A type I interferon-mitochondrial axis regulates efferocytosis and interferon-stimulated gene induction in macrophages.

Macrophage metabolism is intricately linked to cellular function. Contrasting with Toll-like receptor (TLR) stimulation, cytosolic nucleic acid sensing induced a decrease in mitochondrial membrane potential (MMP) while maintaining mitochondrial respiration. Interferon α/β (IFN-I) receptor (IFNAR) signaling was necessary and sufficient for this metabolic response. IFNAR signaling induced interferon-stimulated gene 15 (ISG15) expression and ISGylation of mitochondrial proteins, including subunits of mitochondrial complex V, increasing ATP production and decreasing MMP, thus enhancing macrophage efferocytic capacity. Moreover, the IFNAR-ISG15-mediated drop in MMP activated the mitochondrial protease OMA1, inducing mitochondrial fission and decreasing endoplasmic reticulum-mitochondria communication, thus dampening IFN-stimulated gene (ISG) induction. Loss of ISG15 or OMA1 enhanced histone acetylation and ISG induction upon IFN-I stimulation, in a manner dependent on mitochondrial calcium uptake. This increase in ISG induction provided protection against acute viral infections. These data indicate that IFNAR-ISG15 signaling boosts efferocytosis while limiting ISG induction, thereby promoting the resolution of inflammation.