1
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Wolfram M, Greif A, Baidukova O, Voll H, Tauber S, Lindacher J, Hegemann P, Kreimer G. Insights into degradation and targeting of the photoreceptor channelrhodopsin-1. PLANT, CELL & ENVIRONMENT 2024; 47:4188-4211. [PMID: 38935876 DOI: 10.1111/pce.15017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 06/05/2024] [Accepted: 06/11/2024] [Indexed: 06/29/2024]
Abstract
In Chlamydomonas, the directly light-gated, plasma membrane-localized cation channels channelrhodopsins ChR1 and ChR2 are the primary photoreceptors for phototaxis. Their targeting and abundance is essential for optimal movement responses. However, our knowledge how Chlamydomonas achieves this is still at its infancy. Here we show that ChR1 internalization occurs via light-stimulated endocytosis. Prior or during endocytosis ChR1 is modified and forms high molecular mass complexes. These are the solely detectable ChR1 forms in extracellular vesicles and their abundance therein dynamically changes upon illumination. The ChR1-containing extracellular vesicles are secreted via the plasma membrane and/or the ciliary base. In line with this, ciliogenesis mutants exhibit increased ChR1 degradation rates. Further, we establish involvement of the cysteine protease CEP1, a member of the papain-type C1A subfamily. ΔCEP1-knockout strains lack light-induced ChR1 degradation, whereas ChR2 degradation was unaffected. Low light stimulates CEP1 expression, which is regulated via phototropin, a SPA1 E3 ubiquitin ligase and cyclic AMP. Further, mutant and inhibitor analyses revealed involvement of the small GTPase ARL11 and SUMOylation in ChR1 targeting to the eyespot and cilia. Our study thus defines the degradation pathway of this central photoreceptor of Chlamydomonas and identifies novel elements involved in its homoeostasis and targeting.
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Affiliation(s)
- Michaela Wolfram
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
| | - Arne Greif
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
| | - Olga Baidukova
- Institute of Biology, Experimental Biophysics, Humboldt Universität, Berlin, Germany
| | - Hildegard Voll
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
| | - Sandra Tauber
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
| | - Jana Lindacher
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
| | - Peter Hegemann
- Institute of Biology, Experimental Biophysics, Humboldt Universität, Berlin, Germany
| | - Georg Kreimer
- Department of Biology, Cell Biology, Friedrich-Alexander Universität, Erlangen-Nürnberg, Germany
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2
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Hufft-Martinez BM, Wang HH, Saadi I, Tran PV. Actin cytoskeletal regulation of ciliogenesis in development and disease. Dev Dyn 2024. [PMID: 38958410 DOI: 10.1002/dvdy.724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Revised: 05/29/2024] [Accepted: 06/15/2024] [Indexed: 07/04/2024] Open
Abstract
Primary cilia are antenna-like sensory organelles that are evolutionarily conserved in nearly all modern eukaryotes, from the single-celled green alga, Chlamydomonas reinhardtii, to vertebrates and mammals. Cilia are microtubule-based cellular projections that have adapted to perform a broad range of species-specific functions, from cell motility to detection of light and the transduction of extracellular mechanical and chemical signals. These functions render cilia essential for organismal development and survival. The high conservation of cilia has allowed for discoveries in C. reinhardtii to inform our understanding of the basic biology of mammalian primary cilia, and to provide insight into the genetic etiology of ciliopathies. Over the last two decades, a growing number of studies has revealed that multiple aspects of ciliary homeostasis are regulated by the actin cytoskeleton, including centrosome migration and positioning, vesicle transport to the basal body, ectocytosis, and ciliary-mediated signaling. Here, we review actin regulation of ciliary homeostasis, and highlight conserved and divergent mechanisms in C. reinhardtii and mammalian cells. Further, we compare the disease manifestations of patients with ciliopathies to those with mutations in actin and actin-associated genes, and propose that primary cilia defects caused by genetic alteration of the actin cytoskeleton may underlie certain birth defects.
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Affiliation(s)
- Brittany M Hufft-Martinez
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Henry H Wang
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Irfan Saadi
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
- Institute of Reproductive and Developmental Sciences, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Pamela V Tran
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
- Jared Grantham Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, USA
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3
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Patel MB, Griffin PJ, Olson SF, Dai J, Hou Y, Malik T, Das P, Zhang G, Zhao W, Witman GB, Lechtreck KF. Distribution and bulk flow analyses of the intraflagellar transport (IFT) motor kinesin-2 support an "on-demand" model for Chlamydomonas ciliary length control. Cytoskeleton (Hoboken) 2024. [PMID: 38456596 PMCID: PMC11380706 DOI: 10.1002/cm.21851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/09/2024]
Abstract
Most cells tightly control the length of their cilia. The regulation likely involves intraflagellar transport (IFT), a bidirectional motility of multi-subunit particles organized into trains that deliver building blocks into the organelle. In Chlamydomonas, the anterograde IFT motor kinesin-2 consists of the motor subunits FLA8 and FLA10 and the nonmotor subunit KAP. KAP dissociates from IFT at the ciliary tip and diffuses back to the cell body. This observation led to the diffusion-as-a-ruler model of ciliary length control, which postulates that KAP is progressively sequestered into elongating cilia because its return to the cell body will require increasingly more time, limiting motor availability at the ciliary base, train assembly, building block supply, and ciliary growth. Here, we show that Chlamydomonas FLA8 also returns to the cell body by diffusion. However, more than 95% of KAP and FLA8 are present in the cell body and, at a given time, just ~1% of the motor participates in IFT. After repeated photobleaching of both cilia, IFT of fluorescent kinesin subunits continued indicating that kinesin-2 cycles from the large cell-body pool through the cilia and back. Furthermore, growing and full-length cilia contained similar amounts of kinesin-2 subunits and the size of the motor pool at the base changed only slightly with ciliary length. These observations are incompatible with the diffusion-as-a-ruler model, but rather support an "on-demand model," in which the cargo load of the trains is regulated to assemble cilia of the desired length.
