The antidepressant-sensitive dopamine transporter in Drosophila melanogaster: a primordial carrier for catecholamines.
Extracellular concentrations of monoamine neurotransmitters are regulated by a family of high-affinity transporters that are the molecular targets for such psychoactive drugs as cocaine, amphetamines, and therapeutic antidepressants. In Drosophila melanogaster, cocaine-induced behaviors show striking similarities to those induced in vertebrate animal models. Although a cocaine-sensitive serotonin carrier exists in flies, there has been no pharmacological or molecular evidence to support the presence of distinct carrier subtypes for other bioactive monoamines. Here we report the cloning and characterization of a cocaine-sensitive fly dopamine transporter (dDAT). In situ hybridization demonstrates that dDAT mRNA expression is restricted to dopaminergic cells in the fly nervous system. The substrate selectivity of dDAT parallels that of the mammalian DATs in that dopamine and tyramine are the preferred substrates, whereas octopamine is transported less efficiently, and serotonin not at all. In contrast, dDAT inhibitors display a rank order of potency most closely resembling that of mammalian norepinephrine transporters. Cocaine has a moderately high affinity to the cloned dDAT (IC50 = 2.6 microM). Voltage-clamp analysis of dDAT expressed in Xenopus laevis oocytes indicates that dDAT-mediated uptake is electrogenic; however, dDAT seems to lack the constitutive leak conductance that is characteristic of the mammalian catecholamine transporters. The combination of a DAT-like substrate selectivity and norepinephrine transporter-like inhibitor pharmacology within a single carrier, and results from phylogenetic analyses, suggest that dDAT represents an ancestral catecholamine transporter gene. The identification of a cocaine-sensitive target linked to dopaminergic neurotransmission in D. melanogaster will serve as a basis for further dissection of the genetic components of psychostimulant-mediated behavior.
Pörzgen
P
P
Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97201, USA. poerzgen@ohsu.edu
Park
S K
SK
Hirsh
J
J
Sonders
M S
MS
Amara
S G
SG
D000595:Amino Acid Sequence; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001692:Biological Transport; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D050482:Catecholamine Plasma Membrane Transport Proteins; D002395:Catecholamines / Q000493:pharmacokinetics*; D003042:Cocaine / Q000494:pharmacology; D018076:DNA, Complementary / Q000302:isolation & purification; D050483:Dopamine Plasma Membrane Transport Proteins; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004553:Electric Conductivity; D004594:Electrophysiology; D015870:Gene Expression; D016678:Genome; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D008657:Metabolic Clearance Rate; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry; D018377:Neurotransmitter Agents / Q000378:metabolism; D050484:Norepinephrine Plasma Membrane Transport Proteins; D009655:Octopamine / Q000493:pharmacokinetics; D009865:Oocytes; D010802:Phylogeny; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D027981:Symporters; D014162:Transfection; D014982:Xenopus laevis
D000928:Antidepressive Agents; D002352:Carrier Proteins; D050482:Catecholamine Plasma Membrane Transport Proteins; D002395:Catecholamines; C493211:DAT protein, Drosophila; D018076:DNA, Complementary; D050483:Dopamine Plasma Membrane Transport Proteins; D029721:Drosophila Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D050484:Norepinephrine Plasma Membrane Transport Proteins; D027981:Symporters; D009655:Octopamine; D020794:Receptor Protein-Tyrosine Kinases; D003042:Cocaine