A major mechanism for regulating the activity of biogenic amine neurotransmitter transporters, the important targets for therapeutic antidepressants and psychostimulant drugs of abuse, is through modulation of the abundance of functional transporters at the plasma membrane. For the dopamine transporter (DAT) we have found that regulated internalization proceeds through one of two apparently distinct mechanisms. The first pathway is stimulated by activation of protein kinase C (PKC) and appears to be mediated by a clathrin-coated pit mechanism. The second pathway is activated by exposure to amphetamine-like drugs, is not affected by PKC antagonists and does not appear to proceed through a clathrin-dependent pathway. We hypothesize that this distinct action of amphetamine and other amphetamine-like drugs may contribute to the unique features of their addictive properties. Internalization of the DAT by the two pathways can be observed to different extents in various systems, including neuronal cultures, catecholaminergic cell lines and other in vitro models.
The aims of this research proposal are to define components of the internalization machinery which are selectively mobilized by the PKC- and amphetamine-induced pathways and to elucidate the cellular mechanisms that regulate DAT internalization in dopamine neurons. High-resolution confocal imaging will be employed to identify the primary endocytic pathways for both PKC- and amphetamine-stimulated internalization mechanisms in model cell lines and in primary cultures of mesencephalic dopamine neurons. siRNAi techniques will be employed to establish the two distinct mechanisms of transporter internalization. Two neuropeptide systems, the orexins and CRF, modulate dopaminergic neurotransmission in vivo by coupling to PKC signaling in dopamine neurons, and appear to play a critical role in cocaine-induced psychomotor sensitization. We will also determine to what extent these endogenous neuropeptides and other regulators activate or modulate PKC- and amphetamine-mediated DAT trafficking in dopamine neuron cultures. The goal of these studies is to more precisely define the major machinery regulating DAT activity and to understand how these pathways modulate the actions of therapeutic and abused drugs that target biogenic amine transporters.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA007595-17
Application #
7894856
Study Section
Synapses, Cytoskeleton and Trafficking Study Section (SYN)
Program Officer
Pollock, Jonathan D
Project Start
1992-01-10
Project End
2011-07-31
Budget Start
2010-08-01
Budget End
2011-07-31
Support Year
17
Fiscal Year
2010
Total Cost
$378,750
Indirect Cost
Name
University of Pittsburgh
Department
Biology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Mortensen, Ole V; Larsen, Mads B; Amara, Susan G (2017) MAP Kinase Phosphatase 3 (MKP3) Preserves Norepinephrine Transporter Activity by Modulating ERK1/2 Kinase-Mediated Gene Expression. Front Cell Neurosci 11:253
Wheeler, David S; Underhill, Suzanne M; Stolz, Donna B et al. (2015) Amphetamine activates Rho GTPase signaling to mediate dopamine transporter internalization and acute behavioral effects of amphetamine. Proc Natl Acad Sci U S A 112:E7138-47
Underhill, Suzanne M; Wheeler, David S; Amara, Susan G (2015) Differential regulation of two isoforms of the glial glutamate transporter EAAT2 by DLG1 and CaMKII. J Neurosci 35:5260-70
Hong, Weimin C; Amara, Susan G (2013) Differential targeting of the dopamine transporter to recycling or degradative pathways during amphetamine- or PKC-regulated endocytosis in dopamine neurons. FASEB J 27:2995-3007
Larsen, Mads B; Fontana, Andreia C K; Magalhaes, Lizandra G et al. (2011) A catecholamine transporter from the human parasite Schistosoma mansoni with low affinity for psychostimulants. Mol Biochem Parasitol 177:35-41
Larsen, Mads Breum; Sonders, Mark S; Mortensen, Ole Valente et al. (2011) Dopamine transport by the serotonin transporter: a mechanistically distinct mode of substrate translocation. J Neurosci 31:6605-15
Hong, Weimin C; Amara, Susan G (2010) Membrane cholesterol modulates the outward facing conformation of the dopamine transporter and alters cocaine binding. J Biol Chem 285:32616-26
Fontana, Andréia C K; Sonders, Mark S; Pereira-Junior, Olavo S et al. (2009) Two allelic isoforms of the serotonin transporter from Schistosoma mansoni display electrogenic transport and high selectivity for serotonin. Eur J Pharmacol 616:48-57
Mortensen, Ole V; Amara, Susan G (2006) Gain of function mutants reveal sites important for the interaction of the atypical inhibitors benztropine and bupropion with monoamine transporters. J Neurochem 98:1531-40
Mortensen, Ole V; Amara, Susan G (2003) Dynamic regulation of the dopamine transporter. Eur J Pharmacol 479:159-70

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