Article

An alanine in segment 3 of domain III (IIIS3) of the cockroach sodium channel contributes to the low pyrethroid sensitivity of an alternative splice variant.

Department of Entomology, Michigan State University, East Lansing, MI 48824, USA.
Insect Biochemistry and Molecular Biology (Impact Factor: 3.42). 03/2006; 36(2):161-8. DOI: 10.1016/j.ibmb.2005.11.008
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ABSTRACT In a previous study, we showed that two alternative exons (G1 and G2 encoding IIIS3-S4) were involved in the differential sensitivity of two cockroach sodium channel splice variants, BgNa(v)1-1 and BgNa(v)2-1 (previously called KD1 and KD2), to deltamethrin, a pyrethroid insecticide (Tan, et al., 2002b. Alternative splicing of an insect sodium channel gene generates pharmacologically distinct sodium channels. J. Neurosci. 22, 5300-5309.). Here, we report the identification of an amino acid residue in exon G2 that contributes to the low deltamethrin sensitivity of BgNa(v)2-1. Replacement of A1356 in BgNa(v)2-1 with the corresponding V1356 in BgNa(v)1-1 enhanced the sensitivity of the BgNa(v)2-1 channel to deltamethrin by six-fold. Conversely, substitution of V1356 with A1356 in BgNa(v)1-1 produced a recombinant BgNa(v)1-1 channel that was 5-fold more resistant to deltamethrin. These results demonstrate that A1356 contributes to the low sensitivity of BgNa(v)2-1 to deltamethrin. A1356V substitution also shifted the voltage-dependence of activation by 10 mV in the hyperpolarizing direction. Possible mechanisms by which this amino acid change affects the action of pyrethroids on the sodium channel are discussed.

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    • "The two varieties BgNa V 1.1a and BgNa V 1.1b 1 , which contain the exons l and k respectively, exhibit distinct electrophysiological properties. Furthermore, BgNa V 1.1b is 100X more resistant to the pyrethroid deltamethrin than BgNa V 1.1a (Du et al., 2006). "
    Insecticides - Basic and Other Applications, 02/2012; , ISBN: 978-953-51-0007-2
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    • "The differential pyrethroid sensitivities between BgNa v 1-1 and BgNa v 2-1 channels are partially attributable to the presence of exon G1 and G2, respectively (Tan et al., 2002). A V1356A change in exon G2 reduces the sensitivity of BgNa v 2-1 channels to pyrethroids (Du et al., 2006). In addition to the selective inclusion of exon G1 or G2, BgNa v 1-1 and BgNa v 2-1 also contain nine amino acid differences scattered throughout the protein. "
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    ABSTRACT: Voltage-gated sodium channels are the primary target of pyrethroids, an important class of synthetic insecticides. Pyrethroids bind to a distinct receptor site on sodium channels and prolong the open state by inhibiting channel deactivation and inactivation. Recent studies have begun to reveal sodium channel residues important for pyrethroid binding. However, how pyrethroid binding leads to inhibition of sodium channel deactivation and inactivation remains elusive. In this study, we show that a negatively charged aspartic acid residue at position 802 (D802) located in the extracellular end of transmembrane segment 1 of domain II (IIS1) is critical for both the action of pyrethroids and the voltage dependence of channel activation. Charge-reversing or -neutralizing substitutions (K, G, or A) of D802 shifted the voltage dependence of activation in the depolarizing direction and reduced channel sensitivity to deltamethrin, a pyrethroid insecticide. The charge-reversing mutation D802K also accelerated open-state deactivation, which may have counteracted the inhibition of sodium channel deactivation by deltamethrin. In contrast, the D802G substitution slowed open-state deactivation, suggesting an additional mechanism for neutralizing the action of deltamethrin. Importantly, Schild analysis showed that D802 is not involved in pyrethroid binding. Thus, we have identified a sodium channel residue that is critical for regulating the action of pyrethroids on the sodium channel without affecting the receptor site of pyrethroids.
    Toxicology and Applied Pharmacology 08/2010; 247(1):53-9. DOI:10.1016/j.taap.2010.05.016 · 3.63 Impact Factor
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    • "This mutation has been confirmed to confer strong insensitivity to a number of pyrethroids by functional assays (He et al., 1999; Tan et al., 2005). Target-site resistance has been also associated with sodium channel alternate transcriptional variation and/or posttranscriptional modifications in some species (Tan et al., 2002a; Du et al., 2006), although the possible broader role of such changes in other species remains unclear. Here we have investigated the resistance mechanism responsible for high levels of bifenthrin resistance in two T. urticae strains from Greece, isolated cDNA sequences that encode a large part of the T. urticae para sodium channel and identified mutations associated with the resistance phenotype. "
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    ABSTRACT: We investigated pyrethroid resistance mechanisms in Tetranychus urticae strains from Greece. Combined bioassay, biochemical and synergistic data indicated that although P450 mono-oxygenase activities were associated with the trait, target site insensitivity was the major resistance component. A 3.3 kb cDNA fragment of the T. urticae para sodium channel gene encompassing segment 4 of domain II to segment 6 of domain IV was obtained by a degenerate PCR strategy. The T. urticae sequence showed highest identity (56%) to the scabies mite, Sarcoptes scabiei, and was phylogenetically classified within the divergent group of Arachnida. Comparison of resistant and susceptible strains identified the point mutation F1538I in segment 6 of domain III, which is known to confer strong resistance to pyrethroids, along with a second mutation (A1215D) in the intracellular linker connecting domains II and III with an unknown role. Three transcripts were identified corresponding to the k and l alternative exons. The mode of inheritance of resistance was confirmed as incompletely recessive, which is consistent with a target site mechanism for pyrethroids.
    Insect Molecular Biology 10/2009; 18(5):583-93. DOI:10.1111/j.1365-2583.2009.00900.x · 2.98 Impact Factor
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