A node organization in the actomyosin contractile ring generates tension and aids stability

Area of Science:

• Cell Biology
• Biophysics
• Computational Biology

Background:

• Cytokinesis relies on the contractile actomyosin ring for cell division.
• The precise mechanism of tension generation within this ring remains unclear.
• Recent studies identified plasma membrane-anchored nodes containing myosin and formins in the fission yeast ring.

Purpose of the Study:

• To investigate the functional consequences of the newly discovered node ultrastructure in the fission yeast contractile ring.
• To elucidate the mechanism of tension generation and node dynamics.
• To explore factors contributing to ring stability.

Main Methods:

• Construction and analysis of a coarse-grained mathematical model of the fission yeast contractile ring.
• Incorporation of experimentally observed node ultrastructure and dynamics into the model.

Main Results:

• The model accurately reproduced experimentally measured ring tension.
• The model explained the observed bidirectional movement of nodes around the ring.
• Tension generation was attributed to a stochastic sliding-filament mechanism involving myosin pulling on actin filaments, independent of sarcomeric organization.

Conclusions:

• The fission yeast contractile ring generates tension through a stochastic sliding-filament mechanism within membrane-anchored nodes.
• Bidirectional node movement and tension generation are consequences of the ring's ultrastructure.
• Component turnover and plasma membrane anchoring are essential for preventing contractile instabilities and maintaining organizational homeostasis.