FLA8/KIF3B phosphorylation regulates kinesin-II interaction with IFT-B to control IFT entry and turnaround

Dev Cell. 2014 Sep 8;30(5):585-97. doi: 10.1016/j.devcel.2014.07.019. Epub 2014 Aug 28.


The assembly and maintenance of cilia depends on intraflagellar transport (IFT). Activated IFT motor kinesin-II enters the cilium with loaded IFT particles comprising IFT-A and IFT-B complexes. At the ciliary tip, kinesin-II becomes inactivated, and IFT particles are released. Moreover, the rate of IFT entry is dynamically regulated during cilium assembly. However, the regulatory mechanism of IFT entry and loading/unloading of IFT particles remains elusive. We show that the kinesin-II motor subunit FLA8, a homolog of KIF3B, is phosphorylated on the conserved S663 by a calcium-dependent kinase in Chlamydomonas. This phosphorylation disrupts the interaction between kinesin-II and IFT-B, inactivates kinesin-II and inhibits IFT entry, and is also required for IFT-B unloading at the ciliary tip. Furthermore, our data suggest that the IFT entry rate is controlled by regulation of the cellular level of phosphorylated FLA8. Therefore, FLA8 phosphorylation acts as a molecular switch to control IFT entry and turnaround.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Biological Transport
  • Calcium-Binding Proteins / metabolism*
  • Chlamydomonas reinhardtii / metabolism*
  • Cilia / metabolism
  • Flagella / physiology*
  • Gene Expression Regulation, Plant*
  • Kinesins / metabolism*
  • Molecular Sequence Data
  • Phosphorylation
  • Plant Proteins / metabolism
  • Sequence Homology, Amino Acid


  • Calcium-Binding Proteins
  • Plant Proteins
  • kinesin-II
  • Kinesins