Cloning and Functional Expression of the First Drosophila melanogaster Sulfakinin Receptor DSK-R1

Abstract Described in this report is a successful cloning and characterization of a functionally active Drosophila sulfakinin receptor designated DSK-R1. When expressed in mammalian cells, DSK-R1 was activated by a sulfated, Met 7 →Leu 7 -substituted analog of drosulfakinin-1, FDDY(SO 3 H)GHLRF-NH 2 ([Leu 7 ]-DSK-1S). The interaction of [Leu 7 ]-DSK-1S with DSK-R1 led to a dose-dependent intracellular calcium increase with an EC 50 in the low nanomolar range. The observed Ca 2+ signal predominantly resulted from activation of pertussis toxin (PTX)-insensitive signaling pathways pointing most likely to G q/11 involvement in coupling to the activated receptor. The unsulfated [Leu 7 ]-DSK-1 was ca. 3000-fold less potent than its sulfated counterpart which stresses the importance of the sulfate moiety for the biological activity of drosulfakinin. The DSK-R1 was specific for the insect sulfakinin since two related vertebrate sulfated peptides, human CCK-8 and gastrin-II, were found inactive when tested at concentrations up to 10 −5 M. To our knowledge, the cloned DSK-R1 receptor is the first functionally active Drosophila sulfakinin receptor reported to date.