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Simone Y, van der Meijden A. Armed stem to stinger: a review of the ecological roles of scorpion weapons. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20210002. [PMID: 34527038 PMCID: PMC8425188 DOI: 10.1590/1678-9199-jvatitd-2021-0002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 03/18/2021] [Indexed: 12/24/2022] Open
Abstract
Scorpions possess two systems of weapons: the pincers (chelae) and the stinger (telson). These are placed on anatomically and developmentally well separated parts of the body, that is, the oral appendages and at the end of the body axis. The otherwise conserved body plan of scorpions varies most in the shape and relative dimensions of these two weapon systems, both across species and in some cases between the sexes. We review the literature on the ecological function of these two weapon systems in each of three contexts of usage: (i) predation, (ii) defense and (iii) sexual contests. In the latter context, we will also discuss their usage in mating. We first provide a comparative background for each of these contexts of usage by giving examples of other weapon systems from across the animal kingdom. Then, we discuss the pertinent aspects of the anatomy of the weapon systems, particularly those aspects relevant to their functioning in their ecological roles. The literature on the functioning and ecological role of both the chelae and the telson is discussed in detail, again organized by context of usage. Particular emphasis is given on the differences in morphology or usage between species or higher taxonomic groups, or between genders, as such cases are most insightful to understand the roles of each of the two distinct weapon systems of the scorpions and their evolutionary interactions. We aimed to synthesize the literature while minimizing conjecture, but also to point out gaps in the literature and potential future research opportunities.
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Affiliation(s)
- Yuri Simone
- CIBIO Research Centre in Biodiversity and Genetic Resources, InBIO, Porto, Portugal
| | - Arie van der Meijden
- CIBIO Research Centre in Biodiversity and Genetic Resources, InBIO, Porto, Portugal
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2
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Meucin-49, a multifunctional scorpion venom peptide with bactericidal synergy with neurotoxins. Amino Acids 2018; 50:1025-1043. [DOI: 10.1007/s00726-018-2580-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Accepted: 04/27/2018] [Indexed: 10/16/2022]
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3
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Maatoug R, Jebali J, Guieu R, De Waard M, Kharrat R. BotAF, a new Buthus occitanus tunetanus scorpion toxin, produces potent analgesia in rodents. Toxicon 2018; 149:72-85. [PMID: 29337220 DOI: 10.1016/j.toxicon.2018.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/08/2018] [Accepted: 01/09/2018] [Indexed: 11/25/2022]
Abstract
This work reports the purification of new potent scorpion neuropeptide, named BotAF, by an activity-guided screening approach. BotAF is a 64-residue long-chain peptide that shares very high similarity with the original β-like scorpion toxin group, in which several peptides have been characterized to be anti-nociceptive in rodents. BotAF administration to rodents does not produce any toxicity or motor impairment, including at high doses. In all models investigated, BotAF turned out to be an efficient peptide in abolishing acute and inflammatory (both somatic and visceral) pain in rodents. It performs with high potency compared to standard analgesics tested in the same conditions. The anti-nociceptive activity of BotAF depends on the route of injection: it is inactive when tested by i.c.v. or i.v. routes but gains in potency when pre-injected locally (in the same compartment than the irritant itself) or by i.t. root 40 to 60 min before pain induction, respectively. BotAF is not an AINS-like compound as it fails to reduce inflammatory edema. Also, it does not activate the opioidergic system as its activity is not affected by naloxone. BotAF does also not bind onto RyR and has low activity towards DRG ion channels (particularly TTX sensitive Na+ channels) and does not bind onto rat brain synaptosome receptors. In somatic and visceral pain models, BotAF dose-dependently inhibited lumbar spinal cord c-fos/c-jun mRNA up regulation. Altogether, our data favor a spinal or peripheral anti-nociceptive mode of action of BotAF.
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Affiliation(s)
- Riadh Maatoug
- Université de Tunis El Manar, Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques, 13, Place Pasteur BP-74, Tunis, 1002, Tunisia
| | - Jed Jebali
- Université de Tunis El Manar, Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques, 13, Place Pasteur BP-74, Tunis, 1002, Tunisia
| | - Régis Guieu
- Biochimie, Hôpital de la Timone, 13005, Marseille, France
| | - Michel De Waard
- Inserm U1087, Institut du Thorax, groupe IIb, Université de Nantes, 8 quai moncousu, 44000, Nantes, France; Smartox Biotechnology, 570 rue de la chimie, bâtiment Nanobio, 38700, Saint Martin d'Hères, France
| | - Riadh Kharrat
- Université de Tunis El Manar, Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques, 13, Place Pasteur BP-74, Tunis, 1002, Tunisia.
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Emerich BL, De Lima ME, Martin-Eauclaire MF, Bougis PE. Comparative analyses and implications for antivenom serotherapy of four Moroccan scorpion Buthus occitanus venoms: Subspecies tunetanus, paris, malhommei, and mardochei. Toxicon 2017; 149:26-36. [PMID: 28712915 DOI: 10.1016/j.toxicon.2017.07.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 07/04/2017] [Accepted: 07/10/2017] [Indexed: 01/14/2023]
Abstract
Temporary passive immunity such as serotherapy against venoms requires the full knowledge of all venom's components. Here, four venoms from Moroccan common yellow scorpions belonging to Buthus occitanus, subspecies tunetanus, paris, malhommei, and mardochei, all collected in four different restricted areas, were analysed in deep. They were fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and their molecular masse profile determined by off-line MALDI-TOF mass spectrometry. Characterisation of their main components was achieved by enzyme-linked immunosorbent assay (ELISA) using specific antisera against the major lethal scorpion toxins identified so far, i.e. voltage-gated sodium channels (Nav) modulators α- and β-toxins, as well as diverse potassium channel pore blocker toxins. For fractions with identical RP-HPLC retention times, we observe that their relative quantities show large differences. Moreover, identical masses present simultaneously in the four venoms are infrequent. ELISAs show that the majority of the RP-HPLC compounds cross-react with the antiserum against the "α-like" toxin Bot I, which has been previously identified in the Algerian Buthus occitanus tunetanus venom. Moreover, minor fractions were recognised by the antiserum against the highly lethal "classical" α-toxin of reference AaH II from the Androctonus australis venom. As such, our results bring new sights for further improving scorpion venom serotherapy in Morocco.
