The effects of phosphorylation on the functional regulation of an expressed recombinant human dopamine transporter

Metabolic labeling experiments were performed using eukaryotic cells transfected with the human dopamine (DA) transporter cDNA. Autophosphorylation in the presence and absence of the transporter substrate DA, was analyzed. Dopamine transporter (DAT) was phosphorylated in the absence of DA and dephosphorylated in the presence of the substrate. The functional significance of this phenomenon was checked by incubating cells with phosphorylation promoting agents, all of which reduced substrate uptake and ligand binding significantly. It is shown that at least one site of phosphorylation on DAT is a serine residue. These experiments suggest that the state of phosphorylation of the DAT may play an important role in its biological function.