Distinct Recognition of Substrates by the Human and Drosophila Serotonin Transporters

• Published in: The Journal of pharmacology and experimental therapeutics 2003-07, Vol.306 (1), p.338-346
• Main Authors: Rodríguez, G J, Roman, D L, White, K J, Nichols, D E, Barker, E L
• Format: Article
• Language: English
• Subjects: 1-Methyl-4-phenylpyridinium - pharmacokinetics; Amphetamine - pharmacokinetics; Animals; Biological Transport; Carrier Proteins - metabolism; Cell Line; Dopamine Agents - pharmacokinetics; Drosophila - metabolism; Drosophila Proteins; Humans; Membrane Glycoproteins - metabolism; Membrane Transport Proteins; Nerve Tissue Proteins; Recombinant Fusion Proteins - metabolism; Serotonin - metabolism; Serotonin Plasma Membrane Transport Proteins; Species Specificity
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.103.048751

The human and Drosophila serotonin transporters (hSERT and dSERT, respectively) were used to explore differences in substrate properties. hSERT and dSERT showed similar K m values for 5-hydroxytryptamine (5-HT; serotonin) transport (1.2 and 0.9 μM, 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, H 1–118 D 119–627 and H 1–281 D 282–476 H 477–638 , 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.