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Affiliation(s)
- Bruna Luiza Emerich
- Aix Marseille Université, CNRS, CRN2M UMR7286, 13344, Marseille, France; Laboratório de Venenos e Toxinas Animais, Dept de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo-Horizonte, MG, Brazil
| | - Maria Elena De Lima
- Laboratório de Venenos e Toxinas Animais, Dept de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, Belo-Horizonte, MG, Brazil
| | | | - Pierre E Bougis
- Aix Marseille Université, CNRS, CRN2M UMR7286, 13344, Marseille, France.
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5
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Wu W, Li Z, Ma Y. Adaptive evolution of insect selective excitatory β-type sodium channel neurotoxins from scorpion venom. Peptides 2017; 92:31-37. [PMID: 28363794 DOI: 10.1016/j.peptides.2017.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/25/2017] [Accepted: 03/27/2017] [Indexed: 10/19/2022]
Abstract
Insect selective excitatory β-type sodium channel neurotoxins from scorpion venom (β-NaScTxs) are composed of about 70-76 amino acid residues and share a common scaffold stabilized by four unique disulfide bonds. The phylogenetic analysis of these toxins was hindered by limited sequence data. In our recent study, two new insect selective excitatory β-NaScTxs, LmIT and ImIT, were isolated from Lychas mucronatus and Isometrus maculatus, respectively. With the sequences previously reported, we examined the adaptive molecular evolution of insect selective excitatory β-NaScTxs by estimating the nonsynonymous-to-synonymous rate ratio (ω=dN/dS). The results revealed 12 positively selected sites in the genes of insect selective excitatory β-NaScTxs. Moreover, these positively selected sites match well with the sites important for interacting with sodium channels, as demonstrated in previous mutagenesis study. These results reveal that adaptive evolution after gene duplication is one of the most important genetic mechanisms of scorpion neurotoxin diversification.
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Affiliation(s)
- Wenlan Wu
- Medical School, Henan University of Science and Technology, Luoyang, Henan Province, PR China.
| | - Zhongjie Li
- Medical School, Henan University of Science and Technology, Luoyang, Henan Province, PR China
| | - Yibao Ma
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
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6
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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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7
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Martin-Eauclaire MF, Salvatierra J, Bosmans F, Bougis PE. The scorpion toxin Bot IX is a potent member of the α-like family and has a unique N-terminal sequence extension. FEBS Lett 2016; 590:3221-32. [DOI: 10.1002/1873-3468.12357] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 08/05/2016] [Accepted: 08/05/2016] [Indexed: 11/08/2022]
Affiliation(s)
| | - Juan Salvatierra
- Department of Physiology; School of Medicine; Johns Hopkins University; Baltimore MD USA
| | - Frank Bosmans
- Department of Physiology; School of Medicine; Johns Hopkins University; Baltimore MD USA
- Solomon H. Snyder Department of Neuroscience; School of Medicine; Johns Hopkins University; Baltimore MD USA
| | - Pierre E. Bougis
- Aix Marseille Université; CNRS; CRN2M; UMR7286; PFRN-CAPM; Marseille France
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β/δ-PrIT1, a highly insecticidal toxin from the venom of the Brazilian spider Phoneutria reidyi (F.O. Pickard-Cambridge, 1897). Toxicon 2015. [DOI: 10.1016/j.toxicon.2015.07.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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9
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Isolation and Characterization of a Novel Non-Selective β-Toxin from the Venom of the ScorpionIsometrus maculatus. Biosci Biotechnol Biochem 2014; 76:2089-92. [DOI: 10.1271/bbb.120438] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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10
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Liu ZR, Tao J, Dong BQ, Ding G, Cheng ZJ, He HQ, Ji YH. Pharmacological kinetics of BmK AS, a sodium channel site 4-specific modulator on Nav1.3. Neurosci Bull 2014; 28:209-21. [PMID: 22622820 DOI: 10.1007/s12264-012-1234-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
OBJECTIVE In this study, the pharmacological kinetics of Buthus martensi Karsch (BmK) AS, a specific modulator of voltage-gated sodium channel site 4, was investigated on Na(v)1.3 expressed in Xenopus oocytes. METHODS Two-electrode voltage clamp was used to record the whole-cell sodium current. RESULTS The peak currents of Na(v)1.3 were depressed by BmK AS over a wide range of concentrations (10, 100, and 500 nmol/L). Most remarkably, BmK AS at 100 nmol/L hyperpolarized the voltage-dependence and increased the voltage-sensitivity of steady-state activation/inactivation. In addition, BmK AS was capable of hyperpolarizing not only the fast inactivation but also the slow inactivation, with a greater preference for the latter. Moreover, BmK AS accelerated the time constant and increased the ratio of recovery in Na(v)1.3 at all concentrations. CONCLUSION This study provides direct evidence that BmK AS facilitates steady-state activation and inhibits slow inactivation by stabilizing both the closed and open states of the Na(v)1.3 channel, which might result from an integrative binding to two receptor sites on the voltage-gated sodium channels. These results may shed light on therapeutics against Na(v)1.3-targeted pathology.
