title: A plant homolog of animal glutamate receptors is an ion channel gated by multiple hydrophobic amino acids.
abstract: Ionotropic glutamate receptors (iGluRs) are ligand-gated cation channels that mediate neurotransmission in animal nervous systems. Homologous proteins in plants have been implicated in root development, ion transport, and several metabolic and signaling pathways. AtGLR3.4, a plant iGluR homolog from Arabidopsis thaliana, has ion channel activity and is gated by asparagine, serine, and glycine. Using heterologous expression in Xenopus oocytes, we found that another Arabidopsis iGluR homolog, AtGLR1.4, functioned as a ligand-gated, nonselective, Ca(2+)-permeable cation channel that responded to an even broader range of amino acids, none of which are agonists of animal iGluRs. Seven of the 20 standard amino acids--mainly hydrophobic ones--acted as agonists, with methionine being most effective and most potent. Nine amino acids were antagonists, and four, including glutamate and glycine, had no effect on channel activity. We constructed a model of this previously uncharacterized ligand specificity and used knockout mutants to show that AtGLR1.4 accounts for methionine-induced membrane depolarization in Arabidopsis leaves.
authors.affiliation: Department of Biochemistry I-Receptor Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44780 Bochum, Germany. daniel.tapken@rub.de
authors.forename: Daniel
authors.initials: D
authors.lastname: Tapken
authors.forename: Uta
authors.initials: U
authors.lastname: Anschütz
authors.forename: Lai-Hua
authors.initials: LH
authors.lastname: Liu
authors.forename: Thomas
authors.initials: T
authors.lastname: Huelsken
authors.forename: Guiscard
authors.initials: G
authors.lastname: Seebohm
authors.forename: Dirk
authors.initials: D
authors.lastname: Becker
authors.forename: Michael
authors.initials: M
authors.lastname: Hollmann
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D015220:Calcium Channels / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018690:Excitatory Amino Acid Agonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D007473:Ion Channels / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008715:Methionine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D010802:Phylogeny; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D015220:Calcium Channels; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C585553:GLR1.4 protein, Arabidopsis; D007473:Ion Channels; D017470:Receptors, Glutamate; D049452:Green Fluorescent Proteins; D008715:Methionine