The classic mode of STING activation is through binding the cyclic dinucleotide 2′3′-cyclic GMP–AMP (cGAMP), produced by the DNA sensor cyclic GMP–AMP synthase (cGAS), which is important for the innate immune response to microbial infection and autoimmune disease. Modes of STING activation that are independent of cGAS are much less well understood. Here, through a spatiotemporally resolved proximity labelling screen followed by quantitative proteomics, we identify the lysosomal membrane protein Niemann–Pick type C1 (NPC1) as a cofactor in the trafficking of STING. NPC1 interacts with STING and recruits it to the lysosome for degradation in both human and mouse cells. Notably, we find that knockout of Npc1 ‘primes’ STING signalling by physically linking or ‘tethering’ STING to SREBP2 trafficking. Loss of NPC1 protein also ‘boosts’ STING signalling by blocking lysosomal degradation. Both priming and boosting of STING signalling are required for severe neurological disease in the Npc1^−/− mouse. Genetic deletion of Sting1 (the gene that encodes STING) or Irf3, but not that of Cgas, significantly reduced the activation of microglia and relieved the loss of Purkinje neurons in the cerebellum of Npc1^−/− mice, leading to improved motor function. Our study identifies a cGAS- and cGAMP-independent mode of STING activation that affects neuropathology and provides a therapeutic target for the treatment of Niemann–Pick disease type C.

STING 激活的经典模式是通过结合由 DNA 传感器环状 GMP-AMP 合酶 (cGAS) 产生的环状二核苷酸 2'3'-环状 GMP-AMP (cGAMP)，这对于微生物感染的先天免疫反应很重要和自身免疫性疾病。独立于 cGAS 的 STING 激活模式鲜为人知。在这里，通过时空分辨的邻近标记筛选和定量蛋白质组学，我们将溶酶体膜蛋白 Niemann-Pick C1 型 (NPC1) 鉴定为 STING 运输的辅助因子。NPC1 与 STING 相互作用并将其募集到溶酶体中以在人和小鼠细胞中降解。值得注意的是，我们发现敲除Npc1通过将 STING 物理连接或“束缚”到 SREBP2 贩运来“启动”STING 信号传导。NPC1 蛋白的缺失还通过阻断溶酶体降解“增强”STING 信号传导。Npc1 ^-/-小鼠的严重神经系统疾病需要启动和增强 STING 信号传导。Sting1（编码 STING 的基因）或Irf3的基因缺失，但不是Cgas的基因缺失，显着降低了小胶质细胞的激活并减轻了Npc1小脑中浦肯野神经元的损失^-/-小鼠，从而改善运动功能。我们的研究确定了一种不依赖 cGAS 和 cGAMP 的 STING 激活模式，它影响神经病理学，并为治疗 C 型 Niemann-Pick 病提供了治疗靶点。