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Contributed Talk, Thursday, 14:45 – 15:00  
Substrate-Ligand Friction Modulates Traction Force

Tilo Pompe1,2, Martin Kaufmann2, Maria Kasimir2, Stephanie Johne2, Stefan Glorius2, Lars Renner2, Manfred Bobeth3, Wolfgang Pompe3, Carsten Werner1,4
 
1
 Universität Leipzig, Institute of Biochemistry, 04103 Leipzig, Germany
2
 Leibniz Institute of Polymer Research Dresden, Max Bergmann Center of Biomaterials Dresden, 01069 Dresden, Germany
3 Dresden University of Technology, Institute of Materials Science, 01062 Dresden, Germany
4 Center of Regenerative Therapies Dresden, 01307 Dresden, Germany

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The force balance between the extracellular microenvironment and the intracellular cytoskeleton controls cell fate decisions. We report on a new mechanism, which exogenously modulates cellular traction forces at adhesion receptors by controlling the anchorage of adhesion ligands to the underlying support or matrix. In the presented example the physiochemistry of a artificial polymer surface was used to vary the anchorage strength of adhesion ligands like fibronectin by variations in materials polarity and hydrophobicity independently of other mechanical properties of the substrate like stiffness.
Using traction force cytometry and mobility measurements of the adhesion ligands we demonstrate the traction force control to originate from friction between the adhesion ligands and the supporting materials/matrix. Within this idea we use the principles of myosin motor activity during fibrillar assembly of fibronectin ligands non-covalently coupled to polymer surfaces and traction force generation at adhesion sites. The description of ligand reorganization during fibronectin fibrillogenesis by a diffusion process allowed us to correlate ligand surface mobility to the cellular traction force at the adhesion receptors by a quasistatic equilibrium between myosin motors inside the cells and the ligand friction on the substrate surface outside the cells.
These findings elucidate a novel mechanism of force regulation at adhesion receptors, which is proposed to be highly relevant in mechanotransduction of adherent cells in natural and artificial scaffolds as well as in cancer progression and metastasis, as many adhesion ligands are found dynamically bound to the extracellular matrix.
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