Identification of the benztropine analog [125I]GA II 34 binding site on the human dopamine transporter

Michael J. Tomlinson, Danielle Krout, Akula Bala Pramod, John R. Lever, Amy Hauck Newman, L. Keith Henry, Roxanne A. Vaughan

Research output: Contribution to journalArticle

Abstract

The dopamine transporter (DAT) is a neuronal membrane protein that is responsible for reuptake of dopamine (DA) from the synapse and functions as a major determinant in control of DA neurotransmission. Cocaine and many psychostimulant drugs bind to DAT and block reuptake, inducing DA overflow that forms the neurochemical basis for euphoria and addiction. Paradoxically, however, some ligands such as benztropine (BZT) bind to DAT and inhibit reuptake but do not produce these effects, and it has been hypothesized that differential mechanisms of binding may stabilize specific transporter conformations that affect downstream neurochemical or behavioral outcomes. To investigate the binding mechanisms of BZT on DAT we used the photoaffinity BZT analog [125I]N-[n-butyl-4-(4‴-azido-3‴-iodophenyl)]-4′,4″-difluoro-3α-(diphenylmethoxy)tropane ([125I]GA II 34) to identify the site of cross-linking and predict the binding pose relative to that of previously-examined cocaine photoaffinity analogs. Biochemical findings show that adduction of [125I]GA II 34 occurs at residues Asp79 or Leu80 in TM1, with molecular modeling supporting adduction to Leu80 and a pharmacophore pose in the central S1 site similar to that of cocaine and cocaine analogs. Substituted cysteine accessibility method protection analyses verified these findings, but identified some differences in structural stabilization relative to cocaine that may relate to BZT neurochemical outcomes.

Original languageEnglish (US)
JournalNeurochemistry International
DOIs
StateAccepted/In press - Jan 1 2018
Externally publishedYes

Fingerprint

Benztropine
Dopamine Plasma Membrane Transport Proteins
Cocaine
Binding Sites
Dopamine
Tropanes
Synaptic Transmission
Synapses
Cysteine
Membrane Proteins
Ligands
Pharmaceutical Preparations

Keywords

  • Benztropine
  • Cocaine
  • Molecular modeling
  • Peptide mapping
  • Photoaffinity labeling
  • SCAM

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Cell Biology

Cite this

Identification of the benztropine analog [125I]GA II 34 binding site on the human dopamine transporter. / Tomlinson, Michael J.; Krout, Danielle; Pramod, Akula Bala; Lever, John R.; Newman, Amy Hauck; Henry, L. Keith; Vaughan, Roxanne A.

In: Neurochemistry International, 01.01.2018.

Research output: Contribution to journalArticle

Tomlinson, Michael J. ; Krout, Danielle ; Pramod, Akula Bala ; Lever, John R. ; Newman, Amy Hauck ; Henry, L. Keith ; Vaughan, Roxanne A. / Identification of the benztropine analog [125I]GA II 34 binding site on the human dopamine transporter. In: Neurochemistry International. 2018.
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