amount of dopamine in the cell. This is best evidenced by the severe cognitive deficits, motor abnormalities, and hyperactivity of mice with no dopamine transporters. These characteristics have striking similarities to the symptoms of ADHD. Differences in the functional VNTR have been identified as risk factors for bipolar disorder and ADHD. Data has emerged that suggests there is also an association with stronger withdrawal symptoms from alcoholism, although this is a point of controversy. An allele of the DAT gene with normal protein levels is associated with non-smoking behavior and ease of quitting. Additionally, male adolescents particularly those in high-risk families (ones marked by a disengaged mother and absence of maternal affection) who carry the 10-allele VNTR repeat show a statistically significant affinity for antisocial peers. Increased activity of DAT is associated with several different disorders, including clinical depression. Mutations in DAT have been shown to cause dopamine transporter deficiency syndrome, an autosomal recessive movement disorder characterized by progressively worsening dystonia and parkinsonism. Pharmacology The dopamine transporter is the target of substrates, dopamine releasers, transport inhibitors and allosteric modulators. Cocaine blocks DAT by binding directly to the transporter and reducing the rate of transport. In contrast, amphetamine enters the presynaptic neuron directly through the neuronal membrane or through DAT, competing for reuptake with dopamine. Once inside, it binds to or enters synaptic vesicles through . When amphetamine binds to TAAR1, it reduces the firing rate of the postsynaptic neuron and triggers protein kinase A and protein kinase C signaling, resulting in DAT phosphorylation. Phosphorylated DAT then either operates in reverse or withdraws into the presynaptic neuron and ceases transport. When amphetamine enters the synaptic vesicles through VMAT2, dopamine is released into the cytosol. Amphetamine also produces dopamine efflux through a second TAAR1-independent mechanism involving CAMKIIα-mediated phosphorylation of the transporter, which putatively arises from the activation of DAT-coupled L-type calcium channels by amphetamine. The dopaminergic mechanisms of each drug are believed to underlie the pleasurable feelings elicited by these substances. Interactions Dopamine transporter has been shown to interact with: Alpha-synuclein, PICK1, and TGFB1I1. Apart from these innate protein-protein interactions, recent studies demonstrated that viral proteins such as HIV-1 Tat protein interacts with the DAT and this binding may alter the dopamine homeostasis in HIV positive individuals which is a contributing factor for the HIV-associated neurocognitive disorders. See also References External links Dopamine transporter-related Associations, Experiments, Publications and Clinical Trials Amphetamine Biology