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Mapping the interaction surface of scorpion β-toxins with an insect sodium channel. Biochem J 2021; 478:2843-2869. [PMID: 34195804 PMCID: PMC10081811 DOI: 10.1042/bcj20210336] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/21/2021] [Accepted: 06/24/2021] [Indexed: 02/07/2023]
Abstract
The interaction of insect-selective scorpion depressant β-toxins (LqhIT2 and Lqh-dprIT3 from Leiurus quinquestriatus hebraeus) with the Blattella germanica sodium channel, BgNav1-1a, was investigated using site-directed mutagenesis, electrophysiological analyses, and structural modeling. Focusing on the pharmacologically defined binding site-4 of scorpion β-toxins at the voltage-sensing domain II (VSD-II), we found that charge neutralization of D802 in VSD-II greatly enhanced the channel sensitivity to Lqh-dprIT3. This was consistent with the high sensitivity of the splice variant BgNav2-1, bearing G802, to Lqh-dprIT3, and low sensitivity of BgNav2-1 mutant, G802D, to the toxin. Further mutational and electrophysiological analyses revealed that the sensitivity of the WT = D802E < D802G < D802A < D802K channel mutants to Lqh-dprIT3 correlated with the depolarizing shifts of activation in toxin-free channels. However, the sensitivity of single mutants involving IIS4 basic residues (K4E = WT << R1E < R2E < R3E) or double mutants (D802K = K4E/D802K = R3E/D802K > R2E/D802K > R1E/D802K > WT) did not correlate with the activation shifts. Using the cryo-EM structure of the Periplaneta americana channel, NavPaS, as a template and the crystal structure of LqhIT2, we constructed structural models of LqhIT2 and Lqh-dprIT3-c in complex with BgNav1-1a. These models along with the mutational analysis suggest that depressant toxins approach the salt-bridge between R1 and D802 at VSD-II to form contacts with linkers IIS1-S2, IIS3-S4, IIIP5-P1 and IIIP2-S6. Elimination of this salt-bridge enables deeper penetration of the toxin into a VSD-II gorge to form new contacts with the channel, leading to increased channel sensitivity to Lqh-dprIT3.
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Li H, Xia Y. Recombinant production of the insecticidal scorpion toxin BjαIT in Escherichia coli. Protein Expr Purif 2017; 142:62-67. [PMID: 28988146 DOI: 10.1016/j.pep.2017.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 09/26/2017] [Accepted: 10/01/2017] [Indexed: 01/28/2023]
Abstract
Scorpion long-chain insect neurotoxins have important potential application value in agricultural pest control. The difficulty of obtaining natural toxins is the major obstacle preventing analyses of their insecticidal activity against more agricultural insect pests. Here we cloned the insect neurotoxin BjαIT gene into the pET32 expression vector and expressed the resulting thioredoxin (Trx)-BjαIT fusion protein in Escherichia coli. Soluble Trx-BjαIT was expressed at a high level when induced at 18 °C with 0.1 mM isopropyl β-d-1-thiogalactopyranoside, and it was purified by Ni2+-nitriloacetic acid affinity chromatography. After cleaving the Trx tag with recombinant enterokinase, the digestion products were purified by CM Sepharose FF ion-exchange chromatography, and 1.5 mg of purified recombinant BjαIT (rBjαIT) was obtained from 100 ml of induced bacterial cells. Injecting rBjαIT induced obvious neurotoxic symptoms and led to death in locust (Locusta migratoria) larvae. Dietary toxicity was not observed in locusts. The results demonstrate that active rBjαIT could be obtained efficiently from an E. coli expression system, which is helpful for determining its insecticidal activity against agricultural insect pests.
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Affiliation(s)
- Hongbo Li
- The Key Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province, College of Biological and Food Engineering, Huaihua University, Huaihua 418008, China; Genetic Engineering Research Center, College of Life Sciences, Chongqing University, Chongqing 400030, China
| | - Yuxian Xia
- Genetic Engineering Research Center, College of Life Sciences, Chongqing University, Chongqing 400030, China.
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Enhanced insecticidal activity of Chilo iridescent virus expressing an insect specific neurotoxin. J Invertebr Pathol 2016; 138:104-11. [DOI: 10.1016/j.jip.2016.06.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/23/2016] [Accepted: 06/27/2016] [Indexed: 11/19/2022]
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The unfulfilled promises of scorpion insectotoxins. J Venom Anim Toxins Incl Trop Dis 2015; 21:16. [PMID: 26085828 PMCID: PMC4470000 DOI: 10.1186/s40409-015-0019-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 05/18/2015] [Indexed: 01/09/2023] Open
Abstract
Since the description and biochemical characterization of the first insect-specific neurotoxins from scorpion venoms, almost all contributions have highlighted their potential application as leads for the development of potent bioinsecticides. Their practical use, however, has been hindered by different factors, some of which are intrinsically related to the toxins and other external determinants. Recent developments in the understanding of the action mechanisms of the scorpion insectotoxins and their bioactive surfaces, coupled with the exploration of novel bioinsecticide delivery systems have renewed the expectations that the scorpion insectotoxins could find their way into commercial applications in agriculture, as part of integrated pest control strategies. Herein, we review the current arsenal of available scorpion neurotoxins with a degree of specificity for insects, the progress made with alternative delivery methods, and the drawbacks that still preclude their practical use.
