Force-dependent Detachment of kinesin-2 Biases Track Switching at Cytoskeletal Filament Intersections

Biophys J. 2012 Jul 3;103(1):48-58. doi: 10.1016/j.bpj.2012.05.037.

Abstract

Intracellular trafficking of organelles often involves cytoskeletal track switching. Organelles such as melanosomes are transported by multiple motors including kinesin-2, dynein, and myosin-V, which drive switching between microtubules and actin filaments during dispersion and aggregation. Here, we used optical trapping to determine the unitary and ensemble forces of kinesin-2, and to reconstitute cargo switching at cytoskeletal intersections in a minimal system with kinesin-2 and myosin-V motors bound to beads. Single kinesin-2 motors exerted forces up to ∼5 pN, similar to kinesin-1. However, kinesin-2 motors were more likely to detach at submaximal forces, and the duration of force maintenance was short as compared to kinesin-1. In multimotor assays, force increased with kinesin-2 density but was not affected by the presence of myosin-V. In crossed filament assays, switching frequencies of motor-bound beads were dependent on the starting track. At equal average forces, beads tended to switch from microtubules onto overlying actin filaments consistent with the relatively faster detachment of kinesin-2 at near-maximal forces. Thus, in addition to relative force, switching probability at filament intersections is determined by the dynamics of motor-filament interaction, such as the quick detachment of kinesin-2 under load. This may enable fine-tuning of filament switching in the cell.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / chemistry
  • Actin Cytoskeleton / physiology*
  • Animals
  • Kinesin / chemistry
  • Kinesin / physiology*
  • Microscopy, Fluorescence
  • Microtubules / physiology*
  • Molecular Dynamics Simulation
  • Myosin Type V / chemistry
  • Myosin Type V / physiology
  • Protein Conformation
  • Rabbits
  • Xenopus
  • Xenopus Proteins / chemistry
  • Xenopus Proteins / physiology*

Substances

  • XKLP3 protein, Xenopus
  • Xenopus Proteins
  • Myosin Type V
  • Kinesin