STING induces HOIP-mediated synthesis of M1 ubiquitin chains to stimulate NF-κB signaling

STING activation by cyclic dinucleotides induces IRF3- and NF-κB-mediated gene expression in mammals, as well as lipidation of LC3B at Golgi-related membranes. While mechanisms of the IRF3 response are well understood, the mechanisms of NF-κB activation via STING remain unclear. We report here that STING activation induces linear/M1-linked ubiquitin chain (M1-Ub) formation and recruitment of the LUBAC E3 ligase, HOIP, to LC3B-associated Golgi membranes where ubiquitin is also localized. Loss of HOIP prevents formation of M1-Ub chains and reduces STING-induced NF-κB and IRF3 signaling in human THP1 monocytes and mouse bone marrow-derived macrophages, without affecting STING activation. STING-induced LC3B lipidation is not required for M1-Ub chain formation or for immune-related gene expression, but the recently reported STING function in neutralizing Golgi pH may be involved. Thus, LUBAC synthesis of M1-linked ubiquitin chains mediates STING-induced innate immune signaling. Synopsis Upon activation, STING traffics to the Golgi and induces NF-κB signaling through poorly understood mechanisms. This study shows that E3 ligase HOIP recruitment to STING-positive Golgi-related vesicles leads to generation of M1-linked ubiquitin chains that stimulate the NF-κB innate immune response. STING activation induces ubiquitin localization at LC3B- and STING-associated Golgi vesicles, and M1- and K63-linked polyubiquitin chain formation. The LUBAC E3 ligase HOIP is recruited to LC3B- and STING-associated Golgi vesicles and activated to synthesize M1 ubiquitin chains. M1-linked ubiquitin chain formation by HOIP stimulates NF-κB-mediated signaling and gene expression upon STING activation. STING-induced LC3B lipidation is not required for M1-linked ubiquitination or immune gene expression, but affects perinuclear localization of HOIP and ubiquitin chains following STING activation. STING signals to NF-κB through the ubiquitination of Golgi vesicles.