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Affiliation(s)
- Zhi-Rui Liu
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai 200444, China
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11
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Liu ZR, Zhang H, Wu JQ, Zhou JJ, Ji YH. PKA phosphorylation reshapes the pharmacological kinetics of BmK AS, a unique site-4 sodium channel-specific modulator. Sci Rep 2014; 4:3721. [PMID: 24430351 PMCID: PMC5379197 DOI: 10.1038/srep03721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 12/19/2013] [Indexed: 01/14/2023] Open
Abstract
Although modulation of the activity of voltage-gated sodium channels (VGSCs) by protein kinase A (PKA) phosphorylation has been investigated in multiple preparations, the pharmacological sensitivity of VGSCs to scorpion toxins after PKA phosphorylation has rarely been approached. In this study, the effects of BmK AS, a sodium channel-specific modulator from Chinese scorpion Buthus martensi Karsch, on the voltage-dependent activation and inactivation of Nav1.2 were examined before and after PKA activation. After PKA phosphorylation, the pattern of dose-dependent modulation of BmK AS, on both Nav1.2α and Nav1.2 (α + β1) was reshaped. Meanwhile, the shifts in voltage-dependency of activation and inactivation induced by BmK AS were attenuated. The results suggested that PKA might play a role in different patterns how β-like toxins such as BmK AS modulate gating properties and peak currents of VGSCs.
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Affiliation(s)
- Z R Liu
- 1] Department of Pharmacology, Institute of Medical Science, Shanghai Jiao Tong University School of Medicine, South Chongqing Road 280, Shanghai 200025, P.R.China [2] Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Nanchen Road 333, Shanghai 200436, P.R. China
| | - H Zhang
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Nanchen Road 333, Shanghai 200436, P.R. China
| | - J Q Wu
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Nanchen Road 333, Shanghai 200436, P.R. China
| | - J J Zhou
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Nanchen Road 333, Shanghai 200436, P.R. China
| | - Y H Ji
- 1] Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Nanchen Road 333, Shanghai 200436, P.R. China [2] Shanghai Chongmin Xinhua Translational Institute of Cancer Pain, Nanmen Road 25, Shanghai 202151, P.R. China
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12
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Martin-Eauclaire MF, Bosmans F, Céard B, Diochot S, Bougis PE. A first exploration of the venom of the Buthus occitanus scorpion found in southern France. Toxicon 2014; 79:55-63. [PMID: 24418174 DOI: 10.1016/j.toxicon.2014.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/20/2013] [Accepted: 01/01/2014] [Indexed: 11/28/2022]
Abstract
Even though Buthus occitanus scorpions are found throughout the Mediterranean region, a lack of distinctive characteristics has hampered their classification into different subspecies. Yet, stings from this particular scorpion family are reported each year to result in pain followed by various toxic symptoms. In order to determine the toxicity origin of the rare French B. occitanus Amoreux scorpion, we collected several specimens and studied their venom composition using a nano ultra high performance liquid chromatography and matrix assisted laser desorption/ionisation time-of-flight mass spectrometry (nano UHPLC/MALDI-TOF-MS) automated workflow combined with an enzyme-linked immunosorbent assay (ELISA) approach. Moreover, we compared this dataset to that obtained from highly lethal Androctonus australis and Androctonus mauretanicus scorpions collected in North Africa. As a result, we found that the B. occitanus Amoreux venom is toxic to mice, an observation that is most likely caused by venom components that inhibit voltage-gated sodium channel inactivation. Moreover, we identified similarities in venom composition between B. occitanus scorpions living in the South of France and other Buthidae collected in Morocco and Algeria. As such, the results of this study should be taken into consideration when treating stings from the B. occitanus species living in the South of France.
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Affiliation(s)
- Marie-France Martin-Eauclaire
- Aix Marseille Université, CNRS, CRN2M UMR7286, Faculté de Médecine, Campus Nord, CS80011, Bd Pierre Dramard, F-13344 Marseille Cedex 15, 13015 Marseille, France
| | - Frank Bosmans
- Department of Physiology, Johns Hopkins University-School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University-School of Medicine, Baltimore, MD 21205, USA
| | - Brigitte Céard
- Aix Marseille Université, CNRS, CRN2M UMR7286, Faculté de Médecine, Campus Nord, CS80011, Bd Pierre Dramard, F-13344 Marseille Cedex 15, 13015 Marseille, France
| | - Sylvie Diochot
- CNRS, IPMC UMR 6097, 06560, Sophia-Antipolis, Valbonne, France
| | - Pierre E Bougis
- Aix Marseille Université, CNRS, CRN2M UMR7286, Faculté de Médecine, Campus Nord, CS80011, Bd Pierre Dramard, F-13344 Marseille Cedex 15, 13015 Marseille, France.
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13
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Quintero-Hernández V, Jiménez-Vargas J, Gurrola G, Valdivia H, Possani L. Scorpion venom components that affect ion-channels function. Toxicon 2013; 76:328-42. [PMID: 23891887 PMCID: PMC4089097 DOI: 10.1016/j.toxicon.2013.07.012] [Citation(s) in RCA: 193] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 07/16/2013] [Indexed: 12/31/2022]
Abstract
The number and types of venom components that affect ion-channel function are reviewed. These are the most important venom components responsible for human intoxication, deserving medical attention, often requiring the use of specific anti-venoms. Special emphasis is given to peptides that recognize Na(+)-, K(+)- and Ca(++)-channels of excitable cells. Knowledge generated by direct isolation of peptides from venom and components deduced from cloned genes, whose amino acid sequences are deposited into databanks are nowadays in the order of 1.5 thousands, out of an estimate biodiversity closed to 300,000. Here the diversity of components is briefly reviewed with mention to specific references. Structural characteristic are discussed with examples taken from published work. The principal mechanisms of action of the three different types of peptides are also reviewed. Na(+)-channel specific venom components usually are modifier of the open and closing kinetic mechanisms of the ion-channels, whereas peptides affecting K(+)-channels are normally pore blocking agents. The Ryanodine Ca(++)-channel specific peptides are known for causing sub-conducting stages of the channels conductance and some were shown to be able to internalize penetrating inside the muscle cells.
