Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.3.1.107 (DAT)
1,471 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several studies have implicated the dopamine transporter gene (DAT1) as conferring susceptibility to attention deficit hyperactivity disorder (ADHD), in particular, a VNTR situated at the 3' end of the gene. In addition, the 10-repeat VNTR allele associated with ADHD has been reported to be associated with an over-active transporter protein (DAT). Thus children possessing this variant might be particularly responsive to methylphenidate, a drug known to act by blocking DAT. We have examined this hypothesis and now report an association between the 10-repeat VNTR DAT1 polymorphism and retrospectively rated methylphenidate response in a sample of 119 Irish children with ADHD (chi(2) = 7.918, df = 1, P = 0.005). Our findings suggest a role for the 10-repeat DAT1 risk allele in medication response and may help to predict positive clinical outcome in ADHD.
...
PMID:Association of the 480 bp DAT1 allele with methylphenidate response in a sample of Irish children with ADHD. 1289 75

1. The ability to target specific neurons can be used to produce selective neural lesions and potentially to deliver therapeutically useful moieties for treatment of disease. In the present study, we sought to determine if a monoclonal antibody to the dopamine transporter (anti-DAT) could be used to target midbrain dopaminergic neurons. 2. The monoclonal antibody recognizes the second, large extracellular loop of DAT. The antibody was conjugated to the "ribosome-inactivating protein"; saporin, and stereotactically pressure microinjected into either the center of the striatum or the left lateral ventricle of adult, male Sprague-Dawley rats. 3. Local intrastriatal injections produced destruction of dopaminergic neurons in the ipsilateral substantia nigra consistent with suicide transport of the immunotoxin. Intraventricular injections (i.c.v.) produced significant loss of dopaminergic neurons in the substantia nigra and ventral tegmental area bilaterally without evident damage to any other aminergic structures such as the locus coeruleus and raphe nuclei. To confirm the anatomic findings, binding of [3-H]mazindol to DAT in the striatum and midbrain was assessed using densitometric analysis of autoradiograms. Anti-DAT-saporin injected i.c.v. at a dose of 21 microg, but not 8 microg, produced highly significant decreases in mazindol binding consistent with loss of the dopaminergic neurons. 4. These results show that anti-DAT can be used to target midbrain dopaminergic neurons and that anti-DAT-saporin may be useful for producing a lesion very similar to the naturally occurring neural degeneration seen in Parkinson's disease. Anti-DAT-saporin joins the growing list of neural lesioning agents based on targeted cytotoxins.
...
PMID:Destruction of midbrain dopaminergic neurons by using immunotoxin to dopamine transporter. 1451 35

Recently we showed evidence that mutation of Tyr-335 to Ala (Y335A) in the human dopamine transporter (hDAT) alters the conformational equilibrium of the transport cycle. Here, by substituting, one at a time, 16 different bulky or charged intracellular residues, we identify three residues, Lys-264, Asp-345, and Asp-436, the mutation of which to alanine produces a phenotype similar to that of Y335A. Like Y335A, the mutants (K264A, D345A, and D436A) were characterized by low uptake capacity that was potentiated by Zn(2+). Moreover, the mutants displayed lower affinity for cocaine and other inhibitors, suggesting a role for these residues in maintaining the structural integrity of the inhibitor binding crevice. The conformational state of K264A, Y335A, and D345A was investigated by assessing the accessibility to MTSET ([2-(trimethylammonium)ethyl]-methanethiosulfonate) of a cysteine engineered into position 159 (I159C) in transmembrane segment 3 of the MTSET-insensitive "E2C" background (C90A/C306A). Unlike its effect at the corresponding position in the homologous norepinephrine transporter (NET I155C), MTSET did not inhibit uptake mediated by E2C I159C. Furthermore, no inhibition was observed upon treatment with MTSET in the presence of dopamine, cocaine, or Zn(2+). Without Zn(2+), E2C I159C/K264A, E2C I159C/Y335A, and E2C I159C/D345A were also not inactivated by MTSET. In the presence of Zn(2+) (10 microm), however, MTSET (0.5 mm) caused up to approximately 60% inactivation. As in NET I155C, this inactivation was protected by dopamine and enhanced by cocaine. These data are consistent with a Zn(2+)-dependent partial reversal of a constitutively altered conformational equilibrium in the mutant transporters. They also suggest that the conformational equilibrium produced by the mutations resembles that of the NET more than that of the DAT. Moreover, the data provide evidence that the cocaine-bound state of both DAT mutants and of the NET is structurally distinct from the cocaine-bound state of the DAT.
...
PMID:Identification of intracellular residues in the dopamine transporter critical for regulation of transporter conformation and cocaine binding. 1459 28

