First Characterization of the Neospora caninum Dense Granule Protein GRA9

Biomed Res Int. 2017:2017:6746437. doi: 10.1155/2017/6746437. Epub 2017 Nov 12.

Abstract

The obligate intracellular apicomplexan parasite Neospora caninum (N. caninum) is closely related to Toxoplasma gondii (T. gondii). The dense granules, which are present in all apicomplexan parasites, are important secretory organelles. Dense granule (GRA) proteins are released into the parasitophorous vacuole (PV) following host cell invasion and are known to play important roles in the maintenance of the host-parasite relationship and in the acquisition of nutrients. Here, we provide a detailed characterization of the N. caninum dense granule protein NcGRA9. The in silico genomic organization and key protein characteristics are described. Immunofluorescence-based localization studies revealed that NcGRA9 is located in the dense granules and is released into the interior of the PV following host cell invasion. Immunogold-electron microscopy confirmed the dense granule localization and showed that NcGRA9 is associated with the intravacuolar network. In addition, NcGRA9 is found in the "excreted secreted antigen" (ESA) fraction of N. caninum. Furthermore, by analysing the distribution of truncated versions of NcGRA9, we provide evidence that the C-terminal region of this protein is essential for the targeting of NcGRA9 into the dense granules of N. caninum, and the truncated proteins show reduced secretion.

MeSH terms

  • Amino Acid Sequence / genetics
  • Animals
  • Antigens, Protozoan / chemistry
  • Antigens, Protozoan / genetics
  • Antigens, Protozoan / isolation & purification
  • Cytoplasmic Vesicles / genetics
  • Cytoplasmic Vesicles / metabolism
  • Host-Parasite Interactions / genetics*
  • Neospora / chemistry*
  • Neospora / genetics
  • Neospora / pathogenicity
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / genetics*
  • Toxoplasma / genetics
  • Toxoplasma / pathogenicity

Substances

  • Antigens, Protozoan
  • Protozoan Proteins