Termination of STING responses is mediated via ESCRT‐dependent degradation

Abstract

cGAS-STING signalling is induced by detection of foreign or mislocalised host double-stranded (ds)DNA within the cytosol. STING acts as the major signalling hub, where it controls production of type I interferons and inflammatory cytokines. Basally, STING resides on the ER membrane. Following activation STING traffics to the Golgi to initiate downstream signalling and subsequently to endolysosomal compartments for degradation and termination of signalling. While STING is known to be degraded within lysosomes, the mechanisms controlling its delivery remain poorly defined.Here we utilised a proteomics-based approach to assess phosphorylation changes in primary murine macrophages following STING activation. This identified numerous phosphorylation events in proteins involved in intracellular and vesicular transport. We utilised high-temporal microscopy to track STING vesicular transport in live macrophages. We subsequently identified that the endosomal complexes required for transport (ESCRT) pathway detects ubiquitinated STING on vesicles, which facilitates the degradation of STING in murine macrophages. Disruption of ESCRT functionality greatly enhanced STING signalling and cytokine production, thus characterising a mechanism controlling effective termination of STING signalling.

Micronucleus Is Not a Potent Inducer of cGAS-STING Pathway

“…Since TBK1 and IRF3 can be activated independently of cGAS-STING pathways (Liu et al, 2015), we aimed to directly monitor the activity of STING. To achieve this, XpSC33 cells were transduced with viruses encoding emiRFP703-cGAS and mRuby3-STING reporters (Balka et al, 2023; Kuchitsu et al, 2023). STING translocates from the ER to the Golgi apparatus during activation (Mukai et al, 2016).…”

cGLRs Join Their Cousins of Pattern Recognition Receptor Family to Regulate Immune Homeostasis

“…The endolysosomal degradation of ubiquitinated STING in murine macrophages requires endosomal complexes required for the transport (ESCRT) pathway involved in microautophagy for its recognition [129][130][131][132]. ESCRT deficiency or inhibition is associated with an overactivated cGAS/STING signaling pathway.…”

ATG and ESCRT control multiple modes of microautophagy

“…The intracellular localization of STING protein determines its induction activity. The degradation of this protein was found to be accomplished through ESCRT protein‐dependent microautophagy [72,73]. The STING fraction localized on the recycling endosome is ubiquitinated and incorporated into the LAMP1‐positive membrane.…”

“…The cargo condensation by ESCRT proteins during MVB formation is mainly accomplished through recognition of the (poly)ubiquitin attached to the cargo proteins on the endosome membrane, where ESCRTs exert their scission activity. While the same process seems to take place in microautophagy for the degradation of vacuolar membrane proteins [69], the data on microautophagy of proteasomes [71] or STING [72,73] offer us a different view, in which the polyubiquitin chain synthesized at sites other than the vacuolar membrane is translocated to the vicinity of the vacuolar membrane to recruit the ESCRT proteins on the membrane. Further studies will be needed to clarify whether other ESCRT‐driven pathways utilize the polyubiquitin chain on the target organelles.…”