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Chen R, Chung SH. Binding Modes and Functional Surface of Anti-mammalian Scorpion α-Toxins to Sodium Channels. Biochemistry 2012; 51:7775-82. [DOI: 10.1021/bi300776g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Shin-Ho Chung
- Research School of Biology, Australian National University, Canberra, ACT 0200, Australia
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Abstract
Scorpion stings are common in many tropical countries. Although most scorpion stings cause only localized pain without life-threatening envenoming, about one third of stings cause systemic envenoming which can result in death. Children are particularly sensitive to scorpion envenoming. The severity of scorpion stings is related to the presence of neurotoxins in the venom that cause a sudden release of neurotransmitters from the autonomic nervous system, predominantly sympathetic. There is also a strong inflammatory response that worsens symptoms, including those of a respiratory nature. Several vital functions may be directly affected, including the cardiovascular, respiratory, and neuromuscular systems. Hypertension is constant at the beginning of systemic envenoming and sometimes has a severe cardiac and respiratory impact. Although controversial, immunotherapy is the only etiological treatment. Administered early, it prevents many complications and improves the outcome. New antivenoms are highly purified immunoglobulin fragments, the efficacy and safety of which are excellent. As a consequence, adverse reactions to antivenoms are now very rare and usually mild, which should limit any reluctance regarding their routine use. Symptomatic treatment is still necessary to support immunotherapy, especially in cases of delayed arrival at hospital. A combination of both approaches should be considered, based on local resources and constraints.
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Affiliation(s)
- Jean-Philippe Chippaux
- UMR 216 (Institute of Research for Development and University Paris Descartes, Sorbonne Paris Cité), Cotonou, Bénin, France.
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103
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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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104
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Näreoja K, Kukkonen JP, Rondinelli S, Toivola DM, Meriluoto J, Näsman J. Adrenoceptor activity of muscarinic toxins identified from mamba venoms. Br J Pharmacol 2012; 164:538-50. [PMID: 21557730 DOI: 10.1111/j.1476-5381.2011.01468.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Muscarinic toxins (MTs) are snake venom peptides named for their ability to interfere with ligand binding to muscarinic acetylcholine receptors (mAChRs). Recent data infer that these toxins may have other G-protein-coupled receptor targets than the mAChRs. The purpose of this study was to systematically investigate the interactions of MTs with the adrenoceptor family members. EXPERIMENTAL APPROACH We studied the interaction of four common MTs, MT1, MT3, MT7 and MTα, with cloned receptors expressed in insect cells by radioligand binding. Toxins showing modest to high-affinity interactions with adrenoceptors were additionally tested for effects on functional receptor responses by way of inhibition of agonist-induced Ca²⁺ increases. KEY RESULTS All MTs behaved non-competitively in radioligand displacement binding. MT1 displayed higher binding affinity for the human α(2B)-adrenoceptor (IC₅₀ = 2.3 nM) as compared with muscarinic receptors (IC₅₀ ≥ 100 nM). MT3 appeared to have a broad spectrum of targets showing high-affinity binding (IC₅₀ = 1-10 nM) to M₄ mAChR, α(1A)-, α(1D)- and α(2A)-adrenoceptors and lower affinity binding (IC₅₀ ≥ 25 nM) to α(1B)- and α(2C)-adrenoceptors and M₁ mAChR. MT7 did not detectably bind to other receptors than M₁, and MTα was specific for the α(2B)-adrenoceptor. None of the toxins showed effects on β₁- or β₂-adrenoceptors. CONCLUSIONS AND IMPLICATIONS Some of the MTs previously found to interact predominantly with mAChRs were shown to bind with high affinity to selected adrenoceptor subtypes. This renders these peptide toxins useful for engineering selective ligands to target various adrenoceptors.
