1
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Cole ES, Maier W, Joachimiak E, Jiang YY, Lee C, Collet E, Chmelik C, Romero DP, Chalker D, Alli NK, Ruedlin TM, Ozzello C, Gaertig J. The Tetrahymena bcd1 mutant implicates endosome trafficking in ciliate, cortical pattern formation. Mol Biol Cell 2023; 34:ar82. [PMID: 37163326 PMCID: PMC10398878 DOI: 10.1091/mbc.e22-11-0501] [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: 11/09/2022] [Revised: 03/15/2023] [Accepted: 05/01/2023] [Indexed: 05/11/2023] Open
Abstract
Ciliates, such as Tetrahymena thermophila, evolved complex mechanisms to determine both the location and dimensions of cortical organelles such as the oral apparatus (OA: involved in phagocytosis), cytoproct (Cyp: for eliminating wastes), and contractile vacuole pores (CVPs: involved in water expulsion). Mutations have been recovered in Tetrahymena that affect both the localization of such organelles along anterior-posterior and circumferential body axes and their dimensions. Here we describe BCD1, a ciliate pattern gene that encodes a conserved Beige-BEACH domain-containing protein a with possible protein kinase A (PKA)-anchoring activity. Similar proteins have been implicated in endosome trafficking and are linked to human Chediak-Higashi syndrome and autism. Mutations in the BCD1 gene broaden cortical organelle domains as they assemble during predivision development. The Bcd1 protein localizes to membrane pockets at the base of every cilium that are active in endocytosis. PKA activity has been shown to promote endocytosis in other organisms, so we blocked clathrin-mediated endocytosis (using "dynasore") and inhibited PKA (using H89). In both cases, treatment produced partial phenocopies of the bcd1 pattern mutant. This study supports a model in which the dimensions of diverse cortical organelle assembly-platforms may be determined by regulated balance between constitutive exocytic delivery and PKA-regulated endocytic retrieval of organelle materials and determinants.
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Affiliation(s)
- Eric S. Cole
- Biology Department, St. Olaf College, Northfield, MN 55057
| | - Wolfgang Maier
- Bioinformatics Group, Department of Computer Science, University of Freiburg, 79110 Freiburg, Germany
| | - Ewa Joachimiak
- Laboratory of Cytoskeleton and Cilia Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 02-093 Warsaw, Poland
| | - Yu-yang Jiang
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637
| | - Chinkyu Lee
- Department of Cellular Biology, University of Georgia, Athens, GA 30605
| | - Erik Collet
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Carl Chmelik
- Biology Department, St. Olaf College, Northfield, MN 55057
| | - Daniel P. Romero
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455
| | - Douglas Chalker
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63021
| | - Nurudeen K. Alli
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63021
| | - Tina M. Ruedlin
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63021
| | - Courtney Ozzello
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, CO 80309
| | - Jacek Gaertig
- Department of Cellular Biology, University of Georgia, Athens, GA 30605
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2
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Sparvoli D, Delabre J, Penarete‐Vargas DM, Kumar Mageswaran S, Tsypin LM, Heckendorn J, Theveny L, Maynadier M, Mendonça Cova M, Berry‐Sterkers L, Guérin A, Dubremetz J, Urbach S, Striepen B, Turkewitz AP, Chang Y, Lebrun M. An apical membrane complex for triggering rhoptry exocytosis and invasion in Toxoplasma. EMBO J 2022; 41:e111158. [PMID: 36245278 PMCID: PMC9670195 DOI: 10.15252/embj.2022111158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 09/13/2022] [Accepted: 09/19/2022] [Indexed: 01/13/2023] Open
Abstract
Apicomplexan parasites possess secretory organelles called rhoptries that undergo regulated exocytosis upon contact with the host. This process is essential for the parasitic lifestyle of these pathogens and relies on an exocytic machinery sharing structural features and molecular components with free-living ciliates. However, how the parasites coordinate exocytosis with host interaction is unknown. Here, we performed a Tetrahymena-based transcriptomic screen to uncover novel exocytic factors in Ciliata and conserved in Apicomplexa. We identified membrane-bound proteins, named CRMPs, forming part of a large complex essential for rhoptry secretion and invasion in Toxoplasma. Using cutting-edge imaging tools, including expansion microscopy and cryo-electron tomography, we show that, unlike previously described rhoptry exocytic factors, TgCRMPs are not required for the assembly of the rhoptry secretion machinery and only transiently associate with the exocytic site-prior to the invasion. CRMPs and their partners contain putative host cell-binding domains, and CRMPa shares similarities with GPCR proteins. Collectively our data imply that the CRMP complex acts as a host-molecular sensor to ensure that rhoptry exocytosis occurs when the parasite contacts the host cell.
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Affiliation(s)
- Daniela Sparvoli
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Jason Delabre
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | | | - Shrawan Kumar Mageswaran
- Department of Biochemistry and Biophysics, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Lev M Tsypin
- Department of Molecular Genetics and Cell BiologyUniversity of ChicagoChicagoILUSA
- Present address:
Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaCAUSA
| | - Justine Heckendorn
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Liam Theveny
- Department of Biochemistry and Biophysics, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Marjorie Maynadier
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Marta Mendonça Cova
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Laurence Berry‐Sterkers
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Amandine Guérin
- Department of Pathobiology, School of Veterinary MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Jean‐François Dubremetz
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
| | - Serge Urbach
- IGFUniversité de Montpellier, CNRS, INSERMMontpellierFrance
| | - Boris Striepen
- Department of Pathobiology, School of Veterinary MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell BiologyUniversity of ChicagoChicagoILUSA
| | - Yi‐Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPAUSA
| | - Maryse Lebrun
- Laboratory of Pathogen Host InteractionsUMR 5235 CNRS, Université de MontpellierMontpellierFrance
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Akkale C, Cassidy-Hanley DM, Clark TG. Tetrahymena thermophila granule lattice protein 3 improves solubility of sexual stage malaria antigens expressed in Escherichia coli. Protein Expr Purif 2022; 194:106060. [PMID: 35134517 PMCID: PMC9977573 DOI: 10.1016/j.pep.2022.106060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 01/29/2022] [Accepted: 01/31/2022] [Indexed: 02/05/2023]
Abstract
The requirement for low cost manufacturing makes bacterial cells a logical platform for the production of recombinant subunit vaccines for malaria. However, protein solubility has been a major stumbling block with prokaryotic expression systems. Notable examples include the transmission blocking vaccine candidates, Pfs25 and Pfs48/45, which are almost entirely insoluble when expressed as recombinant proteins in Escherichia coli. Various solubility tags have been used with limited success in improving solubility, although recent studies with granule lattice protein 1 (Grl1p) from the ciliated protozoan, Tetrahymena thermophila, have shown promise. Here, we examine a related solubility tag, granule lattice protein 3 (Grl3p) from T. thermophila, and compare it to both Grl1p and the well-studied maltose binding protein (MBP) used to improve the solubility of multiple protein targets. We find that Grl3p performs comparably to Grl1p when linked to Pfs25 but significantly improves solubility when paired with Pfs48/45.
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Affiliation(s)
- Cengiz Akkale
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA; Department of Bioengineering, Faculty of Engineering, Adana Alparslan Türkeş Science and Technology University, Adana, Turkey.
| | - Donna Marie Cassidy-Hanley
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Theodore G. Clark
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
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4
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Kuppannan A, Jiang YY, Maier W, Liu C, Lang CF, Cheng CY, Field MC, Zhao M, Zoltner M, Turkewitz AP. A novel membrane complex is required for docking and regulated exocytosis of lysosome-related organelles in Tetrahymena thermophila. PLoS Genet 2022; 18:e1010194. [PMID: 35587496 PMCID: PMC9159632 DOI: 10.1371/journal.pgen.1010194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 06/01/2022] [Accepted: 04/06/2022] [Indexed: 12/20/2022] Open
Abstract
In the ciliate Tetrahymena thermophila, lysosome-related organelles called mucocysts accumulate at the cell periphery where they secrete their contents in response to extracellular events, a phenomenon called regulated exocytosis. The molecular bases underlying regulated exocytosis have been extensively described in animals but it is not clear whether similar mechanisms exist in ciliates or their sister lineage, the Apicomplexan parasites, which together belong to the ecologically and medically important superphylum Alveolata. Beginning with a T. thermophila mutant in mucocyst exocytosis, we used a forward genetic approach to uncover MDL1 (Mucocyst Discharge with a LamG domain), a novel gene that is essential for regulated exocytosis of mucocysts. Mdl1p is a 40 kDa membrane glycoprotein that localizes to mucocysts, and specifically to a tip domain that contacts the plasma membrane when the mucocyst is docked. This sub-localization of Mdl1p, which occurs prior to docking, underscores a functional asymmetry in mucocysts that is strikingly similar to that of highly polarized secretory organelles in other Alveolates. A mis-sense mutation in the LamG domain results in mucocysts that dock but only undergo inefficient exocytosis. In contrast, complete knockout of MDL1 largely prevents mucocyst docking itself. Mdl1p is physically associated with 9 other proteins, all of them novel and largely restricted to Alveolates, and sedimentation analysis supports the idea that they form a large complex. Analysis of three other members of this putative complex, called MDD (for Mucocyst Docking and Discharge), shows that they also localize to mucocysts. Negative staining of purified MDD complexes revealed distinct particles with a central channel. Our results uncover a novel macromolecular complex whose subunits are conserved within alveolates but not in other lineages, that is essential for regulated exocytosis in T. thermophila.
