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Stimulation of Cytoplasmic DNA Sensing Pathways In Vitro and In Vivo

Stimulation of Cytoplasmic DNA Sensing Pathways In Vitro and In Vivo

Published on: September 18, 2014

STAT2 hinders STING intracellular trafficking and reshapes its activation in response to DNA damage

Chenyao Wang^1,2, Jing Nan³, Elise Holvey-Bates⁴

¹Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195.

Proceedings of the National Academy of Sciences of the United States of America

|April 10, 2023

Abstract:

In cancer cells, endogenous or therapy-induced DNA damage leads to the abnormal presence of DNA in the cytoplasm, which triggers the activation of cGAS (cyclic GMP-AMP synthase) and STING (stimulator of interferon genes). STAT2 suppresses the cGAMP-induced expression of IRF3-dependent genes by binding to STING, blocking its intracellular trafficking, which is essential for the full response to STING activation. STAT2 reshapes STING signaling by inhibiting the induction of IRF3-dependent, but not NF-κB-dependent genes. This noncanonical activity of STAT2 is regulated independently of its tyrosine phosphorylation but does depend on the phosphorylation of threonine 404, which promotes the formation of a STAT2:STING complex that keeps STING bound to the endoplasmic reticulum (ER) and increases resistance to DNA damage. We conclude that STAT2 is a key negative intracellular regulator of STING, a function that is quite distinct from its function as a transcription factor.

Insights

STAT2 negatively regulates STING signaling by blocking its trafficking, distinct from its transcription factor role. This prevents IRF3-dependent gene expression, enhancing DNA damage resistance in cancer cells.

Area of Science:

Immunology
Molecular Biology
Cancer Research

Background:

DNA damage in cancer cells can trigger cytoplasmic DNA sensing pathways.
The cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) pathway is activated by cytoplasmic DNA.
STING activation is crucial for innate immune responses and anti-tumor immunity.

Purpose of the Study:

To investigate the role of STAT2 in regulating STING signaling.
To elucidate the mechanism by which STAT2 modulates STING-mediated immune responses.
To determine if STAT2's function in STING signaling is linked to its known transcription factor activity.

Main Methods:

Western blotting to assess protein phosphorylation and complex formation.
Immunofluorescence microscopy to track STING intracellular trafficking.
Reporter gene assays to measure IRF3 and NF-κB dependent gene induction.
Analysis of STAT2 binding to STING in response to DNA damage.

Main Results:

STAT2 binds to STING and inhibits its intracellular trafficking, suppressing IRF3-dependent gene expression.
STAT2's regulation of STING is independent of tyrosine phosphorylation but dependent on threonine 404 phosphorylation.
Phosphorylation of STAT2 at T404 promotes a STAT2:STING complex, retaining STING at the endoplasmic reticulum.
STAT2 selectively inhibits IRF3-dependent genes, not NF-κB-dependent genes, in response to STING activation.
STAT2 binding to STING enhances cellular resistance to DNA damage.

Conclusions:

STAT2 acts as a novel, noncanonical negative regulator of STING signaling.
STAT2's function in STING pathway regulation is distinct from its role as a transcription factor.
STAT2-mediated inhibition of STING trafficking and IRF3 activation contributes to DNA damage resistance.

Read full analysis

Keywords:

DNA damage STAT2 STING

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