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

Abstract

The chemokine G protein-coupled receptor CC chemokine receptor 5 (CCR5) is used as an entry gate by CCR5-tropic and dual-or CCR5/CXC chemokine receptor 4-tropic strains of HIV to enter the human host cells. Thus, CCR5 antagonists (i.e., maraviroc) have been proven to be clinically effective by preventing the interaction between viral glycoprotein 120 and CCR5 and thus impeding viral entry into host cells. However, the emergence of HIV strains resistant to CCR5 antagonists has been reported in vitro and in vivo, where the virus has adapted to enter the cells via antagonist-bound CCR5. An alternative strategy that should obviate this mode of viral resistance would entail the ablation of the CCR5 portal for HIV entry from the cell surface through agonist-induced receptor internalization. Although this protective effect has been demonstrated clearly with natural CCR5 ligands, the chemoattractant properties of these chemokines have precluded them from further consideration in terms of drug development. Thus, we sought to explore the possibility of developing novel small molecules and selective CCR5 agonists devoid of eliciting chemotaxis. Indeed, the CCR5 agonists described herein were found to induce profound downmodulation of CCR5 (and not CXC chemokine receptor 4) from the cell surface and its sustained sequestration in the intracellular compartment without inducing chemotaxis in vitro. The bioactivity profile of these novel CCR5 agonists is exemplified by the compound (R)-2-(4-cyanophenyl)-N-(1-(1-(N,1-diphenylmethylsulfonamido)propan-2-yl)piperidin-4-yl)acetamide ) that potently inhibits HIV-1 infection in human peripheral blood mononuclear cells and macrophages in vitro with potencies comparable to that of maraviroc and moreover demonstrates full activity against a maraviroc-resistant HIV-1 RU570 strain.

Biased Signaling at Chemokine Receptors

“…We also showed that the chemokines tested in this study activated G proteins with potencies that generally match those detected for ␤-arrestin recruitment and other assays, but with subtle changes in the rank order according to assay. Thus, the behavior of chemokines contrast to the situation encountered in other studies with some synthetic small molecules that show agonism in one assay but antagonism in another (30,31). Collectively, our results suggest the existence of a moderate signaling bias between chemokines acting on the same receptor.…”

Biased and Constitutive Signaling in the CC-chemokine Receptor CCR5 by Manipulating the Interface between Transmembrane Helices 6 and 7

“…Such a biased drug would cause receptor internalization, thereby preventing virus interaction with CCR5 and a lack of potential side effects after unwanted cellular signaling. Importantly, these properties were recently presented in ESN-196, a novel small-molecule CCR5-targeting ligand that induced CCR5 sequestration without promoting chemotaxis (47). Theoretically, targeting human components involved in the HIV infection cycle instead of the viral proteins would decrease the risk of resistance (48,49).…”

Partial Agonist and Biased Signaling Properties of the Synthetic Enantiomers J113863/UCB35625 at Chemokine Receptors CCR2 and CCR5

“…The CCR5 response may also be biased with synthetic small molecules. For instance, YM-370749 and ESN-196 promote strong calcium mobilization and receptor internalization but not cell migration (20,21). However, the signaling pathways activated by synthetic small molecules at chemokine receptors remains often unknown.…”