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Affiliation(s)
- K Näreoja
- Department of Biosciences, Biochemistry, Åbo Akademi University, Turku, Finland
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105
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Identification and phylogenetic analysis of Tityus pachyurus and Tityus obscurus novel putative Na+-channel scorpion toxins. PLoS One 2012; 7:e30478. [PMID: 22355312 PMCID: PMC3280238 DOI: 10.1371/journal.pone.0030478] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 12/16/2011] [Indexed: 11/19/2022] Open
Abstract
Background Colombia and Brazil are affected by severe cases of scorpionism. In Colombia the most dangerous accidents are caused by Tityus pachyurus that is widely distributed around this country. In the Brazilian Amazonian region scorpion stings are a common event caused by Tityus obscurus. The main objective of this work was to perform the molecular cloning of the putative Na+-channel scorpion toxins (NaScTxs) from T. pachyurus and T. obscurus venom glands and to analyze their phylogenetic relationship with other known NaScTxs from Tityus species. Methodology/Principal Findings cDNA libraries from venom glands of these two species were constructed and five nucleotide sequences from T. pachyurus were identified as putative modulators of Na+-channels, and were named Tpa4, Tpa5, Tpa6, Tpa7 and Tpa8; the latter being the first anti-insect excitatory β-class NaScTx in Tityus scorpion venom to be described. Fifteen sequences from T. obscurus were identified as putative NaScTxs, among which three had been previously described, and the others were named To4 to To15. The peptides Tpa4, Tpa5, Tpa6, To6, To7, To9, To10 and To14 are closely related to the α-class NaScTxs, whereas Tpa7, Tpa8, To4, To8, To12 and To15 sequences are more related to the β-class NaScTxs. To5 is possibly an arthropod specific toxin. To11 and To13 share sequence similarities with both α and β NaScTxs. By means of phylogenetic analysis using the Maximum Parsimony method and the known NaScTxs from Tityus species, these toxins were clustered into 14 distinct groups. Conclusions/Significance This communication describes new putative NaScTxs from T. pachyurus and T. obscurus and their phylogenetic analysis. The results indicate clear geographic separation between scorpions of Tityus genus inhabiting the Amazonian and Mountain Andes regions and those distributed over the Southern of the Amazonian rainforest. Based on the consensus sequences for the different clusters, a new nomenclature for the NaScTxs is proposed.
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106
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Zhu S, Peigneur S, Gao B, Lu X, Cao C, Tytgat J. Evolutionary diversification of Mesobuthus α-scorpion toxins affecting sodium channels. Mol Cell Proteomics 2011; 11:M111.012054. [PMID: 21969612 DOI: 10.1074/mcp.m111.012054] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α-Scorpion toxins constitute a family of peptide modulators that induce a prolongation of the action potential of excitable cells by inhibiting voltage-gated sodium channel inactivation. Although they all adopt a conserved structural scaffold, the potency and phylogentic preference of these toxins largely vary, which render them an intriguing model for studying evolutionary diversification among family members. Here, we report molecular characterization of a new multigene family of α-toxins comprising 13 members (named MeuNaTxα-1 to MeuNaTxα-13) from the scorpion Mesobuthus eupeus. Of them, five native toxins (MeuNaTxα-1 to -5) were purified to homogeneity from the venom and the solution structure of MeuNaTxα-5 was solved by nuclear magnetic resonance. A systematic functional evaluation of MeuNaTxα-1, -2, -4, and -5 was conducted by two-electrode voltage-clamp recordings on seven cloned mammalian voltage-gated sodium channels (Na(v)1.2 to Na(v)1.8) and the insect counterpart DmNa(v)1 expressed in Xenopus oocytes. Results show that all these four peptides slow inactivation of DmNa(v)1 and are inactive on Na(v)1.8 at micromolar concentrations. However, they exhibit differential specificity for the other six channel isoforms (Na(v)1.2 to Na(v)1.7), in which MeuNaTxα-4 shows no activity on these isoforms and thus represents the first Mesobuthus-derived insect-selective α-toxin identified so far with a half maximal effective concentration of 130 ± 2 nm on DmNa(v)1 and a half maximal lethal dose of about 200 pmol g(-1) on the insect Musca domestica; MeuNaTxα-2 only affects Na(v)1.4; MeuNaTxα-1 and MeuNaTxα-5 have a wider range of channel spectrum, the former active on Na(v)1.2, Na(v)1.3, Na(v)1.6, and Na(v)1.7, whereas the latter acting on Na(v)1.3-Na(v)1.7. Remarkably, MeuNaTxα-4 and MeuNaTxα-5 are two nearly identical peptides differing by only one point mutation at site 50 (A50V) but exhibit rather different channel subtype selectivity, highlighting a switch role of this site in altering the target specificity. By the maximum likelihood models of codon substitution, we detected nine positively selected sites (PSSs) that could be involved in functional diversification of Mesobuthus α-toxins. The PSSs include site 50 and other seven sites located in functional surfaces of α-toxins. This work represents the first thorough investigation of evolutionary diversification of α-toxins derived from a specific scorpion lineage from the perspectives of sequence, structure, function, and evolution.
