Dopamine transporter expression and transport capacity is regulated by palmitoylation

Abstract

The dopamine transporter (DAT) mediates the reuptake of synaptic dopamine and thus regulates the spatio-temporal dynamics of dopaminergic neurotransmission. Complex control of DAT is exerted by various regulatory processes including posttranslational modifications. We previously found that DAT is palmitoylated, via the addition of a 16-carbon palmitic acid moiety to Cys 580, and that depalmitoylation led to reductions in Vmax and transporter levels. Palmitoylation is a reversible process catalyzed by palmitoyl acyltransferases (PATs) (also called DHHC enzymes based on the conserved active site sequence Asp-His-His-Cys), and palmitoyl-protein thioesterases (PPTs). 23 PAT enzymes, have been identified in the human genome, with some associated with DA diseases such as schizophrenia. To identify the PATs and PPTs involved with DAT palmitoylation and function, we co-expressed various DHHC enzymes individually with DAT and assessed DAT palmitoylation, expression, surface levels, and DA transport capacity. Palmitoylation and expression of DAT were enhanced by the neuronal PATs, DHHC2, DHHC3, DHHC8, DHHC15, and DHHC17 while several others had no effect, consistent with a role for palmitoylation in opposing DAT degradation. Increased DAT palmitoylation also led to enhanced DA uptake with no effect on surface levels, suggesting that palmitoylation also increases transport capacity via an alteration of DAT transport kinetics. Palmitoylation of DAT thus plays a role in both short- and long-term regulation of DAT, and may represent a point of DA reuptake dysregulation in dopaminergic disorders. Support: The National Institute on Drug Abuse (Grant # DA 13147 RAV & DA 031991 JDF) and ND EPSCoR (Grant # EPS-0184442 DER)