Conformationally constrained lipid A mimetics for exploration of structural basis of TLR4/MD-2 activation by lipopolysaccharide

ACS Chem Biol. 2013 Nov 15;8(11):2423-32. doi: 10.1021/cb4003199. Epub 2013 Sep 26.


Recognition of the lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, by the Toll-like receptor 4 (TLR4)-myeloid differentiation factor 2 (MD-2) complex is essential for the control of bacterial infection. A pro-inflammatory signaling cascade is initiated upon binding of membrane-associated portion of LPS, a glycophospholipid Lipid A, by a coreceptor protein MD-2, which results in a protective host innate immune response. However, activation of TLR4 signaling by LPS may lead to the dysregulated immune response resulting in a variety of inflammatory conditions including sepsis syndrome. Understanding of structural requirements for Lipid A endotoxicity would ensure the development of effective anti-inflammatory medications. Herein, we report on design, synthesis, and biological activities of a series of conformationally confined Lipid A mimetics based on β,α-trehalose-type scaffold. Replacement of the flexible three-bond β(1→6) linkage in diglucosamine backbone of Lipid A by a two-bond β,α(1↔1) glycosidic linkage afforded novel potent TLR4 antagonists. Synthetic tetraacylated bisphosphorylated Lipid A mimetics based on a β-GlcN(1↔1)α-GlcN scaffold selectively block the LPS binding site on both human and murine MD-2 and completely abolish lipopolysaccharide-induced pro-inflammatory signaling, thereby serving as antisepsis drug candidates. In contrast to their natural counterpart lipid IVa, conformationally constrained Lipid A mimetics do not activate mouse TLR4. The structural basis for high antagonistic activity of novel Lipid A mimetics was confirmed by molecular dynamics simulation. Our findings suggest that besides the chemical structure, also the three-dimensional arrangement of the diglucosamine backbone of MD-2-bound Lipid A determines endotoxic effects on TLR4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomimetics*
  • Crystallography, X-Ray
  • Dose-Response Relationship, Drug
  • Escherichia coli / chemistry
  • HEK293 Cells
  • Humans
  • Interleukin-6 / antagonists & inhibitors
  • Interleukin-6 / metabolism
  • Lipid A / chemistry*
  • Lipopolysaccharides / immunology
  • Male
  • Mice
  • Models, Biological*
  • Molecular Conformation
  • Peptides / antagonists & inhibitors
  • Peptides / chemistry*
  • Protein Binding
  • Signal Transduction
  • Toll-Like Receptor 4 / antagonists & inhibitors
  • Toll-Like Receptor 4 / chemistry*


  • Interleukin-6
  • Lipid A
  • Lipopolysaccharides
  • MD-2 mimetic peptide
  • Peptides
  • TLR4 protein, human
  • Toll-Like Receptor 4