Ivermectin and nodulisporic acid receptors in Drosophila melanogaster contain both gamma-aminobutyric acid-gated Rdl and glutamate-gated GluCl alpha chloride channel subunits.
35S-labeled derivatives of the insecticides nodulisporic acid and ivermectin were synthesized and demonstrated to bind with high affinity to a population of receptors in Drosophila head membranes that were previously shown to be associated with a glutamate-gated chloride channel. Nodulisporic acid binding was modeled as binding to a single population of receptors. Ivermectin binding was composed of at least two kinetically distinct receptor populations, only one of which was associated with nodulisporic acid binding. The binding of these two ligands was modulated by glutamate, ivermectin, and antagonists of invertebrate gamma-aminobutyric acid (GABA)ergic receptors. Because solubilized nodulisporic acid and ivermectin receptors comigrated as 230-kDa complexes by gel filtration, antisera specific for both the Drosophila glutamate-gated chloride channel subunit GluCl alpha (DmGluCl alpha) and the GABA-gated chloride channel subunit Rdl (DmRdl) proteins were generated and used to examine the possible coassembly of these two subunits within a single receptor complex. DmGluCl alpha antibodies immunoprecipitated all of the ivermectin and nodulisporic acid receptors solubilized by detergent from Drosophila head membranes. DmRdl antibodies also immunoprecipitated all solubilized nodulisporic receptors, but only approximately 70% of the ivermectin receptors. These data suggest that both DmGluCl alpha and DmRdl are components of nodulisporic acid and ivermectin receptors, and that there also exists a distinct class of ivermectin receptors that contains the DmGluCl alpha subunit but not the DmRdl subunit. This co-association of DmGluCl alpha and DmRdl represents the first biochemical and immunological evidence of coassembly of subunits from two different subclasses of ligand-gated ion channel subunits.
Ludmerer
Steven W
SW
Department of Parasite Biochemistry and Molecular Biology, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Warren
Vivien A
VA
Williams
Brande S
BS
Zheng
Yingcong
Y
Hunt
David C
DC
Ayer
Michelle B
MB
Wallace
Michael A
MA
Chaudhary
Ashok G
AG
Egan
Marjorie A
MA
Meinke
Peter T
PT
Dean
Dennis C
DC
Garcia
Maria L
ML
Cully
Doris F
DF
Smith
McHardy M
MM
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000378:metabolism*; D029721:Drosophila Proteins / Q000737:chemistry / Q000502:physiology*; D004331:Drosophila melanogaster; D018698:Glutamic Acid / Q000502:physiology*; D007106:Immune Sera / Q000378:metabolism; D007211:Indoles / Q000378:metabolism*; D015640:Ion Channel Gating; D007559:Ivermectin / Q000378:metabolism*; D011233:Precipitin Tests; D011869:Radioligand Assay; D011955:Receptors, Drug / Q000276:immunology / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000502:physiology*; D012995:Solubility; D013462:Sulfur Radioisotopes / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018118:Chloride Channels; D029721:Drosophila Proteins; D007106:Immune Sera; D007211:Indoles; C410124:N-2-hydroxyethyl-2,2-nodulisporamide N amide; C082030:Rdl protein, Drosophila; D011955:Receptors, Drug; D011963:Receptors, GABA-A; D013462:Sulfur Radioisotopes; C109777:glutamate-gated chloride channels; C110703:nodulisporic acid A; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D007559:Ivermectin