Keratin intermediate filaments (KIFs) form cytoskeletal KIF networks that are essential for the structural integrity of epithelial cells. However, the mechanical properties of the in situ network have not been defined. Particle-tracking microrheology (PTM) was used to obtain the micromechanical properties of the KIF network in alveolar epithelial cells (AECs), independent of other cytoskeletal components, such as microtubules and microfilaments. The storage modulus (G′) at 1 Hz of the KIF network decreases from the perinuclear region (335 dyn/cm2) to the cell periphery (95 dyn/cm2), yielding a mean value of 210 dyn/cm2. These changes in G′ are inversely proportional to the mesh size of the network, which increases ≈10-fold from the perinuclear region (0.02 μm2) to the cell periphery (0.3 μm2). Shear stress (15 dyn/cm 2 for 4 h) applied across the surface of AECs induces a more uniform distribution of KIF, with the mesh size of the network ranging from 0.02 μm2 near the nucleus to only 0.04 μm2 at the cell periphery. This amounts to a 40% increase in the mean G′. The storage modulus of the KIF network in the perinuclear region accurately predicts the shear-induced deflection of the cell nucleus to be 0.87 ± 0.03 μm. The high storage modulus of the KIF network, coupled with its solidlike rheological behavior, supports the role of KIF as an intracellular structural scaffold that helps epithelial cells to withstand external mechanical forces.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 22 2008|
- Intermediate filaments
- Lung alveolar epithelial cells
- Shear stress