Molecular Aspects of Membrane Trafficking in Paramecium

Plattner, Helmut; Kissmehl, Roland

doi:10.1016/s0074-7696(03)32005-4

Cited by 29 publications

(36 citation statements)

References 167 publications

(161 reference statements)

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“…Analysis of Paramecium cells appears to be rewarding as they display a most elaborate membranetrafficking system (Fig. 1), with distinct, predictable pathways (Allen and Fok, 1983;Allen and Fok, 2000;Fok and Allen, 1988;Fok and Allen, 1990;Plattner and Kissmehl, 2003) in which the different actin isoforms participate, as we now show. In the present work we combined the different techniques to establish a functional and topological overview of actin diversification in a Paramecium cell.…”

Section: Introductionmentioning

confidence: 54%

“…6D), which can easily be identified as 'parasomal sacs'. They correspond to stationary sites of constitutive exocytosis and coated pit endocytosis (Allen and Fok, 2000;Plattner and Kissmehl, 2003).…”

Section: Actin8-1mentioning

confidence: 99%

“…The trafficking scheme is based on published reviews (Fok and Allen, 1990;Allen and Fok, 2000;Plattner and Kissmehl, 2003). Actin distribution is based mainly on the present data obtained with GFP localization in vivo and with antibody labeling, but also takes into account data from previous work (Tiggemann and Plattner, 1981;Kersken et al, 1986a;Kersken et al, 1986b;Kissmehl et al, 2004).…”

Section: Nuclear and Cell Divisionmentioning

confidence: 99%

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A broad spectrum of actin paralogs inParamecium tetraureliacells display differential localization and function

Sehring

Reiner

Mansfeld

et al. 2007

Journal of Cell Science

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To localize the different actin paralogs found in Paramecium and to disclose functional implications, we used overexpression of GFP-fusion proteins and antibody labeling, as well as gene silencing. Several isoforms are associated with food vacuoles of different stages. GFP-actin either forms a tail at the lee side of the organelle, or it is vesicle bound in a homogenous or in a speckled arrangement, thus reflecting an actin-based mosaic of the phagosome surface appropriate for association and/or dissociation of other vesicles upon travel through the cell. Several paralogs occur in cilia. A set of actins is found in the cell cortex where actin outlines the regular surface pattern. Labeling of defined structures of the oral cavity is due to other types of actin, whereas yet more types are distributed in a pattern suggesting association with the numerous Golgi fields. A substantial fraction of actins is associated with cytoskeletal elements that are known to be composed of other proteins. Silencing of the respective actin genes or gene subfamilies entails inhibitory effects on organelles compatible with localization studies. Knock down of the actin found in the cleavage furrow abolishes cell division, whereas silencing of other actin genes alters vitality, cell shape and swimming behavior.

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Section: Introductionmentioning

confidence: 54%

Section: Actin8-1mentioning

confidence: 99%

Section: Nuclear and Cell Divisionmentioning

confidence: 99%

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A broad spectrum of actin paralogs inParamecium tetraureliacells display differential localization and function

Sehring

Reiner

Mansfeld

et al. 2007

Journal of Cell Science

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“…Like those organisms, Paramecium has to perform within one cell all functions that are normally shared between different cell types in multicellular organisms. Accordingly complex are the cytoskeletal anatomy (1), food uptake and processing (20), and membrane trafficking pathways (47). This complexity is mirrored in the mere size of the genome, with ϳ39,500 protein-coding genes (8).…”

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confidence: 99%

Distinct Subcellular Localization of a Group of Synaptobrevin-Like SNAREs in Paramecium tetraurelia and Effects of Silencing SNARE-Specific Chaperone NSF

et al. 2010

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We have identified new synaptobrevin-like SNAREs and localized the corresponding gene products with green fluorescent protein (GFP)-fusion constructs and specific antibodies at the light and electron microscope (EM) levels. These SNAREs, named Paramecium tetraurelia synaptobrevins 8 to 12 (PtSyb8 to PtSyb12), showed mostly very restricted, specific localization, as they were found predominantly on structures involved in endoor phagocytosis. In summary, we found PtSyb8 and PtSyb9 associated with the nascent food vacuole, PtSyb10 near the cell surface, at the cytostome, and in close association with ciliary basal bodies, and PtSyb11 on early endosomes and on one side of the cytostome, while PtSyb12 was found in the cytosol. PtSyb4 and PtSyb5 (identified previously) were localized on small vesicles, PtSyb5 probably being engaged in trichocyst (dense core secretory vesicle) processing. PtSyb4 and PtSyb5 are related to each other and are the furthest deviating of all SNAREs identified so far. Because they show no similarity with any other R-SNAREs outside ciliates, they may represent a ciliate-specific adaptation. PtSyb10 forms small domains near ciliary bases, and silencing slows down cell rotation during depolarization-induced ciliary reversal. NSF silencing supports a function of cell surface SNAREs by revealing vesicles along the cell membrane at sites normally devoid of vesicles. The distinct distributions of these SNAREs emphasize the considerable differentiation of membrane trafficking, particularly along the endo-/phagocytic pathway, in this protozoan.

