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The effects of knock-down resistance mutations and alternative splicing on voltage-gated sodium channels in Musca domestica and Drosophila melanogaster

Thompson, Andrew J.; Verdin, Paul S.; Burton, Mark J.; Davies, T. G.Emyr; Williamson, Martin S.; Field, Linda M.; Baines, Richard A.; Mellor, Ian R.; Duce, Ian R.

Authors

Andrew J. Thompson

Paul S. Verdin

Mark J. Burton

T. G.Emyr Davies

Martin S. Williamson

Linda M. Field

Richard A. Baines

IAN MELLOR ian.mellor@nottingham.ac.uk
Assistant Professor

Ian R. Duce



Abstract

© 2020 Elsevier Ltd Voltage-gated sodium channels (VGSCs) are a major target site for the action of pyrethroid insecticides and resistance to pyrethroids has been ascribed to mutations in the VGSC gene. VGSCs in insects are encoded by only one gene and their structural and functional diversity results from posttranscriptional modification, particularly, alternative splicing. Using whole cell patch clamping of neurons from pyrethroid susceptible (wild-type) and resistant strains (s-kdr) of housefly, Musca domestica, we have shown that the V50 for activation and steady state inactivation of sodium currents (INa+) is significantly depolarised in s-kdr neurons compared with wild-type and that 10 nM deltamethrin significantly hyperpolarised both of these parameters in the neurons from susceptible but not s-kdr houseflies. Similarly, tail currents were more sensitive to deltamethrin in wild-type neurons (EC15 14.5 nM) than s-kdr (EC15 133 nM). We also found that in both strains, INa+ are of two types: a strongly inactivating (to 6.8% of peak) current, and a more persistent (to 17.1% of peak) current. Analysis of tail currents showed that the persistent current in both strains (wild-type EC15 5.84 nM) was more sensitive to deltamethrin than was the inactivating type (wild-type EC15 35.1 nM). It has been shown previously, that the presence of exon l in the Drosophila melanogaster VGSC gives rise to a more persistent INa+ than does the alternative splice variant containing exon k and we used PCR with housefly head cDNA to confirm the presence of the housefly orthologues of splice variants k and l. Their effect on deltamethrin sensitivity was determined by examining INa+ in Xenopus oocytes expressing either the k or l variants of the Drosophila para VGSC. Analysis of tail currents, in the presence of various concentrations of deltamethrin, showed that the l splice variant was significantly more sensitive (EC50 42 nM) than the k splice variant (EC50 866 nM). We conclude that in addition to the presence of point mutations, target site resistance to pyrethroids may involve the differential expression of splice variants.

Citation

Thompson, A. J., Verdin, P. S., Burton, M. J., Davies, T. G., Williamson, M. S., Field, L. M., …Duce, I. R. (2020). The effects of knock-down resistance mutations and alternative splicing on voltage-gated sodium channels in Musca domestica and Drosophila melanogaster. Insect Biochemistry and Molecular Biology, 122, https://doi.org/10.1016/j.ibmb.2020.103388

Journal Article Type Article
Acceptance Date Apr 13, 2020
Online Publication Date May 4, 2020
Publication Date Jul 1, 2020
Deposit Date Jul 17, 2020
Publicly Available Date May 5, 2021
Journal Insect Biochemistry and Molecular Biology
Print ISSN 0965-1748
Electronic ISSN 1879-0240
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 122
Article Number 103388
DOI https://doi.org/10.1016/j.ibmb.2020.103388
Keywords Insect Science; Biochemistry; Molecular Biology
Public URL https://nottingham-repository.worktribe.com/output/4489260
Publisher URL https://www.sciencedirect.com/science/article/pii/S0965174820300771

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