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Affiliation(s)
- V. Quintero-Hernández
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
| | - J.M. Jiménez-Vargas
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
| | - G.B. Gurrola
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
- Cardiovascular Center 2139, Michigan University, Ann Arbor, MI 48109-5644, U.S.A
| | - H.H.F. Valdivia
- Cardiovascular Center 2139, Michigan University, Ann Arbor, MI 48109-5644, U.S.A
| | - L.D. Possani
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
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14
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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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15
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Nie Y, Zeng XC, Luo X, Wu S, Zhang L, Cao H, Zhou J, Zhou L. Tremendous intron length differences of the BmKBT and a novel BmKBT-like peptide genes provide a mechanical basis for the rapid or constitutive expression of the peptides. Peptides 2012; 37:150-6. [PMID: 22705625 DOI: 10.1016/j.peptides.2012.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 06/07/2012] [Accepted: 06/07/2012] [Indexed: 11/17/2022]
Abstract
The cDNA sequence encoding a novel BmKBT-like peptide (referred to as BmKBy) was cloned and sequenced from the scorpion Mesobuthus martensii Karsch. Functional analysis indicated that both BmKBT and BmKBy possess strong toxicity in mice, but very weak toxicity in cotton bollworm. Phylogenetic analysis showed that BmKBy and BmKBT represent evolutionary intermediates between the α- and β-toxins from scorpions. The genomic sequences of BmKBT and BmKBy were also obtained. It is interesting to see that two genes, which contain an intron of 225 and 1529bp, respectively, exactly code for the BmKBT peptide. One gene, which contains an intron of 1312bp, codes for BmKBy. Given that genes with long introns favor constitutive expression, whereas those with short introns are rapidly regulated in response to stimulations, the BmKBT_a and BmKBT_b genes provide a mechanical basis for either constitutive expression or rapid generation of the toxic peptides in response to different signals.
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Affiliation(s)
- Yao Nie
- Department of Biological Science and Technology, School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), Wuhan 430074, China
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16
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Gurevitz M. Mapping of scorpion toxin receptor sites at voltage-gated sodium channels. Toxicon 2012; 60:502-11. [DOI: 10.1016/j.toxicon.2012.03.022] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 03/22/2012] [Accepted: 03/27/2012] [Indexed: 10/28/2022]
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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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Schwartz EF, Mourão CBF, Moreira KG, Camargos TS, Mortari MR. Arthropod venoms: A vast arsenal of insecticidal neuropeptides. Biopolymers 2012. [DOI: 10.1002/bip.22100] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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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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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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Canul-Tec JC, Riaño-Umbarila L, Rudiño-Piñera E, Becerril B, Possani LD, Torres-Larios A. Structural basis of neutralization of the major toxic component from the scorpion Centruroides noxius Hoffmann by a human-derived single-chain antibody fragment. J Biol Chem 2011; 286:20892-900. [PMID: 21489992 PMCID: PMC3121463 DOI: 10.1074/jbc.m111.238410] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 03/30/2011] [Indexed: 11/06/2022] Open
Abstract
It has previously been reported that several single-chain antibody fragments of human origin (scFv) neutralize the effects of two different scorpion venoms through interactions with the primary toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2). Here we present the crystal structure of the complex formed between one scFv (9004G) and the Cn2 toxin, determined in two crystal forms at 2.5 and 1.9 Å resolution. A 15-residue span of the toxin is recognized by the antibody through a cleft formed by residues from five of the complementarity-determining regions of the scFv. Analysis of the interface of the complex reveals three features. First, the epitope of toxin Cn2 overlaps with essential residues for the binding of β-toxins to its Na(+) channel receptor site. Second, the putative recognition of Css2 involves mainly residues that are present in both Cn2 and Css2 toxins. Finally, the effect on the increase of affinity of previously reported key residues during the maturation process of different scFvs can be inferred from the structure. Taken together, these results provide the structural basis that explain the mechanism of the 9004G neutralizing activity and give insight into the process of directed evolution that gave rise to this family of neutralizing scFvs.
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Affiliation(s)
- Juan Carlos Canul-Tec
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Lidia Riaño-Umbarila
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Enrique Rudiño-Piñera
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Baltazar Becerril
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Lourival D. Possani
- From the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca, Morelos 62210 and
| | - Alfredo Torres-Larios
- the Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Apartado postal 70-243, Mexico City 04510, México
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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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Abdel-Rahman MA, Omran MAA, Abdel-Nabi IM, Nassier OA, Schemerhorn BJ. Neurotoxic and cytotoxic effects of venom from different populations of the Egyptian Scorpio maurus palmatus. Toxicon 2009; 55:298-306. [PMID: 19682484 DOI: 10.1016/j.toxicon.2009.08.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 07/31/2009] [Accepted: 08/05/2009] [Indexed: 10/20/2022]
Abstract
Neurotoxic and cytotoxic effects of venoms from Scorpio maurus palmatus taken from different populations were assessed for geographic based variability in toxicity, and to evaluate their insecticidal potency. Scorpions were collected from four regions. Three locations were mutually isolated pockets in the arid area of Southern Sinai. The fourth sample was collected from a population inhabiting the semi-arid environment of Western Mediterranean Coastal Desert. The neurotoxic (paralytic) effect of the venom from each population was assayed by its ability to induce permanent disability in adult cockroaches within 3h. Venom was applied using microinjection techniques through an intersegmental membrane. Probit analysis was used to calculate the Paralytic Effective Dose (PED(50), ng/100mg). Levels of glutathione, lipid peroxidation, protein carbonyl content and nitric oxide, as well as the activities of superoxide dismutase, catalase and cholinesterase, were measured to assess the cytotoxicity of the venom. The results show that the injected venom from each population induced obvious spasticity, followed by flaccid paralysis. All the tested biochemical parameters, except glutathione content, revealed significant differences in toxicity in venom taken from the different scorpion populations. We conclude that (i) the venom of this scorpion has significant neurotoxic and cytotoxic effects on insect cells, (ii) its efficacy, as assessed by the PED(50) unit, exhibited variation across its geographic range, and (iii) components in the venom may have the potential for being developed into effective and environmentally friendly bioinsecticides.
