Regulatory roles for MD-2 and TLR4 in ligand-induced receptor clustering
Regulatory roles for MD-2 and TLR4 in ligand-induced receptor clustering
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DOI：
10.4049/jimmunol.176.10.6211
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发表时间：
2006-05-15
影响因子：
4.4
通讯作者：
Miyake, Kensuke
中科院分区：
文献类型：
--
作者：
Kobayashi, Makiko;Saitoh, Shin-ichiroh;Miyake, Kensuke
lp，一个委托人。在革兰氏阴性菌中的膜成分，被一个由TLR4和MD-2组成的受体复合体识别。MD-2是一种与TLR4细胞外结构域相关的细胞外分子，在LPS识别中起关键作用。MD-2直接与LIPS相互作用，从Phe（119）到Lys(132)（小鼠中Arg(132)）的区域已被证明是LPS与TLR4/MD-2相互作用的重要区域。在小鼠MD-2突变体中，我们在本研究中发现Gly（59）是LPS在119-132区外结合的一个新的关键氨基酸。LIPS信号被认为是由配体诱导的TLR4聚类触发的，而TLR4聚类也受MD-2调控。然而，我们对MD-2分子中调控配体诱导受体聚集的区域或氨基酸知之甚少。以丙氨酸取代Phe（126）或Gly（129）的MD-2突变体破坏了LPS诱导的TLR4聚类，但没有破坏LPS与TLR4/MD-2的结合，这表明配体诱导的受体聚类受到MD-2与配体结合的不同调节。我们进一步表明，配体诱导的受体聚集和配体与受体相互作用的解离以依赖于TLR4信号传导的方式发生，需要内体酸化。这些结果支持了MD-2在LPS识别中的主要作用。
LPS, a principal. membrane component in Gram-negative bacteria, is recognized by a receptor complex consisting of TLR4 and MD-2. MD-2 is an extracellular molecule that is associated with the extracellular domain of TLR4 and has a critical role in LPS recognition. MD-2 directly interacts with LIPS, and the region from Phe(119) to Lys(132) (Arg(132) in mice) has been shown to be important for interaction between LPS and TLR4/MD-2. With mouse MD-2 mutants, we show in this study that Gly(59) was found to be a novel critical amino acid for LPS binding outside the region 119-132. LIPS signaling is thought to be triggered by ligand-induced TLR4 clustering, which is also regulated by MD-2. Little is known, however, about a region or an amino acid in the MD-2 molecule that regulates ligand-induced receptor clustering. MD-2 mutants substituting alanine for Phe(126) or Gly(129) impaired LPS-induced TLR4 clustering, but not LPS binding to TLR4/MD-2, demonstrating that ligand-induced receptor clustering is differentially regulated by MD-2 from ligand binding. We further show that dissociation of ligand-induced receptor clustering and of ligand-receptor interaction occurs in a manner dependent on TLR4 signaling and requires endosomal acidification. These results support a principal role for MD-2 in LPS recognition.