The CEP19-RABL2 GTPase Complex Binds IFT-B to Initiate Intraflagellar Transport at the Ciliary Base

Dev Cell. 2017 Jul 10;42(1):22-36.e12. doi: 10.1016/j.devcel.2017.05.016. Epub 2017 Jun 15.

Abstract

Highly conserved intraflagellar transport (IFT) protein complexes direct both the assembly of primary cilia and the trafficking of signaling molecules. IFT complexes initially accumulate at the base of the cilium and periodically enter the cilium, suggesting an as-yet-unidentified mechanism that triggers ciliary entry of IFT complexes. Using affinity-purification and mass spectrometry of interactors of the centrosomal and ciliopathy protein, CEP19, we identify CEP350, FOP, and the RABL2B GTPase as proteins organizing the first known mechanism directing ciliary entry of IFT complexes. We discover that CEP19 is recruited to the ciliary base by the centriolar CEP350/FOP complex and then specifically captures GTP-bound RABL2B, which is activated via its intrinsic nucleotide exchange. Activated RABL2B then captures and releases its single effector, the intraflagellar transport B holocomplex, from the large pool of pre-docked IFT-B complexes, and thus initiates ciliary entry of IFT.

Keywords: CEP19; CEP350; FGFR1OP; RABL2; cilia; ciliopathy; intraflagellar transport; obesity; retinal degeneration; small GTPase.

Publication types

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

MeSH terms

  • Animals
  • Cell Cycle Proteins / metabolism*
  • Centrioles / metabolism
  • Cilia / metabolism*
  • Ciliopathies
  • Flagella / metabolism*
  • Gene Knockout Techniques
  • Guanosine Triphosphate / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Multiprotein Complexes / metabolism*
  • Nucleotides / metabolism
  • Phenotype
  • Protein Binding
  • Protein Stability
  • Protein Transport
  • Reproducibility of Results
  • rab GTP-Binding Proteins / deficiency
  • rab GTP-Binding Proteins / metabolism*

Substances

  • CEP19 protein, human
  • Cell Cycle Proteins
  • Multiprotein Complexes
  • Nucleotides
  • Guanosine Triphosphate
  • RABL2 protein, mouse
  • RABL2A protein, human
  • rab GTP-Binding Proteins