The cytoplasmic 'linker region' in Toll-like receptor 3 controls receptor localization and signaling
The cytoplasmic 'linker region' in Toll-like receptor 3 controls receptor localization and signaling
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DOI：
10.1093/intimm/dxh115
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发表时间：
2004-08-01
影响因子：
4.4
通讯作者：
Seya, T
中科院分区：
文献类型：
--
作者：
Funami, K;Matsumoto, M;Seya, T
Toll 样受体 3 (TLR3) 识别双链 RNA 并通过新鉴定的接头 TICAM-1 传递信号以激活 NF-kappaB 和干扰素 (IFN)-β 启动子。 TLR3 的胞外 LRR 结构域参与配体识别，而胞内 TIR 结构域对于配体刺激时的接头结合和信号转导至关重要。在这里，我们通过免疫荧光染色和共聚焦显微镜分析了人单核细胞来源的未成熟树突状细胞（iDC）和表达人 TLR3 的稳定转染子中的 TLR3 定位。 TLR3 主要位于特定但尚未鉴定的细胞内囊泡中，TLR3 信号传导在此启动。 TLR3 尾截短突变体的表达分析表明，细胞质“接头”区域（残基 730-755）决定了 TLR3 的细胞内定位。连接区的定点诱变使我们能够鉴定出 TLR3 细胞内表达的相关决定簇如 Arg(740) 和 Val(741) 残基。此外，连接区的丙氨酸扫描表明，TLR3细胞质连接区中的Phe(732)、Leu(742)和Gly(743)对于配体诱导的NF-κB和IFN-β启动子激活至关重要。因此，TLR3的细胞质连接区调节受体在细胞器内的保留和信号转导，这可能与DC中TLR3的功能密切相关。
Toll-like receptor 3 (TLR3) recognizes double-stranded RNA and transmits signals to activate NF-kappaB and the interferon (IFN)-beta promoter via the newly identified adaptor, TICAM-1. The extracellular LRR domain of TLR3 is engaged in the ligand recognition, while the intracellular TIR domain is crucial for the adaptor binding and signal transduction upon ligand stimulation. Here, we analyzed TLR3 localization in human monocyte-derived immature dendritic cells (iDCs) and stable transfectants expressing human TLR3 by immunofluorescence staining and confocal microscopy. TLR3 was predominantly localized in specific but as yet unidentified intracellular vesicles where TLR3 signaling was initiated. Expression analysis of TLR3-tail-truncated mutants revealed that the cytoplasmic 'linker' region (residues 730-755) determines the intracellular localization of TLR3. Site-directed mutagenesis of the linker region allowed us to identify the relevant determinants as Arg(740) and Val(741) residues for intracellular expression of TLR3. Furthermore, alanine scanning of the linker region demonstrated that the Phe(732), Leu(742) and Gly(743) in the TLR3 cytoplasmic linker region are essential for ligand-induced NF-kappaB and IFN-beta promoter activation. Thus, the cytoplasmic linker region of TLR3 regulates receptor retention inside the organelle and signaling, which may be closely linked to TLR3 function in DCs.