title: Differential effects of overexpression of wild-type and mutant human alpha-synuclein on MPP+-induced neurotoxicity in PC12 cells.
abstract: The genetic background and the pathogenesis of familial Parkinson's disease (PD) have not been fully elucidated. Two missense mutations in the alpha-synuclein gene, A30P and A53T, have been linked to familial PD. Increasing evidence suggests the involvement of alpha-synuclein, the dopamine transporter (DAT), and neurotoxins in the pathogenesis of PD, but their relationships to the death of nigral cells remains poorly understood. In the present study, we used the PC12 cell line, a well recognized model of the nigral cell, to investigate the effects of overexpression of wild-type (WT) and mutant human alpha-synuclein on MPP+-induced neurotoxicity. We found that overexpression of mutant alpha-synuclein enhanced the toxicity of MPP+ to PC12 cells and elevated intracellular reactive oxygen species (ROS) levels, whereas overexpression of WT alpha-synuclein protected PC12 cells against MPP+ toxicity and lowered ROS levels. Furthermore, assays of 131I-FP-beta-CIT binding with DAT membrane fractions showed that WT and mutant alpha-synuclein had different effects on the expression of DAT on the cell membrane following exposure to MPP+. WT alpha-synuclein reduced the toxic effect of MPP+ by facilitating DAT internalization, while both A30P and A53T alpha-synuclein aggravated the toxic effect of MPP+ by reducing DAT internalization. These data indicate that alpha-synuclein regulates ROS levels and DAT surface expression in dopaminergic neurons, and thus changes the response of these cells to MPP+.
authors.affiliation: Department of Neurology, Second Affiliated Hospital of Soochow University, 1055 Sanxiang Road, Suzhou 215004, China.
authors.forename: Jin-Jun
authors.initials: JJ
authors.lastname: Qian
authors.forename: Yan-Bo
authors.initials: YB
authors.lastname: Cheng
authors.forename: Ya-Ping
authors.initials: YP
authors.lastname: Yang
authors.forename: Cheng-Jie
authors.initials: CJ
authors.lastname: Mao
authors.forename: Zheng-Hong
authors.initials: ZH
authors.lastname: Qin
authors.forename: Kai
authors.initials: K
authors.lastname: Li
authors.forename: Chun-Feng
authors.initials: CF
authors.lastname: Liu
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology*; D000818:Animals; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007381:Intermediate Filament Proteins / Q000235:genetics* / Q000378:metabolism; D008970:Molecular Weight; D009154:Mutation / Q000502:physiology*; D009498:Neurotoxins / Q000494:pharmacology*; D016716:PC12 Cells / Q000187:drug effects* / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D014162:Transfection / Q000379:methods; D014326:Tropanes / Q000378:metabolism
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D007381:Intermediate Filament Proteins; D009498:Neurotoxins; D017382:Reactive Oxygen Species; D014326:Tropanes; C430456:desmuslin; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine