The role of F-actin and myosin in epithelial cell rheology
Kathleen M Van Citters 1, Brenton D Hoffman 1, Gladys Massiera 1 and John C. Crocker 1*
1 University of Pennsylvania
* To whom correspondence should be addressed. E-mail: jcrocker{at}seas.upenn.edu.
Submitted on June 13, 2006
Revised on August 19, 2006
Accepted on 21 August 2006
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Abstract |
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While actin and myosin are important contributors to cell force generation, shape change and motility, their contributions to cell stiffness and frequency-dependent rheology have not been conclusively determined. We apply several pharmacological interventions to cultured epithelial cells to elucidate the roles of actin and myosin in cells' mechanical response and intracellular fluctuations. A suite of different methods is used to separately examine the mechanics of the deep cell interior and cortex, in response to depletion of intracellular ATP, depolymerization of F-actin and inhibition of myosin II. Comparison of these results shows that F-actin plays a significant role in the mechanics of the cortical region of epithelial cells, but its disruption has no discernable effect on the rheology of the deeper interior. Moreover, we find that myosins do not contribute significantly to the rheology or ATP dependent, non-Brownian motion in the cell interior. Finally, we investigate the broad distribution of apparent stiffness values reported by some microrheology methods, which are not observed with two-point microrheology. Based on our findings and a simple model, we conclude it is heterogeneity of the tracer-cytoskeleton contacts, not the network itself, which is primarily responsible for the broad distribution of apparent stiffnesses.
Key Words:
actin, cell mechanics, cytoskeleton, microrheology, myosin