Comparative analyses of α-synuclein expression levels in rat brain tissues and transfected cells

Abstract

α-Synuclein may have a role in the genesis of Parkinson's disease (PD) and other neurodegenerative diseases, and overexpression of α-synuclein in endogenously expressing systems and transfected cell lines has been linked to its cytotoxicity. Because there is no definition of what constitutes normal or high expression levels of α-synuclein, the current studies were undertaken. Protein levels of α-synuclein, and its binding partner, the dopamine transporter (DAT), were examined and semi-quantified in different rat brain regions and compared to the amounts of α-synuclein expressed in L tk − cells after transfection with known amounts of DNA. Of the regions tested, α-synuclein expression was lowest in dopamine-producing brain areas, substantia nigra and ventral tegmental area; conversely, the expression of DAT was the highest in these tissues. Areas that do not normally degenerate in PD, such as cerebellum, nucleus accumbens and thalamus, expressed the highest levels of α-synculein and very low DAT. Expression of DAT and α-synuclein to levels similar to those observed in rat substantia nigra were obtained after transfection of L tk − cells with 1–2 μg each of α-synuclein and DAT DNAs, indicating that such transfection conditions produce normal expression levels of these proteins.