Neurotransmitter levels in brain are critical for normal brain function. Abnormal levels of neurotransmitter, resulting in inappropriate neural signaling, underlie a diverse list of brain disorders. For example, epilepsy, excitotoxic cell death, depression, and a number of conditions related to drug abuse are all related to abnormal transmitter levels in brain. Neurotransmitter transporters are proteins, located on neurons and glia, that function in part to transport transmitter from the extracellular milieu into cells. As such, they play a central role in regulating synaptic signaling. While much is being learned about the permeation properties of various neurotransmitter transporters (e.g., transport rates, substrate affinities, conducting states), little is known about how particular structural domains of the transporter participate in the permeation process. Furthermore, while it is known that transporter function can be regulated, the extent to which the regulation occurs through manipulation of the domains involved in permeation is not known. The major goal of this application is to define the role of intra-molecular and inter-molecular interactions in regulation of the GABA transporter GAT1.
Specific Aim 1 is to test the hypothesis that the amino terminal cytoplasmic tail of the GABA transporter GAT1 positively regulates GABA transport through interactions with internal cytoplasmic loops of the transporter.
Specific Aim 2 is to test the hypothesis that proteins that physically interact with the amino terminal tail of GAT1 negatively regulate GAT1 function by preventing the N-terminal tail from interacting with the internal cytoplasmic loops of the transporter.
Specific Aim 3 is to test the hypothesis that intermolecular interactions that negatively regulate transporter function can be modulated by physiologically relevant factors. These studies are important because they will (i) define a new regulatory role in permeation for intracellular transporter domains; (ii) elucidate a novel mechanism for the cellular regulation of transporter function through protein-protein interactions; and (iii) provide data that could be useful in strategies aimed at regulating transporter function in the treatment of disorders related to abnormal transmitter levels.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Research Project (R01)
Project #
5R01MH061468-05
Application #
6742495
Study Section
Special Emphasis Panel (ZRG1-MDCN-4 (01))
Program Officer
Asanuma, Chiiko
Project Start
2000-05-10
Project End
2006-04-30
Budget Start
2004-05-26
Budget End
2006-04-30
Support Year
5
Fiscal Year
2004
Total Cost
$243,750
Indirect Cost
Name
University of Southern California
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089
Quick, M W (2006) The role of SNARE proteins in trafficking and function of neurotransmitter transporters. Handb Exp Pharmacol :181-96
Hansra, Nina; Arya, Shruti; Quick, Michael W (2004) Intracellular domains of a rat brain GABA transporter that govern transport. J Neurosci 24:4082-7
Chen, Nian-Hang; Reith, Maarten E A; Quick, Michael W (2004) Synaptic uptake and beyond: the sodium- and chloride-dependent neurotransmitter transporter family SLC6. Pflugers Arch 447:519-31
Wang, Dan; Deken, Scott L; Whitworth, Terri L et al. (2003) Syntaxin 1A inhibits GABA flux, efflux, and exchange mediated by the rat brain GABA transporter GAT1. Mol Pharmacol 64:905-13
Jensen, Kimmo; Chiu, Chi-Sung; Sokolova, Irina et al. (2003) GABA transporter-1 (GAT1)-deficient mice: differential tonic activation of GABAA versus GABAB receptors in the hippocampus. J Neurophysiol 90:2690-701
Sung, Uhna; Apparsundaram, Subramaniam; Galli, Aurelio et al. (2003) A regulated interaction of syntaxin 1A with the antidepressant-sensitive norepinephrine transporter establishes catecholamine clearance capacity. J Neurosci 23:1697-709
Deken, Scott L; Wang, Dan; Quick, Michael W (2003) Plasma membrane GABA transporters reside on distinct vesicles and undergo rapid regulated recycling. J Neurosci 23:1563-8
Quick, Michael W (2003) Regulating the conducting states of a mammalian serotonin transporter. Neuron 40:537-49
Quick, Michael W (2002) Substrates regulate gamma-aminobutyric acid transporters in a syntaxin 1A-dependent manner. Proc Natl Acad Sci U S A 99:5686-91
Chiu, Chi-Sung; Jensen, Kimmo; Sokolova, Irina et al. (2002) Number, density, and surface/cytoplasmic distribution of GABA transporters at presynaptic structures of knock-in mice carrying GABA transporter subtype 1-green fluorescent protein fusions. J Neurosci 22:10251-66

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