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Expression, delivery and function of insecticidal proteins expressed by recombinant baculoviruses. Viruses 2015; 7:422-55. [PMID: 25609310 PMCID: PMC4306846 DOI: 10.3390/v7010422] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/06/2015] [Accepted: 01/15/2015] [Indexed: 12/13/2022] Open
Abstract
Since the development of methods for inserting and expressing genes in baculoviruses, a line of research has focused on developing recombinant baculoviruses that express insecticidal peptides and proteins. These recombinant viruses have been engineered with the goal of improving their pesticidal potential by shortening the time required for infection to kill or incapacitate insect pests and reducing the quantity of crop damage as a consequence. A wide variety of neurotoxic peptides, proteins that regulate insect physiology, degradative enzymes, and other potentially insecticidal proteins have been evaluated for their capacity to reduce the survival time of baculovirus-infected lepidopteran host larvae. Researchers have investigated the factors involved in the efficient expression and delivery of baculovirus-encoded insecticidal peptides and proteins, with much effort dedicated to identifying ideal promoters for driving transcription and signal peptides that mediate secretion of the expressed target protein. Other factors, particularly translational efficiency of transcripts derived from recombinant insecticidal genes and post-translational folding and processing of insecticidal proteins, remain relatively unexplored. The discovery of RNA interference as a gene-specific regulation mechanism offers a new approach for improvement of baculovirus biopesticidal efficacy through genetic modification.
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Tianpei X, Li D, Qiu P, Luo J, Zhu Y, Li S. Scorpion peptide LqhIT2 activates phenylpropanoid pathways via jasmonate to increase rice resistance to rice leafrollers. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 230:1-11. [PMID: 25480003 DOI: 10.1016/j.plantsci.2014.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 10/07/2014] [Accepted: 10/09/2014] [Indexed: 05/09/2023]
Abstract
LqhIT2 is an insect-specific toxin peptide identified in Leiurus quinquestriatus hebraeus that can be toxic to lepidoptera pests. However, whether LqhIT2 induces insect resistance in rice, and how the LqhIT2 influences the biochemical metabolism of rice plants remains unknown. Here, purified LqhIT2-GST fusion protein had toxicity to rice leafrollers. Meanwhile, in vitro and field trials showed that LqhIT2 transgenic rice plants were less damaged by rice leafrollers compared to the wild type plants. Introducing LqhIT2 primed the elevated expression of lipoxygenase, a key component of the jasmonic acid biosynthetic pathway, together with enhanced linolenic acid, cis-(+)-12-oxophytodienoic acid, jasmonic acid, and jasmonic acid-isoleucine levels. In addition, phenylalanine ammonia-lyase, a key gene of the phenylpropanoid pathway, was up-regulated. Correspondingly, the contents of downstream products of the phenylpropanoid pathway such as flavonoids and lignins, were also increased in LqhIT2 transgenic plants. These changes were paralleled by decreased starch, glucose, and glucose-6-phosphate accumulation, the key metabolites of glycolysis pathway that supplies the raw material and intermediate carbon products for phenylpropanoids biosyntheses. These findings suggest that, in addition to its own toxicity against pests, LqhIT2 activate the phenylpropanoid pathway via jasmonate-mediated priming, which subsequently increases flavonoid and lignin content and improves insect resistance in rice.
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Affiliation(s)
- Xiuzi Tianpei
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Dong Li
- National Key Laboratory of Genetic Crop Improvement, Huazhong Agriculture University, Wuhan 430070, China
| | - Ping Qiu
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Jie Luo
- National Key Laboratory of Genetic Crop Improvement, Huazhong Agriculture University, Wuhan 430070, China.
| | - Yingguo Zhu
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China
| | - Shaoqing Li
- State Key Laboratory of Hybrid Rice, Key Laboratory for Research and Utilization of Heterosis in Indica Rice of the Ministry of Agriculture, Engineering Research Center for Plant Biotechology and Germplasm Utilization of the Ministry of Education, College of Life Science, Wuhan University, Wuhan 430072, China.
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Tianpei X, Zhu Y, Li S. Optimized scorpion polypeptide LMX: a pest control protein effective against rice leaf folder. PLoS One 2014; 9:e100232. [PMID: 24964088 PMCID: PMC4070919 DOI: 10.1371/journal.pone.0100232] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 05/24/2014] [Indexed: 11/25/2022] Open
Abstract
Lepidopteran insect pests are the main class of pests causing significant damage to crop plant yields. Insecticidal scorpion peptides exhibit toxicity specific for insects. Here, we report that a peptide LMX, optimized from the insect-specific scorpion neurotoxin LqhIT2, showed high levels of activity against rice leaf folder in vitro and in planta. Oral ingestion of LMX protein led to a significant decrease in feeding on rice leaves, repression of larval growth and development, delay in molting, and increase in larval lethality. Compared with LqhIT2 protein, the stability and insecticidal efficacy of LMX was better. Meanwhile, biochemical analysis showed that LMX protein ingestion dramatically decreased ecdysone content in rice leaf folder larvae, and down-regulated enzymatic activities of the detoxification system (α-naphthyl acetate esterase and glutathione S-transferase), the digestive system (tryptase and chymotrypsin), and the antioxidant system (catalase). These changes were tightly correlated with the dosage of LMX protein. Transgene analysis showed that the rate of leaf damage, and the number of damaged tillers and leaves in the transgenic line were greatly reduced relative to wild type plants and empty vector plants. Based on these observations, we propose that the insect-specific scorpion neurotoxin peptide LMX is an attractive and effective alternative molecule for the protection of rice from rice leaf folder.
