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Cyclin-dependent kinase 5 phosphorylates serine 31 of tyrosine hydroxylase and regulates its stability

Lily Y Moy1, Li-Huei Tsai

  • 1Department of Pathology and Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA. lily_moy@hms.harvard.edu

The Journal of Biological Chemistry
|October 9, 2004
PubMed

Insights

Cyclin-dependent kinase 5 (cdk5) phosphorylates tyrosine hydroxylase (TH) at serine 31, increasing TH activity and stabilizing TH protein levels. This finding reveals a novel regulatory mechanism for catecholamine biosynthesis in neurons.

Area of Science:

  • Neuroscience
  • Biochemistry
  • Enzymology

Background:

  • Tyrosine hydroxylase (TH) is the key enzyme in catecholamine synthesis.
  • TH activity is regulated by post-translational modifications, including phosphorylation.
  • Cyclin-dependent kinase 5 (cdk5) is crucial for neuronal development and function.

Purpose of the Study:

  • To investigate if TH is a substrate of cdk5.
  • To determine the functional consequences of cdk5-mediated TH phosphorylation.
  • To elucidate the role of cdk5 in regulating TH expression and activity.

Main Methods:

  • In vitro kinase assays to identify TH as a cdk5 substrate.
  • Site-directed mutagenesis to create phosphorylation-defective TH mutants (S31A).
  • Analysis of TH activity, protein levels, and phosphorylation in cdk5 transgenic and knockout mouse models.
  • Immunohistochemistry in mouse substantia nigra.

Main Results:

  • cdk5 directly phosphorylates TH at serine 31.
  • Phosphorylation of TH at Ser-31 by cdk5 increases TH activity.
  • cdk5 and p35 co-expression enhance TH protein stability, leading to increased TH levels.
  • TH protein levels are reduced in cdk5 knockout mice.
  • Phosphorylation-defective TH S31A mutant shows no altered activity or turnover by cdk5.

Conclusions:

  • cdk5-mediated phosphorylation of TH at Ser-31 is a novel regulatory mechanism.
  • This phosphorylation event enhances TH activity and stabilizes TH protein.
  • cdk5 plays a significant role in regulating catecholamine biosynthesis through TH.

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