Arl13b and the exocyst interact synergistically in ciliogenesis

• Type of Material: Article
• Authors: Cecília Seixas, Universidade Nova de Lisbo; Soo Young Choi, Medical University of South Carolina; Noemi Polgar, University of Hawaii at Manoa; Nicole Umberger, Emory University; Michael P. East, Emory University; Xiaofeng Zuo, Medical University of South Carolina; Hugo Moreiras, Universidade Nova de Lisboa; Rania Ghossoub, Centre de Recherche en Cancérologie de Marseille; Alexandre Benmerah, Laboratory of Inherited Kidney Diseases, France; Richard Kahn, Emory University; Ben Fogelgren, University of Hawaii at Manoa; Tamara Caspary, Emory University; Joshua H. Lipschutz, Medical University of South Carolina; Duarte C. Barral, Universidade Nova de Lisboa
• Language: English
• Date: 2016-01-15
• Publisher: American Society for Cell Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2016 Seixas et al.
• License: Creative Commons Attribution 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1091/mbc.E15-02-0061
• Title of Journal or Parent Work: Molecular Biology of the Cell
• ISSN: 1059-1524
• Volume: 27
• Issue: 2
• Start Page: 308
• End Page: 320
• Grant/Funding Information: Funding for B.F. was obtained from the National Institutes of Health (1K01DK087852, R03DK100738, and P20GM103456-06A1-8293), the March of Dimes (#5-FY14-56), and Pilot and Feasibility Awards, as well as from National Institutes of Health–Designated Research Centers 5G12MD007601 and 5P30DK074038.; Funding for A.B. was obtained from the Fondation pour la Recherche Médicale (DEQ20130326532).; This work was supported by a Marie Curie International Reintegration Grant (PIRG05-GA-2009-247726) and a grant from Câmara Municipal de Oeiras to D.C.B., postdoctoral fellowships from the Fundação para a Ciência e a Tecnologia (SFRH/BPD/32323/2006 and iNOVA4Health‐UID/Multi/04462/2013) to C.S., and research funding from the National Institute of Neurological Disorders and Stroke (R01 NS056380) to T.C. and from the National Institute of General Medical Sciences (GM090158) to R.A.K.; It was also supported by predoctoral fellowships from the American Heart Association (09PRE2140029) to M.P.E.; an Emory PRISM Graduate Teaching Fellows in K-12 Education Fellowship (DGE0536941), an Emory Genetics and Molecular Biology Graduate Program Training Grant (T32GM008490), and an Emory Human Disease Genetics Training Fellowship (T32MH087977) to N.L.U. Funding to J.H.L. was obtained from the Veterans Administration (Merit Award I01 BX000820), the National Institutes of Health (DK069909 and DK070980), and Satellite Healthcare (Norman S. Coplon Extramural Research Grant).
• Keywords: TRAFFICKING; NERVOUS-SYSTEM; Science & Technology; Life Sciences & Biomedicine; Cell Biology; EFFECTOR; JOUBERT-SYNDROME; MEMBRANE; PRIMARY CILIA; DISEASE; KIDNEY; EPITHELIAL-CELLS; TRANSPORT
• Research Categories: Chemistry, Biochemistry; Biology, Genetics; Health Sciences, General

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.