PT  - JOURNAL ARTICLE
AU  - Andrea Cordes
AU  - Hannes Witt
AU  - Aina Gallemí-Pérez
AU  - Bastian Brückner
AU  - Florian Grimm
AU  - Marian Vache
AU  - Tabea Oswald
AU  - Daniel Flormann
AU  - Franziska Lautenschläger
AU  - Marco Tarantola
AU  - Andreas Janshoff
TI  - Pre-stress of actin cortices is important for the viscoelastic response of living cells
AID  - 10.1101/783613
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 783613
4099  - http://biorxiv.org/content/early/2020/03/25/783613.short
4100  - http://biorxiv.org/content/early/2020/03/25/783613.full
AB  - Shape, dynamics, and viscoelastic properties of eukaryotic cells are primarily governed by a thin, reversibly cross-linked actomyosin cortex located directly beneath the plasma membrane. We obtain time-dependent rheological responses of fibroblasts and MDCK II cells from deformation-relaxation curves using an atomic force microscope to access the dependence of cortex fluidity on pre-stress. We introduce a viscoelastic model that treats the cell as a composite shell and assumes that relaxation of the cortex follows a power law giving access to cortical pre-stress, area compressibility modulus, and the power law (fluidity) exponent. Cortex fluidity is modulated by interfering with myosin activity. We find that the power law exponent of the cell cortex decreases with increasing intrinsic pre-stress and area compressibility modulus, in accordance with previous finding for isolated actin networks subject to external stress. Extrapolation to zero tension returns the theoretically predicted power law exponent for transiently cross-linked polymer networks. In contrast to the widely used Hertzian mechanics, our model provides viscoelastic parameters independent of indenter geometry and compression velocity.