The binding sites for benztropines and dopamine in the dopamine transporter overlap

TY - JOUR

T1 - The binding sites for benztropines and dopamine in the dopamine transporter overlap

AU - Jensen, Heidi Bisgaard

AU - Larsen, M Andreas B

AU - Mazier, Sonia

AU - Beuming, Thijs

AU - Weinstein, Harel

AU - Shi, Lei

AU - Løland, Claus Juul

AU - Gether, Ulrik

N1 - Copyright © 2010 Elsevier Ltd. All rights reserved.

PY - 2011/1/1

Y1 - 2011/1/1

N2 - Analogs of benztropines (BZTs) are potent inhibitors of the dopamine transporter (DAT) but are less effective than cocaine as behavioral stimulants. As a result, there have been efforts to evaluate these compounds as leads for potential medication for cocaine addiction. Here we use computational modeling together with site-directed mutagenesis to characterize the binding site for BZTs in DAT. Docking into molecular models based on the structure of the bacterial homolog LeuT supported a BZT binding site that overlaps with the substrate-binding pocket. In agreement, mutations of residues within the pocket, including22Number in superscript describes residue number according to generic numbering scheme (see Materials and Methods). Val1523.46 to Ala or Ile, Ser4228.60 to Ala and Asn1573.51 to Cys or Ala, resulted in decreased affinity for BZT and the analog JHW007, as assessed in [3H]dopamine uptake inhibition assays and/or [3H]CFT competition binding assay. A putative polar interaction of one of the phenyl ring fluorine substituents in JHW007 with Asn1573.51 was used as a criterion for determining likely binding poses and establish a structural context for the mutagenesis findings. The analysis positioned the other fluorine-substituted phenyl ring of JHW007 in close proximity to Ala47910.51/Ala48010.52 in transmembrane segment (TM) 10. The lack of such an interaction for BZT led to a more tilted orientation, as compared to JHW007, bringing one of the phenyl rings even closer to Ala47910.51/Ala48010.52. Mutation of Ala47910.51 and Ala48010.52 to valines supported these predictions with a larger decrease in the affinity for BZT than for JHW007. Summarized, our data suggest that BZTs display a classical competitive binding mode with binding sites overlapping those of cocaine and dopamine.

AB - Analogs of benztropines (BZTs) are potent inhibitors of the dopamine transporter (DAT) but are less effective than cocaine as behavioral stimulants. As a result, there have been efforts to evaluate these compounds as leads for potential medication for cocaine addiction. Here we use computational modeling together with site-directed mutagenesis to characterize the binding site for BZTs in DAT. Docking into molecular models based on the structure of the bacterial homolog LeuT supported a BZT binding site that overlaps with the substrate-binding pocket. In agreement, mutations of residues within the pocket, including22Number in superscript describes residue number according to generic numbering scheme (see Materials and Methods). Val1523.46 to Ala or Ile, Ser4228.60 to Ala and Asn1573.51 to Cys or Ala, resulted in decreased affinity for BZT and the analog JHW007, as assessed in [3H]dopamine uptake inhibition assays and/or [3H]CFT competition binding assay. A putative polar interaction of one of the phenyl ring fluorine substituents in JHW007 with Asn1573.51 was used as a criterion for determining likely binding poses and establish a structural context for the mutagenesis findings. The analysis positioned the other fluorine-substituted phenyl ring of JHW007 in close proximity to Ala47910.51/Ala48010.52 in transmembrane segment (TM) 10. The lack of such an interaction for BZT led to a more tilted orientation, as compared to JHW007, bringing one of the phenyl rings even closer to Ala47910.51/Ala48010.52. Mutation of Ala47910.51 and Ala48010.52 to valines supported these predictions with a larger decrease in the affinity for BZT than for JHW007. Summarized, our data suggest that BZTs display a classical competitive binding mode with binding sites overlapping those of cocaine and dopamine.

KW - Animals

KW - Benztropine

KW - Binding Sites

KW - COS Cells

KW - Cercopithecus aethiops

KW - Cocaine

KW - Dopamine

KW - Dopamine Plasma Membrane Transport Proteins

KW - Models, Molecular

KW - Structure-Activity Relationship

U2 - 10.1016/j.neuropharm.2010.08.021

DO - 10.1016/j.neuropharm.2010.08.021

M3 - Journal article

C2 - 20816875

SN - 0028-3908

VL - 60

SP - 182

EP - 190

JO - Neuropharmacology

JF - Neuropharmacology

IS - 1

ER -