51
|
Zhang Y, Huang Y, Srivathsan A, Lim TK, Lin Q, He CY. The unusual flagellar-targeting mechanism and functions of the trypanosome ortholog of the ciliary GTPase Arl13b. J Cell Sci 2018; 131:jcs.219071. [PMID: 30097558 PMCID: PMC6140319 DOI: 10.1242/jcs.219071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 07/28/2018] [Indexed: 12/11/2022] Open
Abstract
The small GTPase Arl13b is one of the most conserved and ancient ciliary proteins. In human and animals, Arl13b is primarily associated with the ciliary membrane, where it acts as a guanine-nucleotide-exchange factor (GEF) for Arl3 and is implicated in a variety of ciliary and cellular functions. We have identified and characterized Trypanosoma brucei (Tb)Arl13, the sole Arl13b homolog in this evolutionarily divergent, protozoan parasite. TbArl13 has conserved flagellar functions and exhibits catalytic activity towards two different TbArl3 homologs. However, TbArl13 is distinctly associated with the axoneme through a dimerization/docking (D/D) domain. Replacing the D/D domain with a sequence encoding a flagellar membrane protein created a viable alternative to the wild-type TbArl13 in our RNA interference (RNAi)-based rescue assay. Therefore, flagellar enrichment is crucial for TbArl13, but mechanisms to achieve this could be flexible. Our findings thus extend the understanding of the roles of Arl13b and Arl13b–Arl3 pathway in a divergent flagellate of medical importance. This article has an associated First Person interview with the first author of the paper. Highlighted Article: All roads lead to cilia – how the essential flagellar enrichment of Arl13 is achieved in trypanosome cells using a fundamentally different strategy compared with that of animal cells.
Collapse
Affiliation(s)
- Yiliu Zhang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Yameng Huang
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Amrita Srivathsan
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Teck Kwang Lim
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Qingsong Lin
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Cynthia Y He
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| |
Collapse
|
52
|
Dai J, Barbieri F, Mitchell DR, Lechtreck KF. In vivo analysis of outer arm dynein transport reveals cargo-specific intraflagellar transport properties. Mol Biol Cell 2018; 29:2553-2565. [PMID: 30133350 PMCID: PMC6254574 DOI: 10.1091/mbc.e18-05-0291] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Outer dynein arms (ODAs) are multiprotein complexes that drive flagellar beating. Based on genetic and biochemical analyses, ODAs preassemble in the cell body and then move into the flagellum by intraflagellar transport (IFT). To study ODA transport in vivo, we expressed the essential intermediate chain 2 tagged with mNeonGreen (IC2-NG) to rescue the corresponding Chlamydomonas reinhardtii mutant oda6. IC2-NG moved by IFT; the transport was of low processivity and increased in frequency during flagellar growth. As expected, IFT of IC2-NG was diminished in oda16, lacking an ODA-specific IFT adapter, and in ift46 IFT46ΔN lacking the ODA16-interacting portion of IFT46. IFT loading appears to involve ODA16-dependent recruitment of ODAs to basal bodies followed by handover to IFT. Upon unloading from IFT, ODAs rapidly docked to the axoneme. Transient docking still occurred in the docking complex mutant oda3 indicating that the docking complex stabilizes rather than initiates ODA–microtubule interactions. In full-length flagella, ODAs continued to enter and move inside cilia by short-term bidirectional IFT and diffusion and the newly imported complexes frequently replaced axoneme-bound ODAs. We propose that the low processivity of ODA-IFT contributes to flagellar maintenance by ensuring the availability of replacement ODAs along the length of flagella.
Collapse
Affiliation(s)
- Jin Dai
- Department of Cellular Biology, University of Georgia, Athens, GA 30602
| | - Francesco Barbieri
- Department of Cellular Biology, University of Georgia, Athens, GA 30602.,Department of Life Science, University of Siena, 53100 Siena, Italy
| | - David R Mitchell
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210
| | - Karl F Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602
| |
Collapse
|
53
|
Endicott SJ, Brueckner M. NUP98 Sets the Size-Exclusion Diffusion Limit through the Ciliary Base. Curr Biol 2018; 28:1643-1650.e3. [PMID: 29731308 DOI: 10.1016/j.cub.2018.04.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 03/14/2018] [Accepted: 04/04/2018] [Indexed: 12/16/2022]
Abstract
The primary cilium maintains a well-regulated complement of soluble and membrane proteins, allowing it to mediate a variety of signaling pathways that are essential for development and tissue homeostasis [1-3]. Entry into the cilium is regulated at the base, where a complex containing nucleoporins, referred to as the "ciliary pore complex" (CPC), has been proposed to set a size-exclusion limit for soluble molecule diffusion into the cilium [4-6]. Here, using a fluorescence-based diffusion trap system, we demonstrate that NUP98, a component of the phenylalanine-glycine (FG) hydrogel permeability barrier at the nuclear pore complex [7, 8], limits the diffusion of soluble molecules >70 kDa into the cilium in cultured mammalian cells. Small interfering RNA (siRNA)-mediated knockdown of NUP98 increases the rate of diffusion of molecules >100 kDa into the cilium. The tubulin heterodimer, the building block of the axoneme [9, 10], is approximately 100 kDa in size. After knockdown of NUP98, cilia become shorter, and their length is more sensitive to changes in cytoplasmic soluble tubulin levels. These data indicate a novel function of the ciliary pore complex, limiting diffusion of soluble tubulin between the ciliary matrix and the cytosol, allowing the cilium to regulate its length independently of cytosolic microtubule dynamics.
Collapse
Affiliation(s)
- S Joseph Endicott
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Martina Brueckner
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Department of Pediatrics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
| |
Collapse
|
54
|
Hong SR, Wang CL, Huang YS, Chang YC, Chang YC, Pusapati GV, Lin CY, Hsu N, Cheng HC, Chiang YC, Huang WE, Shaner NC, Rohatgi R, Inoue T, Lin YC. Spatiotemporal manipulation of ciliary glutamylation reveals its roles in intraciliary trafficking and Hedgehog signaling. Nat Commun 2018; 9:1732. [PMID: 29712905 PMCID: PMC5928066 DOI: 10.1038/s41467-018-03952-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 03/22/2018] [Indexed: 12/22/2022] Open
Abstract
Tubulin post-translational modifications (PTMs) occur spatiotemporally throughout cells and are suggested to be involved in a wide range of cellular activities. However, the complexity and dynamic distribution of tubulin PTMs within cells have hindered the understanding of their physiological roles in specific subcellular compartments. Here, we develop a method to rapidly deplete tubulin glutamylation inside the primary cilia, a microtubule-based sensory organelle protruding on the cell surface, by targeting an engineered deglutamylase to the cilia in minutes. This rapid deglutamylation quickly leads to altered ciliary functions such as kinesin-2-mediated anterograde intraflagellar transport and Hedgehog signaling, along with no apparent crosstalk to other PTMs such as acetylation and detyrosination. Our study offers a feasible approach to spatiotemporally manipulate tubulin PTMs in living cells. Future expansion of the repertoire of actuators that regulate PTMs may facilitate a comprehensive understanding of how diverse tubulin PTMs encode ciliary as well as cellular functions. Tubulin post-translational modifications (PTMs) occur spatiotemporally throughout cells, therefore assessing the physiological roles in specific subcellular compartments has been challenging. Here the authors develop a method to rapidly deplete tubulin glutamylation inside the primary cilia by targeting an engineered deglutamylase to the axoneme.
Collapse
Affiliation(s)
- Shi-Rong Hong
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Cuei-Ling Wang
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yao-Shen Huang
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yu-Chen Chang
- Department of Life Science, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Ya-Chu Chang
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Ganesh V Pusapati
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, 94305, CA, USA
| | - Chun-Yu Lin
- Department of Medical Science, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Ning Hsu
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Hsiao-Chi Cheng
- Department of Medical Science, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yueh-Chen Chiang
- Interdisciplinary Program of Science, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Wei-En Huang
- Department of Life Science, National Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Nathan C Shaner
- Department of Photobiology and Bioimaging, The Scintillon Institute, San Diego, 92121, CA, USA
| | - Rajat Rohatgi
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, 94305, CA, USA
| | - Takanari Inoue
- Department of Cell Biology, Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, 21205, MD, USA.
| | - Yu-Chun Lin
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, 30013, Taiwan. .,Department of Medical Science, National Tsing Hua University, Hsinchu, 30013, Taiwan.
| |
Collapse
|
55
|
Garcia G, Raleigh DR, Reiter JF. How the Ciliary Membrane Is Organized Inside-Out to Communicate Outside-In. Curr Biol 2018; 28:R421-R434. [PMID: 29689227 PMCID: PMC6434934 DOI: 10.1016/j.cub.2018.03.010] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cilia, organelles that move to execute functions like fertilization and signal to execute functions like photoreception and embryonic patterning, are composed of a core of nine-fold doublet microtubules overlain by a membrane. Distinct types of cilia display distinct membrane morphologies, ranging from simple domed cylinders to the highly ornate invaginations and membrane disks of photoreceptor outer segments. Critical for the ability of cilia to signal, both the protein and the lipid compositions of ciliary membranes are different from those of other cellular membranes. This specialization presents a unique challenge for the cell as, unlike membrane-bounded organelles, the ciliary membrane is contiguous with the surrounding plasma membrane. This distinct ciliary membrane is generated in concert with multiple membrane remodeling events that comprise the process of ciliogenesis. Once the cilium is formed, control of ciliary membrane composition relies on discrete molecular machines, including a barrier to membrane proteins entering the cilium at a specialized region of the base of the cilium called the transition zone and a trafficking adaptor that controls G protein-coupled receptor (GPCR) localization to the cilium called the BBSome. The ciliary membrane can be further remodeled by the removal of membrane proteins by the release of ciliary extracellular vesicles that may function in intercellular communication, removal of unneeded proteins or ciliary disassembly. Here, we review the structures and transport mechanisms that control ciliary membrane composition, and discuss how membrane specialization enables the cilium to function as the antenna of the cell.