Alpha-synuclein modulates dopamine homeostasis in dopamine-producing neurons of substantia nigra, partly through regulation of human dopamine transporter (hDAT) activity. To identify the underlying mechanisms, we disrupted the modulation of hDAT activity by wild-type (wt) alpha-synuclein, and its familial Parkinson's disease linked mutants A30P and A53T, by mild trypsinization (0.1%, 30 s) of Ltk(-) cotransfected cells. Trypsin completely reversed the attenuation of hDAT function mediated by wt and the A30P mutant. In A53T coexpressing cells, where DAT activity is not downregulated, trypsinization did not induce any changes. These effects of trypsin were mimicked by collagenase I and Dispase (0.1%, 1 min each) but not by chymotrypsin, Pronase, or papain (0.1%, up to 2 min each). Trypsin increased dopamine uptake in rat primary mesencephalic neurons, suggesting that DAT activity is also subjected to modulation by alpha-synuclein in these neurons that endogenously coexpress both proteins. In trypsinized cells, dopamine accelerated both production of reactive oxygen species and cell death in hDAT and wt or A30P, but not A53T, coexpressing cells, compared to nontrypsinized cells. Paradoxically, trypsin increased the protein-protein interactions between the synuclein variants and hDAT, without any noticeable proteolysis of these proteins. hDAT-alpha-synuclein protein-protein interactions occurred through residues 58-107 (NAC domain) of the alpha-synuclein variants and residues 598-620 of the carboxy-terminal tail of hDAT, in both trypsinized and nontrypsinized cells. Confocal microscopy and biotinylation studies show that, in cells expressing the wt or A30P variants, but not the A53T mutant, hDAT is sequestered away from the plasma membrane into the cytoplasm, an effect that is reversed by trypsin. These results show that alpha-synuclein modulates hDAT function through trafficking of the transporter in a process that can be disrupted by trypsin.
...
PMID:Trypsin disrupts the trafficking of the human dopamine transporter by alpha-synuclein and its A30P mutant. 1475 60

Administration of the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to C57BL/6 mice targets nigrostriatal dopaminergic neurons, leading to cell death and the depletion of striatal dopamine. After MPTP lesioning in young adult mice, surviving nigrostriatal dopaminergic neurons display robust and reproducible return of striatal dopamine weeks to months after injury. Thus, the mouse provides an excellent model with which to investigate the mechanisms underlying neuroplasticity of the nigrostriatal system following neurotoxic injury. The purpose of this study was to analyze proteins and mRNA transcripts of genes involved in dopamine biosynthesis (tyrosine hydroxylase; TH) and uptake (dopamine transporter; DAT) with regard to time course (7-90 days) after MPTP lesioning. Molecular analysis using immunohistochemistry and Western immunoblotting techniques demonstrated an increase in striatal TH by 30-60 days postlesioning that returned to near-control (prelesioned) levels by 60-90 days. In situ hybridization histochemistry indicated that this increase in TH protein might be due in part to increased TH mRNA expression in surviving nigrostriatal dopaminergic neurons. Analysis of TH protein at 7, 30, 60, and 90 days postlesioning with two-dimensional polyacrylamide gel electrophoresis in conjunction with Western immunoblotting revealed altered TH protein isoforms migrating at isoelectric points different from those of the native isoform. In contrast to TH protein, which returned to prelesioned levels by 60 days, DAT protein analysis showed that increased expression of striatal DAT protein did not return to near-prelesion levels until 90 days postlesioning. These results suggest that TH and DAT may differ in their time course of expression in surviving dopaminergic neurons and may play a role in mediating the return of striatal dopamine.
...
PMID:Tyrosine hydroxylase and dopamine transporter expression following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurodegeneration of the mouse nigrostriatal pathway. 1511 26

