Cloning and Functional Characterization of a Novel Dopamine Receptor fromDrosophila melanogaster

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Abstract
A cDNA clone is described that encodes a novel G-protein-coupled dopamine receptor (DopR99B) expressed inDrosophilaheads. The DopR99B receptor maps to 99B3–5, close to the position of the octopamine/tyramine receptor gene at 99A10–B1, suggesting that the two may be related through a gene duplication. Agonist stimulation of DopR99B receptors expressed inXenopusoocytes increased intracellular Ca2+levels monitored as changes in an endogenous inward Ca2+-dependent chloride current. In addition to initiating this intracellular Ca2+signal, stimulation of DopR99B increased cAMP levels. The rank order of potency of agonists in stimulating the chloride current is: dopamine > norepinephrine > epinephrine > tyramine. Octopamine and 5-hydroxytryptamine are not active (Drosophilareceptor defines a novel structural class of dopamine receptors. Because DopR99B is the second dopamine receptor cloned fromDrosophila, this work establishes dopamine receptor diversity in a system amenable to genetic dissection.