GSK3 beta mediates acentromeric spindle stabilization by activated PKC zeta

Area of Science:

• Cell Biology
• Reproductive Biology
• Molecular Biology

Background:

• Mammalian egg fertilization involves precise signaling events for zygote formation.
• Mouse eggs arrested at meiotic metaphase II (MII) are acentrosomal.
• The MII meiotic spindle acts as a scaffold for signaling pathways regulating post-fertilization events.

Purpose of the Study:

• To investigate the role of phosphorylated Protein Kinase C zeta (p-PKC zeta) and Glycogen Synthase Kinase 3beta (GSK3 beta) in MII spindle organization.
• To elucidate the mechanism by which p-PKC zeta influences spindle stability.

Main Methods:

• Immunopurification of p-PKC zeta from MII eggs.
• Co-localization studies using immunofluorescence and Fluorescence Resonance Energy Transfer (FRET).
• Analysis of protein interactions at acentrosomal spindle poles and kinetochore regions.

Main Results:

• p-PKC zeta and GSK3 beta were found enriched at acentrosomal spindle poles and kinetochores in MII eggs.
• p-PKC zeta co-localized with GSK3 beta and Partition deficit protein 6 (Par6), known microtubule stabilizers.
• Evidence suggests p-PKC zeta phosphorylates GSK3 beta at the ser9 position, inhibiting its activity.

Conclusions:

• p-PKC zeta plays a crucial role in maintaining meiotic spindle stability in mammalian eggs.
• The mechanism involves the inactivation of GSK3 beta via phosphorylation at ser9 by p-PKC zeta.
• This regulation ensures spindle organization during meiotic metaphase arrest, critical for successful fertilization.