251
|
Abstract
Cilia are membrane-bounded, centriole-derived projections from the cell surface that contain a microtubule cytoskeleton, the ciliary axoneme, surrounded by a ciliary membrane. Axonemes in multiciliated cells of mammalian epithelia are 9 + 2, possess dynein arms, and are motile. In contrast, single nonmotile 9 + 0 primary cilia are found on epithelial cells, such as those of the kidney tubule, but also on nonepithelial cells, such as chondrocytes, fibroblasts, and neurons. The ciliary membranes of all cilia contain specific receptors and ion channel proteins that initiate signaling pathways controlling motility and/or linking mechanical or chemical stimuli, including sonic hedgehog and growth factors, to intracellular transduction cascades regulating differentiation, migration, and cell growth during development and in adulthood. Unique motile 9 + 0 cilia, found during development at the embryonic node, determine left-right asymmetry of the body.
Collapse
Affiliation(s)
- Peter Satir
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA.
| | | |
Collapse
|
252
|
Blaineau C, Tessier M, Dubessay P, Tasse L, Crobu L, Pagès M, Bastien P. A novel microtubule-depolymerizing kinesin involved in length control of a eukaryotic flagellum. Curr Biol 2007; 17:778-82. [PMID: 17433682 DOI: 10.1016/j.cub.2007.03.048] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 03/13/2007] [Accepted: 03/14/2007] [Indexed: 11/19/2022]
Abstract
Cilia and flagella are complex, microtubule (MT)-filled cell organelles of which the structure is evolutionarily conserved from protistan cells to mammalian sperm and the size is regulated. The best-established model for flagellar length (FL) control is set by the balance of continuous MT assembly and disassembly occurring at the flagellar tip. Because steady-state assembly of tubulin onto the distal end of the flagellum requires intraflagellar transport (IFT)--a bidirectional movement of large protein complexes that occurs within the flagellum--FL control must rely upon the regulation of IFT. This does not preclude that other pathways might "directly" affect MT assembly and disassembly. Now, among the superfamily of kinesins, family-13 (MCAK/KIF2) members exhibit a MT-depolymerizing activity responsible for their essential functions in mitosis. Here we present a novel family-13 kinesin from the flagellated protozoan parasite Leishmania major, that localizes essentially to the flagellum, and whose overexpression produces flagellar shortening and knockdown yields long flagella. Using negative mutants, we demonstrate that this phenotype is linked with the MT-binding and -depolymerizing activity of this kinesin. This is the first report of an effector protein involved in FL control through a direct action in MT dynamics, thus this finding complements the assembly-disassembly model.
Collapse
Affiliation(s)
- Christine Blaineau
- Laboratoire de Parasitologie-Mycologie, Biologie Moléculaire, Biologie Cellulaire et Biodiversité des Protozoaires Parasites, FRE 3013 Centre National de Recherche Scientifique/Université Montpellier I, Montpellier, France.
| | | | | | | | | | | | | |
Collapse
|
253
|
Burghoorn J, Dekkers MPJ, Rademakers S, de Jong T, Willemsen R, Jansen G. Mutation of the MAP kinase DYF-5 affects docking and undocking of kinesin-2 motors and reduces their speed in the cilia of Caenorhabditis elegans. Proc Natl Acad Sci U S A 2007; 104:7157-62. [PMID: 17420466 PMCID: PMC1855366 DOI: 10.1073/pnas.0606974104] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the cilia of the nematode Caenorhabditis elegans, anterograde intraflagellar transport (IFT) is mediated by two kinesin-2 complexes, kinesin II and OSM-3 kinesin. These complexes function together in the cilia middle segments, whereas OSM-3 alone mediates transport in the distal segments. Not much is known about the mechanisms that compartmentalize the kinesin-2 complexes or how transport by both kinesins is coordinated. Here, we identify DYF-5, a conserved MAP kinase that plays a role in these processes. Fluorescence microscopy and EM revealed that the cilia of dyf-5 loss-of-function (lf) animals are elongated and are not properly aligned into the amphid channel. Some cilia do enter the amphid channel, but the distal ends of these cilia show accumulation of proteins. Consistent with these observations, we found that six IFT proteins accumulate in the cilia of dyf-5(lf) mutants. In addition, using genetic analyses and live imaging to measure the motility of IFT proteins, we show that dyf-5 is required to restrict kinesin II to the cilia middle segments. Finally, we show that, in dyf-5(lf) mutants, OSM-3 moves at a reduced speed and is not attached to IFT particles. We propose that DYF-5 plays a role in the undocking of kinesin II from IFT particles and in the docking of OSM-3 onto IFT particles.
Collapse
Affiliation(s)
- Jan Burghoorn
- *Department of Cell Biology and Genetics and Center for Biomedical Genetics and
| | | | - Suzanne Rademakers
- *Department of Cell Biology and Genetics and Center for Biomedical Genetics and
| | | | - Rob Willemsen
- Clinical Genetics, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands
| | - Gert Jansen
- *Department of Cell Biology and Genetics and Center for Biomedical Genetics and
- To whom correspondence should be addressed at:
Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands. E-mail:
| |
Collapse
|
254
|
Wemmer KA, Marshall WF. Flagellar length control in chlamydomonas--paradigm for organelle size regulation. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 260:175-212. [PMID: 17482906 DOI: 10.1016/s0074-7696(06)60004-1] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A fundamental unsolved question in cell biology is how the cell controls the size of its organelles. Cilia and flagella are an ideal test case to study the mechanism of organelle size control, because their size is easily measured and can be represented by a single number-length. Moreover, the involvement of cilia in many developmental and physiological processes suggests an understanding of their size control system is critical for understanding ciliary diseases, many of which (e.g., autosomal recessive polycystic kidney disease) are known to involve abnormally short cilia. The flagella of the model organism Chlamydomonas reinhardtii provide the best genetic and cell-biological system to study length control of cilia. Studies in this organism using genetics, biochemistry, imaging, and mathematical modeling have revealed many genes involved in length control of cilia and flagella, and have suggested several testable models for length regulation.
Collapse
Affiliation(s)
- Kimberly A Wemmer
- Department of Biochemistry, University of California, San Francisco, California 94158, USA
| | | |
Collapse
|
255
|
Abstract
Cilia are microtubule-based organelles that project like antennae from the surface of most cells in the body. Motile cilia move fluid past cells, for example mucus in the airway. Non-motile primary cilia, however, transduce a multitude of sensory stimuli, including chemical concentrations of growth factors, hormones, odorants, and developmental morphogens, as well as osmolarity, light intensity, and fluid flow. Cilia have evolved a complex ultrastructure to accommodate these diverse functions, and an extensive molecular machinery has developed to support the assembly of these organelles. Defects in the cilia themselves, or the machinery required to assemble them, lead to a broad spectrum of human disease symptoms, including polycystic kidney disease, nephronophthisis, hydrocephalus, polydactyly, situs inversus, retinal degeneration, and obesity. While these diseases highlight the pivotal roles of cilia in physiology and development, the mechanistic link between cilia, physiology, and disease remains unclear.
Collapse
Affiliation(s)
- Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th St., San Francisco, California 94143, USA.
| | | |
Collapse
|
256
|
Abstract
Recently, there has been a surge in the number of pioneering studies combining experiments with quantitative modeling to explain both relatively simple modules of molecular machinery of the cell and to achieve system-level understanding of cellular networks. Here we discuss the utility and methods of modeling and review several current models of cell signaling, cytoskeletal self-organization, nuclear transport, and the cell cycle. We discuss successes of and barriers to modeling in cell biology and its future directions, and we argue, using the field of bacterial chemotaxis as an example, that the closer the complete systematic understanding of cell behavior is, the more important modeling becomes and the more experiment and theory merge.
Collapse
Affiliation(s)
- Alex Mogilner
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, 95616, USA.
| | | | | |
Collapse
|
257
|
Hunter CA, Tomas S. Accurate Length Control of Supramolecular Oligomerization: Vernier Assemblies. J Am Chem Soc 2006; 128:8975-9. [PMID: 16819894 DOI: 10.1021/ja061928f] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Linear oligomeric supramolecular assemblies of defined length have been generated using the Vernier principle. Two molecules, containing a different number (n and m) of mutually complementary binding sites, separated by the same distance, interact with each other to form an assembly of length (n x m). The assembly grows in the same way as simple supramolecular polymers, but at a molecular stop signal, when the binding sites come into register, the assembly terminates giving an oligomer of defined length. This strategy has been realized using tin and zinc porphyrin oligomers as the molecular building blocks. In the presence of isonicotinic acid, a zinc porphyrin trimer and a tin porphyrin dimer form a 3:4 triple stranded Vernier assembly six porphyrins long. The triple strand Vernier architecture introduced here adds an additional level of cooperativity, yielding a stability and selectivity that cannot be achieved via a simple Vernier approach. The assembly properties of the system were characterized using fluorescence titrations and size-exclusion chromatography (SEC). Assembly of the Vernier complex is efficient at micromolar concentrations in nonpolar solvents, and under more competitive conditions, a variety of fragmentation assemblies can be detected, allowing determination of the stability constants for this system and detailed speciation profiles to be constructed.
