Stat4 regulates multiple components of IFN-gamma-inducing signaling pathways.
Stat4 is activated in response to IL-12. Most functions of IL-12, including the induction of IFN-gamma, are compromised in the absence of Stat4. Since the precise role of Stat4 in IFN-gamma induction has not been established, experiments were conducted to examine Stat4 activation of IFN-gamma and other genes required for cytokine-induced expression of IFN-gamma. We first examined IL-12 signaling components. Basal expression of IL-12Rss1 and IL-12Rss2 is decreased in Stat4-deficient cells compared with that in control cells. However, IL-12 was still capable of inducing equivalent phosphorylation of Jak2 and Tyk2 in wild-type and Stat4-deficient activated T cells. We have further determined that other cytokine signaling pathways that induce IFN-gamma production are defective in the absence of Stat4. IL-18 induces minimal IFN-gamma production from Stat4-deficient activated T cells compared with control cells. This is due to defective IL-18 signaling, which results from the lack of IL-12-induced, and Stat4-dependent, expression of the IL-18R. Following IL-12 pretreatment to induce IL-18R, wild-type, but not Stat4-deficient, activated T cells demonstrated IL-18-induced NF-kappaB DNA-binding activity. In addition, IL-12-pretreated Stat4-deficient activated T cells have minimal IFN-gamma production followed by stimulation with IL-18 alone or in combination with IL-12 compared with control cells. Thus, Stat4 activation by IL-12 is required for the function of multiple cytokine pathways that result in induction of IFN-gamma.
Lawless
V A
VA
Department of Microbiology and Immunology and Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Zhang
S
S
Ozes
O N
ON
Bruns
H A
HA
Oldham
I
I
Hoey
T
T
Grusby
M J
MJ
Kaplan
M H
MH
D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D007371:Interferon-gamma / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D007375:Interleukin-1 / Q000502:physiology; D018664:Interleukin-12 / Q000502:physiology; D020382:Interleukin-18 / Q000502:physiology; D053614:Janus Kinase 2; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D050797:STAT4 Transcription Factor; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D053634:TYK2 Kinase; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
D004268:DNA-Binding Proteins; D007375:Interleukin-1; D020382:Interleukin-18; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050797:STAT4 Transcription Factor; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D018664:Interleukin-12; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D053634:TYK2 Kinase; C499356:Tyk2 protein, mouse