Collapse
Affiliation(s)
- Galo Garcia
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA
| | - David R Raleigh
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Radiation Oncology, University of California, San Francisco, CA 94143, USA; Department of Neurological Surgery, University of California, San Francisco, CA 94143, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA.
| |
Collapse
|
56
|
Eguether T, Cordelieres FP, Pazour GJ. Intraflagellar transport is deeply integrated in hedgehog signaling. Mol Biol Cell 2018. [PMID: 29540531 PMCID: PMC5935068 DOI: 10.1091/mbc.e17-10-0600] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The vertebrate hedgehog pathway is organized in primary cilia, and hedgehog components relocate into or out of cilia during signaling. Defects in intraflagellar transport (IFT) typically disrupt ciliary assembly and attenuate hedgehog signaling. Determining whether IFT drives the movement of hedgehog components is difficult due to the requirement of IFT for building cilia. Unlike most IFT proteins, IFT27 is dispensable for cilia formation but affects hedgehog signaling similarly to other IFTs, allowing us to examine its role in the dynamics of signaling. Activating signaling at points along the pathway in Ift27 mutant cells showed that IFT is extensively involved in the pathway. Similar analysis of Bbs mutant cells showed that BBS proteins participate at many levels of signaling but are not needed to concentrate Gli transcription factors at the ciliary tip. Our analysis showed that smoothened delivery to cilia does not require IFT27, but the role of other IFTs is not known. Using a rapamycin-induced dimerization system to sequester IFT-B proteins at the mitochondria in cells with fully formed cilia did not affect the delivery of Smo to cilia, suggesting that this membrane protein may not require IFT-B for delivery.
Collapse
Affiliation(s)
- Thibaut Eguether
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605
| | - Fabrice P Cordelieres
- Université de Bordeaux, UMS 3420 CNRS-Université de Bordeaux-US4 INSERM, Bordeaux Imaging Center, F-33000 Bordeaux, France
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605
| |
Collapse
|
57
|
Lu L, Madugula V. Mechanisms of ciliary targeting: entering importins and Rabs. Cell Mol Life Sci 2018; 75:597-606. [PMID: 28852774 PMCID: PMC11105572 DOI: 10.1007/s00018-017-2629-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 08/11/2017] [Accepted: 08/16/2017] [Indexed: 12/29/2022]
Abstract
Primary cilium is a rod-like plasma membrane protrusion that plays important roles in sensing the cellular environment and initiating corresponding signaling pathways. The sensory functions of the cilium critically depend on the unique enrichment of ciliary residents, which is maintained by the ciliary diffusion barrier. It is still unclear how ciliary cargoes specifically enter the diffusion barrier and accumulate within the cilium. In this review, the organization and trafficking mechanism of the cilium are compared to those of the nucleus, which are much better understood at the moment. Though the cilium differs significantly from the nucleus in terms of molecular and cellular functions, analogous themes and principles in the membrane organization and cargo trafficking are notable between them. Therefore, knowledge in the nuclear trafficking can likely shed light on our understanding of the ciliary trafficking. Here, with a focus on membrane cargoes in mammalian cells, we briefly review various ciliary trafficking pathways from the Golgi to the periciliary membrane. Models for the subsequent import translocation across the diffusion barrier and the enrichment of cargoes within the ciliary membrane are discussed in detail. Based on recent discoveries, we propose a Rab-importin-based model in an attempt to accommodate various observations on ciliary targeting.
Collapse
Affiliation(s)
- Lei Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
| | - Viswanadh Madugula
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| |
Collapse
|
58
|
The Axon Initial Segment: An Updated Viewpoint. J Neurosci 2018; 38:2135-2145. [PMID: 29378864 DOI: 10.1523/jneurosci.1922-17.2018] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 01/20/2018] [Accepted: 01/25/2018] [Indexed: 12/20/2022] Open
Abstract
At the base of axons sits a unique compartment called the axon initial segment (AIS). The AIS generates and shapes the action potential before it is propagated along the axon. Neuronal excitability thus depends crucially on the AIS composition and position, and these adapt to developmental and physiological conditions. The AIS also demarcates the boundary between the somatodendritic and axonal compartments. Recent studies have brought insights into the molecular architecture of the AIS and how it regulates protein trafficking. This Viewpoints article summarizes current knowledge about the AIS and highlights future challenges in understanding this key actor of neuronal physiology.
Collapse
|
59
|
Nakamura H, Lee AA, Afshar AS, Watanabe S, Rho E, Razavi S, Suarez A, Lin YC, Tanigawa M, Huang B, DeRose R, Bobb D, Hong W, Gabelli SB, Goutsias J, Inoue T. Intracellular production of hydrogels and synthetic RNA granules by multivalent molecular interactions. NATURE MATERIALS 2018; 17:79-89. [PMID: 29115293 PMCID: PMC5916848 DOI: 10.1038/nmat5006] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 09/08/2017] [Indexed: 05/06/2023]
Abstract
Some protein components of intracellular non-membrane-bound entities, such as RNA granules, are known to form hydrogels in vitro. The physico-chemical properties and functional role of these intracellular hydrogels are difficult to study, primarily due to technical challenges in probing these materials in situ. Here, we present iPOLYMER, a strategy for a rapid induction of protein-based hydrogels inside living cells that explores the chemically inducible dimerization paradigm. Biochemical and biophysical characterizations aided by computational modelling show that the polymer network formed in the cytosol resembles a physiological hydrogel-like entity that acts as a size-dependent molecular sieve. We functionalize these polymers with RNA-binding motifs that sequester polyadenine-containing nucleotides to synthetically mimic RNA granules. These results show that iPOLYMER can be used to synthetically reconstitute the nucleation of biologically functional entities, including RNA granules in intact cells.
Collapse
Affiliation(s)
- Hideki Nakamura
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Albert A. Lee
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Ali Sobhi Afshar
- Center for Imaging Science, Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, MD, 21218
- To whom correspondence regarding the computational analysis should be addressed: (A.S.A)
| | - Shigeki Watanabe
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
| | - Elmer Rho
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Shiva Razavi
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Department of Biomedical Engineering, Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, MD 21218
| | - Allison Suarez
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Yu-Chun Lin
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Makoto Tanigawa
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Department of Biomedical Engineering, Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, MD 21218
| | - Brian Huang
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Robert DeRose
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - Diana Bobb
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
| | - William Hong
- Department of Biophysics and Biophysical Chemistry, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
| | - Sandra B. Gabelli
- Department of Biophysics and Biophysical Chemistry, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD, 21205
- Department of Oncology, School of Medicine, Johns Hopkins University, Baltimore, MD, 21205
| | - John Goutsias
- Center for Imaging Science, Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, MD, 21218
| | - Takanari Inoue
- Department of Cell Biology, School of Medicine, The Johns Hopkins University, Baltimore, MD, 21205
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, The Johns Hopkins University, Baltimore, MD, 21205
- Department of Biomedical Engineering, Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, MD 21218
- To whom general correspondence should be addressed: (T.I.)
| |
Collapse
|
60
|
Stephen LA, Elmaghloob Y, Ismail S. Maintaining protein composition in cilia. Biol Chem 2017; 399:1-11. [PMID: 28850540 DOI: 10.1515/hsz-2017-0168] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/18/2017] [Indexed: 01/10/2023]
Abstract
The primary cilium is a sensory organelle that is vital in regulating several signalling pathways. Unlike most organelles cilia are open to the rest of the cell, not enclosed by membranes. The distinct protein composition is crucial to the function of cilia and many signalling proteins and receptors are specifically concentrated within distinct compartments. To maintain this composition, a mechanism is required to deliver proteins to the cilium whilst another must counter the entropic tendency of proteins to distribute throughout the cell. The combination of the two mechanisms should result in the concentration of ciliary proteins to the cilium. In this review we will look at different cellular mechanisms that play a role in maintaining the distinct composition of cilia, including regulation of ciliary access and trafficking of ciliary proteins to, from and within the cilium.
Collapse
Affiliation(s)
- Louise A Stephen
- CR-UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Yasmin Elmaghloob
- CR-UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Shehab Ismail
- CR-UK Beatson Institute, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| |
Collapse
|
61
|
Seo S, Datta P. Photoreceptor outer segment as a sink for membrane proteins: hypothesis and implications in retinal ciliopathies. Hum Mol Genet 2017; 26:R75-R82. [PMID: 28453661 DOI: 10.1093/hmg/ddx163] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 04/24/2017] [Indexed: 12/28/2022] Open
Abstract
The photoreceptor outer segment (OS) is a unique modification of the primary cilium, specialized for light perception. Being homologous organelles, the primary cilium and the OS share common building blocks and molecular machinery to construct and maintain them. The OS, however, has several unique structural features that are not seen in primary cilia. Although these unique features of the OS have been well documented, their implications in protein localization have been under-appreciated. In this review, we compare the structural properties of the primary cilium and the OS, and propose a hypothesis that the OS can act as a sink for membrane proteins. We further discuss the implications of this hypothesis in polarized protein localization in photoreceptors and mechanisms of photoreceptor degeneration in retinal ciliopathies.
Collapse
Affiliation(s)
- Seongjin Seo
- Department of Ophthalmology and Visual Sciences, Wynn Institute for Vision Research, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Poppy Datta
- Department of Ophthalmology and Visual Sciences, Wynn Institute for Vision Research, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| |
Collapse
|
62
|
Fan CH, Huang YS, Huang WE, Lee AA, Ho SY, Kao YL, Wang CL, Lian YL, Ueno T, Andrew Wang TS, Yeh CK, Lin YC. Manipulating Cellular Activities Using an Ultrasound-Chemical Hybrid Tool. ACS Synth Biol 2017; 6:2021-2027. [PMID: 28945972 DOI: 10.1021/acssynbio.7b00162] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We developed an ultrasound-chemical hybrid tool to precisely manipulate cellular activities. A focused ultrasound coupled with gas-filled microbubbles was used to rapidly trigger the influx of membrane-impermeable chemical dimerizers into living cells to regulate protein dimerization and location without inducing noticeable toxicity. With this system, we demonstrated the successful modulation of phospholipid metabolism triggered by a short pulse of ultrasound exposure. Our technique offers a powerful and versatile tool for using ultrasound to spatiotemporally manipulate the cellular physiology in living cells.
