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A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
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PP1-mediated dephosphorylation of phosphoproteins at mitotic exit is controlled by inhibitor-1 and PP1

Judy Qiju Wu1, Jessie Yanxiang Guo, Wanli Tang

  • 1Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.

Nature Cell Biology
|April 28, 2009
PubMed

Insights

Protein phosphatase-1 (PP1) deactivates mitotic proteins. Its activation requires dephosphorylation of Cdc2 and inhibitor-1, enabling mitotic exit.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitotic exit requires the loss of cell division cycle 2 (Cdc2/Cdk1) kinase activity.
  • Dephosphorylation of proteins phosphorylated by Cdc2 is essential for mitotic exit.
  • Protein phosphatase-1 (PP1) is a key enzyme in dephosphorylation processes.

Purpose of the Study:

  • To identify the primary phosphatase responsible for dephosphorylating mitotic phosphoproteins.
  • To elucidate the regulatory mechanisms controlling PP1 activity during mitotic exit.

Main Methods:

  • Investigated the role of PP1 in mitotic phosphoprotein dephosphorylation.
  • Examined the regulation of PP1 by Cdc2 and inhibitor-1 during mitosis.
  • Utilized biochemical assays to study protein phosphorylation and dephosphorylation events.

Main Results:

  • PP1 was identified as the main catalyst for dephosphorylating mitotic phosphoproteins.
  • PP1 activity is suppressed in early mitosis by Cdc2 phosphorylation and inhibitor-1 binding.
  • PP1 activation occurs through a sequential dephosphorylation process involving Cdc2 and inhibitor-1, leading to mitotic exit.

Conclusions:

  • Cdc2 plays a dual role by phosphorylating substrates and inhibiting their PP1-mediated dephosphorylation.
  • The coordinated action of Cdc2, inhibitor-1, and PP1 is crucial for timely mitotic exit.
  • Understanding PP1 regulation provides insights into cell cycle control and potential therapeutic targets.

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