Joubert syndrome Arl13b functions at ciliary membranes and stabilizes protein transport in Caenorhabditis elegans.
The small ciliary G protein Arl13b is required for cilium biogenesis and sonic hedgehog signaling and is mutated in patients with Joubert syndrome (JS). In this study, using Caenorhabditis elegans and mammalian cell culture systems, we investigated the poorly understood ciliary and molecular basis of Arl13b function. First, we show that Arl13b/ARL-13 localization is frequently restricted to a proximal ciliary compartment, where it associates with ciliary membranes via palmitoylation modification motifs. Next, we find that loss-of-function C. elegans arl-13 mutants possess defects in cilium morphology and ultrastructure, as well as defects in ciliary protein localization and transport; ciliary transmembrane proteins abnormally accumulate, PKD-2 ciliary abundance is elevated, and anterograde intraflagellar transport (IFT) is destabilized. Finally, we show that arl-13 interacts genetically with other ciliogenic and ciliary transport-associated genes in maintaining cilium structure/morphology and anterograde IFT stability. Together, these data implicate a role for JS-associated Arl13b at ciliary membranes, where it regulates ciliary transmembrane protein localizations and anterograde IFT assembly stability.
School of Biomolecular and Biomedical Science and 2 Electron Microscopy Laboratory, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland.
Sebiha
S
Cevik
Yuji
Y
Hori
Oktay I
OI
Kaplan
Katarzyna
K
Kida
Tiina
T
Toivenon
Christian
C
Foley-Fisher
David
D
Cottell
Toshiaki
T
Katada
Kenji
K
Kontani
Oliver E
OE
Blacque
D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D002923:Cilia / Q000235:genetics / Q000378:metabolism; D004285:Dogs; D006801:Humans; D021381:Protein Transport
D020727:ADP-Ribosylation Factors