Structural and Molecular Interactions of CCR5 Inhibitors with CCR5

Abstract

We have characterized the structural and molecular interactions of CC-chemokine receptor 5 (CCR5) with three CCR5 inhibitors active against R5 human immunodeficiency virus type 1 (HIV-1) including the potent in vitro and in vivo CCR5 inhibitor aplaviroc (AVC). The data obtained with saturation binding assays and structural analyses delineated the key interactions responsible for the binding of CCR5 inhibitors with CCR5 and illustrated that their binding site is located in a predominantly lipophilic pocket in the interface of extracellular loops and within the upper transmembrane (TM) domain of CCR5. Mutations in the CCR5 binding sites of AVC decreased gp120 binding to CCR5 and the susceptibility to HIV-1 infection, although mutations in TM4 and TM5 that also decreased gp120 binding and HIV-1 infectivity had less effects on the binding of CC-chemokines, suggesting that CCR5 inhibition targeting appropriate regions might render the inhibition highly HIV-1-specific while preserving the CC chemokine-CCR5 interactions. The present data delineating residue by residue interactions of CCR5 with CCR5 inhibitors should not only help design more potent and more HIV-1-specific CCR5 inhibitors, but also give new insights into the dynamics of CC-chemokine-CCR5 interactions and the mechanisms of CCR5 involvement in the process of cellular entry of HIV-1.Highly active antiretroviral therapy has brought about a major impact on the acquired immunodeficiency syndrome (AIDS) epidemics in industrially advanced nations (1, 2), however, eradication of HIV-1 2 appears to be currently impossible mainly because of the viral reservoirs remaining in blood and infected tissues (3). Successful antiviral drugs, in theory, exert their virus-specific effects by interacting with viral components such as viral genes or their transcripts without disturbing cellular metabolisms or functions (2). However, at present, no antiretroviral drugs or agents have been demonstrated to be completely specific for HIV-1 and devoid of toxicity or side effects in the therapy of AIDS (4). Limitations of antiviral therapy of AIDS are exacerbated by complicated regimens, emergence of drug-resistant HIV-1 variants (1), and a number of inherent adverse effects (5).Thus, identification of new antiretroviral drugs that have unique mechanisms of action and produce no or least minimal side effects remains an important therapeutic objective (2, 4). CCR5 is a member of the G protein-coupled, seven-transmembrane segment receptors, which comprise the largest superfamily of proteins in the body (6). In 1996, it was revealed that CCR5 serves as one of the two essential coreceptors for HIV-1 entry to human CD4 ϩ cells, thereby serving as an attractive target for possible intervention of HIV-1 infection (7-10). Aplaviroc (AVC; AK602/ONO4128/873140; Fig. 1), a novel spirodiketopiperazine derivative, represents a CCR5 inhibitor that specifically binds to human CCR5 with a high affinity, greatly blocks HIV-1-gp120/ CCR5 binding, and exerts potent activity against a wide spectrum of ...

HIV-1 Resistance to CCR5 Antagonists Associated with Highly Efficient Use of CCR5 and Altered Tropism on Primary CD4 + T Cells

“…This resistance pathway often, but not always, results in a virus that is resistant to multiple CCR5 antagonists (22,33,39,53,56). The CCR5 antagonists that have been used clinically all seem to bind to a hydrophobic region in the transmembrane helices of CCR5 and induce conformational alterations in the extracellular domains of the coreceptor that inhibit recognition by gp120 (13,31,32,46,52). These conformational alterations are similar though not identical as judged by the ability of these compounds to affect the binding of various conformation-dependent monoclonal antibodies to CCR5.…”

“…Interactions between gp120 and CCR5 occur in at least two distinct areas: (i) the bridging sheet and the stem of the V3 loop interact with sulfated tyrosine residues in the NЈ terminus of CCR5, and (ii) the crown of the V3 loop is thought to engage the extracellular loops (ECLs), particularly ECL2, of CCR5 (10-12, 14, 18, 28). Small-molecule CCR5 antagonists bind to a hydrophobic pocket in the transmembrane helices of CCR5 and exert their effects on HIV by altering the position of the ECLs, making them allosteric inhibitors of HIV infection (13,31,32,46,52). The conformational changes in CCR5 that are induced by CCR5 antagonists vary to some degree with different drugs, as evidenced by differential binding of antibodies and chemokines to various drug-bound forms of CCR5 (47,54).…”

Binding modes of CCR5-targetting HIV entry inhibitors: Partial and full antagonists

“…Similar to aplaviroc, SCH-C formed a hydrogen bond with Glu283 through its oxime-hydroxyl group, which could explain the dramatic loss of binding affinity when Glu283 was mutated to alanine. 16 The other terminal oxygen atom of Glu283 formed two intramolecular hydrogen bonds to the hydroxyl groups of Thr177 and Tyr108, respectively. The oxime-piperidine ring of the inhibitor fitted into a hydrophobic pocket created by the side chains of Glu172 and Arg274 that formed a salt link between each other.…”

HIV Type 1 from a Patient with Baseline Resistance to CCR5 Antagonists Uses Drug-Bound Receptor for Entry

“…[13][14][15][16] The binding site for most, if not all, CCR5 antagonists appears to be a lipophilic pocket near the interface of the extracellular loops (ECLs) and transmembrane helices of CCR5. 17,18 CCR5 antagonists are believed to exert their antiviral effects by altering the conformation of CCR5 rather than by directly competing with the HIV envelope glycoprotein (Env) for binding to the coreceptor, making them allosteric inhibitors. 19 With the recent approval of maraviroc for the treatment of HIV infection, it will be important to determine viral and host factors that influence the efficacy of these agents.…”