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“…Paramecium, which must perform all of the autonomous functions of an entire organism, possesses highly diversified membrane trafficking pathways (53). P. tetraurelia is capable of a fast synchronous release of dense core vesicles, defensive organelles called "trichocysts," that has striking similarities to dense core vesicle exocytosis of neuroendocrine cells (52,74).…”

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Molecular Identification of a SNAP-25-Like SNARE Protein inParamecium

et al. 2008

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Using database searches of the completed Paramecium tetraurelia macronuclear genome with the metazoan SNAP-25 homologues, we identified a single 21-kDa Qb/c-SNARE in this ciliated protozoan, named P. tetraurelia SNAP (PtSNAP), containing the characteristic dual heptad repeat SNARE motifs of SNAP-25. The presence of only a single Qb/c class SNARE in P. tetraurelia is surprising in view of the multiple genome duplications and the high number of SNAREs found in other classes of this organism. As inferred from the subcellular localization of a green fluorescent protein (GFP) fusion construct, the protein is localized on a variety of intracellular membranes, and there is a large soluble pool of PtSNAP. Similarly, the PtSNAP that is detected with a specific antibody in fixed cells is associated with a number of intracellular membrane structures, including food vacuoles, the contractile vacuole system, and the sites of constitutive endo-and exocytosis. Surprisingly, using gene silencing, we could not assign a role to PtSNAP in the stimulated exocytosis of dense core vesicles (trichocysts), but we found an increased number of food vacuoles in PtSNAP-silenced cells. In conclusion, we identify PtSNAP as a Paramecium homologue of metazoan SNAP-25 that shows several divergent features, like resistance to cleavage by botulinum neurotoxins.Membrane trafficking in eukaryotic cells involves budding of vesicles from a donor compartment and transport to and fusion with the acceptor compartment. The soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are of central importance in the mediation of membrane fusions (32). The crystal structure of the synaptic SNARE complex has been resolved (70). The ternary synaptic SNARE complex consists of the SNARE motifs of synaptobrevin-2 (VAMP2) and syntaxin-1A and the two SNARE motifs from the synaptosome-associated protein of 25 kDa (SNAP-25). Structures of different SNARE complexes revealed a highly conserved four-helix structure, with the difference that the positions of the two SNARE motifs from SNAP-25 can be contributed by two different SNARE proteins (7). The highly conserved pattern of SNARE pairing has led to the so-called 3Q-plus-1R rule (21). According to this rule, fusogenic SNARE complexes always contain three SNARE motifs containing a glutamine residue in the center of the SNARE motif (Q-SNARE) and one SNARE displaying an arginine at the same position (R-SNARE). Furthermore, Qa-, Qb-, Qc-, and R-SNAREs can be recognized by specific sequence features (40).Identification of the SNARE components of the synaptic SNARE complex and functional analysis have been greatly facilitated by the availability of specific inhibitors, e.g., by Clostridium botulinum neurotoxins (BoNTs), that specifically cleave certain neuronal SNAREs (46). BoNTs are zinc-dependent proteases which, by cleaving SNARE proteins, inhibit neurotransmitter release. The structural basis for the specificity of SNAP-25 cleavage by BoNT/A and BoNT/E has been solved, and the interacting amino acid...

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Molecular Aspects of Membrane Trafficking in Paramecium

Cited by 29 publications

References 167 publications

A broad spectrum of actin paralogs inParamecium tetraureliacells display differential localization and function

A broad spectrum of actin paralogs inParamecium tetraureliacells display differential localization and function

Distinct Subcellular Localization of a Group of Synaptobrevin-Like SNAREs in Paramecium tetraurelia and Effects of Silencing SNARE-Specific Chaperone NSF

Molecular Identification of a SNAP-25-Like SNARE Protein inParamecium

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