The dopamine transporter (DAT) has been identified as a principal brain receptor site previously correlated with the rewarding and euphoric properties of cocaine. Euphoric responses to rapid administration of cocaine can be much more prominent than those that follow slower rates of administration. In previous years, investigators in this Branch have found that activators of protein kinase C (PKC) modulate dopamine transport in transiently-expressing COS cells. In the current year, we have followed previous observations that identified DAT as a phosphoprotein to identify efects of several PKC, MAP kinase, MEKkinase and IP3 kinase agents on dopamine upatke rates. Studies of site directed mutants in potential phosphoacceptor sites identify N-terminal mutants as important for MAP kinase, IP3 kinase and for PKC regulation. These studies document that the DAT regulation can occur as internalization of the tranpsorter or as downregulation of the function of the transporter that remains expressed on cell surfaces, using activation of distince kinase pthways. Coexpression with KEPI also alters DAT function. These data increase evidence that PKC and MAP kinase regulation of DAT occurs through multiple direct- and indirect mechanisms. Work during this year has also provided insights into functions of the human allelic variants in the DAT 5' flanking region. Human variants and haplotypes from this region have beeen identified by genomic resequencing. Large constructions containing a number of variants in each of the two most prominent haplotypes have been expressed in two cell expression systems as luciferase fusion constructions. Interestingly, these results provide evidence for up to a 30% difference in experession related to the individual human haplotypes. These studies complement studies of regulation at a protein phospphorylation level to provide a more complete picture of the state- and trait-dependent features of regulation of this important determinant of dopaminergic functions including those important for drug reward.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
Intramural Research (Z01)
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National Institute on Drug Abuse
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Lin, Zhicheng; Uhl, George R (2005) Proline mutations induce negative-dosage effects on uptake velocity of the dopamine transporter. J Neurochem 94:276-87
Dohi, Toshihiro; Kitayama, Shigeo; Morioka, Norimitsu et al. (2004) Regulation of dopamine and MPP+ transport by catecholamine transporters. Nihon Shinkei Seishin Yakurigaku Zasshi 24:43-7
Lin, Zhicheng; Zhang, Ping-Wu; Zhu, Xuguang et al. (2003) Phosphatidylinositol 3-kinase, protein kinase C, and MEK1/2 kinase regulation of dopamine transporters (DAT) require N-terminal DAT phosphoacceptor sites. J Biol Chem 278:20162-70
Moron, Jose A; Zakharova, Irina; Ferrer, Jasmine V et al. (2003) Mitogen-activated protein kinase regulates dopamine transporter surface expression and dopamine transport capacity. J Neurosci 23:8480-8
Uhl, George R (2003) Dopamine transporter: basic science and human variation of a key molecule for dopaminergic function, locomotion, and parkinsonism. Mov Disord 18 Suppl 7:S71-80
Uhl, George R; Lin, Zhicheng (2003) The top 20 dopamine transporter mutants: structure-function relationships and cocaine actions. Eur J Pharmacol 479:71-82
Lin, Zhicheng; Uhl, George R (2003) Human dopamine transporter gene variation: effects of protein coding variants V55A and V382A on expression and uptake activities. Pharmacogenomics J 3:159-68
Liu, Qing-Rong; Zhang, Ping-Wu; Zhen, Qiaoxi et al. (2002) KEPI, a PKC-dependent protein phosphatase 1 inhibitor regulated by morphine. J Biol Chem 277:13312-20