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Affiliation(s)
- Xiuzi Tianpei
- State Key Laboratory of Hybrid Rice; Key Laboratory for Research and Utilization of Heterosis in Indica Rice of Ministry of Agriculture; Engineering Research Center for Plant Biotechology and Germplasm Utilization of Ministry of Education; College of Life Sciences, Wuhan University, Wuhan, China
| | - Yingguo Zhu
- State Key Laboratory of Hybrid Rice; Key Laboratory for Research and Utilization of Heterosis in Indica Rice of Ministry of Agriculture; Engineering Research Center for Plant Biotechology and Germplasm Utilization of Ministry of Education; College of Life Sciences, Wuhan University, Wuhan, China
| | - Shaoqing Li
- State Key Laboratory of Hybrid Rice; Key Laboratory for Research and Utilization of Heterosis in Indica Rice of Ministry of Agriculture; Engineering Research Center for Plant Biotechology and Germplasm Utilization of Ministry of Education; College of Life Sciences, Wuhan University, Wuhan, China
- * E-mail:
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NeuroBactrus, a novel, highly effective, and environmentally friendly recombinant baculovirus insecticide. Appl Environ Microbiol 2012; 79:141-9. [PMID: 23064343 DOI: 10.1128/aem.02781-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A novel recombinant baculovirus, NeuroBactrus, was constructed to develop an improved baculovirus insecticide with additional beneficial properties, such as a higher insecticidal activity and improved recovery, compared to wild-type baculovirus. For the construction of NeuroBactrus, the Bacillus thuringiensis crystal protein gene (here termed cry1-5) was introduced into the Autographa californica nucleopolyhedrovirus (AcMNPV) genome by fusion of the polyhedrin-cry1-5-polyhedrin genes under the control of the polyhedrin promoter. In the opposite direction, an insect-specific neurotoxin gene, AaIT, from Androctonus australis was introduced under the control of an early promoter from Cotesia plutellae bracovirus by fusion of a partial fragment of orf603. The polyhedrin-Cry1-5-polyhedrin fusion protein expressed by the NeuroBactrus was not only occluded into the polyhedra, but it was also activated by treatment with trypsin, resulting in an ∼65-kDa active toxin. In addition, quantitative PCR revealed that the neurotoxin was expressed from the early phase of infection. NeuroBactrus showed a high level of insecticidal activity against Plutella xylostella larvae and a significant reduction in the median lethal time against Spodoptera exigua larvae compared to those of wild-type AcMNPV. Rerecombinant mutants derived from NeuroBactrus in which AaIT and/or cry1-5 were deleted were generated by serial passages in vitro. Expression of the foreign proteins (B. thuringiensis toxin and AaIT) was continuously reduced during the serial passage of the NeuroBactrus. Moreover, polyhedra collected from S. exigua larvae infected with the serially passaged NeuroBactrus showed insecticidal activity similar to that of wild-type AcMNPV. These results suggested that NeuroBactrus could be recovered to wild-type AcMNPV through serial passaging.
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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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Tang XX, Sun XL, Pu GQ, Wang WB, Zhang CX, Zhu J. Expression of a neurotoxin gene improves the insecticidal activity of Spodoptera litura nucleopolyhedrovirus (SpltNPV). Virus Res 2011; 159:51-6. [DOI: 10.1016/j.virusres.2011.04.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2010] [Revised: 04/25/2011] [Accepted: 04/25/2011] [Indexed: 11/30/2022]
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Recombinant scorpion insect excitatory toxin BmK IT accelerates the growth of insect Spodoptera frugiperda 9 cells. Mol Cell Biochem 2011; 351:93-8. [DOI: 10.1007/s11010-011-0715-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 01/04/2011] [Indexed: 10/18/2022]
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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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Fan X, Zheng B, Fu Y, Sun Y, Liang A. Baculovirus-mediated expression of a Chinese scorpion neurotoxin improves insecticidal efficacy. Sci Bull (Beijing) 2008. [DOI: 10.1007/s11434-008-0242-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Kozminsky-Atias A, Somech E, Zilberberg N. Isolation of the first toxin from the scorpion Buthus occitanus israelis showing preference for Shaker potassium channels. FEBS Lett 2007; 581:2478-84. [PMID: 17490656 DOI: 10.1016/j.febslet.2007.04.065] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 04/22/2007] [Accepted: 04/23/2007] [Indexed: 11/18/2022]
Abstract
We have purified BoiTx1, the first toxin from the venom of the Israeli scorpion, Buthus occitanus israelis, and studied its activity and genomic organization. BoiTx1 is a 37 amino acid-long peptide contained six conserved cysteines, and is classified as an alpha-KTx3.10 toxin. The pharmacological effects of BoiTx1 were studied on various cloned K(+) channels expressed in Xenopus laevis oocytes. BoiTx1 inhibited currents through Drosophila Shaker channels with an IC(50) value of 3.5+/-0.5nM, yet had much lesser effect on its mammalian orthologs. Thus, BoiTx1 is the first member of the alpha-KTx3 family that preferentially affects insect potassium channels.
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Affiliation(s)
- Adi Kozminsky-Atias
- Department of Life Sciences and the Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Bosmans F, Tytgat J. Sea anemone venom as a source of insecticidal peptides acting on voltage-gated Na+ channels. Toxicon 2007; 49:550-60. [PMID: 17224168 PMCID: PMC1868498 DOI: 10.1016/j.toxicon.2006.11.029] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 11/17/2006] [Indexed: 12/19/2022]
Abstract
Sea anemones produce a myriad of toxic peptides and proteins of which a large group acts on voltage-gated Na+ channels. However, in comparison to other organisms, their venoms and toxins are poorly studied. Most of the known voltage-gated Na+ channel toxins isolated from sea anemone venoms act on neurotoxin receptor site 3 and inhibit the inactivation of these channels. Furthermore, it seems that most of these toxins have a distinct preference for crustaceans. Given the close evolutionary relationship between crustaceans and insects, it is not surprising that sea anemone toxins also profoundly affect insect voltage-gated Na+ channels, which constitutes the scope of this review. For this reason, these peptides can be considered as insecticidal lead compounds in the development of insecticides.
