Effect of mutant alpha-synuclein on dopamine homeostasis in a new human mesencephalic cell line.
Mutations in alpha-synuclein have been linked to rare, autosomal dominant forms of Parkinson's disease. Despite its ubiquitous expression, mutant alpha-synuclein primarily leads to the loss of dopamine-producing neurons in the substantia nigra. alpha-Synuclein is a presynaptic nerve terminal protein of unknown function, although several studies suggest it is important for synaptic plasticity and maintenance. The present study utilized a new human mesencephalic cell line, MESC2.10, to study the effect of A53T mutant alpha-synuclein on dopamine homeostasis. In addition to expressing markers of mature dopamine neurons, differentiated MESC2.10 cells are electrically active, produce dopamine, and express wild-type human alpha-synuclein. Lentivirus-induced overexpression of A53T mutant alpha-synuclein in differentiated MESC2.10 cells resulted in down-regulation of the vesicular dopamine transporter (VMAT2), decreased potassium-induced and increased amphetamine-induced dopamine release, enhanced cytoplasmic dopamine immunofluorescence, and increased intracellular levels of superoxide. These results suggest that mutant alpha-synuclein leads to an impairment in vesicular dopamine storage and consequent accumulation of dopamine in the cytosol, a pathogenic mechanism that underlies the toxicity of the psychostimulant amphetamine and the parkinsonian neurotoxin 1-methyl-4-phenylpyridinium. Interestingly, cells expressing A53T mutant alpha-synuclein were resistant to amphetamine-induced toxicity. Because extravesicular, cytoplasmic dopamine can be easily oxidized into reactive oxygen species and other toxic metabolites, mutations in alpha-synuclein might lead to Parkinson's disease by triggering protracted, low grade dopamine toxicity resulting in terminal degeneration and ultimately cell death.
Lotharius
Julie
J
Section for Neuronal Survival, Wallenberg Neuroscience Center, Lund University, Lund 221 84, Sweden. julie.lotharius@mphy.lu.se
Barg
Sebastian
S
Wiekop
Pia
P
Lundberg
Cecilia
C
Raymon
Heather K
HK
Brundin
Patrik
P
D000662:Amphetamines / Q000494:pharmacology; D015415:Biomarkers; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000033:anatomy & histology; D018014:Gene Transfer Techniques; D006706:Homeostasis; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology* / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D010300:Parkinson Disease / Q000235:genetics; D018408:Patch-Clamp Techniques; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D051843:Synucleins; D051844:alpha-Synuclein
D000662:Amphetamines; D015415:Biomarkers; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; D013481:Superoxides; D004298:Dopamine