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BP: Fachverband Biologische Physik

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

BP 24.13: Poster

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

Post-Translational Modifications Soften Vimentin Filaments — •Julia Kraxner, Charlotta Lorenz, and Sarah Köster — Institute for X-Ray Physics, University of Göttingen, Germany

The mechanical properties of biological cells greatly influence their function, such as the ability to move, contract and divide and they need to flexibly adapt, for example during wound healing or cancer metastasis. These mechanical properties are determined by the so-called cytoskeleton, a complex network consisting of three filamentous protein systems, microtubules, actin filaments and intermediate filaments (IFs). A rather slow way to adapt cell mechanics to varying requirements on the cell is differential expression of the cytoskeleton proteins which affects the network architecture and the interaction between the filaments. Here, we focus on the intermediate filament vimentin and introduce post-translational modifications (PTMs), i.e. changes applied to specific amino acids in the protein after expression in the cell. By such PTMs, e.g. the charge pattern along the protein may be altered. Interestingly, PTMs occur comparatively fast and thus provide a mechanism for mechanical modulation on short time scales. We study the impact of one such PTM, phosphorylation, which is the addition of a phosphate group to an amino acid, on filament mechanics by stretching single filaments using optical traps. Whereas full phosphorylation leads to disassembly of IFs, partial phosphorylation results in softening of the filaments. By employing mutants that mimic phosphorylation as well as Monte Carlo simulations, we explain our observation through the additional charges introduced during phosphorylation.