Collapse
Affiliation(s)
| | | | | | | | - Sheng-Yang Ho
- Department
of Chemistry, National Taiwan University, Taipei, 10617, Taiwan
| | | | | | | | - Tasuku Ueno
- Graduate
School of Pharmaceutical Sciences, University of Tokyo, Tokyo, 113-8654, Japan
| | | | | | | |
Collapse
|
63
|
Nag S, Resnick A. Biophysics and biofluid dynamics of primary cilia: evidence for and against the flow-sensing function. Am J Physiol Renal Physiol 2017. [DOI: 10.1152/ajprenal.00172.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Primary cilia have been called “the forgotten organelle” for over 20 yr. As cilia now have their own journal and several books devoted to their study, perhaps it is time to reconsider the moniker “forgotten organelle.” In fact, during the drafting of this review, 12 relevant publications have been issued; we therefore apologize in advance for any relevant work we inadvertently omitted. What purpose is yet another ciliary review? The primary goal of this review is to specifically examine the evidence for and against the hypothesized flow-sensing function of primary cilia expressed by differentiated epithelia within a kidney tubule, bringing together differing disciplines and their respective conceptual and experimental approaches. We will show that understanding the biophysics/biomechanics of primary cilia provides essential information for understanding any potential role of ciliary function in disease. We will summarize experimental and mathematical models used to characterize renal fluid flow and incident force on primary cilia and to characterize the mechanical response of cilia to an externally applied force and discuss possible ciliary-mediated cell signaling pathways triggered by flow. Throughout, we stress the importance of separating the effects of fluid shear and stretch from the action of hydrodynamic drag.
Collapse
Affiliation(s)
- Subhra Nag
- Department of Biology, Geology, and Environmental Sciences, Cleveland State University, Cleveland, Ohio
| | - Andrew Resnick
- Department of Biology, Geology, and Environmental Sciences, Cleveland State University, Cleveland, Ohio
- Department of Physics, Cleveland State University, Cleveland, Ohio; and
- Center for Gene Regulation in Health and Disease, Cleveland State University, Cleveland, Ohio
| |
Collapse
|
64
|
Han Y, Xiong Y, Shi X, Wu J, Zhao Y, Jiang J. Regulation of Gli ciliary localization and Hedgehog signaling by the PY-NLS/karyopherin-β2 nuclear import system. PLoS Biol 2017; 15:e2002063. [PMID: 28777795 PMCID: PMC5544186 DOI: 10.1371/journal.pbio.2002063] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 07/07/2017] [Indexed: 12/21/2022] Open
Abstract
Hedgehog (Hh) signaling in vertebrates depends on primary cilia. Upon stimulation, Hh pathway components, including Gli transcription factors, accumulate at primary cilia to transduce the Hh signal, but the mechanisms underlying their ciliary targeting remains largely unknown. Here, we show that the PY-type nuclear localization signal (PY-NLS)/karyopherinβ2 (Kapβ2) nuclear import system regulates Gli ciliary localization and Hh pathway activation. Mutating the PY-NLS in Gli or knockdown of Kapβ2 diminished Gli ciliary localization. Kapβ2 is required for the formation of Gli activator (GliA) in wild-type but not in Sufu mutant cells. Knockdown of Kapβ2 affected Hh signaling in zebrafish embryos, as well as in vitro cultured cerebellum granule neuron progenitors (CGNPs) and SmoM2-driven medulloblastoma cells. Furthermore, Kapβ2 depletion impaired the growth of cultured medulloblastoma cells, which was rescued by Gli overexpression. Interestingly, Kapβ2 is a transcriptional target of the Hh pathway, thus forming a positive feedback loop for Gli activation. Our study unravels the molecular mechanism and cellular machinery regulating Gli ciliary localization and identifies Kapβ2 as a critical regulator of the Hh pathway and a potential drug target for Hh-driven cancers. The secreted Hedgehog (Hh) protein plays an evolutionarily conserved role in both embryonic development and adult tissue homeostasis. Malfunction of Hh signaling activity contributes to a wide range of human diseases, including birth defects and cancer. Hh signaling in vertebrates critically depends on the primary cilium, a microtubule-based plasma membrane protrusion present on the surface of most mammalian cells. Upon ligand stimulation, Hh pathway components, including the seven-transmembrane protein Smoothened (Smo) and Gli transcription factors, accumulate at primary cilia to transduce the Hh signal, but the mechanisms underlying their ciliary targeting are still poorly understood. Here, we discover that the PY-type nuclear localization signal (PY-NLS) and the nuclear import factor karyopherinβ2 (Kapβ2) regulate Gli ciliary localization and Hh pathway activity. Mutating the PY-NLS in Gli or knockdown of Kapβ2 diminished Gli ciliary localization without affecting Smo ciliary accumulation in response to Hh. Kapβ2 regulates the formation of the active form of Gli, which is required for proper Hh signaling in zebrafish embryos and cultured cerebellum granule neuron progenitors (CGNPs). Kapβ2 depletion impaired the growth of medulloblastoma cells driven by an oncogenic form of Smo. Finally, Kapβ2 is a transcriptional target of the Hh pathway, forming a positive feedback loop to promote Gli activation. Our study reveals the molecular mechanism underlying the regulation of Gli ciliary targeting and identifies Kapβ2 as a potential cancer drug target.
Collapse
Affiliation(s)
- Yuhong Han
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Yue Xiong
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Institute of Biochemistry and Cell Biology, Shanghai Institute of Life Sciences, CAS, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xuanming Shi
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Jiang Wu
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Yun Zhao
- State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Institute of Biochemistry and Cell Biology, Shanghai Institute of Life Sciences, CAS, School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- * E-mail: (JJ); (YZ)
| | - Jin Jiang
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- * E-mail: (JJ); (YZ)
| |
Collapse
|
65
|
Abstract
Motile and non-motile (primary) cilia are nearly ubiquitous cellular organelles. The dysfunction of cilia causes diseases known as ciliopathies. The number of reported ciliopathies (currently 35) is increasing, as is the number of established (187) and candidate (241) ciliopathy-associated genes. The characterization of ciliopathy-associated proteins and phenotypes has improved our knowledge of ciliary functions. In particular, investigating ciliopathies has helped us to understand the molecular mechanisms by which the cilium-associated basal body functions in early ciliogenesis, as well as how the transition zone functions in ciliary gating, and how intraflagellar transport enables cargo trafficking and signalling. Both basic biological and clinical studies are uncovering novel ciliopathies and the ciliary proteins involved. The assignment of these proteins to different ciliary structures, processes and ciliopathy subclasses (first order and second order) provides insights into how this versatile organelle is built, compartmentalized and functions in diverse ways that are essential for human health.
Collapse
|
66
|
Hou Y, Witman GB. The N-terminus of IFT46 mediates intraflagellar transport of outer arm dynein and its cargo-adaptor ODA16. Mol Biol Cell 2017; 28:2420-2433. [PMID: 28701346 PMCID: PMC5576905 DOI: 10.1091/mbc.e17-03-0172] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 06/30/2017] [Accepted: 07/05/2017] [Indexed: 01/23/2023] Open
Abstract
A transposon event, resulting in partial suppression of a Chlamydomonas IFT46 null mutant, allowed the function of the N-terminus of IFT46 in flagellar assembly to be explored. The IFT46 N-terminus is not required for IFT complex assembly but is required for transport of outer arm dynein and its adaptor, ODA16, into the flagellum. Cilia are assembled via intraflagellar transport (IFT). The IFT machinery is composed of motors and multisubunit particles, termed IFT-A and IFT-B, that carry cargo into the cilium. Knowledge of how the IFT subunits interact with their cargo is of critical importance for understanding how the unique ciliary domain is established. We previously reported a Chlamydomonas mutant, ift46-1, that fails to express the IFT-B protein IFT46, has greatly reduced levels of other IFT-B proteins, and assembles only very short flagella. A spontaneous suppression of ift46-1 restored IFT-B levels and enabled growth of longer flagella, but the flagella lacked outer dynein arms. Here we show that the suppression is due to insertion of the transposon MRC1 into the ift46-1 allele, causing the expression of a fusion protein including the IFT46 C-terminal 240 amino acids. The IFT46 C-terminus can assemble into and stabilize IFT-B but does not support transport of outer arm dynein into flagella. ODA16, a cargo adaptor specific for outer arm dynein, also fails to be imported into the flagella in the absence of the IFT46 N-terminus. We conclude that the IFT46 N-terminus, ODA16, and outer arm dynein interact for IFT of the latter.
Collapse
Affiliation(s)
- Yuqing Hou
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA 01655
| | - George B Witman
- Division of Cell Biology and Imaging, Department of Radiology, University of Massachusetts Medical School, Worcester, MA 01655
| |
Collapse
|
67
|
Takao D, Kamimura S. Simulation of intra-ciliary diffusion suggests a novel role of primary cilia as a cell-signaling enhancer. Dev Growth Differ 2017; 59:415-422. [PMID: 28573753 DOI: 10.1111/dgd.12360] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 12/16/2022]
Abstract
Besides the role to generate a fluid flow in the surrounding medium, eukaryotic cilia have a crucial function in sensing external signals such as chemical or mechanical stimuli. A large body of work has shown that cilia are frequently found in various types of sensory cells and are closely related to many regulatory mechanisms in differentiation and development. However, we do not yet have a definitive answer to the fundamental question, "why cilia?" It has been a long-standing mystery why cells use cilia for sensing external signals. To shed light on this, we sought to describe the kinetics of signaling with theoretical approaches. Based on the results, here we propose a new role of cilia as a cell-signaling enhancer. The enhancing effect comes from restricted volume for the free intra-ciliary diffusion of molecules due to the cylindrical shape of cilia, which can facilitate quick accumulation of intracellular signaling molecules. Our simulations demonstrate that both the rate and amplitude of response in signal transduction depend on where the membrane receptors or channels are located along the ciliary shaft. In addition, the calculated transfer function of cilia regarded as a transmitter of external signals also suggests the properties of cilia as a signal enhancer. Since such unique composition of receptors and channels in cilia is found in various types of eukaryotic cells, signal enhancing is presumably one of the most essential and conserved roles of cilia.
Collapse
Affiliation(s)
- Daisuke Takao
- Department of Molecular Genetics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
| | - Shinji Kamimura
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
| |
Collapse
|
68
|
Jensen VL, Leroux MR. Gates for soluble and membrane proteins, and two trafficking systems (IFT and LIFT), establish a dynamic ciliary signaling compartment. Curr Opin Cell Biol 2017; 47:83-91. [PMID: 28432921 DOI: 10.1016/j.ceb.2017.03.012] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/18/2017] [Accepted: 03/21/2017] [Indexed: 12/28/2022]
Abstract
Primary cilia are microtubule-based organelles found on most mammalian cell surfaces. They possess a soluble matrix and membrane contiguous with the cell body cytosol and plasma membrane, and yet, have distinct compositions that can be modulated to enable dynamic signal transduction. Here, we discuss how specialized ciliary compartments are established using a coordinated network of gating, trafficking and targeting activities. Cilium homeostasis is maintained by a size-selective molecular mesh that limits soluble protein entry, and by a membrane diffusion barrier localized at the transition zone. Bidirectional protein shuttling between the cell body and cilium uses IntraFlagellar Transport (IFT), and prenylated ciliary protein delivery is achieved through Lipidated protein IntraFlagellar Targeting (LIFT). Elucidating how these gates and transport systems function will help reveal the roles that cilia play in ciliary signaling and the growing spectrum of disorders termed ciliopathies.