Collapse
Affiliation(s)
- Christopher A Hunter
- Centre for Chemical Biology, Krebs Institute for Biomolecular Science, Department of Chemistry, University of Sheffield, Sheffield S3 7HF UK.
| | | |
Collapse
|
258
|
Bressloff PC. Stochastic model of intraflagellar transport. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:061916. [PMID: 16906873 DOI: 10.1103/physreve.73.061916] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Revised: 05/15/2006] [Indexed: 05/11/2023]
Abstract
We present a stochastic model of filament growth driven by the motor-assisted transport of particles along the filament. We show how the growth can be analyzed in terms of a sequence of first passage times for a particle hopping between the two ends of the filament, and use this to calculate the mean and variance of the length as a function of time. We determine how the growth depends on the waiting time density of the underlying hopping process, and highlight differences in the growth generated by normal and anomalous transport, for which the mean waiting time is finite and infinite, respectively. In the case of normal transport, we determine the length at which there is a balance between particle-driven assembly and particle-independent disassembly of the filament. The existence of such a balance point is thought to provide a mechanism for flagellar length control.
Collapse
Affiliation(s)
- Paul C Bressloff
- Department of Mathematics, University of Utah, Salt Lake City, Utah 84112, USA
| |
Collapse
|
259
|
Pedersen LB, Geimer S, Rosenbaum JL. Dissecting the molecular mechanisms of intraflagellar transport in chlamydomonas. Curr Biol 2006; 16:450-9. [PMID: 16527740 DOI: 10.1016/j.cub.2006.02.020] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 01/04/2006] [Accepted: 01/19/2006] [Indexed: 10/24/2022]
Abstract
BACKGROUND The assembly and maintenance of eukaryotic cilia and flagella are mediated by intraflagellar transport (IFT), a bidirectional microtubule (MT)-based transport system. The IFT system consists of anterograde (kinesin-2) and retrograde (cDynein1b) motor complexes and IFT particles comprising two complexes, A and B. In the current model for IFT, kinesin-2 carries cDynein1b, IFT particles, and axonemal precursors from the flagellar base to the tip, and cDynein1b transports kinesin-2, IFT particles, and axonemal turnover products from the tip back to the base. Most of the components of the IFT system have been identified and characterized, but the mechanisms by which these different components are coordinated and regulated at the flagellar base and tip are unclear. RESULTS Using a variety of Chlamydomonas mutants, we confirm that cDynein1b requires kinesin-2 for transport toward the tip and show that during retrograde IFT, kinesin-2 can exit the flagella independent of the cDynein1b light intermediate chain (LIC) and IFT particles. Furthermore, using biochemical approaches, we find that IFT complex B can associate with cDynein1b independent of complex A and cDynein1b LIC. Finally, using electron microscopy, we show that the IFT tip turnaround point most likely is localized distal to the plus end of the outer-doublet B MTs. CONCLUSION Our results support a model for IFT in which tip turnaround involves (1) dissociation of IFT complexes A and B and release of inactive cDynein1b from complex B, (2) binding of complex A to active cDynein1b, and (3) reassociation of complex B with A prior to retrograde IFT.
Collapse
Affiliation(s)
- Lotte B Pedersen
- Institute of Molecular Biology and Physiology, University of Copenhagen, DK-2100 Copenhagen, Denmark.
| | | | | |
Collapse
|
260
|
Wloga D, Camba A, Rogowski K, Manning G, Jerka-Dziadosz M, Gaertig J. Members of the NIMA-related kinase family promote disassembly of cilia by multiple mechanisms. Mol Biol Cell 2006; 17:2799-810. [PMID: 16611747 PMCID: PMC1474788 DOI: 10.1091/mbc.e05-05-0450] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The genome of Tetrahymena thermophila contains 39 loci encoding NIMA-related kinases (NRKs), an extraordinarily large number for a unicellular organism. Evolutionary analyses grouped these sequences into several subfamilies, some of which have orthologues in animals, whereas others are protist specific. When overproduced, NRKs of three subfamilies caused rapid shortening of cilia. Ultrastructural studies revealed that each NRK triggered ciliary resorption by a distinct mechanism that involved preferential depolymerization of a subset of axonemal microtubules, at either the distal or proximal end. Overexpression of a kinase-inactive variant caused lengthening of cilia, indicating that constitutive NRK-mediated resorption regulates the length of cilia. Each NRK preferentially resorbed a distinct subset of cilia, depending on the location along the anteroposterior axis. We also show that normal Tetrahymena cells maintain unequal length cilia. We propose that ciliates used a large number of NRK paralogues to differentially regulate the length of specific subsets of cilia in the same cell.
Collapse
Affiliation(s)
- Dorota Wloga
- *Department of Cellular Biology, University of Georgia, Athens, GA 30602-2607
| | - Amy Camba
- *Department of Cellular Biology, University of Georgia, Athens, GA 30602-2607
| | - Krzysztof Rogowski
- *Department of Cellular Biology, University of Georgia, Athens, GA 30602-2607
| | - Gerard Manning
- Razavi-Newman Center for Bioinformatics, Salk Institute for Biological Studies, La Jolla, CA 92037; and
| | - Maria Jerka-Dziadosz
- Department of Cell Biology, M. Nencki Institute of Experimental Biology, Polish Academy of Science, 02-093 Warsaw, Poland
| | - Jacek Gaertig
- *Department of Cellular Biology, University of Georgia, Athens, GA 30602-2607
| |
Collapse
|
261
|
Jékely G, Arendt D. Evolution of intraflagellar transport from coated vesicles and autogenous origin of the eukaryotic cilium. Bioessays 2006; 28:191-8. [PMID: 16435301 DOI: 10.1002/bies.20369] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The cilium/flagellum is a sensory-motile organelle ancestrally present in eukaryotic cells. For assembly cilia universally rely on intraflagellar transport (IFT), a specialised bidirectional transport process mediated by the ancestral and conserved IFT complex. Based on the homology of IFT complex proteins to components of coat protein I (COPI) and clathrin-coated vesicles, we propose that the non- vesicular, membrane-bound IFT evolved as a specialised form of coated vesicle transport from a protocoatomer complex. IFT thus shares common ancestry with all protocoatomer derivatives, including all vesicle coats and the nuclear pore complex (NPC). This has major implications for the evolutionary origin of the cilium. First, it reinforces the tenet that duplication and divergence of pre-existing structures, rather than symbiosis, were the major themes during cilium evolution. Second, it suggests that the initial step in the autogenous origin of the cilium was the establishment of a membrane patch with transmembrane proteins transported by the ancestral vesicle-coating IFT complex. We propose a scenario for how the initial membrane patch gradually protruded to enhance exposure to the environment, then started to move, and finally compartmentalised to render receptor signalling and ciliary beating more efficient.
Collapse
Affiliation(s)
- Gáspár Jékely
- European Molecular Biology Laboratory, Heidelberg, Germany.
| | | |
Collapse
|
262
|
Erdmann M, Scholz A, Melzer IM, Schmetz C, Wiese M. Interacting protein kinases involved in the regulation of flagellar length. Mol Biol Cell 2006; 17:2035-45. [PMID: 16467378 PMCID: PMC1415332 DOI: 10.1091/mbc.e05-10-0976] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
A striking difference of the life stages of the protozoan parasite Leishmania is a long flagellum in the insect stage promastigotes and a rudimentary organelle in the mammalian amastigotes. LmxMKK, a mitogen-activated protein (MAP) kinase kinase from Leishmania mexicana, is required for growth of a full-length flagellum. We identified LmxMPK3, a MAP kinase homologue, with a similar expression pattern as LmxMKK being not detectable in amastigotes, up-regulated during the differentiation to promastigotes, constantly expressed in promastigotes, and shut down during the differentiation to amastigotes. LmxMPK3 null mutants resemble the LmxMKK knockouts with flagella reduced to one-fifth of the wild-type length, stumpy cell bodies, and vesicles and membrane fragments in the flagellar pocket. A constitutively activated recombinant LmxMKK activates LmxMPK3 in vitro. Moreover, LmxMKK is likely to be directly involved in the phosphorylation of LmxMPK3 in vivo. Finally, LmxMPK3 is able to phosphorylate LmxMKK, indicating a possible feedback regulation. This is the first time that two interacting components of a signaling cascade have been described in the genus Leishmania. Moreover, we set the stage for the analysis of reversible phosphorylation in flagellar morphogenesis.
