Phthalic acid diamides activate ryanodine-sensitive Ca2+ release channels in insects.
Flubendiamide represents a novel chemical family of substituted phthalic acid diamides with potent insecticidal activity. So far, the molecular target and the mechanism of action were not known. Here we present for the first time evidence that phthalic acid diamides activate ryanodine-sensitive intracellular calcium release channels (ryanodine receptors, RyR) in insects. With Ca(2+) measurements, we showed that flubendiamide and related compounds induced ryanodine-sensitive cytosolic calcium transients that were independent of the extracellular calcium concentration in isolated neurons from the pest insect Heliothis virescens as well as in transfected CHO cells expressing the ryanodine receptor from Drosophila melanogaster. Binding studies on microsomal membranes from Heliothis flight muscles revealed that flubendiamide and related compounds interacted with a site distinct from the ryanodine binding site and disrupted the calcium regulation of ryanodine binding by an allosteric mechanism. This novel insecticide mode of action seems to be restricted to specific RyR subtypes because the phthalic acid diamides reported here had almost no effect on mammalian type 1 ryanodine receptors.
Ebbinghaus-Kintscher
Ulrich
U
Bayer CropScience AG, Alfred-Nobel-Strasse 50, D-40789 Monheim, Germany. ulrich.ebbinghaus-kintscher@bayercropscience.com
Luemmen
Peter
P
Lobitz
Nicole
N
Schulte
Thomas
T
Funke
Christian
C
Fischer
Rüdiger
R
Masaki
Takao
T
Yasokawa
Noriaki
N
Tohnishi
Masanori
M
D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D016466:CHO Cells; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D003958:Diamide / Q000494:pharmacology*; D004331:Drosophila melanogaster; D016257:Fura-2; D007425:Intracellular Membranes / Q000737:chemistry; D047028:Macrocyclic Compounds; D051379:Mice; D008856:Microscopy, Fluorescence; D009036:Moths / Q000378:metabolism*; D009132:Muscles / Q000737:chemistry / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010080:Oxazoles / Q000494:pharmacology; D012433:Ryanodine / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology; D014162:Transfection; D005466:Fluorocarbons; D010797:Phthalimides
D001549:Benzamides; D002110:Caffeine; D002118:Calcium; D003958:Diamide; D016257:Fura-2; D047028:Macrocyclic Compounds; D010080:Oxazoles; D012433:Ryanodine; D019837:Ryanodine Receptor Calcium Release Channel; D013450:Sulfones; C108644:xestospongin A; C508762:flubendiamide; D005466:Fluorocarbons; D010797:Phthalimides