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Affiliation(s)
- Mohamed A Abdel-Rahman
- Department of Zoology, Faculty of Science, Suez Canal University, Ismailia 41522, Egypt.
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New analysis of the toxic compounds from the Androctonus mauretanicus mauretanicus scorpion venom. Toxicon 2008; 51:835-52. [DOI: 10.1016/j.toxicon.2007.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 12/10/2007] [Accepted: 12/14/2007] [Indexed: 11/23/2022]
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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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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: 104] [Impact Index Per Article: 6.1] [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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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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Bosmans F, Martin-Eauclaire MF, Tytgat J. Differential effects of five 'classical' scorpion beta-toxins on rNav1.2a and DmNav1 provide clues on species-selectivity. Toxicol Appl Pharmacol 2006; 218:45-51. [PMID: 17118417 PMCID: PMC1868420 DOI: 10.1016/j.taap.2006.10.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 10/05/2006] [Accepted: 10/11/2006] [Indexed: 12/19/2022]
Abstract
In general, scorpion beta-toxins have been well examined. However, few in-depth studies have been devoted to species selectivity and affinity comparisons on the different voltage-activated Na(+) channels since they have become available as cloned channels that can be studied in heterologous expression systems. As a result, their classification is largely historical and dates from early in vivo experiments on mice and cockroach and fly larvae. In this study, we aimed to provide an updated overview of selectivity and affinity of scorpion beta-toxins towards voltage-activated Na(+) channels of vertebrates or invertebrates. As pharmacological tools, we used the classic beta-toxins AaHIT, Css II, Css IV, Css VI and Ts VII and tested them on the neuronal vertebrate voltage-activated Na(+) channel, rNa(v)1.2a. For comparison, its invertebrate counterpart, DmNav1, was also tested. Both these channels were expressed in Xenopus laevis oocytes and the currents measured with the two-electrode voltage-clamp technique. We supplemented this data with several binding displacement studies on rat brain synaptosomes. The results lead us to propose a general classification and a novel nomenclature of scorpion beta-toxins based on pharmacological activity.
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Affiliation(s)
- Frank Bosmans
- Laboratory of Toxicology, University of Leuven, O&N 2, Postbus 922, Herestraat 49, 3000 Leuven, Belgium
- * To whom correspondence should be addressed: J. Tytgat, Laboratory of Toxicology, University of Leuven, O&N 2, Postbus 922, Herestraat 49, 3000 Leuven, Belgium. Fax: +3216323405, Tel.: +3216323403. E-mail: ; http://www.toxicology.be
| | - Marie-France Martin-Eauclaire
- CNRS FRE 2732, Biologie des Interactions Moléculaires et Cellulaires, Faculté de Médecine secteur Nord, Institut Jean Roche, Université de la Méditerranée, Bd Pierre Dramard, 13916, Marseille, Cedex 20, France
| | - Jan Tytgat
- Laboratory of Toxicology, University of Leuven, O&N 2, Postbus 922, Herestraat 49, 3000 Leuven, Belgium
- * To whom correspondence should be addressed: J. Tytgat, Laboratory of Toxicology, University of Leuven, O&N 2, Postbus 922, Herestraat 49, 3000 Leuven, Belgium. Fax: +3216323405, Tel.: +3216323403. E-mail: ; http://www.toxicology.be
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Cohen L, Lipstein N, Gordon D. Allosteric interactions between scorpion toxin receptor sites on voltage‐gated Na channels imply a novel role for weakly active components in arthropod venom. FASEB J 2006; 20:1933-5. [PMID: 16877526 DOI: 10.1096/fj.05-5545fje] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Scorpion beta and alpha-toxins modify the activation and inactivation of voltage-gated sodium channels. Although the two types of toxin bind at two distinct receptor sites on the same sodium channel, they exhibit synergic effects when coinjected into insects. To clarify the basis of this synergism we examined the mutual effects of alpha and beta toxin representatives in radio-ligand binding assays. We found positive allosteric interactions between receptor site-4 of the excitatory Bj-xtrIT and the depressant LqhIT2 beta toxins and receptor site-3 of the alpha toxin LqhalphaIT, on locust neuronal membranes. Unexpectedly, a nontoxic mutant Bj-xtrIT-E15R, which binds with high affinity to receptor site-4, was able to enhance LqhalphaIT binding and toxicity similarly to the unmodified Bj-xtrIT. This result indicates that mere binding of a nontoxic ligand to receptor site-4 ("silent binding") induces a conformational change that does not alter channel gating, but influences toxin binding at receptor site-3 leading to enhanced toxicity. This finding suggests a new functional role for weakly toxic polypeptides in that they enhance the effect of other active neurotoxins in the arthropod venom. Such silent binding may have also valuable implications in attempts to improve drug efficacy by combining potent drugs with nonactive allosteric enhancers.
