The immune system protects us from pathogenic agents that pose a threat to our body. Receptors that recognize molecular structures characteristic of various infectious agents are key to the activation of the immune response. Among them are nucleotide-binding oligomerization domain-containing proteins 2 (NOD2), which are primarily found in immune cells and trigger an inflammatory response upon ligand binding. The smallest structural unit of bacterial peptidoglycan that activates the NOD2 is muramyl dipeptide. Upon binding, mechanisms of innate immunity and, indirectly, adaptive immunity are activated, which is why synthetic NOD2 agonists hold great therapeutic potential. Besides their role as adjuvants in vaccines, they could also be used in cancer therapy and in the treatment of certain infectious diseases. Recently, they have also shown promise as potential therapeutic agents in the treatment of neurodegenerative diseases.
As part of this Master’s thesis, we aimed to improve the agonistic activity of a desmuramylpeptide lead compound on the NOD2 receptor. We synthesized 12 different analogues of a trans-feruloyl derivative of the tripeptide hPhe-L-Val-D-Glu, in which the amino acid homophenylalanine was replaced with its structural analogues. The first set of modifications involved introducing various functional groups onto the aromatic ring. Next, the aromatic ring was replaced with a cyclohexyl group, and finally, we prepared analogues containing an additional methylene group. The agonistic activity of the synthesized compounds on the NOD2 receptor was evaluated using a HEK-Blue hNOD2 cell-based assay.
The results confirmed that compounds containing the D-configured amino acid were more potent agonists than those with the L-configuration. The structures of four synthesized compounds that exhibited EC50 values in the picomolar concentration range suggest that hydrophobic interactions of the homophenylalanine analogues in the receptor's binding pocket are key for agonistic activity. The most potent compound in the assay contained a homophenylalanine analogue with an additional methylene group in the side chain (EC50 = 310 pM). Our results provided further insight into the structure–activity relationship of NOD2 agonists. The synthesized compounds represent a promising starting point for further evaluation, while the SAR findings will serve as valuable guidance for future optimization of these compounds.
|
