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J Cell Sci. 2005 Aug 1;118(Pt 15):3523-30. Epub 2005 Jul 19.

Alpha-synuclein activation of protein phosphatase 2A reduces tyrosine hydroxylase phosphorylation in dopaminergic cells.

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1
Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.

Erratum in

  • J Cell Sci. 2005 Sep 1;118(Pt 17):4073. Peng, Xiangmin M [corrected to Peng, Xiangmin].

Abstract

alpha-Synuclein is an abundant presynaptic protein implicated in neuronal plasticity and neurodegenerative diseases. Although the function of alpha-synuclein is not thoroughly elucidated, we found that alpha-synuclein regulates dopamine synthesis by binding to and inhibiting tyrosine hydroxylase, the rate limiting enzyme in dopamine synthesis. Understanding alpha-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 alpha-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 alpha-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 alpha-synuclein overexpression on levels and activity of PKA and PP2A in our cells. PKA was unaffected by alpha-synuclein. PP2A protein levels also were unchanged, however, the activity of PP2A increased in parallel with alpha-synuclein expression. Inhibition of PP2A dramatically increased Ser40 phosphorylation only in alpha-synuclein overexpressors in which alpha-synuclein was also found to co-immunoprecipitate with PP2A. Together the data reveal a functional interaction between alpha-synuclein and PP2A that leads to PP2A activation and underscores a key role for alpha-synuclein in protein phosphorylation.

PMID:
16030137
DOI:
10.1242/jcs.02481
[Indexed for MEDLINE]
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