Molecular insights into intrinsic transducer-coupling bias in the CXCR4-CXCR7 system

Chemokine receptors constitute an important subfamily of G protein-coupled receptors (GPCRs), and they are critically involved in a broad range of immune response mechanisms. Ligand promiscuity among these receptors makes them an interesting target to explore multiple aspects of biased agonism. Here, we comprehensively characterize two chemokine receptors namely, CXCR4 and CXCR7, in terms of their transducer-coupling and downstream signaling upon their stimulation by a common chemokine agonist, CXCL12, and a small molecule agonist, VUF11207. We observe that CXCR7 lacks G-protein-coupling while maintaining robust & beta;arr recruitment with a major contribution of GRK5/6. On the other hand, CXCR4 displays robust G-protein activation as expected but exhibits significantly reduced & beta;arr-coupling compared to CXCR7. These two receptors induce distinct & beta;arr conformations even when activated by the same agonist, and CXCR7, unlike CXCR4, fails to activate ERK1/2 MAP kinase. We also identify a key contribution of a single phosphorylation site in CXCR7 for & beta;arr recruitment and endosomal localization. Our study provides molecular insights into intrinsic-bias encoded in the CXCR4-CXCR7 system with broad implications for drug discovery. Chemokine receptors are G protein-coupled receptors (GPCRs) involved in immune responses and characterized by ligand promiscuity Here, the authors characterize signaling through chemokine receptors CXCR4 and CXCR7, with insights into intrinsic-bias encoded in the CXCR4-CXCR7 system.

Automated summary

Chemokine receptors are G protein-coupled receptors (GPCRs) involved in immune responses and characterized by ligand promiscuity. Here, the authors characterize signaling through chemokine receptors CXCR4 and CXCR7, with insights into intrinsic-bias encoded in the CXCR4-CXCR7 system.