Mannose binding lectin and lung collectins interact with Toll-like receptor 4 and MD-2 by different mechanisms.
Mannose binding lectin and lung collectins interact with Toll-like receptor 4 and MD-2 by different mechanisms.
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DOI：
10.1016/j.bbagen.2009.10.006
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发表时间：
2009-12
期刊：
影响因子：
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通讯作者：
Takeyuki Shimizu;C. Nishitani;H. Mitsuzawa;S. Ariki;Motoko Takahashi;K. Ohtani;N. Wakamiya;Y. Kuroki
中科院分区：
文献类型：
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作者：
Takeyuki Shimizu;C. Nishitani;H. Mitsuzawa;S. Ariki;Motoko Takahashi;K. Ohtani;N. Wakamiya;Y. Kuroki
背景我们以前已经证明肺胶原蛋白，表面活性蛋白A（SP-A）和表面活性蛋白D，与Toll样受体（TLR）2，TLR 4或MD-2相互作用。肺聚集蛋白与TLR 2和TLR 4/MD-2的结合导致通过这些受体的信号传导的改变，提示肺聚集蛋白的免疫调节功能。甘露糖结合凝集素（MBL）是另一种与SP-A具有结构同源性的凝集素分子。方法制备重组MBL，分析其与重组可溶性TLR 4（sTLR 4）和MD-2的结合情况，并测定其与sTLR 4和MD-2的结合情况。这种相互作用是钙离子依赖性的，并被甘露糖或单克隆抗体抑制。用肽N-糖苷酶F处理sTLR 4或MD-2显著降低MBL的结合。SP-A与去糖基化的sTLR 4结合，而在SP-A/MBL嵌合分子中，当SP-A的Glu 195-Phe 228或Thr 174-Gly 194被相应的MBL序列取代时，这一特性没有改变。由于我们以前的研究表明肺凝集素结合TLRs的肽部分，MBL和肺凝集素通过不同的机制与TLRs相互作用。一般意义MBL和TLR 4或MD-2之间的这些直接相互作用表明，MBL可能通过改变TLRs的信号来调节细胞反应。
BACKGROUNDWe have previously shown that lung collectins, surfactant proteins A (SP-A) and surfactant proteins D, interact with Toll-like receptor (TLR) 2, TLR4, or MD-2. Bindings of lung collectins to TLR2 and TLR4/MD-2 result in the alterations of signaling through these receptors, suggesting the immunomodulatory functions of lung collectins. Mannose binding lectin (MBL) is another collectin molecule which has structural homology to SP-A. The interaction between MBL and TLRs has not yet been determined.METHODSWe prepared recombinant MBL, and analyzed its bindings to recombinant soluble forms of TLR4 (sTLR4) and MD-2.RESULTSMBL bound to sTLR4 and MD-2. The interactions were Ca2+-dependent and inhibited by mannose or monoclonal antibody against the carbohydrate-recognition domain of MBL. Treatment of sTLR4 or MD-2 by peptide N-glycosidase F significantly decreased the binding of MBL. SP-A bound to deglycosylated sTLR4, and this property did not change in chimeric molecules of SP-A/MBL in which Glu195–Phe228or Thr174–Gly194of SP-A were replaced with the corresponding MBL sequences.CONCLUSIONSThese results suggested that MBL binds to TLR4 and MD-2 through the carbohydrate-recognition domain, and that oligosaccharide moieties of TLR4 and MD-2 are important for recognition by MBL. Since our previous studies indicated that lung collectins bind to the peptide portions of TLRs, MBL and lung collectins interact with TLRs by different mechanisms.GENERAL SIGNIFICANCEThese direct interactions between MBL and TLR4 or MD-2 suggest that MBL may modulate cellular responses by altering signals through TLRs.