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Affiliation(s)
- Shunyi Zhu
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing 100101, China.
| | - Steve Peigneur
- Laboratory of Toxicology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium
| | - Bin Gao
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing 100101, China
| | - Xiuxiu Lu
- State Key Laboratory of Bio-organic and Natural Product Chemistry Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Chunyang Cao
- State Key Laboratory of Bio-organic and Natural Product Chemistry Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Jan Tytgat
- Laboratory of Toxicology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium
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107
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András CD, Albert C, Salamon S, Gálicza J, András R, András E. Conus magus vs. Irukandji syndrome: A computational approach of a possible new therapy. Brain Res Bull 2011; 86:195-202. [DOI: 10.1016/j.brainresbull.2011.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 07/03/2011] [Accepted: 07/05/2011] [Indexed: 01/22/2023]
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108
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Rowe AH, Xiao Y, Scales J, Linse KD, Rowe MP, Cummins TR, Zakon HH. Isolation and characterization of CvIV4: a pain inducing α-scorpion toxin. PLoS One 2011; 6:e23520. [PMID: 21887265 PMCID: PMC3160894 DOI: 10.1371/journal.pone.0023520] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 07/19/2011] [Indexed: 12/03/2022] Open
Abstract
Background Among scorpion species, the Buthidae produce the most deadly and painful venoms. However, little is known regarding the venom components that cause pain and their mechanism of action. Using a paw-licking assay (Mus musculus), this study compared the pain-inducing capabilities of venoms from two species of New World scorpion (Centruroides vittatus, C. exilicauda) belonging to the neurotoxin-producing family Buthidae with one species of non-neurotoxin producing scorpion (Vaejovis spinigerus) in the family Vaejovidae. A pain-inducing α-toxin (CvIV4) was isolated from the venom of C. vittatus and tested on five Na+ channel isoforms. Principal Findings C. vittatus and C. exilicauda venoms produced significantly more paw licking in Mus than V. spinigerus venom. CvIV4 produced paw licking in Mus equivalent to the effects of whole venom. CvIV4 slowed the fast inactivation of Nav1.7, a Na+ channel expressed in peripheral pain-pathway neurons (nociceptors), but did not affect the Nav1.8-based sodium currents of these neurons. CvIV4 also slowed the fast inactivation of Nav1.2, Nav1.3 and Nav1.4. The effects of CvIV4 are similar to Old World α-toxins that target Nav1.7 (AahII, BmK MI, LqhIII, OD1), however the primary structure of CvIV4 is not similar to these toxins. Mutant Nav1.7 channels (D1586A and E1589Q, DIV S3–S4 linker) reduced but did not abolish the effects of CvIV4. Conclusions This study: 1) agrees with anecdotal evidence suggesting that buthid venom is significantly more painful than non-neurotoxic venom; 2) demonstrates that New World buthids inflict painful stings via toxins that modulate Na+ channels expressed in nociceptors; 3) reveals that Old and New World buthids employ similar mechanisms to produce pain. Old and New World α-toxins that target Nav1.7 have diverged in sequence, but the activity of these toxins is similar. Pain-inducing toxins may have evolved in a common ancestor. Alternatively, these toxins may be the product of convergent evolution.
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Affiliation(s)
- Ashlee H Rowe
- Section of Neurobiology, University of Texas at Austin, Austin, Texas, United States of America.
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109
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Gao B, Zhu L, Zhu S. A naturally-occurring carboxyl-terminally truncated α-scorpion toxin is a blocker of sodium channels. Biochem Biophys Res Commun 2011; 411:673-8. [PMID: 21763288 DOI: 10.1016/j.bbrc.2011.06.178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 06/29/2011] [Indexed: 11/17/2022]
Abstract
α-Scorpion toxins constitute a multigene family of evolutionarily conserved venom peptides that inhibit sodium channel inactivation and increase its peak current. Here, we describe the characterization of a new α-scorpion toxin gene expressed in the venom gland of Mesobuthus eupeus that encodes a carboxyl-terminally truncated product of 38 residues (named MeuNaTxα(NT)-1). Synthetic MeuNaTxα(NT)-1 was oxidized to form two disulfide bridges in an alkaline environment and the refolded peptide exhibits different structure and function from the classical α-scorpion toxin. MeuNaTxα(NT)-1 blocks sodium channels on rat dorsal root ganglia (DRG) neurons without impact on the inactivation of the channels. This work provides a clue for evolution-guided design of channel blockers for therapeutic aims.
