Toxoplasma gondii rhoptry kinase ROP16 activates STAT3 and STAT6 resulting in cytokine inhibition and arginase-1-dependent growth control

• Published in: PLoS pathogens Vol. 7; no. 9; p. e1002236
• Main Authors: Butcher, Barbara A, Fox, Barbara A, Rommereim, Leah M, Kim, Sung Guk, Maurer, Kirk J, Yarovinsky, Felix, Herbert, De'Broski R, Bzik, David J, Denkers, Eric Y
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.09.2011; Public Library of Science (PLoS)
• Subjects: Animals; Arginase - antagonists & inhibitors; Arginase - genetics; Arginase - metabolism; Biology; Bone marrow; Cells, Cultured; Cloning; Cytokines; Cytokines - immunology; Experiments; Female; Gene Deletion; Gene Knockout Techniques; Health aspects; Immune system; Interleukin-12 Subunit p40 - immunology; Janus Kinase 2 - genetics; Janus Kinase 2 - metabolism; Kinases; Macrophages - immunology; Mice; Mice, Inbred C57BL; Myeloid Differentiation Factor 88 - metabolism; Nitric oxide; Parasites; Phosphorylation; Phosphotransferases; Physiological aspects; Plasmids; Protein-Tyrosine Kinases - genetics; Protein-Tyrosine Kinases - metabolism; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; Rodents; Signal Transduction; STAT proteins; STAT3 Transcription Factor - genetics; STAT3 Transcription Factor - metabolism; STAT6 Transcription Factor - genetics; STAT6 Transcription Factor - metabolism; Toxoplasma; Toxoplasma - enzymology; Toxoplasma - genetics; Toxoplasma - pathogenicity; United States; Phosphorylation; Cytokines; Signal Transduction; Mice, Inbred C57BL; Cells, Cultured; Arginase; Myeloid Differentiation Factor 88; Protozoan Proteins; Gene Knockout Techniques; Macrophages; STAT6 Transcription Factor; Janus Kinase 2; Toxoplasma; Animals; Plasmids; Gene Deletion; Female; Mice; STAT3 Transcription Factor; Protein-Tyrosine Kinases; Interleukin-12 Subunit p40
• DOI: 10.1371/journal.ppat.1002236
• ISSN: 1553-7374; 1553-7366

The ROP16 kinase of Toxoplasma gondii is injected into the host cell cytosol where it activates signal transducer and activator of transcription (STAT)-3 and STAT6. Here, we generated a ROP16 deletion mutant on a Type I parasite strain background, as well as a control complementation mutant with restored ROP16 expression. We investigated the biological role of the ROP16 molecule during T. gondii infection. Infection of mouse bone marrow-derived macrophages with rop16-deleted (ΔROP16) parasites resulted in increased amounts of IL-12p40 production relative to the ROP16-positive RH parental strain. High level IL-12p40 production in ΔROP16 infection was dependent on the host cell adaptor molecule MyD88, but surprisingly was independent of any previously recognized T. gondii triggered pathway linking to MyD88 (TLR2, TLR4, TLR9, TLR11, IL-1ß and IL-18). In addition, ROP16 was found to mediate the suppressive effects of Toxoplasma on LPS-induced cytokine synthesis in macrophages and on IFN-γ-induced nitric oxide production by astrocytes and microglial cells. Furthermore, ROP16 triggered synthesis of host cell arginase-1 in a STAT6-dependent manner. In fibroblasts and macrophages, failure to induce arginase-1 by ΔROP16 tachyzoites resulted in resistance to starvation conditions of limiting arginine, an essential amino acid for replication and virulence of this parasite. ΔROP16 tachyzoites that failed to induce host cell arginase-1 displayed increased replication and dissemination during in vivo infection. We conclude that encounter between Toxoplasma ROP16 and the host cell STAT signaling cascade has pleiotropic downstream effects that act in multiple and complex ways to direct the course of infection.