The broad long-term objectives of this proposal are to identify the molecular determinants of psychostimulant recognition (cocaine and amphetamine) by serotonin transporters (SERTs), thereby revealing fundamental mechanisms involved SERT function and modulation by drugs. This project has direct health relatedness as SERTs are the molecular target for.most antidepressant drugs as well as many drugs of abuse. Antidepressants such as paroxetine, fluoxetine, and imipramine bind to the transporter and inhibit serotonin uptake, thereby prolonging the extracellular lifespan of the neurotransmitter. The abused psychostimulants cocaine and amphetamine also bind to the transporter, but have distinct pharmacologic effects leading to abuse potential and possible neurotoxicity. Despite the cloning of SERT in the early 1990's, the molecular and cellular neurobiology surrounding the function of this transport protein remains to be fully elucidated. This project uses a multidisciplinary approach aimed at significantly advancing knowledge regarding the molecular pharmacology of psychostimulants at SERTs. The studies will use multiple techniques including expression and characterization of recombinant transporters in mammalian cells, the substituted cysteine accessibility method (SCAM), real-time fluorescent substrate assays, electrophysiology, and site-directed mutagenesis to identify amino acids involved with specific transporter functions including antagonist and substrate binding. In addition, computer-assisted structure-activity studies of cocaine and amphetamine derivatives will be coupled with mutagenesis in an attempt to identify direct ligand-transporter interactions. Therefore, the specific aims of this project are: 1) To determine the core domains forming the substrate permeation pathway, 2) To elucidate information about the orientation of SERT domains, and 3) To identify and elucidate the role of amino acids in the core domains involved with recognition of psychostimulants. The proposed strategies will provide critical new information linking protein structure to functional properties of the transporter and an enhanced understanding of the molecular mechanisms of action for psychotherapeutic and abused drugs. Abused stimulants such as cocaine and amphetamine (including methamphetamine (""""""""Meth"""""""") and MDMA or 'ecstasy') are of great societal concern. The proposed studies will reveal important new information on how these abused drugs alter their target in the brain (i.e., the serotonin transporter) and offer new strategies to combat the addictive properties of these substances.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA018682-07
Application #
7388824
Study Section
Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
Program Officer
Hillery, Paul
Project Start
2000-09-01
Project End
2011-03-31
Budget Start
2008-04-01
Budget End
2009-03-31
Support Year
7
Fiscal Year
2008
Total Cost
$209,177
Indirect Cost
Name
Purdue University
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
072051394
City
West Lafayette
State
IN
Country
United States
Zip Code
47907
Sealover, Natalie R; Felts, Bruce; Kuntz, Charles P et al. (2016) The external gate of the human and Drosophila serotonin transporters requires a basic/acidic amino acid pair for 3,4-methylenedioxymethamphetamine (MDMA) translocation and the induction of substrate efflux. Biochem Pharmacol 120:46-55
Torres-Altoro, Melissa I; Kuntz, Charles P; Nichols, David E et al. (2010) Structural analysis of the extracellular entrance to the serotonin transporter permeation pathway. J Biol Chem 285:15369-79
Wenthur, Cody J; Rodriguez, Gustavo J; Kuntz, Charles P et al. (2010) Conformational flexibility of transmembrane helix VII of the human serotonin transporter impacts ion dependence and transport. Biochem Pharmacol 80:1418-26
Walline, Crystal C; Nichols, David E; Carroll, F Ivy et al. (2008) Comparative molecular field analysis using selectivity fields reveals residues in the third transmembrane helix of the serotonin transporter associated with substrate and antagonist recognition. J Pharmacol Exp Ther 325:791-800
Torres-Altoro, Melissa I; White, Kellie J; Rodriguez, Gustavo J et al. (2008) Helix XI contributes to the entrance of the serotonin transporter permeation pathway. Protein Sci 17:1761-70