A STING antagonist modulating the interaction with STIM1 blocks ER-to-Golgi trafficking and inhibits lupus pathology.

Background: Nucleic acids are potent stimulators of type I interferon (IFN-I) and antiviral defense, but may also promote pathological inflammation. A range of diseases are characterized by elevated IFN-I, including systemic lupus erythematosus (lupus). The DNA-activated cGAS-STING pathway is a major IFN-I-inducing pathway, and activation of signaling is dependent on trafficking of STING from the ER to the Golgi.

Methods: Here we used cell culture systems, a mouse lupus model, and material from lupus patients, to explore the mode of action of a STING antagonistic peptide, and its ability to modulate disease processes.

Findings: We report that the peptide ISD017 selectively inhibits all known down-stream activities of STING, including IFN-I, inflammatory cytokines, autophagy, and apoptosis. ISD017 blocks the essential trafficking of STING from the ER to Golgi through a mechanism dependent on the STING ER retention factor STIM1. Importantly, ISD017 blocks STING activity in vivo and ameliorates disease development in a mouse model for lupus. Finally, ISD017 treatment blocks pathological cytokine responses in cells from lupus patients with elevated IFN-I levels.

Interpretation: These data hold promise for beneficial use of STING-targeting therapy in lupus.

Funding: The Novo Nordisk Foundation, The European Research Council, The Lundbeck Foundation, European Union under the Horizon 2020 Research, Deutsche Forschungsgemeinschaft, Chulalongkorn University.