Coordinate Control of Host Centrosome Position, Organelle Distribution, and Migratory Response by Toxoplasma gondii via Host mTORC2

Yubao Wang,Louis M Weiss,Amos Orlofsky

doi:10.1074/jbc.m109.095778

Yubao Wang, Louis M Weiss + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m109.095778

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Abstract

The invasion of host cells by Toxoplasma gondii is accompanied by a reorganization of host cell structure, in which the host centrosome and Golgi apparatus are localized to the vacuole, and mitochondria, microtubules, and endolysosomes are recruited to the vacuole perimeter. The mechanism and functional significance of this process have not been well defined. Here, we report that the centrosome-vacuole association was abolished in mammalian target of rapamycin complex 2 (mTORC2)-deficient cells, which also displayed a disordered distribution of perivacuolar host mitochondria and lysosomes. Infection of fibroblasts led to stable, mTORC2-dependent activation of Akt, and Akt inhibition mimicked the effect of mTORC2 ablation on centrosome, mitochondria, and lysosome localization. Mobilization of the centrosome by Akt inhibition was abrogated by inhibitors of glycogen synthase kinase 3 (GSK3), implying that the centrosome is constrained to the vacuole through an mTORC2-Akt-GSK3 pathway. Infected cells were incapable of migration in a wounded monolayer model, and this effect was associated with the inability of centrosomes to reorient in the direction of migration. Both migration and centrosome reorientation were fully restored upon ablation of mTORC2. These findings provide the first linkage of host signals to parasite-mediated host cell reorganization and demonstrate migratory suppression as a novel functional consequence of this process that is associated with mTORC2-mediated centrosome constraint.

Highlights

The host centrosome and Golgi become closely associated with the parasitophorous vacuole (PV), which is tightly wrapped by host microtubules, mitochondria, and endoplasmic reticulum
We examined the relationship between mTOR complex 2 (mTORC2) and Akt signaling in parasitized human foreskin fibroblasts (HFFs), in which we had previously demonstrated the stable activation of Akt by T. gondii [15]
No effect of mTORC2 depletion was observed on the distribution of mitochondria or lysosomes in uninfected MEFs (Figs. 4C and 5C). These results demonstrate a correlation between parasite regulation of the host centrosome/microtubule network and the maintenance of an ordered distribution of mitochondria and lysosomes around the PV, indicating a potential mechanistic linkage between these events

Summary

Introduction

Signaling via the Ser/Thr kinase Akt has been implicated in polarization during migratory responses in fibroblasts [14], and we have previously demonstrated that T. gondii infection of primary fibroblasts results in stable activation of host Akt [15]. Our findings demonstrate that this pathway is critical for control of centrosome position and organelle distribution in parasitized cells and indicate a link between centrosome constraint and regulation of migratory response. These results indicate that the mTORC2-dependent restriction of centrosome position is mediated by Akt and demonstrate that continual signaling is required to maintain PV-centrosome association.

Results

Conclusion