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Affiliation(s)
- Frank Bosmans
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, Building 35, 3B 211, NINDS, NIH, Bethesda, MD 20892, USA
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Abstract
Since the introduction of DDT in the 1940s, arthropod pest control has relied heavily upon chemical insecticides. However, the development of insect resistance, an increased awareness of the real and perceived environmental and health impacts of these chemicals, and the need for systems with a smaller environmental footprint has stimulated the search for new insecticidal compounds, novel molecular targets, and alternative control methods. In recent decades a variety of biocontrol methods employing peptidic or proteinaceous insect-specific toxins derived from microbes, plants and animals have been examined in the laboratory and field with varying results. Among the many interdependent factors involved with the production of a cost-effective pesticide--production expense, kill efficiency, environmental persistence, pest-specificity, pest resistance-development, public perception and ease of delivery--sprayable biopesticides have not yet found equal competitive footing with chemical counterparts. However, while protein/peptide-based biopesticides continue to have limitations, advances in the technology, particularly of genetically modified organisms as biopesticidal delivery systems, has continually progressed. This review highlights the varieties of delivery methods currently practiced, examining the strengths and weaknesses of each method.
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Gurevitz M, Karbat I, Cohen L, Ilan N, Kahn R, Turkov M, Stankiewicz M, Stühmer W, Dong K, Gordon D. The insecticidal potential of scorpion β-toxins. Toxicon 2007; 49:473-89. [PMID: 17197009 DOI: 10.1016/j.toxicon.2006.11.015] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 11/20/2006] [Indexed: 11/28/2022]
Abstract
Voltage-gated sodium channels are a major target for toxins and insecticides due to their central role in excitability, but due to the conservation of these channels in Animalia most insecticides do not distinguish between those of insects and mammals, thereby imposing risks to humans and livestock. Evidently, as long as modern agriculture depends heavily on the use of insecticides there is a great need for new substances capable of differentiating between sodium channel subtypes. Such substances exist in venomous animals, but ways for their exploitation have not yet been developed due to problems associated with manufacturing, degradation, and delivery to the target channels. Engineering of plants for expression of anti-insect toxins or use of natural vectors that express toxins near their target site (e.g. baculoviruses) are still problematic and raise public concern. In this problematic reality a rational approach might be to learn from nature how to design highly selective anti-insect compounds preferably in the form of peptidomimetics. This is a complex task that requires the elucidation of the face of interaction between insect-selective toxins and their sodium channel receptor sites. This review delineates current progress in: (i) elucidation of the bioactive surfaces of scorpion beta-toxins, especially the excitatory and depressant groups, which show high preference for insects and bind insect sodium channels with high affinity; (ii) studies of the mode of interaction of scorpion beta-toxins with receptor site-4 on voltage-gated sodium channels; and (iii) clarification of channel elements that constitute receptor site-4. This information may be useful in future attempts to mimic the bioactive surface of the toxins for the design of anti-insect selective peptidomimetics.
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Affiliation(s)
- Michael Gurevitz
- Department of Plant Sciences, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel.
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Nicholson GM. Insect-selective spider toxins targeting voltage-gated sodium channels. Toxicon 2007; 49:490-512. [PMID: 17223149 DOI: 10.1016/j.toxicon.2006.11.027] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Accepted: 11/17/2006] [Indexed: 12/21/2022]
Abstract
The voltage-gated sodium (Na(v)) channel is a target for a number of drugs, insecticides and neurotoxins. These bind to at least seven identified neurotoxin binding sites and either block conductance or modulate Na(v) channel gating. A number of peptide neurotoxins from the venoms of araneomorph and mygalomorph spiders have been isolated and characterized and determined to interact with several of these sites. These all conform to an 'inhibitor cystine-knot' motif with structural, but not sequence homology, to a variety of other spider and marine snail toxins. Of these, spider toxins several show phyla-specificity and are being considered as lead compounds for the development of biopesticides. Hainantoxin-I appears to target site-1 to block Na(v) channel conductance. Magi 2 and Tx4(6-1) slow Na(v) channel inactivation via an interaction with site-3. The delta-palutoxins, and most likely mu-agatoxins and curtatoxins, target site-4. However, their action is complex with the mu-agatoxins causing a hyperpolarizing shift in the voltage-dependence of activation, an action analogous to scorpion beta-toxins, but with both delta-palutoxins and mu-agatoxins slowing Na(v) channel inactivation, a site-3-like action. In addition, several other spider neurotoxins, such as delta-atracotoxins, are known to target both insect and vertebrate Na(v) channels most likely as a result of the conserved structures within domains of voltage-gated ion channels across phyla. These toxins may provide tools to establish the molecular determinants of invertebrate selectivity. These studies are being greatly assisted by the determination of the pharmacophore of these toxins, but without precise identification of their binding site and mode of action their potential in the above areas remains underdeveloped.
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Affiliation(s)
- Graham M Nicholson
- Neurotoxin Research Group, Department of Medical and Molecular Biosciences, University of Technology, Sydney P.O. Box 123, Broadway, NSW 2007, Australia.
