Substrate stiffness regulates solubility of cellular vimentin

Area of Science:

• Cell Biology
• Biochemistry
• Biophysics

Background:

• Intermediate filament protein vimentin regulates cell behavior, morphology, and mechanics.
• Previous studies indicated vimentin is largely insoluble in cells cultured on rigid substrates.
• Substrate stiffness effects on vimentin organization were previously unreported.

Purpose of the Study:

• To investigate the impact of substrate stiffness on vimentin organization and solubility.
• To explore the dynamic nature of vimentin in response to cellular mechanical cues.

Main Methods:

• Culturing human mesenchymal stem cells (hMSCs), endothelial cells, and fibroblasts on substrates of varying stiffness.
• Assessing vimentin detergent solubility and organization using imaging techniques.
• Modulating cellular tension and morphology through various biochemical and mechanical interventions.

Main Results:

• Vimentin detergent solubility exhibited biphasic changes, increasing with cell spreading and membrane ruffling on softer substrates.
• Soluble vimentin appeared as small fragments, suggesting dynamic assembly/disassembly.
• Vimentin solubility decreased with serum starvation, cell-cell contact formation, microtubule disruption, or inhibition of specific signaling pathways (Rac1, ROCK, PAK).
• Inhibition of myosin or actin assembly increased vimentin solubility on rigid substrates.

Conclusions:

• Vimentin exhibits greater dynamic behavior and sensitivity to cellular tension and morphology changes than previously understood.
• Substrate stiffness significantly influences vimentin assembly state and solubility.
• These findings suggest a more adaptable role for vimentin in response to the in vivo mechanical environment.