Toll-like receptor 9 (TLR9) recognizes DNA in endosomes and activates distinct signaling pathways to stimulate the production of proinflammatory cytokines and type I interferons (IFNs). The assembly of signaling platforms on microtubule-associated proteins 1A/1B–light chain 3 (LC3)–decorated endosomal vesicles is required to transduce TLR9 signals that stimulate the production of IFN but not interleukin-12 p40 (IL-12p40). LC3-associated phagocytosis (LAP), a form of noncanonical autophagy, is critical for the activation of interferon regulatory factor 7 (IRF7) and for IFN synthesis. We showed that after the stimulation of TLR9 by CpG oligonucleotides, the autophagy protein LC3 and the kinase IKKα were recruited to endosomes that contained TLR9. The recruitment of IKKα and LC3 to such signaling endosomes was not stimulated by catalysts of classical autophagosome formation but involved LAP formation, which required ATG5 but not FIP200. In addition, we found that the LC3-IKKα complex further associated with both TRAF3 and IRF7. We identified three putative LC3-interacting regions (LIRs) in IKKα, and mutagenesis suggested that two of these were critical for direct binding to LC3. Moreover, mutation of the same LIR sequences failed to rescue type I IFN production in IKKα-deficient dendritic cells upon reconstitution. Together, these data suggest a direct link between LAP formation and IKKα recruitment downstream of TLR9 activation that is necessary to facilitate type I IFN production.

Toll样受体9（TLR9）识别内体中的DNA并激活不同的信号传导途径，以刺激促炎性细胞因子和I型干扰素（IFN）的产生。在微管相关蛋白1A / 1B-轻链3（LC3）-修饰的内体囊泡上组装信号平台需要转导TLR9信号，该信号刺激IFN的产生，但不刺激白介素12 p40（IL-12p40）的产生。LC3相关的吞噬作用（LAP），一种非典型的自噬形式，对于干扰素调节因子7（IRF7）的激活和IFN的合成至关重要。我们显示，在CpG寡核苷酸刺激TLR9之后，自噬蛋白LC3和激酶IKKα被募集到含有TLR9的内体中。IKKα和LC3募集到此类信号传递内体不受经典自噬体形成催化剂的刺激，但涉及LAP形成，这需要ATG5而不是FIP200。另外，我们发现LC3-IKKα复合物进一步与TRAF3和IRF7相关。我们在IKKα中鉴定出三个推定的LC3相互作用区域（LIR），诱变表明其中两个对于直接结合LC3至关重要。而且，相同的LIR序列的突变在重建后未能挽救IKKα缺陷型树突状细胞中I型IFN的产生。总之，这些数据表明，LAP形成与TLR9激活下游的IKKα募集之间存在直接联系，这对促进I型IFN的产生必不可少。我们发现LC3-IKKα复合物进一步与TRAF3和IRF7相关。我们在IKKα中鉴定出三个推定的LC3相互作用区域（LIR），诱变表明其中两个对于直接结合LC3至关重要。而且，相同的LIR序列的突变在重建后未能挽救IKKα缺陷型树突状细胞中I型IFN的产生。总之，这些数据表明，LAP形成与TLR9激活下游的IKKα募集之间存在直接联系，这对促进I型IFN的产生必不可少。我们发现LC3-IKKα复合物进一步与TRAF3和IRF7相关。我们在IKKα中鉴定出三个推定的LC3相互作用区域（LIR），诱变表明其中两个对于直接结合LC3至关重要。而且，相同的LIR序列的突变在重建后未能挽救IKKα缺陷型树突状细胞中I型IFN的产生。总之，这些数据表明，LAP形成与TLR9激活下游的IKKα募集之间存在直接联系，这对促进I型IFN的产生必不可少。重建后，相同LIR序列的突变未能挽救IKKα缺陷型树突状细胞中I型IFN的产生。总之，这些数据表明，LAP形成与TLR9激活下游的IKKα募集之间存在直接联系，这对促进I型IFN的产生必不可少。重建后，相同LIR序列的突变未能挽救IKKα缺陷型树突状细胞中I型IFN的产生。总之，这些数据表明，LAP形成与TLR9激活下游的IKKα募集之间存在直接联系，这对促进I型IFN产生是必需的。