Collapse
Affiliation(s)
- Victor L Jensen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada; Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, Canada
| | - Michel R Leroux
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada; Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, Canada.
| |
Collapse
|
69
|
Ishikawa H, Marshall WF. Intraflagellar Transport and Ciliary Dynamics. Cold Spring Harb Perspect Biol 2017; 9:9/3/a021998. [PMID: 28249960 DOI: 10.1101/cshperspect.a021998] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cilia and flagella are microtubule-based organelles whose assembly requires a motile process, known as intraflagellar transport (IFT), to bring tubulin and other components to the distal tip of the growing structure. The IFT system uses a multiprotein complex with components that appear to be specialized for the transport of different sets of cargo proteins. The mechanisms by which cargo is selected for ciliary import and transport by IFT remain an area of active research. The complex dynamics of cilia and flagella are under constant regulation to ensure proper length control, and this regulation appears to involve regulation at the stage of IFT injection into the flagellum, as well as regulation of flagellar disassembly and, possibly, of cargo binding. Cilia and flagella thus represent a convenient model system to study how multiple motile and signaling pathways cooperate to control the assembly and dynamics of a complex cellular structure.
Collapse
Affiliation(s)
- Hiroaki Ishikawa
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94158
| | - Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94158
| |
Collapse
|
70
|
Badgandi HB, Hwang SH, Shimada IS, Loriot E, Mukhopadhyay S. Tubby family proteins are adapters for ciliary trafficking of integral membrane proteins. J Cell Biol 2017; 216:743-760. [PMID: 28154160 PMCID: PMC5350516 DOI: 10.1083/jcb.201607095] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 11/25/2016] [Accepted: 01/09/2017] [Indexed: 01/19/2023] Open
Abstract
Trafficking of integral membrane proteins to cilia is poorly understood. Badgandi et al. show that tubby family proteins TULP3 and TUB act as general adapters for ciliary trafficking of structurally diverse integral membrane cargo like GCPRs and the polycystin 1/2 complex. The primary cilium is a paradigmatic organelle for studying compartmentalized signaling; however, unlike soluble protein trafficking, processes targeting integral membrane proteins to cilia are poorly understood. In this study, we determine that the tubby family protein TULP3 functions as a general adapter for ciliary trafficking of structurally diverse integral membrane cargo, including multiple reported and novel rhodopsin family G protein–coupled receptors (GPCRs) and the polycystic kidney disease–causing polycystin 1/2 complex. The founding tubby family member TUB also localizes to cilia similar to TULP3 and determines trafficking of a subset of these GPCRs to neuronal cilia. Using minimal ciliary localization sequences from GPCRs and fibrocystin (also implicated in polycystic kidney disease), we demonstrate these motifs to be sufficient and TULP3 dependent for ciliary trafficking. We propose a three-step model for TULP3/TUB-mediated ciliary trafficking, including the capture of diverse membrane cargo by the tubby domain in a phosphoinositide 4,5-bisphosphate (PI(4,5)P2)-dependent manner, ciliary delivery by intraflagellar transport complex A binding to the TULP3/TUB N terminus, and subsequent release into PI(4,5)P2-deficient ciliary membrane.
Collapse
Affiliation(s)
- Hemant B Badgandi
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Sun-Hee Hwang
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Issei S Shimada
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Evan Loriot
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390.,STARS Program, University of Texas Southwestern Medical Center, Dallas, TX 75390.,Jesuit College Preparatory School of Dallas, Dallas, TX 75244
| | - Saikat Mukhopadhyay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| |
Collapse
|
71
|
He M, Agbu S, Anderson KV. Microtubule Motors Drive Hedgehog Signaling in Primary Cilia. Trends Cell Biol 2017; 27:110-125. [PMID: 27765513 PMCID: PMC5258846 DOI: 10.1016/j.tcb.2016.09.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 09/08/2016] [Accepted: 09/23/2016] [Indexed: 01/05/2023]
Abstract
The mammalian Hedgehog (Hh) signaling pathway is required for development and for maintenance of adult stem cells, and overactivation of the pathway can cause tumorigenesis. All responses to Hh family ligands in mammals require the primary cilium, an ancient microtubule-based organelle that extends from the cell surface. Genetic studies in mice and humans have defined specific functions for cilium-associated microtubule motor proteins: they act in the construction and disassembly of the primary cilium, they control ciliary length and stability, and some have direct roles in mammalian Hh signal transduction. These studies highlight how integrated genetic and cell biological studies can define the molecular mechanisms that underlie cilium-associated health and disease.
Collapse
Affiliation(s)
- Mu He
- Department of Physiology and Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Stephanie Agbu
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; Biochemistry, Cell, and Molecular Biology Program, Weill Graduate School of Medical Sciences of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Kathryn V Anderson
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| |
Collapse
|
72
|
Garcia-Gonzalo FR, Reiter JF. Open Sesame: How Transition Fibers and the Transition Zone Control Ciliary Composition. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a028134. [PMID: 27770015 DOI: 10.1101/cshperspect.a028134] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cilia are plasma membrane protrusions that act as cellular propellers or antennae. To perform these functions, cilia must maintain a composition distinct from those of the contiguous cytosol and plasma membrane. The specialized composition of the cilium depends on the ciliary gate, the region at the ciliary base separating the cilium from the rest of the cell. The ciliary gate's main structural features are electron dense struts connecting microtubules to the adjacent membrane. These structures include the transition fibers, which connect the distal basal body to the base of the ciliary membrane, and the Y-links, which connect the proximal axoneme and ciliary membrane within the transition zone. Both transition fibers and Y-links form early during ciliogenesis and play key roles in ciliary assembly and trafficking. Accordingly, many human ciliopathies are caused by mutations that perturb ciliary gate function.
Collapse
Affiliation(s)
- Francesc R Garcia-Gonzalo
- Departamento de Bioquímica, Facultad de Medicina, and Instituto de Investigaciones Biomédicas Alberto Sols UAM-CSIC, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94158
| |
Collapse
|
73
|
Phua SC, Chiba S, Suzuki M, Su E, Roberson EC, Pusapati GV, Schurmans S, Setou M, Rohatgi R, Reiter JF, Ikegami K, Inoue T. Dynamic Remodeling of Membrane Composition Drives Cell Cycle through Primary Cilia Excision. Cell 2017; 168:264-279.e15. [PMID: 28086093 DOI: 10.1016/j.cell.2016.12.032] [Citation(s) in RCA: 229] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 10/27/2016] [Accepted: 12/21/2016] [Indexed: 12/16/2022]
Abstract
The life cycle of a primary cilium begins in quiescence and ends prior to mitosis. In quiescent cells, the primary cilium insulates itself from contiguous dynamic membrane processes on the cell surface to function as a stable signaling apparatus. Here, we demonstrate that basal restriction of ciliary structure dynamics is established by the cilia-enriched phosphoinositide 5-phosphatase, Inpp5e. Growth induction displaces ciliary Inpp5e and accumulates phosphatidylinositol 4,5-bisphosphate in distal cilia. This change triggers otherwise-forbidden actin polymerization in primary cilia, which excises cilia tips in a process we call cilia decapitation. While cilia disassembly is traditionally thought to occur solely through resorption, we show that an acute loss of IFT-B through cilia decapitation precedes resorption. Finally, we propose that cilia decapitation induces mitogenic signaling and constitutes a molecular link between the cilia life cycle and cell-division cycle. This newly defined ciliary mechanism may find significance in cell proliferation control during normal development and cancer.
Collapse
Affiliation(s)
- Siew Cheng Phua
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Shuhei Chiba
- Laboratory of Biological Science, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Masako Suzuki
- Advanced Research Facilities and Services, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Emily Su
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Elle C Roberson
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ganesh V Pusapati
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | | | - Mitsutoshi Setou
- Department of Cellular and Molecular Anatomy and International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Rajat Rohatgi
- Departments of Medicine and Biochemistry, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Koji Ikegami
- Department of Cellular and Molecular Anatomy and International Mass Imaging Center, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan.
| | - Takanari Inoue
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| |
Collapse
|
74
|
Abstract
Although solitary or sensory cilia are present in most cells of the body and their existence has been known since the sixties, very little is known about their functions. One suspected function is fluid flow sensing- physical bending of cilia produces an influx of Ca++, which can then result in a variety of activated signaling pathways. Defective cilia and ciliary-associated proteins have been shown to result in cystic diseases. Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a progressive disease, typically appearing in the 5th decade of life and is one of the most common monogenetic inherited human diseases, affecting approximately 600,000 people in the United States. Because the mechanical properties of cilia impact their response to applied flow, we asked how the stiffness of cilia can be controlled pharmacologically. We performed an experiment subjecting cilia to Taxol (a microtubule stabilizer) and CoCl2 (a HIF stabilizer to model hypoxia). Madin-Darby Canine Kidney (MDCK) cells were selected as our model system. After incubation with a selected pharmacological agent, cilia were optically trapped and the bending modulus measured. We found that HIF stabilization significantly weakens cilia. These results illustrate a method to alter the mechanical properties of primary cilia and potentially alter the flow sensing properties of cilia.
Collapse
Affiliation(s)
- Andrew Resnick
- Department of Physics, Cleveland State University, Cleveland, Ohio, United States of America.,Center for Gene Regulation in Health and Disease, Cleveland State University, Cleveland, Ohio, United States of America
| |
Collapse
|
75
|
Qiu L, LeBel RP, Storm DR, Chen X. Type 3 adenylyl cyclase: a key enzyme mediating the cAMP signaling in neuronal cilia. INTERNATIONAL JOURNAL OF PHYSIOLOGY, PATHOPHYSIOLOGY AND PHARMACOLOGY 2016; 8:95-108. [PMID: 27785336 PMCID: PMC5078481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Accepted: 09/06/2016] [Indexed: 06/06/2023]
Abstract
Cilia are rigid, centriole-derived, microtubule-based organelles present in a majority of vertebrate cells including neurons. They are considered the cellular "antennae" attuned for detecting a range of extracellular signals including photons, odorants, morphogens, hormones and mechanical forces. The ciliary microenvironment is distinct from most actin-based subcellular structures such as microvilli or synapses. In the nervous system, there is no evidence that neuronal cilia process any synaptic structure. Apparently, the structural features of neuronal cilia do not allow them to harbor any synaptic connections. Nevertheless, a large number of G protein-coupled receptors (GPCRs) including odorant receptors, rhodopsin, Smoothened, and type 6 serotonin receptor are found in cilia, suggesting that these tiny processes largely depend on metabotropic receptors and their tuned signals to impact neuronal functions. The type 3 adenylyl cyclase (AC3), widely known as a cilia marker, is highly and predominantly expressed in olfactory sensory cilia and primary cilia throughout the brain. We discovered that ablation of AC3 in mice leads to pleiotropic phenotypes including anosmia, failure to detect mechanical stimulation of airflow, cognitive deficit, obesity, and depression-like behaviors. Multiple lines of human genetic evidence also demonstrate that AC3 is associated with obesity, major depressive disorder (MDD), sarcoidosis, and infertility, underscoring its functional importance. Here we review recent progress on AC3, a key enzyme mediating the cAMP signaling in neuronal cilia.
