Ciliary entry of KIF17 is dependent on its binding to the IFT-B complex via IFT46-IFT56 as well as on its nuclear localization signal

Mol Biol Cell. 2017 Mar 1;28(5):624-633. doi: 10.1091/mbc.E16-09-0648. Epub 2017 Jan 11.

Abstract

Cilia function as cellular antennae to sense and transduce extracellular signals. A number of proteins are specifically localized in cilia. Anterograde and retrograde ciliary protein trafficking are mediated by the IFT-B and IFT-A complexes in concert with kinesin-2 and dynein-2 motors, respectively. However, the role of KIF17, a homodimeric kinesin-2 protein, in protein trafficking has not been fully understood in vertebrate cilia. In this study, we demonstrated, by using the visible immunoprecipitation assay, that KIF17 interacts with the IFT46-IFT56 dimer in the IFT-B complex through its C-terminal sequence located immediately upstream of the nuclear localization signal (NLS). We then showed that KIF17 reaches the ciliary tip independently of its motor domain and requires IFT-B binding for its entry into cilia rather than for its intraciliary trafficking. We further showed that KIF17 ciliary entry depends not only on its binding to IFT-B but also on its NLS, to which importin α proteins bind. Taking the results together, we conclude that in mammalian cells, KIF17 is dispensable for ciliogenesis and IFT-B trafficking but requires IFT-B, as well as its NLS, for its ciliary entry across the permeability barrier located at the ciliary base.

MeSH terms

  • Axoneme / metabolism
  • Carrier Proteins / metabolism*
  • Cell Line
  • Cilia / metabolism*
  • Dyneins / metabolism
  • Flagella / metabolism
  • Gene Knockout Techniques
  • Humans
  • Kinesins / metabolism*
  • Molecular Motor Proteins / metabolism*
  • Nuclear Localization Signals / metabolism
  • Protein Transport / physiology
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / metabolism

Substances

  • Carrier Proteins
  • KIF17 protein, human
  • KIF2A protein, human
  • Molecular Motor Proteins
  • Nuclear Localization Signals
  • Dyneins
  • Kinesins