Biophysical Society Thematic Meeting | Riga 2026

Active and Responsive Soft Matter: From Biological to Engineered Systems

Poster Abstracts

9-POS Board 9 MECHANICAL TENSION EXTENDS THE MICROTUBULE LATTICE AND MODULATES KINESIN-1 BINDING IN AN ISOFORM-DEPENDENT MANNER Yannic Lurz 1 ; Benedikt Fischer 1 ; Jaya Mishra 2 ; Laura Muras 1 ; Erik Schäffer 1 ; Nisha Mohd Rafiq 2 ; E. Michael Ostap 3 ; Igor Kulic 4 ; Serapion Pyrpassopoulos 1 ; 1 University of Tübingen, Center for Plant Molecular Biology, Tübingen, Germany 2 University of Tübingen, Interfaculty Institute of Biochemistry , Tuebingen, Germany 3 University of Pennsylvania, Department of Physiology, Philadelphia, PA, USA 4 CNRS, Institute Charles Sadron, Strasbourg, France Recent work has shown that the microtubule lattice possesses remarkable structural plasticity, with its conformation modulated by microtubule-associated proteins and motor proteins. However, how this plasticity responds to mechanical forces remains poorly understood. Here, we developed optical tweezers and fluorescence microscopy assays to measure the effect of tensile forces on single microtubules. Decorating microtubules with quantum dots enabled nanometre precision measurement of mechanical lattice distortions of ~0.33% under a mean tensile force of ⟨ ΔF ⟩ = 10.4 pN, within the range F min = 1.29 pN to F max = 20.4 pN — comparable to forces generated by one to three kinesin-1 or cytoplasmic dynein motors. Within this force range, the mean binding rate of KIF5B decreased within seconds by ~20% and its mean dissociation rate increased by ~10%, resulting in a reduction in mean run length. This response was not uniform across microtubules subjected to similar tensile forces; in extreme cases, run length decreased by up to 46% under tension. Substantial heterogeneity was also observed along individual microtubules, where distinct lattice regions responded differently to applied force, implying that tensile-force-induced lattice expansion is not always uniform along a single microtubule. Similar heterogeneity was observed in cells: when MAPs with competing conformational preferences are overexpressed, they assemble in non-overlapping patches along the same microtubule. These observations are consistent with a dynamic polymorphic lattice model, in which mechanical stress differentially stabilises distinct structural configurations, as supported by Brownian dynamics simulations and a statistical mechanical Ising model based on the conformational bistability of the tubulin building block. Strikingly, no statistically significant effects were observed for KIF5C within the same force range, revealing an isoform-dependent mechanoresponse. Together, these findings establish microtubules as bona fide mechanochemical signal transducers, converting mechanical forces into biochemical signals across distances spanning the cell body with the speed and sensitivity required for rapid cellular responses.

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