STING primes stress granule assembly at the ER 2328483

Abstract

Abstract Introduction Stress granules (SGs) are stress-induced ribonucleoprotein condensates that are implicated in diverse diseases, including amyotrophic lateral sclerosis (ALS). How SG nucleation is primed prior to stress remains unclear. STING is an ER-resident adaptor known for DNA-sensing innate immune signaling. Analysis of STING interactomes revealed its associations with SG proteins, prompting us to investigate whether STING regulates SG formation. Methods SG assembly in wild-type and STING-deficient cells exposed to oxidative, heat, or ER stress was quantified by immunofluorescence. STING-associated interactions were examined using co-immunoprecipitation, proximity ligation assays, and TurboID-based proximity labeling. Domain mapping was performed using mutants of STING and the SG protein G3BP1. We assessed the role of ER tethering in SG pre-condensate formation, using a construct that anchors the G3BP1-interacting region of STING to the ER without its transmembrane domains. The impact of STING on ALS-associated TDP-43 mutant phenotypes was evaluated. Results Loss of STING reduced SG number and size independently of canonical STING signaling. STING interacted with the SG core proteins G3BP1 and UBAP2L under basal conditions, indicating the presence of ER-associated SG pre-condensates. Expression of an ER-anchored STING C-terminal domain restored SG formation and reduced stress-induced cell death in STING-deficient cells. STING also promoted cytoplasmic accumulation and aggregation of ALS-associated mutant TDP-43 and exacerbated mitochondrial dysfunction. Conclusion STING functions as an ER-resident scaffold that primes SG maturation by pre-organizing core components before overt stress, independently of innate immune signaling. This STING—SG axis links membrane scaffolding to condensate biology and provides a mechanistic connection to neurodegenerative pathology. Targeting STING interactions with SG proteins may offer a therapeutic strategy for diseases driven by aberrant SG assembly. Funding Source n/a Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)