Anomalous dopamine release associated with a human dopamine transporter coding variant.

Mazei-Robison MS, Bowton E, Holy M, Schmudermaier M, Freissmuth M, Sitte HH, Galli A, Blakely RD
J Neurosci. 2008 28 (28): 7040-6

PMID: 18614672 · PMCID: PMC2573963 · 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.

MeSH Terms (17)

Alanine Amphetamine Analysis of Variance Biotinylation Cell Line, Transformed Dopamine Dopamine Plasma Membrane Transport Proteins Dopamine Uptake Inhibitors Humans Membrane Potentials Methylphenidate Mutation Patch-Clamp Techniques Protein Transport Sodium Transfection Valine

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