IRG1 catalyzed energy metabolite itaconic acid restrains type I interferon-dependent immune responses by alkylation of TBK1.

Perturbation of energy metabolism is an essential feature during infection and inflammation. TANK-binding kinase 1 (TBK1) is crucial for initiating the innate immune response against viral infection, although aberrant and ongoing TBK1 activation induces excessive production of type I interferons (IFN-I). Nonetheless, the mechanisms whereby energy metabolism controls TBK1 activation remain unclear. Here, we elucidate a mechanism linking energy metabolism to the inhibition of TBK1-induced IFN-I responses via the immune response gene 1 (IRG1)-itaconic acid axis. Mechanistically, itaconic acid and its derivatives alkylated TBK1 at Cys605, thereby disrupting TBK1 dimerization and rapid activation. IRG1, the enzyme that catalyzes itaconic acid production, is upregulated during late-phase viral infection and acts as a feedback regulator to restrain TBK1 activity. We developed itaconic acid-based compounds ITA-5/ITA-9 as alternative TBK1 inhibitors. ITA-5/ITA-9 effectively limited excess IFN-I-mediated hyperinflammation. These findings provide a promising therapeutic strategy for treating diseases mediated by aberrant TBK1 activation.