Collapse
Affiliation(s)
- Liyan Qiu
- Department of Molecular, Cellular, and Biomedical Sciences, College of Life Science and Agriculture, University of New HampshireDurham, NH 03824, USA
| | - Robert P LeBel
- Department of Molecular, Cellular, and Biomedical Sciences, College of Life Science and Agriculture, University of New HampshireDurham, NH 03824, USA
| | - Daniel R Storm
- Department of Pharmacology, School of Medicine, University of WashingtonSeattle, WA, 98195-7750, USA
| | - Xuanmao Chen
- Department of Molecular, Cellular, and Biomedical Sciences, College of Life Science and Agriculture, University of New HampshireDurham, NH 03824, USA
| |
Collapse
|
76
|
Del Viso F, Huang F, Myers J, Chalfant M, Zhang Y, Reza N, Bewersdorf J, Lusk CP, Khokha MK. Congenital Heart Disease Genetics Uncovers Context-Dependent Organization and Function of Nucleoporins at Cilia. Dev Cell 2016; 38:478-92. [PMID: 27593162 PMCID: PMC5021619 DOI: 10.1016/j.devcel.2016.08.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 07/07/2016] [Accepted: 08/08/2016] [Indexed: 01/21/2023]
Abstract
Human genomics is identifying candidate genes for congenital heart disease (CHD), but discovering the underlying mechanisms remains challenging. In a patient with CHD and heterotaxy (Htx), a disorder of left-right patterning, we previously identified a duplication in Nup188. However, a mechanism to explain how a component of the nuclear pore complex (NPC) could cause Htx/CHD was undefined. Here, we show that knockdown of Nup188 or its binding partner Nup93 leads to a loss of cilia during embryonic development while leaving NPC function largely intact. Many data, including the localization of endogenous Nup188/93 at cilia bases, support their direct role at cilia. Super-resolution imaging of Nup188 shows two barrel-like structures with dimensions and organization incompatible with an NPC-like ring, arguing against a proposed "ciliary pore complex." We suggest that the nanoscale organization and function of nucleoporins are context dependent in a way that is required for the structure of the heart.
Collapse
Affiliation(s)
- Florencia Del Viso
- Program in Vertebrate Developmental Biology, Departments of Pediatrics and Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Fang Huang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Weldon School of Biomedical Engineering, College of Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Jordan Myers
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Madeleine Chalfant
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Yongdeng Zhang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Nooreen Reza
- Program in Vertebrate Developmental Biology, Departments of Pediatrics and Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - C Patrick Lusk
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
| | - Mustafa K Khokha
- Program in Vertebrate Developmental Biology, Departments of Pediatrics and Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
| |
Collapse
|
77
|
Wei Q, Zhang Y, Schouteden C, Zhang Y, Zhang Q, Dong J, Wonesch V, Ling K, Dammermann A, Hu J. The hydrolethalus syndrome protein HYLS-1 regulates formation of the ciliary gate. Nat Commun 2016; 7:12437. [PMID: 27534274 PMCID: PMC4992140 DOI: 10.1038/ncomms12437] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 06/30/2016] [Indexed: 12/18/2022] Open
Abstract
Transition fibres (TFs), together with the transition zone (TZ), are basal ciliary structures thought to be crucial for cilium biogenesis and function by acting as a ciliary gate to regulate selective protein entry and exit. Here we demonstrate that the centriolar and basal body protein HYLS-1, the C. elegans orthologue of hydrolethalus syndrome protein 1, is required for TF formation, TZ organization and ciliary gating. Loss of HYLS-1 compromises the docking and entry of intraflagellar transport (IFT) particles, ciliary gating for both membrane and soluble proteins, and axoneme assembly. Additional depletion of the TF component DYF-19 in hyls-1 mutants further exacerbates TZ anomalies and completely abrogates ciliogenesis. Our data support an important role for HYLS-1 and TFs in establishment of the ciliary gate and underline the importance of selective protein entry for cilia assembly.
Collapse
Affiliation(s)
- Qing Wei
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.,Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yingyi Zhang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Clementine Schouteden
- Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, A-1030 Vienna, Austria
| | - Yuxia Zhang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Qing Zhang
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Jinhong Dong
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Veronika Wonesch
- Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, A-1030 Vienna, Austria
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Alexander Dammermann
- Max F. Perutz Laboratories, Vienna Biocenter (VBC), University of Vienna, A-1030 Vienna, Austria
| | - Jinghua Hu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.,Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota 55905, USA.,Mayo Translational PKD Center, Mayo Clinic, Rochester, Minnesota 55905, USA
| |
Collapse
|
78
|
Verhey KJ, Yang W. Permeability barriers for generating a unique ciliary protein and lipid composition. Curr Opin Cell Biol 2016; 41:109-16. [PMID: 27232950 DOI: 10.1016/j.ceb.2016.05.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2016] [Revised: 05/04/2016] [Accepted: 05/10/2016] [Indexed: 01/08/2023]
Abstract
Cilia (and flagella) are microtubule-based protrusions that are found in single or multiple copies on the surface of most eukaryotic cells. Defects in cilia formation and/or function have now been correlated with an expanding spectrum of human genetic diseases termed ciliopathies. Recent work indicates that cilia are indeed a bona fide organelle with a unique protein and lipid content that enables specific cellular functions. Despite the physiological and clinical relevance of cilia, our understanding of how a unique protein and lipid composition is generated for this organelle remains poor. Here we review recent work on the mechanisms that determine the protein and lipid content, and thus the functional outputs, of this unique organelle.
Collapse
Affiliation(s)
- Kristen J Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| | - Weidong Yang
- Department of Biology, Temple University, Philadelphia, PA 19122, USA
| |
Collapse
|
79
|
Wang S, Livingston MJ, Su Y, Dong Z. Reciprocal regulation of cilia and autophagy via the MTOR and proteasome pathways. Autophagy 2016; 11:607-16. [PMID: 25906314 DOI: 10.1080/15548627.2015.1023983] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Primary cilium is an organelle that plays significant roles in a number of cellular functions ranging from cell mechanosensation, proliferation, and differentiation to apoptosis. Autophagy is an evolutionarily conserved cellular function in biology and indispensable for cellular homeostasis. Both cilia and autophagy have been linked to different types of genetic and acquired human diseases. Their interaction has been suggested very recently, but the underlying mechanisms are still not fully understood. We examined autophagy in cells with suppressed cilia and measured cilium length in autophagy-activated or -suppressed cells. It was found that autophagy was repressed in cells with short cilia. Further investigation showed that MTOR activation was enhanced in cilia-suppressed cells and the MTOR inhibitor rapamycin could largely reverse autophagy suppression. In human kidney proximal tubular cells (HK2), autophagy induction was associated with cilium elongation. Conversely, autophagy inhibition by 3-methyladenine (3-MA) and chloroquine (CQ) as well as bafilomycin A1 (Baf) led to short cilia. Cilia were also shorter in cultured atg5-knockout (KO) cells and in atg7-KO kidney proximal tubular cells in mice. MG132, an inhibitor of the proteasome, could significantly restore cilium length in atg5-KO cells, being concomitant with the proteasome activity. Together, the results suggest that cilia and autophagy regulate reciprocally through the MTOR signaling pathway and ubiquitin-proteasome system.
Collapse
Key Words
- 3-MA, 3-methyladenine
- 70kDa, polypeptide 1
- ANKS6, ankyrin repeat and sterile α motif domain containing 6
- ATG/atg, autophagy-related
- Ac-TUBA, acetylated-tubulin α
- Baf, bafilomycin A1
- CF, confluence
- CQ, chloroquine
- DAPI, 4′-6-diamidino-2-phenylindole
- FBS, fetal bovine serum
- HK2, human kidney proximal tubular cells
- IFT, intraflagellar transport
- KAP3, kinesin family-associated protein 3
- KD, knockdown
- KIF3A/3B, kinesin family member 3A/3B
- KO, knockout
- LTA, lotus tetragonolobus agglutinin
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β
- MEF, mouse embryonic fibroblast
- MTOR
- MTOR, mechanistic target of rapamycin
- OFD1, oral-ficial-digital syndrome 1
- PBS, phosphate-buffered saline
- PKD, polycystic kidney disease
- RKRB, Krebs-Henseleit saline containing 25 mM NaHCO3
- RPS6KB1, ribosomal protein S6 kinase
- Rapa, rapamycin
- SD, standard deviation
- autophagy
- cilia
- polycystic kidney disease
- proteasome
Collapse
Affiliation(s)
- Shixuan Wang
- a Department of Cellular Biology and Anatomy ; Medical College of Georgia; Georgia Reagents University and Charlie Norwood VA Medical Center ; Augusta , GA USA
| | | | | | | |
Collapse
|
80
|
Takao D, Verhey KJ. Gated entry into the ciliary compartment. Cell Mol Life Sci 2016; 73:119-27. [PMID: 26472341 PMCID: PMC4959937 DOI: 10.1007/s00018-015-2058-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 09/28/2015] [Accepted: 09/29/2015] [Indexed: 11/26/2022]
Abstract
Cilia and flagella play important roles in cell motility and cell signaling. These functions require that the cilium establishes and maintains a unique lipid and protein composition. Recent work indicates that a specialized region at the base of the cilium, the transition zone, serves as both a barrier to entry and a gate for passage of select components. For at least some cytosolic proteins, the barrier and gate functions are provided by a ciliary pore complex (CPC) that shares molecular and mechanistic properties with nuclear gating. Specifically, nucleoporins of the CPC limit the diffusional entry of cytosolic proteins in a size-dependent manner and enable the active transport of large molecules and complexes via targeting signals, importins, and the small G protein Ran. For membrane proteins, the septin protein SEPT2 is part of the barrier to entry whereas the gating function is carried out and/or regulated by proteins associated with ciliary diseases (ciliopathies) such as nephronophthisis, Meckel–Gruber syndrome and Joubert syndrome. Here, we discuss the evidence behind these models of ciliary gating as well as the similarities to and differences from nuclear gating.