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Affiliation(s)
- Mansi B Patel
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Paul J Griffin
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Spencer F Olson
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Jin Dai
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Yuqing Hou
- Department of Radiology, UMass Chan Medical School, Worcester, Massachusetts, USA
| | - Tara Malik
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Poulomi Das
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Gui Zhang
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Winston Zhao
- Department of Radiology, UMass Chan Medical School, Worcester, Massachusetts, USA
| | - George B Witman
- Department of Radiology, UMass Chan Medical School, Worcester, Massachusetts, USA
| | - Karl F Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
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4
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Moran AL, Louzao-Martinez L, Norris DP, Peters DJM, Blacque OE. Transport and barrier mechanisms that regulate ciliary compartmentalization and ciliopathies. Nat Rev Nephrol 2024; 20:83-100. [PMID: 37872350 DOI: 10.1038/s41581-023-00773-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/19/2023] [Indexed: 10/25/2023]
Abstract
Primary cilia act as cell surface antennae, coordinating cellular responses to sensory inputs and signalling molecules that regulate developmental and homeostatic pathways. Cilia are therefore critical to physiological processes, and defects in ciliary components are associated with a large group of inherited pleiotropic disorders - known collectively as ciliopathies - that have a broad spectrum of phenotypes and affect many or most tissues, including the kidney. A central feature of the cilium is its compartmentalized structure, which imparts its unique molecular composition and signalling environment despite its membrane and cytosol being contiguous with those of the cell. Such compartmentalization is achieved via active transport pathways that bring protein cargoes to and from the cilium, as well as gating pathways at the ciliary base that establish diffusion barriers to protein exchange into and out of the organelle. Many ciliopathy-linked proteins, including those involved in kidney development and homeostasis, are components of the compartmentalizing machinery. New insights into the major compartmentalizing pathways at the cilium, namely, ciliary gating, intraflagellar transport, lipidated protein flagellar transport and ciliary extracellular vesicle release pathways, have improved our understanding of the mechanisms that underpin ciliary disease and associated renal disorders.
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Affiliation(s)
- Ailis L Moran
- School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland
| | - Laura Louzao-Martinez
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Dorien J M Peters
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
| | - Oliver E Blacque
- School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.
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5
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Zhao H, Li Q, Zhou J. Ciliary ectosomes: critical microvesicle packets transmitted from the cell tower. Sci Bull (Beijing) 2023; 68:2674-2677. [PMID: 37833188 DOI: 10.1016/j.scib.2023.09.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Affiliation(s)
- Huijie Zhao
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China.
| | - Qingchao Li
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China
| | - Jun Zhou
- Center for Cell Structure and Function, Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Shandong Normal University, Jinan 250014, China; State Key Laboratory of Medicinal Chemical Biology, Haihe Laboratory of Cell Ecosystem, College of Life Sciences, Nankai University, Tianjin 300071, China.
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6
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Derderian C, Canales GI, Reiter JF. Seriously cilia: A tiny organelle illuminates evolution, disease, and intercellular communication. Dev Cell 2023; 58:1333-1349. [PMID: 37490910 PMCID: PMC10880727 DOI: 10.1016/j.devcel.2023.06.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 01/18/2023] [Accepted: 06/30/2023] [Indexed: 07/27/2023]
Abstract
The borders between cell and developmental biology, which have always been permeable, have largely dissolved. One manifestation is the blossoming of cilia biology, with cell and developmental approaches (increasingly complemented by human genetics, structural insights, and computational analysis) fruitfully advancing understanding of this fascinating, multifunctional organelle. The last eukaryotic common ancestor probably possessed a motile cilium, providing evolution with ample opportunity to adapt cilia to many jobs. Over the last decades, we have learned how non-motile, primary cilia play important roles in intercellular communication. Reflecting their diverse motility and signaling functions, compromised cilia cause a diverse range of diseases collectively called "ciliopathies." In this review, we highlight how cilia signal, focusing on how second messengers generated in cilia convey distinct information; how cilia are a potential source of signals to other cells; how evolution may have shaped ciliary function; and how cilia research may address thorny outstanding questions.
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Affiliation(s)
- Camille Derderian
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Gabriela I Canales
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Jeremy F Reiter
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA.
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7
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Dougherty LL, Dutta S, Avasthi P. The ERK activator, BCI, inhibits ciliogenesis and causes defects in motor behavior, ciliary gating, and cytoskeletal rearrangement. Life Sci Alliance 2023; 6:e202301899. [PMID: 36914265 PMCID: PMC10011610 DOI: 10.26508/lsa.202301899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/02/2023] [Accepted: 03/03/2023] [Indexed: 03/14/2023] Open
Abstract
MAPK pathways are well-known regulators of the cell cycle, but they have also been found to control ciliary length in a wide variety of organisms and cell types from Caenorhabditis elegans neurons to mammalian photoreceptors through unknown mechanisms. ERK1/2 is a MAP kinase in human cells that is predominantly phosphorylated by MEK1/2 and dephosphorylated by the phosphatase DUSP6. We have found that the ERK1/2 activator/DUSP6 inhibitor, (E)-2-benzylidene-3-(cyclohexylamino)-2,3-dihydro-1H-inden-1-one (BCI), inhibits ciliary maintenance in Chlamydomonas and hTERT-RPE1 cells and assembly in Chlamydomonas These effects involve inhibition of total protein synthesis, microtubule organization, membrane trafficking, and KAP-GFP motor dynamics. Our data provide evidence for various avenues for BCI-induced ciliary shortening and impaired ciliogenesis that gives mechanistic insight into how MAP kinases can regulate ciliary length.