Collapse
Affiliation(s)
- Maja Erdmann
- Bernhard Nocht Institute for Tropical Medicine, Parasitology Section, D-20359 Hamburg, Germany
| | | | | | | | | |
Collapse
|
263
|
Davenport JR, Yoder BK. An incredible decade for the primary cilium: a look at a once-forgotten organelle. Am J Physiol Renal Physiol 2005; 289:F1159-69. [PMID: 16275743 DOI: 10.1152/ajprenal.00118.2005] [Citation(s) in RCA: 229] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Since the discovery that numerous proteins involved in mammalian disease localize to the basal bodies and cilia, these organelles have emerged from relative obscurity to the center of intense research efforts in an expanding number of disease- and developmental-related fields. Our understanding of the association between cilia and human disease has benefited substantially from the use of lower organisms such as Chlamydomonas and Caenorhabditis elegans and the availability of murine models and cell culture. These research endeavors led to the discovery that loss of normal ciliary function in mammals is responsible for cystic and noncystic pathology in the kidney, liver, brain, and pancreas, as well as severe developmental patterning abnormalities. In addition, the localization of proteins involved in rare human disorders such as Bardet-Biedl syndrome has suggested that cilia-related dysfunction may play a role in modern human epidemics such as hypertension, obesity, and diabetes. Although we have made great advances in demonstrating the importance of cilia over the past decade, the physiological role that this organelle plays in most tissues remains elusive. Research focused on addressing this issue will be of critical importance for a further understanding of how ciliary dysfunction can lead to such severe disease and developmental pathologies.
Collapse
Affiliation(s)
- James R Davenport
- Department of Cell Biology, University of Alabama at Birmingham, 35294, USA
| | | |
Collapse
|
264
|
Pan J, Snell WJ. Chlamydomonas shortens its flagella by activating axonemal disassembly, stimulating IFT particle trafficking, and blocking anterograde cargo loading. Dev Cell 2005; 9:431-8. [PMID: 16139231 DOI: 10.1016/j.devcel.2005.07.010] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Revised: 06/23/2005] [Accepted: 07/27/2005] [Indexed: 10/25/2022]
Abstract
Almost all eukaryotic cells form cilia/flagella, maintain them at their genetically specified lengths, and shorten them. Here, we define the cellular mechanisms that bring about shortening of flagella prior to meiotic cell division and in response to environmental cues in the biflagellated green alga Chlamydomonas. We show that the flagellar shortening pathway is distinct from the one that enforces transient shortening essential for length control. During flagellar shortening, disassembly of the axoneme is stimulated over the basal rate, and the rate of entry into flagella of intraflagellar transport (IFT) particles is increased. Moreover, the particles entering the disassembling flagella lack cargo. Thus, flagellar shortening depends on the interplay between dynamic properties of the axoneme and the IFT machinery; a cell triggered to shorten its flagellum activates disassembly of the axoneme and stimulates entry into the flagellum of IFT particles possessing empty cargo binding sites available to retrieve the disassembled components.
Collapse
Affiliation(s)
- Junmin Pan
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, 75390, USA
| | | |
Collapse
|
265
|
Oliveira DM, Gouveia JJS, Diniz NB, Pacheco ACL, Vasconcelos EJR, Diniz MC, Viana DA, Ferreira TD, Albuquerque MC, Fortier DC, Maia ARS, Costa LAC, Melo JOP, da Silva MC, Walter CA, Faria JO, Tome AR, Gomes MJN, Oliveira SMP, Araújo-Filho R, Costa RB, Maggioni R. Pathogenomics analysis of Leishmania spp.: flagellar gene families of putative virulence factors. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2005; 9:173-93. [PMID: 15969649 DOI: 10.1089/omi.2005.9.173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The trypanosomatid flagellar apparatus contains conventional and unique features, whose roles in infectivity are still enigmatic. Although the flagellum and the flagellar pocket are critical organelles responsible for all vesicular trafficking between the cytoplasm and cell surface, still very little is known about their roles in pathogenesis and how molecules get to and from the flagellar pocket. The ongoing analysis of the genome sequences and proteome profiles of Leishmania major and L infantum, Trypanosoma cruzi, T. brucei, and T. gambiensi ( www.genedb.org ), coupled with our own work on L. chagasi (as part of the Brazilian Northeast Genome Program- www.progene.ufpe.br ), prompted us to scrutinize flagellar genes and proteins of Leishmania spp. promastigotes that could be virulence factors in leishmaniasis. We have identified some overlooked parasite factors such as the MNUDC-1 (a protein involved in nuclear development and genomic fusion) and SQS (an enzyme of sterol biosynthesis), among the described flagellar gene families. A database concerning the results of this work, as well as of other studies of Leishmania and its organelles, is available at http://nugen.lcc.uece.br/LPGate . It will serve as a convenient bioinformatics resource on genomics and pathology of the etiological agents of leishmaniasis.
Collapse
Affiliation(s)
- Diana M Oliveira
- Núcleo de Genômica e Bioinformática, Faculdade de Veterinária, Universidade Estadual do Ceara (UECE), Campus do Itaperi, Fortaleza, Ceara, Brazil.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
266
|
Bradley BA, Quarmby LM. A NIMA-related kinase, Cnk2p, regulates both flagellar length and cell size in Chlamydomonas. J Cell Sci 2005; 118:3317-26. [PMID: 16030138 DOI: 10.1242/jcs.02455] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The cycle of ciliogenesis and ciliary disassembly is coordinated with cell division. In the unicellular alga Chlamydomonas, the two flagella are maintained at constant and equal length during interphase, and are reabsorbed prior to mitosis. We report that the NIMA-related kinase, Cnk2p, is an axonemal protein that affects flagellar length via effects on disassembly rate and also plays a role in the cellular assessment of size prior to committing to mitosis. This is the second NIMA-related kinase shown to affect ciliary function and cell cycle progression in Chlamydomonas. We speculate that members of the NIMA family have evolved nuanced roles to coordinate cilia/cell cycle regulation.
Collapse
Affiliation(s)
- Brian A Bradley
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | | |
Collapse
|
267
|
Bengs F, Scholz A, Kuhn D, Wiese M. LmxMPK9, a mitogen-activated protein kinase homologue affects flagellar length in Leishmania mexicana. Mol Microbiol 2005; 55:1606-15. [PMID: 15720564 DOI: 10.1111/j.1365-2958.2005.04498.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Components of mitogen-activated signal transduction pathways have been shown to be involved in flagellum biogenesis and maintenance. A mitogen-activated protein kinase homologue, designated LmxMPK9 from Leishmania mexicana, has been recently identified in a homology screen and its mRNA found to be present in all life stages. Three different splice-addition sites were used for mRNA maturation in trans-splicing in the different life stages. However, here we show that LmxMPK9 protein is exclusively found in the promastigote stage. Recombinant expression of LmxMPK9 in Escherichia coli and kinase assays revealed a temperature optimum at 27 degrees C, the optimal growth temperature for L. mexicana promastigotes, and a preference for manganese to promote substrate phosphorylation of myelin basic protein. A deletion mutant for the single-copy gene revealed significantly elongated flagella, whereas overexpression led to a subpopulation with rather short to no flagella suggesting a role for LmxMPK9 in flagellar morphogenesis.
Collapse
Affiliation(s)
- Florian Bengs
- Bernhard Nocht Institute for Tropical Medicine, Parasitology Section, Bernhard-Nocht-Strasse 74, D-20359 Hamburg, Germany
| | | | | | | |
Collapse
|
268
|
Abstract
Intraflagellar transport (IFT) is the term that refers to the microtubule dependent particle motility that is common to almost all flagella and cilia and is distinct from the mechanism of flagellar beating. IFT involves the rapid, bi-directional transport of molecular motors and their cargo proteins from the base to the tip of the flagellum and back again. While the basic mechanism of IFT is well established, the varied functions of this process are continually being elucidated. For example, although IFT plays a clear role in flagellar assembly, disassembly and stability, the exact sequence of events that take place when tubulin subunit addition and loss occur during flagellar assembly and disassembly, respectively, are unknown. Key to furthering our understanding of IFT is greater knowledge of the flagellar tip complex (FTC) because it is at the FTC that flagellar assembly and disassembly, cargo loading and unloading, and motor protein regulation occur. Yet these related processes may only represent one aspect of the importance of IFT in flagellar dynamics. IFT may also provide the basic elements of a signal transduction mechanism that functions to provide the nucleus with information about the outside environment and even about the state of the flagellum itself. Thus, IFT may function as the central component of a signal transduction system that controls flagellar gene transcription.
