A single amino acid residue controls Ca2+ signaling by an octopamine receptor from Drosophila melanogaster

Rhythmic activity of cells and cellular networks plays an important role in physiology. In the nervous system oscillations of electrical activity and/or second messenger concentrations are important to synchronize neuronal activity. At the molecular level, rhythmic activity can be initiated by different routes. We have recently shown that an octopamine-activated G-protein-coupled receptor (GPCR; DmOct alpha 1Rb, CG3856) from Drosophila initiates Ca2+ oscillations. Here, we have unraveled the molecular basis of cellular Ca2+ signaling controlled by the DmOct alpha 1Rb receptor using a combination of pharmacological intervention, site-directed mutagenesis, and functional cellular Ca2+ imaging on heterologously expressed receptors. Phosphorylation of a single amino acid residue in the third intracellular loop of the GPCR by PKC is necessary and sufficient to desensitize the receptor. From its desensitized state, DmOct alpha 1Rb is resensitized by dephosphorylation, and a new Ca2+ signal occurs on octopamine stimulation. Our findings show that transient changes of the receptor's surface profile have a strong effect on its physiological signaling properties. We expect that the detailed knowledge of DmOct alpha 1Rb-dependent signal transduction fosters the identification of specific drugs that can be used for GPCR-mediated pest control, since octopamine serves important physiological and behavioral functions in arthropods.-Hoff M., Balfanz, S., Ehling, P., Gensch, T., Baumann, A. A single amino acid residue controls Ca2+ signaling by an octopamine receptor from Drosophila melanogaster. FASEB J. 25, 2484-2491 (2011). www.fasebj.org