Multiscale mechanics and temporal evolution of vimentin intermediate filament networks

Abstract

The cytoskeleton, an intricate network of protein filaments, motor proteins, and crosslinkers, largely determines the mechanical properties of cells. Among the three filamentous components, F-actin, microtubules, and intermediate filaments (IFs), the IF network is by far the most extensible and resilient to stress. We present a multiscale approach to disentangle the three main contributions to vimentin IF network mechanics – single filament mechanics, filament length, and interactions between filaments – including their temporal evolution. Combining particle tracking, quadruple optical trapping and computational modeling, we derive quantitative information on the strength and kinetics of filament interactions. Specifically, we find that hydrophobic contributions to network mechanics enter mostly via filament elongation kinetics, whereas electrostatics have a direct influence on filament–filament interactions. These results indicate that cells might need to explicitly suppress attractive interactions to re-organize the extremely stable cellular vimentin network.

Vimentin Intermediate Filament Softening - Recovery Behavior and Post-Translational Modifications

“…In addition, comparing our results to experiments with network stiffness measured over time as shown in Ref. [103], further shows that our obtained control vimentin networks are much softer and our MSDs do not reach a plateau for long lag times τ. The difference between the experiment described in Ref.…”

“…The difference between the experiment described in Ref. [103] and the one described here, is the used wall material for the measuring chamber and the height of the chamber. In Ref.…”

“…Over time, vimentin networks stiffen which can be linked to an increase in filament length [103]. However, reduction of the hydrophobic or an increase in electrostatic interactions in between vimentin filaments leads to slower filament elongation and therefore to delayed network formations [103]. This strengthens the importance of various conditions that have an impact on filament network mechanics: elongation kinetics as well as filament-filament interactions [103].…”

“…Another important parameter to consider during network formation is the temporal evolution of the IF network. Over time, vimentin networks stiffen which can be linked to an increase in filament length [103]. However, reduction of the hydrophobic or an increase in electrostatic interactions in between vimentin filaments leads to slower filament elongation and therefore to delayed network formations [103].…”

“…However, reduction of the hydrophobic or an increase in electrostatic interactions in between vimentin filaments leads to slower filament elongation and therefore to delayed network formations [103]. This strengthens the importance of various conditions that have an impact on filament network mechanics: elongation kinetics as well as filament-filament interactions [103]. Despite all the research done on mechanics of IFs, they are not as extensively studied compared to actin and microtubules which are the other two components of the cytoskeleton and various aspects still remain unclear.…”