1-Methyl-4-phenylpyridinium (MPP+), the toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, induces apoptosis in cerebellar granule neurons (CGNs). We have tested the hypothesis that organic cation transporter (OCT) 3 mediates the accumulation and, hence, the toxicity of MPP+ in CGNs. CGNs in primary culture express OCT3 but do not express mRNA for OCT1, OCT2 or the dopamine transporter. Cerebellar astrocytes are negative for OCT3 protein by immunocytochemistry. [3H]MPP+ accumulation by CGNs exhibits first-order kinetics, and a Kt value of 5.3 ± 1.2 μM and a Tmax of 0.32 ± 0.02 pmol per min per 106 cells. [3H]MPP+ accumulation is inhibited by corticosterone, β-estradiol and decynium 22 with Ki values of 0.25 μM, 0.17 μM and 4.0 nM respectively. [3H]MPP+ accumulation is also inhibited by desipramine, dopamine, serotonin and norepinephrine, but is not affected by carnitine (10 mM), mazindol (9 μM) or GBR 12909 (1 μM). MPP+-induced caspase-3-like activation and cell death are prevented by pretreatment with 5 μM β-estradiol. In contrast, the neurotoxic effects of rotenone are unaffected by β-estradiol. Interestingly, GBR 12909 protects CGNs from both MPP+ and rotenone toxicity. In summary, CGNs accumulate MPP+ in manner that is consistent with uptake via OCT3 and the presence of this protein in CGNs explains their sensitivity to MPP+ toxicity.
- 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)
- GBR 12909
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience