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

version 3 (curated until May 28, 2011)

A cleavable propeptide influences Toxoplasma infection by facilitating the trafficking and secretion of the TgMIC2-M2AP invasion complex.

Harper, J. M., Huynh, M. H., Coppens, I., Parussini, F., Moreno, S., Carruthers, V. B. (2006 Oct, Mol Biol Cell)

Propeptides regulate protein function and trafficking in many eukaryotic systems and have emerged as important features of regulated secretory proteins in parasites of the phylum Apicomplexa. Regulated protein secretion from micronemes and host cell invasion are inextricably linked and essential processes for the apicomplexan parasite Toxoplasma gondii. TgM2AP is a propeptide-containing microneme protein found in a heterohexameric complex with the microneme protein TgMIC2, a protein that has a demonstrated fundamental role in gliding motility and invasion. TgM2AP function is also central to these processes, because disruption of TgM2AP (m2apKO) results in secretory retention of TgMIC2, leading to reduced TgMIC2 secretion from the micronemes and impaired invasion. Because the TgM2AP propeptide is predicted to be processed in an intracellular site near where TgMIC2 is retained in m2apKO parasites, we hypothesized that the propeptide and its proteolytic removal influence trafficking and secretion of the complex. We found that proTgM2AP traffics through endosomal compartments and that deletion of the propeptide leads to defective trafficking of the complex within or near this site, resulting in aberrant processing and decreased secretion of TgMIC2, impaired invasion, and reduced virulence in vivo, mirroring the phenotypes observed in m2apKO parasites. In contrast, mutation of several cleavage site residues resulted in normal localization, but it affected the stability and secretion of the complex from the micronemes. Therefore, the propeptide and its cleavage site influence distinct aspects of TgMIC2-M2AP function, with both impacting the outcome of infection.

PubMed: 16914527, full text

Localisation information

TGME49_014940 (M2AP, proTgM2AP) MIC2-associated protein M2AP

Experimental localisation: trans-golgi network during extracellular tachyzoite, trans-golgi network during intracellular tachyzoite, early endosome during extracellular tachyzoite, early endosome during intracellular tachyzoite, anterior vesicle during extracellular tachyzoite, anterior vesicle during intracellular tachyzoite, microneme during extracellular tachyzoite, microneme during intracellular tachyzoite, dense granule during extracellular tachyzoite, dense granule during intracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "proTgM2AP localizes to the TGN, early endosome, and anterior vesicles... Figure 3. proTgM2AP is secreted via dense granules"
  • Microscopy type: Light, EM
  • Microscopy method: polyclonal antibody directly to protein
  • Strain: RH
  • Gene model mapping comments: Blast from Neospora M2AP AY039231
  • Localisation record: TGN and early endosome and anterior vesicles and microneme and dense granule during extracellular tachyzoite and intracellular tachyzoite

TGME49_059530 (GalNac) UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase T1, putative

Experimental localisation: trans-golgi network during extracellular tachyzoite, trans-golgi network during intracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "various organellar markers, including TgM2AP, micronemes (B and B'); GRASP-mRFP, Golgi cisternae (C and C'); TgGalNac-YFP, TGN (D and D'); and TgRab51-HA, TGN/early endosome (E and E')."
  • Microscopy type: Light
  • Microscopy method: YFP tag
  • Strain: RH
  • Gene model mapping comments: annotation matches
  • Localisation record: TGN during extracellular tachyzoite and intracellular tachyzoite

TGME49_067810 (Rab51, Rab5) Rab 5

Experimental localisation: trans-golgi network during extracellular tachyzoite, trans-golgi network during intracellular tachyzoite, early endosome during extracellular tachyzoite, early endosome during intracellular tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "various organellar markers, including TgM2AP, micronemes (B and B'); GRASP-mRFP, Golgi cisternae (C and C'); TgGalNac-YFP, TGN (D and D'); and TgRab51-HA, TGN/early endosome (E and E')."
  • Microscopy type: Light
  • Microscopy method: HA tag
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: TGN and early endosome during extracellular tachyzoite and intracellular tachyzoite

TGME49_110780 (GRA4) hypothetical protein

Experimental localisation: dense granule
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "To further investigate secretion of proTgM2AP via the default pathway, we performed dual immunofluorescence labeling of proTgM2AP with the dense granule marker TgGRA4."
  • Microscopy type: Light
  • Microscopy method: antibody
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: dense granule

TGME49_055260 (AMA1) apical membrane antigen 1, putative

Experimental localisation: microneme
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "Extracellular 1C4 and TgM2APpro tachyzoites were subjected to immunofluorescence analysis by using antibodies against TgM2AP and TgAMA1, a microneme protein showing normal localization."
  • Microscopy type: Light
  • Microscopy method: antibody
  • Strain: RH
  • Gene model mapping comments: inferred from another publication
  • Localisation record: microneme