The Vacuolar‐ATPase of <i>Paramecium multimicronucleatum</i>: Gene Structure of the B Subunit and the Dynamics of the V‐ATPase‐rich Osmoregulatory Membranes

Fok, Agnes K.; Yamauchi, Kiyoshi; Ishihara, Akinori; Aihara, Masahiko; Ishida, Masaki; Allen, Richard D.

doi:10.1111/j.1550-7408.2002.tb00521.x

Cited by 22 publications

(24 citation statements)

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“…Identification of c-subunits (proteolipids) of V 0 and Fsubunits of V 1 in P. tetraurelia Only one gene of the Paramecium V-ATPase has been previously described, encoding the B-subunit of V 1 of P. multimicronucleatum (Fok et al, 2002). In a pilot genome survey of P. tetraurelia (Dessen et al, 2001), a clone containing a sequence highly similar to a c-subunit (proteolipid) was identified, thus opening the possibility of gaining molecular knowledge on V 0 -subunits.…”

Section: Resultsmentioning

confidence: 99%

The vacuolar proton-ATPase plays a major role in several membrane-bounded organelles inParamecium

Wassmer

Froissard

Plattner

et al. 2005

Journal of Cell Science

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IntroductionThe vacuolar-proton-ATPase (V-ATPase) translocates protons across membranes against their electrochemical potential through ATP hydrolysis. The V-ATPase is responsible for the acidification of organelles like phagosomes, lysosomes, early endosomes, the trans-Golgi-network, dense core secretory granules and vacuoles of plants (Sun-Wada et al., 2003a;Nelson, 2003;Kluge et al., 2003). In some specialized cells of higher organisms, the enzyme is also localized in the plasma membrane and serves to secrete protons to the extracellular space. For example, the acidification of the extracellular matrix by proton secretion of osteoclasts is important for bone resorption (Toyomura et al., 2003). An important aspect of the proton translocation by the V-ATPase is the creation of an electrochemical potential that can be used for secondary active transport of ions. This mechanism is used in neuronal cells, where the neurotransmitters glutamate or γ-amino-butyric-acid are concentrated in the lumen of synaptic vesicles (Roseth et al., 1995;Fonnum et al., 1998) and in chromaffin granules (Apps, 1997).The V-ATPase is composed of two subcomplexes: the cytosolic V 1 -sector, where ATP binding and hydrolysis takes place; and a transmembranous V 0 -sector, through which protons are tunneled. The holoenzyme in Saccharomyces cerevisiae consists of 14 different subunits (Kawasaki-Nishi et al., 2004;Sambade and Kane, 2004). V 1 contains subunits A-H in the stoichiometry A 3 B 3 CDEFG 2 H 1-2 . V 0 is formed by the subunits a, c, c′, c′′, d and e in a stoichiometry of ade x c 4 c′c′′. The V-ATPase was shown to act by a rotationary mechanism similar to that of the structurally related F-ATPase (Imamura et al., 2003).The enzyme activity can be regulated by reversible dissociation of V 1 from V 0 . It was found in yeast that the ratio of assembled/disassembled enzyme is strongly influenced by the culture conditions. Most of the V 1 -domains dissociate from their V 0 counterparts at vacuoles in yeast when glucose is depleted in the medium (Kane and Smardon, 2003). Whether other physiological conditions exist that lead to a dissociation of the enzyme is unclear.Apart from its enzymatic action as a proton pump, the V 0 -subcomplex of the V-ATPase was found to be localized in the plasma membrane and to be involved in the release of neurotransmitter in mammalian cells (Falk-Vairant et al., 1996;Morel, 2003). A role of the V 0 -sector was also shown in homotypic membrane fusion of vacuoles in yeast (Peters et al., 2001). V 0 -subcomplexes were reported to build so-called 'trans-complexes' in opposing membranes and were postulated to facilitate membrane fusion. A knockout mutant of the vacuolar a-subunit of V 0 (vph1) was shown to cause fragmentation of vacuoles, also indicating an involvement of the V-ATPase in membrane dynamics (Bayer et al., 2003).Paramecium is a unicellular model organism, in which

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Section: Resultsmentioning

confidence: 99%

The vacuolar proton-ATPase plays a major role in several membrane-bounded organelles inParamecium

