Abstract COPA syndrome is caused by loss-of-function mutations in the COP-α subunit of coatomer protein complex I (COPI), which participates in retrograde vesicular trafficking of proteins from the Golgi to the endoplasmic reticulum (ER). Disease manifests early in life with arthritis, lung pathology, kidney dysfunction and systemic inflammation associated with NF-κB activation and type I interferon (IFNαβ) production. Here, we generated in vitro models for COPA syndrome and interrogated inflammatory signalling pathways via a range of biochemical and molecular biological techniques. Results were confirmed with cell lines in which mutant COPA was overexpressed and with COPA syndrome patient PBMCs. We identified Stimulator of Interferon Genes (STING), as a driver of inflammation in COPA syndrome. Furthermore, we found that genetic deletion of COPG1, another COPI subunit protein, induced NF-κB and type I IFN pathways similar to COPA-deficiency. Finally, we demonstrate that in vitro , inflammation due to COPA syndrome mutations was ameliorated by treatment with the small molecule STING inhibitor H-151. Therefore, inflammation induced by deletion of COPI subunits in general suggests a link between retrograde trafficking and STING regulation, and this innate immune sensor represents a novel therapeutic target in COPA syndrome.

Activation of STING due to COPI-deficiency