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Plattner H. Ciliate Research. From Myth to Trendsetting Science. J Eukaryot Microbiol 2022; 69:e12926. [PMID: 35608570 DOI: 10.1111/jeu.12926] [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: 02/21/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/28/2022]
Abstract
This special issue of the Journal of Eukaryotic Microbiology (JEM) summarizes achievements obtained by generations of researchers with ciliates in widely different disciplines. In fact, ciliates range among the first cells seen under the microscope centuries ago. Their beauty made them an object of scientia amabilis and their manifold reactions made them attractive for college experiments and finally challenged causal analyses at the cellular level. Some of this work was honored by a Nobel Prize. Some observations yielded a baseline for additional novel discoveries, occasionally facilitated by specific properties of some ciliates. This also offers some advantage in the exploration of closely related parasites (malaria). Articles contributed here by colleagues from all over the world encompass a broad spectrum of ciliate life, from genetics to evolution, from molecular cell biology to ecology, from intercellular signaling to epigenetics etc. This introductory chapter, largely based on my personal perception, aims at integrating work presented in this special issue of JEM into a broader historical context up to current research.
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Abstract
Single-celled microorganisms are important in ecosystems, and their behaviors impact the Earth’s environments. To survive in harsh environments, these organisms frequently act as though exercising discretion. How do they achieve such intelligent behaviors? In this work, we focused on the accumulation of ciliates on solid/fluid interfaces, where they can obtain sufficient nutrients and a stable environment. This phenomenon is not described in the standard hydrodynamics of microswimmers. Our experiment and simulation revealed that simple principles, the anisotropic shape of the cell and the mechanosensing nature of cilia, induce the accumulation of ciliates on solid/fluid interfaces. The contribution of our work is that a simple response of the cellular apparatus and fluid dynamics explain the apparently clever behavior of ciliates. An important habit of ciliates, namely, their behavioral preference for walls, is revealed through experiments and hydrodynamic simulations. A simple mechanical response of individual ciliary beating (i.e., the beating is stalled by the cilium contacting a wall) can solely determine the sliding motion of the ciliate along the wall and result in a wall-preferring behavior. Considering ciliate ethology, this mechanosensing system is likely an advantage in the single cell’s ability to locate nutrition. In other words, ciliates can skillfully use both the sliding motion to feed on a surface and the traveling motion in bulk water to locate new surfaces according to the single “swimming” mission.
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Plattner H. Signalling in ciliates: long- and short-range signals and molecular determinants for cellular dynamics. Biol Rev Camb Philos Soc 2015; 92:60-107. [PMID: 26487631 DOI: 10.1111/brv.12218] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/28/2015] [Accepted: 08/21/2015] [Indexed: 12/30/2022]
Abstract
In ciliates, unicellular representatives of the bikont branch of evolution, inter- and intracellular signalling pathways have been analysed mainly in Paramecium tetraurelia, Paramecium multimicronucleatum and Tetrahymena thermophila and in part also in Euplotes raikovi. Electrophysiology of ciliary activity in Paramecium spp. is a most successful example. Established signalling mechanisms include plasmalemmal ion channels, recently established intracellular Ca2+ -release channels, as well as signalling by cyclic nucleotides and Ca2+ . Ca2+ -binding proteins (calmodulin, centrin) and Ca2+ -activated enzymes (kinases, phosphatases) are involved. Many organelles are endowed with specific molecules cooperating in signalling for intracellular transport and targeted delivery. Among them are recently specified soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), monomeric GTPases, H+ -ATPase/pump, actin, etc. Little specification is available for some key signal transducers including mechanosensitive Ca2+ -channels, exocyst complexes and Ca2+ -sensor proteins for vesicle-vesicle/membrane interactions. The existence of heterotrimeric G-proteins and of G-protein-coupled receptors is still under considerable debate. Serine/threonine kinases dominate by far over tyrosine kinases (some predicted by phosphoproteomic analyses). Besides short-range signalling, long-range signalling also exists, e.g. as firmly installed microtubular transport rails within epigenetically determined patterns, thus facilitating targeted vesicle delivery. By envisaging widely different phenomena of signalling and subcellular dynamics, it will be shown (i) that important pathways of signalling and cellular dynamics are established already in ciliates, (ii) that some mechanisms diverge from higher eukaryotes and (iii) that considerable uncertainties still exist about some essential aspects of signalling.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, PO Box M625, 78457, Konstanz, Germany
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Simon M, Plattner H. Unicellular Eukaryotes as Models in Cell and Molecular Biology. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 309:141-98. [DOI: 10.1016/b978-0-12-800255-1.00003-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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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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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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Marti M, Hehl AB. Encystation-specific vesicles in Giardia: a primordial Golgi or just another secretory compartment? Trends Parasitol 2004; 19:440-6. [PMID: 14519581 DOI: 10.1016/s1471-4922(03)00201-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Matthias Marti
- Division of Infection and Immunity, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia
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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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Karava V, Fasia L, Siafaka-Kapadai A. Anandamide amidohydrolase activity, released in the medium by Tetrahymena pyriformis. Identification and partial characterization. FEBS Lett 2001; 508:327-31. [PMID: 11728445 DOI: 10.1016/s0014-5793(01)03095-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Anandamide, an endogenous cannabinoid receptor ligand, was rapidly metabolized by Tetrahymena pyriformis in vivo. Metabolic products were mainly phospholipids as well as neutral lipids, including small amounts of free arachidonic acid. Anandamide amidohydrolase activity was detected in the culture medium by the release of [3H]arachidonic acid from [3H]anandamide, in a time- and concentration-dependent manner. Kinetic experiments demonstrated that the released enzyme had an apparent K(m) of 3.7 microM and V(max) 278 pmol/min/mg protein. Amidohydrolase activity was maximal at pH 9-10, was abolished by phenylmethylsulfonyl fluoride and was Ca(2+)- and Mg(2+)-independent. Thus, T. pyriformis is capable of hydrolyzing anandamide in vivo and releasing amidohydrolase activity.