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Nicholson GM. Fighting the global pest problem: preface to the special Toxicon issue on insecticidal toxins and their potential for insect pest control. Toxicon 2006; 49:413-22. [PMID: 17223148 DOI: 10.1016/j.toxicon.2006.11.028] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 11/17/2006] [Indexed: 12/21/2022]
Abstract
Arthropod pests are responsible for major crop devastation and are vectors for the transmission of new and re-emerging diseases in humans and livestock. Despite many years of effective control by conventional agrochemical insecticides, a number of factors are threatening the effectiveness and continued use of these agents. These include the development of insecticide resistance and use-cancellation or de-registration of some insecticides due to human health and environmental concerns. Several approaches are being investigated for the design of new (bio)pesticides. These include the development of transgenic plants and recombinant baculoviruses as delivery systems for a variety of insect-selective toxins. Additional approaches for the development of foliar sprays include the rational design of peptidomimetics based on the key residues of these toxins that interact with the insect target. This special issue provides an overview of these phyletically selective animal, plant and microbial toxins and their diverse mechanisms of action to paralyze or kill arthropods. In addition, it reviews their potential for biopesticide discovery and validation of novel insecticide targets and provides an overview of the strengths and weaknesses of biopesticides in the global control of arthropod pests.
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Affiliation(s)
- Graham M Nicholson
- Neurotoxin Research Group, Department of Medical & Molecular Biosciences, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007, Australia.
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Regev A, Rivkin H, Gurevitz M, Chejanovsky N. New measures of insecticidal efficacy and safety obtained with the 39K promoter of a recombinant baculovirus. FEBS Lett 2006; 580:6777-82. [PMID: 17141223 DOI: 10.1016/j.febslet.2006.11.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Accepted: 11/16/2006] [Indexed: 11/27/2022]
Abstract
Baculoviruses are orally infectious to insects and considered to be natural insecticides. To enhance their speed-of-kill these viruses were engineered to express arthropod neurotoxins under the control of various strong promoters. Although this strategy proved to be efficient, it raised recently concerns about safety. We analyzed the speed-of-kill and safety of Autographa californica multiple nucleopolyhedrovirus expressing the insecticidal scorpion neurotoxin AaIT and found that the mortality of Helicoverpa armigera larvae was enhanced significantly when the expression was controlled by the baculovirus delayed-early promoter 39K rather than the very late promoter p10. This improvement was also reflected in better protection of cotton leaves on which these insects were fed. Using lacZ as a sensitive reporter we also found that expression driven by the 39K promoter was detected in insect but not in mammalian cells. These results imply that by selection of an appropriate viral promoter, engineered baculoviruses may comply with the high standard biosafety requirements from a genetically modified organism (GMO). Our results provide further support for the potential use of engineered baculoviruses in insect pest control in a safely manner.
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Affiliation(s)
- Avital Regev
- Entomology Department, Institute of Plant Protection, ARO, The Volcani Center, POB 6, Bet Dagan 50250, Israel
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Inceoglu AB, Kamita SG, Hammock BD. Genetically modified baculoviruses: a historical overview and future outlook. Adv Virus Res 2006; 68:323-60. [PMID: 16997016 DOI: 10.1016/s0065-3527(06)68009-3] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The concept of using genetic engineering to improve the natural insecticidal activity of baculoviruses emerged during the 1980s. Both academic and industrial laboratories have since invested a great deal of effort to generate genetically modified (GM) or recombinant baculoviruses with dramatically improved speeds of kill. Optimal production methodologies and formulations have also been developed, and the safety and ecology of the recombinant baculoviruses have been thoroughly investigated. Unfortunately, the initial excitement that was generated by these technologies was tempered when industry made a critical decision to not complete the registration process of GM baculoviruses for pest insect control. In this chapter, we summarize the developments in the field from a historical perspective and provide our opinions as to the current status and future potential of the technology. We will argue that GM baculoviruses are valuable and viable tools for pest insect control both alone and in combination with wild-type viruses. We believe that these highly effective biopesticides still have a bright future in modern agriculture as public awareness and acceptance of GM organisms, including GM baculoviruses, increases.
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Affiliation(s)
- A Bora Inceoglu
- Department of Entomology and Cancer Research Center University of California, Davis, California 95616, USA
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Abstract
Voltage-gated Na(+) channels are integral membrane proteins that function as a gateway for a selective permeation of sodium ions across biological membranes. In this way, they are crucial players for the generation of action potentials in excitable cells. Voltage-gated Na(+) channels are encoded by at least nine genes in mammals. The different isoforms have remarkably similar functional properties, but small changes in function and pharmacology are biologically well-defined, as underscored by mutations that cause several diseases and by modulation of a myriad of compounds, respectively. This review will stress on the modulation of voltage-gated Na(+) channels by scorpion alpha-toxins. Nature has designed these two classes of molecules as if they were predestined to each other: an inevitable 'encounter' between a voltage-gated Na(+) channel isoform and an alpha-toxin from scorpion venom indeed results in a dramatically changed Na(+) current phenotype with clear-cut consequences on electrical excitability and sometimes life or death. This fascinating aspect justifies an overview on scorpion venoms, their alpha-toxins and the Na(+) channel targets they are built for, as well as on the molecular determinants that govern the selectivity and affinity of this 'inseparable duo'.
