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Stimulation of Cytoplasmic DNA Sensing Pathways In Vitro and In Vivo
Published on: September 18, 2014
IFI16 is required for DNA sensing in human macrophages by promoting production and function of cGAMP
K L Jønsson1,2, A Laustsen1,2, C Krapp1,3
1Department of Biomedicine, Aarhus University, Wilhelm Meyers Alle 4, Aarhus C 8000, Denmark.
Abstract:
Innate immune activation by macrophages is an essential part of host defence against infection. Cytosolic recognition of microbial DNA in macrophages leads to induction of interferons and cytokines through activation of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). Other host factors, including interferon-gamma inducible factor 16 (IFI16), have been proposed to contribute to immune activation by DNA. However, their relation to the cGAS-STING pathway is not clear. Here, we show that IFI16 functions in the cGAS-STING pathway on two distinct levels. Depletion of IFI16 in macrophages impairs cGAMP production on DNA stimulation, whereas overexpression of IFI16 amplifies the function of cGAS. Furthermore, IFI16 is vital for the downstream signalling stimulated by cGAMP, facilitating recruitment and activation of TANK-binding kinase 1 in STING complex. Collectively, our results suggest that IFI16 is essential for efficient sensing and signalling upon DNA challenge in macrophages to promote interferons and antiviral responses.
Insights
Interferon-gamma inducible factor 16 (IFI16) plays a crucial role in the innate immune response to microbial DNA. This study reveals IFI16 enhances cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway signaling for effective antiviral defense.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Innate immunity relies on macrophages to detect microbial DNA and initiate defense responses.
- The cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) pathway is key for sensing cytosolic DNA and inducing interferons.
- The precise role of interferon-gamma inducible factor 16 (IFI16) in DNA-triggered immune activation remains unclear.
Purpose of the Study:
- To elucidate the function of IFI16 within the cGAS-STING pathway.
- To determine how IFI16 influences macrophage responses to microbial DNA.
- To investigate the molecular mechanisms by which IFI16 modulates immune signaling.
Main Methods:
- Macrophage cell culture and stimulation with DNA.
- Gene depletion (siRNA) and overexpression techniques for IFI16.
- Measurement of cyclic GMP-AMP (cGAMP) production.
- Analysis of TANK-binding kinase 1 (TBK1) recruitment and activation.
- Assessment of interferon and cytokine induction.
Main Results:
- Depletion of IFI16 in macrophages significantly reduced cGAMP production upon DNA stimulation.
- Overexpression of IFI16 potentiated the enzymatic activity of cGAS.
- IFI16 was essential for the downstream signaling cascade, facilitating TBK1 recruitment and activation within the STING complex.
- IFI16 deficiency impaired the induction of interferons and cytokines.
Conclusions:
- IFI16 acts as a critical positive regulator of the cGAS-STING pathway in macrophages.
- IFI16 enhances both the initial sensing of DNA by cGAS and the subsequent downstream signaling through STING.
- IFI16 is vital for mounting an effective innate immune response against cytosolic DNA pathogens, promoting interferon and antiviral responses.
