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

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.

Pubmed ID: 16030137

Authors

  • Peng X
  • Peng XM
  • Tehranian R
  • Dietrich P
  • Stefanis L
  • Perez RG

Journal

Journal of cell science

Publication Data

August 1, 2005

Associated Grants

  • Agency: NINDS NIH HHS, Id: NS42094

Mesh Terms

  • Animals
  • Cell Line
  • Dopamine
  • Gene Expression Regulation
  • Mice
  • Mice, Inbred C57BL
  • Okadaic Acid
  • PC12 Cells
  • Phosphoprotein Phosphatases
  • Phosphorylation
  • Protein Phosphatase 2
  • Rats
  • Serine
  • Tyrosine 3-Monooxygenase