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Affiliation(s)
- Frank Bosmans
- Laboratory of Toxicology, University of Leuven, O and N 2, Postbus 922, Herestraat 49, 3000 Leuven, Belgium
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Jinn TR, Tu WC, Lu CI, Tzen JTC. Enhancing insecticidal efficacy of baculovirus by early expressing an insect neurotoxin, LqhIT2, in infected Trichoplusia ni larvae. Appl Microbiol Biotechnol 2006; 72:1247-53. [PMID: 16636828 DOI: 10.1007/s00253-006-0431-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2006] [Revised: 03/10/2006] [Accepted: 03/15/2006] [Indexed: 10/24/2022]
Abstract
LqhIT(2), an insect specific neurotoxin from the venom of Leiurus quinquestriatus hebraeus, has been demonstrated to improve insecticidal efficacy of Autographa californica nuclear polyhedrosis virus (AcMNPV). A polyhedrin-positive recombinant AcMNPVvAcP(hsp70)EGFP/P(pag90)IT(2) was engineered for larvae to express the enhanced green fluorescence protein (EGFP) and LqhIT(2) under the control of P(hsp70) and P(pag90) promoters, respectively. This would allow a visual observation of the viral infection and an improvement of the insecticidal efficacy. The insecticidal activity of this recombinant baculovirus, a wild type AcMNPV and four other recombinant baculoviruses, was evaluated and compared in terms of mortality, body weight, median lethal time (LT(50)), and median lethal concentration (LC(50)). Insecticidal efficacy was unaltered when treated with vAcP(hsp70)EGFP, moderately improved when infected by vAcP(10)IT(2) (a P(10)-promoted LqhIT ( 2 ) gene), and significantly elevated when treated with vAcP(pag90)IT(2) or vAcP(hsp70)EGFP/P(pag90)IT(2). No apparent difference was observed in insecticidal efficacy when additional EGFP was expressed as a visible marker. These results suggest that recombinant AcMNPV vAcP(hsp70)EGFP/P(pag90)IT(2) may be used as an effective insecticide against Trichoplusia ni and other lepidopterous insect pests.
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Affiliation(s)
- Tzyy-Rong Jinn
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan 40227, Republic of China
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Tan PTJ, Ranganathan S, Brusic V. Deduction of functional peptide motifs in scorpion toxins. J Pept Sci 2006; 12:420-7. [PMID: 16432807 DOI: 10.1002/psc.744] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Scorpion toxins are important physiological probes for characterizing ion channels. Molecular databases have limited functional annotation of scorpion toxins. Their function can be inferred by searching for conserved motifs in sequence signature databases that are derived statistically but are not necessarily biologically relevant. Mutation studies provide biological information on residues and positions important for structure-function relationship but are not normally used for extraction of binding motifs. 3D structure analyses also aid in the extraction of peptide motifs in which non-contiguous residues are clustered spatially. Here we present new, functionally relevant peptide motifs for ion channels, derived from the analyses of scorpion toxin native and mutant peptides.
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Affiliation(s)
- Paul T J Tan
- Institute for Infocomm Research, 21 Heng Mui Keng Terrace, Singapore 119613
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Rajendra W, Hackett KJ, Buckley E, Hammock BD. Functional expression of lepidopteran-selective neurotoxin in baculovirus: potential for effective pest management. Biochim Biophys Acta Gen Subj 2005; 1760:158-63. [PMID: 16406338 DOI: 10.1016/j.bbagen.2005.11.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2005] [Revised: 10/23/2005] [Accepted: 11/16/2005] [Indexed: 11/23/2022]
Abstract
Recombinant baculovirus expressing insect-selective neurotoxins derived from venomous animals are considered as an attractive alternative to chemical insecticides for efficient insect control agents. Recently we identified and characterized a novel lepidopteran-selective toxin, Buthus tamulus insect-selective toxin (ButaIT), having 37 amino acids and eight half cysteine residues from the venom of the South Indian red scorpion, Mesobuthus tamulus. The synthetic toxin gene containing the ButaIT sequence in frame to the bombyxin signal sequence was engineered into a polyhedrin positive Autographa californica nuclear polyhedrosis virus (AcMNPV) genome under the control of the p10 promoter. Toxin expression in the haemolymph of infected larvae of Heliothis virescens and also in an insect cell culture system was confirmed by western blot analysis using antibody raised against the GST-ButaIT fusion protein. The recombinant NPV (ButaIT-NPV) showed enhanced insecticidal activity on the larvae of Heliothis virescens as evidenced by a significant reduction in median survival time (ST50) and also a greater reduction in feeding damage as compared to the wild-type AcMNPV.
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Affiliation(s)
- Wudayagiri Rajendra
- Division of Molecular Biology, Department of Zoology, Sri Venkateswara University, Tirupati-517 502, India.
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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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Szewczyk B, Hoyos-Carvajal L, Paluszek M, Skrzecz I, Lobo de Souza M. Baculoviruses-- re-emerging biopesticides. Biotechnol Adv 2005; 24:143-60. [PMID: 16257169 DOI: 10.1016/j.biotechadv.2005.09.001] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2005] [Revised: 08/19/2005] [Accepted: 09/09/2005] [Indexed: 11/28/2022]
Abstract
Biological control of agricultural pests has gained importance in recent years due to increased pressure to reduce the use of agrochemicals and their residues in the environment and food. Viruses of a few families are known to infect insects but only those belonging to the highly specialized family Baculoviridae have been used as biopesticides. They are safe to people and wildlife, their specificity is very narrow. Their application as bioinsecticides was limited until recently because of their slow killing action and technical difficulties for in vitro commercial production. Two approaches for the wider application of baculoviruses as biopesticides will be implemented in future. In countries where use of genetically modified organisms is restricted, the improvements will be mainly at the level of diagnostics, in vitro production and changes in biopesticide formulations. In the second approach, the killing activity of baculoviruses may be augmented by genetic modifications of the baculovirus genome with genes of another natural pathogen. It is expected that the baculoviruses improved by genetic modifications will be gradually introduced in countries which have fewer concerns towards genetically modified organisms.
