Migratory activation of parasitized dendritic cells by the protozoanToxoplasma gondii14-3-3 protein

Abstract

The obligate intracellular parasite Toxoplasma gondii exploits cells of the immune system to disseminate. Upon infection, parasitized dendritic cells (DCs) and microglia exhibit a hypermigratory phenotype in vitro that has been associated with enhancing parasite dissemination in vivo in mice. One unresolved question is how parasites commandeer parasitized cells to achieve systemic dissemination by a ‘Trojan horse’ mechanism. By chromatography and mass spectrometry analyses, we identified an orthologue of the 14-3-3 protein family, T. gondii 14-3-3 (Tg14-3-3), as mediator of DC hypermotility. We demonstrate that parasite-derived polypeptide fractions enriched for Tg14-3-3 or recombinant Tg14-3-3 are sufficient to induce the hypermotile phenotype when introduced by protein transfection into murine DCs, human DCs or microglia. Further, gene transfer of Tg14-3-3 by lentiviral transduction induced hypermotility in primary human DCs. In parasites expressing Tg14-3-3 in a ligand regulatable fashion, over-expression of Tg14-3-3 was correlated with induction of hypermotility in parasitized DCs. Localization studies in infected DCs identified Tg14-3-3 within the parasitophorous vacuolar space and a rapid recruitment of host cell 14-3-3 to the parasitophorous vacuole membrane. The present work identifies a determinant role for Tg14-3-3 in the induction of the migratory activation of immune cells by T. gondii. Collectively, the findings reveal Tg14-3-3 as a novel target for an intracellular pathogen that acts by hijacking the host cell’s migratory properties to disseminate.

Toxoplasma gondii disrupts β1 integrin signaling and focal adhesion formation during monocyte hypermotility

“…Recently, it was found that T. gondii secretes a 14-3-3 protein (Tg14-3-3) into the parasitophorous vacuole and sequesters host 14-3-3 (54), a family of adapter proteins involved in numerous signaling pathways including adhesion. The introduction of purified Tg14-3-3 into DCs or the expression of Tg14-3-3 in DCs is sufficient to induce hypermotility (54). In addition, a peptide from the T. gondii dense granule protein GRA5 increases the CCR7-mediated chemotaxis of DCs (55).…”

Microvesicles released from Giardia intestinalis disturb host-pathogen response in vitro

“…Recently, some manuscripts have shown and reviewed the role of dendritic cells during protozoan −host cell interaction (i.e. Boscardin et al, 2016;Weidner et al, 2016;Feijó et al, 2016;Ersching et al, 2016). However, there are no current reports involving MVs from parasites in modulating dendritic cell functions.…”

Parasitized Natural Killer cells do not facilitate the spread of Toxoplasma gondii to the brain

“…For example, adoptive transfer of T. gondii ‐infected DCs into the peritoneal cavity resulted in higher infection loads in the brain at early time points post‐infection, when compared with infection with free parasites 4, 5, 7. Furthermore, blood CD11b+ cells (which may include NK cells) were able to shuttle tachyzoites across the blood‐brain barrier 5, 30.…”

“…T. gondii may exploit the natural migratory pathways of host cells, or actively manipulate host cell migration to augment spread. In vitro studies have shown that parasitized DC displays rapid cytoskeletal remodelling, induction of a hypermotile phenotype and enhanced transmigration across endothelial monolayers 4, 6, 7. It is therefore reasonable to suggest that T. gondii is transported across the blood‐brain barrier within host immune cells.…”