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Affiliation(s)
- Bin Gao
- Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Chaoyang District, Beijing, China
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110
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Biochemical and molecular characterization of the venom from the Cuban scorpion Rhopalurus junceus. Toxicon 2011; 58:18-27. [DOI: 10.1016/j.toxicon.2011.04.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/17/2011] [Accepted: 04/12/2011] [Indexed: 11/21/2022]
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111
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Abstract
Scorpion envenomation is a dangerous and common global event that can result in a variety of toxic clinical effects. These are typically managed with supportive care or antivenom. Antivenom use is controversial because of conflicting evidence of effectiveness for adrenergic toxicity. However, both controlled and uncontrolled studies have shown that antivenom is effective in resolving neuromotor toxicity associated with envenomations by the scorpions of genus Centruroides.
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112
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Action potentials in primary osteoblasts and in the MG-63 osteoblast-like cell line. J Bioenerg Biomembr 2011; 43:311-22. [PMID: 21523406 DOI: 10.1007/s10863-011-9354-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2011] [Accepted: 04/03/2011] [Indexed: 01/25/2023]
Abstract
Whole-cell patch-clamp analysis revealed a resting membrane potential of -60 mV in primary osteoblasts and in the MG-63 osteoblast-like cells. Depolarization-induced action potentials were characterized by duration of 60 ms, a minimal peak-to-peak distance of 180 ms, a threshold value of -20 mV and a repolarization between the spikes to -45 mV. Expressed channels were characterized by application of voltage pulses between -150 mV and 90 mV in 10 mV steps, from a holding potential of -40 mV. Voltages below -60 mV induced an inward current. Depolarizing voltages above -30 mV evoked two currents: (a) a fast activated and inactivated inward current at voltages between -30 and 30 mV, and (b) a delayed-activated outward current that was induced by voltages above -30 mV. Electrophysiological and pharmacological parameters indicated that hyperpolarization activated strongly rectifying K(+) (K(ir)) channels, whereas depolarization activated tetrodotoxin sensitive voltage gated Na(+) (Na(v)) channels as well as delayed, slowly activated, non-inactivating, and tetraethylammonium sensitive voltage gated K(+) (K(v)) channels. In addition, RT-PCR showed expression of Na(v)1.3, Na(v)1.4, Na(v)1.5, Na(v)1.6, Na(v)1.7, and K(ir)2.1, K(ir)2.3, and K(ir)2.4 as well as K(v)2.1. We conclude that osteoblasts express channels that allow firing of action potentials.
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113
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Cusinato DAC, Souza AM, Vasconcelos F, Guimarães LFL, Leite FP, Gregório ZMO, Giglio JR, Arantes EC. Assessment of biochemical and hematological parameters in rats injected with Tityus serrulatus scorpion venom. Toxicon 2010; 56:1477-86. [PMID: 20837041 DOI: 10.1016/j.toxicon.2010.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 09/01/2010] [Accepted: 09/03/2010] [Indexed: 10/19/2022]
Abstract
The aim of this work was to evaluate the hematological changes induced by Tityus serrulatus venom (TsV). Blood of Wistar rats was collected 0.5, 2, 6 and 24 h after i.p. injection of TsV (0.5 mg/kg) or saline (controls). Two additional groups were injected with 0.67 mg/kg and 0.25 mg/kg of TsV and the blood was collected after 0.5 and 2 h, respectively. The results showed an increase on hematocrit (Ht), red blood cells (RBC) count, hemoglobin concentration (Hb), albumin and total protein, mainly 2-6 h after envenoming. Increase in serum activities of amylase, creatine kinase and aspartate aminotransferase were also observed, indicating tecidual damages. Hyperglycemia was observed at all times analyzed, as a consequence of catecholamine release. No significant changes were detected in the urea, [Na(+)] and [Ca(2+)], but an increase of [Mg(2+)], [K(+)] and conductivity was observed. TsV induced a reduction of erythrocytes osmotic fragility as consequence of dehydration and increase in plasma electrolytes concentration, as evidenced by its higher conductivity. This study demonstrated that TsV is able to induce severe hematological changes, that appear within the first hours after envenoming, justifying the seeking of medical attention as soon as possible to avoid worsening of clinical symptoms.
