A parafusin-related Toxoplasma protein in Ca2+-regulated secretory organelles

doi:10.1078/0171-9335-00214

European Journal of Cell Biology

Volume 80, Issue 12, December 2001, Pages 775-783

https://doi.org/10.1078/0171-9335-00214 Get rights and content

Summary

We cloned a gene, PRP1, of Toxoplasma gondii encoding a 637-amino-acids protein having a calculated mass of 70 kDa. The sequence showed high homology to parafusin, a protein that in Paramecium tetraurelia participates in Ca²⁺-regulated exocytosis and is a paralog of phosphoglucomutase. We show that Toxoplasma gondii homogenate and an expressed recombinant PRP1 fusion protein cross-react with a specific peptide-derived antibody to parafusin in Western blots. Antibodies to the recombinant PRP1 showed cross-reaction with parafusin and recognized PRP1, as bands at M_r 63×10³ and 68×10³, respectively. PRP1 is labeled when Toxoplasma gondii cells are incubated with inorganic ³²P and appears as the major band on autoradiograms of SDS-PAGE gels. The localization of PRP1 was examined in secretory organelles of Toxoplasma gondii by deconvolution light microscopy followed by three dimensional reconstruction using pairwise combinations of specific antibodies. PRP1 localized to the apical third of the cell. It co-localized with micronemes, the only secretory organelle the secretion of which is Ca²⁺ dependent. Quantification of the co-localized stain suggests that only mature micronemes ready for exocytosis have PRP1. These findings suggest that PRP1, parafusin and other members of the phosphoglucomutase superfamily have a conserved role in Ca²⁺-regulated exocytic processes.

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Citation Excerpt :
Paralogs of the enzyme phosphoglucomutase (PGM) exist in various eukaryotes and function in calcium-mediated signaling events (Kim et al., 1992). This PGM paralog is called PFUS in Paramecium (Satir et al., 1989) and PRP1 in Toxoplasma (Matthiesen et al., 2001, 2003), with a putative ortholog also being present in the Plasmodium genome (Kats et al., 2008). RNA interference (RNAi) knock-down of PFUS in P. tetraurelia results in failed assembly of the DCSVs, which is consistent with a function in the secretory vesicle scaffold of DCSVs (Liu et al., 2011).
The alveolate superphylum includes many free-living and parasitic organisms, which are united by the presence of alveolar sacs lying proximal to the plasma membrane, providing cell structure. All species comprising the apicomplexan group of alveolates are parasites and have adapted to the unique requirements of the parasitic lifestyle. Here the evolution of apicomplexan secretory organelles that are involved in the critical process of egress from one cell and invasion of another is explored. The variations within the Apicomplexa and how these relate to species-specific biology will be discussed. In addition, recent studies have identified specific calcium-sensitive molecules that coordinate the various events and regulate the release of these secretory organelles within apicomplexan parasites. Some aspects of this machinery are conserved outside the Apicomplexa, and are beginning to elucidate the conserved nature of the machinery. Briefly, the relationship of this secretion machinery within the Apicomplexa will be discussed, compared with free-living and predatory alveolates, and how these might have evolved from a common ancestor.
Calcium signaling in closely related protozoan groups (Alveolata): Non-parasitic ciliates (Paramecium, Tetrahymena) vs. parasitic Apicomplexa (Plasmodium, Toxoplasma)
2012, Cell Calcium
Citation Excerpt :
A 63 kDa-phosphoprotein, pp63, is dephosphorylated during synchronous trichocyst exocytosis in parallel with ATP decay (≤5 s) and rephosphorylated during ATP recovery (≥20 s), as summarized previously [424]. This protein was identified in Paramecium as phosphoglucomutase, PGM [425]; it was also found in Toxoplasma [426]. Based on its sensitivity to PP2B/CaN and to a Ca2+-inhibitable protein kinase we derived a Ca2+-sensitive de-/rephosphorylation cycle for pp63/PGM in connection with the mobilization of glucose for glycolysis [424,427] in spatially restricted cortical areas where pp63/PGM is enriched [428].
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A parafusin-related Toxoplasma protein in Ca2+-regulated secretory organelles

Summary

J. Biol. Chem.

Int. J. Parasitol.

Anal. Biochem.

Exp. Cell Res.

J. Biol. Chem.

J. Biol. Chem.

Anal. Biochem.

J. Biol. Chem.

Cell

J. Mol. Biol.

Trends Cell Biol.

Int. J. Parasitol.

Eur. J. Cell Biol.

Genetic analysis of membrane differentiation in Paramecium. Freeze-fracture study of the trichocyst cycle in wild-type and mutant strains

J. Cell Biol.

Superresolution three-dimensional images of fluorescence in cells with minimal light exposure

Science

Secretion of micronemal proteins is associated with Toxoplasma invasion of host cells

Cell. Microbiol.

Sequential protein secretion from three distinct organelles of Toxoplasma gondii accompanies invasion of human fibroblasts

Eur. J. Cell Biol.

Mobilization of intracellular calcium stimulates microneme discharge in Toxoplasma gondii

Mol. Microbiol.

In vivo analysis of the major exocytosis-sensitive phosphoprotein in Tetrahymena

J. Cell Biol.

Inhibitory and activating functions for MAPK Kss1 in the S. cerevisiae filamentous-growth signalling pathway.

Nature

Visualization of single RNA transcripts in situ.

Science

The role of Rab3A in neurotransmitter release

Nature

A parafusin-related Toxoplasma protein in Ca²⁺-regulated secretory organelles