Collapse
Affiliation(s)
- Daisuke Takao
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI 48109 USA
| | - Kristen J. Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Pl, Ann Arbor, MI 48109 USA
| |
Collapse
|
81
|
Abstract
Cilia and flagella are microtubule-based organelles that play important roles in human health by contributing to cellular motility as well as sensing and responding to environmental cues. Defects in cilia formation and function cause a broad class of human genetic diseases called ciliopathies. To carry out their specialized functions, cilia contain a unique complement of proteins that must be imported into the ciliary compartment. In this chapter, we describe methods to measure the permeability barrier of the ciliary gate by microinjection of fluorescent proteins and dextrans of different sizes into ciliated cells. We also describe a fluorescence recovery after photobleaching (FRAP) assay to measure the entry of ciliary proteins into the ciliary compartment. These assays can be used to determine the molecular mechanisms that regulate the formation and function of cilia in mammalian cells.
Collapse
Affiliation(s)
- Daisuke Takao
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Kristen J Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA.
| |
Collapse
|
82
|
Garcia-Gonzalo FR, Phua SC, Roberson EC, Garcia G, Abedin M, Schurmans S, Inoue T, Reiter JF. Phosphoinositides Regulate Ciliary Protein Trafficking to Modulate Hedgehog Signaling. Dev Cell 2015; 34:400-409. [PMID: 26305592 DOI: 10.1016/j.devcel.2015.08.001] [Citation(s) in RCA: 230] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 08/01/2015] [Accepted: 08/05/2015] [Indexed: 12/17/2022]
Abstract
Primary cilia interpret vertebrate Hedgehog (Hh) signals. Why cilia are essential for signaling is unclear. One possibility is that some forms of signaling require a distinct membrane lipid composition, found at cilia. We found that the ciliary membrane contains a particular phosphoinositide, PI(4)P, whereas a different phosphoinositide, PI(4,5)P2, is restricted to the membrane of the ciliary base. This distribution is created by Inpp5e, a ciliary phosphoinositide 5-phosphatase. Without Inpp5e, ciliary PI(4,5)P2 levels are elevated and Hh signaling is disrupted. Inpp5e limits the ciliary levels of inhibitors of Hh signaling, including Gpr161 and the PI(4,5)P2-binding protein Tulp3. Increasing ciliary PI(4,5)P2 levels or conferring the ability to bind PI(4)P on Tulp3 increases the ciliary localization of Tulp3. Lowering Tulp3 in cells lacking Inpp5e reduces ciliary Gpr161 levels and restores Hh signaling. Therefore, Inpp5e regulates ciliary membrane phosphoinositide composition, and Tulp3 reads out ciliary phosphoinositides to control ciliary protein localization, enabling Hh signaling.
Collapse
Affiliation(s)
- Francesc R Garcia-Gonzalo
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Siew C Phua
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Elle C Roberson
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Galo Garcia
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Monika Abedin
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
| | - Stéphane Schurmans
- Laboratory of Functional Genetics, GIGA-Research Centre, Université de Liège, 4000-Liège, Belgium
| | - Takanari Inoue
- Department of Cell Biology and Center for Cell Dynamics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics and Cardiovascular Research Institute, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
| |
Collapse
|
83
|
Recruitment of β-Arrestin into Neuronal Cilia Modulates Somatostatin Receptor Subtype 3 Ciliary Localization. Mol Cell Biol 2015; 36:223-35. [PMID: 26503786 DOI: 10.1128/mcb.00765-15] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 10/20/2015] [Indexed: 01/09/2023] Open
Abstract
Primary cilia are essential sensory and signaling organelles present on nearly every mammalian cell type. Defects in primary cilia underlie a class of human diseases collectively termed ciliopathies. Primary cilia are restricted subcellular compartments, and specialized mechanisms coordinate the localization of proteins to cilia. Moreover, trafficking of proteins into and out of cilia is required for proper ciliary function, and this process is disrupted in ciliopathies. The somatostatin receptor subtype 3 (Sstr3) is selectively targeted to primary cilia on neurons in the mammalian brain and is implicated in learning and memory. Here, we show that Sstr3 localization to cilia is dynamic and decreases in response to somatostatin treatment. We further show that somatostatin treatment stimulates β-arrestin recruitment into Sstr3-positive cilia and this recruitment can be blocked by mutations in Sstr3 that impact agonist binding or phosphorylation. Importantly, somatostatin treatment fails to decrease Sstr3 ciliary localization in neurons lacking β-arrestin 2. Together, our results implicate β-arrestin in the modulation of Sstr3 ciliary localization and further suggest a role for β-arrestin in the mediation of Sstr3 ciliary signaling.
Collapse
|
84
|
Photoreceptor Sensory Cilium: Traversing the Ciliary Gate. Cells 2015; 4:674-86. [PMID: 26501325 PMCID: PMC4695852 DOI: 10.3390/cells4040674] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 10/07/2015] [Accepted: 10/09/2015] [Indexed: 01/13/2023] Open
Abstract
Cilia are antenna-like extensions of the plasma membrane found in nearly all cell types. In the retina of the eye, photoreceptors develop unique sensory cilia. Not much was known about the mechanisms underlying the formation and function of photoreceptor cilia, largely because of technical limitations and the specific structural and functional modifications that cannot be modeled in vitro. With recent advances in microscopy techniques and molecular and biochemical approaches, we are now beginning to understand the molecular basis of photoreceptor ciliary architecture, ciliary function and its involvement in human diseases. Here, I will discuss the studies that have revealed new knowledge of how photoreceptor cilia regulate their identity and function while coping with high metabolic and trafficking demands associated with processing light signal.
Collapse
|
85
|
Phua SC, Lin YC, Inoue T. An intelligent nano-antenna: Primary cilium harnesses TRP channels to decode polymodal stimuli. Cell Calcium 2015; 58:415-22. [PMID: 25828566 PMCID: PMC4564334 DOI: 10.1016/j.ceca.2015.03.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 11/30/2022]
Abstract
The primary cilium is a solitary hair-like organelle on the cell surface that serves as an antenna sensing ever-changing environmental conditions. In this review, we will first recapitulate the molecular basis of the polymodal sensory function of the primary cilia, specifically focusing on transient receptor potential (TRP) channels that accumulate inside the organelle and conduct calcium ions (Ca(2+)). Each subfamily member, namely TRPP2 TRPP3, TRPC1 and TRPV4, is gated by multiple environmental factors, including chemical (receptor ligands, intracellular second messengers such as Ca(2+)), mechanical (fluid shear stress, hypo-osmotic swelling), or physical (temperature, voltage) stimuli. Both activity and heterodimer compositions of the TRP channels may be dynamically regulated for precise tuning to the varying dynamic ranges of the individual input stimuli. We will thus discuss the potential regulation of TRP channels by local second messengers. Despite its reported importance in embryonic patterning and tissue morphogenesis, the precise functional significance of the downstream Ca(2+) signals of the TRP channels remains unknown. We will close our review by featuring recent technological advances in visualizing and analyzing signal transduction inside the primary cilia, together with current perspectives illuminating the functional significance of intraciliary Ca(2+) signals.
Collapse
Affiliation(s)
- Siew Cheng Phua
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
| | - Yu-Chun Lin
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Takanari Inoue
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Precursory Research for Embryonic Science and Technology (PRESTO) Investigator, Japan Science and Technology Agency (JST), Saitama 332-0012, Japan.
| |
Collapse
|
86
|
Wei Q, Ling K, Hu J. The essential roles of transition fibers in the context of cilia. Curr Opin Cell Biol 2015; 35:98-105. [PMID: 25988548 DOI: 10.1016/j.ceb.2015.04.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/18/2015] [Accepted: 04/23/2015] [Indexed: 12/18/2022]
Abstract
Once thought of as a vestigial organelle, the primary cilium is now recognized as a signaling hub for key cellular pathways in vertebrate development. The recent renaissance in cilia studies significantly improved our understanding of how cilia form and function, but little is known about how ciliogenesis is initiated and how ciliary proteins enter cilia. These important ciliary events require transition fibers (TFs) that are positioned at the ciliary base as symmetric nine-bladed propeller fibrous structures. Up until recently, TFs have been the most underappreciated ciliary structures due to limited knowledge about their molecular composition and function. Here, we highlight recent advances in our understanding of TF composition and the indispensable roles of TFs in regulating the initiation of ciliogenesis and the selective import of ciliary proteins.
Collapse
Affiliation(s)
- Qing Wei
- Department of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Jinghua Hu
- Department of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA; Mayo Translational PKD Center, Rochester, MN, USA; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA.
| |
Collapse
|
87
|
McIntyre JC, Joiner AM, Zhang L, Iñiguez-Lluhí J, Martens JR. SUMOylation regulates ciliary localization of olfactory signaling proteins. J Cell Sci 2015; 128:1934-45. [PMID: 25908845 PMCID: PMC4457158 DOI: 10.1242/jcs.164673] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 03/24/2015] [Indexed: 11/20/2022] Open
Abstract
Cilia are evolutionarily conserved organelles found on many mammalian cell types, including neuronal populations. Although neuronal cilia, including those on olfactory sensory neurons (OSNs), are often delineated by localization of adenylyl cyclase 3 (AC3, also known as ADCY3), the mechanisms responsible for targeting integral membrane proteins are largely unknown. Post-translational modification by small ubiquitin-like modifier (SUMO) proteins plays an important role in protein localization processes such as nuclear-cytosolic transport. Here, we identified through bioinformatic analysis that adenylyl cyclases harbor conserved SUMOylation motifs, and show that AC3 is a substrate for SUMO modification. Functionally, overexpression of the SUMO protease SENP2 prevented ciliary localization of AC3, without affecting ciliation or cilia maintenance. Furthermore, AC3-SUMO mutants did not localize to cilia. To test whether SUMOylation is sufficient for cilia entry, we compared localization of ANO2, which possesses a SUMO motif, and ANO1, which lacks SUMOylation sites and does not localize to cilia. Introduction of SUMOylation sites into ANO1 was not sufficient for ciliary entry. These data suggest that SUMOylation is necessary but not sufficient for ciliary trafficking of select constituents, further establishing the link between ciliary and nuclear import.
