title: Toxoplasma gondii GRA7-Induced TRAF6 Activation Contributes to Host Protective Immunity.
abstract: The intracellular parasite Toxoplasma gondii has unique dense granule antigens (GRAs) that are crucial for host infection. Emerging evidence suggests that GRA7 of T. gondii is a promising serodiagnostic marker and an effective toxoplasmosis vaccine candidate; however, little is known about the intracellular regulatory mechanisms involved in the GRA7-induced host responses. Here we show that GRA7-induced MyD88 signaling through the activation of TRAF6 and production of reactive oxygen species (ROS) is required for the induction of NF-κB-mediated proinflammatory responses by macrophages. GRA7 stimulation resulted in the rapid activation of mitogen-activated protein kinases and an early burst of ROS in macrophages in a MyD88-dependent manner. GRA7 induced a physical association between GRA7 and TRAF6 via MyD88. Remarkably, the C terminus of GRA7 (GRA7-V) was sufficient for interaction with and ubiquitination of the RING domain of TRAF6, which is capable of inflammatory cytokine production. Interestingly, the generation of ROS and TRAF6 activation are mutually dependent on GRA7/MyD88-mediated signaling in macrophages. Furthermore, mice immunized with GRA7-V showed markedly increased Th1 immune responses and protective efficacy against T. gondii infection. Collectively, these results provide novel insight into the crucial role of GRA7-TRAF6 signaling in innate immune responses.
authors.affiliation: Department of Molecular and Life Science, College of Science and Technology, Hanyang University, Ansan, South Korea Department of Microbiology, Chungnam National University School of Medicine, Daejeon, South Korea chulsuyang@hanyang.ac.kr.
authors.forename: Chul-Su
authors.initials: CS
authors.lastname: Yang
authors.affiliation: Department of Infection Biology, Chungnam National University School of Medicine, Daejeon, South Korea.
authors.forename: Jae-Min
authors.initials: JM
authors.lastname: Yuk
authors.affiliation: Department of Infection Biology, Chungnam National University School of Medicine, Daejeon, South Korea Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, South Korea.
authors.forename: Young-Ha
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Department of Microbiology, Chungnam National University School of Medicine, Daejeon, South Korea Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon, South Korea.
authors.forename: Eun-Kyeong
authors.initials: EK
authors.lastname: Jo
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology; D000953:Antigens, Protozoan / Q000378:metabolism*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000276:immunology*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics; D016328:NF-kappa B / Q000276:immunology; D015800:Protozoan Proteins / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000235:genetics; D051197:Toll-Like Receptor 4 / Q000235:genetics; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology / Q000469:parasitology; D054875:Ubiquitination
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016207:Cytokines; C112573:GRA7 protein, Toxoplasma gondii; D008562:Membrane Glycoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D015800:Protozoan Proteins; D017382:Reactive Oxygen Species; D048029:TNF Receptor-Associated Factor 6; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1