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.
Chagkutip
Jaturaporn
J
Department of Pharmacology, University of North Dakota School of Medicine and Health Sciences, Grand Forks 58202, USA.
Vaughan
Roxanne A
RA
Govitrapong
Piyarat
P
Ebadi
Manuchair
M
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