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Affiliation(s)
- Larissa L Dougherty
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH, USA
- Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS, USA
| | - Soumita Dutta
- Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS, USA
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Prachee Avasthi
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH, USA
- Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS, USA
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8
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Bigge BM, Dougherty LL, Avasthi P. Lithium-induced ciliary lengthening sparks Arp2/3 complex-dependent endocytosis. Mol Biol Cell 2023; 34:ar26. [PMID: 36753380 PMCID: PMC10092651 DOI: 10.1091/mbc.e22-06-0219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Ciliary length is highly regulated, but can be disrupted by lithium, which causes ciliary elongation across cell types and organisms. We used the algal system Chlamydomonas reinhardtii to investigate the mechanism behind lithium-induced ciliary elongation. Protein synthesis is not required for lengthening, and the target of lithium, GSK3, has substrates that can influence membrane dynamics. Further, ciliary assembly requires a supply of ciliary membrane as well as protein. Lithium-treated cilia elongate normally with brefeldin treatment, but dynasore treatment produced defective lengthening suggesting a source of membrane from the cell surface rather than the Golgi. Genetic or chemical perturbation of the Arp2/3 complex or dynamin, required for endocytosis, blocks lithium-induced ciliary lengthening. Finally, we found an increase in Arp2/3 complex- and endocytosis-dependent actin filaments near the ciliary base upon lithium treatment. Our results identify a mechanism for lithium-mediated cilium lengthening and demonstrate the endocytic pathway for cilium membrane supply in algae is likely a conserved mechanism given lithium's conserved effects across organisms.
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Affiliation(s)
- Brae M Bigge
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH 03755
| | - Larissa L Dougherty
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH 03755
| | - Prachee Avasthi
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Dartmouth College, Hanover, NH 03755
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9
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Bigge BM, Rosenthal NE, Avasthi P. Initial ciliary assembly in Chlamydomonas requires Arp2/3 complex-dependent endocytosis. Mol Biol Cell 2023; 34:ar24. [PMID: 36753382 PMCID: PMC10092647 DOI: 10.1091/mbc.e22-09-0443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Ciliary assembly, trafficking, and regulation are dependent on microtubules, but the mechanisms of ciliary assembly also require the actin cytoskeleton. Here, we dissect subcellular roles of actin in ciliogenesis by focusing on actin networks nucleated by the Arp2/3 complex in the powerful ciliary model, Chlamydomonas. We find that the Arp2/3 complex is required for the initial stages of ciliary assembly when protein and membrane are in high demand but cannot yet be supplied from the Golgi complex. We provide evidence for Arp2/3 complex-dependent endocytosis of ciliary proteins, an increase in endocytic activity upon induction of ciliary growth, and relocalization of plasma membrane proteins to newly formed cilia.
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Affiliation(s)
- Brae M Bigge
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
| | - Nicholas E Rosenthal
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
| | - Prachee Avasthi
- Biochemistry and Cell Biology Department, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755; Anatomy and Cell Biology Department, University of Kansas Medical Center, Kansas City, KS 66103
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10
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Abstract
The assembly and maintenance of most cilia and eukaryotic flagella depends on intraflagellar transport (IFT), the bidirectional movement of multi-megadalton IFT trains along the axonemal microtubules. These IFT trains function as carriers, moving ciliary proteins between the cell body and the organelle. Whereas tubulin, the principal protein of cilia, binds directly to IFT particle proteins, the transport of other ciliary proteins and complexes requires adapters that link them to the trains. Large axonemal substructures, such as radial spokes, outer dynein arms and inner dynein arms, assemble in the cell body before attaching to IFT trains, using the adapters ARMC2, ODA16 and IDA3, respectively. Ciliary import of several membrane proteins involves the putative adapter tubby-like protein 3 (TULP3), whereas membrane protein export involves the BBSome, an octameric complex that co-migrates with IFT particles. Thus, cells employ a variety of adapters, each of which is substoichiometric to the core IFT machinery, to expand the cargo range of the IFT trains. This Review summarizes the individual and shared features of the known cargo adapters and discusses their possible role in regulating the transport capacity of the IFT pathway.
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Affiliation(s)
- Karl Lechtreck
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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11
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Abstract
Cilia sense and transduce sensory stimuli, homeostatic cues and developmental signals by orchestrating signaling reactions. Extracellular vesicles (EVs) that bud from the ciliary membrane have well-studied roles in the disposal of excess ciliary material, most dramatically exemplified by the shedding of micrometer-sized blocks by photoreceptors. Shedding of EVs by cilia also affords cells with a powerful means to shorten cilia. Finally, cilium-derived EVs may enable cell-cell communication in a variety of organisms, ranging from single-cell parasites and algae to nematodes and vertebrates. Mechanistic understanding of EV shedding by cilia is an active area of study, and future progress may open the door to testing the function of ciliary EV shedding in physiological contexts. In this Cell Science at a Glance and the accompanying poster, we discuss the molecular mechanisms that drive the shedding of ciliary material into the extracellular space, the consequences of shedding for the donor cell and the possible roles that ciliary EVs may have in cell non-autonomous contexts.
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Affiliation(s)
- Irene Ojeda Naharros
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA 94143-3120, USA
| | - Maxence V. Nachury
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA 94143-3120, USA
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12
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Vinay L, Belleannée C. EV duty vehicles: Features and functions of ciliary extracellular vesicles. Front Genet 2022; 13:916233. [PMID: 36061180 PMCID: PMC9438925 DOI: 10.3389/fgene.2022.916233] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 07/08/2022] [Indexed: 12/12/2022] Open
Abstract
The primary cilium is a microtubule-based organelle that extends from a basal body at the surface of most cells. This antenna is an efficient sensor of the cell micro-environment and is instrumental to the proper development and homeostatic control of organs. Recent compelling studies indicate that, in addition to its role as a sensor, the primary cilium also emits signals through the release of bioactive extracellular vesicles (EVs). While some primary-cilium derived EVs are released through an actin-dependent ectocytosis and are called ectosomes (or large EVs, 350–500 nm), others originate from the exocytosis of multivesicular bodies and are smaller (small EVs, 50–100 nm). Ciliary EVs carry unique signaling factors, including protein markers and microRNAs (miRNAs), and participate in intercellular communication in different organism models. This review discusses the mechanism of release, the molecular features, and functions of EVs deriving from cilia, based on the existing literature.
