Non-peptide ligand binding to the formyl peptide receptor FPR2--A comparison to peptide ligand binding modes

Ligands of the FPR2 receptor initiate many signaling pathways including activation of phospholipase C, protein kinase C, the mitogen-activated protein kinase, and phosphatidylinositol 3-kinase/protein kinase B pathway. The possible actions include also calcium flux, superoxide generation, as well as migration and proliferation of monocytes. FPR2 activation may induce a pro- and anti-inflammatory effect depending on the ligand type. It is also found that this receptor is involved in tumor growth. Most of currently known FPR2 ligands are agonists since they were designed based on N-formyl peptides, which are natural agonists of formyl receptors. Since the non-peptide drugs are indispensable for effective treatment strategies, we performed a docking study of such ligands employing a generated dual template homology model of the FPR2 receptor. The study revealed different binding modes of particular classes of these drugs. Based on the obtained docking poses we proposed a detailed location of three hydrophobic pockets in orthosteric binding site of FPR2. Our model emphasizes the importance of aromatic stacking, especially with regard to residues His102(3.29) and Phe257(6.51), for binding of FPR2 ligands. We also identified other residues important for non-peptide ligand binding in the binding site of FPR2.