Functional analysis of Caenorhabditis elegans glutamate receptor subunits by domain transplantation.
Glutamate receptors are not only abundant and important mediators of fast excitatory synaptic transmission in vertebrates, but they also serve a similar function in invertebrates such as Drosophila and the nematode Caenorhabditis elegans. In C. elegans, an animal with only 302 neurons, 10 different glutamate receptor subunits have been identified and cloned. To study the ion channel properties of these receptor subunits, we recorded glutamate-gated currents from Xenopus oocytes that expressed either C. elegans glutamate receptor subunits or chimeric rat/C. elegans glutamate receptor subunits. The chimeras were constructed between the C. elegans glutamate receptor pore domains and either the rat kainate receptor subunit GluR6, the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunit GluR1, or the N-methyl-d-aspartate (NMDA) receptor subunit NMDAR1-1a. Although native subunits were nonfunctional, 9 of 10 ion pores were found to conduct current upon transplantation into rat receptor subunits. A provisional classification of the C. elegans glutamate receptor subunits was attempted based on functionality of the chimeras. C. elegans glutamate receptor ion pores, at a position homologous to a highly conserved site critical for ion permeation properties in vertebrate glutamate receptor pores, contain amino acids not found in vertebrate glutamate receptors. We show that the pore-constricting Q/R site, which in vertebrate receptors determines calcium permeability and rectification properties of the ion channel, in C. elegans can be occupied by other amino acids, including, surprisingly, lysine and proline, without loss of these properties.
Strutz-Seebohm
Nathalie
N
Department of Biochemistry I, Receptor Biochemistry, Ruhr University Bochum, Bochum D-44780, Germany.
Werner
Markus
M
Madsen
David M
DM
Seebohm
Guiscard
G
Zheng
Yi
Y
Walker
Craig S
CS
Maricq
Andres V
AV
Hollmann
Michael
M
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D005260:Female; D015870:Gene Expression; D018698:Glutamic Acid / Q000494:pharmacology; D006801:Humans; D006860:Hydrogen Bonding; D007473:Ion Channels / Q000502:physiology; D007608:Kainic Acid / Q000494:pharmacology; D007668:Kidney; D008564:Membrane Potentials; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000502:physiology / Q000648:ultrastructure; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D051381:Rats; D018091:Receptors, AMPA / Q000235:genetics; D017470:Receptors, Glutamate / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D018092:Kainic Acid Receptors / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D014162:Transfection; D014982:Xenopus laevis; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D029742:Caenorhabditis elegans Proteins; D004533:Egtazic Acid; D018698:Glutamic Acid; D007473:Ion Channels; D007608:Kainic Acid; D021122:Protein Subunits; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid