Structure of CC Chemokine Receptor 2 with Orthosteric and Allosteric Antagonists

Summary

CC chemokine receptor 2 (CCR2) is one of 19 members of the chemokine receptor subfamily of human Class A G protein-coupled receptors (GPCRs). CCR2 is expressed on monocytes, immature dendritic cells and T cell subpopulations, and mediates their migration towards endogenous CC chemokine ligands such as CCL2 ¹ . CCR2 and its ligands are implicated in numerous inflammatory and neurodegenerative diseases ² including atherosclerosis, multiple sclerosis, asthma, neuropathic pain, and diabetic nephropathy, as well as cancer ³ . These disease associations have motivated numerous preclinical studies and clinical trials ⁴ (see ClinicalTrials.gov) in search of therapies that target the CCR2:chemokine axis. To aid drug discovery efforts ⁵ , we solved a structure of CCR2 in a ternary complex with an orthosteric (BMS-681 ⁶ ) and allosteric (CCR2-RA-[ R] ⁷ ) antagonist. BMS-681 inhibits chemokine binding by occupying the orthosteric pocket of the receptor in a previously unseen binding mode. CCR2-RA-[ R] binds in a novel, highly druggable pocket that is the most intracellular allosteric site observed in Class A GPCRs to date; this site spatially overlaps the G protein-binding site in homologous receptors. CCR2-RA-[ R] inhibits CCR2 non-competitively by blocking activation-associated conformational changes and formation of the G protein-binding interface. The conformational signature of the conserved microswitch residues observed in double-antagonist-bound CCR2 resembles the most inactive GPCR structures solved to date. Like other protein:protein interactions, receptor:chemokine complexes are considered challenging therapeutic targets for small molecules, and the present structure suggests diverse pocket epitopes that can be exploited to overcome drug design obstacles.