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13
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Establishing and regulating the composition of cilia for signal transduction. Nat Rev Mol Cell Biol 2020; 20:389-405. [PMID: 30948801 DOI: 10.1038/s41580-019-0116-4] [Citation(s) in RCA: 246] [Impact Index Per Article: 61.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The primary cilium is a hair-like surface-exposed organelle of the eukaryotic cell that decodes a variety of signals - such as odorants, light and Hedgehog morphogens - by altering the local concentrations and activities of signalling proteins. Signalling within the cilium is conveyed through a diverse array of second messengers, including conventional signalling molecules (such as cAMP) and some unusual intermediates (such as sterols). Diffusion barriers at the ciliary base establish the unique composition of this signalling compartment, and cilia adapt their proteome to signalling demands through regulated protein trafficking. Much progress has been made on the molecular understanding of regulated ciliary trafficking, which encompasses not only exchanges between the cilium and the rest of the cell but also the shedding of signalling factors into extracellular vesicles.
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14
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Long H, Huang K. Transport of Ciliary Membrane Proteins. Front Cell Dev Biol 2020; 7:381. [PMID: 31998723 PMCID: PMC6970386 DOI: 10.3389/fcell.2019.00381] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/17/2019] [Indexed: 12/24/2022] Open
Abstract
Cilia and flagella are highly conserved organelles in eukaryotic cells that drive cell movement and act as cell antennae that receive and transmit signals. In addition to receiving and transducing external signals that activate signal cascades, cilia also secrete ciliary ectosomes that send signals to recipient cells, and thereby mediate cell–cell communication. Abnormal ciliary function leads to various ciliopathies, and the precise transport and localization of ciliary membrane proteins are essential for cilium function. This review summarizes current knowledge about the transport processes of ciliary membrane proteins after their synthesis at the endoplasmic reticulum: modification and sorting in the Golgi apparatus, transport through vesicles to the ciliary base, entrance into cilia through the diffusion barrier, and turnover by ectosome secretion. The molecular mechanisms and regulation involved in each step are also discussed. Transport of ciliary membrane proteins is a complex, precise cellular process coordinated among multiple organelles. By systematically analyzing the existing research, we identify topics that should be further investigated to promote progress in this field of research.
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Affiliation(s)
- Huan Long
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Kaiyao Huang
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
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15
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Jack B, Mueller DM, Fee AC, Tetlow AL, Avasthi P. Partially Redundant Actin Genes in Chlamydomonas Control Transition Zone Organization and Flagellum-Directed Traffic. Cell Rep 2019; 27:2459-2467.e3. [PMID: 31116988 PMCID: PMC6541019 DOI: 10.1016/j.celrep.2019.04.087] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/03/2018] [Accepted: 04/18/2019] [Indexed: 11/16/2022] Open
Abstract
The unicellular green alga Chlamydomonas reinhardtii is a biflagellated cell with two actin genes: one encoding a conventional actin (IDA5) and the other encoding a divergent novel actin-like protein (NAP1). Here, we probe how actin redundancy contributes to flagellar assembly. Disrupting a single actin allows complete flagellar assembly. However, when disrupting both actins using latrunculin B (LatB) treatment on the nap1 mutant background, we find that actins are necessary for flagellar growth from newly synthesized limiting flagellar proteins. Under total actin disruption, transmission electron microscopy identified an accumulation of Golgi-adjacent vesicles. We also find that there is a mislocalization of a key transition zone gating and ciliopathy protein, NPHP-4. Our experiments demonstrate that each stage of flagellar biogenesis requires redundant actin function to varying degrees, with an absolute requirement for these actins in transport of Golgi-adjacent vesicles and flagellar incorporation of newly synthesized proteins.
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Affiliation(s)
- Brittany Jack
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - David M Mueller
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Ann C Fee
- University of Missouri-Kansas City, School of Medicine, Kansas City, MO 64110, USA
| | - Ashley L Tetlow
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Prachee Avasthi
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Ophthalmology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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16
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Kamiya R, Shiba K, Inaba K, Kato-Minoura T. Release of Sticky Glycoproteins from Chlamydomonas Flagella During Microsphere Translocation on the Surface Membrane. Zoolog Sci 2018; 35:299-305. [DOI: 10.2108/zs180025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Ritsu Kamiya
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Kogiku Shiba
- Shimoda Marine Research Center, University of Tsukuba, Shimoda 5-10-1, Shizuoka 415-0025, Japan
| | - Kazuo Inaba
- Shimoda Marine Research Center, University of Tsukuba, Shimoda 5-10-1, Shizuoka 415-0025, Japan
| | - Takako Kato-Minoura
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
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17
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Gong F, Wang J, Li J. Isolation and characterization of peroxiredoxin 1 gene of Dunaliella salina. Gene 2017; 635:39-45. [DOI: 10.1016/j.gene.2017.09.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 08/05/2017] [Accepted: 09/08/2017] [Indexed: 10/18/2022]
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18
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Kumar D, Strenkert D, Patel-King RS, Leonard MT, Merchant SS, Mains RE, King SM, Eipper BA. A bioactive peptide amidating enzyme is required for ciliogenesis. eLife 2017; 6. [PMID: 28513435 PMCID: PMC5461114 DOI: 10.7554/elife.25728] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/15/2017] [Indexed: 02/06/2023] Open
Abstract
The pathways controlling cilium biogenesis in different cell types have not been fully elucidated. We recently identified peptidylglycine α-amidating monooxygenase (PAM), an enzyme required for generating amidated bioactive signaling peptides, in Chlamydomonas and mammalian cilia. Here, we show that PAM is required for the normal assembly of motile and primary cilia in Chlamydomonas, planaria and mice. Chlamydomonas PAM knockdown lines failed to assemble cilia beyond the transition zone, had abnormal Golgi architecture and altered levels of cilia assembly components. Decreased PAM gene expression reduced motile ciliary density on the ventral surface of planaria and resulted in the appearance of cytosolic axonemes lacking a ciliary membrane. The architecture of primary cilia on neuroepithelial cells in Pam-/- mouse embryos was also aberrant. Our data suggest that PAM activity and alterations in post-Golgi trafficking contribute to the observed ciliogenesis defects and provide an unanticipated, highly conserved link between PAM, amidation and ciliary assembly.
