Aspects of signal transduction in stimulus exocytosis‐coupling in <i>Paramecium</i>

Satir, Birgit H.; Busch, Gerald R.; Vuoso, Alice; Murtaugh, Timothy J.

doi:10.1002/jcb.240360411

Cited by 39 publications

(18 citation statements)

References 53 publications

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“…(Plattner 1974(Plattner , 1976Bilinski et al, 1981;Satir 1982, 1983;Garafolo et al, 1983;Satir et al, 1988;Cohen 1990, 1996;Knoll et al, 1991Knoll et al, , 1993Erxleben and Plattner 1994;Länge et al, 1995;Erxleben et al, 1997;Plattner 1997, 1998;Iwadate et al, 1997Iwadate et al, , 1999a). Fig.…”

Section: Introductionmentioning

confidence: 97%

Contribution of Calcium Influx on Trichocyst Discharge in Paramecium caudatum

Iwadate

Kikuyama

2001

Zoological Science

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Section: Introductionmentioning

confidence: 97%

Contribution of Calcium Influx on Trichocyst Discharge in Paramecium caudatum

Iwadate

Kikuyama

2001

Zoological Science

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“…A low pH in the trichocyst lumen has been inferred to contribute to stimulus-secretion coupling (Satir, 1989;Satir et al, 1988). Therefore, we have now analyzed in more detail the uptake of A0 under different experimental conditions both in vivo and in vitro.…”

Section: Introductionmentioning

confidence: 99%

Secretory organelles of Paramecium cells (trichocysts) are not remarkably acidic compartments.

Lumpert¹,

Glas-Albrecht²,

Eisenmann³

et al. 1992

J Histochem Cytochem.

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Acridine orange (AO) trapping in conjunction with fluorescence microscopy was applied toPammecium cells. Trichocysts were not labeled when analyzed with an image intensification system (as opposed to a lysosomal population). Only with increasing intensity of ultraviolet light (UV) did trichocysts (and to some extent the cytosol) exhibit orange fluorescence, both effects being paralleled by inaeasing cell damage. Therefore, in comparison with the reported cytosolic pH (6.8), trichocysts cannot be considered as essentially acidic compartments. This is supported by experiments in vitro, using isolated cortex fragments or isolated fractions of membrane-bounded trichocysts (390% non-leaky). Again, during w illumination orange fluorescence was observed even in the absence of ATP and Mg2'. Furthermore, this A0 fluorescence and the condensation state of trichocyst contents were not affected by N H 3 or by any of the widely differing ion-and H+-exchange inhibitors or ionophores tested. Decondensation of trichocyst contents occurred only when Ca2+ ionophore A23187 or X537A was incorporated into trichocyst membranes and when Ca2+ was then added. In this case all trichocysts partially decondensed within their intact membranes. We conclude that A 0 might be trapped in trichocysts by the abundant acidic secretory components during observation with uv light, rather than by acidic luminal pH. ( J Hisrochem Cyrochem 40953-160, 1992)

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“…Previously we discovered a cytosolic phosphoprotein, parafusin, that plays a role in regulated exocytosis in the unicellular eukaryote Paramecium (1,2) and that is evolutionarily conserved (3). Parafusih has been shown to be phosphorylated via a Ca2+-dependent protein kinase (4).…”

mentioning

confidence: 99%

Cloning and sequencing of parafusin, a calcium-dependent exocytosis-related phosphoglycoprotein.

Subramanian

Wyroba

Andersen

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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A cDNA for parafusin, an evolutionarily conserved phosphoglycoprotein involved in exocytosis, has been cloned and sequenced from a uniceilular eukaryote, Paramecium tetraurelia. A Paramecium cDNA library was screened with an oligonucleotide probe synthesized to an internal amino acid sequence of isolated parafusin. The insert was 3 kb long with an open reading frame of 1.75 kb. Data base searches of the deduced amino acid sequence showed that Paramecium parafusin had a 50.7% sequence identity to rabbit muscle phosphoglucomutase, although no detectable phosphoglucomutate activity has been detected in isolated parafusin. The deduced parafusin amino acid sequence had four inserts and two deletions, which might confer on the protein specific functions in signal transduction events related to exocytosis. Furthermore, searches for potential phosphorylation sites showed the presence of a protein kinase C site (KDFSFR) specifi to parafusin. Southern blot analysis with probes specific for parafusin and phosphoglucomutase suggested that these proteins-were products of different genes. We propose that parafusin and phosphoglucomutase are members of a superfamily that conserve homologies important for the tertiary structure of the molecules.Previously we discovered a cytosolic phosphoprotein, parafusin, that plays a role in regulated exocytosis in the unicellular eukaryote Paramecium (1, 2) and that is evolutionarily conserved (3). Parafusih has been shown to be phosphorylated via a Ca2+-dependent protein kinase (4). Surprisingly, parafusin is also a phosphoglycoprotein in which a short chain ofmannose residues is 0-linked to serine. This chain is phosphoglucosylated by a glucose-1-phosphate phosphotransferase that uses UDP glucose (5). We have recently demonstrated that dephosphoglucosylation is catalyzed by a Ca2+-activated phosphodiesterase. Cells in which parafusin is normal but that are unable to release the content of their dense core secretory vesicles upon stimulation show inactive phosphodiesterase, suggesting that dephosphoglucosylation is a critical event in the pathway to exocytosis (4).Tryptic digests of parafusin purified as described earlier (6)

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Aspects of signal transduction in stimulus exocytosis‐coupling in Paramecium

Cited by 39 publications

References 53 publications

Contribution of Calcium Influx on Trichocyst Discharge in Paramecium caudatum

Contribution of Calcium Influx on Trichocyst Discharge in Paramecium caudatum

Secretory organelles of Paramecium cells (trichocysts) are not remarkably acidic compartments.

Cloning and sequencing of parafusin, a calcium-dependent exocytosis-related phosphoglycoprotein.

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