Regulatory roles for MD-2 and TLR4 in ligand-induced receptor clustering

Makiko Kobayashi, Shin Ichiroh Saitoh, Natsuko Tanimura, Koichiro Takahashi, Kiyoshi Kawasaki, Masahiro Nishijima, Yukari Fujimoto, Koichi Fukase, Sachiko Akashi-Takamura, Kensuke Miyake

Research output: Contribution to journalArticlepeer-review

139 Citations (Scopus)


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 LPS, and the region from Phe119 to Lys132 (Arg132 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 Gly59 was found to be a novel critical amino acid for LPS binding outside the region 119-132. LPS 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 Phe126 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.

Original languageEnglish
Pages (from-to)6211-6218
Number of pages8
JournalJournal of Immunology
Issue number10
Publication statusPublished - 2006 May 15
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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