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Does the M-Phase Promoting Factor (MPF) Activate a Major Ca
Jean Claude Labbe1, André Picard1,2, Marcel Doree1
1INSERM U. 249 and CNRS-CRBM, BP 5015, 34033 Montpllier Cedex, FRANCE.
Development, Growth & Differentiation
|June 7, 2023
Summary
In starfish, inhibiting dephosphorylation activates a key cell cycle protein kinase. This suggests a regulatory protein, possibly maturation-promoting factor (MPF), controls kinase activity during cell division.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- A major Ca2+- and cyclic nucleotide-independent protein kinase activity fluctuates with maturation-promoting factor (MPF) during the cell cycle in starfish.
- Understanding the regulation of this kinase is crucial for comprehending cell cycle progression.
Purpose of the Study:
- To investigate the regulatory mechanisms controlling the activity of a major M-phase-specific protein kinase in starfish oocytes.
- To determine if protein phosphorylation or dephosphorylation plays a key role in kinase activation.
Main Methods:
- Microinjection of starfish oocytes with a phosphatase inhibitor (α-naphthylphosphate).
- Microinjection of oocytes with cytoplasm from oocytes at different cell cycle stages or with specific treatments.
- Assaying protein kinase activity in oocyte homogenates.
Main Results:
- Inhibiting dephosphorylation with α-naphthylphosphate significantly increased major cycling kinase activity.
- Cytoplasm containing active kinase but no MPF did not activate the kinase in recipient oocytes.
- Cytoplasm containing MPF (with or without high kinase activity) induced kinase activation in recipient oocytes.
Conclusions:
- Inhibiting dephosphorylation of a regulatory protein activates the M-phase-specific protein kinase.
- Maturation-promoting factor (MPF) is a potential candidate for this regulatory protein, linking MPF to kinase activation during cell division.
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