ZBP1 sequesters cGAS in the cytoplasm and sustains type I interferon responses to mitochondrial DNA

Abstract

Mitochondrial DNA (mtDNA) is a potent agonist of the innate immune system; however, the exact immunostimulatory features of mtDNA and the kinetics of mtDNA detection by cytosolic nucleic acid sensors remain poorly defined. Here, we show that mitochondrial genome instability leads to Z-form mtDNA accumulation. Z-DNA Binding Protein 1 (ZBP1) stabilizes Z-form mtDNA and nucleates a cytosolic complex containing cGAS, RIPK1, and RIPK3 to sustain STAT1 phosphorylation and type I interferon (IFN-I) signaling. Increased mitochondrial Z-DNA, ZBP1 expression, and IFN-I responses are observed in cardiomyocytes after exposure to Doxorubicin, a first-line chemotherapeutic agent that induces frequent cardiotoxicity in cancer patients. Strikingly, mice lacking ZBP1 or IFN-I signaling are protected from Doxorubicin-induced cardiotoxicity. Our findings reveal ZBP1 as a cooperative partner for cGAS that sustains IFN-I responses to mitochondrial genome instability and highlight ZBP1 as a potential target in heart failure and other disorders where mtDNA stress contributes to interferon-related pathology.