Molecular Crowding Modulates Actin Filament Mechanics and Structure

Abstract

The cellular environment is crowded with high concentrations of macromolecules that significantly reduce the accessible volume limiting biomolecule interactions. Reductions in cellular volume can generate depletion forces that affect protein assembly and stability. The mechanical and structural properties of actin filaments play critical roles in various cellular functions including structural support, cell movement, division, and intracellular transport. Although the effects of molecular crowding on actin polymerization have been shown, how crowded environments affect filament conformations, dynamics, and mechanical properties is unknown. In this study, we investigate the effects of solution crowding on the modulations of filament mechanics and structure both in vitro and in silico. Direct visualization of filaments in the presence of crowding agents is achieved by fluorescence microscopy imaging, allowing for the quantification of filament thermal bending dynamics and mechanics. Biophysical analysis indicate that molecular crowding modulates thermal fluctuations, enhances filament's effective bending stiffness, and reduces average filament lengths. Utilizing the explicit molecular dynamics simulations, we demonstrate that molecular crowding alters filament conformations and structural properties indicating overall compaction and stabilization that are directly coupled to filament mechanics. Taken together, our study suggests the interplay between excluded volume effects and non‐specific interactions raised from molecular crowding may modulate actin filament mechanics and structure.Support or Funding InformationThis study was supported by the UCF start‐up fund and In‐House grant for H.K. The authors would like to thank the National Science Foundation for support of this work through REU site EEC 1560007. We acknowledge the computational time from UCF stokes cluster.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.