Invited Symposium: Molecular and Cellular Analysis of Dopamine and Serotonin Transporters
Liu, F. (Centre for Addiction & Mental Health, Institute of Medical Sciences, University of Toronto, Canada)
Lee, F.J.S. (Centre for Addiction & Mental Health, Department of Psychiatry, University of Toronto, Canada)
McConkey, F. (Centre for Addiction & Mental Health, Department of Psychiatry, University of Toronto, Canada)
LeClerc, N. (Dept Pathologie & Biologie Cellulaire, University of Montreal, Canada)
Niznik, H.B. (Centre for Addiction & Mental Health, Departments of Psychiatry and Pharmacology, University of Toronto, Canada)
Because of the importance of the presynaptic dopamine transporter (DAT) in the control of synaptic availability of dopamine, its own regulation may be a crucial component in the maintenance of normal dopaminergic neurotransmission. Functional regulation of the DAT by second messenger systems has been observed in synaptosomes as well as with the cloned transporter, but little is understood regarding the mechanism(s) involved in this regulation. Using immunofluorescent confocal microscopy, we recently demonstrated that the regulation of transport capacity (Vmax) of the human DAT by protein kinase-dependent pathways is a consequence of the rapid bidirectional shuttling, or trafficking, of DAT protein between the plasma membrane and intracellular compartments, with the level of activity correlated to the amount of DAT protein present at the cell membrane. Identical rapid translocation patterns are observed in both mammalian (COS-7) and insect (Sf9) cells transiently expressing the human DAT. Similar observations have recently been described for the GABA1 and 5-HT transporters. Rapid membrane trafficking provides an efficient means by which the DAT may be regulated, and suggests a key role for cytoskeletal components in the dynamic regulation of DAT function. We now provide evidence that human DAT trafficking is influenced by the presence of the neural microtubule protein MAP2C, a developmentally regulated alternative spliced form of MAP2, which, when expressed in Sf9 cells, can induce cytoskeletal rearrangement and subsequent distinct morphological changes reminiscent of the changes accompanying neuronal morphogenesis. Co-expression of MAP2C with DAT in Sf9 cells results in a redistribution of DAT immunoreactivity, with an increase in DAT at the cell surface. This change is accompanied by an approx 2-fold increase in DAT function reflected by a change in Vmax from 0.38 to 0.81 pmol/10*5 cells/min. These observations indicate an involvement of the cytoskeleton in DAT functional regulation, and suggest that MAP2C may influence neurodevelopmental targeting/trafficking of the DAT protein.
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|Pristupa, Z.B.; Liu, F.; Lee, F.J.S.; McConkey, F.; LeClerc, N.; Niznik, H.B.; (1998). Cytoskeletal Proteins and the Regulation of hDAT Trafficking and Function. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/simantov/pristupa0780/index.html|
|© 1998 Author(s) Hold Copyright|