A conserved ion channel function of STING mediates noncanonical autophagy and cell death

The cGAS/STING pathway triggers inflammation upon diverse cellular stresses such as infection, cellular damage, aging, and diseases. STING also triggers noncanonical autophagy, involving LC3 lipidation on STING vesicles through the V-ATPase-ATG16L1 axis, as well as induces cell death. Although the proton pump V-ATPase senses organelle deacidification in other contexts, it is unclear how STING activates V-ATPase for noncanonical autophagy. Here we report a conserved channel function of STING in proton efflux and vesicle deacidification. STING activation induces an electron-sparse pore in its transmembrane domain, which mediates proton flux in vitro and the deacidification of post-Golgi STING vesicles in cells. A chemical ligand of STING, C53, which binds to and blocks its channel, strongly inhibits STING-mediated proton flux in vitro. C53 fully blocks STING trafficking from the ER to the Golgi, but adding C53 after STING arrives at the Golgi allows for selective inhibition of STING-dependent vesicle deacidification, LC3 lipidation, and cell death, without affecting trafficking. The discovery of STING as a channel opens new opportunities for selective targeting of canonical and noncanonical STING functions. Activated STING forms a highly conserved proton channel which deacidifies post-Golgi STING trafficking vesicles. The channel of STING is essential for noncanonical functions of the cGAS pathway, such as ATG8 lipidation onto single membranes (CASM) and cell death.STING activation induces an electron-sparse pore in its transmembrane domain, allowing for proton efflux. Ligand binding stimulates STING trafficking through the Golgi complex to perinuclear clusters of endosome-like, acidic vesicles. The channel of STING deacidifies post-Golgi trafficking vesicles, leading to the activation of V-ATPase-mediated LC3 lipidation, also known as noncanonical autophagy. Selectively blocking the channel of STING abrogates STING-dependent proton flux, vesicle deacidification, LC3 lipidation, and cell death. Activated STING forms a highly conserved proton channel which deacidifies post-Golgi STING trafficking vesicles. The channel of STING is essential for noncanonical functions of the cGAS pathway, such as ATG8 lipidation onto single membranes (CASM) and cell death.