Rho kinase regulates the intracellular micromechanical response of adherent cells to Rho activation

Thomas P. Kole, Yiider Tseng^*, Lawrence Huang, Joseph L. Katz, and Denis Wirtz^*

Department of Chemical and Biomolecular Engineering, The Johns Hopkins University; Department of Biomedical Engineering, The Johns Hopkins University; Graduate Program in Molecular Biophysics, The Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, USA

Monitoring Editor: Paul Matsudaira

Local sol-gel transitionsof the cytoskeleton modulate cell shape changes, which are requiredfor essential cellular functions, including motility and adhesion.In vitro studies using purified cytoskeletal proteins have suggestedmolecular mechanisms of regulation of cytoskeleton mechanics;however, the mechanical behavior of living cells and the signalingpathways by which it is regulated remains largely unknown. Toaddress this issue, we used a nanoscale sensing method, intracellularmicrorheology, to examine the mechanical response of the cellto activation of the small GTPase Rho. We observe that the cytoplasmicstiffness and viscosity of serum-starved Swiss 3T3 cells transientlyand locally enhances upon treatment with lysophosphatidic acid(LPA), and this mechanical behavior follows a similar trendas Rho activity. Furthermore, the time-dependent activationof Rho decreases the degree of microheterogeneity of the cytoplasm.Our results reveal fundamental differences between intracellularelasticity and cellular tension, and suggest a critical rolefor Rho kinase in the regulation of intracellular mechanics.

^*Corresponding author. E-mail address: yiider{at}jhu.edu

^*Corresponding author. E-mail address: wirtz{at}jhu.edu