An estimate to the first approximation of microtubule rupture force
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Microtubule mechanical properties are essential for understanding basic cellular processes, including cell motility and division, but the forces that result in microtubule rupture or breakage have not yet been measured directly. These forces are essential to understand the mechanical properties of the cytoskeleton and responses by cells to both normal conditions and stress caused by injury or disease. Here we estimate the force required to rupture a microtubule by analyzing kinesin-14 Ncd motor-induced microtubule breakage in ensemble motility assays. We model the breakage events as caused by Ncd motors pulling or pushing on single microtubules that are clamped at one end by other motors attached to the glass surface. The number of pulling or pushing Ncd motors is approximated from the length of the microtubule bound to the surface and the forces produced by the pulling or pushing motors are estimated from forces produced by the Ncd motor in laser-trap assays, reported by others. Our analysis provides an estimate, to the first approximation, of ~ 500 pN for the minimal force required to rupture a 13-pf microtubule. The value we report is close to the forces estimated from microtubule stretching/fragmentation experiments and overlaps with the forces applied by AFM in microtubule indentation assays that destabilize microtubules and break microtubule protofilaments. It is also consistent with the forces required to disrupt protein noncovalent bonds in force spectroscopy experiments. These findings are relevant to microtubule deformation and breakage caused by cellular tension in vivo.
KeywordsMicrotubules Rupture force Kinesin-14 motor Motor force generation Microtubule gliding assays
This study was supported by US National Science Foundation Grant #CMMI-1660924 to SAE and #MCB-1517245 to PEM. Any opinions, findings, conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the National Science Foundation. We thank Shin'ichi Ishiwata for valuable discussions.
SAE designed the study, analyzed data, prepared figures and wrote the manuscript; PEM contributed to data analysis and interpretation, and manuscript writing.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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