Allosteric Model of Maraviroc Binding to CC Chemokine Receptor 5 (CCR5)

Abstract

Maraviroc is a nonpeptidic small molecule human immunodeficiency virus type 1 (HIV-1) entry inhibitor that has just entered the therapeutic arsenal for the treatment of patients. We recently demonstrated that maraviroc binding to the HIV-1 coreceptor, CC chemokine receptor 5 (CCR5), prevents it from binding the chemokine CCL3 and the viral envelope glycoprotein gp120 by an allosteric mechanism. However, incomplete knowledge of ligand-binding sites and the lack of CCR5 crystal structures have hampered an in-depth molecular understanding of how the inhibitor works. Here, we addressed these issues by combining site-directed mutagenesis (SDM) with homology modeling and docking. Six crystal structures of G-protein-coupled receptors were compared for their suitability for CCR5 modeling. All CCR5 models had equally good geometry, but that built from the recently reported dimeric structure of the other HIV-1 coreceptor CXCR4 bound to the peptide CVX15 (Protein Data Bank code 3OE0) best agreed with the SDM data and discriminated CCR5 from non-CCR5 binders in a virtual screening approach. SDM and automated docking predicted that maraviroc inserts deeply in CCR5 transmembrane cavity where it can occupy three different binding sites, whereas CCL3 and gp120 lie on distinct yet overlapped regions of the CCR5 extracellular loop 2. Data suggesting that the transmembrane cavity remains accessible for maraviroc in CCL3-bound and gp120-bound CCR5 help explain our previous observation that the inhibitor enhances dissociation of preformed ligand-CCR5 complexes. Finally, we identified residues in the predicted CCR5 dimer interface that are mandatory for gp120 binding, suggesting that receptor dimerization might represent a target for new CCR5 entry inhibitors.

CCR5 Antagonist TD-0680 Uses a Novel Mechanism for Enhanced Potency against HIV-1 Entry, Cell-mediated Infection, and a Resistant Variant

“…Consistent with mutagenesis analysis, TD-0232 and Maraviroc interacted with key residues such as Trp-86, Tyr-108, Ile-198, Tyr-251, and Glu-283 (Fig. 5, B, C, and E) (21,34,35). As for TD-0680, Tyr-108, Phe-112, Ile-198, Trp-248, and Tyr-251, which locate in the deep TM pocket, provided a hydrophobic environment to the binding of TD-0680.…”

“…Structural Modeling Uncovered Unique Binding Mechanism Employed by TD-0680-A CCR5 model was built based on sequence homology of a recently determined CXCR4 crystal structure (35,38). TAK-779, Maraviroc, TD-0232, and TD-0680 were docked using this model, and the lowest energy/ highest cluster conformations of each compound were subsequently analyzed.…”

Chemokine Receptors as Therapeutic Targets in HIV Infection

“…The finding that the TM cavity remains accessible for MVC in CCL3-bound and gp120-bound CCR5 [113], provides an explanation for the enhancement by TAK779 and MVC of the dissociation of preformed ligand-CCR5 complexes with an efficiency that correlates with their ability to act as inverse agonists [112]. The identification of residues mandatory for gp120 binding in the predicted CCR5 dimer interface suggests that receptor dimerization might represent a target for new CCR5 entry inhibitors [113].…”

“…MVC is predicted to insert deeply in the CCR5 TM cavity where it can occupy three different binding sites, whereas CCL3 and gp120 lie on distinct, yet overlapped regions of the CCR5 ECL2 [113]. TAK779 and MVC were found to be full and weak inverse agonists for CCR5, respectively, indicating that they stabilize distinct CCR5 conformations with impaired abilities to activate G-proteins [112].…”

Protein-protein Interactions: Network Analysis and Applications in Drug Discovery

“…Although small molecules can be developed that are cell permeable and should therefore be able to target PPIs inside the cell, most FDA-approved small molecule PPI inhibitors inhibit the interaction of extracellular proteins. Examples are the anti-HIV drug maraviroc that allosterically inhibits the interaction between the viral gp120 protein and the human CCR5 receptor [14]; tirofiban that antagonizes fibrinogen binding to the glycoprotein IIb/IIIa receptor and is used as a platelet aggregation inhibitor; and degarelix, an inhibitor of the interaction between gonadotropin-releasing hormone and its receptor for the treatment of prostate cancer [11]. Since quite some intracellular small molecule PPI inhibitors are currently being clinically evaluated, predominantly in the oncology field, and more should soon enter phase I trials based on their thorough pre-clinical validation, it is likely just a matter of time before some of them will gain FDA approval.…”