Collapse
Affiliation(s)
- Jeremy C McIntyre
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, USA
| | - Ariell M Joiner
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lian Zhang
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, USA
| | - Jorge Iñiguez-Lluhí
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jeffrey R Martens
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, USA
| |
Collapse
|
88
|
Narita K, Takeda S. Cilia in the choroid plexus: their roles in hydrocephalus and beyond. Front Cell Neurosci 2015; 9:39. [PMID: 25729351 PMCID: PMC4325912 DOI: 10.3389/fncel.2015.00039] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 01/27/2015] [Indexed: 12/21/2022] Open
Abstract
Cilia are whip-like projections that are widely conserved in eukaryotes and function as a motile propeller and/or sensory platform to detect various extracellular stimuli. In vertebrates, cilia are ubiquitously found in most cells, showing structural and functional diversities depending on the cell type. In this review, we focus on the structure and function of cilia in choroid plexus epithelial cells (CPECs). CPECs form one or two dozen non-motile 9+0 cilia, which display transient acquisition of motility during development. Genetic malfunction of cilia can lead to failure of multiple organs including the brain. Especially, several groups have demonstrated that the defects in CPEC cilia cause the communicating form of hydrocephalus. In order to elucidate the molecular mechanisms underlying the hydrocephalus, we have previously demonstrated that the cilia possess an NPFF receptor for autocrine signaling to regulate transepithelial fluid transport. In this perspective, we also discuss the potential involvement of cilia in the other aspects of choroid plexus functions, such as the regulation of brain development and neuroinflammation.
Collapse
Affiliation(s)
- Keishi Narita
- Department of Anatomy and Cell Biology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi Chuo, Yamanashi, Japan
| | - Sen Takeda
- Department of Anatomy and Cell Biology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi Chuo, Yamanashi, Japan
| |
Collapse
|
89
|
Chong YC, Mann RK, Zhao C, Kato M, Beachy PA. Bifurcating action of Smoothened in Hedgehog signaling is mediated by Dlg5. Genes Dev 2015; 29:262-76. [PMID: 25644602 PMCID: PMC4318143 DOI: 10.1101/gad.252676.114] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 12/29/2014] [Indexed: 12/19/2022]
Abstract
Binding of the Hedgehog (Hh) protein signal to its receptor, Patched, induces accumulation of the seven-pass transmembrane protein Smoothened (Smo) within the primary cilium and of the zinc finger transcription factor Gli2 at the ciliary tip, resulting ultimately in Gli-mediated changes in nuclear gene expression. However, the mechanism by which pathway activation is communicated from Smo to Gli2 is not known. In an effort to elucidate this mechanism, we identified Dlg5 (Discs large, homolog 5) in a biochemical screen for proteins that preferentially interact with activated Smo. We found that disruption of Smo-Dlg5 interactions or depletion of endogenous Dlg5 leads to diminished Hh pathway response without a significant impact on Smo ciliary accumulation. We also found that Dlg5 is localized at the basal body, where it associates with another pathway component, Kif7. We show that Dlg5 is required for Hh-induced enrichment of Kif7 and Gli2 at the tip of the cilium but is dispensable for Gpr161 exit from the cilium and the consequent suppression of Gli3 processing into its repressor form. Our findings suggest a bifurcation of Smo activity in Hh response, with a Dlg5-independent arm for suppression of Gli repressor formation and a second arm involving Smo interaction with Dlg5 for Gli activation.
Collapse
Affiliation(s)
- Yong Chun Chong
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA; Department of Developmental Biology, Stanford University, Stanford, California 94305, USA; Department of Biochemistry, Stanford University, Stanford, California 94305, USA
| | - Randall K Mann
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA; Department of Developmental Biology, Stanford University, Stanford, California 94305, USA; Department of Biochemistry, Stanford University, Stanford, California 94305, USA
| | - Chen Zhao
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA; Department of Developmental Biology, Stanford University, Stanford, California 94305, USA; Department of Biochemistry, Stanford University, Stanford, California 94305, USA
| | - Masaki Kato
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA; Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
| | - Philip A Beachy
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Stanford, California 94305, USA; Department of Developmental Biology, Stanford University, Stanford, California 94305, USA; Department of Biochemistry, Stanford University, Stanford, California 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
| |
Collapse
|
90
|
Craft JM, Harris JA, Hyman S, Kner P, Lechtreck KF. Tubulin transport by IFT is upregulated during ciliary growth by a cilium-autonomous mechanism. ACTA ACUST UNITED AC 2015; 208:223-37. [PMID: 25583998 PMCID: PMC4298693 DOI: 10.1083/jcb.201409036] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In Chlamydomonas cilia, IFT concentrates soluble tubulin by regulating IFT train occupancy and thereby promotes elongation of axonemal microtubules. The assembly of the axoneme, the structural scaffold of cilia and flagella, requires translocation of a vast quantity of tubulin into the growing cilium, but the mechanisms that regulate the targeting, quantity, and timing of tubulin transport are largely unknown. In Chlamydomonas, GFP-tagged α-tubulin enters cilia as an intraflagellar transport (IFT) cargo and by diffusion. IFT-based transport of GFP-tubulin is elevated in growing cilia and IFT trains carry more tubulin. Cells possessing both nongrowing and growing cilia selectively target GFP-tubulin into the latter. The preferential delivery of tubulin boosts the concentration of soluble tubulin in the matrix of growing versus steady-state cilia. Cilia length mutants show abnormal kinetics of tubulin transport. We propose that cells regulate the extent of occupancy of IFT trains by tubulin cargoes. During ciliary growth, IFT concentrates soluble tubulin in cilia and thereby promotes elongation of the axonemal microtubules.
Collapse
Affiliation(s)
- Julie M Craft
- Department of Cellular Biology and College of Engineering, University of Georgia, Athens, GA 30602
| | - J Aaron Harris
- Department of Cellular Biology and College of Engineering, University of Georgia, Athens, GA 30602
| | - Sebastian Hyman
- Department of Cellular Biology and College of Engineering, University of Georgia, Athens, GA 30602
| | - Peter Kner
- Department of Cellular Biology and College of Engineering, University of Georgia, Athens, GA 30602
| | - Karl F Lechtreck
- Department of Cellular Biology and College of Engineering, University of Georgia, Athens, GA 30602
| |
Collapse
|
91
|
Takao D, Dishinger JF, Kee HL, Pinskey JM, Allen BL, Verhey KJ. An assay for clogging the ciliary pore complex distinguishes mechanisms of cytosolic and membrane protein entry. Curr Biol 2014; 24:2288-94. [PMID: 25264252 DOI: 10.1016/j.cub.2014.08.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 07/08/2014] [Accepted: 08/07/2014] [Indexed: 01/25/2023]
Abstract
As a cellular organelle, the cilium contains a unique protein composition. Entry of both membrane and cytosolic components is tightly regulated by gating mechanisms at the cilium base; however, the mechanistic details of ciliary gating are largely unknown. We previously proposed that entry of cytosolic components is regulated by mechanisms similar to those of nuclear transport and is dependent on nucleoporins (NUPs), which comprise a ciliary pore complex (CPC). To investigate ciliary gating mechanisms, we developed a system to clog the pore by inhibiting NUP function via forced dimerization. We targeted NUP62, a component of the central channel of the nuclear pore complex (NPC), for forced dimerization by tagging it with the homodimerizing Fv domain. As proof of principle, we show that forced dimerization of NUP62-Fv attenuated (1) active transport of BSA into the nuclear compartment and (2) the kinesin-2 motor KIF17 into the ciliary compartment. Using the pore-clogging technique, we find that forced dimerization of NUP62 attenuated the gated entry of cytosolic proteins but did not affect entry of membrane proteins or diffusional entry of small cytosolic proteins. We propose a model in which active transport of cytosolic proteins into both nuclear and ciliary compartments requires functional NUPs of the central pore, whereas lateral entry of membrane proteins utilizes a different mechanism that is likely specific to each organelle's limiting membrane.
Collapse
Affiliation(s)
- Daisuke Takao
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - John F Dishinger
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - H Lynn Kee
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Justine M Pinskey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Ben L Allen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Kristen J Verhey
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| |
Collapse
|
92
|
Alford LM, Mattheyses AL, Hunter EL, Lin H, Dutcher SK, Sale WS. The Chlamydomonas mutant pf27 reveals novel features of ciliary radial spoke assembly. Cytoskeleton (Hoboken) 2014; 70:804-18. [PMID: 24124175 DOI: 10.1002/cm.21144] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 09/10/2013] [Accepted: 09/12/2013] [Indexed: 01/05/2023]
Abstract
To address the mechanisms of ciliary radial spoke assembly, we took advantage of the Chlamydomonas pf27 mutant. The radial spokes that assemble in pf27 are localized to the proximal quarter of the axoneme, but otherwise are fully assembled into 20S radial spoke complexes competent to bind spokeless axonemes in vitro. Thus, pf27 is not defective in radial spoke assembly or docking to the axoneme. Rather, our results suggest that pf27 is defective in the transport of spoke complexes. During ciliary regeneration in pf27, radial spoke assembly occurs asynchronously from other axonemal components. In contrast, during ciliary regeneration in wild-type Chlamydomonas, radial spokes and other axonemal components assemble concurrently as the axoneme grows. Complementation in temporary dikaryons between wild-type and pf27 reveals rescue of radial spoke assembly that begins at the distal tip, allowing further assembly to proceed from tip to base of the axoneme. Notably, rescued assembly of radial spokes occurred independently of the established proximal radial spokes in pf27 axonemes in dikaryons. These results reveal that 20S radial spokes can assemble proximally in the pf27 cilium but as the cilium lengthens, spoke assembly requires transport. We postulate that PF27 encodes an adaptor or modifier protein required for radial spoke–IFT interaction.
