Diffusible crosslinkers generate directed forces in microtubule networks.
Cytoskeletal remodeling is essential to eukaryotic cell division and morphogenesis. The mechanical forces driving the restructuring are attributed to the action of molecular motors and the dynamics of cytoskeletal filaments, which both consume chemical energy. By contrast, non-enzymatic filament crosslinkers are regarded as mere friction-generating entities. Here, we experimentally demonstrate that diffusible microtubule crosslinkers of the Ase1/PRC1/Map65 family generate directed microtubule sliding when confined between partially overlapping microtubules. The Ase1-generated forces, directly measured by optical tweezers to be in the piconewton-range, were sufficient to antagonize motor-protein driven microtubule sliding. Force generation is quantitatively explained by the entropic expansion of confined Ase1 molecules diffusing within the microtubule overlaps. The thermal motion of crosslinkers is thus harnessed to generate mechanical work analogous to compressed gas propelling a piston in a cylinder. As confinement of diffusible proteins is ubiquitous in cells, the associated entropic forces are likely of importance for cellular mechanics beyond cytoskeletal networks.
B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
Zdenek
Z
Lansky
B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
Marcus
M
Braun
B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany.
Annemarie
A
Lüdecke
B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany.
Michael
M
Schlierf
AMOLF, Science Park 104, 1098 XG Amsterdam, the Netherlands. Electronic address: tenwolde@amolf.nl.
Pieter Rein
PR
ten Wolde
Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands. Electronic address: marcel.janson@wur.nl.
Marcel E
ME
Janson
B CUBE - Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany; Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany. Electronic address: diez@bcube-dresden.de.
Stefan
S
Diez
D000818:Animals; D001696:Biomechanical Phenomena; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000378:metabolism; D017276:Friction; D049452:Green Fluorescent Proteins / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D052898:Optical Tweezers; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism
C502827:Ase1 protein, S pombe; D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; D029702:Schizosaccharomyces pombe Proteins; C066696:ncd protein, Drosophila; D049452:Green Fluorescent Proteins; D016547:Kinesins