Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.64 (MPP)
 1,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The plasma membrane dopamine transporter is located on presynaptic nerve terminals and is responsible for the termination of dopaminergic neurotransmission via dopamine reuptake. The dopamine transporter may also contribute to the pathogenesis of Parkinson disease. Dopamine transporter expression correlates well with susceptibility to neuronal degeneration in 1-methyl-4-phenyl-1,2,3,6 -tetrahydropyridine (MPTP)-induced parkinsonism. Recent studies have implicated the dopamine transporter in the uptake of both this neurotoxin and its metabolite, MPP(+), as well as another experimental neurotoxin, 6-hydroxydopamine. In these studies we examined the role of the dopamine transporter in the neurotoxicity of both MPP(+) and 6-hydroxydopamine in the rat brain using in vivo administration of phosphorothioate antisense oligonucleotides targeting dopamine transporter mRNA. Infusion of dopamine transporter antisense (1 nmol/day, 7 days) into the left substantia nigra pars compacta resulted in reduced (3)H-WIN 35-428 binding in the left striatum and significant levodopa and amphetamine-induced contralateral rotations. Unilateral pretreatment with dopamine transporter antisense prior to bilateral intrastriatal infusion of either MPP(+) or 6-hydroxydopamine resulted in asymmetrical striatal (3)H-WIN 35-428 binding and dopamine content as well as significant apomorphine-induced ipsilateral rotations, suggesting neuroprotection of nigrostriatal neurons on the antisense-treated side. Thus, the dopamine transporter appears to play a critical role in determining susceptibility to the experimental neurotoxins MPP(+) and 6-hydroxydopamine. In light of this, the dopamine transporter may prove useful, both as a marker for susceptibility to Parkinson's disease and as a target for therapeutic intervention.
 ...
PMID:Dopamine transporter function assessed by antisense knockdown in the rat: protection from dopamine neurotoxicity. 1088 Oct 39

The mechanisms whereby 1-methyl-4-phenylpyridinium (MPP(+)) mediates cell death and Parkinsonism are still unclear. We have shown that dopamine transporter (DAT) is required for MPP(+)-mediated cytotoxicity in HEK-293 cells stably transfected with human DAT. Furthermore, MPP(+) produced a concentration- and time-dependent reduction in the uptake of [3H]dopamine. We observed a significant decrease in [3H]WIN 35428 binding in the intact cells with MPP(+). The saturation analysis of the [3H]WIN 35428 binding obtained from total membrane fractions revealed a decrease in the transporter density (B(max)) with an increase in the dissociation equilibrium constant (K(d)) after MPP(+) treatment. Furthermore, biotinylation assays confirmed that MPP(+) reduced both plasma membrane and intracellular DAT immunoreactivity. Taken together, these findings suggest that the reduction in cell surface DAT protein expression in response to MPP(+) may be a contributory factor in the down-regulation of DAT function while enhanced lysosomal degradation of DAT may signal events leading to cellular toxicity.
 ...
PMID:1-Methyl-4-phenylpyridinium-induced down-regulation of dopamine transporter function correlates with a reduction in dopamine transporter cell surface expression. 1457 93