Actin filament assembly driven by distributive polymerases clustered on membrane surfaces

Area of Science:

• Biochemistry
• Cell Biology
• Biophysics

Background:

• Actin filaments form branched networks via the Arp2/3 complex, driving cellular membrane dynamics.
• Understanding actin polymerization mechanisms is crucial for cell motility and division.

Purpose of the Study:

• To theoretically and computationally investigate how membrane surfaces influence actin filament assembly.
• To determine the conditions under which surface-mediated polymerization surpasses solution-mediated elongation.

Main Methods:

• Utilized theoretical modeling and computer simulations.
• Incorporated experimentally measured parameter values for actin dynamics.
• Analyzed the impact of protein clustering and thermal fluctuations on filament growth.

Main Results:

• Membrane surfaces accelerate actin filament assembly by concentrating actin-binding proteins.
• Surface-mediated polymerization can exceed solution-mediated elongation rates, especially at high actin concentrations (>200 μM).
• Profilin dissociation time reduces surface advantages without force, while load forces enhance polymerization and stall force.

Conclusions:

• Membrane confinement and protein clustering significantly enhance actin filament elongation rates.
• Surface effects are critical for understanding actin dynamics in cellular processes involving membrane interactions.
• Force-dependent regulation of actin polymerization is modulated by surface-associated factors.