Abstract

The dopamine transporter (DAT) plays a crucial role in the regulation of brain dopamine (DA) homeostasis through the re-uptake of DA back into the presynaptic terminal. In addition to re-uptake, DAT is also able to release DA through a process referred to as DAT-mediated DA efflux. This is the mechanism by which potent and highly addictive psychostimulants, such as amphetamine (AMPH) and its analogues, increase extracellular DA levels in motivational and reward areas of the brain. Recently, we discovered that G protein beta gamma subunits (G beta gamma) binds to the DAT, and that activation of G beta gamma results in DAT-mediated efflux - a similar mechanism as AMPH. Previously, we have shown that G beta gamma binds directly to a stretch of 15 residues within the intracellular carboxy terminus of DAT (residues 582-596). Additionally, a TAT peptide containing residues 582 to 596 of DAT was able to block the G beta gamma-induced DA efflux through DAT. Here, we use a combination of computational biology, mutagenesis, biochemical, and functional assays to identify the amino acid residues within the 582-596 sequence of the DAT carboxy terminus involved in the DAT-G beta gamma interaction and G beta gamma-induced DA efflux. Our in-silico protein-protein docking analysis predicted the importance of F587 and R588 residues in a network of interactions with residues in G beta gamma. In addition, we observed that mutating R588 to alanine residue resulted in a mutant DAT which exhibited attenuated DA efflux induced by G beta gamma activation. We demonstrate that R588, and to a lesser extent F5837, located within the carboxy terminus of DAT play a critical role in the DAT-G beta gamma physical interaction and promotion of DA efflux. These results identify a potential new pharmacological target for the treatment of neuropsychiatric conditions in which DAT functionality is implicated including ADHD and substance use disorder.