Anomalous Dopamine Release Associated with a Human Dopamine Transporter Coding Variant

• Published in: The Journal of neuroscience Vol. 28; no. 28; pp. 7040 - 7046
• Main Authors: Mazei-Robison, Michelle S, Bowton, Erica, Holy, Marion, Schmudermaier, Martin, Freissmuth, Michael, Sitte, Harald H, Galli, Aurelio, Blakely, Randy D
• Format: Journal Article
• Language: English
• Published: United States Soc Neuroscience 09.07.2008; Society for Neuroscience
• Subjects: Alanine - genetics; Amphetamine - pharmacology; Analysis of Variance; Biotinylation - methods; Brief Communications; Cell Line, Transformed; Dopamine - metabolism; Dopamine Plasma Membrane Transport Proteins - genetics; Dopamine Plasma Membrane Transport Proteins - physiology; Dopamine Uptake Inhibitors - pharmacology; Humans; Membrane Potentials - drug effects; Membrane Potentials - physiology; Methylphenidate - pharmacology; Mutation - genetics; Patch-Clamp Techniques; Protein Transport - drug effects; Sodium - metabolism; Transfection; Valine - genetics
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/JNEUROSCI.0473-08.2008

Dopamine (DA) signaling at synapses is tightly coordinated through opposing mechanisms of vesicular fusion-mediated DA release and transporter-mediated DA clearance. Altered brain DA signaling is suspected to underlie multiple brain disorders, including schizophrenia, Parkinson's disease, bipolar disorder, and attention-deficit hyperactivity disorder (ADHD). We identified a pedigree containing two male children diagnosed with ADHD who share a rare human DA transporter (DAT; SLC6A3 ) coding variant, Ala559Val. Among >1000 control and affected subjects, the Val559 variant has only been isolated once previously, in a female subject with bipolar disorder. Although hDAT Ala559Val supports normal DAT protein and cell surface expression, as well as normal DA uptake, the variant exhibits anomalous DA efflux from DA-loaded cells. We also demonstrate that hDAT Ala599Val exhibits increased sensitivity to intracellular Na + , but not intracellular DA, and displays exaggerated DA efflux at depolarized potentials. Remarkably, the two most common ADHD medications, amphetamine and methylphenidate, both block hDAT Ala559Val-mediated DA efflux, whereas these drugs have opposite actions at wild-type hDAT. Our findings reveal that DA efflux, typically associated with amphetamine-like psychostimulants, can be produced through a heritable change in hDAT structure. Because multiple gene products are known to coordinate to support amphetamine-mediated DA efflux, the properties of hDAT Ala559Val may have broader significance in identifying a new mechanism through which DA signaling disorders arise. Additionally, they suggest that block of inappropriate neurotransmitter efflux may be an unsuspected mechanism supporting the therapeutic actions of existing transporter-directed medications.