Development of ?GlcN(1?1)?Man-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 ?GlcN(1?6)GlcN backbone of Lipid A is exchanged for a rigid trehalose-like ?GlcN(1?1)?Man 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 ?GlcN(1?1)?Man disaccharide has been elaborated. The ?,?-(1?1) linkage was attained by the glycosylation of 2-N-carbamate-protected ?-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. ?GlcN(1?1)?Man-based Lipid A mimetics (?,?-GM-LAM) induced potent activation of NF-?B 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 ?GlcN(1?1)?Man scaffold represents an efficient approach toward powerful and adjustable TLR4 activation.

SUBMITTER: Adanitsch F 

PROVIDER: S-EPMC4191062 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature