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Updated: Nov 23, 2025

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Published on: May 3, 2018
The PHLPP1 N-Terminal Extension Is a Mitotic Cdk1 Substrate and Controls an Interactome Switch
Agnieszka T Kawashima1,2, Cassandra Wong3, Gema Lordén1
1Department of Pharmacology, University of California, San Diego, California, USA.
PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) is regulated during mitosis. Its phosphorylation controls binding to mitotic proteins, ensuring accurate cell division and supporting its tumor suppressor role.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) acts as a tumor suppressor by dephosphorylating Akt.
- The molecular mechanisms regulating PHLPP1 activity, particularly during the cell cycle, remain largely uncharacterized.
Purpose of the Study:
- To investigate the cell cycle-dependent regulation of PHLPP1.
- To elucidate the role of PHLPP1 phosphorylation and its interaction partners during mitosis.
Main Methods:
- Cell cycle analysis to assess mitotic delays and chromosomal segregation errors.
- Proximity-dependent biotin identification (BioID) to identify PHLPP1 interacting proteins during mitosis.
- Site-directed mutagenesis to study the role of the N-terminal extension (NTE).
Main Results:
- PHLPP1 undergoes cell cycle-dependent regulation, with deletion causing mitotic delays and increased chromosomal segregation errors.
- PHLPP1 is hyperphosphorylated during mitosis by Cdk1 within its N-terminal extension (NTE).
- Mitotic PHLPP1 dissociates from plasma membrane scaffolds (e.g., Scribble) and interacts with kinetochore/mitotic spindle proteins (e.g., KNL1, TPX2) in an NTE-dependent manner.
Conclusions:
- Mitotic phosphorylation of PHLPP1 by Cdk1 regulates its binding to mitotic partners, facilitating accurate cell cycle progression.
- These findings reveal a novel mechanism for PHLPP1 regulation and suggest its role in maintaining genomic stability, relevant to its tumor-suppressive function.
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