Human TLR4 polymorphism D299G/T399I alters TLR4/MD-2 conformation and response to a weak ligand monophosphoryl lipid A
Human TLR4 polymorphism D299G/T399I alters TLR4/MD-2 conformation and response to a weak ligand monophosphoryl lipid A
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DOI：
10.1093/intimm/dxs084
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发表时间：
2013-01-01
影响因子：
4.4
通讯作者：
Miyake, Kensuke
中科院分区：
文献类型：
--
作者：
Yamakawa, Natsuko;Ohto, Umeharu;Miyake, Kensuke
疾病相关的TLR 4多态性影响配体诱导的二聚化。细胞表面的异源二聚体Toll样受体4（TLR 4）/MD-2感知脂多糖（LPS），脂多糖是革兰氏阴性菌的主要膜成分。LPS与MD-2结合并诱导TLR 4/MD-2的二聚化。二聚化TLR 4激活下游信号传导。TLR 4基因多态性（D299 G/T399 I）导致LPS低反应性，并与多种感染性和非感染性疾病相关。然而，LPS低反应性的分子机制仍然存在争议。我们在此询问TLR 4多态性是否影响TLR 4/MD-2的细胞表面表达、配体依赖性TLR 4/MD-2二聚化或TLR 4/MD-2对弱激动剂单磷酰脂质A（MPL）的反应。新建立的抗TLR 4 mAb检测到Ba/F3细胞上的D299 G/T399 I TLR 4/MD-2，而之前的抗TLR 4 mAb检测到了，这是否符合上面的线？，提示D299 G/T399 I多态性引起TLR 4的构象变化。MPL对D299 G/T399 I/TLR 4/MD-2细胞的低反应性比脂质A更明显。D299 G/T399 I多态性损害了MPLS依赖的TLR 4/MD-2二聚化。D299 G/T399 I多态性不改变LPS与可溶性TLR 4/MD-2的结合，但损害其二聚化。这些结果表明D299 G/T399 I TLR 4多态性通过改变配体依赖性二聚化来损害TLR 4/MD-2应答。
Disease-associated TLR4 polymorphisms affect ligand-induced dimerization.A cell surface heterodimer Toll-like receptor 4 (TLR4)/MD-2 senses lipopolysaccharide (LPS), a principal membrane component of Gram-negative bacteria. LPS binds to MD-2 and induces dimerization of TLR4/MD-2. Dimerized TLR4 activates downstream signaling. TLR4 polymorphism replacing Asp299 with Gly and Thr399 with Ile (D299G/T399I) causes LPS hyporesponsiveness, and is associated with a variety of infectious and noninfectious diseases. However, a molecular mechanism underlying the LPS hyporesponsiveness remains controversial. We here asked whether the TLR4 polymorphism influenced cell surface expression of TLR4/MD-2, ligand-dependent TLR4/MD-2 dimerization or TLR4/MD-2 responses to a weak agonist monophosphoryl lipid A (MPL). A newly established anti-TLR4 mAb detected D299G/T399I TLR4/MD-2 on Ba/F3 cells, whereas a previous anti-TLR4 mAb did will this fit on the line above?, suggesting that the D299G/T399I polymorphism caused a conformational change in TLR4. Hyporesponsiveness of D299G/T399I TLR4/MD-2 was much more apparent when cells were stimulated with MPL than with lipid A. MPL-dependent TLR4/MD-2 dimerization was impaired by the D299G/T399I polymorphism. The D299G/T399I polymorphism did not alter LPS-binding to soluble TLR4/MD-2, but impaired its dimerization. These results suggest that the D299G/T399I TLR4 polymorphism impairs TLR4/MD-2 responses by altering ligand-dependent dimerization.