Strain stiffening of Ndc80 complexes attached to microtubule plus ends.

Autor:	Schwietert F; Physics Department, TU Dortmund University, Dortmund, Germany., Volkov VA; School of Biological and Behavioural Sciences, Queen Mary University of London, London, UK; Department of Bionanoscience, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands., Huis In 't Veld PJ; Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany., Dogterom M; Department of Bionanoscience, Faculty of Applied Sciences, Delft University of Technology, Delft, Netherlands., Musacchio A; Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany., Kierfeld J; Physics Department, TU Dortmund University, Dortmund, Germany. Electronic address: jan.kierfeld@tu-dortmund.de.
Jazyk:	angličtina
Zdroj:	Biophysical journal [Biophys J] 2022 Nov 01; Vol. 121 (21), pp. 4048-4062. Date of Electronic Publication: 2022 Oct 04.
DOI:	10.1016/j.bpj.2022.09.039
Abstrakt:	In the mitotic spindle, microtubules attach to chromosomes via kinetochores. The microtubule-binding Ndc80 complex is an integral part of kinetochores, and is essential for kinetochores to attach to microtubules and to transmit forces from dynamic microtubule ends to the chromosomes. The Ndc80 complex has a rod-like appearance with globular domains at its ends that are separated by a long coiled coil. Its mechanical properties are considered important for the dynamic interaction between kinetochores and microtubules. Here, we present a novel method that allows us to time trace the effective stiffness of Ndc80 complexes following shortening microtubule ends against applied force in optical trap experiments. Applying this method to wild-type Ndc80 and three variants (calponin homology (CH) domains mutated or Hec1 tail unphosphorylated, phosphorylated, or truncated), we reveal that each variant exhibits strain stiffening; i.e., the effective stiffness increases under tension that is built up by a depolymerizing microtubule. The strain stiffening relation is roughly linear and independent of the state of the microtubule. We introduce structure-based models that show that the strain stiffening can be traced back to the specific architecture of the Ndc80 complex with a characteristic flexible kink, to thermal fluctuations of the microtubule, and to the bending elasticity of flaring protofilaments, which exert force to move the Ndc80 complexes. Our model accounts for changes in the amount of load-bearing attachments at various force levels and reproduces the roughly linear strain stiffening behavior, highlighting the importance of force-dependent binding affinity. Competing Interests: Declaration of interests The authors declare no competing interests. (Copyright © 2022 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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