Phospho-TBK1 (Ser172) and TBK1 assays to monitor the activation of TLR3/4 and cGAS-STING signaling pathways
These cell-based assays are designed to monitor the expression of TBK1, as well as its phosphorylation on Ser172 which is a hallmark of its activation.
Following pathogen infection and binding of dsRNA, LPS, or dsDNA to their respective cell surface receptors TLR3, TLR4 or cytoplasmic sensor cGAS, the kinase TBK1 is recruited to signaling complexes and activated by autophosphorylation at Ser172. The kinase in turn activates IRF3, which translocates to the nucleus and induces the transcription of type I IFNs, leading to an inflammatory response.
TBK1 is also involved in autophagy, where it directly phosphorylates the autophagy receptors optineurin and p62, which target the protein cargo to the autophagosome.
In NASH (Non-Alcoholic Steatohepatitis)/liver fibrosis, Kupffer cells are continuously exposed to an overload of gut-derived bacterial LPS, leading to the upregulation of TLR4, and therefore to an overactivation of TBK1. Therapeutic strategies consist in inhibiting this pathway.
The cGAS-STING signaling axis has recently emerged as a key player in immuno-oncology. Therapeutic activation of this pathway, which can be monitored by an increase in TBK1 phosphorylation, has shown promising anti-tumor effects in vivo.