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Affiliation(s)
- Dhivya Kumar
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, United States
| | - Daniela Strenkert
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, United States
| | - Ramila S Patel-King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, United States
| | - Michael T Leonard
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, United States
| | - Sabeeha S Merchant
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, United States.,Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, United States
| | - Richard E Mains
- Department of Neuroscience, University of Connecticut Health Center, Farmington, United States
| | - Stephen M King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, United States
| | - Betty A Eipper
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, United States.,Department of Neuroscience, University of Connecticut Health Center, Farmington, United States
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19
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Hsu KS, Chuang JZ, Sung CH. The Biology of Ciliary Dynamics. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a027904. [PMID: 28062565 DOI: 10.1101/cshperspect.a027904] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The cilium is an evolutionally conserved apical membrane protrusion that senses and transduces diverse signals to regulate a wide range of cellular activities. The cilium is dynamic in length, structure, and protein composition. Dysregulation of ciliary dynamics has been linked with ciliopathies and other human diseases. The cilium undergoes cell-cycle-dependent assembly and disassembly, with ciliary resorption linked with G1-S transition and cell-fate choice. In the resting cell, the cilium remains sensitive to environmental cues for remodeling during tissue homeostasis and repair. Recent findings further reveal an interplay between the cilium and extracellular vesicles and identify bioactive cilium-derived vesicles, posing a previously unrecognized role of cilia for sending signals. The photoreceptor outer segment is a notable dynamic cilium. A recently discovered protein transport mechanism in photoreceptors maintains light-regulated homeostasis of ciliary length.
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Affiliation(s)
- Kuo-Shun Hsu
- The Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, New York 10065
| | - Jen-Zen Chuang
- The Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, New York 10065
| | - Ching-Hwa Sung
- Departments of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York 10065
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20
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Abstract
Primary cilia are small, antenna-like structures that detect mechanical and chemical cues and transduce extracellular signals. While mammalian primary cilia were first reported in the late 1800s, scientific interest in these sensory organelles has burgeoned since the beginning of the twenty-first century with recognition that primary cilia are essential to human health. Among the most common clinical manifestations of ciliary dysfunction are renal cysts. The molecular mechanisms underlying renal cystogenesis are complex, involving multiple aberrant cellular processes and signaling pathways, while initiating molecular events remain undefined. Autosomal Dominant Polycystic Kidney Disease is the most common renal cystic disease, caused by disruption of polycystin-1 and polycystin-2 transmembrane proteins, which evidence suggests must localize to primary cilia for proper function. To understand how the absence of these proteins in primary cilia may be remediated, we review intracellular trafficking of polycystins to the primary cilium. We also examine the controversial mechanisms by which primary cilia transduce flow-mediated mechanical stress into intracellular calcium. Further, to better understand ciliary function in the kidney, we highlight the LKB1/AMPK, Wnt, and Hedgehog developmental signaling pathways mediated by primary cilia and misregulated in renal cystic disease.
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21
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Ciliary Extracellular Vesicles: Txt Msg Organelles. Cell Mol Neurobiol 2016; 36:449-57. [PMID: 26983828 DOI: 10.1007/s10571-016-0345-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 02/08/2016] [Indexed: 01/12/2023]
Abstract
Cilia are sensory organelles that protrude from cell surfaces to monitor the surrounding environment. In addition to its role as sensory receiver, the cilium also releases extracellular vesicles (EVs). The release of sub-micron sized EVs is a conserved form of intercellular communication used by all three kingdoms of life. These extracellular organelles play important roles in both short and long range signaling between donor and target cells and may coordinate systemic responses within an organism in normal and diseased states. EV shedding from ciliated cells and EV-cilia interactions are evolutionarily conserved phenomena, yet remarkably little is known about the relationship between the cilia and EVs and the fundamental biology of EVs. Studies in the model organisms Chlamydomonas and Caenorhabditis elegans have begun to shed light on ciliary EVs. Chlamydomonas EVs are shed from tips of flagella and are bioactive. Caenorhabditis elegans EVs are shed and released by ciliated sensory neurons in an intraflagellar transport-dependent manner. Caenorhabditis elegans EVs play a role in modulating animal-to-animal communication, and this EV bioactivity is dependent on EV cargo content. Some ciliary pathologies, or ciliopathies, are associated with abnormal EV shedding or with abnormal cilia-EV interactions. Until the 21st century, both cilia and EVs were ignored as vestigial or cellular junk. As research interest in these two organelles continues to gain momentum, we envision a new field of cell biology emerging. Here, we propose that the cilium is a dedicated organelle for EV biogenesis and EV reception. We will also discuss possible mechanisms by which EVs exert bioactivity and explain how what is learned in model organisms regarding EV biogenesis and function may provide insight to human ciliopathies.
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22
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Kumar D, Blaby-Haas CE, Merchant SS, Mains RE, King SM, Eipper BA. Early eukaryotic origins for cilia-associated bioactive peptide-amidating activity. J Cell Sci 2016; 129:943-56. [PMID: 26787743 DOI: 10.1242/jcs.177410] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 01/13/2016] [Indexed: 01/15/2023] Open
Abstract
Ciliary axonemes and basal bodies were present in the last eukaryotic common ancestor and play crucial roles in sensing and responding to environmental cues. Peptidergic signaling, generally considered a metazoan innovation, is essential for organismal development and homeostasis. Peptidylglycine α-amidating monooxygenase (PAM) is crucial for the last step of bioactive peptide biosynthesis. However, identification of a complete PAM-like gene in green algal genomes suggests ancient evolutionary roots for bioactive peptide signaling. We demonstrate that the Chlamydomonas reinhardtii PAM gene encodes an active peptide-amidating enzyme (CrPAM) that shares key structural and functional features with the mammalian enzyme, indicating that components of the peptide biosynthetic pathway predate multicellularity. In addition to its secretory pathway localization, CrPAM localizes to cilia and tightly associates with the axonemal superstructure, revealing a new axonemal enzyme activity. This localization pattern is conserved in mammals, with PAM present in both motile and immotile sensory cilia. The conserved ciliary localization of PAM adds to the known signaling capabilities of the eukaryotic cilium and provides a potential mechanistic link between peptidergic signaling and endocrine abnormalities commonly observed in ciliopathies.
