title: Identification of amino acid residues in the insect sodium channel critical for pyrethroid binding.
abstract: The voltage-gated sodium channel is the primary target site of pyrethroids, which constitute a major class of insecticides used worldwide. Pyrethroids prolong the opening of sodium channels by inhibiting deactivation and inactivation. Despite numerous attempts to characterize pyrethroid binding to sodium channels in the past several decades, the molecular determinants of the pyrethroid binding site on the sodium channel remain elusive. Here, we show that an F-to-I substitution at 1519 (F1519I) in segment 6 of domain III (IIIS6) abolished the sensitivity of the cockroach sodium channel expressed in Xenopus laevis oocytes to all eight structurally diverse pyrethroids examined, including permethrin and deltamethrin. In contrast, substitution by tyrosine or tryptophan reduced the channel sensitivity to deltamethrin only by 3- to 10-fold, indicating that an aromatic residue at this position is critical for the interaction of pyrethroids with sodium channels. The F1519I mutation, however, did not alter the action of two other classes of sodium channel toxins, batrachotoxin (a site 2 toxin) and Lqhalpha-IT (a site 3 toxin). Schild analysis using competitive interaction of pyrethroid-stereospecific isomers demonstrated that the F1519W mutation and a previously known pyrethroid-resistance mutation, L993F in IIS6, reduced the binding affinity of 1S-cis-permethrin, an inactive isomer that shares the same binding site with the active isomer 1R-cis-permethrin. Our results provide the first direct proof that Leu993 and Phe1519 are part of the pyrethroid receptor site on an insect sodium channel.
authors.affiliation: Department of Entomology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Tan
authors.forename: Zhiqi
authors.initials: Z
authors.lastname: Liu
authors.forename: Ruiwu
authors.initials: R
authors.lastname: Wang
authors.forename: Zachary Y
authors.initials: ZY
authors.lastname: Huang
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Chen
authors.forename: Michael
authors.initials: M
authors.lastname: Gurevitz
authors.forename: Ke
authors.initials: K
authors.lastname: Dong
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D003058:Cockroaches; D004331:Drosophila melanogaster; D005260:Female; D007532:Isoleucine / Q000235:genetics; D007930:Leucine / Q000235:genetics; D009154:Mutation; D062550:NAV1.1 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010649:Phenylalanine / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D011722:Pyrethrins / Q000378:metabolism*; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000235:genetics
chemical_list: D062550:NAV1.1 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D011722:Pyrethrins; D015222:Sodium Channels; D007532:Isoleucine; D010649:Phenylalanine; D014364:Tryptophan; D007930:Leucine