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α-Synuclein activation of protein phosphatase 2A reduces tyrosine hydroxylase phosphorylation in dopaminergic cells

2005; The Company of Biologists; Volume: 118; Issue: 15 Linguagem: Inglês

10.1242/jcs.02481

1477-9137

Xiangmin Peng, Roya Tehranian, Paula Dietrich, Leonidas Stefanis, Ruth G. Perez,

Nuclear Receptors and Signaling

α-Synuclein is an abundant presynaptic protein implicated in neuronal plasticity and neurodegenerative diseases. Although the function of α-synuclein is not thoroughly elucidated, we found that α-synuclein regulates dopamine synthesis by binding to and inhibiting tyrosine hydroxylase, the rate limiting enzyme in dopamine synthesis. Understanding α-synuclein function in dopaminergic cells should add to our knowledge of this key protein, which is implicated in Parkinson's disease and other disorders. Herein, we report a mechanism by which α-synuclein diminishes tyrosine hydroxylase phosphorylation and activity in stably transfected dopaminergic cells. Short-term regulation of tyrosine hydroxylase depends on the phosphorylation of key seryl residues in the amino-terminal regulatory domain of the protein. Of these, Ser40 contributes significantly to tyrosine hydroxylase activation and dopamine synthesis. We observed that α-synuclein overexpression caused reduced Ser40 phosphorylation in MN9D cells and inducible PC12 cells. Ser40 is phosphorylated chiefly by the cyclic AMP-dependent protein kinase PKA and dephosphorylated almost exclusively by the protein phosphatase, PP2A. Therefore, we measured the impact of α-synuclein overexpression on levels and activity of PKA and PP2A in our cells. PKA was unaffected by α-synuclein. PP2A protein levels also were unchanged, however, the activity of PP2A increased in parallel with α-synuclein expression. Inhibition of PP2A dramatically increased Ser40 phosphorylation only in α-synuclein overexpressors in which α-synuclein was also found to co-immunoprecipitate with PP2A. Together the data reveal a functional interaction between α-synuclein and PP2A that leads to PP2A activation and underscores a key role for α-synuclein in protein phosphorylation.