The effects of knock-down resistance mutations and alternative splicing on voltage-gated sodium channels in Musca domestica and Drosophila melanogaster. (July 2020)

• Record Type: Journal Article
• Authors: 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.
• Is Part Of: Insect biochemistry and molecular biology. Volume 122(2020)
• Publication Date: 2020-07
• Subjects: Voltage-gated sodium channel -- Pyrethroid -- Splice variant -- Insecticide resistance -- Xenopus oocyte; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2020.103388
• Languages: English
• ISSNs: 0965-1748

Abstract

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 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. Graphical abstract: Image 1 Highlights: Neuronal voltage-gated sodium channels in houseflies produce either strongly inactivating or more persistent currents. Tail currents and shifts in voltage sensitivity are more sensitive to deltamethrin in wild-type than resistant houseflies. The persistent current in both strains was more sensitive to deltamethrin than was the inactivating type. Orthologues of Drosophila voltage-gated sodium channel splice variants k and l are expressed in housefly heads. The l splice variant, with a persistent current, is more sensitive to deltamethrin than the k splice variant.