Investigators tested whether intermediate filaments influence motility under mechanical stress. Cells were migrated across a substrate containing alternating soft and stiff regions. Control cells maintained similar speed but changed shape more on stiff regions. Cells with reduced vimentin (an intermediate filament protein) showed comparable protrusion formation on both regions but exhibited increased cytoplasmic deformation and occasional rupture-like blebs on stiff regions, leading to more frequent reversals and reduced net displacement. Actin polymerization at the front was still observed. Which statement best describes the role of intermediate filaments in cell motility in this experiment?
- Intermediate filaments are static and cannot affect migration, so reduced vimentin should increase net displacement by lowering cytoskeletal stiffness.
- Intermediate filaments are the primary drivers of leading-edge protrusion, so reducing vimentin should prevent actin polymerization at the front.
- Intermediate filaments serve as the principal tracks for vesicle transport, so reducing vimentin should specifically block microtubule-based delivery.
- Intermediate filaments mainly provide mechanical support that helps cells tolerate deformation during migration, improving net displacement under stiff conditions. (correct answer)
Explanation: This question assesses understanding of intermediate filament function under mechanical stress during migration. Intermediate filaments provide mechanical resilience that helps cells withstand deformation forces. In the vignette, vimentin-reduced cells showed increased deformation and rupture on stiff substrates, leading to more reversals and reduced net displacement. Choice D is correct because it accurately describes how intermediate filaments provide mechanical support that helps cells tolerate deformation during migration, improving net displacement under stiff conditions. Choice B is incorrect because intermediate filaments do not drive leading-edge protrusion - this is an actin-based process. When evaluating cell migration under mechanical stress, remember that intermediate filaments act as shock absorbers, maintaining cellular integrity without directly generating motile forces.