(428g) The Role of F-Actin and Myosin II in Epithelial Cell Rheology

The frequency-dependent mechanical response of epithelial cells treated with Latrunculin-A and blebbistatin was used to study the role of F-actin and myosin II on the mechanical properties of the cell. A suite of different methods is used to examine any differences between internal and cortical responses. These methods measure the response of cells to driving from both Brownian motion and an externally applied mechanical force. Comparison of these techniques emphasizes the presences of two mechanical distinct networks in epithelial cells. In addition, the actin network plays a prominent role in the rheology of the cortex of epithelial cells; decreasing the power law exponent of the rheology from 0.16 to 0.06. However, actin disruption has no measurable effect on the interior response. On the other hand, myosin II disruption showed no effect in the cortical region of the cell, but did lower the average amplitude of the mean squared displacement as measured from the cell's interior at long lag times, τ > 10^-3. Although both our interior measurement methods yield matching frequency dependence, laser tracking microrheology (LTM) reports a broad distribution of amplitudes that is not seen in two point microrheology (TPM). We present a hypothesis that simultaneously explains why tracer cytoskeleton links can be responsible for distributions measured by LTM, and suggests a minimum arrangement of bead-cell contacts needed to create this amplitude distribution.