MPP+ iodide (N-Methyl-4-Phenylpyridinium Iodide), the metabolite of a neurotoxin MPTP, causes symptom of Parkinson’s disease (PD) in animal models by selectively destroying dopaminergic neurons in substantia nigra. MPP+ induces autophagic cell death in SH-SY5Y cells. MPP+ induces dopamine transporter (DAT) externalization in dopaminergic (DA) neurons, but internalization of serotonin transporter (SERT) in serotonergic (5-HT) neurons.