title: Development of αGlcN(1↔1)αMan-based lipid A mimetics as a novel class of potent Toll-like receptor 4 agonists.
abstract: The endotoxic portion of lipopolysaccharide (LPS), a glycophospholipid Lipid A, initiates the activation of the Toll-like Receptor 4 (TLR4)-myeloid differentiation factor 2 (MD-2) complex, which results in pro-inflammatory immune signaling. To unveil the structural requirements for TLR4·MD-2-specific ligands, we have developed conformationally restricted Lipid A mimetics wherein the flexible βGlcN(1→6)GlcN backbone of Lipid A is exchanged for a rigid trehalose-like αGlcN(1↔1)αMan scaffold resembling the molecular shape of TLR4·MD-2-bound E. coli Lipid A disclosed in the X-ray structure. A convergent synthetic route toward orthogonally protected αGlcN(1↔1)αMan disaccharide has been elaborated. The α,α-(1↔1) linkage was attained by the glycosylation of 2-N-carbamate-protected α-GlcN-lactol with N-phenyl-trifluoroacetimidate of 2-O-methylated mannose. Regioselective acylation with (R)-3-acyloxyacyl fatty acids and successive phosphorylation followed by global deprotection afforded bis- and monophosphorylated hexaacylated Lipid A mimetics. αGlcN(1↔1)αMan-based Lipid A mimetics (α,α-GM-LAM) induced potent activation of NF-κB signaling in hTLR4/hMD-2/CD14-transfected HEK293 cells and robust LPS-like cytokines expression in macrophages and dendritic cells. Thus, restricting the conformational flexibility of Lipid A by fixing the molecular shape of its carbohydrate backbone in the "agonistic" conformation attained by a rigid αGlcN(1↔1)αMan scaffold represents an efficient approach toward powerful and adjustable TLR4 activation.
authors.affiliation: Department of Chemistry, University of Natural Resources and Life Sciences , Muthgasse 18, A-1190 Vienna, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Adanitsch
authors.forename: Simon
authors.initials: S
authors.lastname: Ittig
authors.forename: Johannes
authors.initials: J
authors.lastname: Stöckl
authors.forename: Alja
authors.initials: A
authors.lastname: Oblak
authors.forename: Mira
authors.initials: M
authors.lastname: Haegman
authors.forename: Roman
authors.initials: R
authors.lastname: Jerala
authors.forename: Rudi
authors.initials: R
authors.lastname: Beyaert
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
authors.forename: Alla
authors.initials: A
authors.lastname: Zamyatina
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000138:chemical synthesis* / Q000494:pharmacology; D016207:Cytokines / Q000096:biosynthesis; D003713:Dendritic Cells / Q000276:immunology; D015195:Drug Design; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D008050:Lipid A / Q000031:analogs & derivatives*; D051379:Mice; D051197:Toll-Like Receptor 4 / Q000819:agonists*; D014199:Trehalose / Q000138:chemical synthesis* / Q000494:pharmacology
chemical_list: D016207:Cytokines; D008050:Lipid A; D051197:Toll-Like Receptor 4; D014199:Trehalose