The ARP2/3 complex prevents excessive formin activity during cytokinesis

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Cytokinesis, the final stage of cell division, relies on an actomyosin contractile ring.
• Actin filament nucleation is crucial for forming the contractile ring and cortical actin networks.
• The formin CYK-1 and the ARP2/3 complex are major actin nucleators with distinct roles.

Purpose of the Study:

• To investigate the roles of formin CYK-1 and the ARP2/3 complex in regulating actin networks during Caenorhabditis elegans embryo cytokinesis.
• To determine how these nucleators influence the kinetics and architecture of the contractile ring and cortex.

Main Methods:

• Depletion of CYK-1 and ARP2 subunit in C. elegans embryos.
• Inhibition of ARP2/3 complex activity.
• Live imaging to observe F-actin dynamics and contractile ring progression.

Main Results:

• CYK-1 is essential for maintaining F-actin levels in the contractile ring and its constriction rate.
• ARP2/3 complex, though not localized to the ring, is required for timely ring formation and constriction.
• Depletion of ARP2/3 complex leads to excess formin-nucleated actin, suggesting negative regulation of CYK-1.

Conclusions:

• CYK-1 and ARP2/3 complex are the primary F-actin nucleators driving distinct cortical actin architectures.
• The kinetics of cytokinesis are modulated by the antagonistic interplay between CYK-1 and the ARP2/3 complex.
• ARP2/3 complex negatively regulates CYK-1 activity, ensuring proper cell division timing.