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Affiliation(s)
- Lior Cohen
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel
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30
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Zuo XP, He HQ, He M, Liu ZR, Xu Q, Ye JG, Ji YH. Comparative pharmacology and cloning of two novel arachnid sodium channels: Exploring the adaptive insensitivity of scorpion to its toxins. FEBS Lett 2006; 580:4508-14. [PMID: 16870180 DOI: 10.1016/j.febslet.2006.07.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 07/07/2006] [Accepted: 07/07/2006] [Indexed: 11/24/2022]
Abstract
Scorpion toxins have been found lacking effect on Na(+) current of its own sodium channel, whereas the molecular mechanism remains mystery. In this study, the binding affinity of pharmacologically distinct scorpion toxins was found much weaker to scorpion (Buthus martensii) nerve synaptosomes than to spider (Ornithoctonus huwena) ones. The sodium channel cDNA from these two species were further cloned. The deduced proteins contain 1871 and 1987 amino acids respectively. Several key amino acid substitutions, i.e., A1610V, I1611L and S1617K, are found in IVS3-S4 constituting receptor site-3, and for receptor site-4, two residues (Leu-Pro) are inserted near IIS4 of scorpion sodium channel.
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Affiliation(s)
- Xiao-Pan Zuo
- Graduate School of the Chinese Academy of Sciences, Shanghai Institute of Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, PR China
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Cohen L, Gilles N, Karbat I, Ilan N, Gordon D, Gurevitz M. Direct evidence that receptor site-4 of sodium channel gating modifiers is not dipped in the phospholipid bilayer of neuronal membranes. J Biol Chem 2006; 281:20673-20679. [PMID: 16720570 DOI: 10.1074/jbc.m603212200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a recent note to Nature, R. MacKinnon has raised the possibility that potassium channel gating modifiers are able to partition in the phospholipid bilayer of neuronal membranes and that by increasing their partial concentration adjacent to their receptor, they affect channel function with apparent high affinity (Lee and MacKinnon (2004) Nature 430, 232-235). This suggestion was adopted by Smith et al. (Smith, J. J., Alphy, S., Seibert, A. L., and Blumenthal, K. M. (2005) J. Biol. Chem. 280, 11127-11133), who analyzed the partitioning of sodium channel modifiers in liposomes. They found that certain modifiers were able to partition in these artificial membranes, and on this basis, they have extrapolated that scorpion beta-toxins interact with their channel receptor in a similar mechanism as that proposed by MacKinnon. Since this hypothesis has actually raised a new conception, we examined it in binding assays using a number of pharmacologically distinct scorpion beta-toxins and insect and mammalian neuronal membrane preparations, as well as by analyzing the rate by which the toxin effect on gating of Drosophila DmNa(v)1 and rat brain rNa(v)1.2a develops. We show that in general, scorpion beta-toxins do not partition in neuronal membranes and that in the case in which a depressant beta-toxin partitions in insect neuronal membranes, this partitioning is unrelated to its interaction with the receptor site and the effect on the gating properties of the sodium channel. These results negate the hypothesis that the high affinity of beta-toxins for sodium channels is gained by their ability to partition in the phospholipid bilayer and clearly indicate that the receptor site for scorpion beta-toxins is accessible to the extracellular solvent.
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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
| | - Nicolas Gilles
- Commissariat à l'Energie Atomique, Department d'Ingenierie et d'Etudes des Proteines, C.E. Saclay, F-91191 Gif Sur Yvette Cedex, France
| | - Izhar Karbat
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
| | - Nitza Ilan
- 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.
| | - 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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32
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Nascimento DG, Rates B, Santos DM, Verano-Braga T, Barbosa-Silva A, Dutra AAA, Biondi I, Martin-Eauclaire MF, De Lima ME, Pimenta AMC. Moving pieces in a taxonomic puzzle: Venom 2D-LC/MS and data clustering analyses to infer phylogenetic relationships in some scorpions from the Buthidae family (Scorpiones). Toxicon 2006; 47:628-39. [PMID: 16551474 DOI: 10.1016/j.toxicon.2006.01.015] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The Buthidae is the most clinically important scorpion family, with over 500 species distributed worldwide. Taxonomical positions and phylogenetic relationships concerning the representative genera and species of this family have been mostly inferred based upon comparisons between morphological characters. Yet, some authors have performed such inferences by comparing some structural properties of a few selected molecules found in the venoms from these scorpions. Here, we propose a novel methodology pipeline designed to address these issues. We have analyzed the whole venoms from some species that exemplify peculiar cases in the Buthidae family (Tityus stigmurus, Tityus serrulatus, Tityus bahiensis, Leiurus quinquestriatus quinquestriatus and Leiurus quinquestriatus hebraeus), by means of a proteomic approach using a 2D-LC/MS technique. The molecules found in these venoms were clustered according to their physicochemical properties (molecular mass and hydrophobicity), by using the machine learning-based Weka software. The clusters assessment, along with the number of molecules found in a given cluster for each scorpion, which assigns for the venom and structural family complexities, respectively, was used to generate a phenetic correlation tree for positioning these species. Our results were in accordance with the classical taxonomy viewpoint, which places T. serrulatus and T. stigmurus as very close species, T. bahiensis as a less related species in the Tityus genus and L. q. quinquestriatus and L. q. hebraeus with small differences within the same species (L. quinquestriatus). Therefore, we believe that this is a well-suited method to determine venom complexities that reflect the scorpions' evolutionary history, which can be crucial to reconstruct their phylogeny through the molecular evolution of their venoms.