Wassmer

Froissard

Plattner

et al. 2005

Journal of Cell Science

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“…Despite this structural diversity the basic functions seem to be conserved between different eukaryotes because the same proteins and cellular processes have been found in Amoeba, Dictyostelium, Paramecium, Trypanosoma and green algae [e.g. V-ATPase (Becker and Hickisch, 2005;Fok et al, 2002;Heuser et al, 1993;Montalvetti et al, 2004;Nishihara et al, 2008;Robinson et al, 1998;Wassmer et al, 2005), aquaporin Nishihara et al, 2008), vesicular transport (Becker and Hickisch, 2005;Buchmann and Becker, 2009;Bush et al, 1994;Harris et al, 2001;Kissmehl et al, 2007;Schilde et al, 2006;Stavrou and O'Halloran, 2006); see KomsicBuchmann and Becker for a summary of identified proteins and cellular processes (Komsic- Buchmann and Becker, 2012)]. …”

Section: Introductionmentioning

confidence: 99%

The SEC6 protein is required for function of the contractile vacuole inChlamydomonas reinhardtii

Komsic-Buchmann¹,

Stephan²,

Becker³

2012

Journal of Cell Science

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SummaryContractile vacuoles (CVs) are essential for osmoregulation in many protists. To investigate the mechanism of CV function in Chlamydomonas, we isolated novel osmoregulatory mutants. Four of the isolated mutant cell lines carried the same 33,641 base deletion, rendering the cell lines unable to grow under strong hypotonic conditions. One mutant cell line (Osmo75) was analyzed in detail. The CV morphology was variable in mutant cells, and most cells had multiple small CVs. In addition, one or two enlarged CVs or no visible CVs at all, were observed by light microscopy. These findings suggest that the mutant is impaired in homotypic vacuolar and exocytotic membrane fusion. Furthermore the mutants had long flagella. One of the affected genes is the only SEC6 homologue in Chlamydomonas (CreSEC6). The SEC6 protein is a component of the exocyst complex that is required for efficient exocytosis. Transformation of the Osmo75 mutant with a CreSEC6-GFP construct rescued the mutant completely (osmoregulation and flagellar length). Rescued strains overexpressed CreSEC6 (as a GFP-tagged protein) and displayed a modified CV activity. CVs were larger, whereas the CV contraction interval remained unchanged, leading to increased water efflux rates. Electron microscopy analysis of Osmo75 cells showed that the mutant is able to form the close contact zones between the plasma membrane and the CV membrane observed during late diastole and systole. These results indicate that CreSEC6 is essential for CV function and required for homotypic vesicle fusion during diastole and water expulsion during systole. In addition, CreSEC6 is not only necessary for CV function, but possibly influences the CV cycle in an indirect manner and flagellar length in Chlamydomonas.

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“…Here, like in other acidic compartments, such as endosomes, occurrence of an H + -ATPase was demonstrated (Fok et al 2002;Wassmer et al 2009). As mentioned, changing acidification also implies change of Rab protein binding (Hurtado- Lorenzo et al 2006) at the organelle surface.…”

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confidence: 62%

Signals Regulating Vesicle Trafficking in Paramecium Cells

Plattner

2016

Biocommunication of Ciliates

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Most data available from Paramecium, fewer from Tetrahymena, disclose essentially the same principles of signaling as in metazoans up to man. Microtubules serve for long-range signaling, whereas SNARE proteins, H + -ATPase, GTPases and actin provide short-range molecular signals, with Ca 2+ as a most efficient, locally and spatially restricted signal particularly for membrane fusion. This is enabled by the strategic positioning of Ca 2+ -release channels, type InsP 3 receptors and ryanodine-receptor-like proteins, also in ciliates. In Paramecium, the most evident trafficking routes encompass exo-/endocytosis, endo-/phagocytosis and the contractile vacuole complex. The high specificity, precision and efficiency of vesicle trafficking regulation in ciliates is facilitated by their highly regular, epigenetically controlled cell structure, with firmly installed microtubular rails.

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The Vacuolar‐ATPase of Paramecium multimicronucleatum: Gene Structure of the B Subunit and the Dynamics of the V‐ATPase‐rich Osmoregulatory Membranes

Cited by 22 publications

References 47 publications

The vacuolar proton-ATPase plays a major role in several membrane-bounded organelles inParamecium

The vacuolar proton-ATPase plays a major role in several membrane-bounded organelles inParamecium

The SEC6 protein is required for function of the contractile vacuole inChlamydomonas reinhardtii

Signals Regulating Vesicle Trafficking in Paramecium Cells

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