title: Amino acid residues of both the extracellular and transmembrane domains influence binding of the antiparasitic agent milbemycin to Haemonchus contortus AVR-14B glutamate-gated chloride channels.
abstract: Glutamate-gated chloride (GluCl) channels are pentameric receptors for the inhibitory neurotransmitter glutamate in invertebrates and are a major target for macrolide anthelmintics. Three amino acids in GluCl channels are reported to render macrolide resistance in nematodes and insects. To examine whether these three amino acids are involved in binding of the antiparasitic agent milbemycin (MLM) to the GluCl channels of the nematode parasite Haemonchus contortus, the equivalent amino acids (L256, P316, and G329) of the Hco-AVR-14B subunit were substituted with various amino acids. cDNAs encoding the wild type and mutants of this subunit were transfected into COS-1 cells for transient expression and analysis of GluCl channels. The abilities of these mutant channels to bind [(3)H]MLM A(4) were remarkably decreased when compared with the wild-type channel. In patch clamp analysis, L256F and P316S mutant channels were 37- and 100-fold less sensitive to MLM A(4) when compared with the wild-type channel, respectively. These findings indicate that amino acid changes in the β10 strand, the M2-M3 linker, and the M3 region influence MLM A(4) binding to the channel. Homology modeling and ligand docking studies suggest the presence of two potential binding sites for MLM A(4).
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue, Japan.
authors.forename: Mao
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Matsuda
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Ozoe
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Ozoe
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000235:genetics; D000818:Animals; D000977:Antiparasitic Agents / Q000737:chemistry*; D001665:Binding Sites; D019556:COS Cells; D018118:Chloride Channels / Q000737:chemistry* / Q000235:genetics; D002522:Chlorocebus aethiops; D006189:Haemonchus; D018942:Macrolides / Q000737:chemistry; D018408:Patch-Clamp Techniques; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D000596:Amino Acids; D000977:Antiparasitic Agents; D018118:Chloride Channels; D018942:Macrolides; C109777:glutamate-gated chloride channels; C027837:moxidectin