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Affiliation(s)
- D A C Cusinato
- Depto. Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto - USP, Av. do Café, s/n, 14040-903 Ribeirão Preto-SP, Brazil
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114
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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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115
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Holford M, Auer S, Laqua M, Ibañez-Tallon I. Manipulating neuronal circuits with endogenous and recombinant cell-surface tethered modulators. Front Mol Neurosci 2009; 2:21. [PMID: 19915728 PMCID: PMC2776481 DOI: 10.3389/neuro.02.021.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 10/10/2009] [Indexed: 11/26/2022] Open
Abstract
Neuronal circuits depend on the precise regulation of cell-surface receptors and ion channels. An ongoing challenge in neuroscience research is deciphering the functional contribution of specific receptors and ion channels using engineered modulators. A novel strategy, termed “tethered toxins”, was recently developed to characterize neuronal circuits using the evolutionary derived selectivity of venom peptide toxins and endogenous peptide ligands, such as lynx1 prototoxins. Herein, the discovery and engineering of cell-surface tethered peptides is reviewed, with particular attention given to their cell-autonomy, modular composition, and genetic targeting in different model organisms. The relative ease with which tethered peptides can be engineered, coupled with the increasing number of neuroactive venom toxins and ligand peptides being discovered, imply a multitude of potentially innovative applications for manipulating neuronal circuits and tissue-specific cell networks, including treatment of disorders caused by malfunction of receptors and ion channels.
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Affiliation(s)
- Mandë Holford
- York College and The Graduate Center, The American Museum of Natural History, The City University of New York New York, NY, USA
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116
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Bhattacharya A, Wickenden AD, Chaplan SR. Sodium channel blockers for the treatment of neuropathic pain. Neurotherapeutics 2009; 6:663-78. [PMID: 19789071 PMCID: PMC5084288 DOI: 10.1016/j.nurt.2009.08.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Drugs that block voltage-gated sodium channels are efficacious in the management of neuropathic pain. Accordingly, this class of ion channels has been a major focus of analgesic research both in academia and in the pharmaceutical/biotechnology industry. In this article, we review the history of the use of sodium channel blockers, describe the current status of sodium channel drug discovery, highlight the challenges and hurdles to attain sodium channel subtype selectivity, and review the potential usefulness of selective sodium channel blockers in neuropathic pain.
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Affiliation(s)
- Anindya Bhattacharya
- grid.417429.dPain & Related Disorders Team, Johnson & Johnson Pharmaceutical Research & Development, LLC, 3210 Merryfield Row, 92121 San Diego, CA
| | - Alan D. Wickenden
- grid.417429.dPain & Related Disorders Team, Johnson & Johnson Pharmaceutical Research & Development, LLC, 3210 Merryfield Row, 92121 San Diego, CA
| | - Sandra R. Chaplan
- grid.417429.dPain & Related Disorders Team, Johnson & Johnson Pharmaceutical Research & Development, LLC, 3210 Merryfield Row, 92121 San Diego, CA
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117
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Effects of scorpion toxin on excitatory and inhibitory presynaptic terminals. Toxicology 2009; 264:198-204. [DOI: 10.1016/j.tox.2009.08.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/08/2009] [Accepted: 08/10/2009] [Indexed: 11/15/2022]
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118
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Full characterization of three toxins from the Androctonus amoreuxi scorpion venom. Toxicon 2009; 54:460-70. [DOI: 10.1016/j.toxicon.2009.05.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 05/05/2009] [Accepted: 05/16/2009] [Indexed: 12/19/2022]
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Zhu MM, Tan M, Cheng HW, Ji YH. The α-like scorpion toxin BmK I enhances membrane excitability via persistent sodium current by preventing slow inactivation and deactivation of rNav1.2a expressed in Xenopus Oocytes. Toxicol In Vitro 2009; 23:561-8. [DOI: 10.1016/j.tiv.2008.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 10/13/2008] [Accepted: 12/17/2008] [Indexed: 10/21/2022]
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120
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Servent D, Fruchart-Gaillard C. Muscarinic toxins: tools for the study of the pharmacological and functional properties of muscarinic receptors. J Neurochem 2009; 109:1193-202. [PMID: 19457160 DOI: 10.1111/j.1471-4159.2009.06092.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Muscarinic receptors mediate metabotropic actions of acetylcholine in the CNS and PNS and autocrine functions of acetylcholine in non-neuronal systems. Because of the lack of highly selective muscarinic ligands, the precise location, functional role, and roles in various diseases of the five muscarinic receptor subtypes remain unclear. Muscarinic toxins isolated from the venom of Dendroaspis snakes have a natural high affinity and selectivity, associated with roles as competitive antagonists, allosteric modulators, and potential agonists. These toxins may therefore be invaluable tools for studying muscarinic receptors. We review data on the structural and pharmacological characterization of the muscarinic toxins, focusing on recent structure-function studies on toxin-receptor interactions. We discuss the potential benefits of using these toxins for investigating muscarinic function in vivo.
