scholarly journals Induction of Ran GTP drives ciliogenesis

2011 ◽  
Vol 22 (23) ◽  
pp. 4539-4548 ◽  
Author(s):  
Shuling Fan ◽  
Eileen L. Whiteman ◽  
Toby W. Hurd ◽  
Jeremy C. McIntyre ◽  
John F. Dishinger ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Protein Transport ◽  
Nucleocytoplasmic Transport ◽  
Small Gtpase ◽  
Basal Bodies ◽  
Ciliary Protein ◽  
Cilia Formation ◽  
Ran Gtp ◽  
New Evidence ◽  
Gtpase Ran

The small GTPase Ran and the importin proteins regulate nucleocytoplasmic transport. New evidence suggests that Ran GTP and the importins are also involved in conveying proteins into cilia. In this study, we find that Ran GTP accumulation at the basal bodies is coordinated with the initiation of ciliogenesis. The Ran-binding protein 1 (RanBP1), which indirectly accelerates Ran GTP → Ran GDP hydrolysis and promotes the dissociation of the Ran/importin complex, also localizes to basal bodies and cilia. To confirm the crucial link between Ran GTP and ciliogenesis, we manipulated the levels of RanBP1 and determined the effects on Ran GTP and primary cilia formation. We discovered that RanBP1 knockdown results in an increased concentration of Ran GTP at basal bodies, leading to ciliogenesis. In contrast, overexpression of RanBP1 antagonizes primary cilia formation. Furthermore, we demonstrate that RanBP1 knockdown disrupts the proper localization of KIF17, a kinesin-2 motor, at the distal tips of primary cilia in Madin–Darby canine kidney cells. Our studies illuminate a new function for Ran GTP in stimulating cilia formation and reinforce the notion that Ran GTP and the importins play key roles in ciliogenesis and ciliary protein transport.

scholarly journals Midbody remnant licenses primary cilia formation in epithelial cells

2016 ◽  
Vol 214 (3) ◽  
pp. 237-239 ◽  
Author(s):  
Carolyn M. Ott
Keyword(s):  
Epithelial Cells ◽  
Primary Cilia ◽  
Cell Biol ◽  
Cilia Formation ◽  
Polarized Epithelial Cells ◽  
New Evidence

Tethered midbody remnants dancing across apical microvilli, encountering the centrosome, and beckoning forth a cilium—who would have guessed this is how polarized epithelial cells coordinate the end of mitosis and the beginning of ciliogenesis? New evidence from Bernabé-Rubio et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601020) supports this emerging model.

scholarly journals Transport into and out of the Nucleus

2001 ◽  
Vol 65 (4) ◽  
pp. 570-594 ◽  
Author(s):  
Ian G. Macara
Keyword(s):  
Rna Processing ◽  
Nucleocytoplasmic Transport ◽  
Small Gtpase ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Facilitated Diffusion ◽  
Transport Mechanisms ◽  
Pore Complexes ◽  
Transport Of Macromolecules ◽  
Gtpase Ran

SUMMARY A defining characteristic of eukaryotic cells is the possession of a nuclear envelope. Transport of macromolecules between the nuclear and cytoplasmic compartments occurs through nuclear pore complexes that span the double membrane of this envelope. The molecular basis for transport has been revealed only within the last few years. The transport mechanism lacks motors and pumps and instead operates by a process of facilitated diffusion of soluble carrier proteins, in which vectoriality is provided by compartment-specific assembly and disassembly of cargo-carrier complexes. The carriers recognize localization signals on the cargo and can bind to pore proteins. They also bind a small GTPase, Ran, whose GTP-bound form is predominantly nuclear. Ran-GTP dissociates import carriers from their cargo and promotes the assembly of export carriers with cargo. The ongoing discovery of numerous carriers, Ran-independent transport mechanisms, and cofactors highlights the complexity of the nuclear transport process. Multiple regulatory mechanisms are also being identified that control cargo-carrier interactions. Circadian rhythms, cell cycle, transcription, RNA processing, and signal transduction are all regulated at the level of nucleocytoplasmic transport. This review focuses on recent discoveries in the field, with an emphasis on the carriers and cofactors involved in transport and on possible mechanisms for movement through the nuclear pores.

