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BP: Fachverband Biologische Physik

BP 24: Poster B: Active Biological Matter, Cell Mechanics, Systems Biology, Computational Biophysics, etc.

BP 24.19: Poster

Tuesday, March 23, 2021, 16:00–18:30, BPp

Measurement of the mechanosensitive binding of actin crosslinkers in the cytoskeleton of live cells — •Valentin Ruffine, Kamran Hosseini, and Elisabeth Fischer-Friedrich — DFG Cluster of Excellence Physics of Life, BIOTEC, Technische Universität Dresden, Germany

In mammalian cells, actin filaments (F-actin) are bundled and crosslinked by multiple actin-binding proteins. The cytoskeletal structures they form are essential for cell motility, division, mechanosensitivity, intracellular transport and the mechanical protection of the cell. They have a highly nonlinear rheological behavior, which is tuned through their microscopic structure and their composition: the length of the microfilaments, the concentration of filaments and crosslinkers, and the nature of the crosslinkers.

Actin-binding proteins mostly form transient bonds with the filaments. This enable both a protective solid-like response on short timescales and large reorganization of the biopolymer network on longer ones. The average lifetime of these bonds typically depends on the mechanical load applied to them, thus on the mechanical stress in the actin network. Interestingly, this lifetime increases with increasing load for some actin crosslinkers. This behavior is termed "catch-bond" and is far less intuitive than the opposite, "slip-bond" behavior. Here, we report experimental results showing a catch-bond behavior for three major human actin crosslinkers: α-actinin 4, filamin A and filamin B. These were obtained in mitotic HeLa cells, using AFM-based cortical tension measurements coupled with FRAP and confocal imaging.