3D Visualization of compressed actin filaments simulated in ReaDDy [1] and Cytosim [2]. Filaments are aligned at the final time step of the simulation. ReaDDy filaments show notable directional biphasic out-of-plane behavior, indicative of filament twist only captured with monomer-scale resolution. Cytosim filaments showed very little out-of-plane behavior, and when they did, it was just as likely to be in either direction.
The dynamic bending and twisting of actin filaments mechanically drive many processes in cells.
Fundamental cellular processes such as endocytosis, cell motility, and cytokinesis are reliant on a cell's ability to produce force. The actin cytoskeleton plays a central role in force production in these processes.
The helical structure of actin filaments results in the coupling of filament twisting and bending, which impacts the structure of the actin network in 3D space. This has implications for actin's function in force production and maintainance of subcellular structures.
[TODO: more images and videos?]
Diagram illustrating the role of actin filament bending and twisting in endocytosis.
We developed two models of actin to compare twisting and bending at different spatiotemporal scales.
Many different simulation methods have been developed to model actin. Each simulation method has limitations depending on the spatial scale.
ReaDDy Actin filaments are composed of particles, one for each actin monomer, which are held together by potentials.
Cytosim actin filaments are represented by control points that define a mathematical line, which is acted upon by physical forces.
[TODO: add a few more details about methods including links to repos]
Diagram of actin filaments modeled at monomer-scale, in which the interactions of each monomer of the filament with its neighbors is explicitly simulated, and fiber-scale, in which the filament is modeled as a series of points connected by simple length and angle-limited springs that have no rotational constraints.
