Mechanism of nucleic acid recognition by endosomal Toll-like receptor 3

合成的病毒双链RNA类似物poly （I:C）在细胞外激活内体toll样受体（TLR） 3和细胞质RNA解旋酶（黑色素瘤分化相关基因5），导致I型干扰素（ifn）和炎症细胞因子的产生，以及树突状细胞（DC）的成熟。细胞外多聚物（I:C）传递到tlr3阳性细胞器和细胞质的机制尚不清楚。在这项研究中，我们证明了细胞质脂筏蛋白Raftlin对于人类髓系DCs和上皮细胞的聚（I:C）细胞摄取至关重要。当Raftlin被沉默时，poly （I:C）不能进入细胞，诱导IFN-β的产生受到抑制。在poly （I:C）刺激下，Raftlin从细胞质转移到质膜，与poly （I:C）共定位，然后移动到tlr3阳性内体。在响应poly （I:C）的质膜上，Raftlin与网格蛋白物理结合。因此，Raftlin与网格蛋白- ap -2复合物协同介导poly （I:C）进入细胞，这对TLR3的激活至关重要。

The synthetic virus double-stranded RNA analogue, poly (I:C), extracellularly activates both the endosomal Toll-like receptor (TLR) 3 and the cytoplasmic RNA helicase, melanoma differentiation-associated gene 5, leading to the production of type I interferons (IFNs) and inflammatory cytokines, and dendritic cell (DC) maturation. The mechanism by which extracellular poly(I:C) is delivered to TLR3-positive organelles and the cytoplasm remains to be elucidated. In this study, we demonstrate that the cytoplasmic lipid raft protein, Raftlin, is essential for poly (I:C) cellular uptake in human myeloid DCs and epithelial cells. When Raftlin was silenced, poly (I:C) failed to enter cells and induction of IFN-β production was inhibited. Upon poly (I:C) stimulation, Raftlin was translocated from the cytoplasm to the plasma membrane where it colocalized with poly (I:C), and thereafter moved to TLR3-positive endosomes. Raftlin physically associated with clathrin at the plasma membrane in response to poly (I:C). Thus, Raftlin cooperates with the clathrin-AP-2 complex to mediate cell entry of poly (I:C), which is critical for activation of TLR3.