Structure-Activity Relationships in Nucleotide Oligomerization Domain 1 (Nod1) Agonistic γ-Glutamyldiaminopimelic Acid Derivatives

N-Acyl-gamma-glutamyldiaminopimelic acid is a prototype ligand for Nod1. We report a detailed SAR of C-12-gamma-D-Glu-DAP. Analogues with glutaric or gamma-aminobutyric acid replacing the glutamic acid show greatly attenuated Nod1-agonistic activity. Substitution of the meso-diaminopimelic (DAP) acid component with monoaminopirnelic acid, L- or D-lysine, or cadaverine also results in reduced activity. The free amine on DAP is crucial. However, the N-acyl group on the D-glutamyl residue can be substituted with N-alkyl groups with full preservation of activity. The free carboxylates on the DAP and Glu components can also be esterified, resulting in more lipophilic but active analogues. Transcriptomal profiling showed a dominant up-regulation of IL-19, IL-20, IL-22, and IL-24, which may explain the pronounced Th2-polarizing activity of these compounds and also implicate cell signaling mediated by TREM-1. These results may explain the hitherto unknown mechanism of synergy between Nod1 and TLR agonists and are likely to be useful in designing vaccine adjuvants.