Dresden 2017 – scientific programme

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BP: Fachverband Biologische Physik

BP 39: Optogenetics for the Cytoskeleton - Focus Session organized by Ulrich Schwarz

BP 39.6: Talk

Wednesday, March 22, 2017, 11:45–12:00, SCH A251

Controlling and modelling contractility in adherent cells — •Dimitri Probst¹, Christoph A. Brand¹, Marco Linke¹, Patrick W. Oakes², Elizabeth Wagner³, Michael Glotzer³, Margaret L. Gardel², and Ulrich S. Schwarz¹ — ¹Institute for Theoretical Physics & BioQuant, Heidelberg University, Germany — ²Institute for Biophysical Dynamics, James Franck Institute and the Department of Physics, University of Chicago, USA — ³Department of Molecular Genetics and Cell Biology, University of Chicago, USA

Cellular contractility is known to be controlled by a small GTPase called RhoA, whose active form promotes both actin polymerization and myosin II motor activity. For example, a global increase of active RhoA in adherent tissue cells leads to the formation of focal adhesions and stress fibers. However, how localized RhoA signals translate into cell-level responses is not well understood. Here we address this question through experiments and modelling using an optogenetic approach. Local activation of RhoA stimulates local contraction that is quickly propagated over the whole cell through the stress fibers. It also drives F-actin and myosin towards the region of heightened RhoA. Surprisingly, the flow reverses direction when local RhoA activation stops. We explain our experimental findings with a viscoelastic physical model that demonstrates that stress fibers are elastic-like structures. We show that the elasticity of the stress fibers is preserved even at time scales exceeding turnover of constituent proteins. Our model furthermore allows to identify the repair molecule zyxin as a key regulator of stress fiber mechanics, as they become fluid-like in its absence.