1-Methyl-4-phenylpyridinium-induced down-regulation of dopamine transporter function correlates with a reduction in dopamine transporter cell surface expression.
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.
Department of Pharmacology, University of North Dakota School of Medicine and Health Sciences, Grand Forks 58202, USA.
Jaturaporn
J
Chagkutip
Roxanne A
RA
Vaughan
Piyarat
P
Govitrapong
Manuchair
M
Ebadi
D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D006801:Humans; D007668:Kidney / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism*; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D021381:Protein Transport / Q000502:physiology; D013223:Statistics as Topic; D014018:Tissue Distribution
D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493214:SLC6A3 protein, human; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine