Autophagic degradation of IRF3 induced by the small-molecule auranofin inhibits its transcriptional and proapoptotic activities

Anna Glanz,Sukanya Chakravarty,Shumin Fan,Karan Chawla,Gayatri Subramanian,Tia Rahman,Dean Walters,Ritu Chakravarti,Saurabh Chattopadhyay

doi:10.1016/j.jbc.2021.101274

Anna Glanz, Sukanya Chakravarty + Show 7 more

Open Access

https://doi.org/10.1016/j.jbc.2021.101274

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Journal: Journal of Biological Chemistry	Publication Date: Oct 5, 2021
Citations: 12	License type: cc-by

Affiliation: University of Toledo

Abstract

The ubiquitously expressed transcription factor interferon (IFN) regulatory factor 3 (IRF3) is critical for the induction of antiviral genes, e.g., type-I IFN. In addition to its transcriptional function, IRF3 also activates a nontranscriptional, proapoptotic signaling pathway. While the proapoptotic function of IRF3 protects against viral infections, it is also involved in harmful immune responses that trigger hepatocyte cell death and promote liver disease. Thus, we hypothesized that a small-molecule inhibitor of the proapoptotic activity of IRF3 could alleviate fatty-acid-induced hepatocyte cell death. We conducted a high-throughput screen, which identified auranofin as a small-molecule inhibitor of the proapoptotic activity of IRF3. In addition to the nontranscriptional apoptotic pathway, auranofin also inhibited the transcriptional activity of IRF3. Using biochemical and genetic tools in human and mouse cells, we uncovered a novel mechanism of action for auranofin, in which it induces cellular autophagy to degrade IRF3 protein, thereby suppressing IRF3 functions. Autophagy-deficient cells were unable to degrade IRF3 upon auranofin treatment, suggesting that the autophagic degradation of IRF3 is a novel approach to regulate IRF3 activities. Using a physiologically relevant in vitro model, we demonstrated that auranofin inhibited fatty-acid-induced apoptotic cell death of hepatocytes. In summary, auranofin is a novel inhibitor of IRF3 functions and may represent a potential therapeutic option in diseases where IRF3 is deleterious.

Highlights

Interferon (IFN) regulatory factor 3 (IRF3), a key transcription factor, is involved in the synthesis of IFN and the IFN-stimulated genes (ISGs) during virus infection [1]
Because IFN regulatory factor 3 (IRF3) is critical for RIG-I-like receptors (RLR)-induced IRF3-mediated pathway of apoptosis (RIPA), RLR activation in the absence or the presence of auranofin was unable to trigger apoptotic activity in the IRF3 knockout cells (Fig. 1H)
Because IRF3 plays a proapoptotic role in hepatocyte apoptosis, we examined whether auranofin induces IRF3 degradation, as observed earlier in nonhepatic cells, to inhibit palmitic acid (PA)-induced apoptosis

Summary

Introduction

Interferon (IFN) regulatory factor 3 (IRF3), a key transcription factor, is involved in the synthesis of IFN and the IFN-stimulated genes (ISGs) during virus infection [1]. In MDA-MB-453 cells, auranofin significantly inhibited, doseand time-dependently, the RLR-induced C-PARP (Fig. 1D) and caspase-3 activity (Fig. 1E). We validated these results in MDAMB-453 cells, in which auranofin strongly inhibited the RLR-induced IFIT3 expression (Fig. 2C). To inquire whether auranofin inhibits IRF3 activity or triggers the degradation of IFIT proteins, we analyzed the mRNA induction of the IRF3 target genes.

Results

Conclusion