Collapse
Affiliation(s)
- Roger D Sloboda
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
| |
Collapse
|
269
|
Abstract
Biologists have long known that humans experience their environment through cilia. Light, odorant, and sound perception depend on these microtubule-filled, complex organelles present on cells in primary sensory tissues. Recently, discoveries on the mechanism of assembly of cilia (flagella) in the lowly, biflagellated, eucaryotic green alga Chlamydomonas have triggered a renaissance of interest in the organelles along with a recognition of their key sensory roles in nonsensory tissues. Chlamydomonas researchers uncovered an entirely new set of cellular machinery essential for transporting the protein components of cilia and flagella in all ciliated/flagellated eukaryotic cells between their site of synthesis in the cell body and their site of assembly at the tip of the flagellum (intraflagellar transport: IFT). Prompted by the surprising observations that disruption of IFT genes in mice led to polycystic kidney disease (PKD) and that PKD proteins are present on the sensory cilia of Caenorhabditis elegans, researchers have made a direct connection between PKD and cilia. At least five (and possibly all) of the seven identified human genes disrupted in PKD and a related disorder nephronophthisis encode proteins expressed in the primary cilia that project into the lumen from the epithelial cells that line renal tubules. Moreover, the renal cilia are flow sensors and at least two of the PKD genes encode ciliary transmembrane proteins essential for mechanosensation. Although their roles have not yet been as clearly identified, cilia also are at the center of a rare human disorder, Bardet-Biedl syndrome (BBS), in which patients exhibit phenotypes of common human diseases, including obesity and increased incidence of hypertension and diabetes. Five of the eight known BBS genes encode basal body or cilia proteins in mice or humans, and homologues of two of the remaining genes are present in basal bodies/cilia of model organisms. Here we briefly describe the biology of cilia and flagella, we outline how studies on model organisms have led to our current understanding of the roles of these organelles and their proteins in health and disease, and we highlight the notion that the primary cilia present on cells throughout the body, even those on brain neurons, may be essential for as yet undiscovered cilium-generated signaling functions.
Collapse
Affiliation(s)
- Junmin Pan
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX 75390-9036, USA
| | | | | |
Collapse
|
270
|
Liu Q, Zuo J, Pierce EA. The retinitis pigmentosa 1 protein is a photoreceptor microtubule-associated protein. J Neurosci 2005; 24:6427-36. [PMID: 15269252 PMCID: PMC1904502 DOI: 10.1523/jneurosci.1335-04.2004] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The outer segments of rod and cone photoreceptor cells are highly specialized sensory cilia made up of hundreds of membrane discs stacked into an orderly array along the photoreceptor axoneme. It is not known how the alignment of the outer segment discs is controlled, although it has been suggested that the axoneme may play a role in this process. Mutations in the retinitis pigmentosa 1 (RP1) gene are a common cause of retinitis pigmentosa (RP). Disruption of the Rp1 gene in mice causes misorientation of outer segment discs, suggesting a role for RP1 in outer segment organization. Here, we show that the RP1 protein is part of the photoreceptor axoneme. Amino acids 28-228 of RP1, which share limited homology with the microtubule-binding domains of the neuronal microtubule-associated protein (MAP) doublecortin, mediate the interaction between RP1 and microtubules, indicating that the putative doublecortin (DCX) domains in RP1 are functional. The N-terminal portion of RP1 stimulates the formation of microtubules in vitro and stabilizes cytoplasmic microtubules in heterologous cells. Evaluation of photoreceptor axonemes from mice with targeted disruptions of the Rp1 gene shows that Rp1 proteins that contain the DCX domains also help control axoneme length and stability in vivo. These results demonstrate that RP1 is a MAP. Given the specific expression of RP1 in photoreceptors, RP1 is thus the first photoreceptor-specific MAP to be identified. Furthermore, these findings indicate that the RP1 form of inherited retinal degeneration is part of the larger class of neurodegenerative diseases caused by MAP dysfunction.
Collapse
Affiliation(s)
- Qin Liu
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | | | | |
Collapse
|
271
|
Wilson NF, Lefebvre PA. Regulation of flagellar assembly by glycogen synthase kinase 3 in Chlamydomonas reinhardtii. EUKARYOTIC CELL 2005; 3:1307-19. [PMID: 15470259 PMCID: PMC522593 DOI: 10.1128/ec.3.5.1307-1319.2004] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Chlamydomonas reinhardtii controls flagellar assembly such that flagella are of an equal and predetermined length. Previous studies demonstrated that lithium, an inhibitor of glycogen synthase kinase 3 (GSK3), induced flagellar elongation, suggesting that a lithium-sensitive signal transduction pathway regulated flagellar length (S. Nakamura, H. Takino, and M. K. Kojima, Cell Struct. Funct. 12:369-374, 1987). Here, we demonstrate that lithium treatment depletes the pool of flagellar proteins from the cell body and that the heterotrimeric kinesin Fla10p accumulates in flagella. We identify GSK3 in Chlamydomonas and demonstrate that its kinase activity is inhibited by lithium in vitro. The tyrosine-phosphorylated, active form of GSK3 was enriched in flagella and GSK3 associated with the axoneme in a phosphorylation-dependent manner. The level of active GSK3 correlated with flagellar length; early during flagellar regeneration, active GSK3 increased over basal levels. This increase in active GSK3 was rapidly lost within 30 min of regeneration as the level of active GSK3 decreased relative to the predeflagellation level. Taken together, these results suggest a possible role for GSK3 in regulating the assembly and length of flagella.
Collapse
Affiliation(s)
- Nedra F Wilson
- Department of Plant Biology, University of Minnesota, 250 Biological Sciences Center, 1445 Gortner Ave., St. Paul, MN 55108, USA.
| | | |
Collapse
|
272
|
Mitchell KAP, Gallagher BC, Szabo G, Otero ADS. NDP kinase moves into developing primary cilia. ACTA ACUST UNITED AC 2005; 59:62-73. [PMID: 15259056 DOI: 10.1002/cm.20025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Inmunofluorescence staining of murine NIH3T3 fibroblasts grown at high density shows that conventional nucleoside diphosphate (NDP) kinases A and B localize to a sensory organelle, the primary cilium. Similar results are obtained with Xenopus A6 kidney epithelial cells, suggesting that NDP kinases are a universal component of the primary cilium. The translocation of NDP kinase into primary cilia depends on size, taking place only when cilia reach a critical length of 5-6 microm. In mature cilia, NDP kinases are distributed along the ciliary shaft in a punctate pattern that is distinct from the continuous staining observed with acetylated alpha-tubulin, a ciliary marker and axonemal component. Isolation of a fraction enriched in primary cilia from A6 cells led to the finding that ciliary NDP kinase is enzymatically active, and is associated with the membrane and the matrix, but not the axoneme. In contrast, acetylated alpha-tubulin is found in the axoneme and, to a lesser extent, in the membrane. Based on the tightly regulated translocation process and the subciliary distribution pattern of NDP kinase, we propose that it plays a role in the elongation and maintenance of primary cilia by its ability to regenerate the GTP utilized by ciliary microtubule turnover and transmembrane signaling.
Collapse
Affiliation(s)
- Kimberly A P Mitchell
- Department of Molecular Physiology and Biological Physics, University of Virginia Medical School, Charlottesville, VA 22908-0736, USA
| | | | | | | |
Collapse
|
273
|
Stolc V, Samanta MP, Tongprasit W, Marshall WF. Genome-wide transcriptional analysis of flagellar regeneration in Chlamydomonas reinhardtii identifies orthologs of ciliary disease genes. Proc Natl Acad Sci U S A 2005; 102:3703-7. [PMID: 15738400 PMCID: PMC553310 DOI: 10.1073/pnas.0408358102] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The important role that cilia and flagella play in human disease creates an urgent need to identify genes involved in ciliary assembly and function. The strong and specific induction of flagellar-coding genes during flagellar regeneration in Chlamydomonas reinhardtii suggests that transcriptional profiling of such cells would reveal new flagella-related genes. We have conducted a genome-wide analysis of RNA transcript levels during flagellar regeneration in Chlamydomonas by using maskless photolithography method-produced DNA oligonucleotide microarrays with unique probe sequences for all exons of the 19,803 predicted genes. This analysis represents previously uncharacterized whole-genome transcriptional activity profiling study in this important model organism. Analysis of strongly induced genes reveals a large set of known flagellar components and also identifies a number of important disease-related proteins as being involved with cilia and flagella, including the zebrafish polycystic kidney genes Qilin, Reptin, and Pontin, as well as the testis-expressed tubby-like protein TULP2.
Collapse
Affiliation(s)
- Viktor Stolc
- Genome Research Facility, National Aeronautic and Space Administration, Ames Research Center, Moffett Field, CA 94035, USA.
| | | | | | | |
Collapse
|
274
|
Abstract
The problem of organelle size control can be addressed most simply by considering cellular structures that are linear, so that their size can be defined by a single parameter: length. We compare existing studies on several linear biological structures including prokaryotic flagella and flagellar hooks, eukaryotic flagella, sarcomere thin filaments, and microvilli. In some cases, existing evidence strongly supports the idea that length control involves a molecular ruler, in which the size of the overall structure is compared with the size of an individual molecule. In other cases, length control is likely to involve a steady-state balance of assembly and disassembly, in which one or the other rate is inherently length dependent. The lessons learned from size control in linear structures should be applicable to organelles with more complex three-dimensional structures.
