title: Characterization of a ligand-gated cation channel based on an inositol receptor in the silkworm, Bombyx mori.
abstract: Insect herbivores recognize non-volatile compounds in plants to direct their feeding behavior. Gustatory receptors (Gr) appear to be required for nutrient recognition by gustatory organs in the mouthparts of insects. Gr10 is expressed in Bombyx mori (BmGr10) mouthparts such as maxillary galea, maxillary palp, and labrum. BmGr10 is predicted to function in sugar recognition; however, the precise biochemical function remains obscure. Larvae of B. mori are monophagous feeders able to find and feed on mulberry leaves. Soluble mulberry leaf extract contains sucrose, glucose, fructose, and myo-inositol. In this study, we identified BmGr10 as an inositol receptor using electrophysiological analysis with the Xenopus oocyte expression system and Ca(2+) imaging techniques using mammalian cells. These results demonstrated that Xenopus oocytes or HEK293T cells expressing BmGr10 specifically respond to myo-inositol and epi-inositol but do not respond to any mono-, di-, or tri-saccharides or to some sugar alcohols. These inositols caused Ca(2+) and Na(+) influxes into the cytoplasm independently of a G protein-mediated signaling cascade, indicating that BmGr10 is a ligand-gated cation channel. Overall, BmGr10 plays an important role in the myo-inositol recognition required for B. mori larval feeding behavior.
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kikuta
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Endo
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Natsuo
authors.initials: N
authors.lastname: Tomita
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Takada
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Morita
authors.affiliation: National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Asaoka
authors.affiliation: Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan. Electronic address: ryoichi@cc.tuat.ac.jp.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Sato
mesh_terms: D000818:Animals; D012831:Bombyx / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005247:Feeding Behavior; D057809:HEK293 Cells; D006801:Humans; D007294:Inositol / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008024:Ligands; D010802:Phylogeny; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism
chemical_list: D019476:Insect Proteins; D008024:Ligands; D011956:Receptors, Cell Surface; D007294:Inositol
keywords: Ca(2+) imaging; Gustatory receptor; Inositol; Mulberry leaf; Xenopus oocyte expression system