scholarly journals BAR Domain-Containing FAM92 Proteins Interact with Chibby1 To Facilitate Ciliogenesis

2016 ◽  
Vol 36 (21) ◽  
pp. 2668-2680 ◽  
Author(s):  
Feng-Qian Li ◽  
Xingwang Chen ◽  
Cody Fisher ◽  
Saul S. Siller ◽  
Klara Zelikman ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Cultured Cells ◽  
Sequence Similarity ◽  
Affinity Purification ◽  
Coiled Coil ◽  
Lipid Binding ◽  
Small Gtpase ◽  
Basal Bodies ◽  
Membrane Remodeling ◽  
Bar Domains

Chibby1 (Cby1) is a small, conserved coiled-coil protein that localizes to centrioles/basal bodies and plays a crucial role in the formation and function of cilia. During early stages of ciliogenesis, Cby1 is required for the efficient recruitment of small vesicles at the distal end of centrioles to facilitate basal body docking to the plasma membrane. Here, we identified family with sequence similarity 92, member A (FAM92A) and FAM92B, which harbor predicted lipid-binding BAR domains, as novel Cby1-interacting partners using tandem affinity purification and mass spectrometry. We found that in cultured cell lines, FAM92A colocalizes with Cby1 at the centrioles/basal bodies of primary cilia, while FAM92B is undetectable. In airway multiciliated cells, both FAM92A and -92B colocalize with Cby1 at the base of cilia. Notably, the centriolar localization of FAM92A and -92B depends largely on Cby1. Knockdown of FAM92A in RPE1 cells impairs ciliogenesis. Consistent with the membrane-remodeling properties of BAR domains, FAM92A and -92B in cooperation with Cby1 induce deformed membrane-like structures containing the small GTPase Rab8 in cultured cells. Our results therefore suggest that FAM92 proteins interact with Cby1 to promote ciliogenesis via regulation of membrane-remodeling processes.

scholarly journals Systematic proteomic analysis of LRRK2-mediated Rab GTPase phosphorylation establishes a connection to ciliogenesis

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Martin Steger ◽  
Federico Diez ◽  
Herschel S Dhekne ◽  
Pawel Lis ◽  
Raja S Nirujogi ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Protein Transport ◽  
Serum Starvation ◽  
Rab Gtpase ◽  
Rab Gtpases ◽  
Rab Protein ◽  
Affinity Enrichment ◽  
Fold Reduction ◽  
Cilia Formation ◽  
Conserved Residue

We previously reported that Parkinson’s disease (PD) kinase LRRK2 phosphorylates a subset of Rab GTPases on a conserved residue in their switch-II domains (Steger et al., 2016) (PMID: 26824392). Here, we systematically analyzed the Rab protein family and found 14 of them (Rab3A/B/C/D, Rab5A/B/C, Rab8A/B, Rab10, Rab12, Rab29, Rab35 and Rab43) to be specifically phosphorylated by LRRK2, with evidence for endogenous phosphorylation for ten of them (Rab3A/B/C/D, Rab8A/B, Rab10, Rab12, Rab35 and Rab43). Affinity enrichment mass spectrometry revealed that the primary ciliogenesis regulator, RILPL1 specifically interacts with the LRRK2-phosphorylated forms of Rab8A and Rab10, whereas RILPL2 binds to phosphorylated Rab8A, Rab10, and Rab12. Induction of primary cilia formation by serum starvation led to a two-fold reduction in ciliogenesis in fibroblasts derived from pathogenic LRRK2-R1441G knock-in mice. These results implicate LRRK2 in primary ciliogenesis and suggest that Rab-mediated protein transport and/or signaling defects at cilia may contribute to LRRK2-dependent pathologies.

scholarly journals On the asymmetric partitioning of nucleocytoplasmic transport – recent insights and open questions

2021 ◽  
Vol 134 (7) ◽  
Author(s):  
Joanna Kalita ◽  
Larisa E. Kapinos ◽  
Roderick Y. H. Lim
Keyword(s):  
Nucleocytoplasmic Transport ◽  
Small Gtpase ◽  
Nuclear Pore ◽  
Permeability Barrier ◽  
Soluble Factors ◽  
Guanosine Diphosphate ◽  
Open Questions ◽  
Cargo Delivery ◽  
Asymmetric Partitioning ◽  
Gtpase Ran

