Distinct Molecular Recognition of Psychostimulants by Human andDrosophilaSerotonin Transporters

Abstract

In this study, human embryonic kidney (HEK)-293 cells stably expressing human, Drosophila, or a chimeric serotonin (5-hydroxytryptamine, 5-HT) transporter (hSERT, dSERT, , respectively) were used to explore the ability of two libraries of structurally distinct psychostimulants to inhibit 5-HT uptake. One library consisted of 3-phenyltropane analogs, whereas the second library consisted of several substituted amphetamines. hSERT exhibited a lower K i value for all the compounds in both libraries compared with dSERT, whereas the chimeric SERT exhibited properties more closely resembling those of dSERT. This species selectivity was explored using computer-generated comparative molecular field analysis to model the interactions of the cocaine analogs and substituted amphetamines at hSERT, dSERT, and the crossspecies chimera. Models for the 3-phenyltropane analogs indicate that a region exists around the aromatic ring where decreased electron density is favored, particularly for hSERT. This finding may indicate pi-pi stacking with an aromatic amino acid residue in SERT. Also, electronegative substituents in the 4Ј-position provide favorable interactions. This structural feature was demonstrated by increased potency of analogs with electronegative substituents on the aromatic ring that withdraw electron density. For the substituted amphetamines, key areas for interaction exist around the amine, an electrostatic component surrounding the 3-position on the aromatic ring, and a steric component surrounding the 4-position.

Structural determinants of species‐selective substrate recognition in human and Drosophila serotonin transporters revealed through computational docking studies

“…1,2 SERTs are targets of antidepressants and substances of abuse like cocaine and 3,4methyl-dioxy-methamphetamine, commonly known as "Ecstasy." 3 Hydropathy analyses initially suggested that SERTs are integral membrane proteins with 12 α-helices. 2,4,5 Sitedirected mutagenesis and substituted cysteine accessibility method (SCAM) experiments on putative transmembrane TMs and loops have supported this proposal.…”

“…Several studies have identified amino acid sequence differences among SERT species that confer alternate specificities for substrates and inhibitors. 3,[12][13][14] Barker et al 15 used human SERT (hSERT) and Drosophila SERT (dSERT) chimeras to implicate Y95 in forming part of the recognition site for citalopram and mazindol, two biogenic amine reuptake inhibitors. Adkins et al 14 used the same approach to show the Y95F hSERT mutant exhibits dSERT-like recognition of N-isopropyl tryptamine.…”

Early 18F‐labeled fluoro‐2‐deoxy‐D‐glucose positron emission tomography scanning in the lymphomas

“…As members of the sodium and chloride‐dependent neurotransmitter transporter gene family, serotonin (5‐HT) transporters (SERTs) carry out the uptake of 5‐HT across plasma membranes in the central nervous system, peripheral nervous system, placenta, platelets, and pulmonary system 1, 2. SERTs are targets of antidepressants and substances of abuse like cocaine and 3,4‐methyldioxy‐methamphetamine, commonly known as “Ecstasy.”3 Hydropathy analyses initially suggested that SERTs are integral membrane proteins with 12 α‐helices 2, 4, 5. Site‐directed mutagenesis and substituted cysteine accessibility method (SCAM) experiments on putative transmembrane TMs and loops have supported this proposal 6–10…”

“…implicated I172 and I176 in substrate and inhibitor binding through protection of transporter function from inactivation by methanethiosulfonate reagents (MTS) in cysteine mutants of these residues. Several studies have identified amino acid sequence differences among SERT species that confer alternate specificities for substrates and inhibitors 3, 12–14. Barker et al 15.…”

Inflammatory pain in the rabbit: A new, efficient method for measuring mechanical hyperalgesia in the hind paw

“…Class 2 GPCRs in this category include the CGRP 1 (Hershey et al, 2005;Mallee et al, 2002), glucagon-like peptide 1 (GLP 1 ) receptor (Tibaduiza et al, 2001) and VIP/PACAP receptor VPAC 1 (Couvineau et al, 1996). The vanilloid receptor TRPV 1 (Valenzano and Sun, 2004), serotonin transporter SERT (Barker et al, 1994;Roman et al, 2004) and the kinase porphobilinogen synthase (Kervinen et al, 2001) are examples of ion channels, transporters and kinases, respectively, that show species differences in pharmacology. Several of the targets described above have been implicated in pain transmission/sensitization/modulation.…”