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Affiliation(s)
- Denis Servent
- CEA, iBiTecS, Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), Gif sur Yvette, France.
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121
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Wang Z, Wang W, Shao Z, Gao B, Li J, Ma J, Li J, Che H, Zhang W. Eukaryotic expression and purification of anti-epilepsy peptide of Buthus martensii Karsch and its protein interactions. Mol Cell Biochem 2009; 330:97-104. [PMID: 19370317 DOI: 10.1007/s11010-009-0104-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 03/30/2009] [Indexed: 11/28/2022]
Abstract
The Asian scorpion Buthus martensil Karsch is important in the Chinese traditional medicine where it is used for the treatment of some nervous system diseases. The anti-epilepsy peptide (AEP) is a 61-amino-acid polypeptide extracted from the venom of B. martensil Karsch. Research has confirmed that it has anti-epileptic effects on the rat model of epilepsy. In this experiment, a cDNA library of AEP from the venom of B. martensil Karsch was constructed using RT-PCR; the primer was designed and used for the amplification. An expression vector of AEP was constructed using Pichia pastoris. Vector expression was induced, and protein purification was then performed. Bolting of the interaction molecule of AEP was by His pull down. Experimental results indicate high AEP expression, and the obtained protein was purified and compared with the control group. Four conspicuous protein bands were observed, and mass chromatographic analysis indicated that the four proteins were synaptosomal-associated protein of 25 kDa (SNAP-25), glial fibrillary acidic protein (GFAP), Glutamic acid decarboxylase (GAD) and N-methyl-D: -aspartate (NMDA). Further, the four protein bands were verified by mammalian two-hybrid experiments and co-immunoprecipitation. AEP was found to interact with SNAP2 and NMDA. This provides experimental evidence for the mechanism of AEP's anti-epileptic action and for the manufacture of a novel type anti-epileptic drug.
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Affiliation(s)
- Zongren Wang
- Department of Traditional Chinese Medicine, Xijing Hospital, The Forth Military Medical University, Xi'an, Shaanxi, 710032, People's Republic of China.
