Effect of alpha-synuclein on the promoter activity of tyrosine hydroxylase gene.

Objective: To approach the associated mechanism by which alpha-synuclein (alpha-Syn) might regulate the metabolism of dopamine.

Methods: A DNA fragment, located at -495 to +25 of the human tyrosine hydroxylase (TH) gene, was amplified by PCR and inserted into the pGL(3)-Basic luciferase reporter vector. The recombinant plasmid pGL(3)-THprom was transfected into a dopaminergic cell line MES23.5 or a alpha-Syn over-expressed MES23.5 (named MES23.5/halpha-Syn(+)). The promoter activity was detected by the Dual Luciferase Assay System.

Results: The luciferase activities in the MES23.5 cells transfected with pGL(3)-Basic, pGL(3)-THprom, and pGL(3)-Control vectors were 5.60+/-0.67, 26.80+/-4.11, and 32.90+/-4.75, respectively. On the other hand, the luciferase activity of pGL(3)-THprom in the MES23.5 (26.80+/-4.11) was significantly higher than that in the MES23.5/halpha-Syn(+) (14.40+/-0.61) (P<0.01).

Conclusion: These results indicate that the - 495 to +25 region in the TH gene possesses promoter activity for controlling the gene expression, and that alpha-Syn may negatively regulate the metabolism of dopamine by affecting the function of TH promoter as a trans-acting factor.