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Abstract Actin filament assembly and mechanics are crucial for maintenance of cell structure, motility, and division. Actin filament assembly occurs in a crowded intracellular environment consisting of various types of molecules, including small organic molecules known as osmolytes. Ample evidence highlights the protective functions of osmolytes such as trimethylamine‐N‐oxide (TMAO), including their effects on protein stability and their ability to counteract cellular osmotic stress. Yet, how TMAO affects individual actin filament assembly dynamics and mechanics is not well understood. We hypothesize that, owing to its protective nature, TMAO will enhance filament dynamics and stiffen actin filaments due to increased stability. In this study, we investigate osmolyte‐dependent actin filament assembly and bending mechanics by measuring filament elongation rates, steady‐state filament lengths, and bending persistence lengths in the presence of TMAO using total internal reflection fluorescence microscopy and pyrene assays. Our results demonstrate that TMAO increases filament elongation rates as well as steady‐state average filament lengths, and enhances filament bending stiffness. Together, these results will help us understand how small organic osmolytes modulate cytoskeletal protein assembly and mechanics in living cells.
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Growth‐induced collective bending and kinetic trapping of cytoskeletal filaments
Abstract Growth and turnover of actin filaments play a crucial role in the construction and maintenance of actin networks within cells. Actin filament growth occurs within limited space and finite subunit resources in the actin cortex. To understand how filament growth shapes the emergent architecture of actin networks, we developed a minimal agent‐based model coupling filament mechanics and growth in a limiting subunit pool. We find that rapid filament growth induces kinetic trapping of highly bent actin filaments. Such collective bending patterns are long‐lived, organized around nematic defects, and arise from competition between filament polymerization and bending elasticity. The stability of nematic defects and the extent of kinetic trapping are amplified by an increase in the abundance of the actin pool and by crosslinking the network. These findings suggest that kinetic trapping is a robust consequence of growth in crowded environments, providing a route to program shape memory in actin networks.
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- Award ID(s):
- 2203601
- PAR ID:
- 10508796
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Cytoskeleton
- Volume:
- 81
- Issue:
- 8
- ISSN:
- 1949-3584
- Format(s):
- Medium: X Size: p. 409-419
- Size(s):
- p. 409-419
- Sponsoring Org:
- National Science Foundation
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