ABSTRACT Macromolecular cargoes are asymmetrically partitioned in the nucleus or cytoplasm by nucleocytoplasmic transport (NCT). At the center of this activity lies the nuclear pore complex (NPC), through which soluble factors circulate to orchestrate NCT. These include cargo-carrying importin and exportin receptors from the β-karyopherin (Kapβ) family and the small GTPase Ran, which switches between guanosine triphosphate (GTP)- and guanosine diphosphate (GDP)-bound forms to regulate cargo delivery and compartmentalization. Ongoing efforts have shed considerable light on how these soluble factors traverse the NPC permeability barrier to sustain NCT. However, this does not explain how importins and exportins are partitioned in the cytoplasm and nucleus, respectively, nor how a steep RanGTP–RanGDP gradient is maintained across the nuclear envelope. In this Review, we peel away the multiple layers of control that regulate NCT and juxtapose unresolved features against known aspects of NPC function. Finally, we discuss how NPCs might function synergistically with Kapβs, cargoes and Ran to establish the asymmetry of NCT.

scholarly journals XMog1, a nuclear Ran-binding protein in Xenopus, is a functional homologue of Schizosaccharomyces pombe Mog1p that co-operates with RanBP1 to control generation of Ran-GTP

2001 ◽  
Vol 114 (16) ◽  
pp. 3013-3023 ◽  
Author(s):  
Francisco J. Nicolás ◽  
William J. Moore ◽  
Chuanmao Zhang ◽  
Paul R. Clarke
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Mammalian Cells ◽  
Binding Protein ◽  
Nucleocytoplasmic Transport ◽  
Small Gtpase ◽  
Growth Defect ◽  
Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Ran Gtp ◽  
Nuclear Envelope Formation

Ran is a multifunctional small GTPase of the Ras superfamily that plays roles in nucleocytoplasmic transport, mitotic spindle assembly and nuclear envelope formation. By screening a Xenopus oocyte cDNA library for Ran-GTP-binding proteins using the two-hybrid system of co-expression in yeast, we identified XMog1, a 20.4 kDa polypeptide related to Mog1p in Saccharomyces cerevisiae and similar gene products in Schizosaccharomyces pombe, Arabidopsis and mammals. We show that cDNAs encoding XMog1 and S. cerevisiae Mog1p rescue the growth defect of S. pombe cells lacking mog1, demonstrating conservation of their functions. In Xenopus somatic cells and transfected mammalian cells, XMog1 is localised to the nucleus. XMog1 alone does not stimulate Ran GTPase activity or nucleotide exchange, but causes nucleotide release from Ran-GTP and forms a complex with nucleotide-free Ran. However, in combination with Ran-binding protein 1 (RanBP1), XMog1 promotes the release of GDP and the selective binding of GTP to Ran. XMog1 and RanBP1 also promote selective GTP loading onto Ran catalysed by the nuclear guanine nucleotide exchange factor, RCC1. We propose that Mog1-related proteins, together with RanBP1, facilitate the generation of Ran-GTP from Ran-GDP in the nucleus.

scholarly journals A Presenilin-2–ARF4 trafficking axis modulates Notch signaling during epidermal differentiation

2016 ◽  
Vol 214 (1) ◽  
pp. 89-101 ◽  
Author(s):  
Ellen J. Ezratty ◽  
H. Amalia Pasolli ◽  
Elaine Fuchs
Keyword(s):  
Notch Signaling ◽  
Basal Body ◽  
Primary Cilia ◽  
Small Gtpase ◽  
Epidermal Differentiation ◽  
Basal Bodies ◽  
Skin Development ◽  
Epidermal Growth ◽  
Presenilin 2 ◽  
Polarized Exocytosis

