Does D2 Determine DAT Location?

Science's STKE  24 Apr 2007:
Vol. 2007, Issue 383, pp. tw141
DOI: 10.1126/stke.3832007tw141

The presynaptic dopamine transporter (DAT), which facilitates the reuptake of released dopamine, plays a critical role in regulating the synaptic concentration of dopamine and thus the intensity and duration of the dopamine signal. DAT activity, which may be regulated by presynaptic D2 dopamine receptors (D2, a class of G protein-coupled receptors), is therefore pertinent to various neurological and neuropsychiatric disorders associated with altered dopaminergic signaling. Lee et al. found that D2 coimmunoprecipitated with DAT from rat striatal tissue. Affinity purification analysis (using fusion proteins containing different regions of D2 or DAT) combined with in vitro binding assays indicated that the two proteins interacted directly through regions in the third intracellular loop of D2 and the DAT N terminus. When D2S (the "short" isoform of D2) was coexpressed with DAT in human embryonic kidney (HEK) 293 cells, dopamine uptake was enhanced compared with that mediated by DAT alone. This facilitated uptake was unaffected by treatment with D2 antagonists and did not involve an increase in DAT abundance but was blocked by overexpression of minigenes encoding DAT or D2 sequences that mediated the interaction between the two proteins. Confocal immunofluorescence analysis indicated that D2S recruited DAT to the plasma membrane; similarly, cell ELISA assays indicated that D2S expression elicited ~20% increase in DAT localization to the plasma membrane. Intriguingly, injection into mice of peptides that blocked the D2-DAT interaction decreased dopamine uptake into striatal synaptosomes and led to increased locomotor activity. Thus, the authors conclude that D2S enhances DAT activity through direct protein interactions that enhance its localization to the plasma membrane.

F. J. S. Lee, L. Pei, A. Moszczynska, B. Vukusic, P. J. Fletcher, F. Liu, Dopamine transporter cell surface localization facilitated by a direct interaction with the dopamine D2 receptor. EMBO J. 26, 2127–2136 (2007). [PubMed]