A new family of insect tyramine receptors.
The Drosophila Genome Project database contains a gene, CG7431, annotated to be an "unclassifiable biogenic amine receptor." We have cloned this gene and expressed it in Chinese hamster ovary cells. After testing various ligands for G protein-coupled receptors, we found that the receptor was specifically activated by tyramine (EC(50), 5x10(-7)M) and that it showed no cross-reactivity with beta-phenylethylamine, octopamine, dopa, dopamine, adrenaline, noradrenaline, tryptamine, serotonin, histamine, and a library of 20 Drosophila neuropeptides (all tested in concentrations up to 10(-5) or 10(-4)M). The receptor was also expressed in Xenopus oocytes, where it was, again, specifically activated by tyramine with an EC(50) of 3x10(-7)M. Northern blots showed that the receptor is already expressed in 8-hour-old embryos and that it continues to be expressed in all subsequent developmental stages. Adult flies express the receptor both in the head and body (thorax/abdomen) parts. In addition to the Drosophila tyramine receptor gene, CG7431, we found another closely related Drosophila gene, CG16766, that probably also codes for a tyramine receptor. Furthermore, we annotated similar tyramine-like receptor genes in the genomic databases from the malaria mosquito Anopheles gambiae and the honeybee Apis mellifera. These four tyramine or tyramine-like receptors constitute a new receptor family that is phylogenetically distinct from the previously identified insect octopamine/tyramine receptors. The Drosophila tyramine receptor is, to our knowledge, the first cloned insect G protein-coupled receptor that appears to be fully specific for tyramine.
Cazzamali
Giuseppe
G
Department of Cell Biology and Comparative Zoology, Institute of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
Klaerke
Dan A
DA
Grimmelikhuijzen
Cornelis J P
CJ
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D017124:Conserved Sequence; D006224:Cricetinae; D003412:Cricetulus; D004331:Drosophila melanogaster / Q000378:metabolism*; D007313:Insecta; D008969:Molecular Sequence Data; D017982:Receptors, Biogenic Amine / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014439:Tyramine / Q000378:metabolism*
D017982:Receptors, Biogenic Amine; C066175:tyramine receptor; D014439:Tyramine