Collapse
Affiliation(s)
- Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California-San Francisco, San Francisco, CA 94143, USA.
| |
Collapse
|
275
|
Abstract
Eukaryotic cilia and flagella are cytoskeletal organelles that are remarkably conserved from protists to mammals. Their basic unit is the axoneme, a well-defined cylindrical structure composed of microtubules and up to 250 associated proteins. These complex organelles are assembled by a dynamic process called intraflagellar transport. Flagella and cilia perform diverse motility and sensitivity functions in many different organisms. Trypanosomes are flagellated protozoa, responsible for various tropical diseases such as sleeping sickness and Chagas disease. In this review, we first describe general knowledge on the flagellum: its occurrence in the living world, its molecular composition, and its mode of assembly, with special emphasis on the exciting developments that followed the discovery of intraflagellar transport. We then present recent progress regarding the characteristics of the trypanosome flagellum, highlighting the original contributions brought by this organism. The most striking phenomenon is the involvement of the flagellum in several aspects of the trypanosome cell cycle, including cell morphogenesis, basal body migration, and cytokinesis.
Collapse
Affiliation(s)
- Linda Kohl
- INSERM U565, CNRS UMR5153, and MNHN USM 0503, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | | |
Collapse
|
276
|
Abstract
Eukaryotic flagella produce a swimming force by coordinating thousands of dynein motor proteins. Recent work provides new clues into how this coordination is achieved.
Collapse
Affiliation(s)
- Kimberly A Wemmer
- Department of Biochemistry and Biophysics, University of California, San Francisco, 600 16th Street, San Francisco, California 94143, USA
| | | |
Collapse
|
277
|
Yang C, Compton MM, Yang P. Dimeric novel HSP40 is incorporated into the radial spoke complex during the assembly process in flagella. Mol Biol Cell 2004; 16:637-48. [PMID: 15563613 PMCID: PMC545900 DOI: 10.1091/mbc.e04-09-0787] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The radial spoke is a stable structural complex in the 9 + 2 axoneme for the control of flagellar motility. However, the spokes in Chlamydomonas mutant pf24 are heterogeneous and unstable, whereas several spoke proteins are reduced differentially. To elucidate the defective mechanism, we clone RSP16, a prominent spoke protein diminished in pf24 axonemes. Unexpectedly, RSP16 is a novel HSP40 member of the DnaJ superfamily that assists chaperones in various protein-folding-related processes. Importantly, RSP16 is uniquely excluded from the 12S spoke precursor complex that is packaged in the cell body and transported toward the flagellar tip to be converted into mature 20S axonemal spokes. Rather, RSP16, transported separately, joins the precursor complex in flagella. Furthermore, RSP16 molecules in vitro and in flagella form homodimers, a characteristic required for the cochaperone activity of HSP40. We postulate that the spoke HSP40 operates as a cochaperone to assist chaperone machinery at the flagellar tip to actively convert the smaller spoke precursor and itself into the mature stable complex; failure of the interaction between the spoke HSP40 and its target polypeptide results in heterogeneous unstable radial spokes in pf24.
Collapse
Affiliation(s)
- Chun Yang
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA
| | | | | |
Collapse
|
278
|
Marshall WF, Qin H, Rodrigo Brenni M, Rosenbaum JL. Flagellar length control system: testing a simple model based on intraflagellar transport and turnover. Mol Biol Cell 2004; 16:270-8. [PMID: 15496456 PMCID: PMC539171 DOI: 10.1091/mbc.e04-07-0586] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Flagellar length regulation provides a simple model system for addressing the general problem of organelle size control. Based on a systems-level analysis of flagellar dynamics, we have proposed a mechanism for flagellar length control in which length is set by the balance of continuous flagellar assembly and disassembly. The model proposes that the assembly rate is length dependent due to the inherent length dependence of intraflagellar transport, whereas disassembly is length independent, such that the two rates can only reach a balance point at a single length. In this report, we test this theoretical model by using three different measurements: 1) the quantity of intraflagellar transport machinery as a function of length, 2) the variation of flagellar length as a function of flagellar number, and 3) the rate of flagellar growth as a function of length. We find that the quantity of intraflagellar transport machinery is independent of length, that flagellar length is a decreasing function of flagellar number, and that flagellar growth rate in regenerating flagella depends on length and not on the time since regeneration began. These results are consistent with the balance-point model for length control. The three strategies used here are not limited to flagella and can in principle be adapted to probe size control systems for any organelle.
Collapse
Affiliation(s)
- Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA.
| | | | | | | |
Collapse
|
279
|
Redeker V, Levilliers N, Vinolo E, Rossier J, Jaillard D, Burnette D, Gaertig J, Bré MH. Mutations of tubulin glycylation sites reveal cross-talk between the C termini of alpha- and beta-tubulin and affect the ciliary matrix in Tetrahymena. J Biol Chem 2004; 280:596-606. [PMID: 15492004 DOI: 10.1074/jbc.m408324200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two types of polymeric post-translational modifications of alpha/beta-tubulin, glycylation and glutamylation, occur widely in cilia and flagella. Their respective cellular functions are poorly understood. Mass spectrometry and immunoblotting showed that two closely related species, the ciliates Tetrahymena and Paramecium, have dramatically different compositions of tubulin post-translational modifications in structurally identical axonemes. Whereas the axonemal tubulin of Paramecium is highly glycylated and has a very low glutamylation content, the axonemal tubulin of Tetrahymena is glycylated and extensively glutamylated. In addition, only the alpha-tubulin of Tetrahymena undergoes detyrosination. Mutations of the known glycylation sites in Tetrahymena tubulin affected the level of each polymeric modification type in both the mutated and nonmutated subunits, revealing cross-talk between alpha- and beta-tubulin. Ultrastructural analyses of glycylation site mutants uncovered defects in the doublet B-subfiber of axonemes and revealed an accumulation of dense material in the ciliary matrix, reminiscent of intraflagellar transport particles seen by others in Chlamydomonas. We propose that polyglycylation and/or polyglutamylation stabilize the B-subfiber of outer doublets and regulate the intraflagellar transport.
Collapse
Affiliation(s)
- Virginie Redeker
- Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, Laboratoire de Neurobiologie, UMR 7637 CNRS, 10 rue Vauquelin, 75005 Paris, France
| | | | | | | | | | | | | | | |
Collapse
|
280
|
Nguyen RL, Tam LW, Lefebvre PA. The LF1 gene of Chlamydomonas reinhardtii encodes a novel protein required for flagellar length control. Genetics 2004; 169:1415-24. [PMID: 15489537 PMCID: PMC1449559 DOI: 10.1534/genetics.104.027615] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Flagellar length is tightly regulated in the biflagellate alga Chlamydomonas reinhardtii. Several genes required for control of flagellar length have been identified, including LF1, a gene required to assemble normal-length flagella. The lf1 mutation causes cells to assemble extra-long flagella and to regenerate flagella very slowly after amputation. Here we describe the positional cloning and molecular characterization of the LF1 gene using a bacterial artificial chromosome (BAC) library. LF1 encodes a protein of 804 amino acids with no obvious sequence homologs in other organisms. The single LF1 mutant allele is caused by a transversion that produces an amber stop at codon 87. Rescue of the lf1 phenotype upon transformation was obtained with clones containing the complete LF1 gene as well as clones that lack the last two exons of the gene, indicating that only the amino-terminal portion of the LF1 gene product (LF1p) is required for function. Although LF1 helps regulate flagellar length, the LF1p localizes almost exclusively in the cell body, with <1% of total cellular LF1p localizing to the flagella.
Collapse
Affiliation(s)
- Rachel L Nguyen
- Department of Plant Biology, University of Minnesota, Saint Paul, 55108, USA
| | | | | |
Collapse
|
281
|
Hou Y, Pazour GJ, Witman GB. A dynein light intermediate chain, D1bLIC, is required for retrograde intraflagellar transport. Mol Biol Cell 2004; 15:4382-94. [PMID: 15269286 PMCID: PMC519134 DOI: 10.1091/mbc.e04-05-0377] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2004] [Revised: 07/09/2004] [Accepted: 07/12/2004] [Indexed: 11/11/2022] Open
Abstract
Intraflagellar transport (IFT), the bidirectional movement of particles along flagella, is essential for flagellar assembly. The motor for retrograde IFT in Chlamydomonas is cytoplasmic dynein 1b, which contains the dynein heavy chain DHC1b and the light intermediate chain (LIC) D1bLIC. To investigate a possible role for the LIC in IFT, we identified a d1blic mutant. DHC1b is reduced in the mutant, indicating that D1bLIC is important for stabilizing dynein 1b. The mutant has variable length flagella that accumulate IFT-particle proteins, indicative of a defect in retrograde IFT. Interestingly, the remaining DHC1b is normally distributed in the mutant flagella, strongly suggesting that the defect is in binding of cargo to the retrograde motor rather than in motor activity per se. Cell growth and Golgi apparatus localization and morphology are normal in the mutant, indicating that D1bLIC is involved mainly in retrograde IFT. Like mammalian LICs, D1bLIC has a phosphate-binding domain (P-loop) at its N-terminus. To investigate the function of this conserved domain, d1blic mutant cells were transformed with constructs designed to express D1bLIC proteins with mutated P-loops. The constructs rescued the mutant cells to a wild-type phenotype, indicating that the function of D1bLIC in IFT is independent of its P-loop.