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Affiliation(s)
- V Karava
- Department of Chemistry (Biochemistry), University of Athens, Panepistimioupolis, 15771, Athens, Greece
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Tazawa M, Ohtsuki M, Sumi-Ichinose C, Shiraishi H, Kuroda R, Hagino Y, Nakashima S, Nozawa Y, Ichinose H, Nagatsu T, Nomura T. GTP cyclohydrolase I from Tetrahymena pyriformis: cloning of cDNA and expression. Comp Biochem Physiol B Biochem Mol Biol 2000; 127:65-73. [PMID: 11126753 DOI: 10.1016/s0305-0491(00)00239-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
A full-length cDNA clone for GTP cyclohydrolase I (EC 3.5.4.16) was isolated from a Tetrahymena pyriformis cDNA library by plaque hybridization. The nucleotide sequence determination revealed that the length of the cDNA insert was 1516 bp. The coding region encoded a protein of 223 amino acid residues with a calculated molecular mass of 25 416 Da. The deduced amino acid sequence of Tetrahrymena GTP cyclohydrolase I showed sequence identity with that of Escherichia coli (55%). The identity of T. pyriformis GTP cyclohydrolase I with sequences of Dictyostelium discoideum, Saccharomyces cerevisiae, Drosophila melanogaster, mouse, rat, and human enzymes was less marked and was 30, 30, 25, 28, 28, and 27%, respectively. RNA blot analysis showed a single mRNA species of 2.1 kb in this protozoan. The mRNA level of GTP cyclohydrolase I increased during synchronous cell division induced by intermittent heat treatment. The results suggest that the mRNA expression is associated with the cell cycle of T. pyriformis.
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Affiliation(s)
- M Tazawa
- Department of Pharmacology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
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Leondaritis G, Galanopoulou D. Characterization of inositol phospholipids and identification of a mastoparan-induced polyphosphoinositide response in Tetrahymena pyriformis. Lipids 2000; 35:525-32. [PMID: 10907787 DOI: 10.1007/s11745-000-552-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The unicellular eukaryote Tetrahymena is a popular model for the study of lipid metabolism. Less attention, however, has been given to the inositol phospholipids of the cell, although it is known that this class of lipids plays an important role in eukaryotic cell signaling. Tetrahymena pyriformis phosphatidylinositol was isolated, purified, and characterized by proton nuclear magnetic resonance analysis and [2-(3)H]myoinositol labeling. Labeling was also used for polyphosphoinositide (phosphatidylinositol phosphate and phosphatidylinositol bisphosphate) identification. Tetrahymena inositol phospholipids were found to belong to the diacylglycerol group, although major Tetrahymena phospholipids, phosphatidylcholine and aminoethylphosphonoglycerides, have been found to be mainly alkylacylglyceroderivatives. Further characterization of Tetrahymena phosphatidylinositol by gas chromatographic analysis indicated that 80% of fatty acids were myristic acid and palmitic acid. This is also in contrast to the fatty acid profile of Tetrahymena phosphatidylcholine and phosphatidylethanolamine, with respect both to the fatty acid length and degree of unsaturation, and may indicate that specific diacylglycerol species are connected with the phosphatidylinositol metabolism in this cell. Treatment of [3H]inositol-labeled Tetrahymena cells with mastoparan, a G-protein-activating peptide, induced changes in the polyphosphoinositide levels, suggesting that inositol phospholipids may form in Tetrahymena a functional signaling system similar to that of higher eukaryotes. Addition of 10 microM mastoparan resulted in a rapid and transient increase in [3H]phosphatidylinositol phosphate followed by a decrease in [3H]phosphatidylinositol bisphosphate. Similar changes in lipids have been reported when phosphoinositide-phospholipase C pathway is activated in both animal and plant cells.
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Affiliation(s)
- G Leondaritis
- Department of Chemistry, University of Athens, Greece
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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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Affiliation(s)
- J Frankel
- Department of Biological Sciences, University of Iowa, Iowa City 52242, USA
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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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