Abstract
The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress. We previously showed that vimentin interacts with zinc, which affects its assembly and redox sensing. Here, we used vimentin wt and C328S, an oxidation-resistant mutant showing improved NaCl-induced polymerization, to assess the impact of zinc on soluble and polymerized vimentin by light scattering and electron microscopy. Zinc acts as a switch, reversibly inducing the formation of vimentin oligomeric species. High zinc concentrations elicit optically-detectable vimentin structures with a characteristic morphology depending on the support. These effects also occur in vimentin C328S, but are not mimicked by magnesium. Treatment of vimentin with micromolar ZnCl2 induces fibril-like particles that do not assemble into filaments, but form aggregates upon subsequent addition of NaCl. In contrast, when added to NaCl-polymerized vimentin, zinc increases the diameter or induces lateral association of vimentin wt filaments. Remarkably, these effects are absent or attenuated in vimentin C328S filaments. Therefore, the zinc-vimentin interaction depends on the chemical environment and on the assembly state of the protein, leading to atypical polymerization of soluble vimentin, likely through electrostatic interactions, or to broadening and lateral association of preformed filaments through mechanisms requiring the cysteine residue. Thus, the impact of zinc on vimentin assembly and redox regulation is envisaged.
Highlights
Intermediate filaments play a fundamental role in the integration of cytoskeletal functions, and in cell dynamics and behavior
EDTA-Free Vimentin Reveals Differential Polymerization Features Derived from the Presence of the Cysteine Residue
In order to study the effect of micromolar zinc on vimentin assembly, we employed a procedure for efficient removal of EDTA from vimentin preparations [41]
Summary
Intermediate filaments play a fundamental role in the integration of cytoskeletal functions, and in cell dynamics and behavior. The type III intermediate filament protein vimentin constitutes a key cytoskeletal element of mesenchymal cells. Vimentin plays key roles in essential cell functions such as division and migration and contributes to cellular structural support and plasticity and organelle positioning. Biophysical techniques are providing high resolution information on the mechanics and dynamic performance of the vimentin network, with a clear impact on the physical properties of cells [6,7]. Vimentin is a key marker and agent of epithelial mesenchymal transition and tumor malignancy [2,8,9,10] and is involved in bacterial and viral infections [11] and autoimmune diseases [12]
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