Dataset Information

Interferon-? restricts Toxoplasma gondii development in murine skeletal muscle cells via nitric oxide production and immunity-related GTPases.

ABSTRACT: The apicomplexan parasite Toxoplasma gondii is regularly transmitted to humans via the ingestion of contaminated meat products from chronically infected livestock. This route of transmission requires intracellular development and long-term survival of the parasite within muscle tissue. In this study, we determined the cell-autonomous immunity of mature primary embryonic or C2C12 skeletal muscle cells (SkMCs) to infection with T. gondii. Non-activated SkMCs and control fibroblasts sustained parasite replication; however, interferon (IFN)-? significantly inhibited parasite growth in SkMCs but not in fibroblasts. Intracellular parasite replication was diminished by IFN-? whereas host cell invasion was not affected. Tumor necrosis factor (TNF) did not further increase the IFN-?-triggered host defense of SkMCs against Toxoplasma. Remarkably, IFN-? alone or in combination with TNF decreased the high level of T. gondii bradyzoite formation being observed in non-activated SkMCs. Stimulation of SkMCs with IFN-? strongly triggered expression of inducible nitric oxide synthase (iNOS) transcripts, and induced significantly higher levels of nitric oxide (NO) in SkMCs than in fibroblasts. Consequently, pharmacological inhibition of iNOS partially abrogated the IFN-?-induced toxoplasmacidal activity of SkMCs. In addition, SkMCs strongly up-regulated immunity-regulated GTPases (IRGs) following stimulation with IFN-?. IRGs accumulated on Toxoplasma-containing vacuoles in SkMCs in a parasite strain-dependent manner. Subsequent vacuole disruption and signs of degenerating parasites were regularly recognized in IFN-?-treated SkMCs infected with type II parasites. Together, murine SkMCs exert potent toxoplasmacidal activity after stimulation with IFN-? and have to be considered active participants in the local immune response against Toxoplasma in skeletal muscle.

SUBMITTER: Takacs AC

PROVIDER: S-EPMC3443239 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Interferon-γ restricts Toxoplasma gondii development in murine skeletal muscle cells via nitric oxide production and immunity-related GTPases.

Takács Anna C AC Swierzy Izabela J IJ Lüder Carsten G K CG

PloS one 20120914 9

The apicomplexan parasite Toxoplasma gondii is regularly transmitted to humans via the ingestion of contaminated meat products from chronically infected livestock. This route of transmission requires intracellular development and long-term survival of the parasite within muscle tissue. In this study, we determined the cell-autonomous immunity of mature primary embryonic or C2C12 skeletal muscle cells (SkMCs) to infection with T. gondii. Non-activated SkMCs and control fibroblasts sustained paras ...[more]

PMID: 23024821

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Project description:UnlabelledA core set of autophagy proteins is required for gamma interferon (IFN-γ)-mediated clearance of Toxoplasma gondii in the mouse because of their control of several downstream effectors, including immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs). However, these effectors are absent (i.e., IRGs) from or nonessential (i.e., GBPs) in IFN-γ-activated human cells, raising the question of how these cells control parasite replication. Here, we define a novel role for ubiquitination and recruitment of autophagy adaptors in the strain-specific control of T. gondii replication in IFN-γ-activated human cells. Vacuoles containing susceptible strains of T. gondii became ubiquitinated, recruited the adaptors p62 and NDP52, and were decorated with LC3. Parasites within LC3-positive vacuoles became enclosed in multiple layers of host membranes, resulting in stunting of parasite replication. However, LC3-positive T. gondii-containing vacuoles did not fuse with endosomes and lysosomes, indicating that this process is fundamentally different from xenophagy, a form of autophagy involved in the control of intracellular bacterial pathogens. Genetic knockout of ATG16L or ATG7 reverted the membrane encapsulation and restored parasite replication, indicating that core autophagy proteins involved in LC3 conjugation are important in the control of parasite growth. Despite a role for the core autophagy machinery in this process, upstream activation through Beclin 1 was not sufficient to enhance the ubiquitination of T. gondii-containing vacuoles, suggesting a lack of reliance on canonical autophagy. These findings demonstrate a new mechanism for IFN-γ-dependent control of T. gondii in human cells that depends on ubiquitination and core autophagy proteins that mediate membrane engulfment and restricted growth.ImportanceAutophagy is a process of cellular remodeling that allows the cell to recycle senescent organelles and recapture nutrients. During innate immune responses in the mouse, autophagy is recruited to help target intracellular pathogens and thus eliminate them. However, the antimicrobial mediators that depend on autophagy in the mouse are not conserved in humans, raising the issue of how human cells control intracellular pathogens. Our study defines a new pathway for the control of the ubiquitous intracellular parasite T. gondii in human cells activated by IFN-γ. Recruitment of autophagy adaptors resulted in engulfment of the parasite in multiple membranes and growth impairment. Although susceptible type 2 and 3 stains of T. gondii were captured by this autophagy-dependent pathway, type 1 strains were able to avoid entrapment.

Dataset Information

Interferon-? restricts Toxoplasma gondii development in murine skeletal muscle cells via nitric oxide production and immunity-related GTPases.

Publications

Interferon-γ restricts Toxoplasma gondii development in murine skeletal muscle cells via nitric oxide production and immunity-related GTPases.

Similar Datasets

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