Oligomerization of the Dopamine Transporter: Cocaine-Induced Conformational Changes at a Homo-Dimer Interface
Jonathan A. Javitch, M.D., Ph.D., Columbia University

Dr. Jonathan Javitch discussed evidence supporting the idea that the dopamine transporter (DAT) and homologous neurotransmitter exist in the plasma membrane as oligomers. Cysteine cross-linking experiments in DAT show that TM6 and TM4 contribute to the formation of two distinct symmetrical interfaces and suggest that the transporter exists as a tetramer. Cocaine analogs prevent cross linking of some, but not all, cysteines in TM4, which suggests that cocaine binding induces a conformational change at the multimer interface.

Protein-Protein Interactions: Defining New Pathways Involved in the Regulation of the Dopamine Transporter
Gonzalo E. Torres, Ph.D., Duke University Medical Center

Dr. Gonzalo Torres discussed the identification of protein-protein interactions supporting dopamine transporter trafficking and its result in increased understanding of mechanisms that underlie the transporter’s cellular regulation and functional expression. Torres discussed attempts to use a proteomic approach to identify the entire network of proteins associated with DAT through selective immunoprecipitation of the transporter complex from examining brain tissue, separating the proteins using 2D gels, and analyzing the proteins using mass spectrometry and database analysis. Future research will focus on identifying the protein network associated with monamine transporters, as well as the subcellular compartments involved in the different steps of targeting and trafficking these transporters, with the ultimate goal of examining how these mechanisms relate to the problem of drug addiction.

DA Transporter Currents: A Reason for Excitement
Susan L. Ingram, Ph.D., Washington State University

Dr. Susan Ingram described research examining the concept that DAT may dynamically regulate DA neurotransmission through both uptake and the release of DA through its channel activity. She discussed research indicating that DAT mediates an uncoupled chloride conductance and that DAT currents in neurons are activated at much lower concentrations than the D-2 receptor or transport. Other studies showed that the DAT-mediated chloride conductance excites DA neurons, and that activation of DAT-mediated currents is a potential mechanism for stimulating DA release in the substantia nigra.

Dopamine Transporter Genetics: From Model Systems to Man
Randy D. Blakely, Ph.D., Vanderbilt University School of Medicine

Dr. Randy Blakely highlighted the ways in which efforts to manipulate the DAT of C. elegans using a forward genetic approach have elucidated critical sites supporting DAT function and have advanced a new model system for the study of dopamine neuron degeneration. Included was the finding that non-DAT-1 genes participate in DAT-1 function, DAT-1 regulation, or in the sensitivity to neurotoxin. Additionally, he discussed human studies on the elucidation of DAT-supported human disorders via functional investigations of DAT polymorphisms.