affinity; (ii) studies of the mode of interaction of scorpion beta-toxins with receptor site-4 on voltage-gated sodium channels; and (iii) clarification of channel elements that constitute receptor site-4. This information may be useful in future attempts to mimic the bioactive surface of the toxins for the design of anti-insect selective peptidomimetics.
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Affiliation(s)
- Michael Gurevitz
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel.
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21
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Abstract
Cancer, in general, is considered a disease of genetic mutation. Many questions are, however, unanswered. How exactly do mutations occur in the cells? How do gene mutations interface with the cell microenvironment and macroenvironment to create cancer phenotypes? Is mutation the cause of cancer or the consequence of special adaptive responses to aging; hormonal imbalance; physical, chemical and biologic stresses and damage? What makes cancer spread in the body and invade other organs causing death to the patient? In this paper, we hypothesize that the cellular hyperexcitability via stimulation of mineral channels (e.g. sodium voltage-gated channels) and ligand excitatory receptors (e.g. glutamate and other neuron and non-neuronal excitatory receptors) could be a significant causative and pathogenic factor of cancer. Managing hyperexcitatory states of the cells through lifestyle, nutritional changes, phytochemical and pharmaceutical medications theoretically could be a prospective direction in cancer prevention and therapy.
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Affiliation(s)
- Ba X Hoang
- Allergy Research Group Inc, Alameda, CA, USA
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de la Vega RCR, Possani LD. Novel paradigms on scorpion toxins that affects the activating mechanism of sodium channels. Toxicon 2007; 49:171-80. [PMID: 17081580 DOI: 10.1016/j.toxicon.2006.09.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Scorpion toxins classified as beta-class are reviewed using a new paradigm. Four distinct sub types are recognized: "classical", "Tsgamma-like", "excitatory" and "depressant"beta-scorpion toxins. Recent experimental data have made possible to identify the interacting interfaces of the Na(+) channel-receptor site 4 with some of these toxins. The voltage-sensor trapping mechanism proposed for the action of these toxic peptides is analyzed in the context of what causes a modification of the activating mechanism of Na(+) channels. A cartoon model is presented with the purpose of summarizing the most current knowledge on the field. Finally, the recent advances on the knowledge of the specific interactions of beta-toxins and different sub types of Na(+) channels are also reviewed.
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Affiliation(s)
- Ricardo C Rodríguez de la Vega
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Av. Universidad 2001, Cuernavaca Morelos 62210, México.
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23
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Leipold E, Hansel A, Borges A, Heinemann SH. Subtype specificity of scorpion beta-toxin Tz1 interaction with voltage-gated sodium channels is determined by the pore loop of domain 3. Mol Pharmacol 2006; 70:340-7. [PMID: 16638971 DOI: 10.1124/mol.106.024034] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated sodium (Nav) channels are modulated by a variety of specific neurotoxins. Scorpion beta-toxins affect the voltage-dependence of channel gating: In their presence, Nav channels activate at subthreshold membrane voltages. Previous mutagenesis studies have revealed that the beta-toxin Css4 interacts with the extracellular linker between segments 3 and 4 in domain 2 of Nav channels with the effect to trap this voltage sensor in an open position (Neuron 21: 919-931, 1998 ). The voltage sensor of domain 2 was thus identified to constitute a major part of neurotoxin receptor site 4. In this work, we studied the effects of the beta-toxin Tz1 from the Venezuelan scorpion Tityus zulianus on various mammalian Nav channel types expressed in HEK 293 cells. Although skeletal muscle channels (Nav1.4) were strongly affected by Tz1, the neuronal channels Nav1.6 and Nav1.2 were less sensitive, and the cardiac Nav1.5 and the peripheral nerve channel Nav1.7 were essentially insensitive. Analysis of channel chimeras in which whole domains of Nav1.2 were inserted into a Nav1.4 background revealed that the Nav1.2 phenotype was not conferred to Nav1.4 by domain 2 but by domain 3. The interaction epitope could be narrowed down to residues Glu1251, Lys1252, and His1257 located in the C-terminal pore loop in domain 3. The receptor site for beta-toxin interaction with Nav channels thus spans domains 2 and 3, where the pore loop in domain 3 specifies the pharmacological properties of individual neuronal Nav channel types.
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Affiliation(s)
- Enrico Leipold
- Institute of Molecular Cell Biology, Molecular and Cellular Biophysics, Friedrich Schiller University Jena, Drackendorfer Str. 1, D-07747 Jena, Germany
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Rodríguez de la Vega RC, Possani LD. Overview of scorpion toxins specific for Na+ channels and related peptides: biodiversity, structure-function relationships and evolution. Toxicon 2005; 46:831-44. [PMID: 16274721 DOI: 10.1016/j.toxicon.2005.09.006] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Scorpion venoms contain a large number of bioactive components. Several of the long-chain peptides were shown to be responsible for neurotoxic effects, due to their ability to recognize Na(+) channels and to cause impairment of channel functions. Here, we revisited the basic paradigms in the study of these peptides in the light of recent data concerning their structure-function relationships, their functional divergence and extant biodiversity. The reviewed topics include: the criteria for classification of long-chain peptides according to their function, and a revision of the state-of-the-art knowledge concerning the surface areas of contact of these peptides with known Na(+) channels. Additionally, we compiled a comprehensive list encompassing 191 different amino acid sequences from long-chain peptides purified from scorpion venoms. With this dataset, a phylogenetic tree was constructed and discussed taking into consideration their documented functional divergence. A critical view on problems associated with the study of these scorpion peptides is presented, drawing special attention to the points that need revision and to the subjects under intensive research at this moment, regarding scorpion toxins specific for Na(+) channels and the other related long-chain peptides recently described.
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Affiliation(s)
- Ricardo C Rodríguez de la Vega
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Av. Universidad 2001, Apartado Postal 510-3, Cuernavaca Morelos 62210, Mexico
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