The TLR3 signaling complex forms by cooperative receptor dimerization
The TLR3 signaling complex forms by cooperative receptor dimerization
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DOI：
10.1073/pnas.0710779105
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发表时间：
2008-01-08
影响因子：
11.1
通讯作者：
Segal, David M.
中科院分区：
文献类型：
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作者：
Leonard, Joshua N.;Ghirlando, Rodolfo;Segal, David M.
Toll样受体（TLR）通过识别病原体相关分子启动免疫应答，但识别的分子基础知之甚少。特别是受体-配体相互作用如何导致下游信号传导的启动尚不清楚。在这里，我们描述了TLR 3识别其配体双链RNA（dsRNA）并形成活性信号复合物的机制。我们表明，dsRNA饱和结合，特异性，可逆的TLR 3胞外域（TLR 3ecd）上的一个定义的配体结合位点（或网站）。结合亲和力随缓冲液酸度和配体大小而增加。纯化的TLR 3ecd蛋白在溶液中仅为单体，但通过高度协同的过程，其在与dsRNA结合时形成二聚体，并且多个TLR 3ecd二聚体与长dsRNA链结合。与TLR 3ecd形成稳定复合物的最小dsRNA寡核苷酸（40-50 bp）各自结合一个TLR 3ecd二聚体，并且这些也是有效激活细胞中TLR 3的最小寡核苷酸。我们得出结论，TLR 3组装dsRNA作为稳定的二聚体，最小的信号单元是一个TLR 3二聚体。
Toll-like receptors (TLRs) initiate immune responses by recognizing pathogen-associated molecules, but the molecular basis for recognition is poorly understood. in particular, it is unclear how receptor-ligand interactions lead to the initiation of downstream signaling. Here, we describe the mechanism by which TLR3 recognizes its ligand, double-stranded RNA (dsRNA), and forms an active signaling complex. We show that dsRNA binds saturably, specifically, and reversibly to a defined ligand-binding site (or sites) on the TLR3 ectodomain (TLR3ecd). Binding affinities increase with both buffer acidity and ligand size. Purified TLR3ecd protein is exclusively monomeric in solution, but through a highly coopera tive process, it forms dimers when bound to dsRNA, and multiple TLR3ecd dimers bind to long dsRNA strands. The smallest dsRNA oligonucleotides that form stable complexes with TLR3ecd (40-50 bp) each bind one TLR3ecd dinner, and these are also the smallest oligonucleotides that efficiently activate TLR3 in cells. We conclude that TLR3 assembles on dsRNA as stable dimers and that the minimal signaling unit is one TLR3 dimer.