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

A - Papers appearing in refereed journals

Thompson, A. J., Verdin, P. S., Burton, M. J., Davies, T. G. E., Williamson, M. S., Field, L. M., Baines, R. A., Mellor, I. R. and 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, p. 103388.

AuthorsThompson, A. J., Verdin, P. S., Burton, M. J., Davies, T. G. E., Williamson, M. S., Field, L. M., Baines, R. A., Mellor, I. R. and Duce, I. R.
Abstract

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 post transcriptional 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.

KeywordsVoltage-gated sodium channel ; Pyrethroid ; Splice variant ; Insecticide resistance; Xenopus oocyte
Year of Publication2020
JournalInsect Biochemistry and Molecular Biology
Journal citation122, p. 103388
Digital Object Identifier (DOI)doi:10.1016/j.ibmb.2020.103388
Web address (URL)https://www.sciencedirect.com/science/article/pii/S0965174820300771?via%3Dihub
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Lawes Agricultural Trust
BBSRC Industrial Strategy Challenge
Funder project or codeBB/G005885/1
BBSRC Strategic Programme in Smart Crop Protection
Output statusPublished
Publication dates
Online04 May 2020
Publication process dates
Accepted13 Apr 2020
PublisherElsevier
ISSN0965-1748

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