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Actin bundle architecture and mechanics regulate myosin II force generation.

Kimberly L Weirich1, Samantha Stam2, Edwin Munro3

  • 1James Franck Institute, University of Chicago, Chicago, Illinois; Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina.

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Actin cytoskeleton architecture dictates myosin II dynamics and force generation. Bundle microstructure, including cross-linker rigidity and filament spacing, controls myosin motor activity and force output in biological materials.

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Area of Science:

  • Biophysics
  • Cell Biology
  • Biomaterials Science

Background:

  • The actin cytoskeleton is crucial for cellular functions like division and motility.
  • Actin filament organization into bundles influences actomyosin force generation, regulating cell behavior.
  • Understanding how actin architecture impacts motor protein dynamics is key to cell mechanics.

Purpose of the Study:

  • To investigate the impact of actin bundle architecture on myosin II dynamics and force generation.
  • To correlate actin filament polarity, spacing, and cross-linker rigidity with myosin II motor behavior.
  • To elucidate the relationship between microstructure and force generation in actin-based biomaterials.

Main Methods:

  • Utilized fluorescence microscopy to observe myosin II dynamics in different actin bundle architectures.
  • Employed computational simulations to model myosin II motion and force generation within actin networks.
  • Varied cross-linker properties (rigidity, size) and actin filament parameters (polarity, spacing) in simulations.

Main Results:

  • Rigid cross-linkers in mixed-polarity bundles led to slow, bidirectional myosin II motion with stalled periods, indicating high forces.
  • Compliant, large cross-linkers resulted in fast, bidirectional myosin II motion without stalls, correlating with lower forces.
  • Simulation results showed a direct relationship between myosin trap duration, force magnitude, and bundle compliance/spacing.

Conclusions:

  • Actin assembly microstructures significantly regulate myosin II dynamics and force magnitude.
  • Bundle architecture, including cross-linker mechanics and filament arrangement, is critical for controlling forces in biological materials.
  • This study highlights the importance of structural organization in the mechanical regulation of cellular processes.