Cells respond to the physical properties of their surroundings by remodeling their cytoskeleton, mainly actin filaments, into higher order structures that can propagate forces across the cell. Numerous studies have shown how forces affect actin remodeling directly at sites of force application. However, their effects on actin filaments at distant locations remained uncharacterized until recently.
This study reveals a previously unidentified, far-acting effect of forces on actin remodeling. By using a specially designed atomic force microscopy tip to apply forces of a magnitude between 100-200 nN at the cell periphery, the researchers noted the assembly of actin filaments around the nucleus into a transient high-order structure, which they called the perinuclear actin rim. The assembly of the perinuclear actin rim was dependent on force-induced release of Ca2+ in the cytoplasm, and was found to be mediated by the actin filament nucleation and elongation factor, inverted formin-2 (INF-2).
The perinuclear actin rim is associated with two main functions: relaying mechanical signals from the cytoplasm to the nucleus, and shielding the genome from any mechanical perturbations that could reach the nucleus.