The role of the actin cortex in maintaining cell shape.

Considering that the plasma membrane is host to a variety of mechanical cues in vivo, and the actin cortex is known to support cell shape, it comes as no surprise that the paired membrane-cortex plays a major role in cellular responses to deformation. In a recent study, we applied highly localized forces to HeLa cells in order to examine the deformation response of the membrane and cortex. Direct visualization of the deformation in the loading plane allowed for the characterization of the observed time-dependent strain. Despite large magnitude and long duration loading regimes, the majority of cells recovered their initial pre-deformed morphology within ~2 min. Unexpectedly, perturbed regions above large-volume nuclei were shown to be quite soft and had negligible influence on morphological recovery. The resistance to deformation and ability to recover was found to be largely influenced by the actin network, and dependent upon rho-kinase mediated contractility.