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Affiliation(s)
- Aarthi Kuppannan
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Yu-Yang Jiang
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Wolfgang Maier
- Bio3/Bioinformatics and Molecular Genetics, Faculty of Biology and ZBMZ, Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Freiburg, Germany
| | - Chang Liu
- Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Charles F. Lang
- Committee on Genetics, Genomics, and Systems Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Chao-Yin Cheng
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dundee, Scotland, United Kingdom
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Minglei Zhao
- Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Martin Zoltner
- Biotechnology and Biomedicine Centre of the Academy of Sciences and Charles University (BIOCEV), Vestec, Czech Republic
| | - Aaron P. Turkewitz
- Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United State of America
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5
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Casler JC, Zajac AL, Valbuena FM, Sparvoli D, Jeyifous O, Turkewitz AP, Horne-Badovinac S, Green WN, Glick BS. ESCargo: a regulatable fluorescent secretory cargo for diverse model organisms. Mol Biol Cell 2020; 31:2892-2903. [PMID: 33112725 PMCID: PMC7927198 DOI: 10.1091/mbc.e20-09-0591] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/20/2020] [Accepted: 10/23/2020] [Indexed: 12/24/2022] Open
Abstract
Membrane traffic can be studied by imaging a cargo protein as it transits the secretory pathway. The best tools for this purpose initially block export of the secretory cargo from the endoplasmic reticulum (ER) and then release the block to generate a cargo wave. However, previously developed regulatable secretory cargoes are often tricky to use or specific for a single model organism. To overcome these hurdles for budding yeast, we recently optimized an artificial fluorescent secretory protein that exits the ER with the aid of the Erv29 cargo receptor, which is homologous to mammalian Surf4. The fluorescent secretory protein forms aggregates in the ER lumen and can be rapidly disaggregated by addition of a ligand to generate a nearly synchronized cargo wave. Here we term this regulatable secretory protein ESCargo (Erv29/Surf4-dependent secretory cargo) and demonstrate its utility not only in yeast cells, but also in cultured mammalian cells, Drosophila cells, and the ciliate Tetrahymena thermophila. Kinetic studies indicate that rapid export from the ER requires recognition by Erv29/Surf4. By choosing an appropriate ER signal sequence and expression vector, this simple technology can likely be used with many model organisms.
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Affiliation(s)
- Jason C. Casler
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Allison L. Zajac
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Fernando M. Valbuena
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Daniela Sparvoli
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Okunola Jeyifous
- Department of Neurobiology, University of Chicago, Chicago, IL 60637
- Marine Biological Laboratory, Woods Hole, MA 02543
| | - Aaron P. Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Sally Horne-Badovinac
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - William N. Green
- Department of Neurobiology, University of Chicago, Chicago, IL 60637
- Marine Biological Laboratory, Woods Hole, MA 02543
| | - Benjamin S. Glick
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
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6
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Agrawal A, Bisharyan Y, Papoyan A, Bednenko J, Cardarelli J, Yao M, Clark T, Berkmen M, Ke N, Colussi P. Fusion to Tetrahymena thermophila granule lattice protein 1 confers solubility to sexual stage malaria antigens in Escherichia coli. Protein Expr Purif 2018; 153:7-17. [PMID: 30081196 PMCID: PMC6189453 DOI: 10.1016/j.pep.2018.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 07/31/2018] [Accepted: 08/02/2018] [Indexed: 11/30/2022]
Abstract
A transmission-blocking vaccine targeting the sexual stages of Plasmodium species could play a key role in eradicating malaria. Multiple studies have identified the P. falciparum proteins Pfs25 and Pfs48/45 as prime targets for transmission-blocking vaccines. Although significant advances have been made in recombinant expression of these antigens, they remain difficult to produce at large scale and lack strong immunogenicity as subunit antigens. We linked a self-assembling protein, granule lattice protein 1 (Grl1p), from the ciliated protozoan, Tetrahymena thermophila, to regions of the ectodomains of either Pfs25 or Pfs48/45. We found that resulting protein chimera could be produced in E. coli as nanoparticles that could be readily purified in soluble form. When produced in the E. coli SHuffle strain, fusion to Grl1p dramatically increased solubility of target antigens while at the same time directing the formation of particles with diameters centering on 38 and 25 nm depending on the antigen. In a number of instances, co-expression with chaperone proteins and induction at a lower temperature further increased expression and solubility. Based on Western blotting and ELISA analysis, Pfs25 and Pfs48/45 retained their transmission-blocking epitopes within E. coli-derived particles, and the particles themselves elicited strong antibody responses in rabbits when given with an aluminum-based adjuvant. Antibodies against Pfs25-containing nanoparticles blocked parasite transmission in standard membrane-feeding assays. In conclusion, fusion to Grl1p can act as a solubility enhancer for proteins with limited solubility while retaining correct folding, which may be useful for applications such as the production of vaccines and other biologics.
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Affiliation(s)
| | | | | | | | | | | | - Theodore Clark
- TetraGenetics Inc, Arlington, MA, USA; Department of Immunology and Microbiology, Cornell University, Ithaca, NY, USA
| | | | - Na Ke
- New England Biolabs, Ipswich, MA, USA
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7
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Grl1 Protein is a Candidate K Antigen in Tetrahymena thermophila. Protist 2018; 169:321-332. [PMID: 29803115 DOI: 10.1016/j.protis.2018.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 03/09/2018] [Accepted: 03/19/2018] [Indexed: 01/18/2023]
Abstract
In Tetrahymena, K antigens associate only with mature basal bodies and are expected to play important roles in the morphogenesis and function of the membrane skeleton around basal bodies, but these proteins have not been identified and their functions are unknown. Commercially available anti-human Rho GDP-dissociation inhibitor α (RhoGDIα) antibody (sc-33201) was accidentally found to show very similar immunofluorescence staining patterns to those of anti-K antigen antibodies, such as 424A8 and 10D12 mouse monoclonal antibodies, in Tetrahymena. A 40kDa protein recognized by this antibody was partially purified and identified as granule lattice protein 1 (Grl1p) by matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry. In immunoblotting experiments this antibody was suggested to recognize endogenous Grl1p. The three-dimensional structure of proGrl1p protein predicted by I-TASSER was similar to a spectrin family protein. Grl1 may be a K antigen and a spectrin-like protein in Tetrahymena.
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8
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Sparvoli D, Richardson E, Osakada H, Lan X, Iwamoto M, Bowman GR, Kontur C, Bourland WA, Lynn DH, Pritchard JK, Haraguchi T, Dacks JB, Turkewitz AP. Remodeling the Specificity of an Endosomal CORVET Tether Underlies Formation of Regulated Secretory Vesicles in the Ciliate Tetrahymena thermophila. Curr Biol 2018; 28:697-710.e13. [PMID: 29478853 DOI: 10.1016/j.cub.2018.01.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/09/2017] [Accepted: 01/17/2018] [Indexed: 12/14/2022]
Abstract
In the endocytic pathway of animals, two related complexes, called CORVET (class C core vacuole/endosome transport) and HOPS (homotypic fusion and protein sorting), act as both tethers and fusion factors for early and late endosomes, respectively. Mutations in CORVET or HOPS lead to trafficking defects and contribute to human disease, including immune dysfunction. HOPS and CORVET are conserved throughout eukaryotes, but remarkably, in the ciliate Tetrahymena thermophila, the HOPS-specific subunits are absent, while CORVET-specific subunits have proliferated. VPS8 (vacuolar protein sorting), a CORVET subunit, expanded to 6 paralogs in Tetrahymena. This expansion correlated with loss of HOPS within a ciliate subgroup, including the Oligohymenophorea, which contains Tetrahymena. As uncovered via forward genetics, a single VPS8 paralog in Tetrahymena (VPS8A) is required to synthesize prominent secretory granules called mucocysts. More specifically, Δvps8a cells fail to deliver a subset of cargo proteins to developing mucocysts, instead accumulating that cargo in vesicles also bearing the mucocyst-sorting receptor Sor4p. Surprisingly, although this transport step relies on CORVET, it does not appear to involve early endosomes. Instead, Vps8a associates with the late endosomal/lysosomal marker Rab7, indicating that target specificity switching occurred in CORVET subunits during the evolution of ciliates. Mucocysts belong to a markedly diverse and understudied class of protist secretory organelles called extrusomes. Our results underscore that biogenesis of mucocysts depends on endolysosomal trafficking, revealing parallels with invasive organelles in apicomplexan parasites and suggesting that a wide array of secretory adaptations in protists, like in animals, depend on mechanisms related to lysosome biogenesis.