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Affiliation(s)
- Boguslaw Szewczyk
- Department of Molecular Virology, Intercollegiate Faculty of Biotechnology of the University of Gdansk and Medical University of Gdansk, Kladki 24, 80-822 GDANSK, Poland.
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Zhang Z, Ye GY, Cai J, Hu C. Comparative venom toxicity between Pteromalus puparum and Nasonia vitripennis (Hymenoptera: Pteromalidae) toward the hemocytes of their natural hosts, non-target insects and cultured insect cells. Toxicon 2005; 46:337-49. [PMID: 16026808 DOI: 10.1016/j.toxicon.2005.05.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Revised: 05/07/2005] [Accepted: 05/31/2005] [Indexed: 11/23/2022]
Abstract
Crude venoms from two parasitoid species, Pteromalus puparum and Nasonia vitripennis (Hymenoptera: Pteromalidae) were assayed for biological activities toward hemocytes from two species of their natural hosts and eight species of their non-natural hosts as well as two lines of cultured Lepidoptera cells, respectively. By inhibiting the spreading and viability of insect hemocytes, the venom from P. puparum displayed significantly higher activities toward plasmatocytes and granular cells from both larvae and pupae of two natural hosts, Pieris rapae and Papilio xuthus, and lower activity toward those from Spodoptera litura, Musca domestica and Sarcophaga peregrina. However, no effect was found towards any type of hemocytes from other five insects tested, namely, Ectropis oblique, Galleria mellonella, Sesamia inferens, Bombyx mori and Parnara guttata. In contrast, the venom from N. vitripennis showed a narrower range of targeted insects. It appeared to have highly adverse effects on the spreading and viability of plasmatocytes and granular cells only from the natural hosts, M. domestica and S. peregrina, little toxicity to cells from P. rapae and P. xuthus, and no effect on any of the other insects tested. Pteromalus puparum venom also apparently presented a high ability to block the spreading of Tn-5B1-4 cells derived from Trichoplusia ni, and high cytotoxicity to the cells and Ha cells derived from Helicoverpa armigera. Nasonia vitripennis venom, however, only had a marked lethal effect to Ha cells. In addition, the possibility that the host range of a defined parasitoid could be assessed using our method of treating hemocytes from candidate insects with venom in vitro, and the potential of our venoms tested in the development of bio-insecticides, insect-resistant transgenic plants, are discussed.
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Affiliation(s)
- Zhong Zhang
- State Key Laboratory of Rice Biology, Institute of Applied Entomology, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310029, China
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Wullschleger B, Nentwig W, Kuhn-Nentwig L. Spider venom: enhancement of venom efficacy mediated by different synergistic strategies in Cupiennius salei. ACTA ACUST UNITED AC 2005; 208:2115-21. [PMID: 15914655 DOI: 10.1242/jeb.01594] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Besides the power of the chelicerae, synergistic interactions between different components in the venom of Cupiennius salei ensure the hunting success of this spider. The main components of the venom were tested alone or in combination according to their physiological venom concentrations in Drosophila bioassays. The high K+ ion content of the venom synergistically increases the insecticidal activity of the neurotoxins CSTX-1, CSTX-9 and CSTX-13 by 20% but does not influence the insecticidal effectiveness of the antimicrobially and cytolytically acting cupiennin 1a. Histamine only enhances the activity of the main neurotoxin CSTX-1. An important role in the envenomation process is exhibited by cupiennin 1a, which increases the insecticidal activity of the above-mentioned neurotoxins by up to 65%. Additionally, the highly synergistic effect of the enhancer CSTX-13 on CSTX-1, provoked in non-toxic physiological concentrations, could be verified for CSTX-9, but not for cupiennin 1a. CSTX-1 and CSTX-9 show positive interactions only when both are injected in toxic non-physiological concentrations.
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Affiliation(s)
- Benno Wullschleger
- Zoological Institute, University of Bern, Baltzerstrasse 6, CH-3012 Bern, Switzerland
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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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Wullschleger B, Kuhn-Nentwig L, Tromp J, Kämpfer U, Schaller J, Schürch S, Nentwig W. CSTX-13, a highly synergistically acting two-chain neurotoxic enhancer in the venom of the spider Cupiennius salei (Ctenidae). Proc Natl Acad Sci U S A 2004; 101:11251-6. [PMID: 15272079 PMCID: PMC509190 DOI: 10.1073/pnas.0402226101] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The survival of the spider Cupiennius salei depends on its hunting success, which largely relies on its immediately paralyzing multicomponent venom. Here, we report on the isolation and characterization of CSTX-13, a neurotoxic enhancer in the spider venom. De novo elucidation of the disulfide bridge pattern of CSTX-13 and the neurotoxin CSTX-1 by tandem MS revealed an identical arrangement. However, in contrast to CSTX-1, CSTX-13 is a two-chain peptide with two interchain and two intrachain disulfide bridges. Furthermore, the insecticidal activity of CSTX-13 is synergistically increased in the presence of K+ ions as well as of the cytolytic peptide cupiennin 1a. We demonstrated that the weakly neurotoxic CSTX-13 enhances the paralytic activity of the neurotoxin CSTX-1 by 65% when it is administered with the latter at its entirely nontoxic physiological concentration, which is 440 times below its LD50 concentration.
