Attractive interactions among intermediate filaments determine network mechanics in vitro
Paul Pawelzyk1, Norbert Mücke2, Harald Herrmann3
1Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
Plos One
|April 3, 2014
Summary
Mechanical properties of intermediate filament (IF) networks, like K8/K18 and vimentin, were studied. Two binding sites were identified, one for high elastic modulus and another for strain stiffening, crucial for IF network mechanics.
Area of Science:
- Biophysics
- Materials Science
- Cell Biology
Background:
- Intermediate filaments (IFs) are crucial cytoskeletal components.
- Their mechanical and structural properties are vital for cell and tissue integrity.
- Understanding IF network mechanics informs disease research and biomaterial development.
Purpose of the Study:
- To investigate the mechanical and structural properties of K8/K18 and vimentin intermediate filament (IF) networks.
- To elucidate the molecular mechanisms underlying IF network mechanics, particularly strain stiffening and elastic modulus.
- To identify the roles of different filament domains and interactions in network behavior.
Main Methods:
- Bulk mechanical rheometry to measure network properties.
- Optical microrheology techniques, including diffusing wave spectroscopy and multiple particle tracking.
- Analysis of filament assembly, persistence length, and network mesh size.
- Investigation of the effects of nonionic surfactants and tailless mutants.
Main Results:
- IF networks exhibit high elastic modulus (G0) and pronounced strain stiffening even without external crosslinkers.
- G0 shows weak concentration dependency (G0 ∼ c(0.5 ± 0.1)) attributed to strong attractive interactions.
- Strain stiffening is suppressed by surfactants and absent in tailless mutants, indicating the importance of tail domains.
- A weaker binding site in the central rod contributes to high G0, while a stronger site in the tail domain facilitates strain stiffening.
- Vimentin shows less strain stiffening than K8/K18 due to electrostatic repulsion.
Conclusions:
- Two distinct binding sites govern IF network mechanics: one for high elastic modulus and another for strain stiffening.
- Hydrophobic interactions in the central rod and tail domains are critical for IF network mechanical integrity and responsiveness.
- Understanding these mechanisms provides insights into cytoskeletal mechanics and potential therapeutic targets.
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