Regulation of dopamine transporter activity by carboxypeptidase E.
BACKGROUND
The dopamine transporter (DAT) plays a critical role in terminating the action of dopamine by rapid reuptake into the presynaptic neuron. Previous studies have revealed that the DAT carboxyl terminus (DAT-CT) can directly interact with other cellular proteins and regulate DAT function and trafficking.


RESULTS
Here, we have identified that carboxypeptidase E (CPE), a prohormone processing exopeptidase and sorting receptor for the regulated secretory pathway, interacts with the DAT-CT and affects DAT function. Mammalian cell lines coexpressing CPE and DAT exhibited increased DAT-mediated dopamine uptake activity compared to cells expressing DAT alone. Moreover, coexpression of an interfering DAT-CT minigene inhibited the effects of CPE on DAT. Functional changes caused by CPE could be attributed to enhanced DAT expression and subsequent increase in DAT cell surface localization, due to decreased DAT degradation. In addition, CPE association could reduce the phosphorylation state of DAT on serine residues, potentially leading to reduced internalization, thus stabilizing plasmalemmal DAT localization.


CONCLUSIONS
Taken together, our results reveal a novel role for CPE in the regulation of DAT trafficking and DAT-mediated DA uptake, which may provide a novel target in the treatment of dopamine-governed diseases such as drug addiction and obesity.
Zhang
Heping
H
Department of Neuroscience, Centre for Addiction and Mental Health, Toronto, Ontario, Canada. peacezhp@yahoo.com.cn
Li
Shupeng
S
Wang
Min
M
Vukusic
Brian
B
Pristupa
Zdenek B
ZB
Liu
Fang
F
D000818:Animals; D019556:COS Cells; D043423:Carboxypeptidase H / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D004795:Enzyme Stability; D057809:HEK293 Cells; D006801:Humans; D066298:In Vitro Techniques; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D014162:Transfection
D050483:Dopamine Plasma Membrane Transport Proteins; D011493:Protein Kinase C; D043423:Carboxypeptidase H; D004298:Dopamine