Synthesis, modeling and functional activity of substituted styrene-amides as small-molecule CXCR7 agonists

Allosteric peptide regulators of chemokine receptors CXCR4 and CXCR7

The chemokine CXCL12 and its shared seven-transmembrane receptors CXCR4 and CXCR7 regulate diseases including cancer, atherosclerosis, autoimmunity, and HIV infection, making these molecules promising drug targets. These molecules also control key processes in normal development and physiology, suggesting the need to selectively modulate CXCR4 and/or CXCR7 functions and signaling to reduce potential complications of long-term therapy. We previously identified two peptides that functioned as allosteric agonists driving CXCR4-dependent chemotaxis, providing key structural information to design a small number of additional peptides to investigate determinants of CXCL12 interactions and signaling through CXCR4 and CXCR7. In the current study, we show that the previously identified peptides only minimally activated CXCR4 signaling through the cytosolic adapter protein β-arrestin 2 and do not initiate signaling to ERK1/2. By comparison, peptides with diverse N-terminal amino acid sequences effectively activated CXCR7 signaling to β-arrestin 2. One peptide, designated as GSLW based on its N-terminal amino acids, activated CXCR7 signaling and potentiated CXCL12-CXCR7 signaling without blocking the scavenger function of CXCR7 to internalize CXCL12. These results advance our understanding of CXCR7 ligand recognition and signaling, and provide structural information to target allosteric binding sites on this receptor as chemical probes and potential therapeutic agents.

Optimized method of G-protein-coupled receptor homology modeling: its application to the discovery of novel CXCR7 ligands

Homology modeling of G-protein-coupled seven-transmembrane receptors (GPCRs) remains a challenge despite the increasing number of released GPCR crystal structures. This challenge can be attributed to the low sequence identity and structural diversity of the ligand-binding pocket of GPCRs. We have developed an optimized GPCR structure modeling method based on multiple GPCR crystal structures. This method was designed to be applicable to distantly related receptors of known structural templates. CXC chemokine receptor (CXCR7) is a potential drug target for cancer chemotherapy. Homology modeling, docking, and virtual screening for CXCR7 were carried out using our method. The predicted docking poses of the known antagonists were different from the crystal structure of human CXCR4 with the small-molecule antagonist IT1t. Furthermore, 21 novel CXCR7 ligands with IC50 values of 1.29-11.4 μM with various scaffolds were identified by structure-based virtual screening.