Arl13b and the exocyst interact synergistically in ciliogenesis

Mol Biol Cell. 2016 Jan 15;27(2):308-20. doi: 10.1091/mbc.E15-02-0061. Epub 2015 Nov 18.

Abstract

Arl13b belongs to the ADP-ribosylation factor family within the Ras superfamily of regulatory GTPases. Mutations in Arl13b cause Joubert syndrome, which is characterized by congenital cerebellar ataxia, hypotonia, oculomotor apraxia, and mental retardation. Arl13b is highly enriched in cilia and is required for ciliogenesis in multiple organs. Nevertheless, the precise role of Arl13b remains elusive. Here we report that the exocyst subunits Sec8, Exo70, and Sec5 bind preferentially to the GTP-bound form of Arl13b, consistent with the exocyst being an effector of Arl13b. Moreover, we show that Arl13b binds directly to Sec8 and Sec5. In zebrafish, depletion of arl13b or the exocyst subunit sec10 causes phenotypes characteristic of defective cilia, such as curly tail up, edema, and abnormal pronephric kidney development. We explored this further and found a synergistic genetic interaction between arl13b and sec10 morphants in cilia-dependent phenotypes. Through conditional deletion of Arl13b or Sec10 in mice, we found kidney cysts and decreased ciliogenesis in cells surrounding the cysts. Moreover, we observed a decrease in Arl13b expression in the kidneys from Sec10 conditional knockout mice. Taken together, our results indicate that Arl13b and the exocyst function together in the same pathway leading to functional cilia.

Publication types

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

MeSH terms

  • ADP-Ribosylation Factors / genetics
  • ADP-Ribosylation Factors / metabolism*
  • Abnormalities, Multiple
  • Animals
  • Cerebellum / abnormalities
  • Cilia / metabolism*
  • Eye Abnormalities
  • Genetic Association Studies
  • HeLa Cells
  • Humans
  • Kidney / metabolism
  • Kidney Diseases, Cystic
  • Mice
  • Mice, Knockout
  • Microtubules / metabolism
  • Mutation
  • NIH 3T3 Cells
  • Retina / abnormalities
  • Vesicular Transport Proteins / metabolism
  • Zebrafish
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism

Substances

  • Arl13b protein, mouse
  • Vesicular Transport Proteins
  • Zebrafish Proteins
  • ADP-Ribosylation Factors
  • Arl13b protein, human
  • Arl13b protein, zebrafish

Supplementary concepts

  • Agenesis of Cerebellar Vermis