STING-OPTN signaling confers cytoprotection through TBK1-dependent mitophagy

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays an essential role in innate immunity. While recent studies have revealed its critical role in non-canonical autophagy independent of its immune function, its role in selective autophagy remains elusive. Here, we identify the cGAS-STING pathway as an upstream positive regulator of mitophagy. We demonstrate that activation of TANK-binding kinase 1 (TBK1) during mitophagy is strictly dependent on the cGAS-STING pathway. Mechanistically, TBK1 activation involves the mitochondrial recruitment of STING, which requires valosin-containing protein (VCP)/p97-mediated degradation of outer mitochondrial membrane proteins. Activated TBK1 then phosphorylates optineurin (OPTN), resulting in the efficient clearance of damaged mitochondria via the autophagosome-lysosome pathway. Disruption of the STING-OPTN axis impairs mitophagy, which switches cellular response from mitophagy to apoptosis. Our work thereby defines a non-canonical, pro-survival function of the cGAS-STING pathway in mitochondrial quality control.