Disease relevance of SLC6A3

• There was no association of the SLC6A3 genotype with obesity for non-Hispanic whites (N = 420) [1].
• Dopamine transporter (SLC6A3) 5' region haplotypes significantly affect transcriptional activity in vitro but are not associated with Parkinson's disease [2].
• Polygenic inheritance of Tourette syndrome, stuttering, attention deficit hyperactivity, conduct, and oppositional defiant disorder: the additive and subtractive effect of the three dopaminergic genes--DRD2, D beta H, and DAT1 [3].
• CNS diseases such as Parkinson, schizophrenia, and attention deficit hyperactivity disorder (ADHD) are characterized by a significant alteration of dopamine transporter (DAT) density [4].
• However, patients with psychosis or dyskinesia carried the nine copy allele 40-bp VNTR of the DAT more frequently than nonafflicted patients (60.0 vs 36.8%, p = 0.008; and 54.7 vs 32.9%, p = 0.006) [5].

Psychiatry related information on SLC6A3

• Together, these data are consistent with the presence of multiple variants in DAT1 that convey susceptibility to bipolar disorder [6].
• In analyses of the relation of symptom levels to the DRD4 and DAT1 genotypes, fathers possessing the 7 repeat DRD4 allele had greater levels of both inattention and conduct disorder symptoms [7].
• Polymorphisms of three different dopaminergic genes, dopamine D2 receptor (DRD2), dopamine beta-hydroxylase (D beta H), and dopamine transporter (DAT1), were examined in Tourette syndrome (TS) probands, their relatives, and controls [3].
• Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families [8].
• Drugs that act on the human serotonin transporter (hSERT), human dopamine transporter (hDAT) and human noradrenaline transporter (hNET) are important in antidepressant treatment and well known in drug abuse [9].

High impact information on SLC6A3

• Cocaine is believed to work by blocking the dopamine transporter (DAT) and thereby increasing the availability of free dopamine within the brain [10].
• This is the first demonstration in humans that the doses used by cocaine abusers lead to significant blockade of DAT, and that this blockade is associated with the subjective effects of cocaine [10].
• Mice lacking the gene encoding the plasma membrane dopamine transporter (DAT) have elevated dopaminergic tone and are hyperactive [11].
• These transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET), which are expressed selectively on the corresponding neurons, are established targets of many psychostimulants, antidepressants, and neurotoxins [12].
• The DAT internalization signal is conserved across SLC6 neurotransmitter carriers and is functional in the homologous norepinephrine transporter, suggesting that this region is likely to be the endocytic signal for all SLC6 neurotransmitter transporters [13].

Chemical compound and disease context of SLC6A3

• OBJECTIVE: To assess the association between a polymorphism related to dopamine function, dopamine transport (SLC6A3), and obesity in smokers [1].
• However, the nine copy allele 40-bp VNTR of the DAT is a predictor for the occurrence of psychosis or dyskinesia in L -dopa-treated patients [5].
• Associations between DAT gene polymorphisms and human disorders with possible links to dopaminergic neurotransmission, including attention-deficit/hyperactivity disorder (ADHD) and consequences of cocaine and alcohol administration, have been reported [14].
• These comprehensive analyses, however, fail to identify any common protein coding DAT sequence variant in more than 150 unrelated individuals free of neuropsychiatric disease, 109 individuals meeting City of Hope criteria for Tourette's syndrome, 64 individuals with DSM-IV diagnoses of ethanol dependence, or 15 individuals with ADHD [14].
• These results indicate that for a given dose of methylphenidate, individual differences in DAT blockade are not the main source for the intersubject variability in MP-induced increases in DA [15].

Biological context of SLC6A3

• CONCLUSIONS: These findings suggest that genetic variation at the SLC6A3 3' VNTR polymorphism may modify dopamine transporter function [16].
• METHOD: The authors assessed dopamine transporter genotype at the SLC6A3 3' variable number of tandem repeats (VNTR) polymorphism and serotonin transporter genotype at the SLC6A4 promotor VNTR polymorphism in 30 healthy subjects who also underwent single photon emission computed tomography with [(123)I]beta-CIT [16].
• We aimed to characterize variation in the 5' region of SLC6A3 because little is known about the extent of variation in this region and potential consequences of such variation on gene expression [2].
• As a means of investigating the risk of smoking associated with genetic polymorphisms in the dopamine transporter (SLC6A3) and the D2 dopamine receptor (DRD2) genes, a case-control study of 289 smokers and 233 nonsmoking controls and a case series analysis of smokers were conducted [17].
• Stress-induced cigarette craving: effects of the DRD2 TaqI RFLP and SLC6A3 VNTR polymorphisms [18].

Anatomical context of SLC6A3

• A polymorphism of the DAT gene (SLC6A3) was associated with the in vivo transporter availability in the putamen of abstinent alcoholics and control subjects [19].
• In the midbrain, however, the BP values for DAT were significantly lower (16%; p = .03) in children with ADHD [20].
• Furthermore, in voltage-clamped oocytes, D2R activation enhanced both DA uptake and DAT-mediated steady-state currents by as much as 70% [21].
• Using rat brain membranes, TB-1-099 weakly inhibited DAT binding (K(i) = 439 nM), was inactive at NET binding ([(3)H]nisoxetine), and partially inhibited SERT binding with an extrapolated plateau ("A" value) of 20% [22].
• We show that the COMT Met158 allele and the DAT 3' variable number of tandem repeat 10-repeat allele are independently associated in healthy humans with more focused neuronal activity (as measured with blood oxygen level-dependent functional magnetic resonance imaging) in the working memory cortical network, including the prefrontal cortex [23].

