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STING signalling is terminated through ESCRT-dependent microautophagy of vesicles originating from recycling endosomes

ABSTRACT: Stimulator of interferon genes (STING) is essential for the type I interferon response against a variety of DNA pathogens. Upon emergence of cytosolic DNA, STING translocates from the endoplasmic reticulum (ER) to the Golgi where STING activates the downstream kinase TBK1, then to lysosome through recycling endosomes (REs) for its degradation. Although the molecular machinery of STING activation is extensively studied and defined, the one underlying STING degradation and inactivation has not yet been fully elucidated. Here we show that STING is degraded by the endosomal sorting complexes required for transport (ESCRT)-driven microautophagy. Airyscan super-resolution microscopy and correlative light/electron microscopy suggest that STING-positive vesicles of an RE origin are directly encapsulated into Lamp1-positive compartments. Screening of mammalian Vps genes, the yeast homologues of which regulate Golgi-to-vacuole transport, shows that ESCRT proteins are essential for the STING encapsulation into Lamp1-positive compartments. Knockdown of Tsg101 and Vps4, components of ESCRT, results in the accumulation of STING vesicles in the cytosol, leading to the sustained type I interferon response. Knockdown of Tsg101 in human primary T cells leads to an increase the expression of interferon-stimulated genes. STING undergoes K63-linked ubiquitination at lysine 288 during its transit through the Golgi/REs, and this ubiquitination is required for STING degradation. Our results reveal a molecular mechanism that prevents hyperactivation of innate immune signalling, which operates at REs.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Cell Culture, Fibroblast

SUBMITTER: Takehiro Suzuki

LAB HEAD: Naoshi Dohmae

PROVIDER: PXD039411 | Pride | 2023-01-24

REPOSITORIES: Pride

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			Action	DRS
	Proteomic_analysis_of_STING_binding_protteins.mzML	Mzml
	Proteomic_analysis_of_STING_binding_protteins.mzid.gz	Mzid
	STING_0h_1.raw	Raw
	STING_0h_2.raw	Raw
	STING_0h_3.raw	Raw

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Project description:The cGAS-STING pathway forms a major component of the innate immune system. cGAS-STING signalling is induced by detection of either foreign (i.e. pathogenic) or mislocalised host double stranded (ds)DNA present within the cytosol. STING acts as the major signalling hub, where it controls activation of transcription factors IRF3 and NF-B for expression of type I interferons and inflammatory cytokines, respectively. Under resting conditions STING resides on the ER membrane. However, following activation STING traffics to the Golgi to initiate downstream signalling, and subsequently to endolysosomal regions for degradation and termination of signalling. However, while STING is known to be degraded by lysosomes, the mechanisms controlling its delivery remain poorly defined. Here we utilised a mass spectrometry approach to assess phosphorylation changes in primary macrophages following STING activation. This identified a large number of phosphorylation events in proteins involved in intracellular transport, including vesicular trafficking. We utilised high-temporal microscopy to track STING vesicular transport in live macrophages. We observed that while macrophages exhibit rapid degradation of STING (i.e., 4-6 h), basal STING protein levels return slowly (i.e., >24 h). Despite STING protein recovery, ultimately macrophages remain unresponsive to re-challenge with STING ligands. Using a combination of imaging and biochemical approaches we subsequently identify that the endosomal complexes required for transport (ESCRT) pathway detects ubiquitinated STING on endosomes, which facilitates the degradation of STING. Disrupting ESCRT recognition of STING via knockdown of the ESCRT-0 component HRS or inhibiting ESCRT function via overexpression of a dominant negative form of VPS4a enhances STING signalling and cytokine production. Therefore, we have characterised the mechanisms that controls effective termination of STING signalling. Dysregulation of STING localisation or its degradation has been implicated in several diseases including autoimmune, autoinflammatory and neuroinflammatory diseases, hence a clearer understanding of STING degradation is imperative for a better understanding of STING-dependent disease pathologies.

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STING signalling is terminated through ESCRT-dependent microautophagy of vesicles originating from recycling endosomes

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