title: Silencing alpha-synuclein gene expression enhances tyrosine hydroxylase activity in MN9D cells.
abstract: 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.
authors: 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.
authors: Dongmei
authors: D
authors: Liu
authors: Ling
authors: L
authors: Jin
authors: Hao
authors: H
authors: Wang
authors: Huanying
authors: H
authors: Zhao
authors: Chunli
authors: C
authors: Zhao
authors: Chunli
authors: C
authors: Duan
authors: Lingling
authors: L
authors: Lu
authors: Bo
authors: B
authors: Wu
authors: Shun
authors: S
authors: Yu
authors: Piu
authors: P
authors: Chan
authors: Yaohua
authors: Y
authors: Li
authors: Hui
authors: H
authors: Yang
mesh_terms: 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
chemical_list: D051844:alpha-Synuclein; D007980:Levodopa; D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine