title: Okaramine insecticidal alkaloids show similar activity on both exon 3c and exon 3b variants of glutamate-gated chloride channels of the larval silkworm, Bombyx mori.
abstract: The okaramine indole alkaloids were recently shown to be more selective than ivermectin in activating the glutamate-gated chloride channels of the silkworm larvae of Bombyx mori (BmGluCls). Those studies were carried out using the exon 3b variant as a representative of BmGluCls. However, it remains unknown whether okaramines are similarly effective on other silkworm GluCl variants and whether they share the same binding site as ivermectin on GluCls. To begin to address these questions, we examined the potency of four okaramines on the exon 3c variant of BmGluCls by two-electrode voltage clamp voltage recordings of glutamate-induced chloride currents. The potency of okaramines in activating the exon 3c BmGluCl agreed well with findings on the exon 3b BmGluCl and insecticidal potency. Okaramine B (10μM) reduced the maximum binding (Bmax) but not the dissociation constant (KD) of [3H]ivermectin in studies on plasma membrane fractions of HEK293 cells expressing the exon 3c variant. These findings indicate that activation of GluCls is important in the insecticidal actions of okaramines.
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Furutani
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ihara
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-chou, Naka-ku, Sakai, Osaka 599-8531, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kai
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: UCL Respiratory, Division of Medicine, University College London, The Rayne Building, 5 University Street, London WC1E 6JF, UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Sattelle
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-chou, Naka-ku, Sakai, Osaka 599-8531, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Hayashi
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan. Electronic address: kmatsuda@nara.kindai.ac.jp.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D001384:Azetidines / Q000494:pharmacology*; D001392:Azocines / Q000494:pharmacology*; D012831:Bombyx; D018118:Chloride Channels / Q000235:genetics* / Q000502:physiology*; D005091:Exons; D057809:HEK293 Cells; D006801:Humans; D026121:Indole Alkaloids / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D007559:Ivermectin / Q000494:pharmacology; D007814:Larva / Q000187:drug effects / Q000502:physiology
chemical_list: D001384:Azetidines; D001392:Azocines; D018118:Chloride Channels; D026121:Indole Alkaloids; D007306:Insecticides; C109777:glutamate-gated chloride channels; C416703:okaramine B; C501539:okaramine C; D007559:Ivermectin
keywords: Binding assay; Glutamate-gated chloride channels; Ivermectin; Okaramines; Silkworm (Bombyx mori); Voltage-clamp electrophysiology