A single polymorphic amino acid on Toxoplasma gondii kinase ROP16 determines the direct and strain-specific activation of Stat3.
Infection by Toxoplasma gondii down-regulates the host innate immune responses, such as proinflammatory cytokine production, in a Stat3-dependent manner. A forward genetic approach recently demonstrated that the type II strain fails to suppress immune responses because of a potential defect in a highly polymorphic parasite-derived kinase, ROP16. We generated ROP16-deficient type I parasites by reverse genetics and found a severe defect in parasite-induced Stat3 activation, culminating in enhanced production of interleukin (IL) 6 and IL-12 p40 in the infected macrophages. Furthermore, overexpression of ROP16 but not ROP18 in mammalian cells resulted in Stat3 phosphorylation and strong activation of Stat3-dependent promoters. In addition, kinase-inactive ROP16 failed to activate Stat3. Comparison of type I and type II ROP16 revealed that a single amino acid substitution in the kinase domain determined the strain difference in terms of Stat3 activation. Moreover, ROP16 bound Stat3 and directly induced phosphorylation of this transcription factor. These results formally establish an essential and direct requirement of ROP16 in parasite-induced Stat3 activation and the significance of a single amino acid replacement in the function of type II ROP16.
Yamamoto
Masahiro
M
Department of Microbiology and Immunology, Graduate School of Medicine, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan.
Standley
Daron M
DM
Takashima
Seiji
S
Saiga
Hiroyuki
H
Okuyama
Megumi
M
Kayama
Hisako
H
Kubo
Emi
E
Ito
Hiroshi
H
Takaura
Mutsumi
M
Matsuda
Tadashi
T
Soldati-Favre
Dominique
D
Takeda
Kiyoshi
K
D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology*; D000818:Animals; D002522:Chlorocebus aethiops; D006801:Humans; D007113:Immunity, Innate; D053762:Interleukin-12 Subunit p40 / Q000276:immunology; D015850:Interleukin-6 / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000469:parasitology; D051379:Mice; D010770:Phosphotransferases / Q000235:genetics / Q000276:immunology*; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000276:immunology*; D013045:Species Specificity; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology*; D014123:Toxoplasmosis / Q000235:genetics / Q000276:immunology*; D014709:Vero Cells
C500879:IL12B protein, human; C508600:IL6 protein, human; D053762:Interleukin-12 Subunit p40; D015850:Interleukin-6; D015800:Protozoan Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D010770:Phosphotransferases