Structure–Activity Relationship in Monosaccharide-Based Toll-Like Receptor 4 (TLR4) Antagonists

Abstract

The structure-activity relationship was investigated in a series of synthetic TLR4 antagonists formed by a glucosamine core linked to two phosphate esters and two linear carbon chains. Molecular modeling showed that the compounds with 10, 12, and 14 carbons chains are associated with higher stabilization of the MD-2/TLR4 antagonist conformation than in the case of the C16 variant. Binding experiments with human MD-2 showed that the C12 and C14 variants have higher affinity than C10, while the C16 variant did not interact with the protein. The molecules, with the exception of the C16 variant, inhibited the LPS-stimulated TLR4 signal in human and murine cells, and the antagonist potency mirrored the MD-2 affinity calculated from in vitro binding experiments. Fourier-transform infrared, nuclear magnetic resonance, and small angle X-ray scattering measurements suggested that the aggregation state in aqueous solution depends on fatty acid chain lengths and that this property can influence TLR4 activity in this series of compounds.

Toll-like Receptor 4–Induced Glycolytic Burst in Human Monocyte-Derived Dendritic Cells Results from p38-Dependent Stabilization of HIF-1α and Increased Hexokinase II Expression

“…1), suggesting that FP7 blocked both endosomal TRIF-dependent and surface MyD88-dependent TLR4 signaling (37). Because FP7 competes with LPS for binding to the TLR4 MD-2 subunit (32,38) and prevents ligand-mediated TLR4 internalization (F.A. Facchini, D. Di Fusco, S. Barresi, A. Minotti, F. Granucci, G. Monteleone, F. Peri, and I. Monteleone, manuscript in preparation), these results suggest that FP7 may not directly inhibit endosomal TLR4 signaling but rather inhibits upstream activation of TLR4 receptor by LPS.…”

Bradyrhizobium Lipid A: Immunological Properties and Molecular Basis of Its Binding to the Myeloid Differentiation Protein-2/Toll-Like Receptor 4 Complex

“…In a second approach, docking calculations of HOLA were performed into the MD-2/TLR4 model in the antagonist conformation reported by us somewhere else ( 50 ). Interestingly, when compared with the structure of the MD-2/TLR4 complex in the agonist conformation (PDB ID 3FXI), among the non-bonded interactions between the two proteins, a loop of TLR4, composed of amino acids 263–266, protrudes into a MD-2 channel (Figure S2 in Supplementary Material), located approximately between Asp161 and Tyr118.…”

Homeostatic and pathogenic roles of GM 3 ganglioside molecular species in TLR 4 signaling in obesity

“…In particular, molecular features of LCFA-GM3 and unsaturated VLCFA-GM3 resemble those of eritoran: (i) short aliphatic-chain length (C10) in comparison with agonistic lipid A species (C14) and (ii) desaturation (C18:1, x-7) making a 180degree turn of the acyl chain in the hydrophobic pocket of MD-2 (Kim et al, 2007). Mimetic compounds based on lipid A/IVa precursors (diacyl monosaccharide species), carrying less number of fatty acids, show antagonistic effect (Facchini et al, 2018). Thus, less fatty-acid number, shorter acyl-chain length, and desaturation may cooperatively contribute to antagonistic activity by affecting interaction mode.…”