A new serotonin transporter (SERT) ligand, [11C]2-[2-(dimethylaminomethylphenylthio)]-5-fluorophenylamine (10, [11C]AFA), was synthesized and evaluated as a candidate PET radioligand in pharmacological and pharmacokinetic studies. As a PET radioligand, AFA (8) can be labeled with either C-11 or F-18. In vitro, AFA displayed high affinity for SERT (Ki 1.46 +/- 0.15 nM) and lower affinity for norepinephrine transporter (NET, Ki 141.7 +/- 47.4 nM) or dopamine transporter (DAT, Ki > 10,000 nM). [11C]AFA (10) was prepared from its monomethylamino precursor 9 by reaction with high specific activity [11C]methyl iodide. Radiochemical yield was 43 +/- 20% based on [11C]methyl iodide at end of bombardment (EOB, n = 10) and specific activity was 2,129 +/- 1,369 Ci/mmol at end of synthesis (EOS, n = 10). Biodistribution studies in rats indicated that [11C]AFA accumulated in brain regions known to contain high concentrations of SERT. Binding in SERT-rich brain regions was reduced significantly by pretreatment with either the cold compound 8 or with the selective serotonin reuptake inhibitor (SSRI) citalopram, but not by the selective norepinephrine reuptake inhibitor nisoxetine, thus underlining its in vivo binding selectivity and specificity for SERT. Imaging experiments in baboons demonstrated that the uptake pattern of [11C]AFA in the baboon brain is consistent with the known distribution of SERT, with highest activity levels in the midbrain and thalamus, followed by striatum, hippocampus, and cortical regions. Activity levels in the baboon brain peaked at 15-40 min after radioligand injection, indicating a fast uptake kinetics for [11C]AFA. Pretreatment of the baboon with citalopram (4 mg/kg) significantly reduced the specific binding of [11C]AFA in all SERT-containing brain regions. Kinetic analysis revealed that the regional equilibrium specific to non-specific partition coefficients (V3") of [11C]AFA are similar to those of [11C]McN5652, but lower than those of [11C]AFM or [11C]DASB. In summary, [11C]AFA appears to be an appropriate PET radioligand with a fast brain uptake kinetics:
...
PMID:A PET imaging agent with fast kinetics: synthesis and in vivo evaluation of the serotonin transporter ligand [11C]2-[2-dimethylaminomethylphenylthio)]-5-fluorophenylamine ([11C]AFA). 1524 63

Neurotransmitter transporters generate larger currents than expected if one assumes fixed stoichiometry models. It remains controversial, however, whether these depolarizing currents arise from high density and rapid turnover rates of a classical transporter, or whether transporters exhibit bona fide channel behavior. Although heterologously expressed transporters show single-channel behavior and noise analysis in native cells strongly suggests channel behavior, no directly observed single-channel events associated with transporters have been reported thus far in native cells. We describe single-channel events arising directly from the Caenorhabditis elegans dopamine transporter (DAT-1) as evidenced by DA-induced channel activity blocked by a high-affinity DAT-1 inhibitor, increased channel activity in neurons that overexpress DAT-1, and loss of channels in dat-1 knockout neurons. Our data indicate that authentic transporter channels underlie depolarizing whole-cell currents. Thus, DA transporters not only transport DA but also exhibit a channel mode of conduction that directly modulates membrane potential and neuronal function.
...
PMID:Dopamine transporters depolarize neurons by a channel mechanism. 1552 Mar 85

Dopamine (DA) plays roles in circuits that are important for brain reward and in striatal brain regions that are important for certain types of habit learning. These processes in wildtype, heterozygous, and homozygous dopamine transporter knockout (DAT-KO) mice, which were mildly food deprived and allowed to make nose-poke responses for food reinforcement, were studied. The mice were given 20-min sessions of daily (a) baseline exposure to the operant chambers, (b) acquisition of nose-poke responses in which responses were reinforced under a fixed ratio (FR5) schedule, (c) a progressive ratio schedule in which the number of responses required to obtain food was gradually increased, and (d) extinction of responses in which nose pokes were not followed by food. Neither heterozygous nor homozygous DAT-KO mice differed from their wildtype litter mates in the number of nose pokes displayed during baseline exposures to the chambers, the number of sessions required for acquisition, the number of responses under the FR5 schedule, or the number of responses under the progressive ratio schedule. Interestingly, however, in the five extinction sessions in which food was no longer delivered by nose poking, homozygous DAT-KO mice exerted significantly more responses than mice of either of the other two genotypes. These lines of evidence suggest a greater resistance of DAT-KO mice to the elimination of the response and support roles of dopaminergic systems in habit memory.
...
PMID:Food-reinforced operant behavior in dopamine transporter knockout mice: enhanced resistance to extinction. 1554 11

