A Drosophila dopamine 2-like receptor: Molecular characterization and identification of multiple alternatively spliced variants.
Dopamine is an important neurotransmitter in the central nervous system of both Drosophila and mammals. Despite the evolutionary distance, functional parallels exist between the fly and mammalian dopaminergic systems, with both playing roles in modulating locomotor activity, sexual function, and the response to drugs of abuse. In mammals, dopamine exerts its effects through either dopamine 1-like (D1-like) or D2-like G protein-coupled receptors. Although pharmacologic data suggest the presence of both receptor subtypes in insects, only cDNAs encoding D1-like proteins have been isolated previously. Here we report the cloning and characterization of a newly discovered Drosophila dopamine receptor. Sequence analysis reveals that this putative protein shares highest homology with known mammalian dopamine 2-like receptors. Eight isoforms of the Drosophila D2-like receptor (DD2R) transcript have been identified, each the result of alternative splicing. The encoded heptahelical receptors range in size from 461 to 606 aa, with variability in the length and sequence of the third intracellular loop. Pharmacologic assessment of three DD2R isoforms, DD2R-606, DD2R-506, and DD2R-461, revealed that among the endogenous biogenic amines, dopamine is most potent at each receptor. As established for mammalian D2-like receptors, stimulation of the Drosophila homologs with dopamine triggers pertussis toxin-sensitive Gi/o-mediated signaling. The D2-like receptor agonist, bromocriptine, has nanomolar potency at DD2R-606, -506, and -461, whereas multiple D2-like receptor antagonists (as established with mammalian receptors) have markedly reduced if any affinity when assessed at the fly receptor isoforms. The isolation of cDNAs encoding Drosophila D2-like receptors extends the range of apparent parallels between the dopaminergic system in flies and mammals. Pharmacologic and genetic manipulation of the DD2Rs will provide the opportunity to better define the physiologic role of these proteins in vivo and further explore the utility of invertebrates as a model system for understanding dopaminergic function in higher organisms.
Hearn
Mark G
MG
Molecular Pharmacology Research Center, Tupper Research Institute, Tufts-New England Medical Center, 750 Washington Street, Box 7703, Boston, MA 02111, USA.
Ren
Yong
Y
McBride
Edward W
EW
Reveillaud
Isabelle
I
Beinborn
Martin
M
Kopin
Alan S
AS
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004298:Dopamine / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D015870:Gene Expression; D014644:Genetic Variation; D016678:Genome; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2 / Q000235:genetics* / Q000378:metabolism; D015290:Second Messenger Systems; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D018492:Dopamine Antagonists; D029721:Drosophila Proteins; D044385:GTP-Binding Protein alpha Subunits; D008024:Ligands; D020033:Protein Isoforms; D012333:RNA, Messenger; D017448:Receptors, Dopamine D2; C468926:dopamine 2-like receptor, Drosophila; C084618:olfactory G protein subunit alpha olf; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins; D004298:Dopamine