Cytosolic-DNA-Mediated, STING-Dependent Proinflammatory Gene Induction Necessitates Canonical NF-κB Activation through TBK1

Abstract

STING (stimulator of interferon genes) is known to control the induction of innate immune genes in response to the recognition of cytosolic DNA species, including the genomes of viruses such as herpes simplex virus 1 (HSV-1). However, while STING is essential for protection of the host against numerous DNA pathogens, sustained STING activity can lead to lethal inflammatory disease. It is known that STING utilizes interferon regulatory factor 3 (IRF3) and nuclear factor B (NF-B) pathways to exert its effects, although the signal transduction mechanisms remain to be clarified fully. Here we demonstrate that in addition to the activation of these pathways, potent induction of the Jun N-terminal protein kinase/stress-activated protein kinase (JNK/SAPK) pathway was similarly observed in response to STING activation by double-stranded DNA (dsDNA). Furthermore, TANK-binding kinase 1 (TBK1) associated with STING was found to facilitate dsDNA-mediated canonical activation of NF-B as well as IRF3 to promote proinflammatory gene transcription. The triggering of NF-B function was noted to require TRAF6 activation. Our findings detail a novel dsDNA-mediated NF-B activation pathway facilitated through a STING-TRAF6-TBK1 axis and suggest a target for therapeutic intervention to plausibly stimulate antiviral activity or, alternatively, avert dsDNA-mediated inflammatory disease. IMPORTANCE The IKK complex, which is composed of two catalytic subunits, IKK␣ and IKK␤, has been suggested to be essential for the activation of canonical NF-B signaling in response to various stimuli, including cytokines (e.g., interleukin-1␣ [IL-1␣] and tumor necrosis factor alpha [TNF-␣]), Toll-like receptor (TLR) ligands (e.g., lipopolysaccharide [LPS]), and dsRNAs derived from viruses, or a synthetic analog. STING has been identified as a critical signaling molecule required for the detection of cytosolic dsDNAs derived from pathogens and viruses. However, little is known about how cytosolic dsDNA triggers NF-B signaling. In the present study, we demonstrate that TBK1, identified as an IKK-related kinase, may predominantly control the activation of NF-B in response to dsDNA signaling via STING through the IKK␣␤ activation loop. Thus, our results establish TBK1 as a downstream kinase controlling dsDNA-mediated IRF3 and NF-B signaling dependent on STING.

Herpes Simplex Virus 1 UL24 Abrogates the DNA Sensing Signal Pathway by Inhibiting NF-κB Activation

“…Herpesvirus infection has been shown to induce mitochondrial stress, and mitochondrial DNA (mtDNA) is then released into the cytoplasm (45). DNA in the cytoplasm triggers the activation of the cGAS-STING DNA sensing pathway, which results in the activation of IRF3 and NF-B (11,21). IFNs and inflammatory chemokines are then produced to suppress the replication of herpesviruses.…”

Enhanced immunostimulatory activity of cyclic dinucleotides on mouse cells when complexed with a cell‐penetrating peptide or combined with CpG

“…Activated STING recruits TBK1 and IRF-3, which in turn results in transcription of IFN-β and proinflammatory cytokines [7,12]. Recent evidence suggests that TRAF6 may be recruited to the STING-TBK1 complex, facilitating the activation of NF-κB and IRF-3 (through TBK1) [39]. TRAF6 is an important molecule that converges signals from various PRRs, affecting DC maturation and induction of cytokine production [40].…”

Activation and Regulation of DNA-Driven Immune Responses

“…At present, there are data to support that this occurs through at least 2 pathways. First, in murine fibroblasts and myeloid cells lacking STING, the activation of NF-B and the induction of NF-B-stimulated genes are impaired (75,76). The STING-dependent pathway for the activation of NF-B was proposed to involve TRAF6 acting upstream of TBK1 to trigger the classical IB kinase ␣/␤ (IKK␣/␤) pathway (75) (Fig.…”