Structural Basis for the Interaction of CCR5 with a Small Molecule, Functionally Selective CCR5 Agonist

Abstract

The chemokine receptor CCR5 is an attractive target for HIV-1 drug development, as individuals whose cells lack surface CCR5 expression are highly resistant to HIV-1 infection. CCR5 ligands, such as CCL5/RANTES, effectively inhibit HIV-1 infection by competing for binding opportunities to the CCR5 and inducing its internalization. However, the inherent proinflammatory activity of the chemotactic response of CCR5 ligands has limited their clinical use. In this study, we found that a novel small molecule, functionally selective CCR5 agonist, 2,2-dichloro-1-(triphenylphosphonio)vinyl formamide perchlorate (YM-370749), down-modulates CCR5 from the cell surface without inducing a chemotactic response and inhibits HIV-1 replication. In molecular docking studies of YM-370749 and a three-dimensional model of CCR5 based on the rhodopsin crystal structure as well as binding and functional studies using various CCR5 mutants, the amino acid residues necessary for interaction with YM-370749 were marked. These results provide a structural basis for understanding the activation mechanism of CCR5 and for designing functionally selective agonists as a novel class of anti-HIV-1 agents.

Agonist-Induced Internalization of CC Chemokine Receptor 5 as a Mechanism to Inhibit HIV Replication

“…In this approach, the ligand-receptor interaction of the CCR5 agonist would provide an allosteric blockade of the gp12-CCR5 interaction to prevent viral entry (similarly to the CCR5 antagonists), and in addition, agonism of CCR5 causes receptor internalization, thereby eliciting a sustained ablation of the entry gate for HIV. The notion of using a small-molecule CCR5 agonist in this manner has been reported previously (Saita et al, 2006); however, we were unable to reproduce these results with the reference ligand (YM-370349). Nonetheless, we report here the discovery of a novel CCR5 smallmolecule agonist with a high anti-HIV potency profile in vitro.…”

“…1C). The synthetic CCR5 agonist 2,2-dichloro-1-(triphenylphosphonio)vinyl formamide perchlorate (YM-370749) (Saita et al, 2006) was tested as a reference ligand and was determined to be inactive in both assays. In contrast, all of the other compounds competitively and reversibly displaced 125 I-MIP-1␤ binding with ESN-196 (K i ϭ 0.09 nM), demonstrating Ͼ50-fold higher potency than the precursor compounds A and B (K i ϭ 21.2 and 5.6 nM, respectively) and the reference antagonist, maraviroc (K i ϭ 0.93 nM).…”

“…This modified chemokine acts as an agonist of CCR5 and has a particularly high capacity to induce CCR5 internalization (Sabbe et al, 2001). Several relevant precedents in this area include the work on CCR5-internalizing analogs of RANTES for topical use (Gaertner et al, 2008) as well as reports on small-molecule CCR5 agonists by a few groups (Saita et al, 2006;Kellenberger et al, 2007). In addition to the latter cases, the use of agonists to elicit receptor internalization and thereby achieve the end point of functional antagonism also finds precedence in other projects, such as the work reported on the sphingosine 1-phosphate receptor 1, where the immunomodulating effect of the small-molecule agonist has been reported to result from the down-regulation of this receptor on the surface of T lymphocytes (Zemann et al, 2006;Bolli et al, 2010).…”

Elucidation of CXCR7-Mediated Signaling Events and Inhibition of CXCR4-Mediated Tumor Cell Transendothelial Migration by CXCR7 Ligands

“…Recently, novel small molecule agonists for CCR3, CCR5, CCR8, and CXCR3 have been reported (18 -21). One of these, the agonist for CCR5, triggered ␤-arrestin2 recruitment (18), similar to the effect of CCX771 on CXCR7. Ali et al (22) argue that nonchemotactic chemokine receptor agonists may be useful in interfering with leukocyte recruitment via homologous and heterologous receptor desensitization.…”

“…It is uncommon to discover small molecule ligands that activate GPCRs whose endogenous ligands are proteins, particularly chemokines (18). We were therefore intrigued by the ability of CCX771 to induce the association of CXCR7 with ␤-arrestin2.…”