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Mechanics of intermediate filaments and microtubules in living cells

Abstract : Although extensively studied in vitro, the mechanics of the cytoskeleton is still largely unexplored in living cells. We use an intracellular optical tweezers-based micromanipulation technique to apply forces directly on cytoskeletal filaments in order to probe microtubules and intermediate filament mechanics and focus on how they interact mechanically. Measuring simultaneously the force applied to the filaments and their deflection, i.e. the deformation of the filaments perpendicular to their axis, as a function of time, allows us to deduce the force-deflection curves of the filaments and to characterize the rigidity of vimentin intermediate filaments and microtubules. By fitting the force-deflection curves at small forces, we show that microtubules have a lower effective stiffness than vimentin upon deflection. We then apply forces twice on the same cytoskeletal bundle to show that vimentin filaments, but not microtubules, stiffen more than three times upon repeated deflections. We further characterize the mechanical coupling between vimentin filaments and microtubules by using microtubule destabilizing and stabilizing drugs and by increasing microtubule acetylation. Interestingly, we find that these modifications do not affect the effective stiffness of vimentin filaments while destabilizing or acetylating microtubules significantly reduces vimentin filament stiffening upon repeated deflection. Altogether, these results suggest that microtubules promote stiffening of vimentin bundles under repeated mechanical stress. In sharp contrast, in cells knockout for vimentin, the mechanical properties of microtubules are unchanged. Our findings highlight the importance of the interactions between microtubules and intermediate filaments in cell mechanics and suggest that vimentin intermediate filaments are mechanosensitive structures which exhibit history-dependent mechanoresponses.
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Submitted on : Monday, October 25, 2021 - 5:14:10 PM
Last modification on : Sunday, June 26, 2022 - 3:17:39 AM
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  • HAL Id : tel-03402660, version 1


Nathan Lardier. Mechanics of intermediate filaments and microtubules in living cells. Cellular Biology. Université Paris sciences et lettres, 2021. English. ⟨NNT : 2021UPSLS058⟩. ⟨tel-03402660⟩



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