Collapse
Affiliation(s)
- Yuqing Hou
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, MA 01655,USA
| | | | | |
Collapse
|
282
|
Tull D, Vince JE, Callaghan JM, Naderer T, Spurck T, McFadden GI, Currie G, Ferguson K, Bacic A, McConville MJ. SMP-1, a member of a new family of small myristoylated proteins in kinetoplastid parasites, is targeted to the flagellum membrane in Leishmania. Mol Biol Cell 2004; 15:4775-86. [PMID: 15342784 PMCID: PMC524726 DOI: 10.1091/mbc.e04-06-0457] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mechanisms by which proteins are targeted to the membrane of eukaryotic flagella and cilia are largely uncharacterized. We have identified a new family of small myristoylated proteins (SMPs) that are present in Leishmania spp and related trypanosomatid parasites. One of these proteins, termed SMP-1, is targeted to the Leishmania flagellum. SMP-1 is myristoylated and palmitoylated in vivo, and mutation of Gly-2 and Cys-3 residues showed that both fatty acids are required for flagellar localization. SMP-1 is associated with detergent-resistant membranes based on its recovery in the buoyant fraction after Triton X-100 extraction and sucrose density centrifugation and coextraction with the major surface glycolipids in Triton X-114. However, the flagellar localization of SMP-1 was not affected when sterol biosynthesis and the properties of detergent-resistant membranes were perturbed with ketoconazole. Remarkably, treatment of Leishmania with ketoconazole and myriocin (an inhibitor of sphingolipid biosynthesis) also had no affect on SMP-1 localization, despite causing the massive distension of the flagellum membrane and the partial or complete loss of internal axoneme and paraflagellar rod structures, respectively. These data suggest that flagellar membrane targeting of SMP-1 is not dependent on axonemal structures and that alterations in flagellar membrane lipid composition disrupt axoneme extension.
Collapse
Affiliation(s)
- Dedreia Tull
- Department of Biochemistry and Molecular Biology, University of Melbourne, Royal Parade, Parkville, Victoria 3010, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
283
|
Thazhath R, Jerka-Dziadosz M, Duan J, Wloga D, Gorovsky MA, Frankel J, Gaertig J. Cell context-specific effects of the beta-tubulin glycylation domain on assembly and size of microtubular organelles. Mol Biol Cell 2004; 15:4136-47. [PMID: 15254268 PMCID: PMC515347 DOI: 10.1091/mbc.e04-03-0247] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Tubulin glycylation is a posttranslational modification found in cells with cilia or flagella. The ciliate Tetrahymena has glycylation on ciliary and cortical microtubules. We showed previously that mutating three glycylation sites on beta-tubulin produces immotile 9 + 0 axonemes and inhibits cytokinesis. Here, we use an inducible glycylation domain mutation and epitope tagging to evaluate the potential of glycylation-deficient tubulin for assembly and maintenance of microtubular systems. In axonemes, the major defects, including lack of the central pair, occurred during assembly, and newly made cilia were abnormally short. The glycylation domain also was required for maintenance of the length of already assembled cilia. In contrast to the aberrant assembly of cilia, several types of cortical organelles showed an abnormally high number of microtubules in the same mutant cells. Thus, the consequences of deficiency in tubulin glycylation are organelle type specific and lead to either insufficient assembly (cilia) or excessive assembly (basal bodies and cortical microtubules). We suggest that the diverse functions of the beta-tubulin glycylation domain are executed by spatially restricted microtubule-associated proteins.
Collapse
Affiliation(s)
- Rupal Thazhath
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | | | | | | | | | | | | |
Collapse
|
284
|
Vismara R, Verni F, Barsanti L, Evangelista V, Gualtieri P. A short flagella mutant of Dunaliella salina (Chlorophyta, Chlorophyceae). Micron 2004; 35:337-44. [PMID: 15006360 DOI: 10.1016/j.micron.2004.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Dunaliella salina (Chlorophyta, Chlorophyceae) is a unicellular wall-less biflagellate alga. In this paper we describe a spontaneous mutant of D. salina, isolated from wild type cultures, which is characterized by very short flagella. The ultrastructure showed the basic 9 + 2 organization of wild-type flagella. Immunofluorescence localization of tubulin in this mutant confirmed the normal construction of the axoneme. Although, the mutant does not swim, still it is able to move and perform photobehavior. As shown by track reconstruction, and rotation movements, observed by means of reflection microscopy, this mutant can move, probably gliding by means of its stumpy flagella. A possible model to explain the mutant motion pattern is discussed.
Collapse
Affiliation(s)
- Rosa Vismara
- Istituto di Biofisica CNR, Area della Ricerca Pisa, Via Moruzzi 1, 56124 Pisa, Italy
| | | | | | | | | |
Collapse
|
285
|
Abstract
The recent identification in Chlamydomonas of the intraflagellar transport machinery that assembles cilia and flagella has triggered a renaissance of interest in these organelles that transcends studies on their well-characterized ability to move. New studies on several fronts have revealed that the machinery for flagellar assembly/disassembly is regulated by homologs of mitotic proteins, that cilia play essential roles in sensory transduction, and that mutations in cilia/basal body proteins are responsible for cilia-related human disorders from polycystic kidney disease to a syndrome associated with obesity, hypertension, and diabetes.
Collapse
Affiliation(s)
- William J Snell
- Department of Cell Biology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
| | | | | |
Collapse
|
286
|
Pan J, Wang Q, Snell WJ. An aurora kinase is essential for flagellar disassembly in Chlamydomonas. Dev Cell 2004; 6:445-51. [PMID: 15030766 DOI: 10.1016/s1534-5807(04)00064-4] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Revised: 02/06/2004] [Accepted: 02/09/2004] [Indexed: 11/26/2022]
Abstract
Cilia and flagella play key roles in development and sensory transduction, and several human disorders, including polycystic kidney disease, are associated with the failure to assemble cilia. Here, we show that the aurora protein kinase CALK in the biflagellated alga Chlamydomonas has a central role in two pathways for eliminating flagella. Cells rendered deficient in CALK were defective in regulated flagellar excision and regulated flagellar disassembly. Exposure of cells to altered ionic conditions, the absence of a centriole/basal body for nucleating flagellar assembly, cessation of delivery of flagellar components to their tip assembly site, and formation of zygotes all led to activation of the regulated disassembly pathway as indicated by phosphorylation of CALK and the absence of flagella. We propose that cells have a sensory pathway that detects conditions that are inappropriate for possession of a flagellum, and that CALK is a key effector of flagellar disassembly in that pathway.
Collapse
Affiliation(s)
- Junmin Pan
- Department of Cell Biology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | | | | |
Collapse
|
287
|
Abstract
It has been a decade since a novel form of microtubule (MT)-based motility, i.e., intraflagellar transport (IFT), was discovered in Chlamydomonas flagella. Subsequent research has supported the hypothesis that IFT is required for the assembly and maintenance of all cilia and flagella and that its underlying mechanism involves the transport of nonmembrane-bound macromolecular protein complexes (IFT particles) along axonemal MTs beneath the ciliary membrane. IFT requires the action of the anterograde kinesin-II motors and the retrograde IFT-dynein motors to transport IFT particles in opposite directions along the MT polymer lattice from the basal body to the tip of the axoneme and back again. A rich diversity of biological processes has been shown to depend upon IFT, including flagellar length control, cell swimming, mating and feeding, photoreception, animal development, sensory perception, chemosensory behavior, and lifespan control. These processes reflect the varied roles of cilia and flagella in motility and sensory signaling.
Collapse
Affiliation(s)
- Jonathan M Scholey
- Center for Genetics and Development, Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
| |
Collapse
|
288
|
Qin H, Diener DR, Geimer S, Cole DG, Rosenbaum JL. Intraflagellar transport (IFT) cargo: IFT transports flagellar precursors to the tip and turnover products to the cell body. ACTA ACUST UNITED AC 2004; 164:255-66. [PMID: 14718520 PMCID: PMC2172340 DOI: 10.1083/jcb.200308132] [Citation(s) in RCA: 270] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Intraflagellar transport (IFT) is the bidirectional movement of multisubunit protein particles along axonemal microtubules and is required for assembly and maintenance of eukaryotic flagella and cilia. One posited role of IFT is to transport flagellar precursors to the flagellar tip for assembly. Here, we examine radial spokes, axonemal subunits consisting of 22 polypeptides, as potential cargo for IFT. Radial spokes were found to be partially assembled in the cell body, before being transported to the flagellar tip by anterograde IFT. Fully assembled radial spokes, detached from axonemal microtubules during flagellar breakdown or turnover, are removed from flagella by retrograde IFT. Interactions between IFT particles, motors, radial spokes, and other axonemal proteins were verified by coimmunoprecipitation of these proteins from the soluble fraction of Chlamydomonas flagella. These studies indicate that one of the main roles of IFT in flagellar assembly and maintenance is to transport axonemal proteins in and out of the flagellum.
