A Patatin-Like Protein Protects Toxoplasma gondii from Degradation in a Nitric Oxide-Dependent Manner

Toxoplasma gondii is an obligate intracellular parasite that uses immune cells to disseminate throughout its host. T. gondii can persist and even slowly replicate in activated host macrophages by reducing the antimicrobial effects of molecules such as nitric oxide (NO). A T. gondii patatin-like protein called TgPL1 was previously shown to be important for survival in activated macro-phages. Here we show that a T. gondiimutant with a deletion of the TgPL1 gene (TgPL1) is degraded in activated macrophages. This degradation phenotype is abolished by the removal of NO by the use of an inducible NO synthase (iNOS) inhibitor or iNOS-deficient macrophages. The exogenous addition of NO tomacrophages results in reduced parasite growth but not the deg-radation ofTgPL1 parasites. These results suggest that NO is necessary but not sufficient for the degradation ofTgPL1 para-sites in activated macrophages. While some patatin-like proteins have phospholipase A2 (PLA2) activity, recombinant TgPL1 purified from Escherichia coli does not have phospholipase activity. This result was not surprising, as TgPL1 contains a G-to-S change at the predicted catalytic serine residue. An epitope-tagged version of TgPL1 partially colocalized with a dense granule protein in the parasitophorous vacuole space. These results may suggest that TgPL1moves to the parasitophorous vacuole to protect parasites from nitric oxide by an undeterminedmechanism. Toxoplasma gondii is a protozoan parasite that is able to infectnucleated cells in warm-blooded hosts, including humans (12). The parasite uses an active invasion process to enter host cells and create a parasitophorous vacuole (PV), which is necessary fo