Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.
J Immunol. 2010 Dec 15;185(12):7614-22. doi: 10.4049/jimmunol.1002760. Epub 2010 Nov 8.
TLR9 recognizes unmethylated CpG DNA and induces innate immune responses. TLR9 activation is a multistep process requiring proteolytic cleavage and trafficking to endolysosomal compartments for ligand-induced signaling. However, the rules that govern the dynamic subcellular trafficking for TLR9 after pathogen uptake have not been established. In this study, we demonstrate that uptake of Aspergillus fumigatus conidia induced drastic spatial redistribution of TLR9 to the phagosomal membrane of A. fumigatus-containing phagosomes but not to bead-containing phagosomes in murine macrophages. Specific TLR9 recruitment to the fungal phagosome was consistent using A. fumigatus spores at different germination stages and selected mutants affecting the display of Ags on the fungal cell surface. Spatiotemporal regulation of TLR9 compartmentalization to the A. fumigatus phagosome was independent of TLR2, TLR4, and downstream TLR signaling. Our data demonstrate that the TLR9 N-terminal proteolytic cleavage domain was critical for successful intracellular trafficking and accumulation of TLR9 in CpG-containing compartments and A. fumigatus phagosomal membranes. Our study provides evidence for a model in which A. fumigatus spore phagocytosis by macrophages specifically induces TLR9 recruitment to A. fumigatus phagosomes and may thereby mediate TLR9-induced antifungal innate immune responses.
TLR9 识别未甲基化的 CpG DNA 并诱导先天免疫反应。TLR9 的激活是一个多步骤的过程，需要蛋白水解切割和运输到内体溶酶体隔间，以进行配体诱导的信号转导。然而，尚不清楚病原体摄取后 TLR9 的动态细胞内运输规则。在这项研究中，我们证明了烟曲霉分生孢子的摄取导致 TLR9 剧烈的空间重分布到含有烟曲霉的吞噬体的吞噬体膜上，但不分布到含有珠体的吞噬体上。使用处于不同萌发阶段的烟曲霉孢子和影响真菌细胞表面 Ag 展示的选定突变体，均观察到 TLR9 被特异性招募到真菌吞噬体上。TLR9 区室化到烟曲霉吞噬体的时空调节独立于 TLR2、TLR4 和下游 TLR 信号。我们的数据表明，TLR9 N 端蛋白水解切割结构域对于 TLR9 在含 CpG 区室和烟曲霉吞噬体膜中的成功细胞内运输和积累是至关重要的。我们的研究提供了证据表明，巨噬细胞吞噬烟曲霉孢子特异性地诱导 TLR9 招募到烟曲霉吞噬体，并可能介导 TLR9 诱导的抗真菌先天免疫反应。