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Affiliation(s)
- Daniela Sparvoli
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | | | - Hiroko Osakada
- Advanced ICT Research Institute, National Institute of Information and Communications Technology (NICT), Kobe 651-2492, Japan
| | - Xun Lan
- Department of Genetics, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Masaaki Iwamoto
- Advanced ICT Research Institute, National Institute of Information and Communications Technology (NICT), Kobe 651-2492, Japan
| | - Grant R Bowman
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | - Cassandra Kontur
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | - William A Bourland
- Department of Biological Sciences, Boise State University, Boise, ID 83725-1515, USA
| | - Denis H Lynn
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Jonathan K Pritchard
- Department of Genetics, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA; Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Tokuko Haraguchi
- Advanced ICT Research Institute, National Institute of Information and Communications Technology (NICT), Kobe 651-2492, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Joel B Dacks
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA.
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9
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Kaur H, Sparvoli D, Osakada H, Iwamoto M, Haraguchi T, Turkewitz AP. An endosomal syntaxin and the AP-3 complex are required for formation and maturation of candidate lysosome-related secretory organelles (mucocysts) in Tetrahymena thermophila. Mol Biol Cell 2017; 28:1551-1564. [PMID: 28381425 PMCID: PMC5449153 DOI: 10.1091/mbc.e17-01-0018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 03/22/2017] [Accepted: 03/28/2017] [Indexed: 12/14/2022] Open
Abstract
Lysosome-related organelles (LROs) are secretory organelles formed by convergence between secretory and endosomal trafficking pathways. In Tetrahymena, secretory vesicles that resemble dense core granules are a new class of LROs whose synthesis depends on a conserved syntaxin required for heterotypic fusion and AP-3 for maturation. The ciliate Tetrahymena thermophila synthesizes large secretory vesicles called mucocysts. Mucocyst biosynthesis shares features with dense core granules (DCGs) in animal cells, including proteolytic processing of cargo proteins during maturation. However, other molecular features have suggested relatedness to lysosome-related organelles (LROs). LROs, which include diverse organelles in animals, are formed via convergence of secretory and endocytic trafficking. Here we analyzed Tetrahymena syntaxin 7-like 1 (Stx7l1p), a Qa-SNARE whose homologues in other lineages are linked with vacuoles/LROs. Stx7l1p is targeted to both immature and mature mucocysts and is essential in mucocyst formation. In STX7L1-knockout cells, the two major classes of mucocyst cargo proteins localize independently, accumulating in largely nonoverlapping vesicles. Thus initial formation of immature mucocysts involves heterotypic fusion, in which a subset of mucocyst proteins is delivered via an endolysosomal compartment. Further, we show that subsequent maturation requires AP-3, a complex widely implicated in LRO formation. Knockout of the µ-subunit gene does not impede delivery of any known mucocyst cargo but nonetheless arrests mucocyst maturation. Our data argue that secretory organelles in ciliates may represent a new class of LROs and reveal key roles of an endosomal syntaxin and AP-3 in the assembly of this complex compartment.
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Affiliation(s)
- Harsimran Kaur
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Daniela Sparvoli
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Hiroko Osakada
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe 651-2492, Japan
| | - Masaaki Iwamoto
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe 651-2492, Japan
| | - Tokuko Haraguchi
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe 651-2492, Japan.,Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
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10
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Whole Genome Sequencing Identifies a Novel Factor Required for Secretory Granule Maturation in Tetrahymena thermophila. G3-GENES GENOMES GENETICS 2016; 6:2505-16. [PMID: 27317773 PMCID: PMC4978903 DOI: 10.1534/g3.116.028878] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Unbiased genetic approaches have a unique ability to identify novel genes associated with specific biological pathways. Thanks to next generation sequencing, forward genetic strategies can be expanded to a wider range of model organisms. The formation of secretory granules, called mucocysts, in the ciliate Tetrahymena thermophila relies, in part, on ancestral lysosomal sorting machinery, but is also likely to involve novel factors. In prior work, multiple strains with defects in mucocyst biogenesis were generated by nitrosoguanidine mutagenesis, and characterized using genetic and cell biological approaches, but the genetic lesions themselves were unknown. Here, we show that analyzing one such mutant by whole genome sequencing reveals a novel factor in mucocyst formation. Strain UC620 has both morphological and biochemical defects in mucocyst maturation-a process analogous to dense core granule maturation in animals. Illumina sequencing of a pool of UC620 F2 clones identified a missense mutation in a novel gene called MMA1 (Mucocyst maturation). The defects in UC620 were rescued by expression of a wild-type copy of MMA1, and disrupting MMA1 in an otherwise wild-type strain phenocopies UC620. The product of MMA1, characterized as a CFP-tagged copy, encodes a large soluble cytosolic protein. A small fraction of Mma1p-CFP is pelletable, which may reflect association with endosomes. The gene has no identifiable homologs except in other Tetrahymena species, and therefore represents an evolutionarily recent innovation that is required for granule maturation.
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11
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Secretion of Polypeptide Crystals from Tetrahymena thermophila Secretory Organelles (Mucocysts) Depends on Processing by a Cysteine Cathepsin, Cth4p. EUKARYOTIC CELL 2015; 14:817-33. [PMID: 26092918 DOI: 10.1128/ec.00058-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/10/2015] [Indexed: 01/26/2023]
Abstract
In many organisms, sophisticated mechanisms facilitate release of peptides in response to extracellular stimuli. In the ciliate Tetrahymena thermophila, efficient peptide secretion depends on specialized vesicles called mucocysts that contain dense crystalline cores that expand rapidly during exocytosis. Core assembly depends of endoproteolytic cleavage of mucocyst proproteins by an aspartyl protease, cathepsin 3 (CTH3). Here, we show that a second enzyme identified by expression profiling, Cth4p, is also required for processing of proGrl proteins and for assembly of functional mucocysts. Cth4p is a cysteine cathepsin that localizes partially to endolysosomal structures and appears to act downstream of, and may be activated by, Cth3p. Disruption of CTH4 results in cells (Δcth4) that show aberrant trimming of Grl proproteins, as well as grossly aberrant mucocyst exocytosis. Surprisingly, Δcth4 cells succeed in assembling crystalline mucocyst cores. However, those cores do not undergo normal directional expansion during exocytosis, and they thus fail to efficiently extrude from the cells. We could phenocopy the Δcth4 defects by mutating conserved catalytic residues, indicating that the in vivo function of Cth4p is enzymatic. Our results indicate that as for canonical proteins packaged in animal secretory granules, the maturation of mucocyst proproteins involves sequential processing steps. The Δcth4 defects uncouple, in an unanticipated way, the assembly of mucocyst cores and their subsequent expansion and thereby reveal a previously unsuspected aspect of polypeptide secretion in ciliates.
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Kumar S, Briguglio JS, Turkewitz AP. An aspartyl cathepsin, CTH3, is essential for proprotein processing during secretory granule maturation in Tetrahymena thermophila. Mol Biol Cell 2014; 25:2444-60. [PMID: 24943840 PMCID: PMC4142616 DOI: 10.1091/mbc.e14-03-0833] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In animal cells, the assembly of dense cores in secretory granules is controlled by proteolytic processing of proproteins. The same phenomenon occurs in the ciliate Tetrahymena thermophila, but the proteases involved appear to be highly unrelated, suggesting that similar regulatory mechanisms have different molecular origins. In Tetrahymena thermophila, peptides secreted via dense-core granules, called mucocysts, are generated by proprotein processing. We used expression profiling to identify candidate processing enzymes, which localized as cyan fluorescent protein fusions to mucocysts. Of note, the aspartyl cathepsin Cth3p plays a key role in mucocyst-based secretion, since knockdown of this gene blocked proteolytic maturation of the entire set of mucocyst proproteins and dramatically reduced mucocyst accumulation. The activity of Cth3p was eliminated by mutation of two predicted active-site mutations, and overexpression of the wild-type gene, but not the catalytic-site mutant, partially rescued a Mendelian mutant defective in mucocyst proprotein processing. Our results provide the first direct evidence for the role of proprotein processing in this system. Of interest, both localization and the CTH3 disruption phenotype suggest that the enzyme provides non–mucocyst-related functions. Phylogenetic analysis of the T. thermophila cathepsins, combined with prior work on the role of sortilin receptors in mucocyst biogenesis, suggests that repurposing of lysosomal enzymes was an important step in the evolution of secretory granules in ciliates.
