title: Distinct recognition of substrates by the human and Drosophila serotonin transporters.
abstract: The human and Drosophila serotonin transporters (hSERT and dSERT, respectively) were used to explore differences in substrate properties. hSERT and dSERT showed similar Km values for 5-hydroxytryptamine (5-HT; serotonin) transport (1.2 and 0.9 micro M, respectively), suggesting similar recognition of 5-HT by the two species variants. Although dSERT cell surface expression was approximately 8-fold lower than that of hSERT, dSERT does appear to have a 2-fold faster turnover number for inward transport of 5-HT. Interestingly, another substrate, N-methyl-4-phenylpyridinium (MPP+), was transported only by hSERT. However, MPP+ inhibited 5-HT uptake in both species variants with similar potencies. Two cross-species chimeras, H1-118D119-627 and H1-281D282-476H477-638, were also unable to transport MPP+, implicating the role of transmembrane domains V to IX in the substrate permeation pathway. Based on exchange experiments, certain substituted-amphetamines also appear to be poor substrates at dSERT. Two-electrode voltage-clamp studies in oocytes confirmed that the amphetamines do not possess substrate-like properties for dSERT. Our data suggest distinct molecular recognition among SERT substrate classes that influence translocation mechanisms.
authors.affiliation: Department of Medical Chemistry and Molecular Phamacology, Pudue University School of Pharmacy, I575 Stadium Mall Dr., West Lafayette IN, 47907-2091, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Rodríguez
authors.forename: D L
authors.initials: DL
authors.lastname: Roman
authors.forename: K J
authors.initials: KJ
authors.lastname: White
authors.forename: D E
authors.initials: DE
authors.lastname: Nichols
authors.forename: E L
authors.initials: EL
authors.lastname: Barker
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000493:pharmacokinetics; D000661:Amphetamine / Q000493:pharmacokinetics; D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D015259:Dopamine Agents / Q000493:pharmacokinetics; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins; D013045:Species Specificity
chemical_list: D002352:Carrier Proteins; D015259:Dopamine Agents; D029721:Drosophila Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C493230:SLC6A4 protein, human; C493233:SerT protein, Drosophila; D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin; D000661:Amphetamine; D015655:1-Methyl-4-phenylpyridinium