Berlin 2008 – scientific programme
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BP: Fachverband Biologische Physik
BP 8: Active Filament Networks
BP 8.4: Talk
Tuesday, February 26, 2008, 11:00–11:15, C 243
Cytoskeleton nanosurgery Part I : Force sensing mechanism within actin stress fibers — •Julien Colombelli1, Achim Besser2, Emmanuel Reynaud1, Holger Kress3, Philippe Girard1, Ulrich Schwarz2, Victor Small4, and Ernst Stelzer1 — 1EMBL. Meyerhofst. 1, D-69117 Heidelberg — 2University Heidelberg, Bioquant, BQ0013 BIOMS, D-69120, Heidelberg — 3Mech. Eng. Dept., Yale University, New Haven CT 06511, USA — 4Institute for Molecular Biotechnology (IMBA), Bohr Gasse, A-1030 Vienna
Mechanotransduction defines the ensemble of mechanisms by which cells convert mechanical stimuli into biochemical activity. The cytoskeleton plays a central role in propagating mechanical signals, however the molecular sensors that potentially recognize mechanical movements, forces and tensions are widely missing. We focus here on perturbing the mechanical equilibrium of the actin cytoskeleton. We study the mechanical relaxation of actin stress fibers (SFs) after combined FRAP and laser nanosurgery in living cells. Quantitative analysis provides support for a theoretical viscoelastic model of SFs dynamics, which predicts the dynamics of contractile forces throughout the SFs. We then analyze the localization by live fluorescence and correlative EM of zyxin, an alpha-actinin partner in SFs. Non-equilibrium dynamics of zyxin after force perturbation by drug treatment, nanosurgery, or external micromanipulation show a high correlation between the modeled forces within the SFs and the localization of zyxin. We propose that SFs sense the molecular forces generated through actomyosin contractility with the mechanosensitive protein zyxin.