Collapse
|
93
|
Awata J, Takada S, Standley C, Lechtreck KF, Bellvé KD, Pazour GJ, Fogarty KE, Witman GB. NPHP4 controls ciliary trafficking of membrane proteins and large soluble proteins at the transition zone. J Cell Sci 2014; 127:4714-27. [PMID: 25150219 DOI: 10.1242/jcs.155275] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protein nephrocystin-4 (NPHP4) is widespread in ciliated organisms, and defects in NPHP4 cause nephronophthisis and blindness in humans. To learn more about the function of NPHP4, we have studied it in Chlamydomonas reinhardtii. NPHP4 is stably incorporated into the distal part of the flagellar transition zone, close to the membrane and distal to CEP290, another transition zone protein. Therefore, these two proteins, which are incorporated into the transition zone independently of each other, define different domains of the transition zone. An nphp4-null mutant forms flagella with nearly normal length, ultrastructure and intraflagellar transport. When fractions from isolated wild-type and nphp4 flagella were compared, few differences were observed between the axonemes, but the amounts of certain membrane proteins were greatly reduced in the mutant flagella, and cellular housekeeping proteins >50 kDa were no longer excluded from mutant flagella. Therefore, NPHP4 functions at the transition zone as an essential part of a barrier that regulates both membrane and soluble protein composition of flagella. The phenotypic consequences of NPHP4 mutations in humans likely follow from protein mislocalization due to defects in the transition zone barrier.
Collapse
Affiliation(s)
- Junya Awata
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Saeko Takada
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Clive Standley
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Karl F Lechtreck
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Karl D Bellvé
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Kevin E Fogarty
- Biomedical Imaging Group, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - George B Witman
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| |
Collapse
|
94
|
Madhivanan K, Aguilar RC. Ciliopathies: the trafficking connection. Traffic 2014; 15:1031-56. [PMID: 25040720 DOI: 10.1111/tra.12195] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 06/28/2014] [Accepted: 07/08/2014] [Indexed: 12/15/2022]
Abstract
The primary cilium (PC) is a very dynamic hair-like membrane structure that assembles/disassembles in a cell-cycle-dependent manner and is present in almost every cell type. Despite being continuous with the plasma membrane, a diffusion barrier located at the ciliary base confers the PC properties of a separate organelle with very specific characteristics and membrane composition. Therefore, vesicle trafficking is the major process by which components are acquired for cilium formation and maintenance. In fact, a system of specific sorting signals controls the right of cargo admission into the cilia. Disruption to the ciliary structure or its function leads to multiorgan diseases known as ciliopathies. These illnesses arise from a spectrum of mutations in any of the more than 50 loci linked to these conditions. Therefore, it is not surprising that symptom variability (specific manifestations and severity) among and within ciliopathies appears to be an emerging characteristic. Nevertheless, one can speculate that mutations occurring in genes whose products contribute to the overall vesicle trafficking to the PC (i.e. affecting cilia assembly) will lead to more severe symptoms, whereas those involved in the transport of specific cargoes will result in milder phenotypes. In this review, we summarize the trafficking mechanisms to the cilia and also provide a description of the trafficking defects observed in some ciliopathies which can be correlated to the severity of the pathology.
Collapse
|
95
|
Wei Q, Xu Q, Zhang Y, Li Y, Zhang Q, Hu Z, Harris PC, Torres VE, Ling K, Hu J. Transition fibre protein FBF1 is required for the ciliary entry of assembled intraflagellar transport complexes. Nat Commun 2014; 4:2750. [PMID: 24231678 PMCID: PMC3856926 DOI: 10.1038/ncomms3750] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 10/11/2013] [Indexed: 12/14/2022] Open
Abstract
Sensory organelle cilia have critical roles in mammalian embryonic development and tissue homeostasis. Intraflagellar transport (IFT) machinery is required for the assembly and maintenance of cilia. Yet, how this large complex passes through the size-dependent barrier at the ciliary base remains enigmatic. Here we report that FBF1, a highly conserved transition fibre protein, is required for the ciliary import of assembled IFT particles at the ciliary base. We cloned dyf-19, the Caenorhabditis elegans homologue of human FBF1, in a whole-genome screen for ciliogenesis mutants. DYF-19 localizes specifically to transition fibres and interacts directly with the IFT-B component DYF-11/IFT54. Although not a structural component of transition fibres, DYF-19 is required for the transit of assembled IFT particles through the ciliary base. Furthermore, we found that human FBF1 shares conserved localization and function with its worm counterpart. We conclude that FBF1 is a key functional transition fibre component that actively facilitates the ciliary entry of assembled IFT machinery.
Collapse
Affiliation(s)
- Qing Wei
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota 55905, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Abstract
The primary cilium compartmentalizes a tiny fraction of the cell surface and volume, yet many proteins are highly enriched in this area and so efficient mechanisms are necessary to concentrate them in the ciliary compartment. Here we review mechanisms that are thought to deliver protein cargo to the base of cilia and are likely to interact with ciliary gating mechanisms. Given the immense variety of ciliary cytosolic and transmembrane proteins, it is almost certain that multiple, albeit frequently interconnected, pathways mediate this process. It is also clear that none of these pathways is fully understood at the present time. Mechanisms that are discussed below facilitate ciliary localization of structural and signaling molecules, which include receptors, G-proteins, ion channels, and enzymes. These mechanisms form a basis for every aspect of cilia function in early embryonic patterning, organ morphogenesis, sensory perception and elsewhere.
Collapse
Affiliation(s)
- Jarema Malicki
- MRC Centre for Developmental and Biomedical Genetics; Department of Biomedical Science; The University of Sheffield; Sheffield, UK
| | | |
Collapse
|
97
|
Sengupta P, Barr MM. New insights into an old organelle: meeting report on biology of cilia and flagella. Traffic 2014; 15:717-26. [PMID: 24612344 DOI: 10.1111/tra.12166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 02/19/2014] [Accepted: 02/24/2014] [Indexed: 12/20/2022]
Abstract
The rising interest of the scientific community in cilia biology was evident from the fact that registration for the third FASEB conference on 'The Biology of Cilia and Flagella' closed out before the early bird deadline. Cilia and flagella are organelles of profound medical importance; defects in their structure or function result in a plethora of human diseases called ciliopathies. 240 clinicians and basic scientists from around the world gathered from 23 June 2013 to 28 June 2013 at Sheraton at the Falls, Niagara Falls, NY to present and discuss their research on this intensely studied subcellular structure. The meeting was organized by Gregory Pazour (University of Massachusetts Medical School), Bradley Yoder (University of Alabama-Birmingham), and Maureen Barr (Rutgers University) and was sponsored by the Federation of American Societies for Experimental Biology (FASEB). Here, we report highlights, points of discussion, and emerging themes from this exciting meeting.
Collapse
Affiliation(s)
- Piali Sengupta
- Department of Biology and National Center for Behavioral Genomics, Brandeis University, 415 South Street, Waltham, MA, 02454, USA
| | | |
Collapse
|
98
|
Dutcher SK. The awesome power of dikaryons for studying flagella and basal bodies in Chlamydomonas reinhardtii. Cytoskeleton (Hoboken) 2013; 71:79-94. [PMID: 24272949 DOI: 10.1002/cm.21157] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/19/2013] [Indexed: 11/08/2022]
Abstract
Cilia/flagella and basal bodies/centrioles play key roles in human health and homeostasis. Among the organisms used to study these microtubule-based organelles, the green alga Chlamydomonas reinhardtii has several advantages. One is the existence of a temporary phase of the life cycle, termed the dikaryon. These cells are formed during mating when the cells fuse and the behavior of flagella from two genetically distinguishable parents can be observed. During this stage, the cytoplasms mix allowing for a defect in the flagella of one parent to be rescued by proteins from the other parent. This offers the unique advantage of adding back wild-type gene product or labeled protein at endogenous levels that can used to monitor various flagellar and basal body phenotypes. Mutants that show rescue and ones that fail to show rescue are both informative about the nature of the flagella and basal body defects. When rescue occurs, it can be used to determine the mutant gene product and to follow the temporal and spatial patterns of flagellar assembly. This review describes many examples of insights into basal body and flagellar proteins' function and assembly that have been discovered using dikaryons and discusses the potential for further analyses.
Collapse
Affiliation(s)
- Susan K Dutcher
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri
| |
Collapse
|
99
|
Wren KN, Craft JM, Tritschler D, Schauer A, Patel DK, Smith EF, Porter ME, Kner P, Lechtreck KF. A differential cargo-loading model of ciliary length regulation by IFT. Curr Biol 2013; 23:2463-71. [PMID: 24316207 DOI: 10.1016/j.cub.2013.10.044] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/23/2013] [Accepted: 10/14/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND During the assembly and maintenance of cilia, precursor proteins need to be transported from the cell body into the organelle. Intraflagellar transport (IFT) is assumed to be the predominant protein transport pathway in cilia, but it remains largely unknown how ciliary proteins use IFT to reach their destination sites in the cilium and whether the amount of cargo transported by IFT is regulated. RESULTS Single-particle imaging showed that DRC4, a structural protein of the axoneme, moves in association with IFT particles inside Chlamydomonas reinhardtii cilia. IFT is required for DRC4 transport both into and within the cilium. DRC4 cargoes dissociate from IFT trains at the tip as well as at various sites along the length of the cilium. Unloaded DRC4 diffuses before docking at its axonemal assembly site. In growing cilia, DRC4 transport by IFT was strongly increased over the steady-state level, and the frequency decreased linearly with the increasing ciliary length. The frequency of DRC4 transport was similarly elevated in short growth-arrested cilia and remained high even when the amount of DRC4 available in the cell body was reduced. CONCLUSIONS DRC4 is a bona fide cargo of IFT. Incompletely assembled cilia trigger an increase in the amount of DRC4 cargo transported by IFT particles, and DRC4 transport is downregulated as cilia approach their steady-state length. We propose a model in which ciliary length is controlled by regulating the amount of cargo transported by IFT particles.
Collapse
Affiliation(s)
- Kathryne N Wren
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Julie M Craft
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Douglas Tritschler
- Department of Genetics, Cell Biology and Development, University of Minnesota, MN 55455, USA
| | - Alexandria Schauer
- Department of Genetics, Cell Biology and Development, University of Minnesota, MN 55455, USA
| | - Deep K Patel
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Elizabeth F Smith
- Department of Biological Science, Dartmouth College, Hanover, NH 03755, USA
| | - Mary E Porter
- Department of Genetics, Cell Biology and Development, University of Minnesota, MN 55455, USA
| | - Peter Kner
- College of Engineering, University of Georgia, Athens, GA 30602, USA
| | - Karl F Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
| |
Collapse
|
100
|
Abstract
The primary cilium that protrudes from the plasma membrane of many eukaryotic cell types is very much a cellular organelle in its own right. Its unique membrane and luminal composition is effectively compartmentalized by diffusion barrier at its base, known as the transition zone. Recent works have now shed light on the molecular components of this diffusion barrier, and revealed intriguing functional similarities with other better characterized cellular barriers.
Collapse
Affiliation(s)
- Yi Shan Lim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University Health System , MD6, 14 Medical Drive , Singapore
| | | |
Collapse
|