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Affiliation(s)
- Dhivya Kumar
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
| | - Crysten E Blaby-Haas
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569, USA
| | - Sabeeha S Merchant
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569, USA Institute for Genomics and Proteomics, University of California, Los Angeles, CA 90095-1569, USA
| | - Richard E Mains
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
| | - Stephen M King
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
| | - Betty A Eipper
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3401, USA Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA
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23
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Hunter EL, Sale WS, Alford LM. Analysis of Axonemal Assembly During Ciliary Regeneration in Chlamydomonas. Methods Mol Biol 2016; 1454:237-43. [PMID: 27514926 DOI: 10.1007/978-1-4939-3789-9_15] [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] [Indexed: 12/22/2022]
Abstract
Chlamydomonas reinhardtii is an outstanding model genetic organism for study of assembly of cilia. Here, methods are described for synchronization of ciliary regeneration in Chlamydomonas to analyze the sequence in which ciliary proteins assemble. In addition, the methods described allow analysis of the mechanisms involved in regulation of ciliary length, the proteins required for ciliary assembly, and the temporal expression of genes encoding ciliary proteins. Ultimately, these methods can contribute to discovery of conserved genes that when defective lead to abnormal ciliary assembly and human disease.
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Affiliation(s)
- Emily L Hunter
- Department of Cell Biology, Emory University, 465 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA, 30322, USA
| | - Winfield S Sale
- Department of Cell Biology, Emory University, 465 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA, 30322, USA.
| | - Lea M Alford
- Department of Cell Biology, Emory University, 465 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA, 30322, USA
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24
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Hu Z, Liang Y, He W, Pan J. Cilia disassembly with two distinct phases of regulation. Cell Rep 2015; 10:1803-10. [PMID: 25801021 DOI: 10.1016/j.celrep.2015.02.044] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 12/30/2014] [Accepted: 02/17/2015] [Indexed: 01/23/2023] Open
Abstract
Cilia and flagella are dynamic organelles that undergo assembly and disassembly during each cell cycle. They are structurally polarized, and the mechanisms by which these organelles are disassembled are incompletely understood. Here, we show that flagellar resorption occurs in two distinct phases of length-dependent regulation. A CDK-like kinase, encoded by flagellar shortening 1 (FLS1), is required for the normal rate of disassembly of only the distal part of the flagellum. Mechanistically, loss of function of FLS1 prevents the initial phosphorylation of CALK, an aurora-like kinase that regulates flagellar shortening, and induces the earlier onset of the inhibitory phosphorylation of CrKinesin13, a microtubule depolymerase, which is involved in flagellar shortening. In addition, CALK and CrKinesin13 phosphorylation can also be induced by the process of flagellar shortening itself, demonstrating an example of cilia-generated signaling not requiring the binding of a ligand or the stimulation of an ion channel.
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25
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Cao M, Ning J, Hernandez-Lara CI, Belzile O, Wang Q, Dutcher SK, Liu Y, Snell WJ. Uni-directional ciliary membrane protein trafficking by a cytoplasmic retrograde IFT motor and ciliary ectosome shedding. eLife 2015; 4. [PMID: 25688564 PMCID: PMC4362204 DOI: 10.7554/elife.05242] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Accepted: 02/14/2015] [Indexed: 12/22/2022] Open
Abstract
The role of the primary cilium in key signaling pathways depends on dynamic regulation of ciliary membrane protein composition, yet we know little about the motors or membrane events that regulate ciliary membrane protein trafficking in existing organelles. Recently, we showed that cilium-generated signaling in Chlamydomonas induced rapid, anterograde IFT-independent, cytoplasmic microtubule-dependent redistribution of the membrane polypeptide, SAG1-C65, from the plasma membrane to the periciliary region and the ciliary membrane. Here, we report that the retrograde IFT motor, cytoplasmic dynein 1b, is required in the cytoplasm for this rapid redistribution. Furthermore, signaling-induced trafficking of SAG1-C65 into cilia is unidirectional and the entire complement of cellular SAG1-C65 is shed during signaling and can be recovered in the form of ciliary ectosomes that retain signal-inducing activity. Thus, during signaling, cells regulate ciliary membrane protein composition through cytoplasmic action of the retrograde IFT motor and shedding of ciliary ectosomes. DOI:http://dx.doi.org/10.7554/eLife.05242.001 Nearly every cell in the human body has slender, hair-like structures known as cilia that project outwards from its surface. These structures can sense and respond to light, chemicals and touch, and they are required for normal development. Failure of cilia to form or function in the correct manner can lead to severe diseases—such as kidney disorders, deafness and loss of vision. A major puzzle for researchers who study cilia has been to understand how cells change the composition of these structures as part of their response to a sensory input. Cilia are ancient structures that were present in early single-celled organisms and researchers interested in cilia have often used a single-celled green alga called Chlamydomonas reinhardtii as a model system for their studies. When these algae reproduce sexually, the two types of sex cells sense the presence of each other when their cilia touch and then stick together. This ciliary touching activates signals that are sent into the cells to get them ready to fuse together, much like sperm and egg cells do in animals. Both ciliary touching and signaling depend on a protein called SAG1, a part of which (known as SAG1-C65) is normally found mostly over the surface membrane of C. reinhardtii. Only very small amounts of SAG1-C65 are normally found on cilia; but, when the sex cells' cilia touch, this protein rapidly moves to the end of the cell nearest the cilia via a previously unknown mechanism. SAG1-C65 then becomes much more enriched in the cilia. Cao, Ning, Hernandez-Lara et al. investigated this process and found that SAG1-C65 movement requires a molecular motor called ‘cytoplasmic dynein’. This motor protein typically walks along the inside of cilia to transport other molecules away from the tip and towards the cell membrane. However, Cao, Ning, Hernandez-Lara et al. found that this dynein also carries SAG1-C65 from the membrane of the cells towards the base of the cilia in preparation for it to enter into these structures. As part of an effort to understand the fate of the protein after it entered cilia, Cao, Ning, Hernandez-Lara et al. discovered that the SAG1-C65 disappeared from the structures without returning to the cell membrane. Instead, SAG1-C65 was packaged within tiny bubble-like structures near the tips of cilia and these packages were then shed from cilia into the external environment. This discovery challenges a widely held view that proteins are only removed from cilia by returning to the cell. Future work will be required to understand more of the molecular details of these processes, which are likely to be present in most cells with cilia. DOI:http://dx.doi.org/10.7554/eLife.05242.002
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Affiliation(s)
- Muqing Cao
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jue Ning
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Carmen I Hernandez-Lara
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Olivier Belzile
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Qian Wang
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Susan K Dutcher
- Department of Genetics, Washington University, St. Louis, United States
| | - Yanjie Liu
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - William J Snell
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
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26
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Ciliary ectosomes: transmissions from the cell's antenna. Trends Cell Biol 2015; 25:276-85. [PMID: 25618328 DOI: 10.1016/j.tcb.2014.12.008] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 12/20/2014] [Accepted: 12/22/2014] [Indexed: 12/21/2022]
Abstract
The cilium is the site of function for a variety of membrane receptors, enzymes and signal transduction modules crucial for a spectrum of cellular processes. Through targeted transport and selective gating mechanisms, the cell localizes specific proteins to the cilium that equip it for the role of sensory antenna. This capacity of the cilium to serve as a specialized compartment where specific proteins can be readily concentrated for sensory reception also makes it an ideal organelle to employ for the regulated emission of specific biological material and information. In this review we present and discuss an emerging body of evidence centered on ciliary ectosomes - bioactive vesicles released from the surface of the cilium.
