Metabolic signals critically shape innate immune responses. Through pharmacological screening of metabolic pathways, we identified aspartate metabolism as a key regulator of cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling. Genetically or aminooxyacetic acid-mediated (AOA-mediated) pharmacologically reducing aspartate levels markedly potentiated the cGAS-STING pathway, leading to stronger upregulation of type I interferons and interferon-stimulated genes. Mechanistically, disruption of de novo pyrimidine synthesis, a major downstream pathway of aspartate, induced mtDNA replication stress and increased mtDNA double-strand breaks, promoting mtDNA release into the cytosol. Cytosolic mtDNA synergized with cGAS-STING agonists to upregulate Z-DNA binding protein 1 (ZBP1), which recruits RIPK1/3 to sustain IRF3 phosphorylation, forming a positive feedback loop that amplifies innate immune signaling. In immunocompetent mouse models, AOA enhanced the antitumor efficacy of STING agonists, chemotherapy, or radiotherapy, whereas aspartate supplementation abrogated these effects. Consistently, aspartate levels negatively correlated with antitumor immunity in colorectal cancer patient samples. Together, our study identifies aspartate-pyrimidine metabolism as a critical metabolic checkpoint that licenses STING signaling by enabling mtDNA stress to cooperate with agonist stimulation, driving type I interferon-dependent ZBP1 induction and feed-forward amplification of STING signaling, thus offering a promising strategy to enhance antitumor immunity.
Liao et al. (Mon,) studied this question.