Associations of SLC6A3 with chemical compounds

• RESULTS: Subjects homozygous for the 10-repeat allele at the SLC6A3 locus demonstrated significantly lower dopamine transporter binding than carriers of the nine-repeat allele [16].
• METHOD: Effects of dopamine transporter (SLC6A3) and dopamine receptor (DRD2) genetic variants on smoking progression were evaluated in a cohort of 615 adolescents, including those who had never smoked, and in a subgroup including only adolescents who had been exposed to nicotine (i.e., smoked at least a puff of a cigarette) (N=292) [24].
• Despite all these data, few studies have addressed the relationship between genetic markers (specifically the VNTR) at the SLC6A3 locus and response to methylphenidate in ADHD patients [25].
• Chemical signaling by dopamine (DA) and L-norepinephrine (L-NE) at synapses is terminated by uptake via specialized presynaptic transport proteins encoded by the DA transporter (DAT) and L-NE transporter (NET) genes, respectively [26].
• These data support the hypothesis that the DAT may be a common neural substrate for cocaine and ethanol in dopaminergic neurons and it may be involved in the psychological effects of both addictions [27].

Physical interactions of SLC6A3

• Our findings suggest that the number of DAT binding sites is higher in drug-naive patients suffering from ADHD than in normal controls [28].
• The correlation observed between inhibitory potency for uptake and binding of either ligand at the hNET was lower than correlations between uptake and binding for hDAT and hSERT [29].
• From week 12 onward they expressed several other markers of dopamine transmission, i.e., D2R mRNA, D2R binding sites and DAT mRNA [30].
• Interestingly, TRPV1 binding was increased in the striatum of DAT KO mice, while CB1 receptor binding was unaffected [31].
• In the second part, the selectivity of the compounds for DAT binding vs SERT binding is studied [32].

Co-localisations of SLC6A3

• In human embryonic kidney 293 cells, Hic-5 colocalizes with DAT at polarized sites and reduces DAT uptake activity through a mechanism involving a decrease in the cell-surface levels of the transporter [33].
• In dopaminergic neurons, PICK1 colocalizes with the dopamine transporter (DAT) and forms a stable protein complex [34].
• DAT was colocalized with alpha-synuclein in mesencephalic neurons and cotransfected Ltk- cells [35].

Regulatory relationships of SLC6A3

• BIS pretreatment abolished norepinephrine-induced c-Fos expression hNET but not dopamine-induced c-Fos induction in hDAT cells [36].
• These results indicate a previously unappreciated role of microtubules in the modulation of DAT trafficking, and provide insight into a novel mechanism by which alpha-synuclein regulates DAT activity, by tethering the transporter to the microtubular network [37].
• 12 weakly released from NET- and SERT-expressing cells with maximum effects less than one-tenth of that of MDMA and did not release from DAT cells [38].
• The reductions of [(3)H]DA uptake and AMPH-induced DAT internalization also were inhibited by coexpression of a dominant negative mutant of dynamin I (K44A), indicating that endocytosis modulates transport capacity, likely through a clathrin-mediated pathway [39].
• In PD, the loss of TH protein in the ventral tier of the substantia nigra pars compacta (SNpc) of the PD group in accompanied by severe losses in the number of neurons that express TH mRNA and DAT mRNA (74% loss) [40].

Other interactions of SLC6A3

• The relation of DAT1 to ADHD increased monotonically, from low to medium to high levels of symptom severity [41].
• Molecular genetic investigations of ADHD have found positive associations with the 480-bp allele of a VNTR situated in the 3' untranslated region of DAT1 and allele 7 of a VNTR in exon 3 of DRD4 [42].
• Correlation between D' and physical distance was observed between markers at DAT1 and DRD5 for distances less than 50 kb [43].
• We confirmed the DAT1 association and also identified two additional susceptibility loci at the DRD5 and DBH [43].
• Alpha-synuclein-mediated inhibition of hDAT activity was independent of expression vectors, cell types and methods of transfection [44].

Analytical, diagnostic and therapeutic context of SLC6A3

• We found no evidence of association with the DAT1 polymorphism, despite a sample size that has up to 80% power to detect a previously reported effect size [42].
• Co-immunoprecipitation studies confirmed the formation of a stable complex between alpha-synuclein and DAT, through direct protein:protein interactions [44].
• Dopamine and norepinephrine robustly induced c-Fos immunofluorescence in both hDAT and hNET cells, but not in untransfected HEK-293 cells, demonstrating that catecholamine-induced c-Fos induction was DAT- and NET-dependent [36].
• OBJECTIVES: With an equal number of positive and negative association studies between the 10-repeat of the DAT gene and ADHD, a meta-analysis is required for this other candidate gene [45].
• Biological assays revealed that some compounds having the N-3 atom substituted with aryl groups possess significant affinity and selectivity for monoamine transporters, and in particular, compound 5d displayed an IC50 of 21 nM toward DAT, and a good selectivity toward SERT (IC50=1042 nM) [4].

References