Asymmetric friction of nonmotor MAPs can lead to their directional motion in active microtubule networks

Cell. 2014 Apr 10;157(2):420-432. doi: 10.1016/j.cell.2014.02.018.


Diverse cellular processes require microtubules to be organized into distinct structures, such as asters or bundles. Within these dynamic motifs, microtubule-associated proteins (MAPs) are frequently under load, but how force modulates these proteins' function is poorly understood. Here, we combine optical trapping with TIRF-based microscopy to measure the force dependence of microtubule interaction for three nonmotor MAPs (NuMA, PRC1, and EB1) required for cell division. We find that frictional forces increase nonlinearly with MAP velocity across microtubules and depend on filament polarity, with NuMA's friction being lower when moving toward minus ends, EB1's lower toward plus ends, and PRC1's exhibiting no directional preference. Mathematical models predict, and experiments confirm, that MAPs with asymmetric friction can move directionally within actively moving microtubule pairs they crosslink. Our findings reveal how nonmotor MAPs can generate frictional resistance in dynamic cytoskeletal networks via micromechanical adaptations whose anisotropy may be optimized for MAP localization and function within cellular structures.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Antigens, Nuclear / chemistry
  • Antigens, Nuclear / metabolism*
  • Biomechanical Phenomena
  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / metabolism*
  • Microscopy, Fluorescence
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / metabolism*
  • Models, Biological
  • Nuclear Matrix-Associated Proteins / chemistry
  • Nuclear Matrix-Associated Proteins / metabolism*
  • Optical Tweezers


  • Antigens, Nuclear
  • Cell Cycle Proteins
  • MAPRE1 protein, human
  • Microtubule-Associated Proteins
  • NUMA1 protein, human
  • Nuclear Matrix-Associated Proteins
  • PRC1 protein, human