title: A primordial dopamine D1-like adenylyl cyclase-linked receptor from Drosophila melanogaster displaying poor affinity for benzazepines.
abstract: We report here the isolation from Drosophila melanogaster of a 2.0 kb cDNA clone encoding a 385 amino acid protein (dDA1) displaying, within putative transmembrane domains, highest amino acid sequence homology (49-53%) to members of the vertebrate dopamine D1-like receptor family. When expressed in either Sf9 or COS-7 cells, dDA1 did not bind the specific D1-like receptor antagonist [3H]SCH-23390 or numerous other dopaminergic, adrenergic or serotoninergic ligands with high affinity. However, like vertebrate dopamine D1-like receptors, dDA1 stimulated the accumulation of cAMP in response to DA (EC50 approximately 300 nM) and 6,7-ADTN (EC50 approximately 500 nM). The dopaminergic rank order of potency (DA > NE >> 5-HT) and the lack of stimulation by other possible neurotransmitters (octopamine, tyramine, tryptamine) or DA metabolites (e.g. N-acetyl dopamine) found in Drosophila suggests that this receptor functionally belongs to the dopamine D1-like subfamily. Benzazepines, which characteristically bind to vertebrate dopamine D1-like receptors with high affinity, were relatively poor in stimulating (SKF-38393, SKF-82526; EC50 > 10 microM) dDA1-mediated accumulation of cAMP. Of the numerous compounds tested, a few dopaminergic antagonists inhibited DA-stimulated production of cAMP in a concentration-dependent manner, albeit with considerably reduced affinity, and with the rank order of potency: (+)-butaclamol(Kb approximately 125nM) > SCH-23390(Kb approximately 230nM) > alpha-flupenthixol (Kb approximately 400 nM) > chlorpromazine > or = spiperone (Kb approximately 680 nM) > or = clozapine. In situ hybridization revealed that dDA1 receptor mRNA is expressed as a maternal transcript, and at later blastoderm stages is restricted to apical regions of the cortical peripheral cytoplasm. The generation of inter-species D1 receptor chimeras may help to identify those particular sequence-specific motifs or amino acid residues conferring high affinity benzaepine receptor interactions.
authors.affiliation: Department of Psychiatry, University of Toronto, Ont., Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Sugamori
authors.forename: L L
authors.initials: LL
authors.lastname: Demchyshyn
authors.forename: F
authors.initials: F
authors.lastname: McConkey
authors.forename: M A
authors.initials: MA
authors.lastname: Forte
authors.forename: H B
authors.initials: HB
authors.lastname: Niznik
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001552:Benzazepines / Q000378:metabolism*; D017124:Conserved Sequence; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000737:chemistry*; D019204:GTP-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009638:Norepinephrine / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D017385:Sequence Homology; D012701:Serotonin / Q000494:pharmacology; D018411:Spodoptera / Q000378:metabolism; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014162:Transfection
chemical_list: D001552:Benzazepines; C093147:Dop1R1 protein, Drosophila; D029721:Drosophila Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D013764:Tetrahydronaphthalenes; D012701:Serotonin; C011639:ADTN; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D004298:Dopamine; D009638:Norepinephrine