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Affiliation(s)
- Benno Wullschleger
- Zoological Institute, University of Bern, Baltzerstrasse 6, CH-3012 Bern, Switzerland
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Szolajska E, Poznanski J, Ferber ML, Michalik J, Gout E, Fender P, Bailly I, Dublet B, Chroboczek J. Poneratoxin, a neurotoxin from ant venom. ACTA ACUST UNITED AC 2004; 271:2127-36. [PMID: 15153103 DOI: 10.1111/j.1432-1033.2004.04128.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Poneratoxin is a small neuropeptide found in the venom of the ant Paraponera clavata. It is stored in the venom reservoir as an inactive 25-residue peptide. Here we describe both chemically synthesized poneratoxin and poneratoxin obtained by expression in insect cells. When expressed in insect cells, poneratoxin was observed attached to cell membranes. Both synthetic and recombinant ponerotoxins were soluble below pH 4.5. The structure of synthetic poneratoxin was characterized by circular dichroism and solved by nuclear magnetic resonance. In an environment imitating a lipid bilayer, at pH within the range of insect hemolymph, synthetic poneratoxin has a V shape, with two alpha-helices connected by a beta-turn. Insect larvae were paralyzed by injection of either of the purified toxins, with the recombinant one acting faster. The recombinant toxin-producing baculovirus reduced the average survival time of the insect host by 25 h compared with unmodified virus. Mass spectrometry analysis showed that the recombinant toxin has an N-terminal 21-residue extension, possibly improving its stability and/or stabilizing the membrane-bound state. The potential use of poneratoxin for the construction of biological insecticide is discussed.
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Affiliation(s)
- Ewa Szolajska
- Institute of Biochemistry and Biophysics (IBB), Polish Academy of Sciences, Warsaw, Poland
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Abstract
Arthropods are the most diverse animal group on the planet. Their ability to inhabit a vast array of ecological niches has inevitably brought them into conflict with humans. Although only a small minority are classified as pest species, they nevertheless destroy about a quarter of the world's annual crop production and transmit an impressive array of pathogens of human and veterinary public health importance. Arthropod pests have been controlled almost exclusively with chemical insecticides since the introduction of DDT in the 1940s. However, the evolution of resistance to many insecticides, coupled with increased awareness of the potential environmental and human and animal health impacts of these chemicals, has stimulated the search for new insecticidal compounds, novel molecular targets, and alternative control methods. Spider venoms are complex chemical cocktails that have evolved to kill or paralyze arthropod prey, and they represent a largely untapped reservoir of insecticidal compounds. This review focuses on several families of invertebrate-specific peptide neurotoxins that were isolated from the venom of Australian funnel-web spiders. These peptides are promising insecticide leads because of their selectivity for invertebrates and activity on previously unvalidated targets. These toxins should facilitate the development of novel target-based screens for new insecticide leads, while their mapped pharmacophores will provide templates for rational design of mimetics that act at these target sites. Furthermore, genes encoding these toxins can be used to improve the efficacy of insect-specific viruses.
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Affiliation(s)
- Hugo W Tedford
- Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06032-3305, USA
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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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35
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Chang JH, Choi JY, Jin BR, Roh JY, Olszewski JA, Seo SJ, O'Reilly DR, Je YH. An improved baculovirus insecticide producing occlusion bodies that contain Bacillus thuringiensis insect toxin. J Invertebr Pathol 2003; 84:30-7. [PMID: 13678710 DOI: 10.1016/s0022-2011(03)00121-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Baculovirus occlusion bodies, large proteinaceous structures which contain virions, have recently been engineered to incorporate foreign proteins. The major constituent protein of occlusion bodies from the baculovirus Autographa californica nucleopolyhedrovirus is polyhedrin, and assembly of recombinant occlusion bodies which incorporate a foreign protein depends on an interaction between native polyhedrin and a polyhedrin-foreign protein fusion. This technology has now been applied to the generation of a recombinant baculovirus (ColorBtrus) that produces occlusion bodies incorporating the Bacillus thuringiensis (Bt) insecticidal Cry1Ac toxin protein. ColorBtrus coexpresses native polyhedrin and a fusion protein in which polyhedrin is fused to the Bt toxin, which is in turn fused to green fluorescent protein (GFP). Analysis of ColorBtrus occlusion bodies confirmed that they include both Bt toxin and GFP, yet still incorporate virions. Bioassay of ColorBtrus demonstrated that its speed of action and pathogenicity are strikingly enhanced compared to wild-type virus. ColorBtrus represents a novel, powerful biological insecticide that combines positive attributes of both Bt toxin and baculovirus based systems.
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Affiliation(s)
- Jin Hee Chang
- School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Suwon 441-744, Republic of Korea
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Gilles N, Gurevitz M, Gordon D. Allosteric interactions among pyrethroid, brevetoxin, and scorpion toxin receptors on insect sodium channels raise an alternative approach for insect control. FEBS Lett 2003; 540:81-5. [PMID: 12681487 DOI: 10.1016/s0014-5793(03)00226-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Intensive pyrethroid use in insect control has led to resistance buildup among various pests. One alternative to battle this problem envisions the combined use of synergistically acting insecticidal compounds. Pyrethroids, scorpion alpha- and beta-toxins, and brevetoxins bind to distinct receptor sites on voltage-gated sodium channels (NaChs) and modify their function. The binding affinity of scorpion alpha-toxins to locust, but not rat-brain NaChs, is allosterically increased by pyrethroids and by brevetoxin-1. Brevetoxin-1 also increases the binding of an excitatory beta-toxin to insect NaChs. These results reveal differences between insect and mammalian NaChs and may be exploited in new strategies of insect control.
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Affiliation(s)
- Nicolas Gilles
- CEA, Département d'Ingénierie et d'Etudes des Protéines, CE Saclay, 91191 Gif-sur-Yvette, France
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