title: Conformationally constrained lipid A mimetics for exploration of structural basis of TLR4/MD-2 activation by lipopolysaccharide.
abstract: 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.
authors: Department of Chemistry, University of Natural Resources and Life Sciences , Muthgasse 18, A-1190 Vienna, Austria.
authors: Daniel
authors: D
authors: Artner
authors: Alja
authors: A
authors: Oblak
authors: Simon
authors: S
authors: Ittig
authors: Jose Antonio
authors: JA
authors: Garate
authors: Simon
authors: S
authors: Horvat
authors: Cécile
authors: C
authors: Arrieumerlou
authors: Andreas
authors: A
authors: Hofinger
authors: Chris
authors: C
authors: Oostenbrink
authors: Roman
authors: R
authors: Jerala
authors: Paul
authors: P
authors: Kosma
authors: Alla
authors: A
authors: Zamyatina
mesh_terms: D000818:Animals; D032701:Biomimetics; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008050:Lipid A / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D051379:Mice; D008954:Models, Biological; D008968:Molecular Conformation; D010455:Peptides / Q000037:antagonists & inhibitors / Q000737:chemistry*; D011485:Protein Binding; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000737:chemistry*; D000093242:Interleukin-6 Inhibitors
chemical_list: D015850:Interleukin-6; D008050:Lipid A; D008070:Lipopolysaccharides; D010455:Peptides; D051197:Toll-Like Receptor 4; D000093242:Interleukin-6 Inhibitors; C554344:MD-2 mimetic peptide; C495345:TLR4 protein, human
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