Silencing alpha-synuclein gene expression enhances tyrosine hydroxylase activity in MN9D cells.
alpha-Synuclein has been implicated in the pathogenesis of Parkinson's disease (PD). Previous studies have shown that alpha-synuclein is involved in the regulation of dopamine (DA) metabolism, possibly by down-regulating the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in DA biosynthesis. In this study, we constructed alpha-synuclein stably silenced MN9D/alpha-SYN(-) cells by vector mediated RNA interference and examined its effects on DA metabolism. We found that there were no significant differences in TH protein and mRNA levels between MN9D, MN9D/alpha-SYN(-) and MN9D/CON cells, suggesting that silencing alpha-synuclein expression does not affect TH gene expression. However, significant increases in phosphorylated TH, cytosolic 3, 4-dihydroxyphenylalanine (L-DOPA) and DA levels were observed in MN9D/alpha-SYN(-) cells. Our data show that TH activity and DA biosynthesis were enhanced by down-regulation of alpha-synuclein, suggesting that alpha-synuclein may act as a negative regulator of cytosolic DA. With respect to PD pathology, a loss of functional alpha-synuclein may result in increased DA levels in neurons that may lead to cell injury or even death.
Liu
Dongmei
D
Beijing Institute for Neuroscience, Beijing Center of Neural Regeneration and Repair, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Capital Medical University, Beijing 100069, China.
Jin
Ling
L
Wang
Hao
H
Zhao
Huanying
H
Zhao
Chunli
C
Duan
Chunli
C
Lu
Lingling
L
Wu
Bo
B
Yu
Shun
S
Chan
Piu
P
Li
Yaohua
Y
Yang
Hui
H
D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D006801:Humans; D007980:Levodopa / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis* / Q000235:genetics; D051844:alpha-Synuclein / Q000096:biosynthesis* / Q000235:genetics
D051844:alpha-Synuclein; D007980:Levodopa; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine