Faculty Opinions recommendation of Host cell subversion by Toxoplasma GRA16, an exported dense granule protein that targets the host cell nucleus and alters gene expression.

The intracellular parasite Toxoplasma gondii adapts to diverse host cell environments within a replicative compartment that is heavily decorated by secreted proteins. In attempts to identify novel parasite secreted proteins that influence host cell activity, we identified and characterized a trans-membrane dense granule protein dubbed GRA64 (TGME49_202620). We found that GRA64 is on the parasitophorous vacuolar membrane (PVM) and is partially exposed to the host cell cytoplasm in both tachyzoite and bradyzoite parasitophorous vacuoles. Using co-immunoprecipitation and proximity-based biotinylation approaches, we demonstrate that GRA64 appears to interact with certain components of the host Endosomal Sorting Complexes Required for Transport (ESCRT). Genetic disruption of GRA64 does not affect acute Toxoplasma virulence in mice nor encystation as observed via tissue cyst burdens in mice during chronic infection. However, ultrastructural analysis of Dgra64 tissue cysts using electron tomography revealed enlarged vesicular structures underneath the cyst membrane, suggesting a role for GRA64 in organizing the recruitment of ESCRT proteins and subsequent intracystic vesicle formation. This study uncovers a novel host-parasite interaction that contributes to an emerging paradigm in which specific host ESCRT proteins are recruited to the limiting membranes (PVMs) of tachyzoite and bradyzoite vacuoles formed during acute and chronic Toxoplasma infection.

Download Full-text

ARE LEUCOCYTOZOON SAKHAROFFI SAMBON AND LEUCOCYTOZOON BERESTNEFFI SAMBON SYNONYMOUS?

Canadian Journal of Research ◽

10.1139/cjr50d-001 ◽

1950 ◽

Vol 28d (1) ◽

pp. 1-4 ◽

Cited By ~ 3

Author(s):

A. Murray Fallis

Keyword(s):

Host Cell ◽

Cell Nucleus ◽

Infected Cells ◽

Host Cell Nucleus

The size of the gametocytes of a leucocytozoon in young crows shows a wide variation in birds obtained in different localities. The host cell nucleus of infected cells may be pushed to one side, almost surround the parasite, or be intermediate between these extremes. Previous descriptions, given by various authors, of Leucocytozoon sakharoffi and L. berestneffi show similar differences in these characters. L. berestneffi is considered therefore to be a synonym of L. sakharoffi.

Download Full-text

First Characterization of theNeospora caninumDense Granule Protein GRA9

BioMed Research International ◽

10.1155/2017/6746437 ◽

2017 ◽

Vol 2017 ◽

pp. 1-15 ◽

Cited By ~ 5

Author(s):

Margret Leineweber ◽

Katrin Spekker-Bosker ◽

Vanessa Ince ◽

Gereon Schares ◽

Andrew Hemphill ◽

...

Keyword(s):

Host Cell ◽

Cell Invasion ◽

Neospora Caninum ◽

Parasitophorous Vacuole ◽

Dense Granule ◽

Immunogold Electron Microscopy ◽

Host Cell Invasion ◽

Dense Granules ◽

Granule Protein

The obligate intracellular apicomplexan parasiteNeospora caninum (N. caninum)is closely related toToxoplasma 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 theN. caninumdense 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 ofN. 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 ofN. caninum, and the truncated proteins show reduced secretion.

Download Full-text