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Affiliation(s)
- Santosh Kumar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Joseph S Briguglio
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
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Briguglio JS, Turkewitz AP. Tetrahymena thermophila: a divergent perspective on membrane traffic. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 322:500-16. [PMID: 24634411 DOI: 10.1002/jez.b.22564] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 01/13/2014] [Accepted: 01/22/2014] [Indexed: 12/12/2022]
Abstract
Tetrahymena thermophila, a member of the Ciliates, represents a class of organisms distantly related from commonly used model organisms in cell biology, and thus offers an opportunity to explore potentially novel mechanisms and their evolution. Ciliates, like all eukaryotes, possess a complex network of organelles that facilitate both macromolecular uptake and secretion. The underlying endocytic and exocytic pathways are key mediators of a cell's interaction with its environment, and may therefore show niche-specific adaptations. Our laboratory has taken a variety of approaches to identify key molecular determinants for membrane trafficking pathways in Tetrahymena. Studies of Rab GTPases, dynamins, and sortilin-family receptors substantiate the widespread conservation of some features but also uncover surprising roles for lineage-restricted innovation.
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Affiliation(s)
- Joseph S Briguglio
- The Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois
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14
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Plattner H, Sehring IM, Mohamed IK, Miranda K, De Souza W, Billington R, Genazzani A, Ladenburger EM. Calcium signaling in closely related protozoan groups (Alveolata): non-parasitic ciliates (Paramecium, Tetrahymena) vs. parasitic Apicomplexa (Plasmodium, Toxoplasma). Cell Calcium 2012; 51:351-82. [PMID: 22387010 DOI: 10.1016/j.ceca.2012.01.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/10/2012] [Accepted: 01/12/2012] [Indexed: 12/20/2022]
Abstract
The importance of Ca2+-signaling for many subcellular processes is well established in higher eukaryotes, whereas information about protozoa is restricted. Recent genome analyses have stimulated such work also with Alveolates, such as ciliates (Paramecium, Tetrahymena) and their pathogenic close relatives, the Apicomplexa (Plasmodium, Toxoplasma). Here we compare Ca2+ signaling in the two closely related groups. Acidic Ca2+ stores have been characterized in detail in Apicomplexa, but hardly in ciliates. Two-pore channels engaged in Ca2+-release from acidic stores in higher eukaryotes have not been stingently characterized in either group. Both groups are endowed with plasma membrane- and endoplasmic reticulum-type Ca2+-ATPases (PMCA, SERCA), respectively. Only recently was it possible to identify in Paramecium a number of homologs of ryanodine and inositol 1,3,4-trisphosphate receptors (RyR, IP3R) and to localize them to widely different organelles participating in vesicle trafficking. For Apicomplexa, physiological experiments suggest the presence of related channels although their identity remains elusive. In Paramecium, IP3Rs are constitutively active in the contractile vacuole complex; RyR-related channels in alveolar sacs are activated during exocytosis stimulation, whereas in the parasites the homologous structure (inner membrane complex) may no longer function as a Ca2+ store. Scrutinized comparison of the two closely related protozoan phyla may stimulate further work and elucidate adaptation to parasitic life. See also "Conclusions" section.
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Affiliation(s)
- H Plattner
- Department of Biology, University of Konstanz, P.O. Box 5560, 78457 Konstanz, Germany.
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Yoo SH, Hur YS. Enrichment of the inositol 1,4,5-trisphosphate receptor/Ca2+ channels in secretory granules and essential roles of chromogranins. Cell Calcium 2012; 51:342-50. [DOI: 10.1016/j.ceca.2011.12.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/07/2011] [Accepted: 12/10/2011] [Indexed: 11/26/2022]
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Abstract
The growth, survival, and life cycle progression of the freshwater ciliated protozoan Tetrahymena thermophila are responsive to protein signals thought to be released by constitutive secretion. In addition to providing insights about ciliate communication, studies of constitutive secretion are of interest for evaluating the utility of T. thermophila as a platform for the expression of secreted protein therapeutics. For these reasons, we undertook an unbiased investigation of T. thermophila secreted proteins using wild-type and secretion mutant strains. Extensive tandem mass spectrometry analyses of secretome samples were performed. We identified a total of 207 secretome proteins, most of which were not detected in a set of abundant whole-cell protein identifications. Numerous proteases and other hydrolases were secreted from cells grown in rich medium but not cells transferred to a nutrient starvation condition. On the other hand, we detected the starvation-enhanced secretion of a small number of cytosolic proteins, suggestive of an exosome-like pathway in T. thermophila. Subsets of proteins from the T. thermophila regulated secretion pathway were detected with differential representation across strains and culture conditions. Finally, many secretome proteins had a predicted N-terminal signal sequence but no other annotated characteristic or functional classification. Our work provides the first comprehensive analysis of secreted proteins in T. thermophila and establishes the groundwork for future studies of constitutive protein secretion biology and biotechnology in ciliates.
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Plattner H. Membrane Trafficking in Protozoa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 280:79-184. [DOI: 10.1016/s1937-6448(10)80003-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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18
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Independent transport and sorting of functionally distinct protein families in Tetrahymena thermophila dense core secretory granules. EUKARYOTIC CELL 2009; 8:1575-83. [PMID: 19684282 DOI: 10.1128/ec.00151-09] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, DeltaGRT1 DeltaGRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in DeltaGRT1 DeltaGRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from DeltaGRT1 DeltaGRT2 cells appear less adhesive than those from the wild type.
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19
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Nam SW, Kim ST, Lee KM, Kim SH, Kou S, Lim J, Hwang H, Joo MK, Jeong B, Yoo SH, Park S. N-Methyl-d-Aspartate Receptor-Mediated Chemotaxis and Ca2+ Signaling in Tetrahymena pyriformis. Protist 2009; 160:331-42. [DOI: 10.1016/j.protis.2008.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 10/26/2008] [Indexed: 01/29/2023]
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20
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Glutamylation on alpha-tubulin is not essential but affects the assembly and functions of a subset of microtubules in Tetrahymena thermophila. EUKARYOTIC CELL 2008; 7:1362-72. [PMID: 18586949 DOI: 10.1128/ec.00084-08] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Tubulin undergoes glutamylation, a conserved posttranslational modification of poorly understood function. We show here that in the ciliate Tetrahymena, most of the microtubule arrays contain glutamylated tubulin. However, the length of the polyglutamyl side chain is spatially regulated, with the longest side chains present on ciliary and basal body microtubules. We focused our efforts on the function of glutamylation on the alpha-tubulin subunit. By site-directed mutagenesis, we show that all six glutamates of the C-terminal tail domain of alpha-tubulin that provide potential sites for glutamylation are not essential but are needed for normal rates of cell multiplication and cilium-based functions (phagocytosis and cell motility). By comparative phylogeny and biochemical assays, we identify two conserved tubulin tyrosine ligase (TTL) domain proteins, Ttll1p and Ttll9p, as alpha-tubulin-preferring glutamyl ligase enzymes. In an in vitro microtubule glutamylation assay, Ttll1p showed a chain-initiating activity while Ttll9p had primarily a chain-elongating activity. GFP-Ttll1p localized mainly to basal bodies, while GFP-Ttll9p localized to cilia. Disruption of the TTLL1 and TTLL9 genes decreased the rates of cell multiplication and phagocytosis. Cells lacking both genes had fewer cortical microtubules and showed defects in the maturation of basal bodies. We conclude that glutamylation on alpha-tubulin is not essential but is required for efficiency of assembly and function of a subset of microtubule-based organelles. Furthermore, the spatial restriction of modifying enzymes appears to be a major mechanism that drives differential glutamylation at the subcellular level.
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21
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Elde NC, Long M, Turkewitz AP. A role for convergent evolution in the secretory life of cells. Trends Cell Biol 2007; 17:157-64. [PMID: 17329106 DOI: 10.1016/j.tcb.2007.02.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 01/19/2007] [Accepted: 02/14/2007] [Indexed: 10/23/2022]
Abstract
The role of convergent evolution in biological adaptation is increasingly appreciated. Many clear examples have been described at the level of individual proteins and for organismal morphology, and convergent mechanisms have even been invoked to account for similar community structures that are shared between ecosystems. At the cellular level, an important area that has received scant attention is the potential influence of convergent evolution on complex subcellular features, such as organelles. Here, we show that existing data strongly argue that convergent evolution underlies the similar properties of specialized secretory vesicles, called dense core granules, in the animal and ciliate lineages. We discuss both the criteria for judging convergent evolution and the contribution that such evolutionary analysis can make to improve our understanding of processes in cell biology. The elucidation of these underlying evolutionary relationships is vital because cellular structures that are assumed to be analogous, owing to shared features, might in fact be governed by different molecular mechanisms.
