Analysis of Tlr4-mediated LPS signal transduction in macrophages by mutational modification of the receptor

X. Du, A. Poltorak, M. Silva, B. Beutler

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Abstract

In mouse macrophages (RAW 264.7 cells), toll-like receptor 4 (Tlr4) is a limiting factor in lipopolysaccharide (LPS) signal transduction. The expression of only 1-2 X 104 copies of recombinant Tlr4 per cell enhances sensitivity to LPS, shifting the EC50 by 30-fold to the left. Expression of the Tlr4(Lps-d) isoform of Tlr4 (found in C3H/HeJ mice) shifts the EC50 2600- fold to the right, essentially abolishing LPS responses. A truncated form of Tlr4, lacking a cytoplasmic domain, exerts only a weak inhibitory effect on signal transduction. Similarly, the normal or Tlr4(Lps-d) forms of protein lacking a cytoplasmic domain, cause modest inhibition of LPS signaling. Manipulations of Tlr4 structure and expression cause changes in LPS sensitivity that range over 3 to 4 orders of magnitude. These findings support the view that Tlr4 is an integral component of a solitary pathway for LPS signal transduction in macrophages and permit inferences related to the mechanism of signaling and its blockade. (C) 1999 Academic Press.

Original languageEnglish (US)
Pages (from-to)328-338
Number of pages11
JournalBlood Cells, Molecules, and Diseases
Volume25
Issue number5-6
Publication statusPublished - 1999

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Keywords

  • Endotoxin
  • Macrophage
  • Mutagenesis
  • Receptor
  • Toll-like receptor 4

ASJC Scopus subject areas

  • Molecular Biology
  • Molecular Medicine
  • Hematology

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