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Updated: Aug 18, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
12:26

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

MAP1B phosphorylation is differentially regulated by Cdk5/p35, Cdk5/p25, and JNK

Takeshi Kawauchi1, Kaori Chihama, Yoshiaki V Nishimura

  • 1Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.

Biochemical and Biophysical Research Communications
|April 23, 2005
PubMed

Insights

Mode I phosphorylation of MAP1B in the brain is primarily driven by JNK in development, not Cdk5/p35. Pathogenic brains utilize Cdk5/p25 for this phosphorylation, impacting biological events.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Cell Biology

Background:

  • Mode I phosphorylated MAP1B is present in both developing and diseased brains.
  • Cyclin-dependent kinase 5 (Cdk5) was previously thought to phosphorylate MAP1B in the developing cerebral cortex.

Purpose of the Study:

  • To investigate the specific kinases responsible for Mode I phosphorylation of MAP1B in the developing cerebral cortex.
  • To elucidate the role of Cdk5/p35 versus Cdk5/p25 in MAP1B phosphorylation.
  • To understand the involvement of Cdk5 in microtubule dynamics and neuronal migration.

Main Methods:

  • Inhibition studies using Cdk5 and JNK inhibitors in primary and slice cultures.
  • Co-transfection experiments with Cdk5, p35, and p25 in COS7 cells.
  • Primary culture studies to assess Cdk5's role in microtubule dynamics.
  • In utero electroporation to demonstrate the importance of microtubule dynamics in neuronal migration.

Main Results:

  • Cdk5 inhibition did not suppress Mode I MAP1B phosphorylation, while JNK inhibition did.
  • Cdk5/p35 did not increase MAP1B phosphorylation in COS7 cells, but Cdk5/p25 did.
  • Cdk5 was involved in regulating microtubule dynamics but not MAP1B phosphorylation in primary cultures.
  • Microtubule dynamics are crucial for neuronal migration.

Conclusions:

  • Mode I phosphorylation of MAP1B is mediated by JNK, not Cdk5/p35, in the developing cerebral cortex.
  • Cdk5/p25 facilitates Mode I MAP1B phosphorylation in pathogenic brains.
  • Cdk5 plays a role in microtubule dynamics independent of MAP1B phosphorylation, impacting neuronal migration.

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