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Affiliation(s)
- Nels C Elde
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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22
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Elde NC, Morgan G, Winey M, Sperling L, Turkewitz AP. Elucidation of clathrin-mediated endocytosis in tetrahymena reveals an evolutionarily convergent recruitment of dynamin. PLoS Genet 2005; 1:e52. [PMID: 16276403 PMCID: PMC1277907 DOI: 10.1371/journal.pgen.0010052] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Accepted: 09/22/2005] [Indexed: 11/25/2022] Open
Abstract
Ciliates, although single-celled organisms, contain numerous subcellular structures and pathways usually associated with metazoans. How this cell biological complexity relates to the evolution of molecular elements is unclear, because features in these cells have been defined mainly at the morphological level. Among these ciliate features are structures resembling clathrin-coated, endocytic pits associated with plasma membrane invaginations called parasomal sacs. The combination of genome-wide sequencing in Tetrahymena thermophila with tools for gene expression and replacement has allowed us to examine this pathway in detail. Here we demonstrate that parasomal sacs are sites of clathrin-dependent endocytosis and that AP-2 localizes to these sites. Unexpectedly, endocytosis in Tetrahymena also involves a protein in the dynamin family, Drp1p (Dynamin-related protein 1). While phylogenetic analysis of AP subunits indicates a primitive origin for clathrin-mediated endocytosis, similar analysis of dynamin-related proteins suggests, strikingly, that the recruitment of dynamin-family proteins to the endocytic pathway occurred independently during the course of the ciliate and metazoan radiations. Consistent with this, our functional analysis suggests that the precise roles of dynamins in endocytosis, as well as the mechanisms of targeting, differ in metazoans and ciliates. The wings of bats and of birds are similar structures with similar functions but nonetheless evolved independently within these two different branches of animals. Many examples of this phenomenon, called convergent evolution, are known at the level of whole organisms. Here, the authors demonstrate that convergent evolution has also occurred at the level of individual cells, in a pathway responsible for taking up membrane from the cell surface. The authors took advantage of the recent genomic sequencing of distantly related organisms, and in particular of the single-celled ciliate Tetrahymena thermophila. In animal cells, one of the proteins required for membrane uptake is called dynamin. Dynamin is not required for this function in most nonanimal cells, but the authors discovered that Tetrahymena is an exception and that it uses a close relative of dynamin for particle uptake. After reconstructing the history of dynamin proteins, the authors found that the specific role in membrane uptake evolved independently in Tetrahymena and in animals.
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Affiliation(s)
- Nels C Elde
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, United States of America
| | - Garry Morgan
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Mark Winey
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Linda Sperling
- Centre de Genetique Moleculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
| | - Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, United States of America
- * To whom correspondence should be addressed. E-mail:
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23
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Smith JC, Northey JGB, Garg J, Pearlman RE, Siu KWM. Robust method for proteome analysis by MS/MS using an entire translated genome: demonstration on the ciliome of Tetrahymena thermophila. J Proteome Res 2005; 4:909-19. [PMID: 15952738 DOI: 10.1021/pr050013h] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To improve the utility of increasingly large numbers of available unannotated and initially poorly annotated genomic sequences for proteome analysis, we demonstrate that effective protein identification can be made on a large and unannotated genome. The strategy developed is to translate the unannotated genome sequence into amino acid sequence encoding putative proteins in all six reading frames, to identify peptides by tandem mass spectrometry (MS/MS), to localize them on the genome sequence, and to preliminarily annotate the protein via a similarity search by BLAST. These tasks have been optimized and automated. Optimization to obtain multiple peptide matches in effect extends the searchable region and results in more robust protein identification. The viability of this strategy is demonstrated with the identification of 223 cilia proteins in the unicellular eukaryotic model organism Tetrahymena thermophila, whose initial genomic sequence draft was released in November 2003. To the best of our knowledge, this is the first demonstration of large-scale protein identification based on such a large, unannotated genome. Of the 223 cilia proteins, 84 have no similarity to proteins in NCBI's nonredundant (nr) database. This methodology allows identifying the locations of the genes encoding these novel proteins, which is a necessary first step to downstream functional genomic experimentation.
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Affiliation(s)
- Jeffrey C Smith
- Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
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24
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Cowan AT, Bowman GR, Edwards KF, Emerson JJ, Turkewitz AP. Genetic, genomic, and functional analysis of the granule lattice proteins in Tetrahymena secretory granules. Mol Biol Cell 2005; 16:4046-60. [PMID: 15958493 PMCID: PMC1196318 DOI: 10.1091/mbc.e05-01-0028] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 04/27/2005] [Accepted: 06/03/2005] [Indexed: 11/11/2022] Open
Abstract
In some cells, the polypeptides stored in dense core secretory granules condense as ordered arrays. In ciliates such as Tetrahymena thermophila, the resulting crystals function as projectiles, expanding upon exocytosis. Isolation of granule contents previously defined five Granule lattice (Grl) proteins as abundant core constituents, whereas a functional screen identified a sixth family member. We have now expanded this screen to identify the nonredundant components required for projectile assembly. The results, further supported by gene disruption experiments, indicate that six Grl proteins define the core structure. Both in vivo and in vitro data indicate that core assembly begins in the endoplasmic reticulum with formation of specific hetero-oligomeric Grl proprotein complexes. Four additional GRL-like genes were found in the T. thermophila genome. Grl2p and Grl6p are targeted to granules, but the transcripts are present at low levels and neither is essential for core assembly. The DeltaGRL6 cells nonetheless showed a subtle change in granule morphology and a marked reduction in granule accumulation. Epistasis analysis suggests this results from accelerated loss of DeltaGRL6 granules, rather than from decreased synthesis. Our results not only provide insight into the organization of Grl-based granule cores but also imply that the functions of Grl proteins extend beyond core assembly.
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Affiliation(s)
- Andrew T Cowan
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
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25
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Jacobs ME, Cortezzo DE, Klobutcher LA. Assessing the effectiveness of coding and non-coding regions in antisense ribosome inhibition of gene expression in Tetrahymena. J Eukaryot Microbiol 2005; 51:536-41. [PMID: 15537088 DOI: 10.1111/j.1550-7408.2004.tb00289.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In Tetrahymena thermophila, an "antisense ribosome" technology has been developed for inhibiting gene expression and generating novel mutants. Short segments of genes are inserted in antisense orientation into an rDNA vector in a region corresponding to an external loop of the folded rRNA. DNA segments derived from the 5'-ends of genes have proven most effective in reducing cognate gene expression. To investigate the efficacy of other genic regions, we generated Tetrahymena cell lines with antisense ribosome constructs containing 100-bp DNA segments derived from the 5'-ends, 3'-ends, and internal coding regions of two non-essential genes, granule lattice protein 1 and macronuclear histone H1. The 5'- and 3'-end constructs inhibited gene expression, but antisense ribosomes derived exclusively from coding regions had little effect.
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Affiliation(s)
- Mary Ellen Jacobs
- Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA
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26
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Abstract
The release of polypeptides in response to extracellular cues is a notable feature of endocrine, exocrine and neuronal cells, and is based on regulated exocytosis via dense-core secretory granules. There is interest in this mode of secretion because of its importance in human physiology and also because regulated exocytosis reflects a complex pathway of membrane traffic that includes compartment-specific reversible macromolecular assembly, coat-independent vesicle budding, maturation/remodeling of both lumenal and membrane constituents, and stimulus-dependent membrane fusion. Secretory granules are absent in most unicellular model organisms but are highly developed in the Ciliates, which therefore offer attractive systems to study these phenomena. In Tetrahymena thermophila, biochemical and genetic approaches have begun yielding insights into issues ranging from control of granule core assembly, based on reverse genetic analysis of granule cargo, to questions about factors involved in granule biogenesis, based on random mutational approaches.
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Affiliation(s)
- Aaron P Turkewitz
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E 58th Street, Chicago IL 60637, USA.
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27
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Rosati G, Modeo L. Extrusomes in Ciliates: Diversification, Distribution, and Phylogenetic Implications. J Eukaryot Microbiol 2003; 50:383-402. [PMID: 14733430 DOI: 10.1111/j.1550-7408.2003.tb00260.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Exocytosis is, in all likelihood, an important communication method among microbes. Ciliates are highly differentiated and specialized micro-organisms for which versatile and/or sophisticated exocytotic organelles may represent important adaptive tools. Thus, in ciliates, we find a broad range of different extrusomes, i.e ejectable membrane-bound organelles. Structurally simple extrusomes, like mucocysts and cortical granules, are widespread in different taxa within the phylum. They play the roles in each case required for the ecological needs of the organisms. Then, we find a number of more elaborate extrusomes, whose distribution within the phylum is more limited, and in some way related to phylogenetic affinities. Herein we provide a survey of literature and our data on selected extrusomes in ciliates. Their morphology, distribution, and possible function are discussed. The possible phylogenetic implications of their diversity are considered.
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Affiliation(s)
- Giovanna Rosati
- Dipartimento di Etologia, Ecologia ed Evoluzione, Università degli Studi di Pisa, Pisa 56126, Italy.
