How actin network dynamics control the onset of actin-based motility

Area of Science:

• Cell Biology
• Biophysics
• Biochemistry

Background:

• Cells utilize dynamic actin networks for mechanical control and motility.
• Branched actin filaments, produced by the Arp2/3 complex, form these essential networks.

Purpose of the Study:

• To investigate the conditions under which microscopic actin network organization generates sufficient stress for sustained cell motility.
• To understand the relationship between protein concentrations and the mechanical properties of growing actin networks.

Main Methods:

• Experimental growth of actin networks on beads in a minimal protein system.
• Simultaneous experimental and computational simulations to analyze network shape and mechanics.
• Systematic variation of protein concentrations (actin monomers, profilin, Arp2/3 complex, capping protein).

Main Results:

• Actin gel morphology is governed by key steps: primer contact, network growth, entanglement, mechanical interaction, and force production.
• Altering the biochemical orchestration of these steps can disrupt network cohesion and impair force generation.
• A predictive phase diagram illustrating actin gel fate based on protein concentrations was developed.

Conclusions:

• A tight biochemical and physical coupling in growing actin networks smooths initial heterogeneities.
• This coupling is crucial for governing force buildup and ultimately, cell motility.
• The findings provide insights into the fundamental mechanisms driving cell movement.