Guanylate-Binding Protein 5 (GBP5) Exacerbates Sepsis by Inhibiting STING-mediated Post-Golgi Transport

Introduction/Rationale: Excessive activation of STING is associated with sepsis. Maintaining appropriate self-limiting mechanisms following STING activation is crucial. Upon activation, STING in the Golgi can be degraded via the lysosomal-autophagic pathway or recruited to COP I vesicles for retrograde transport back to the ER. GBP5 is localized to the Golgi and plays a crucial role in the immune response. However, its potential functional relationship with STING in sepsis remains unclear.

Methods: The role of GBP5 in sepsis was investigated by assessing inflammation and intestinal injury severity levels in WT/GBP5 KO mice. Subsequently, molecular docking and immunoprecipitation (IP) experiments identified a potential interaction between GBP5 and STING. Cellular experiments further evaluated the specific mechanism by which GBP5 inhibits STING-mediated post-Golgi transport.

Results: Elevated GBP5 expression was observed in sepsis patients, correlating positively with STING levels. Overexpression of GBP5 enhanced STING activation, while GBP5 KO inhibited STING phosphorylation. GBP5 interacts with STING via its ligand-binding domain, and this interaction is associated with the localization of GBP5 in the Golgi. Mass spectrometry analysis showed that GBP5 is associated with vesicle transport in the Golgi and autophagosome assembly. Following STING activation, co-localization between STING and the Golgi apparatus was significantly reduced in the GBP5 KO group. GBP5 overexpression inhibited autophagy, and in the GBP5 KO group, STING levels were reduced in the ER but elevated in the Golgi. Survival and intestinal injury outcomes were significantly improved in GBP5 KO mice following CLP.

Conclusion: GBP5 interacts with activated STING at the Golgi, exerting dual regulatory effects: preventing autophagic degradation of STING and inhibiting its retrograde transport to the ER. This enhances STING signaling, thereby exacerbating the inflammatory response and tissue damage caused by sepsis.