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28
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Cole ES, Stuart KR, Marsh TC, Aufderheide K, Ringlien W. Confocal fluorescence microscopy for Tetrahymena thermophila. Methods Cell Biol 2003; 70:337-59. [PMID: 12512328 DOI: 10.1016/s0091-679x(02)70009-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- E S Cole
- Biology Department, St. Olaf College, Northfield, Minnesota 55057, USA
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Bradshaw NR, Chilcoat ND, Verbsky JW, Turkewitz AP. Proprotein processing within secretory dense core granules of Tetrahymena thermophila. J Biol Chem 2003; 278:4087-95. [PMID: 12435750 DOI: 10.1074/jbc.m207236200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the ciliate Tetrahymena thermophila, the polypeptides stored in secretory dense core granules (DCGs) are generated by proteolytic processing of precursors, and the mature products assemble as a crystal. Previous observations suggested that this maturation involves precise cleavage at distinct motifs by a small number of enzymes. To test these inferences, we analyzed the determinants for site-specific processing of pro-Grl1p (Granule lattice protein 1) by complete gene replacement with modified alleles. Contrary to the predictions of previous models, none of the component amino acids in a putative processing motif was necessary for targeted cleavage. Indeed, cleavage at a range of alternative positions near the native site was consistent with normal DCG assembly. Furthermore, substitution of other classes of processing site motifs did not perturb DCG structure or function. These results suggest that processing can be catalyzed by multiple proteases, for which substrate accessibility may be the prime determinant of site specificity. Consistent with this, inhibition of either subtilisin or cathepsin family proteases resulted in delayed processing of pro-Grl1p.
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Affiliation(s)
- Niels R Bradshaw
- Department of Molecular Genetics and Cell Biology, the University of Chicago, Illinois 60637, USA
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30
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Plattner H, Kissmehl R. Molecular Aspects of Membrane Trafficking in Paramecium. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 232:185-216. [PMID: 14711119 DOI: 10.1016/s0074-7696(03)32005-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Results achieved in the molecular biology of Paramecium have shed new light on its elaborate membrane trafficking system. Paramecium disposes not only of the standard routes (endoplasmic reticulum --> Golgi --> lysosomes or secretory vesicles; endo- and phagosomes --> lysosomes/digesting vacuoles), but also of some unique features, e.g. and elaborate phagocytic route with the cytoproct and membrane recycling to the cytopharynx, as well as the osmoregulatory system with multiple membrane fusion sites. Exocytosis sites for trichocysts (dense-core secretory vesicles), parasomal sacs (coated pits), and terminal cisternae (early endosomes) display additional regularly arranged predetermined fusion/fission sites, which now can be discussed on a molecular basis. Considering the regular, repetitive arrangements of membrane components, availability of mutants for complementation studies, sensitivity to gene silencing, and so on, Paramecium continues to be a valuable model system for analyzing membrane interactions. This review intends to set a new baseline for ongoing work along these lines.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, D-78457 Konstanz, Germany
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31
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Touz MC, Gottig N, Nash TE, Lujan HD. Identification and characterization of a novel secretory granule calcium-binding protein from the early branching eukaryote Giardia lamblia. J Biol Chem 2002; 277:50557-63. [PMID: 12354777 DOI: 10.1074/jbc.m202558200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Giardia lamblia is a flagellate protozoan that infects humans and other mammals and the most frequently isolated intestinal parasite worldwide. Giardia trophozoites undergo essential biological changes to survive outside the intestine of their host by differentiating into infective cysts. Cyst formation, or encystation, is considered one of the most primitive adaptive responses developed by eukaryotes early in evolution and crucial for the transmission of the parasite among susceptible hosts. During this process, proteins that will assemble into the extracellular cyst wall (CWP1 and CWP2) are transported to the cell surface within encystation-specific secretory vesicles (ESVs) by a developmentally regulated secretory pathway. Cyst wall proteins (CWPs) are maintained as a dense material inside the ESVs, but after exocytosis, they form the fibrillar matrix of the cyst wall. Little is known about the molecular mechanisms involved in granule biogenesis and discharge in Giardia, as well as the assembly of the extracellular wall. In this work, we provide evidences that a novel 54-kDa protein that exclusively localizes to the ESVs is induced during encystation similar to CWPs, proteolytically processed during granule maturation, and able to bind calcium in vitro. The gene encoding this molecule predicts a novel protein (called gGSP for G. lamblia Granule-specific Protein) without homology to any other protein reported in public databases. Nevertheless, it possesses characteristics of calcium-sequestering molecules of higher eukaryotes. Inhibition of gGSP expression abolishes cyst wall formation, suggesting that this secretory granule protein regulates Ca(2+)-dependent degranulation of ESVs during cyst wall formation.
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Affiliation(s)
- María C Touz
- Catedra de Bioquimica y Biologia Molecular, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, CP 5000 Córdoba, Argentina
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32
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Haddad A, Bowman GR, Turkewitz AP. New class of cargo protein in Tetrahymena thermophila dense core secretory granules. EUKARYOTIC CELL 2002; 1:583-93. [PMID: 12456006 PMCID: PMC117993 DOI: 10.1128/ec.1.4.583-593.2002] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Regulated exocytosis of dense core secretory granules releases biologically active proteins in a stimulus-dependent fashion. The packaging of the cargo within newly forming granules involves a transition: soluble polypeptides condense to form water-insoluble aggregates that constitute the granule cores. Following exocytosis, the cores generally disassemble to diffuse in the cell environment. The ciliates Tetrahymena thermophila and Paramecium tetraurelia have been advanced as genetically manipulatable systems for studying exocytosis via dense core granules. However, all of the known granule proteins in these organisms condense to form the architectural units of lattices that are insoluble both before and after exocytosis. Using an approach designed to detect new granule proteins, we have now identified Igr1p (induced during granule regeneration). By structural criteria, it is unrelated to the previously characterized lattice-forming proteins. It is distinct in that it is capable of dissociating from the insoluble lattice following secretion and therefore represents the first diffusible protein identified in ciliate granules.
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Affiliation(s)
- Alex Haddad
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA
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33
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Fillingham JS, Chilcoat ND, Turkewitz AP, Orias E, Reith M, Pearlman RE. Analysis of expressed sequence tags (ESTs) in the ciliated protozoan Tetrahymena thermophila. J Eukaryot Microbiol 2002; 49:99-107. [PMID: 12043965 DOI: 10.1111/j.1550-7408.2002.tb00350.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To assess the utility of expressed sequence tag (EST) sequencing as a method of gene discovery in the ciliated protozoan Tetrahymena thermophila, we have sequenced either the 5' or 3' ends of 157 clones chosen at random from two cDNA libraries constructed from the mRNA of vegetatively growing cultures. Of 116 total non-redundant clones, 8.6% represented genes previously cloned in Tetrahymena. Fifty-two percent had significant identity to genes from other organisms represented in GenBank, of which 92% matched human proteins. Intriguing matches include an opioid-regulated protein, a glutamate-binding protein for an NMDA-receptor, and a stem-cell maintenance protein. Eleven-percent of the non-Tetrahymena specific matches were to genes present in humans and other mammals but not found in other model unicellular eukaryotes, including the completely sequenced Saccharomyces cerevisiae. Our data reinforce the fact that Tetrahymena is an excellent unicellular model system for studying many aspects of animal biology and is poised to become an important model system for genome-scale gene discovery and functional analysis.
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34
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Bowman GR, Turkewitz AP. Analysis of a mutant exhibiting conditional sorting to dense core secretory granules in Tetrahymena thermophila. Genetics 2001; 159:1605-16. [PMID: 11779800 PMCID: PMC1461923 DOI: 10.1093/genetics/159.4.1605] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The formation of dense core granules (DCGs) requires both the sorting of granule contents from other secretory proteins and a postsorting maturation process. The Tetrahymena thermophila strain SB281 fails to synthesize DCGs, and previous analysis suggested that the defect lay at or near the sorting step. Because this strain represents one of the very few mutants in this pathway, we have undertaken a more complete study of the phenotype. Genetic epistasis analysis places the defect upstream of those in two other characterized Tetrahymena mutants. Using immunofluorescent detection of granule content proteins, as well as GFP tagging, we describe a novel cytoplasmic compartment to which granule contents can be sorted in growing SB281 cells. Cell fusion experiments indicate that this compartment is not a biosynthetic intermediate in DCG synthesis. Sorting in SB281 is strongly conditional with respect to growth. When cells are starved, the storage compartment is degraded and de novo synthesized granule proteins are rapidly secreted. The mutation in SB281 therefore appears to affect DCG synthesis at the level of both sorting and maturation.
