Related Experiment Video
Updated: May 27, 2025
Spatial and Temporal Analysis of Active ERK in the C. elegans Germline
Published on: November 29, 2016
The MAST kinase KIN-4 carries out mitotic entry functions of Greatwall in C. elegans
Ludivine Roumbo1,2, Batool Ossareh-Nazari1,2, Suzanne Vigneron3
1Université Paris cité, CNRS, Institut Jacques Monod, F-75013, Paris, France.
Abstract:
MAST-like, or Greatwall (Gwl), an atypical protein kinase related to the evolutionarily conserved MAST kinase family, is crucial for cell cycle control during mitotic entry. Mechanistically, Greatwall is activated by Cyclin B-Cdk1 phosphorylation of a 550 amino acids-long insertion in its atypical activation segment. Subsequently, Gwl phosphorylates Endosulfine and Arpp19 to convert them into inhibitors of PP2A-B55 phosphatase, thereby preventing early dephosphorylation of M-phase targets of Cyclin B-Cdk1. Here, searching for an elusive Gwl-like activity in C. elegans, we show that the single worm MAST kinase, KIN-4, fulfills this function in worms and can functionally replace Greatwall in the heterologous Xenopus system. Compared to Greatwall, the short activation segment of KIN-4 lacks a phosphorylation site, and KIN-4 is active even when produced in E. coli. We also show that a balance between Cyclin B-Cdk1 and PP2A-B55 activity, regulated by KIN-4, is essential to ensure asynchronous cell divisions in the early worm embryo. These findings resolve a long-standing puzzle related to the supposed absence of a Greatwall pathway in C. elegans, and highlight a novel aspect of PP2A-B55 regulation by MAST kinases.
Insights
The Greatwall (Gwl) kinase pathway, essential for cell division, is present in C. elegans as KIN-4. This MAST kinase regulates PP2A-B55 phosphatase activity, ensuring proper embryonic cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- The Greatwall (Gwl) kinase is a key regulator of cell cycle progression during mitosis.
- Gwl controls mitotic entry by phosphorylating targets that inhibit the PP2A-B55 phosphatase.
- The existence of a Gwl-like pathway in C. elegans remained elusive.
Purpose of the Study:
- To identify and characterize the Gwl-like activity in C. elegans.
- To investigate the function of the MAST kinase KIN-4 in cell cycle regulation.
- To understand the role of KIN-4 in regulating PP2A-B55 activity and embryonic development.
Main Methods:
- Functional analysis of C. elegans KIN-4 in vivo and in heterologous systems.
- Biochemical characterization of KIN-4 activity.
- Investigation of KIN-4's role in regulating Cyclin B-Cdk1 and PP2A-B55 balance during early embryogenesis.
Main Results:
- The C. elegans MAST kinase KIN-4 possesses Gwl-like activity and can functionally replace Xenopus Gwl.
- KIN-4 has a distinct activation mechanism compared to Gwl, lacking a key phosphorylation site.
- KIN-4 activity is essential for maintaining the balance between Cyclin B-Cdk1 and PP2A-B55, crucial for asynchronous cell divisions in early C. elegans embryos.
Conclusions:
- This study identifies KIN-4 as the C. elegans ortholog of Gwl, resolving a long-standing question.
- MAST kinases, including KIN-4, play a conserved role in regulating PP2A-B55 phosphatase activity.
- KIN-4's function is critical for proper embryonic cell division timing in C. elegans.
Related Concept Videos
02:15M-Cdk Drives Transition Into Mitosis
Cyclin-dependent kinases, or Cdks, work in concert with cyclins to control cell cycle transitions. M-Cdk, a complex of Cdk1 bound to M cyclin, is a well-known example of this coordinated control that drives the transition from the G2 to the M phase.
M cyclin...
01:07MAPK Signaling Cascades
02:38Mitogens and the Cell Cycle
02:19The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
02:39Positive Regulator Molecules
00:50Anaphase Promoting Complex