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Affiliation(s)
- Danielle G Nascimento
- Laboratório de Venenos e Toxinas Animais, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627, 31270-901 Belo Horizonte, Minas Gerais, Brazil
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33
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Bel Haj Rhouma R, Cérutti-Duonor M, Benkhadir K, Goudey-Perrière F, El Ayeb M, Lopez-Ferber M, Karoui H. Insecticidal effects of Buthus occitanus tunetanus BotIT6 toxin expressed in Escherichia coli and baculovirus/insect cells. JOURNAL OF INSECT PHYSIOLOGY 2005; 51:1376-83. [PMID: 16216259 DOI: 10.1016/j.jinsphys.2005.08.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 08/24/2005] [Accepted: 08/26/2005] [Indexed: 05/04/2023]
Abstract
BotIT6 is a neurotoxin polypeptide derived from the venom of the scorpion Buthus occitanus tunetanus (Bot). Its mature form is composed of 62 amino acids. BotIT6 has been reported to be the most potent toxin from Bot venom that has a strict selectivity for insects. Such toxin may have potential as a potent animal-harmless tool against insects. Using RT-PCR, we isolated and sequenced a cDNA encoding 62 amino acid residues corresponding to the known amino acid sequence of BotIT6. We have expressed a recombinant active form of BotIT6 in significantly high amounts in Escherichia coli. We have also engineered the cDNA into the Autographa californica Nuclear Polyhedrosis Virus (AcMNPV) genome and expressed the protein under control of the polyhedrin promoter. Supernatants of AcIT6-virus infected Sf9 insect cells exhibit a typical intoxication effect when injected to Spodoptera littoralis larvae. Moreover, injection of the recombinant virus showed enhanced insecticidal potency against S. littoralis larvae compared with wild type AcMNPV.
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Affiliation(s)
- Rahima Bel Haj Rhouma
- Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, Tunis-Belvedère, Tunisia
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34
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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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Martin-Eauclaire MF, Ceard B, Bosmans F, Rosso JP, Tytgat J, Bougis PE. New “Birtoxin analogs” from Androctonus australis venom. Biochem Biophys Res Commun 2005; 333:524-30. [PMID: 15963953 DOI: 10.1016/j.bbrc.2005.05.148] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Accepted: 05/23/2005] [Indexed: 11/16/2022]
Abstract
From the venom of the scorpion Androctonus australis, we have isolated a new bioactive polypeptide termed AaBTX-L1. When tested on the insect voltage-gated Na(+) channel (para) of the fruit fly, this toxin was able to induce a clear shift in activation (V(1/2)), resulting in the opening of the channel at more negative membrane potentials. Furthermore, AaBTX-L1 was totally devoid of toxicity when injected into mice intracerebroventricularly and did not compete with radiolabeled voltage-gated K(+) and Na(+) channel toxins in binding experiments on rat brain synaptosomes. Using its N-terminal amino acid sequence to design degenerate primers, several clones were amplified by PCR from the A. australis venom gland cDNA library. As a consequence, seven full oligonucleotide sequences encoding "long-chain" polypeptides with only three disulfide bridges have been cloned for the first time and are described here. Remarkably, they share high similarity with the anti-insect toxin Birtoxin from Parabuthus transvaalicus.
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Affiliation(s)
- Marie-France Martin-Eauclaire
- CNRS FRE 2738, Ingénierie des Protéines, Faculté de Médecine secteur Nord, Institut Jean Roche, Université de la Méditerranée, Bd Pierre Dramard, 13916 Marseille 20, France.
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Bosmans F, Martin-Eauclaire MF, Tytgat J. The depressant scorpion neurotoxin LqqIT2 selectively modulates the insect voltage-gated sodium channel. Toxicon 2005; 45:501-7. [PMID: 15733572 DOI: 10.1016/j.toxicon.2004.12.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 12/09/2004] [Accepted: 12/10/2004] [Indexed: 11/30/2022]
Abstract
LqqIT2 is a depressant neurotoxin present in the venom of the Leiurus quinquestriatus quinquestriatus scorpion, one of the world's most dangerous scorpions endemic to dry habitats in Africa and Asia. In order to determine its efficacy, potency and selectivity, LqqIT2 was subjected for the first time to an electrophysiological and pharmacological comparison between two different cloned sodium channels expressed in Xenopus laevis oocytes. Aside from typical beta-toxin effects, LqqIT2 also affected the inactivation process and ion selectivity of the insect voltage-gated sodium channel. The most interesting feature of LqqIT2 is its total insect-selectivity. At a concentration of 1 microM, the insect-voltage-gated sodium channel, para, was profoundly modulated while its mammalian counterpart, the rat brain Na(v)1.2 channel, was not affected. This trait offers excellent prospects for the development of novel insecticides.
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Affiliation(s)
- Frank Bosmans
- Laboratory of Toxicology, Faculty of Pharmacy, University of Leuven, E. Van Evenstraat 4, B-3000 Leuven, Belgium
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37
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Cohen L, Karbat I, Gilles N, Ilan N, Benveniste M, Gordon D, Gurevitz M. Common features in the functional surface of scorpion beta-toxins and elements that confer specificity for insect and mammalian voltage-gated sodium channels. J Biol Chem 2004; 280:5045-53. [PMID: 15569679 DOI: 10.1074/jbc.m408427200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scorpion beta-toxins that affect the activation of mammalian voltage-gated sodium channels (Navs) have been studied extensively, but little is known about their functional surface and mode of interaction with the channel receptor. To enable a molecular approach to this question, we have established a successful expression system for the anti-mammalian scorpion beta-toxin, Css4, whose effects on rat brain Navs have been well characterized. A recombinant toxin, His-Css4, was obtained when fused to a His tag and a thrombin cleavage site and had similar binding affinity for and effect on Na currents of rat brain sodium channels as those of the native toxin isolated from the scorpion venom. Molecular dissection of His-Css4 elucidated a functional surface of 1245 A2 composed of the following: 1) a cluster of residues associated with the alpha-helix, which includes a putative "hot spot" (this cluster is conserved among scorpion beta-toxins and contains their "pharmacophore"); 2) a hydrophobic cluster associated mainly with the beta2 and beta3 strands, which is likely to confer the specificity for mammalian Navs; 3) a single bioactive residue (Trp-58) in the C-tail; and 4) a negatively charged residue (Glu-15) involved in voltage sensor trapping as inferred from our ability to uncouple toxin binding from activity upon its substitution. This study expands our understanding about the mode of action of scorpion beta-toxins and illuminates differences in the functional surfaces that may dictate their specificities for mammalian versus insect sodium channels.