How primary cilia impact epidermal growth and differentiation during embryogenesis is poorly understood. Here, we show that during skin development, Notch signaling occurs within the ciliated, differentiating cells of the first few suprabasal epidermal layers. Moreover, both Notch signaling and cilia disappear in the upper layers, where key ciliary proteins distribute to cell–cell borders. Extending this correlation, we find that Presenilin-2 localizes to basal bodies/cilia through a conserved VxPx motif. When this motif is mutated, a GFP-tagged Presenilin-2 still localizes to intercellular borders, but basal body localization is lost. Notably, in contrast to wild type, this mutant fails to rescue epidermal differentiation defects seen upon Psen1 and 2 knockdown. Screening components implicated in ciliary targeting and polarized exocytosis, we provide evidence that the small GTPase ARF4 is required for Presenilin basal body localization, Notch signaling, and subsequent epidermal differentiation. Collectively, our findings raise the possibility that ARF4-dependent polarized exocytosis acts through the basal body–ciliary complex to spatially regulate Notch signaling during epidermal differentiation.

scholarly journals Functional Redundancy of the B9 Proteins and Nephrocystins in Caenorhabditis elegans Ciliogenesis

2008 ◽  
Vol 19 (5) ◽  
pp. 2154-2168 ◽  
Author(s):  
Corey L. Williams ◽  
Marlene E. Winkelbauer ◽  
Jenny C. Schafer ◽  
Edward J. Michaud ◽  
Bradley K. Yoder
Keyword(s):  
Caenorhabditis Elegans ◽  
Joubert Syndrome ◽  
Cystic Kidney ◽  
Basal Bodies ◽  
The Novel ◽  
C Elegans ◽  
Human Genes ◽  
Cilia Formation ◽  
Strong Candidate ◽  
Candidate Loci

Meckel-Gruber syndrome (MKS), nephronophthisis (NPHP), and Joubert syndrome (JBTS) are a group of heterogeneous cystic kidney disorders with partially overlapping loci. Many of the proteins associated with these diseases interact and localize to cilia and/or basal bodies. One of these proteins is MKS1, which is disrupted in some MKS patients and contains a B9 motif of unknown function that is found in two other mammalian proteins, B9D2 and B9D1. Caenorhabditis elegans also has three B9 proteins: XBX-7 (MKS1), TZA-1 (B9D2), and TZA-2 (B9D1). Herein, we report that the C. elegans B9 proteins form a complex that localizes to the base of cilia. Mutations in the B9 genes do not overtly affect cilia formation unless they are in combination with a mutation in nph-1 or nph-4, the homologues of human genes (NPHP1 and NPHP4, respectively) that are mutated in some NPHP patients. Our data indicate that the B9 proteins function redundantly with the nephrocystins to regulate the formation and/or maintenance of cilia and dendrites in the amphid and phasmid ciliated sensory neurons. Together, these data suggest that the human homologues of the novel B9 genes B9D2 and B9D1 will be strong candidate loci for pathologies in human MKS, NPHP, and JBTS.

scholarly journals Protein Kinase A-Mediated Septin7 Phosphorylation Disrupts Septin Filaments and Ciliogenesis

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 361
Author(s):  
Han-Yu Wang ◽  
Chun-Hsiang Lin ◽  
Yi-Ru Shen ◽  
Ting-Yu Chen ◽  
Chia-Yih Wang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Primary Cilia ◽  
Cell Growth And Migration ◽  
Filament Dynamics ◽  
Gtp Binding ◽  
Cilia Formation ◽  
And Migration ◽  
Septin Filament ◽  
Kinase A

Septins are GTP-binding proteins that form heteromeric filaments for proper cell growth and migration. Among the septins, septin7 (SEPT7) is an important component of all septin filaments. Here we show that protein kinase A (PKA) phosphorylates SEPT7 at Thr197, thus disrupting septin filament dynamics and ciliogenesis. The Thr197 residue of SEPT7, a PKA phosphorylating site, was conserved among different species. Treatment with cAMP or overexpression of PKA catalytic subunit (PKACA2) induced SEPT7 phosphorylation, followed by disruption of septin filament formation. Constitutive phosphorylation of SEPT7 at Thr197 reduced SEPT7‒SEPT7 interaction, but did not affect SEPT7‒SEPT6‒SEPT2 or SEPT4 interaction. Moreover, we noted that SEPT7 interacted with PKACA2 via its GTP-binding domain. Furthermore, PKA-mediated SEPT7 phosphorylation disrupted primary cilia formation. Thus, our data uncover the novel biological function of SEPT7 phosphorylation in septin filament polymerization and primary cilia formation.

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