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122
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Guidine PAM, Mesquita MBS, Moraes-Santos T, Massensini AR, Moraes MFD. Electroencephalographic evidence of brainstem recruitment during scorpion envenomation. Neurotoxicology 2009; 30:90-6. [DOI: 10.1016/j.neuro.2008.10.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 10/06/2008] [Accepted: 10/07/2008] [Indexed: 10/21/2022]
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123
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Docherty RJ, Farmer CE. The pharmacology of voltage-gated sodium channels in sensory neurones. Handb Exp Pharmacol 2009:519-61. [PMID: 19655117 DOI: 10.1007/978-3-540-79090-7_15] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels (VGSCs) are vital for the normal functioning of most excitable cells. At least nine distinct functional subtypes of VGSCs are recognized, corresponding to nine genes for their pore-forming alpha-subunits. These have different developmental expression patterns, different tissue distributions in the adult and are differentially regulated at the cellular level by receptor-coupled cell signalling systems. Unsurprisingly, VGSC blockers are found to be useful as drugs in diverse clinical applications where excessive excitability of tissue leads to pathological dysfunction, e.g. epilepsy or cardiac tachyarrhythmias. The effects of most clinically useful VGSC blockers are use-dependent, i.e. their efficacy depends on channel activity. In addition, many natural toxins have been discovered that interact with VGSCs in complex ways and they have been used as experimental probes to study the structure and function of the channels and to better understand how drugs interact with the channels. Here we have attempted to summarize the properties of VGSCs in sensory neurones, discuss how they are regulated by cell signalling systems and we have considered briefly current concepts of their physiological function. We discuss in detail how drugs and toxins interact with archetypal VGSCs and where possible consider how they act on VGSCs in peripheral sensory neurones. Increasingly, drugs that block VGSCs are being used as systemic analgesic agents in chronic pain syndromes, but the full potential for VGSC blockers in this indication is yet to be realized and other applications in sensory dysfunction are also possible. Drugs targeting VGSC subtypes in sensory neurones are likely to provide novel systemic analgesics that are tissue-specific and perhaps even disease-specific, providing much-needed novel therapeutic approaches for the relief of chronic pain.
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Affiliation(s)
- Reginald J Docherty
- Neurorestoration Group, Wolfson CARD, King's College London, London SE1 9RT, UK.
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124
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Guidine PAM, Moraes-Santos T, Massensini AR, Moraes MFD. Carbamazepine is effective in the treatment of 21-day-old Wistar rats injected with Tityus serrulatus crude venom. Brain Res 2008; 1239:256-60. [PMID: 18760265 DOI: 10.1016/j.brainres.2008.08.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2008] [Revised: 08/07/2008] [Accepted: 08/08/2008] [Indexed: 10/21/2022]
Abstract
The scorpion-envenoming syndrome has an incidence of approximately 8000 accidents/year in Brazil; with most severe cases occurring during childhood and elderly. Previous results from our laboratory suggest that the effects of scorpion toxins on the central nervous system play a major role on the lethality induced by scorpion envenoming. Our group has shown that the pre-treatment with carbamazepine (CBZ) is able to increase the latency-to-death in developing animals inoculated with tityustoxin, a toxic fraction of the Tityus serrulatus crude venom. Nevertheless, in order to perceive CBZ as potentially useful in clinical practice, the efficiency of CBZ against crude venom inoculation and the pharmacological treatment introduced after envenomation must be addressed. Thus, the objective of this work was to evaluate CBZ therapeutic efficiency against scorpion envenomation in developing rats. Animals were treated with i.p. injections of either vehicle or CBZ (50 mg/kg or 100 mg/kg) 10 min after injected with a s.c. fixed volume of either saline or crude T. serrulatus venom extract (48 mg/kg). The dose chosen for venom inoculation was 16 times its DL50 for 21-day-old Wistar rats, invariably inducing death within 2 h. Although CBZ did not significantly reduce the pulmonary edema, it was effective in increasing survival rate by approximately 75% in treated rats. In conclusion, CBZ was effective in the treatment of T. serrulatus envenomation even though not blocking the pulmonary edema.