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Affiliation(s)
- Lior Cohen
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Sackler School of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
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Karbat I, Cohen L, Gilles N, Gordon D, Gurevitz M, Izhar K, Lior C, Nicholas G, Dalia G, Michael G. Conversion of a scorpion toxin agonist into an antagonist highlights an acidic residue involved in voltage sensor trapping during activation of neuronal Na
+
channels. FASEB J 2004; 18:683-9. [PMID: 15054090 DOI: 10.1096/fj.03-0733com] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Gating modifiers constitute a large group of polypeptide toxins that interact with the voltage-sensing module of ion channels. Among them, scorpion beta-toxins induce a negative shift in the voltage dependence of sodium channel activation. To explain their effect, a "voltage sensor trapping" model has been proposed in which the voltage sensor of domain-II (DIIS4) is trapped in an outward, activated position by a prebound beta-toxin upon membrane depolarization. Whereas toxin effect on channel activation was enhanced upon neutralization of the two outermost arginines in DIIS4, toxin residues involved in sensor trapping have not been identified. Using the scorpion excitatory beta-toxin, Bj-xtrIT, we found two conserved acidic residues, Glu15 and Glu30, mandatory for toxin action. Whereas mutagenesis of Glu30 affected both toxicity and binding affinity, substitutions E15A/F abolished activity but had minor effects on binding. Complete uncoupling of activity from binding was obtained with mutant E15R, acting as an efficient antagonist of Bj-xtrIT. On the basis of the voltage sensor trapping model and our results, we propose that Glu15 interacts with the emerging gating charges of DIIS4 upon membrane depolarization. Conserved acidic residues found in a variety of gating modifiers from scorpions and spiders may interact similarly with the voltage sensor.
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Affiliation(s)
- Izhar Karbat
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
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Cohen L, Karbat I, Gilles N, Froy O, Corzo G, Angelovici R, Gordon D, Gurevitz M. Dissection of the Functional Surface of an Anti-insect Excitatory Toxin Illuminates a Putative “Hot Spot” Common to All Scorpion β-Toxins Affecting Na+ Channels. J Biol Chem 2004; 279:8206-11. [PMID: 14672947 DOI: 10.1074/jbc.m307531200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scorpion beta-toxins affect the activation of voltage-sensitive sodium channels (NaChs). Although these toxins have been instrumental in the study of channel gating and architecture, little is known about their active sites. By using an efficient system for the production of recombinant toxins, we analyzed by point mutagenesis the entire surface of the beta-toxin, Bj-xtrIT, an anti-insect selective excitatory toxin from the scorpion Buthotus judaicus. Each toxin mutant was purified and analyzed using toxicity and binding assays, as well as by circular dichroism spectroscopy to discern the differences among mutations that caused structural changes and those that specifically affected bioactivity. This analysis highlighted a functional discontinuous surface of 1405 A(2), which was composed of a number of non-polar and three charged amino acids clustered around the main alpha-helical motif and the C-tail. Among the charged residues, Glu(30) is a center of a putative "hot spot" in the toxin-receptor binding-interface and is shielded from bulk solvent by a hydrophobic "gasket" (Tyr(26) and Val(34)). Comparison of the Bj-xtrIT structure with that of other beta-toxins that are active on mammals suggests that the hot spot and an adjacent non-polar region are spatially conserved. These results highlight for the first time structural elements that constitute a putative "pharmacophore" involved in the interaction of beta-toxins with receptor site-4 on NaChs. Furthermore, the unique structure of the C-terminal region most likely determines the specificity of excitatory toxins for insect NaChs.
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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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Barbier J, Lamthanh H, Le Gall F, Favreau P, Benoit E, Chen H, Gilles N, Ilan N, Heinemann SH, Gordon D, Ménez A, Molgó J. A δ-Conotoxin from Conus ermineus Venom Inhibits Inactivation in Vertebrate Neuronal Na+ Channels but Not in Skeletal and Cardiac Muscles. J Biol Chem 2004; 279:4680-5. [PMID: 14615484 DOI: 10.1074/jbc.m309576200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have isolated delta-conotoxin EVIA (delta-EVIA), a conopeptide in Conus ermineus venom that contains 32 amino acid residues and a six-cysteine/four-loop framework similar to that of previously described omega-, delta-, microO-, and kappa-conotoxins. However, it displays low sequence homology with the latter conotoxins. delta-EVIA inhibits Na+ channel inactivation with unique tissue specificity upon binding to receptor site 6 of neuronal Na+ channels. Using amphibian myelinated axons and spinal neurons, we showed that delta-EVIA increases the duration of action potentials by inhibiting Na+ channel inactivation. delta-EVIA considerably enhanced nerve terminal excitability and synaptic efficacy at the frog neuromuscular junction but did not affect directly elicited muscle action potentials. The neuronally selective property of delta-EVIA was confirmed by showing that a fluorescent derivative of delta-EVIA labeled motor nerve endings but not skeletal muscle fibers. In a heterologous expression system, delta-EVIA inhibited inactivation of rat neuronal Na+ channel subtypes (rNaV1.2a, rNaV1.3, and rNaV1.6) but did not affect rat skeletal (rNaV1.4) and human cardiac muscle (hNaV1.5) Na+ channel subtypes. delta-EVIA, in the range of concentrations used, is the first conotoxin found to affect neuronal Na+ channels without acting on Na+ channels of skeletal and cardiac muscle. Therefore, it is a unique tool for discriminating voltage-sensitive Na+ channel subtypes and for studying the distribution and modulation mechanisms of neuronal Na+ channels, and it may serve as a lead to design new drugs adapted to treat diseases characterized by defective nerve conduction.
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Affiliation(s)
- Julien Barbier
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR 9040, CNRS, 91198 Gif-sur-Yvette cedex, France
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