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Affiliation(s)
- G R Bowman
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA
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35
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Mitchell KJ, Pinton P, Varadi A, Tacchetti C, Ainscow EK, Pozzan T, Rizzuto R, Rutter GA. Dense core secretory vesicles revealed as a dynamic Ca(2+) store in neuroendocrine cells with a vesicle-associated membrane protein aequorin chimaera. J Cell Biol 2001; 155:41-51. [PMID: 11571310 PMCID: PMC2150797 DOI: 10.1083/jcb.200103145] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of dense core secretory vesicles in the control of cytosolic-free Ca(2+) concentrations ([Ca(2+)](c)) in neuronal and neuroendocrine cells is enigmatic. By constructing a vesicle-associated membrane protein 2-synaptobrevin.aequorin chimera, we show that in clonal pancreatic islet beta-cells: (a) increases in [Ca(2+)](c) cause a prompt increase in intravesicular-free Ca(2+) concentration ([Ca(2+)]SV), which is mediated by a P-type Ca(2+)-ATPase distinct from the sarco(endo) plasmic reticulum Ca(2+)-ATPase, but which may be related to the PMR1/ATP2C1 family of Ca(2+) pumps; (b) steady state Ca(2+) concentrations are 3-5-fold lower in secretory vesicles than in the endoplasmic reticulum (ER) or Golgi apparatus, suggesting the existence of tightly bound and more rapidly exchanging pools of Ca(2+); (c) inositol (1,4,5) trisphosphate has no impact on [Ca(2+)](SV) in intact or permeabilized cells; and (d) ryanodine receptor (RyR) activation with caffeine or 4-chloro-3-ethylphenol in intact cells, or cyclic ADPribose in permeabilized cells, causes a dramatic fall in [Ca(2+)](SV). Thus, secretory vesicles represent a dynamic Ca(2+) store in neuroendocrine cells, whose characteristics are in part distinct from the ER/Golgi apparatus. The presence of RyRs on secretory vesicles suggests that local Ca(2+)-induced Ca(2+) release from vesicles docked at the plasma membrane could participate in triggering exocytosis.
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Affiliation(s)
- K J Mitchell
- Department of Biochemistry, University of Bristol, BS8 1TD Bristol, United Kingdom
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36
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Chilcoat ND, Elde NC, Turkewitz AP. An antisense approach to phenotype-based gene cloning in Tetrahymena. Proc Natl Acad Sci U S A 2001; 98:8709-13. [PMID: 11438705 PMCID: PMC37500 DOI: 10.1073/pnas.151243498] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report a pioneering approach using Tetrahymena thermophila that permits rapid identification of genes based on their null or hypomorphic phenotypes. This technique involves cell transformation with a library of plasmids that encode 26S ribosomal subunits containing short insertions. The insertions correspond to antisense sequences for a large number of genes. The majority of cells each acquires a single antisense sequence, which silences a single genomic locus. Because the insertion site within the ribosomal sequence is known, the silenced gene is easily amplified. We demonstrate that this approach can be used to identify genes required for dense core granule exocytosis.
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Affiliation(s)
- N D Chilcoat
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
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37
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Plattner H, Klauke N. Calcium in ciliated protozoa: sources, regulation, and calcium-regulated cell functions. INTERNATIONAL REVIEW OF CYTOLOGY 2001; 201:115-208. [PMID: 11057832 DOI: 10.1016/s0074-7696(01)01003-8] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In ciliates, a variety of processes are regulated by Ca2+, e.g., exocytosis, endocytosis, ciliary beat, cell contraction, and nuclear migration. Differential microdomain regulation may occur by activation of specific channels in different cell regions (e.g., voltage-dependent Ca2+ channels in cilia), by local, nonpropagated activation of subplasmalemmal Ca stores (alveolar sacs), by different sensitivity thresholds, and eventually by interplay with additional second messengers (cilia). During stimulus-secretion coupling, Ca2+ as the only known second messenger operates at approximately 5 microM, whereby mobilization from alveolar sacs is superimposed by "store-operated Ca2+ influx" (SOC), to drive exocytotic and endocytotic membrane fusion. (Content discharge requires binding of extracellular Ca2+ to some secretory proteins.) Ca2+ homeostasis is reestablished by binding to cytosolic Ca2+-binding proteins (e.g., calmodulin), by sequestration into mitochondria (perhaps by Ca2+ uniporter) and into endoplasmic reticulum and alveolar sacs (with a SERCA-type pump), and by extrusion via a plasmalemmal Ca2+ pump and a Na+/Ca2+ exchanger. Comparison of free vs total concentration, [Ca2+] vs [Ca], during activation, using time-resolved fluorochrome analysis and X-ray microanalysis, respectively, reveals that altogether activation requires a calcium flux that is orders of magnitude larger than that expected from the [Ca2+] actually required for local activation.
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Affiliation(s)
- H Plattner
- Department of Biology, University of Konstanz, Germany
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38
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Vayssié L, Garreau de Loubresse N, Sperling L. Growth and form of secretory granules involves stepwise assembly but not differential sorting of a family of secretory proteins in Paramecium. J Cell Sci 2001; 114:875-86. [PMID: 11181171 DOI: 10.1242/jcs.114.5.875] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paramecium trichocysts are voluminous secretory vesicles consisting of a spindle-shaped body surmounted by a tip that serves to anchor them at exocytotic sites in the plasma membrane. This constrained shape is conferred by the proteins stored in the vesicles, which form an insoluble three-dimensional crystalline array. The constituent polypeptides (Trichocyst Matrix Proteins, TMPs), which assemble during trichocyst biogenesis, are produced by proteolytic processing of soluble proproteins encoded by a large multigene family. In order to investigate the functional significance of the TMP multigene family, which assures the synthesis of a mixture of related polypeptides, we have designed synthetic genes for heterologous expression of three different mature polypeptides, which were used to obtain sequence-specific rabbit antisera. We used these antisera to carry out immunolocalization experiments with wild-type trichocysts at different stages of development and found that the trichocyst matrix consists of two concentric layers containing different TMPs, and that the assembly of each layer corresponds to a distinct phase of trichocyst growth. Examination of mutant trichocysts created by targeted gene silencing of different TMP genes showed that the layer containing the products of the silenced genes is specifically affected, as are all subsequently assembled parts of the structure, consistent with an ordered assembly pathway. This stepwise assembly is not controlled by differential sorting of the TMPs, as single and double label experiments provided evidence that the different TMPs are delivered together to post-Golgi vesicles and developing trichocysts. We present a model for trichocyst biogenesis in which TMP assembly is controlled by protein processing.
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Affiliation(s)
- L Vayssié
- Centre de Génétique Moléculaire, CNRS, France
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39
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Turkewitz AP, Chilcoat ND, Haddad A, Verbsky JW. Regulated protein secretion in Tetrahymena thermophila. Methods Cell Biol 1999; 62:347-62. [PMID: 10503203 DOI: 10.1016/s0091-679x(08)61542-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Affiliation(s)
- A P Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637, USA
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40
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Hai B, Gaertig J, Gorovsky MA. Knockout heterokaryons enable facile mutagenic analysis of essential genes in Tetrahymena. Methods Cell Biol 1999; 62:513-31. [PMID: 10503215 DOI: 10.1016/s0091-679x(08)61554-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- B Hai
- Department of Biology, University of Rochester, New York 14627, USA
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41
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Gaertig J, Kapler G. Transient and stable DNA transformation of Tetrahymena thermophila by electroporation. Methods Cell Biol 1999; 62:485-500. [PMID: 10503213 DOI: 10.1016/s0091-679x(08)61552-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- J Gaertig
- Department of Cellular Biology, University of Georgia, Athens 30602, USA
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42
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Affiliation(s)
- J Frankel
- Department of Biological Sciences, University of Iowa, Iowa City 52242, USA
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43
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Lee S, Wisniewski JC, Dentler WL, Asai DJ. Gene knockouts reveal separate functions for two cytoplasmic dyneins in Tetrahymena thermophila. Mol Biol Cell 1999; 10:771-84. [PMID: 10069817 PMCID: PMC25201 DOI: 10.1091/mbc.10.3.771] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In many organisms, there are multiple isoforms of cytoplasmic dynein heavy chains, and division of labor among the isoforms would provide a mechanism to regulate dynein function. The targeted disruption of somatic genes in Tetrahymena thermophila presents the opportunity to determine the contributions of individual dynein isoforms in a single cell that expresses multiple dynein heavy chain genes. Substantial portions of two Tetrahymena cytoplasmic dynein heavy chain genes were cloned, and their motor domains were sequenced. Tetrahymena DYH1 encodes the ubiquitous cytoplasmic dynein Dyh1, and DYH2 encodes a second cytoplasmic dynein isoform, Dyh2. The disruption of DYH1, but not DYH2, resulted in cells with two detectable defects: 1) phagocytic activity was inhibited, and 2) the cells failed to distribute their chromosomes correctly during micronuclear mitosis. In contrast, the disruption of DYH2 resulted in a loss of regulation of cell size and cell shape and in the apparent inability of the cells to repair their cortical cytoskeletons. We conclude that the two dyneins perform separate tasks in Tetrahymena.
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Affiliation(s)
- S Lee
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA
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44
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Affiliation(s)
- G A Rutter
- Department of Biochemistry, School of Medical Sciences, University of Bristol, United Kingdom.
