title: A conserved signal and GTPase complex are required for the ciliary transport of polycystin-1.
abstract: Primary cilia regulate epithelial differentiation and organ function. Failure of mutant polycystins to localize to cilia abolishes flow-stimulated calcium signaling and causes autosomal dominant polycystic kidney disease. We identify a conserved amino acid sequence, KVHPSST, in the C-terminus of polycystin-1 (PC1) that serves as a ciliary-targeting signal. PC1 binds a multimeric protein complex consisting of several GTPases (Arf4, Rab6, Rab11) and the GTPase-activating protein (GAP), ArfGAP with SH3 domain, ankyrin repeat and PH domain 1 (ASAP1) in the Golgi, which facilitates vesicle budding and Golgi exocytosis. A related N-terminal ciliary-targeting sequence in polycystin-2 similarly binds Arf4. Deletion of the extreme C-terminus of PC1 ablates Arf4 and ASAP1 binding and prevents ciliary localization of an integral membrane CD16.7-PC1 chimera. Interactions are confirmed for chimeric and endogenous proteins through quantitated in vitro and cell-based approaches. PC1 also complexes with Rab8; knockdown of trafficking regulators Arf4 or Rab8 functionally blocks CD16.7-PC1 trafficking to cilia. Mutations in rhodopsin disrupt a similar signal and cause retinitis pigmentosa, while Bardet-Biedl syndrome, primary open-angle glaucoma, and tumor cell invasiveness are linked to dysregulation of ASAP1 or Rab8 or its effectors. In this paper, we provide evidence for a conserved GTPase-dependent ciliary-trafficking mechanism that is shared between epithelia and neurons, and is essential in ciliary-trafficking and cell homeostasis.
authors.affiliation: Department of Pathology, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Heather H
authors.initials: HH
authors.lastname: Ward
authors.forename: Ursa
authors.initials: U
authors.lastname: Brown-Glaberman
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Morita
authors.forename: Seth L
authors.initials: SL
authors.lastname: Alper
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Bedrick
authors.forename: Vincent H
authors.initials: VH
authors.lastname: Gattone
authors.forename: Dusanka
authors.initials: D
authors.lastname: Deretic
authors.forename: Angela
authors.initials: A
authors.lastname: Wandinger-Ness
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002923:Cilia / Q000378:metabolism*; D017124:Conserved Sequence; D004285:Dogs; D020690:GTPase-Activating Proteins / Q000378:metabolism; D015870:Gene Expression; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism*; D061251:Primary Cell Culture; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021382:Protein Sorting Signals; D021381:Protein Transport; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050396:TRPP Cation Channels / Q000737:chemistry / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D020727:ADP-Ribosylation Factors; D048868:Adaptor Proteins, Signal Transducing; D020690:GTPase-Activating Proteins; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D050396:TRPP Cation Channels; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C117891:ASAP1 protein, human; C119053:RABGAP1 protein, human; C082377:RAB8A protein, human; C116688:ARF4 protein, human