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Diener DR, Lupetti P, Rosenbaum JL. Proteomic analysis of isolated ciliary transition zones reveals the presence of ESCRT proteins. Curr Biol 2015; 25:379-384. [PMID: 25578910 DOI: 10.1016/j.cub.2014.11.066] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 11/13/2014] [Accepted: 11/20/2014] [Indexed: 10/24/2022]
Abstract
The transition zone (TZ) is a specialized region of the cilium characterized by Y-shaped connectors between the microtubules of the ciliary axoneme and the ciliary membrane [1]. Located near the base of the cilium, the TZ is in the prime location to act as a gate for proteins into and out of the ciliary compartment, a role supported by experimental evidence [2-6]. The importance of the TZ has been underscored by studies showing that mutations affecting proteins located in the TZ result in cilia-related diseases, or ciliopathies, presenting symptoms including renal cysts, retinal degeneration, and situs inversus [7-9]. Some TZ proteins have been identified and shown to interact with each other through coprecipitation studies in vertebrate cells [4, 10, 11] and genetics studies in C. elegans [3]. As a distinct approach to identify TZ proteins, we have taken advantage of the biology of Chlamydomonas to isolate TZs. Proteomic analysis identified 115 proteins, ten of which were known TZ proteins related to ciliopathies, indicating that the preparation was highly enriched for TZs. Interestingly, six proteins of the endosomal sorting complexes required for transport (ESCRT) were also associated with the TZs. Identification of these and other proteins in the TZ will provide new insights into functions of the TZ, as well as candidate ciliopathy genes.
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Affiliation(s)
- Dennis R Diener
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA.
| | - Pietro Lupetti
- Department of Life Sciences, University of Siena, Siena 53100, Italy
| | - Joel L Rosenbaum
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA.
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28
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Wood CR, Rosenbaum JL. Proteins of the ciliary axoneme are found on cytoplasmic membrane vesicles during growth of cilia. Curr Biol 2014; 24:1114-20. [PMID: 24814148 PMCID: PMC4096978 DOI: 10.1016/j.cub.2014.03.047] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 02/24/2014] [Accepted: 03/14/2014] [Indexed: 12/01/2022]
Abstract
The cilium is a specialized extension of the cell in which many specific proteins are admitted and retained, while many others are excluded or expelled. In order to maintain the organelle, the cell must possess mechanisms for the selective gating of protein entry, as well as for the targeted transport of proteins to the cilium from their sites of synthesis within the cell [1-4]. We hypothesized that the cell employs cytoplasmic vesicles as vehicles not only for the transport of proteins destined for the ciliary membrane but also for the transport of axonemal proteins to the cilium by means of peripheral association with vesicles. To test this hypothesis, we employed two different experimental strategies: (1) isolation and biochemical characterization of cytoplasmic vesicles that carry ciliary proteins, and (2) in situ localization of ciliary proteins on cytoplasmic vesicle surfaces using gold labeling and electron microscopy. Our findings indicate that structural proteins destined for the ciliary axoneme are attached to the outer surfaces of cytoplasmic vesicles that carry integral ciliary membrane proteins during the process of ciliary growth.
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Affiliation(s)
- Christopher R Wood
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Joel L Rosenbaum
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.
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29
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Dentler W. Ciliary and Flagellar Membrane Vesicle (Ectosome) Purification. Bio Protoc 2014. [DOI: 10.21769/bioprotoc.1156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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30
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Morga B, Bastin P. Getting to the heart of intraflagellar transport using Trypanosoma and Chlamydomonas models: the strength is in their differences. Cilia 2013; 2:16. [PMID: 24289478 PMCID: PMC4015504 DOI: 10.1186/2046-2530-2-16] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 11/11/2013] [Indexed: 11/22/2022] Open
Abstract
Cilia and flagella perform diverse roles in motility and sensory perception, and defects in their construction or their function are responsible for human genetic diseases termed ciliopathies. Cilia and flagella construction relies on intraflagellar transport (IFT), the bi-directional movement of ‘trains’ composed of protein complexes found between axoneme microtubules and the flagellum membrane. Although extensive information about IFT components and their mode of action were discovered in the green algae Chlamydomonas reinhardtii, other model organisms have revealed further insights about IFT. This is the case of Trypanosoma brucei, a flagellated protist responsible for sleeping sickness that is turning out to be an emerging model for studying IFT. In this article, we review different aspects of IFT, based on studies of Chlamydomonas and Trypanosoma. Data available from both models are examined to ask challenging questions about IFT such as the initiation of flagellum construction, the setting-up of IFT and the mode of formation of IFT trains, and their remodeling at the tip as well as their recycling at the base. Another outstanding question is the individual role played by the multiple IFT proteins. The use of different models, bringing their specific biological and experimental advantages, will be invaluable in order to obtain a global understanding of IFT.
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Affiliation(s)
- Benjamin Morga
- Trypanosome Cell Biology Unit, Institut Pasteur and CNRS, URA 2581, 25 rue du Docteur Roux, 75015, Paris, France.
