ApiLoc - A database of published protein sub-cellular localisation in Apicomplexa

version 3 (curated until May 28, 2011)

Role of the parafusin orthologue, PRP1, in microneme exocytosis and cell invasion in Toxoplasma gondii.

Matthiesen, S. H., Shenoy, S. M., Kim, K., Singer, R. H., Satir, B. H. (2003 Sep, Cell Microbiol)

The association of PRP1, a Paramecium parafusin orthologue, with Toxoplasma gondii micronemes, now confirmed by immunoelectron microscopy, has here been studied in relation to exocytosis and cell invasion. PRP1 becomes labelled in vivo by inorganic 32P and is dephosphorylated when ethanol is used to stimulate Ca2+-dependent exocytosis of the micronemes. The ethanol Ca2+-stimulated exocytosis is accompanied by translocation of PRP1 and microneme content protein (MIC3) from the apical end of the parasite. Immunoblotting showed that PRP1 is redistributed inside the parasite, while microneme content is secreted. To study whether similar changes occur during cell invasion, quantitative microscopy was performed during secretion, invasion and exit (egress) from the host cell. Time-course experiments showed that fluorescence intensities of PRP1 and MIC3 immediately after invasion were reduced 10-fold compared to preinvasion levels, indicating that PRP1 translocation and microneme secretion accompanies invasion. MIC3 regained fluorescence intensity and apical distribution after 15 min, while PRP1 recovered after 1 h. Intensity of both proteins then increased throughout the parasite division period until host cell lysis, suggesting the need to secrete microneme proteins to egress. These studies suggest that PRP1 associated with the secretory vesicle scaffold serves an important role in Ca2+-regulated exocytosis and cell invasion.

PubMed: 12925131, full text

Localisation information

TGME49_085980 (glucosephosphate-mutase I, PRP1) phosphoglucomutase/parafusin related protein 1, putative

Experimental localisation: conoid during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "In post-embedding gold particle labelling of LR white sections shows that PRP1 is localized to the micronemes. "
  • Microscopy type: Light, EM
  • Microscopy method: polyclonal antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: Genbank AF295534 found from referenced article 11831391 – blasted from there
  • Localisation record: conoid during tachyzoite

TGME49_119560 (MIC3, MIC 3) microneme protein MIC3

Experimental localisation: microneme during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "The fluorescence micrographs show that staining of the apical end is reduced after invasion (2 min) for both PRP1 and the microneme content protein MIC3."
  • Microscopy type: Light
  • Microscopy method: Monoclonal antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: micronemes during tachyzoite