Collapse
Affiliation(s)
- Hongmin Qin
- MCDB Dept., Yale University, New Haven, CT 06520, USA
| | | | | | | | | |
Collapse
|
289
|
Abstract
Deciliation, also known as deflagellation, flagellar autotomy, flagellar excision, or flagellar shedding, refers to the process whereby eukaryotic cells shed their cilia or flagella, often in response to stress. Used for many decades as a tool for scientists interested in the structure, function, and genesis of cilia, deciliation itself is a process worthy of scientific investigation. Deciliation has numerous direct medical implications, but more profoundly, intriguing relationships between deciliation, ciliogenesis, and the cell cycle indicate that understanding the mechanism of deciliation will contribute to a deeper understanding of broad aspects of cell biology. This review provides a critical examination of diverse data bearing on this problem. It also highlights current deficiencies in our understanding of the mechanism of deciliation.
Collapse
Affiliation(s)
- Lynne M Quarmby
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| |
Collapse
|
290
|
Tam LW, Dentler WL, Lefebvre PA. Defective flagellar assembly and length regulation in LF3 null mutants in Chlamydomonas. J Cell Biol 2003; 163:597-607. [PMID: 14610061 PMCID: PMC2173655 DOI: 10.1083/jcb.200307143] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Accepted: 09/09/2003] [Indexed: 11/30/2022] Open
Abstract
Four long-flagella (LF) genes are important for flagellar length control in Chlamydomonas reinhardtii. Here, we characterize two new null lf3 mutants whose phenotypes are different from previously identified lf3 mutants. These null mutants have unequal-length flagella that assemble more slowly than wild-type flagella, though their flagella can also reach abnormally long lengths. Prominent bulges are found at the distal ends of short, long, and regenerating flagella of these mutants. Analysis of the flagella by electron and immunofluorescence microscopy and by Western blots revealed that the bulges contain intraflagellar transport complexes, a defect reported previously (for review see Cole, D.G., 2003. Traffic. 4:435-442) in a subset of mutants defective in intraflagellar transport. We have cloned the wild-type LF3 gene and characterized a hypomorphic mutant allele of LF3. LF3p is a novel protein located predominantly in the cell body. It cosediments with the product of the LF1 gene in sucrose density gradients, indicating that these proteins may form a functional complex to regulate flagellar length and assembly.
Collapse
Affiliation(s)
- Lai-Wa Tam
- Department of Plant Biology, University of Minnesota, St. Paul, MN 55108, USA
| | | | | |
Collapse
|
291
|
Pedersen LB, Geimer S, Sloboda RD, Rosenbaum JL. The Microtubule Plus End-Tracking Protein EB1 Is Localized to the Flagellar Tip and Basal Bodies in Chlamydomonas reinhardtii. Curr Biol 2003; 13:1969-74. [PMID: 14614822 DOI: 10.1016/j.cub.2003.10.058] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Flagellar axonemes assemble and continuously turn over at the flagellar tip. The supply and removal of axonemal subunits at the tip are mediated by intraflagellar transport (IFT), a motility process essential for the assembly and maintenance of all eukaryotic flagella and cilia. IFT is characterized by the movement of large protein complexes (IFT particles) from the basal bodies to the flagellar tip by kinesin-II and from the tip back to the basal bodies by cytoplasmic dynein 1b. The IFT particles consist of approximately 16 polypeptides partitioned into two complexes, A and B, and associate with axonemal precursors/turn over products. The mechanisms by which IFT motor regulation and cargo loading/unloading occur at the flagellar tip are unknown. We identified a Chlamydomonas reinhardtii ortholog of the microtubule (MT) plus end-tracking protein EB1 [4] (CrEB1) and show here that CrEB1 localizes to the tip of flagella and to the proximal part of the basal bodies. Furthermore, we found that CrEB1 is depleted from flagella of the temperature-sensitive (ts) flagellar assembly-defective (fla) mutant fla11(ts) at the restrictive temperature. This depletion of CrEB1 is accompanied by a dramatic accumulation of IFT particle polypeptides near the flagellar tip.
Collapse
Affiliation(s)
- Lotte B Pedersen
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | | | | | | |
Collapse
|
292
|
Kohl L, Robinson D, Bastin P. Novel roles for the flagellum in cell morphogenesis and cytokinesis of trypanosomes. EMBO J 2003; 22:5336-46. [PMID: 14532107 PMCID: PMC213772 DOI: 10.1093/emboj/cdg518] [Citation(s) in RCA: 193] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2003] [Revised: 07/31/2003] [Accepted: 08/15/2003] [Indexed: 11/13/2022] Open
Abstract
Flagella and cilia are elaborate cytoskeletal structures conserved from protists to mammals, where they fulfil functions related to motility or sensitivity. Here we demonstrate novel roles for the flagellum in the control of cell size, shape, polarity and division of the protozoan Trypanosoma brucei. To investigate the function of the flagellum, its formation was perturbed by inducible RNA interference silencing of com ponents required for intraflagellar transport, a dynamic process necessary for flagellum assembly. First, we show that down-regulation of intraflagellar transport leads to assembly of a shorter flagellum. Strikingly, cells with a shorter flagellum are smaller, with a direct correlation between flagellum length and cell size. Detailed morphogenetic analysis reveals that the tip of the new flagellum defines the point where cytokinesis is initiated. Secondly, when new flagellum formation is completely blocked, non-flagellated cells are very short, lose their normal shape and polarity, and fail to undergo cytokinesis. We show that flagellum elongation controls formation of cytoskeletal structures (present in the cell body) that act as molecular organizers of the cell.
Collapse
Affiliation(s)
- Linda Kohl
- INSERM U565 and CNRS UMR8646, Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris cedex 05, France
| | | | | |
Collapse
|
293
|
Han YG, Kwok BH, Kernan MJ. Intraflagellar Transport Is Required in Drosophila to Differentiate Sensory Cilia but Not Sperm. Curr Biol 2003; 13:1679-86. [PMID: 14521833 DOI: 10.1016/j.cub.2003.08.034] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Intraflagellar transport (IFT) uses kinesin II to carry a multiprotein particle to the tips of eukaryotic cilia and flagella and a nonaxonemal dynein to return it to the cell body. IFT particle proteins and motors are conserved in ciliated eukaryotes, and IFT-deficient mutants in algae, nematodes, and mammals fail to extend or maintain cilia and flagella, including sensory cilia. In Drosophila, the only ciliated cells are sensory neurons and sperm. no mechanoreceptor potential (nomp) mutations have been isolated that affect the differentiation and function of ciliated sense organs. The nompB gene is here shown to encode an IFT protein. Its mutant phenotypes reveal the consequences of an IFT defect in an insect. RESULTS Mechanosensory and olfactory neurons in nompB mutants have missing or defective cilia. nompB encodes the Drosophila homolog of the IFT complex B protein IFT88/Polaris/OSM-5. nompB is expressed in the ciliated sensory neurons, and a functional, tagged NOMPB protein is located in sensory cilia and around basal bodies. Surprisingly, nompB mutant males produce normally elongated, motile sperm. Neuronally restricted expression and male germline mosaic experiments show that nompB-deficient sperm are fully functional in transfer, competition, and fertilization. CONCLUSIONS NOMPB, the Drosophila homolog of IFT88, is required for the assembly of sensory cilia but not for the extension or function of the sperm flagellum. Assembly of this extremely long axoneme is therefore independent of IFT.
