Gonzalo E. Torres, Ph.D.
Gonzalo E. Torres, PhD.
Department of Pharmacology and Therapeutics
1200 Newell Dr., ARB R5-252, PO Box 100267
Gainesville, FL 32610-0267
Associate Professor, Department of Pharmacology and Therapeutics.
Molecular mechanisms associated with amphetamine actions in the brain.
PhD, St Louis University, 1999, Adviser: Mark Voigt, PhD
Postdoc Duke University, 1999-2004, Adviser: Marc Caron, PhD
Current Research Focus
Research efforts in our laboratory use proteomics-based approaches to examine higher order organization and protein-protein interactions in the control of dopamine homeostasis. Over the last 15 years, several studies have revealed numerous mechanisms influencing the activity and cellular distribution of the dopamine transporter (DAT), suggesting that fine-tuning of dopamine homeostasis occurs via an elaborate interplay of multiple pathways. Our lab recently found a direct link between DAT and synaptic vesicles, which enables efficient loading of transmitter into vesicles destined for release. We also showed that the βγ subunits of G proteins regulate DAT activity. In heterologous cells and brain tissue, a physical association between Gβγ subunits and DAT was demonstrated by co-immunoprecipitation. Furthermore, in vitro assays determined that this association occurs via a direct interaction between the intracellular carboxy-terminus of DAT and Gβγ. Functional assays performed in the presence of the non-hydrolyzable GTP analog GTP-γ-S, Gβγ subunit overexpression, or the Gβγ activator mSIRK all resulted in rapid inhibition of DAT activity in heterologous systems. Gβγ activation by mSIRK also inhibited dopamine uptake in brain synaptosomes and dopamine clearance from mouse striatum as measured by high-speed chronoamperometry in vivo. Gβγ subunits are intracellular signaling molecules that regulate a multitude of physiological processes through interactions with enzymes and ion channels. These findings add neurotransmitter transporters to the growing list of molecules regulated by G-proteins and suggest a novel role for Gβγ signaling in the control of dopamine.
In addition to uptake or direct transport, DAT can also function to release DA. This process, referred to as reverse transport or efflux, enables addictive psychostimulants, such as amphetamine and its analogues, to increase extracellular DA levels in motivational and reward areas of the brain. It has long being recognized that DA neurons release DA through exocytotic and non-exocytotic processes. However, the exact mechanisms by which physiological signals or psychostimulants induce DA release through DAT have not been defined. Thus, examining the basic mechanism(s) that affect reverse transport through DAT is critical for understanding both fundamental aspects of DA regulation and for clinical intervention in DA-related brain disorders associated with the therapeutic use and abuse of psychostimulants. We recently discovered that Gβγ binds DAT and regulates transporter activity. This effect was demonstrated in cultured cells, brain synaptosomes, and in vivo. More importantly, activation of Gβγ promotes DAT-mediated DA efflux, whereas inhibition of Gβγ attenuates amphetamine-elicited DA efflux in cultured cells. Finally, activation of Gβγ enhances, whereas inhibition of Gβγ reduces amphetamine-evoked locomotor activity in vivo. Based on these preliminary data, the central hypothesis of the lab’s research is that the interaction between DAT and βγ subunits promotes DA release through DAT and is involved in the actions of amphetamine.
Egaña, L., Cuevas, R., Baust, T., Parra, L.A. Leak, R., Hochendoner, S., Peña, K., Quiroz, M., Hong, W.C., Dorostkar, M.M., Janz, R., Sitte, H.H. and Torres, G.E. (2009) Physical and functional interaction between the dopamine transporter and the synaptic vesicle protein synaptogyrin-3. J. Neurosci. 29, 4952-604.
Cartier, E., Baust, T., Parra, L., Quiroz, M., Egana, L. and Torres, G.E. (2010) A biochemical and functional protein complex involving dopamine synthesis and transport into synaptic vesicles. J. Biol. Chem. 285, 1957-66.
Sager, J.J. and Torres, G.E. (2011) Proteins interacting with monoamine transporters: current state and future challenges. Biochemistry 50, 7295-310.
Matthews, M., Bondi, C., Torres, G. and Moghaddam, B. (2013) Reduced presynaptic dopamine activity in adolescent dorsal striatum. Neuropsychopharmacology. 38,1344-51.
Harun, R., Grassi, C., Munoz, J. Torres, GE, and Wagner, A. (2015) Neurobiological model of stimulated dopamine neurotransmission to interpret fast-scan cyclic voltammetry data. Brain Research 1599,67-84.