Cazzamali Giuseppe, Klaerke Dan A, Grimmelikhuijzen Cornelis J P
Department of Cell Biology and Comparative Zoology, Institute of Biology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
Biochem Biophys Res Commun. 2005 Dec 16;338(2):1189-96. doi: 10.1016/j.bbrc.2005.10.058. Epub 2005 Oct 21.
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.
果蝇基因组计划数据库包含一个名为CG7431的基因，注释为“无法分类的生物胺受体”。我们克隆了该基因并在中国仓鼠卵巢细胞中进行表达。在测试了各种G蛋白偶联受体的配体后，我们发现该受体被酪胺特异性激活（半数有效浓度[EC(50)]为5×10⁻⁷M），并且它与β-苯乙胺、章鱼胺、多巴、多巴胺、肾上腺素、去甲肾上腺素、色胺、5-羟色胺、组胺以及20种果蝇神经肽文库（所有测试浓度高达10⁻⁵或10⁻⁴M）均无交叉反应。该受体也在非洲爪蟾卵母细胞中表达，在那里它同样被酪胺特异性激活，EC(50)为3×10⁻⁷M。Northern印迹显示该受体在8小时龄的胚胎中就已表达，并且在随后的所有发育阶段持续表达。成年果蝇在头部和身体（胸部/腹部）部位均表达该受体。除了果蝇酪胺受体基因CG7431外，我们还发现了另一个与之密切相关的果蝇基因CG16766，它可能也编码一种酪胺受体。此外，我们在冈比亚疟蚊和蜜蜂的基因组数据库中注释了类似的酪胺样受体基因。这四种酪胺或酪胺样受体构成了一个新的受体家族，在系统发育上与先前鉴定的昆虫章鱼胺/酪胺受体不同。据我们所知，果蝇酪胺受体是第一个克隆的似乎对酪胺完全特异的昆虫G蛋白偶联受体。
