title: Active transport and diffusion barriers restrict Joubert Syndrome-associated ARL13B/ARL-13 to an Inv-like ciliary membrane subdomain.
abstract: Cilia are microtubule-based cell appendages, serving motility, chemo-/mechano-/photo- sensation, and developmental signaling functions. Cilia are comprised of distinct structural and functional subregions including the basal body, transition zone (TZ) and inversin (Inv) compartments, and defects in this organelle are associated with an expanding spectrum of inherited disorders including Bardet-Biedl syndrome (BBS), Meckel-Gruber Syndrome (MKS), Joubert Syndrome (JS) and Nephronophthisis (NPHP). Despite major advances in understanding ciliary trafficking pathways such as intraflagellar transport (IFT), how proteins are transported to subciliary membranes remains poorly understood. Using Caenorhabditis elegans and mammalian cells, we investigated the transport mechanisms underlying compartmentalization of JS-associated ARL13B/ARL-13, which we previously found is restricted at proximal ciliary membranes. We now show evolutionary conservation of ARL13B/ARL-13 localisation to an Inv-like subciliary membrane compartment, excluding the TZ, in many C. elegans ciliated neurons and in a subset of mammalian ciliary subtypes. Compartmentalisation of C. elegans ARL-13 requires a C-terminal RVVP motif and membrane anchoring to prevent distal cilium and nuclear targeting, respectively. Quantitative imaging in more than 20 mutants revealed differential contributions for IFT and ciliopathy modules in defining the ARL-13 compartment; IFT-A/B, IFT-dynein and BBS genes prevent ARL-13 accumulation at periciliary membranes, whereas MKS/NPHP modules additionally inhibit ARL-13 association with TZ membranes. Furthermore, in vivo FRAP analyses revealed distinct roles for IFT and MKS/NPHP genes in regulating a TZ barrier to ARL-13 diffusion, and intraciliary ARL-13 diffusion. Finally, C. elegans ARL-13 undergoes IFT-like motility and quantitative protein complex analysis of human ARL13B identified functional associations with IFT-B complexes, mapped to IFT46 and IFT74 interactions. Together, these findings reveal distinct requirements for sequence motifs, IFT and ciliopathy modules in defining an ARL-13 subciliary membrane compartment. We conclude that MKS/NPHP modules comprise a TZ barrier to ARL-13 diffusion, whereas IFT genes predominantly facilitate ARL-13 ciliary entry and/or retention via active transport mechanisms.
authors: School of Biomolecular and Biomedical Science, University College Dublin, Belfield, Dublin, Ireland.
authors: Sebiha
authors: S
authors: Cevik
authors: Anna A W M
authors: AA
authors: Sanders
authors: Erwin
authors: E
authors: Van Wijk
authors: Karsten
authors: K
authors: Boldt
authors: Lara
authors: L
authors: Clarke
authors: Jeroen
authors: J
authors: van Reeuwijk
authors: Yuji
authors: Y
authors: Hori
authors: Nicola
authors: N
authors: Horn
authors: Lisette
authors: L
authors: Hetterschijt
authors: Anita
authors: A
authors: Wdowicz
authors: Andrea
authors: A
authors: Mullins
authors: Katarzyna
authors: K
authors: Kida
authors: Oktay I
authors: OI
authors: Kaplan
authors: Sylvia E C
authors: SE
authors: van Beersum
authors: Ka
authors: K
authors: Man Wu
authors: Stef J F
authors: SJ
authors: Letteboer
authors: Dorus A
authors: DA
authors: Mans
authors: Toshiaki
authors: T
authors: Katada
authors: Kenji
authors: K
authors: Kontani
authors: Marius
authors: M
authors: Ueffing
authors: Ronald
authors: R
authors: Roepman
authors: Hannie
authors: H
authors: Kremer
authors: Oliver E
authors: OE
authors: Blacque
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics* / Q000378:metabolism; D000015:Abnormalities, Multiple; D000818:Animals; D020788:Bardet-Biedl Syndrome / Q000235:genetics / Q000473:pathology; D001693:Biological Transport, Active / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D002526:Cerebellar Diseases / Q000235:genetics* / Q000473:pathology; D002531:Cerebellum / Q000002:abnormalities; D002923:Cilia / Q000235:genetics* / Q000378:metabolism; D002925:Ciliary Motility Disorders / Q000235:genetics / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004677:Encephalocele / Q000235:genetics / Q000473:pathology; D005124:Eye Abnormalities / Q000235:genetics* / Q000473:pathology; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000235:genetics* / Q000473:pathology; D008566:Membranes / Q000378:metabolism; D007690:Polycystic Kidney Diseases / Q000235:genetics / Q000473:pathology; D012160:Retina / Q000002:abnormalities* / Q000473:pathology; D012174:Retinitis Pigmentosa; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; C490080:IFT74 protein, human; C114503:INVS protein, human; D014157:Transcription Factors; D020727:ADP-Ribosylation Factors; C530391:ARL13B protein, human