Human alpha-synuclein over-expression increases intracellular reactive oxygen species levels and susceptibility to dopamine.
alpha-Synuclein is a major component of Lewy bodies found in the brains of patients with Parkinson's disease (PD). Two point mutations in alpha-synuclein (A53T and A30P) are identified in few families with dominantly inherited PD. Yet the mechanism by which this protein is involved in nigral cell death remains poorly understood. Mounting evidence suggests the importance of oxidative stress in the pathogenesis of PD. Here we investigated the effects of wild-type and two mutant forms of alpha-synuclein on intracellular reactive oxygen species (ROS) levels using clonal SH-SY5Y cells engineered to over-express these proteins. All three cell lines, and particularly mutant alpha-synuclein-expressing cells, had increased ROS levels relative to control LacZ-engineered cells. In addition, cell viability was significantly curtailed following the exposure of all three alpha-synuclein-engineered cells to dopamine, but more so with mutant alpha-synuclein. These results suggest that over-expression of alpha-synuclein, and especially its mutant forms, exaggerates the vulnerability of neurons to dopamine-induced cell death through excess intracellular ROS generation. Thus, these findings provide a link between mutations or over-expression of alpha-synuclein and apoptosis of dopaminergic neurons by lowering the threshold of these cells to oxidative damage.
Junn
Eunsung
E
Genetic Pharmacology Unit, Experimental Therapeutics Branch, NINDS, National Institutes of Health, Bethesda, MD 20892-1406, USA.
Mouradian
M Maral
MM
D016923:Cell Death / Q000187:drug effects / Q000235:genetics*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D017930:Genes, Reporter; D006801:Humans; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics*; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D017354:Point Mutation / Q000502:physiology; D020033:Protein Isoforms; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology; D051843:Synucleins; D051844:alpha-Synuclein
D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D017382:Reactive Oxygen Species; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; D004298:Dopamine