Quantitative single-molecule imaging of TLR4 reveals ligand-specific receptor dimerization
Quantitative single-molecule imaging of TLR4 reveals ligand-specific receptor dimerization
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DOI：
10.1126/scisignal.aan1308
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发表时间：
2017-10-31
影响因子：
7.3
通讯作者：
Heilemann, Mike
中科院分区：
文献类型：
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作者：
Krueger, Carmen L.;Zeuner, Marie-Theres;Heilemann, Mike
在人类中，入侵的病原体由Toll样受体(TLRs)识别。当TLR4被革兰氏阴性菌细胞壁的脂多糖识别后，TLR4发生二聚化，并可激活两条不同的信号通路，一条是依赖于MyD88的促炎性通路，另一条是非依赖于MyD88的抗病毒通路。这两条通路之间的平衡依赖于配体，而配体组成决定了入侵的病原体是激活还是逃避宿主的免疫反应。我们通过定量单分子定位显微镜研究了TLR4在完整细胞中的二聚化行为，以响应不同的内毒素化学类型。定量超分辨数据显示，在没有辅助受体MD2和CD14的情况下，TLR4在HEK 293细胞中是单体。当TLR4与MD2、CD14同时存在时，52%的受体为单体受体，48%的受体为二聚体。来自大肠杆菌或明尼苏达沙门氏菌的内毒素可引起二聚体TLR4复合体的形成，而来自球形红杆菌的拮抗内毒素化学型使TLR4在细胞表面以单体形式存在。此外，我们还发现，激活核因子-kappaB信号需要依赖于内毒素的二聚化。综上所述，这些数据证明了TLR4在细胞环境中的配体依赖的二聚化，这可能为分子理解受体下游的偏向信号铺平道路。
In humans, invading pathogens are recognized by Toll-like receptors (TLRs). Upon recognition of lipopolysaccharide (LPS) derived from the cell wall of Gram-negative bacteria, TLR4 dimerizes and can stimulate two different signaling pathways, the proinflammatory, MyD88-dependent pathway and the antiviral, MyD88-independent pathway. The balance between these two pathways is ligand-dependent, and ligand composition determines whether the invading pathogen activates or evades the host immune response. We investigated the dimerization behavior of TLR4 in intact cells in response to different LPS chemotypes through quantitative single-molecule localization microscopy. Quantitative superresolved data showed that TLR4 was monomeric in the absence of its co-receptors-MD2 and CD14 in transfected HEK 293 cells. When TLR4 was present together with MD2 and CD14 but in the absence of LPS, 52% of the receptors were monomeric and 48% were dimeric. LPS from Escherichia coli or Salmonella minnesota caused the formation of dimeric TLR4 complexes, whereas the antagonistic LPS chemotype from Rhodobacter sphaeroides maintained TLR4 in monomeric form at the cell surface. Furthermore, we showed that LPS-dependent dimerization was required for the activation of NF-kappa B signaling. Together, these data demonstrate ligand-dependent dimerization of TLR4 in the cellular environment, which could pave the way for a molecular understanding of biased signaling downstream of the receptor.