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31
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Kubo T, Yanagisawa HA, Liu Z, Shibuya R, Hirono M, Kamiya R. A conserved flagella-associated protein in Chlamydomonas, FAP234, is essential for axonemal localization of tubulin polyglutamylase TTLL9. Mol Biol Cell 2013; 25:107-17. [PMID: 24196831 PMCID: PMC3873882 DOI: 10.1091/mbc.e13-07-0424] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A novel axonemal protein, FAP234, of Chlamydomonas is found to form a complex with a tubulin-polyglutamylating enzyme, TTLL9, and function in the stabilization and intraflagellar transport of TTLL9. These proteins are conserved in most ciliated organisms and may be specialized for regulation of ciliary motility. Tubulin undergoes various posttranslational modifications, including polyglutamylation, which is catalyzed by enzymes belonging to the tubulin tyrosine ligase–like protein (TTLL) family. A previously isolated Chlamydomonas reinhardtii mutant, tpg1, carries a mutation in a gene encoding a homologue of mammalian TTLL9 and displays lowered motility because of decreased polyglutamylation of axonemal tubulin. Here we identify a novel tpg1-like mutant, tpg2, which carries a mutation in the gene encoding FAP234, a flagella-associated protein of unknown function. Immunoprecipitation and sucrose density gradient centrifugation experiments show that FAP234 and TTLL9 form a complex. The mutant tpg1 retains FAP234 in the cell body and flagellar matrix but lacks it in the axoneme. In contrast, tpg2 lacks both TTLL9 and FAP234 in all fractions. In fla10, a temperature-sensitive mutant deficient in intraflagellar transport (IFT), both TTLL9 and FAP234 are lost from the flagellum at nonpermissive temperatures. These and other results suggest that FAP234 functions in stabilization and IFT-dependent transport of TTLL9. Both TTLL9 and FAP234 are conserved in most ciliated organisms. We propose that they constitute a polyglutamylation complex specialized for regulation of ciliary motility.
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Affiliation(s)
- Tomohiro Kubo
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655 Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan Department of Life Science, Faculty of Science, Gakushuin University, Toshima-ku, Tokyo 171-8588, Japan
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Hilton LK, Gunawardane K, Kim JW, Schwarz MC, Quarmby LM. The kinases LF4 and CNK2 control ciliary length by feedback regulation of assembly and disassembly rates. Curr Biol 2013; 23:2208-2214. [PMID: 24184104 DOI: 10.1016/j.cub.2013.09.038] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 09/12/2013] [Accepted: 09/12/2013] [Indexed: 11/29/2022]
Abstract
BACKGROUND Many of the diverse functions of cilia depend upon tight control of their length. Steady-state length reflects a balance between rates of ciliary assembly and disassembly, two parameters likely controlled by a length sensor of unknown identity or mechanism. RESULTS A null mutation in Chlamydomonas CNK2, a member of the evolutionarily conserved family of NIMA-related kinases, reveals feedback regulation of assembly and disassembly rates. cnk2-1 mutant cells have a mild long-flagella (lf) phenotype as a consequence of reduced rates of flagellar disassembly. This is in contrast to the strong lf mutant lf4-7, which exhibits an aberrantly high rate of assembly. Cells carrying both mutations have even longer flagella than lf4-7 single mutants do. In addition to their high rate of assembly, lf4-7 mutants have a CNK2-dependent increase in disassembly rate. Finally, cnk2-1 cells have a decreased rate of turnover of flagellar subunits at the tip of the flagellum, demonstrating that the effects on disassembly are compensated by a reduced rate of assembly. CONCLUSIONS We propose a model wherein CNK2 and LF4 modulate rates of disassembly and assembly respectively in a feedback loop that is activated when flagella exceed optimal length.
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Affiliation(s)
- Laura K Hilton
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Kavisha Gunawardane
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Joo Wan Kim
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Marianne C Schwarz
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Lynne M Quarmby
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
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Kato N, Dong T, Bailey M, Lum T, Ingram D. Triacylglycerol mobilization is suppressed by brefeldin A in Chlamydomonas reinhardtii. PLANT & CELL PHYSIOLOGY 2013; 54:1585-99. [PMID: 23872273 PMCID: PMC4081630 DOI: 10.1093/pcp/pct103] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Brefeldin A suppresses vesicle trafficking by inhibiting exchange of GDP for GTP in ADP-ribosylation factor. We report that brefeldin A suppresses mobilization of triacylglycerols in Chlamydomonas reinhardtii, a model organism of green microalgae. Analyses revealed that brefeldin A causes Chlamydomonas to form lipid droplets in which triacylglycerols accumulate in a dose-dependent manner. Pulse labeling experiment using fluorescent fatty acids suggested that brefeldin A inhibits the cells from degrading fatty acids. The experiment also revealed that the cells transiently form novel compartments that accumulate exogenously added fatty acids in the cytoplasm, designated fatty acid-induced microbodies (FAIMs). Brefeldin A up-regulates the formation of FAIMs, whereas nitrogen deprivation that up-regulates triacylglycerol synthesis in Chlamydomonas does not cause the cells to form FAIMs. These results underscore the role of the vesicle trafficking machinery in triacylglycerol metabolism in green microalgae.
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Affiliation(s)
- Naohiro Kato
- Department of Biological Sciences, Louisiana State University, 226 Life Sciences Building, Baton Rouge, LA 70803, USA
- *Corresponding author: E-mail: ; Fax: +1-225-578-2597
| | - Trung Dong
- Department of Biological Sciences, Louisiana State University, 226 Life Sciences Building, Baton Rouge, LA 70803, USA
| | - Michael Bailey
- Department of Biological Sciences, Louisiana State University, 226 Life Sciences Building, Baton Rouge, LA 70803, USA
| | - Tony Lum
- Department of Biological Sciences, Louisiana State University, 226 Life Sciences Building, Baton Rouge, LA 70803, USA
| | - Drury Ingram
- Cell Biology & Bioimaging Core, Pennington Biomedical Research Center, 6400 Perkins Rd., Baton Rouge, LA 70808, USA
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