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Desmin and vimentin intermediate filament networks: their viscoelastic properties investigated by mechanical rheometry.

Abstract：

:We have investigated the viscoelastic properties of the cytoplasmic intermediate filament (IF) proteins desmin and vimentin. Mechanical measurements were supported by time-dependent electron microscopy studies of the assembly process under similar conditions. Network formation starts within 2 min, but it takes more than 30 min until equilibrium mechanical network strength is reached. Filament bundling is more pronounced for desmin than for vimentin. Desmin filaments (persistence length l(p) approximately 900 nm) are stiffer than vimentin filaments (l(p) approximately 400 nm), but both IFs are much more flexible than microfilaments. The concentration dependence of the plateau modulus G(0) approximately c(alpha) is much weaker than predicted theoretically for networks of semiflexible filaments. This is more pronounced for vimentin (alpha=0.47) than for desmin (alpha=0.70). Both networks exhibit strain stiffening at large shear deformations. At the transition from linear to nonlinear viscoelastic response, only desmin shows characteristics of nonaffine network deformation. Strain stiffening and the maximum modulus occur at strain amplitudes about an order of magnitude larger than those for microfilaments. This is probably attributable to axial slippage within the tetramer building blocks of the IFs. Network deformation beyond a critical strain gamma(max) results in irreversible damage. Strain stiffening sets in at lower concentrations, is more pronounced, and is less sensitive to ionic strength for desmin than for vimentin. Hence, desmin exhibits strain stiffening even at low-salt concentrations, which is not observed for vimentin, and we conclude that the strength of electrostatic repulsion compared to the strength of attractive interactions forming the network junctions is significantly weaker for desmin than for vimentin filaments. These findings indicate that both IFs exhibit distinct mechanical properties that are adapted to their respective cellular surroundings [i.e., myocytes (desmin) and fibroblasts (vimentin)].

journal_name

J Mol Biol

journal_title

Journal of molecular biology

authors

Schopferer M,Bär H,Hochstein B,Sharma S,Mücke N,Herrmann H,Willenbacher N

doi

10.1016/j.jmb.2009.03.005

subject

Has Abstract

pub_date

2009-04-24 00:00:00

pages

133-43

issue

eissn

0022-2836

issn

1089-8638

pii

S0022-2836(09)00270-8

journal_volume

388

pub_type

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Desmin and vimentin intermediate filament networks: their viscoelastic properties investigated by mechanical rheometry.