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45
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Scheenen WJ, Wollheim CB, Pozzan T, Fasolato C. Ca2+ depletion from granules inhibits exocytosis. A study with insulin-secreting cells. J Biol Chem 1998; 273:19002-8. [PMID: 9668080 DOI: 10.1074/jbc.273.30.19002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The secretory compartment is characterized by low luminal pH and high Ca2+ content. Previous studies in several cell types have shown that the size of the acidic Ca2+ pool, of which secretory granules represent a major portion, could be estimated by applying first a Ca2+ ionophore followed by agents that collapse acidic pH gradients. In the present study we have employed this protocol in the insulin-secreting cell line Ins-1 to determine whether the Ca2+ trapped in the secretory granules plays a role in exocytosis. The results demonstrate that a high proportion of ionophore-mobilizable Ca2+ in Ins-1 cells resides in the acidic compartment. The latter pool, however, does not significantly contribute to the [Ca2+]i changes elicited by thapsigargin and the inositol trisphosphate-producing agonist carbachol. By monitoring membrane capacitance at the single cell level or by measuring insulin release in cell populations, we show that Ca2+ mobilization from nonacidic Ca2+ pools causes a profound and long lasting increase in depolarization-induced secretion, whereas breakdown of granule pH had no significant effect. In contrast, releasing Ca2+ from the acidic pool markedly reduces secretion. It is suggested that a high Ca2+ concentration in the secretory compartment is needed to sustain optimal exocytosis.
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Affiliation(s)
- W J Scheenen
- Department of Biomedical Sciences, Consiglio Nazionale delle Ricerche, Center of Biomembranes, University of Padova, Via G. Colombo 3, 35100 Padova Italy.
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46
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Arvan P, Castle D. Sorting and storage during secretory granule biogenesis: looking backward and looking forward. Biochem J 1998; 332 ( Pt 3):593-610. [PMID: 9620860 PMCID: PMC1219518 DOI: 10.1042/bj3320593] [Citation(s) in RCA: 409] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Secretory granules are specialized intracellular organelles that serve as a storage pool for selected secretory products. The exocytosis of secretory granules is markedly amplified under physiologically stimulated conditions. While granules have been recognized as post-Golgi carriers for almost 40 years, the molecular mechanisms involved in their formation from the trans-Golgi network are only beginning to be defined. This review summarizes and evaluates current information about how secretory proteins are thought to be sorted for the regulated secretory pathway and how these activities are positioned with respect to other post-Golgi sorting events that must occur in parallel. In the first half of the review, the emerging role of immature secretory granules in protein sorting is highlighted. The second half of the review summarizes what is known about the composition of granule membranes. The numerous similarities and relatively limited differences identified between granule membranes and other vesicular carriers that convey products to and from the plasmalemma, serve as a basis for examining how granule membrane composition might be established and how its unique functions interface with general post-Golgi membrane traffic. Studies of granule formation in vitro offer additional new insights, but also important challenges for future efforts to understand how regulated secretory pathways are constructed and maintained.
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Affiliation(s)
- P Arvan
- Division of Endocrinology and Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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47
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Klauke N, Kissmehl R, Plattner H, Haga N, Watanabe T. An exocytotic mutant of Paramecium caudatum: membrane fusion without secretory contents release. Cell Calcium 1998; 23:349-60. [PMID: 9681197 DOI: 10.1016/s0143-4160(98)90030-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
This is a detailed characterization of a secretory mutant incapable of releasing secretory contents despite normal exocytotic membrane fusion performance. Trichocyst non-discharge strain tnd1 of Paramecium caudatum and its wildtype (wt) both show a transient cortical [Ca2+]i increase and exocytotic membrane fusion in response to the polyamine secretagogue, aminoethyldextran (AED), or to caffeine. tnd1 cells frequently display spontaneous Ca2+ signals parallelled by spontaneous exocytotic membrane fusion. This remains undetected, unless the trichocyst matrix is shown to be freely accessible to the inert, non-membrane permeable fluorochrome, F2FITC, from the outside. In these tnd1 cells, spontaneous and AED- or caffeine-induced membrane fusion, always without contents expulsion by decondensation (i.e. several-fold stretching), is ascertained by electron microscopy. Exocytotic openings, with condensed trichocysts retained, may persist for hours without impairing cells. Trichocyst decondensation normally requires micromolar [Ca2+]e, but an increase to 10 mM has no effect on tnd1 trichocyst expansion in vivo or in vitro (when isolated and exposed to ionophore A23187 + Ca2+). Paracrystalline packing of the major secretory components (trichynins) does occur, despite incomplete proteolytic precursor processing (according to SDS-PAGE). However, 45Ca(2+)-binding by secretory components is considerably reduced--the likely cause of the non-discharge phenotype. Our findings imply significant untriggered membrane fusion in a system normally following the triggered pathway and clear separation of exocytotic membrane fusion from any later Ca(2+)-dependent steps of the secretory cycle.
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Affiliation(s)
- N Klauke
- Department of Biology, University of Konstanz, Germany
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48
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Verbsky JW, Turkewitz AP. Proteolytic processing and Ca2+-binding activity of dense-core vesicle polypeptides in Tetrahymena. Mol Biol Cell 1998; 9:497-511. [PMID: 9450970 PMCID: PMC25279 DOI: 10.1091/mbc.9.2.497] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Formation and discharge of dense-core secretory vesicles depend on controlled rearrangement of the core proteins during their assembly and dispersal. The ciliate Tetrahymena thermophila offers a simple system in which the mechanisms may be studied. Here we show that most of the core consists of a set of polypeptides derived proteolytically from five precursors. These share little overall amino acid identity but are nonetheless predicted to have structural similarity. In addition, sites of proteolytic processing are notably conserved and suggest that specific endoproteases as well as carboxypeptidase are involved in core maturation. In vitro binding studies and sequence analysis suggest that the polypeptides bind calcium in vivo. Core assembly and postexocytic dispersal are compartment-specific events. Two likely regulatory factors are proteolytic processing and exposure to calcium. We asked whether these might directly influence the conformations of core proteins. Results using an in vitro chymotrypsin accessibility assay suggest that these factors can induce sequential structural rearrangements. Such progressive changes in polypeptide folding may underlie the mechanisms of assembly and of rapid postexocytic release. The parallels between dense-core vesicles in different systems suggest that similar mechanisms are widespread in this class of organelles.
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Affiliation(s)
- J W Verbsky
- Department of Molecular Genetics & Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA
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49
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Orias E. Mapping the germ-line and somatic genomes of a ciliated protozoan, Tetrahymena thermophila. Genome Res 1998; 8:91-9. [PMID: 9477337 DOI: 10.1101/gr.8.2.91] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ciliates are among the very few eukaryotes in which the powers of molecular biology, conventional genetics, and microbial methodology can be synergistically combined. Because ciliates also are distant relatives of vertebrates, fungi, and plants, the sequencing of a ciliate genome will be of import to our understanding of eukaryotic biology. Tetrahymena thermophila is the only ciliate in which a systematic genetic mapping of DNA polymorphisms has begun. Tetrahymena has many biological features that make it a specially or uniquely useful experimental system for fundamental research in cell and molecular biology and for biotechnological applications. A key factor in the usefulness of Tetrahymena is the speed, facility, and versatility with which it can be cultivated under a wide range of nutrient conditions, temperature, and scale. This article describes the progress made in genetically and physically mapping the genomes of T. thermophila: the micronuclear (germ-line) genome, which is not transcriptionally expressed, and the macronuclear (somatic) fragmented genome, which is actively expressed and determines the cell's phenotype.
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Affiliation(s)
- E Orias
- Department of Molecular, Cellular, and Developmental Biology, University of California at Santa Barbara (UCSB), Santa Barbara, California 93106, USA.
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50
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Melia SM, Cole ES, Turkewitz AP. Mutational analysis of regulated exocytosis in Tetrahymena. J Cell Sci 1998; 111 ( Pt 1):131-40. [PMID: 9394019 DOI: 10.1242/jcs.111.1.131] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genetic analysis of regulated exocytosis can be accomplished in ciliates, since mutants defective in stimulus-dependent secretion of dense-core vesicles can be identified. In Tetrahymena thermophila, secretion in wild-type cells can result in their encapsulation by the proteins released from vesicle cores. Cells with defects in secretion were isolated from mutagenized homozygous cells that were generated using a highly efficient method. Screening was based both on a visual assay for encapsulation, and on a novel panning step using differential centrifugation to take advantage of the selective mobility of mutants that fail to encapsulate upon stimulation. 18 mutants with defects in several ordered steps have been identified. Defects in a set of these could be localized to three stages: granule formation, transport to cell surface docking sites, and exocytosis itself. Mutants with defects in this last stage can be ordered into successive steps based on several criteria, including their responsiveness to multiple secretagogues and Ca2+ ionophores. The results of both somatic and genetic complementation on selected pairs also help to characterize the defective factors.
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Affiliation(s)
- S M Melia
- Department of Molecular Genetics, University of Chicago, Chicago, IL 60637, USA
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