Thursday, November 27, 2008

Host cell autophagy is induced by Toxoplasma gondii and contributes to parasite growth

J Biol Chem. 2008 Nov 21. [Epub ahead of print]

Host cell autophagy is induced by Toxoplasma gondii and contributes to parasite growth

Wang Y, Weiss LM, Orlofsky A.

Pathology, Albert Einstein College of Medicine, Bronx, NY 10461.

Autophagy has been shown to contribute to defense against intracellular bacteria and parasites. In comparison, the ability of such pathogens to manipulate host cell autophagy to their advantage has not been examined. Here we present evidence that infection by Toxoplasma gondii, an intracellular protozoan parasite, induces host cell autophagy in both HeLa cells and primary fibroblasts, via a mechanism dependent on host Atg5 but independent of host mTOR suppression. Infection led to the conversion of LC3 to the autophagosome-associated form LC3-II, to the accumulation of LC3-containing vesicles near the parasitophorous vacuole, and to the relocalization towards the vacuole of structures labeled by the phosphatidylinositol-3-phosphate indicator, YFP-2xFYVE. The autophagy regulator beclin 1 was concentrated in the vicinity of the parasitophorous vacuole in infected cells. Inhibitor studies indicated that parasite-induced autophagy is dependent on calcium signaling and on abscisic acid. At physiologically relevant amino acid levels parasite growth became defective in Atg5-deficient cells, indicating a role for host cell autophagy in parasite recovery of host cell nutrients. A flow cytometric analysis of cell size as a function of parasite content revealed that autophagy-dependent parasite growth correlates with autophagy-dependent consumption of host cell mass that is dependent on parasite progression. These findings indicate a new role for autophagy as a pathway by which parasites may effectively compete with the host cell for limiting anabolic resources.

PMID: 19028680 [PubMed - as supplied by publisher]

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