Autoxidation pathways and redox reactions of dihydroxytryptamines (5,6- and 5,7-DHT) and of 6-hydroxydopamine (6-OH-DA) are illustrated, and their potential role in aminergic neurotoxicity is discussed. It is proposed that certain aspects of the cytotoxicity of 6-OH-DA and of the DHTs, namely redox cycling of their quinone- and quinoneimine-intermediates as a source of free radicals, may also apply to quinoidal reactive intermediates and to glutathionyl- or cysteinyl conjugates ("thioether adducts") of o-dihydroxylated (catechol-like) metabolites of certain substituted amphetamines (of methylenedioxymethamphetamine (MDMA) and of methylenedioxyamphetamine (MDA)). Despite similarities in their primary interaction with the plasmalemmal (serotonergic transporter/dopamine transporter, SERT/DAT) and vesicular monoamine transporters (VMAT2), MDMA and fenfluramine (N-ethyl-meta-trifluoromethamphetamine, Fen) differ substantially in many aspects of their metabolism, pharmacokinetics, pharmacology, and neurotoxicology profile; the consequences of these differences for neuronal response patterns and long-term survival prospects are not yet fully understood. However, sustained hyperthermia appears to be a critical factor in these differences. Methodological requirements for adequate detection and description of pre- and postsynaptic forms of drug-induced neurotoxicity are exemplified using recently published accounts. The inclusion of microglial markers into research strategies has widened contemporary pathogenetic concepts on methamphetamine (MA)-induced neurotoxicity as an example of inflammatory neurodegeneration, thus complementing the traditional ROS and RNS-dependent stress models. Amphetamine-type neurotoxicity studies may assist in elaborating of preventive strategies for human neurodegenerative disorders.
...
PMID:Serotonin neurotoxins--past and present. 1563 91

Parkinson's disease (PD) is, to a large extent, specific to the human species. Most symptoms are the consequence of the preferential degeneration of the dopamine-synthesizing cells of the mesostriatal-mesocortical neuronal pathway. Reasons for that can be traced back to the evolutionary mechanisms that shaped the dopamine neurons in humans. In vertebrates, dopamine-containing neurons and nuclei do not exhibit homogenous phenotypes. In this respect, mesencephalic dopamine neurons of the substantia nigra and ventral tegmental area are characterized by a molecular combination (tyrosine hydroxylase, aromatic amino acid decarboxylase, monoamine oxidase, vesicular monoamine transporter, dopamine transporter--to name a few), which is not found in other dopamine-containing neurons of the vertebrate brain. In addition, the size of these mesencephalic DA nuclei is tremendously expanded in humans as compared to other vertebrates. Differentiation of the mesencephalic neurons during development depends on genetic mechanisms, which also differ from those of other dopamine nuclei. In contrast, pathophysiological approaches to PD have highlighted the role of ubiquitously expressed molecules such as a-synuclein, parkin, and microtubule-associated proteins. We propose that the peculiar phenotype of the dopamine mesencephalic neurons, which has been selected during vertebrate evolution and reshaped in the human lineage, has also rendered these neurons particularly prone to oxidative stress, and thus, to the fairly specific neurodegeneration of PD. Numerous evidence has been accumulated to demonstrate that perturbed regulation of DAT-dependent dopamine uptake, DAT-dependent accumulation of toxins, dysregulation of TH activity as well as high sensitivity of DA mesencephalic neurons to oxidants are key components of the neurodegeneration process of PD. This view points to the contribution of nonspecific mechanisms (alpha-synuclein aggregation) in a highly specific cellular environment (the dopamine mesencephalic neurons) and provides a robust framework to develop novel and rational therapeutic schemes in PD.
...
PMID:The degeneration of dopamine neurons in Parkinson's disease: insights from embryology and evolution of the mesostriatocortical system. 1568 11


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---