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Affiliation(s)
- Patrícia Alves Maia Guidine
- Núcleo de Neurociências (NNC), Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, Pampulha, 31270 901 Belo Horizonte, Minas Gerais, Brazil
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125
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Billen B, Vassilevski A, Nikolsky A, Tytgat J, Grishin E. Two novel sodium channel inhibitors from Heriaeus melloteei spider venom differentially interacting with mammalian channel's isoforms. Toxicon 2008; 52:309-17. [DOI: 10.1016/j.toxicon.2008.05.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 05/20/2008] [Accepted: 05/30/2008] [Indexed: 12/19/2022]
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126
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127
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Guidine PAM, Moraes-Santos T, Massensini AR, Moraes MFD. Carbamazepine protects the CNS of Wistar rats against the central effects of scorpion envenomation. Neurotoxicology 2008; 29:136-42. [DOI: 10.1016/j.neuro.2007.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Revised: 10/01/2007] [Accepted: 10/09/2007] [Indexed: 10/22/2022]
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128
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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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129
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Xiao Y, Luo X, Kuang F, Deng M, Wang M, Zeng X, Liang S. Synthesis and characterization of huwentoxin-IV, a neurotoxin inhibiting central neuronal sodium channels. Toxicon 2007; 51:230-9. [PMID: 18054060 DOI: 10.1016/j.toxicon.2007.09.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Revised: 09/18/2007] [Accepted: 09/25/2007] [Indexed: 10/22/2022]
Abstract
Our previous work demonstrated that huwentoxin-IV was an inhibitor cystine knot peptide from Chinese tarantula Ornithoctonus huwena venom that blocked tetrodotoxin-sensitive voltage-gated sodium channels from mammalian sensory neurons [Peng, K., Shu, Q., Liu, Z., Liang, S., 2002. Function and solution structure of huwentoxin-IV, a potent neuronal tetrodotoxin (TTX)-sensitive sodium channel antagonist from Chinese bird spider Selenocosmia huwena. J. Biol. Chem. 277(49), 47564-47571]. However, the actions of the neurotoxin on central neuronal sodium channels remain unknown. In this study, we chemically synthesized native huwentoxin-IV and found that sodium channel isoforms from rat hippocampus neurons were also sensitive to native and synthetic toxins, but the toxin-binding affinity (IC(50) approximately 0.4 microM) was 12-fold lower than to peripheral isoforms. The blockade by huwentoxin-IV could be reversed by strong depolarization due to the dissociation of toxin-channel complex as observed for receptor site 3 toxins. Moreover, small unilamellar vesicle-binding assays showed that in contrast to ProTx-II from the tarantula Thrixopelma pruriens, huwentoxin-IV almost lacked the ability to partition into the negatively charged and neutral phospholipid bilayer of artificial membranes. These findings indicated that huwentoxin-IV was a sodium channel antagonist preferentially targeting peripheral isoforms via a mechanism quite different from ProTx-II.
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Affiliation(s)
- Yucheng Xiao
- Life Sciences College, Hunan Normal University, Changsha, Hunan 410081, PR China
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130
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Moran Y, Kahn R, Cohen L, Gur M, Karbat I, Gordon D, Gurevitz M. Molecular analysis of the sea anemone toxin Av3 reveals selectivity to insects and demonstrates the heterogeneity of receptor site-3 on voltage-gated Na+ channels. Biochem J 2007; 406:41-8. [PMID: 17492942 PMCID: PMC1948988 DOI: 10.1042/bj20070233] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Av3 is a short peptide toxin from the sea anemone Anemonia viridis shown to be active on crustaceans and inactive on mammals. It inhibits inactivation of Na(v)s (voltage-gated Na+ channels) like the structurally dissimilar scorpion alpha-toxins and type I sea anemone toxins that bind to receptor site-3. To examine the potency and mode of interaction of Av3 with insect Na(v)s, we established a system for its expression, mutagenized it throughout, and analysed it in toxicity, binding and electrophysiological assays. The recombinant Av3 was found to be highly toxic to blowfly larvae (ED50=2.65+/-0.46 pmol/100 mg), to compete well with the site-3 toxin LqhalphaIT (from the scorpion Leiurus quinquestriatus) on binding to cockroach neuronal membranes (K(i)=21.4+/-7.1 nM), and to inhibit the inactivation of Drosophila melanogaster channel, DmNa(v)1, but not that of mammalian Na(v)s expressed in Xenopus oocytes. Moreover, like other site-3 toxins, the activity of Av3 was synergically enhanced by ligands of receptor site-4 (e.g. scorpion beta-toxins). The bioactive surface of Av3 was found to consist mainly of aromatic residues and did not resemble any of the bioactive surfaces of other site-3 toxins. These analyses have portrayed a toxin that might interact with receptor site-3 in a different fashion compared with other ligands of this site. This assumption was corroborated by a D1701R mutation in DmNa(v)1, which has been shown to abolish the activity of all other site-3 ligands, except Av3. All in all, the present study provides further evidence for the heterogeneity of receptor site-3, and raises Av3 as a unique model for design of selective anti-insect compounds.
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Affiliation(s)
- Yehu Moran
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Roy Kahn
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Lior Cohen
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Maya Gur
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Izhar Karbat
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Dalia Gordon
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
- Correspondence may be addressed to either of these authors (email or )
| | - Michael Gurevitz
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
- Correspondence may be addressed to either of these authors (email or )
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