Collapse
Affiliation(s)
- Young-Goo Han
- Graduate Program in Genetics, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
| | | | | |
Collapse
|
294
|
Sarpal R, Todi SV, Sivan-Loukianova E, Shirolikar S, Subramanian N, Raff EC, Erickson JW, Ray K, Eberl DF. Drosophila KAP Interacts with the Kinesin II Motor Subunit KLP64D to Assemble Chordotonal Sensory Cilia, but Not Sperm Tails. Curr Biol 2003; 13:1687-96. [PMID: 14521834 DOI: 10.1016/j.cub.2003.09.025] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Kinesin II-mediated anterograde intraflagellar transport (IFT) is essential for the assembly and maintenance of flagella and cilia in various cell types. Kinesin associated protein (KAP) is identified as the non-motor accessory subunit of Kinesin II, but its role in the corresponding motor function is not understood. RESULTS We show that mutations in the Drosophila KAP (DmKap) gene could eliminate the sensory cilia as well as the sound-evoked potentials of Johnston's organ (JO) neurons. Ultrastructure analysis of these mutants revealed that the ciliary axonemes are absent. Mutations in Klp64D, which codes for a Kinesin II motor subunit in Drosophila, show similar ciliary defects. All these defects are rescued by exclusive expression of DmKAP and KLP64D/KIF3A in the JO neurons of respective mutants. Furthermore, reduced copy number of the DmKap gene was found to enhance the defects of hypomorphic Klp64D alleles. Unexpectedly, however, both the DmKap and the Klp64D mutant adults produce vigorously motile sperm with normal axonemes. CONCLUSIONS KAP plays an essential role in Kinesin II function, which is required for the axoneme growth and maintenance of the cilia in Drosophila type I sensory neurons. However, the flagellar assembly in Drosophila spermatids does not require Kinesin II and is independent of IFT.
Collapse
Affiliation(s)
- Ritu Sarpal
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | | | | | | | | | | | | | | | | |
Collapse
|
295
|
Parker JDK, Quarmby LM. Chlamydomonas fla mutants reveal a link between deflagellation and intraflagellar transport. BMC Cell Biol 2003; 4:11. [PMID: 12930563 PMCID: PMC194436 DOI: 10.1186/1471-2121-4-11] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Accepted: 08/20/2003] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Cilia and flagella are often lost in anticipation of mitosis or in response to stress. There are two ways that a cell can lose its flagella: resorption or deflagellation. Deflagellation involves active severing of the axoneme at the base of the flagellum; this process is defective in Chlamydomonas fa mutants. In contrast, resorption has been thought to occur as a consequence of constitutive disassembly at the tip in the absence of continued assembly, which requires intraflagellar transport (IFT). Chlamydomonas fla mutants are unable to build and maintain flagella due to defects in IFT. RESULTS fla10 cells, which are defective in kinesin-II, the anterograde IFT motor, resorb their flagella at the restrictive temperature (33 degrees C), as previously reported. We find that in standard media containing approximately 300 microM calcium, fla10 cells lose flagella by deflagellation at 33 degrees C. This temperature-induced deflagellation of a fla mutant is not predicted by the IFT-based model for flagellar length control. Other fla mutants behave similarly, losing their flagella by deflagellation instead of resorption, if adequate calcium is available. These data suggest a new model whereby flagellar resorption involves active disassembly at the base of the flagellum via a mechanism with components in common with the severing machinery of deflagellation. As predicted by this model, we discovered that deflagellation stimuli induce resorption if deflagellation is blocked either by mutation in a FA gene or by lack of calcium. Further support for this model comes from our discovery that fla10-fa double mutants resorb their flagella more slowly than fla10 mutants. CONCLUSIONS Deflagellation of the fla10 mutant at the restrictive temperature is indicative of an active disassembly signal, which can manifest as either resorption or deflagellation. We propose that when IFT is halted by either an inactivating mutation or a cellular signal, active flagellar disassembly is initiated. This active disassembly is distinct from the constitutive disassembly which plays a role in flagellar length control.
Collapse
Affiliation(s)
| | - Lynne Marie Quarmby
- Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| |
Collapse
|
296
|
Wiese M, Kuhn D, Grünfelder CG. Protein kinase involved in flagellar-length control. EUKARYOTIC CELL 2003; 2:769-77. [PMID: 12912896 PMCID: PMC178386 DOI: 10.1128/ec.2.4.769-777.2003] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During its life cycle, the parasitic protozoon Leishmania mexicana differentiates from a flagellated form, the promastigote, to an amastigote form carrying a rudimentary flagellum. Besides biochemical changes, this process involves a change in overall cell morphology including flagellar shortening. A mitogen-activated protein kinase kinase homologue designated LmxMKK was identified in a homology screening and found to be critically involved in the regulation of flagellar assembly and cell size. LmxMKK is exclusively expressed in the promastigote stage and is likely to be regulated by posttranslational mechanisms such as phosphorylation. A deletion mutant for the single-copy gene revealed motile flagella dramatically reduced in length and lacking the paraflagellar rod, a structure adjacent to the axoneme in kinetoplastid flagella. Moreover, a fraction of the cells showed perturbance of the axonemal structure. Complementation of the deletion mutant with the wild-type gene restored typical promastigote morphology. We propose that LmxMKK influences anterograde intraflagellar transport to maintain flagellar length in Leishmania promastigotes; as such, it is the first protein kinase known to be involved in organellar assembly.
Collapse
Affiliation(s)
- Martin Wiese
- Parasitology Section, Bernhard-Nocht-Institute for Tropical Medicine, D-20359 Hamburg, Germany.
| | | | | |
Collapse
|
297
|
Tilney LG, Connelly PS, Ruggiero L, Vranich KA, Guild GM. Actin filament turnover regulated by cross-linking accounts for the size, shape, location, and number of actin bundles in Drosophila bristles. Mol Biol Cell 2003; 14:3953-66. [PMID: 14517310 PMCID: PMC206991 DOI: 10.1091/mbc.e03-03-0158] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Drosophila bristle cells are shaped during growth by longitudinal bundles of cross-linked actin filaments attached to the plasma membrane. We used confocal and electron microscopy to examine actin bundle structure and found that during bristle elongation, snarls of uncross-linked actin filaments and small internal bundles also form in the shaft cytoplasm only to disappear within 4 min. Thus, formation and later removal of actin filaments are prominent features of growing bristles. These transient snarls and internal bundles can be stabilized by culturing elongating bristles with jasplakinolide, a membrane-permeant inhibitor of actin filament depolymerization, resulting in enormous numbers of internal bundles and uncross-linked filaments. Examination of bundle disassembly in mutant bristles shows that plasma membrane association and cross-bridging adjacent actin filaments together inhibits depolymerization. Thus, highly cross-bridged and membrane-bound actin filaments turn over slowly and persist, whereas poorly cross-linked filaments turnover more rapidly. We argue that the selection of stable bundles relative to poorly cross-bridged filaments can account for the size, shape, number, and location of the longitudinal actin bundles in bristles. As a result, filament turnover plays an important role in regulating cytoskeleton assembly and consequently cell shape.
Collapse
Affiliation(s)
- Lewis G Tilney
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
| | | | | | | | | |
Collapse
|
298
|
Abstract
Little is known about the molecular basis of organelle size control in eukaryotes. Cells of the biflagellate alga Chlamydomonas reinhardtii actively maintain their flagella at a precise length. Chlamydomonas mutants that lose control of flagellar length have been isolated and used to demonstrate that a dynamic process keeps flagella at an appropriate length. To date, none of the proteins required for flagellar length control have been identified in any eukaryotic organism. Here, we show that a novel MAP kinase is crucial to enforcing wild-type flagellar length in C. reinhardtii. Null mutants of LF4 [2], a gene encoding a protein with extensive amino acid sequence identity to a mammalian MAP kinase of unknown function, MOK [3], are unable to regulate the length of their flagella. The LF4 protein (LF4p) is localized to the flagella, and in vitro enzyme assays confirm that the protein is a MAP kinase. The long-flagella phenotype of lf4 cells is rescued by transformation with the cloned LF4 gene. The demonstration that a novel MAP kinase helps enforce flagellar length control indicates that a previously unidentified signal transduction pathway controls organelle size in C. reinhardtii.
Collapse
Affiliation(s)
- Steven A Berman
- Department of Plant Biology, University of Minnesota, 250 Biological Sciences Center, St. Paul, MN 55108, USA
| | | | | | | |
Collapse
|
299
|
Abstract
First discovered in the green alga, Chlamydomonas, intraflagellar transport (IFT) is the bidirectional movement of protein particles along the length of eukaryotic cilia and flagella. Composed of approximately 16 different proteins, IFT particles are moved out to the distal tip of the organelle by kinesin-II and are brought back to the cell body by cytoplasmic dynein 1b. Mutant analysis of the IFT motor and particle proteins using diverse organisms has revealed a conserved and essential role for IFT in the assembly and maintenance of cilia and flagella. IFT is thought to mediate this assembly through the delivery of axonemal precursors out to the distal tip of the growing organelle. Consistent with this model, the IFT particle proteins are rich in protein-protein binding motifs, suggesting that the particles may act as scaffolds for the binding of multiple cargoes. With most of the IFT proteins now identified at the level of the gene, this review will briefly examine both the structure and function of the IFT machinery of Chlamydomonas reinhardtii.
Collapse
Affiliation(s)
- Douglas G Cole
- Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, Idaho, 83844-3052, USA.
| |
Collapse
|
300
|
Abstract
The control of flagellar length can be easily studied in the model genetic cell Chlamydomonas. Recent work has revealed that the mutant gene in a long-flagella mutant encodes a protein kinase.
Collapse
Affiliation(s)
- Joel Rosenbaum
- Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.
| |
Collapse
|