MPP + toxicity and plasma membrane dopamine transporter: study using cell lines expressing the wild-type and mutant rat dopamine transporters

Abstract

The Parkinsonism-inducing neurotoxin 1-methyl-4-phenylpyridinium (MPP +) causes specific cell death in dopaminergic neurons after accumulation by the dopamine transporter (DAT). COS cells, a non-neuronal cell line insensitive to high doses of MPP +, becomes sensitive to MPP + when transfected with the rat DAT cDNA. We analyzed the bi-directional transport of MPP + and its toxicity in several cell lines expressing wild or mutant DATs. Cell death in COS cells expressing wild DAT by exposure to MPP + was concentration-dependent and cocaine-reversible. Increased wild DAT expression caused higher sensitivities to the toxin in HeLa cells. Although several mutant DATs demonstrated greater transport activity than the wild-type, they displayed similar or lower sensitivity to MPP + toxicity. Reverse transport of preloaded [ 3H]MPP + through DAT was facilitated in COS cells expressing certain mutant DATs, which consistently displayed less sensitivity to MPP + toxicity. These results suggest that re-distribution of MPP + due to influx/efflux turnover through the transporter is a key factor in MPP + toxicity.