Substrate stiffness regulates solubility of cellular vimentin

Vimentin in hMSCs on different-stiffness gels. Vimentin networks are evident in cells on gels over a wide range of stiffnesses (A–D; actin, red; vimentin, green; and nuclei, blue). On 0.2-kPa gels hMSCs are small and round (Figure 2, A, E, I, and M). Cells elongate on 5-kPa gels (B, F, J, N). On 30-kPa gels and silanized glass, cells spread similarly and contain stress fibers (G, H), and the vimentin network extends to the cell edge (O, P). Bars, 10 μm. Substrate stiffness regulates solubility of cellular vimentin Mol Biol Cell. 2014 January 1;25(1):87-94.

Vimentin in hMSCs on different-stiffness gels. Vimentin networks are evident in cells on gels over a wide range of stiffnesses (A–D; actin, red; vimentin, green; and nuclei, blue). On 0.2-kPa gels hMSCs are small and round (Figure 2, A, E, I, and M). Cells elongate on 5-kPa gels (B, F, J, N). On 30-kPa gels and silanized glass, cells spread similarly and contain stress fibers (G, H), and the vimentin network extends to the cell edge (O, P). Bars, 10 μm.
Substrate stiffness regulates solubility of cellular vimentin
Mol Biol Cell. 2014 January 1;25(1):87-94.

Murray ME, Mendez MG, Janmey PA. Substrate stiffness regulates solubility of cellular vimentin. Mol Biol Cell Jan 2014; 25 (1): 87-94.

Summary

The intermediate filament protein vimentin is involved in the regulation of cell behavior, morphology, and mechanical properties. Previous studies using cells cultured on glass or plastic substrates showed that vimentin is largely insoluble. Although substrate stiffness was shown to alter many aspects of cell behavior, changes in vimentin organization were not reported. Our results show for the first time that mesenchymal stem cells (hMSCs), endothelial cells, and fibroblasts cultured on different-stiffness substrates exhibit biphasic changes in vimentin detergent solubility, which increases from nearly 0 to 67% in hMSCs coincident with increases in cell spreading and membrane ruffling. When imaged, the detergent-soluble vimentin appears to consist of small fragments the length of one or several unit-length filaments. Vimentin detergent solubility decreases when these cells are subjected to serum starvation, allowed to form cell-cell contacts, after microtubule disruption, or inhibition of Rac1, Rho-activated kinase, or p21-activated kinase. Inhibiting myosin or actin assembly increases vimentin solubility on rigid substrates. These data suggest that in the mechanical environment in vivo, vimentin is more dynamic than previously reported and its assembly state is sensitive to stimuli that alter cellular tension and morphology.

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