Phenolamine-dependent adenylyl cyclase activation in Drosophila Schneider 2 cells

Drosophila Schneider 2 (S-2) cells are often employed as host cells for non -lyric, stable expression and functional characterization of mammalian and insect G-protein-coupled receptors (GPCRs), such as biogenic amine receptor s. In order to avoid cross-reactions, it is extremely important to know whi ch endogenous receptors are already present in the non-transfected S-2 cell s. Therefore, we analyzed cellular levels of cyclic AMP and Ca2+, important second messengers for intracellular signal transduction via GPCRs, in resp onse to a variety of naturally occurring biogenic amines, such as octopamin e, tyramine, serotonin, histamine, dopamine and melatonin. None of these am ines (up to 0.1 mM) was able to reduce forskolin-stimulated cyclic AMP prod uction in St cells. Furthermore, no agonist-induced calcium responses were observed. Nevertheless, the phenolamines octopamine (OA) and tyramine (TA) induced a dose-dependent increase of cyclic adenosine monophosphate (AMP) p roduction in S-2 cells, while serotonin, histamine, dopamine and melatonin (up to 0.1 mM) did not, The pharmacology of this response was similar to th at of the octopamine-2 (OA(2)) receptor type. In addition, this paper provi des evidence for the presence of an endogenous mRNA encoding an octopamine receptor type in these cells, which is identical or Very similar to OAMB. T his receptor was previously shown to be positively coupled to adenylyl cycl ase, (C) 2001 Elsevier Science Ltd. All rights reserved.