Biology subjects

Ogawa, E.

Publications and source records attributed to Ogawa, E..

3 recordsLinked to original sources

bioRxiv2022

Lysosomal vesiculophagy terminates STING signalling

Stimulator of interferon genes (STING) is essential for the type I interferon response against a variety of DNA pathogens1,2. 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 degradation3-6. Although the molecular machinery of STING activation is extensively studied and defined7, the one underlying STING degradation has not yet been fully elucidated. Here we show an unanticipated mechanism termed "lysosomal vesiculophagy" dictates STING degradation. Airyscan super-resolution microscopy and correlative light/electron microscopy show that a cluster of STING-positive vesicles of an RE origin are directly encapsulated into lysosome. Screening of mammalian Vps genes, the yeast homologues of which regulate Golgi-to-vacuole transport8, shows that the endosomal sorting complexes required for transport (ESCRT) is essential for the STING encapsulation into lysosome. Knockdown of Tsg101 and Vps4, components of ESCRT9, results in the accumulation of STING vesicles in the cytosol, leading to the sustained type I interferon response. STING undergoes ubiquitination at REs and degradation of STING requires the ubiquitin-binding domain of Tsg101, ensuring the selective degradation of activated STING. Our results reveal a novel mode of autophagy that prevents hyperactivation of innate immune signalling and provide insights into the ER-Golgi-REs-lysosomes pathway for degradation of transmembrane proteins.

cell biology↗

bioRxiv2021

Implications of cholesterol and sphingomyelin in STING phosphorylation by TBK1

Stimulator of interferon genes (STING) is essential for the type I interferon response induced by microbial DNA from virus or self-DNA from mitochondria/nuclei. In response to emergence of such DNAs in the cytosol, STING translocates from the endoplasmic reticulum (ER) to the Golgi, and activates TANK-binding kinase 1 (TBK1) at the trans-Golgi network (TGN). Activated TBK1 then phosphorylates STING at Ser365, generating an interferon regulatory factor 3 (IRF3)-docking site on STING. How this reaction proceeds specifically at the TGN remains poorly understood. Here we report a cell-free reaction in which endogenous STING is phosphorylated by TBK1. The reaction utilizes microsomal membrane fraction prepared from TBK1-knockout (KO) cells and recombinant TBK1. We observed agonist-, TBK1-, "ER-to-Golgi" traffic-, and palmitoylation-dependent phosphorylation of STING at Ser365, mirroring the nature of STING phosphorylation in vivo. Treating the microsomal membrane fraction with sphingomyelinase or methyl-{beta}-cyclodextrin, an agent to extract cholesterol from membranes, suppressed the phosphorylation of STING by TBK1. Given the enrichment of sphingomyelin and cholesterol in the TGN, these results may provide the molecular basis underlying the specific phosphorylation reaction of STING at the TGN.

cell biology↗

bioRxiv2020

Homeostatic regulation of STING by Golgi-to-ER membrane traffic

Coat protein complex I (COP-I) mediates the retrograde transport from the Golgi to the ER1,2. Mutation of the COPA gene, encoding one of the COP-I subunits (-COP), causes an immune dysregulatory disease (COPA syndrome)3. The molecular mechanism by which the impaired retrograde transport results in autoinflammation is not understood. Here we report that STING4, an innate immunity protein, is a cargo of the Golgi-to-ER membrane transport. In the presence of the disease-causative -COP variants, STING cannot be retrieved back to the ER from the Golgi. The forced Golgi residency of STING results in the cGAS-independent and palmitoylation-dependent activation of the STING downstream signalling pathway. Surf45, a protein that circulates between the ER and the Golgi, binds STING and -COP, and mediates retrograde transport of STING to the ER. STING/Surf4/-COP complex is disrupted in the presence of the disease-causative -COP variant. Intriguingly, the STING ligand cGAMP also impairs the formation of STING/Surf4/-COP complex. Our results suggest a homeostatic regulation of STING at the resting state by the Golgi-to-ER membrane traffic and provide insights into the pathogenesis of COPA syndrome.

cell biology↗