Actin filaments growing against a barrier with fluctuating shape

Area of Science:

• Biophysics
• Polymer Physics
• Cellular Mechanics

Background:

• Actin filaments are crucial for cellular processes, generating forces against cellular structures.
• Understanding force generation mechanisms is key to comprehending cell motility and division.
• Nonrigid cellular components introduce complexities to biopolymer force dynamics.

Purpose of the Study:

• To investigate how the mechanical properties and fluctuations of a nonrigid obstacle affect force generation by growing actin filaments.
• To analyze the interplay between filament polymerization dynamics and barrier shape fluctuations.
• To determine the influence of external load on barrier morphology and force generation.

Main Methods:

• Simulations of parallel actin filament growth against a deformable barrier.
• Modeling barrier shape fluctuations using Kardar-Parisi-Zhang (KPZ) dynamics for a 1D interface.
• Analytical calculations using mean-field theory.
• Analysis of force-velocity relationships and barrier height profiles.

Main Results:

• Barrier shape fluctuations significantly alter the force generation mechanism of actin filaments.
• The force-velocity curve's characteristics depend critically on the relative timescales of filament polymerization and barrier dynamics.
• External load influences the barrier's height profile, revealing load-dependent morphological changes.
• Mean-field theory predictions show good agreement with simulation outcomes.

Conclusions:

• The mechanical response of nonrigid cellular obstacles is a critical factor in actin-mediated force generation.
• Fluctuations in cellular structures, described by KPZ dynamics, play a vital role in regulating biopolymer force-velocity relationships.
• This study provides a theoretical framework for understanding force generation in complex cellular environments.