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Stat4 regulates multiple components of IFN-gamma-inducing signaling pathways
V A Lawless1, S Zhang, O N Ozes
1Department of Microbiology and Immunology and Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|December 20, 2000
Summary
Signal transducer and activator of transcription 4 (Stat4) is crucial for interleukin-12 (IL-12) to induce interferon-gamma (IFN-gamma). Stat4 is required for multiple cytokine pathways to function, ultimately leading to IFN-gamma induction.
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- Interleukin-12 (IL-12) is a key cytokine that induces interferon-gamma (IFN-gamma) production, primarily through the Signal transducer and activator of transcription 4 (Stat4) pathway.
- The exact role of Stat4 in IL-12-mediated IFN-gamma induction and its impact on other cytokine signaling pathways remain incompletely understood.
Purpose of the Study:
- To elucidate the precise function of Stat4 in the induction of IFN-gamma and associated genes.
- To investigate the impact of Stat4 deficiency on IL-12 and IL-18 signaling pathways.
- To determine the necessity of Stat4 for cytokine-induced IFN-gamma expression.
Main Methods:
- Comparative analysis of IL-12 signaling components in Stat4-deficient and wild-type T cells.
- Assessment of Janus kinase (Jak2) and Tyrosine kinase 2 (Tyk2) phosphorylation.
- Evaluation of IL-18 receptor (IL-18R) expression and NF-kappaB DNA-binding activity following IL-12 pretreatment.
- Measurement of IFN-gamma production upon stimulation with IL-18 and/or IL-12.
Main Results:
- Stat4 deficiency led to decreased basal expression of IL-12 receptor subunits (IL-12Rss1 and IL-12Rss2).
- IL-12 induced equivalent Jak2 and Tyk2 phosphorylation in both wild-type and Stat4-deficient cells.
- Stat4-deficient cells exhibited defective IL-18 signaling, characterized by reduced IL-18R expression and impaired IL-18-induced NF-kappaB activation.
- Absence of Stat4 significantly diminished IFN-gamma production in response to IL-18, even after IL-12 pretreatment.
Conclusions:
- Stat4 activation by IL-12 is essential for the proper function of multiple cytokine pathways involved in IFN-gamma induction.
- Stat4 plays a critical role in regulating IL-18 receptor expression and downstream signaling, thereby influencing IFN-gamma production.
- These findings highlight Stat4 as a central mediator connecting IL-12 and IL-18 signaling for effective IFN-gamma responses.