Authors
Meyer R, Rölleke U, Schwarz N, Perez-Tirado A, Schepers AV, Janshoff A, Köster S
Journal
BioRxiv
Citation
bioRxiv 2025.02.24.639846.
Abstract
The eukaryotic cytoskeleton consists of three filament types: actin filaments, microtubules and intermediate filaments (IFs). IF proteins are expressed in a cell-type specific manner, and keratins are found in epithelial cells. In certain cell types, the keratins form a layer close to the membrane which may be referred to as an “IF-cortex”. It is hypothesized that this IF-cortex arranges with radial bundles in a “rim-and-spokes” structure in epithelia. Based on this hypothesis, IFs and actin filaments might add complementary mechanical properties to the cortex. It was previously shown that single IFs in vitro remain undamaged at high strains. We now ask the question of whether this unique force-extension behavior of single IFs is also relevant in the filament network within a cell. Here, we show the influence of equibiaxial strain on wild-type (WT) and keratin-deficient (KO) cells comparing the viscoelastic properties close to the cell membrane using atomic force microscopy, in a spatially resolved manner. We find that cells without keratin exhibit a higher pre-stress than the WT cells. The compressibility modulus is increased at the cell rim, compared to the inside region, due to the geometry of the cell layer. Interestingly, both the pre-stress and the fluidity of the KO cells are altered already at low strains, whereas the WT cells show a response only at large strain. Our results indicate that KO cells compensate for the missing keratin, but are nevertheless very sensitive to external strain, whereas the intricate interplay between the actin and keratin cortices preserves the mechanical state and cell stability.
