Functional differentiation of cooperating kinesin-2 motors orchestrates cargo import and transport in C. elegans cilia

Nat Cell Biol. 2015 Dec;17(12):1536-45. doi: 10.1038/ncb3263. Epub 2015 Nov 2.


Intracellular transport depends on cooperation between distinct motor proteins. Two anterograde intraflagellar transport (IFT) motors, heterotrimeric kinesin-II and homodimeric OSM-3, cooperate to move cargo along Caenorhabditis elegans cilia. Here, using quantitative fluorescence microscopy, with single-molecule sensitivity, of IFT in living strains containing single-copy transgenes encoding fluorescent IFT proteins, we show that kinesin-II transports IFT trains through the ciliary base and transition zone to a 'handover zone' on the proximal axoneme. There, OSM-3 gradually replaces kinesin-II, yielding velocity profiles inconsistent with in vitro motility assays, and then drives transport to the ciliary tip. Dissociated kinesin-II motors undergo rapid turnaround and recycling to the ciliary base, whereas OSM-3 is recycled mainly to the handover zone. This reveals a functional differentiation in which the slower, less processive kinesin-II imports IFT trains into the cilium and OSM-3 drives their long-range transport, thereby optimizing cargo delivery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • A Kinase Anchor Proteins / genetics
  • A Kinase Anchor Proteins / metabolism
  • Algorithms
  • Animals
  • Biological Transport / genetics
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / chemistry
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Cilia / metabolism*
  • Computer Simulation
  • Kinesin / chemistry
  • Kinesin / genetics
  • Kinesin / metabolism*
  • Kinetics
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Microscopy, Fluorescence
  • Models, Biological
  • Mutation
  • Protein Multimerization
  • Video Recording


  • A Kinase Anchor Proteins
  • A kinase anchor protein (kap-1), C elegans
  • Caenorhabditis elegans Proteins
  • Luminescent Proteins
  • OSM-3 protein, C elegans
  • kinesin-II
  • Kinesin