Amtyr1: Characterization of a gene from honeybee (Apis mellifera) brain encoding a functional tyramine receptor

Biogenic amine receptors are involved in the regulation and modulation of v arious physiological and behavioral processes in both vertebrates and inver tebrates. We have cloned a member of this gene family from the CNS of the h oneybee, Apis mellifera. The deduced amino acid sequence is homologous to t yramine receptors cloned from Locusta migratoria and Drosophila melanogaste r as well as to an octopamine receptor cloned from Heliothis virescens. Fun ctional properties of the honeybee receptor were studied in stably transfec ted human embryonic kidney 293 cells. Tyramine reduced forskolin-induced cy clic AMP production in a dose-dependent manner with an EC50 of similar to 1 30 nM. A similar effect of tyramine was observed in membrane homogenates of honeybee brains. Octopamine also reduced cyclic AMP production in the tran sfected cell line but was both less potent (EC50 of similar to 3 mu M) and less efficacious than tyramine. Receptor-encoding mRNA has a widespread dis tribution in the brain and subesophageal ganglion of the honeybee, suggesti ng that this tyramine receptor is involved in sensory signal processing as well as in higher-order brain functions.