ARMH3-mediated recruitment of PI4KB directs Golgi-to-endosome trafficking and activation of the antiviral effector STING

The cGAS-STING pathway mediates cytoplasmic DNA-triggered innate immunity. STING activation is initiated by cyclic-GMP-AMP (cGAMP)-induced translocation from the endoplasmic reticulum and sulfated glycosaminoglycans-induced polymerization at the Golgi. Here, we examine the mechanisms underlying STING transport and activation beyond the Golgi. A genome-wide CRISPR-Cas9 screen identified Armadillo-like helical domain-containing protein 3 (ARMH3) as critical for STING activation. Upon cGAMP-triggered translocation, ARMH3 interacted with STING at the Golgi and recruited phosphatidylinositol 4-kinase beta (PI4KB) to synthesize PI4P, which directed STING Golgi-to-endosome trafficking via PI4P-binding proteins AP-1 and GGA2. Disrupting PI4P-dependent lipid transport through RNAi of other PI4P-binding proteins impaired STING activation. Consistently, disturbed lipid composition inhibited STING activation, whereas aberrantly elevated cellular PI4P led to cGAS-independent STING activation. Armh3(fl/fll)Lyz(Cre/Cre) mice were susceptible to DNA virus challenge in vivo. Thus, ARMH3 bridges STING and PIK4B to generate PI4P for STING transportation and activation, an interaction conserved in all eukaryotes.

Automated summary

The cGAS-STING pathway is involved in cytoplasmic DNA-induced innate immune response. STING is activated through translocation from the endoplasmic reticulum and polymerization at the Golgi triggered by cyclic-GMP-AMP (cGAMP) and sulfated glycosaminoglycans, respectively. This study reveals that Armadillo-like helical domain-containing protein 3 (ARMH3) is critical for STING activation and acts as a bridge between STING and phosphatidylinositol 4-kinase beta (PI4KB) to generate PI4P, which directs STING trafficking from the Golgi to endosomes through PI4P-binding proteins AP-1 and GGA2.