STING induces LUBAC-mediated synthesis of linear ubiquitin chains to stimulate innate immune signaling

STING activation by cyclic dinucleotides in mammals induces IRF3- and NF{kappa}B -mediated gene expression, and the lipidation of LC3B at Golgi-related membranes. While mechanisms of the IRF3 response are well understood, the mechanisms of NF{kappa}B activation mediated by STING remain unclear. We report 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 ubiquitin chains and reduces STING-induced NF{kappa}B and IRF3-mediated signaling in human monocytic THP1 cells and mouse bone marrow derived macrophages, without affecting STING activation. STING-induced LC3B lipidation is not required for M1-Ub chain formation or the immune-related gene expression, however the recently reported function of STING to neutralize the pH of the Golgi may be involved. Thus, LUBAC synthesis of M1 ubiquitin chains mediates STING-induced innate immune signaling.