HIV-1 exploits CCR5 conformational heterogeneity to escape inhibition by chemokines

Abstract

CC chemokine receptor 5 (CCR5) is a receptor for chemokines and the coreceptor for R5 HIV-1 entry into CD4(+) T lymphocytes. Chemokines exert anti-HIV-1 activity in vitro, both by displacing the viral envelope glycoprotein gp120 from binding to CCR5 and by promoting CCR5 endocytosis, suggesting that they play a protective role in HIV infection. However, we showed here that different CCR5 conformations at the cell surface are differentially engaged by chemokines and gp120, making chemokines weaker inhibitors of HIV infection than would be expected from their binding affinity constants for CCR5. These distinct CCR5 conformations rely on CCR5 coupling to nucleotide-free G proteins ((NF)G proteins). Whereas native CCR5 chemokines bind with subnanomolar affinity to (NF)G protein-coupled CCR5, gp120/HIV-1 does not discriminate between (NF)G protein-coupled and uncoupled CCR5. Interestingly, the antiviral activity of chemokines is G protein independent, suggesting that "low-chemokine affinity" (NF)G protein-uncoupled conformations of CCR5 represent a portal for viral entry. Furthermore, chemokines are weak inducers of CCR5 endocytosis, as is revealed by EC50 values for chemokine-mediated endocytosis reflecting their low-affinity constant value for (NF)G protein-uncoupled CCR5. Abolishing CCR5 interaction with (NF)G proteins eliminates high-affinity binding of CCR5 chemokines but preserves receptor endocytosis, indicating that chemokines preferentially endocytose low-affinity receptors. Finally, we evidenced that chemokine analogs achieve highly potent HIV-1 inhibition due to high-affinity interactions with internalizing and/or gp120-binding receptors. These data are consistent with HIV-1 evading chemokine inhibition by exploiting CCR5 conformational heterogeneity, shed light into the inhibitory mechanisms of anti-HIV-1 chemokine analogs, and provide insights for the development of unique anti-HIV molecules

Cocirculation of Two env Molecular Variants, of Possible Recombinant Origin, in Gorilla and Chimpanzee Simian Foamy Virus Strains from Central Africa

“…Alternatively, the SFV receptor may be expressed in different conformations at the cell surface, allowing two modes of engagement by the two Env variants. Indeed, such conformational heterogeneity was described for the CCR5 molecule and its interaction with the envelope of HIV and chemokines (67).…”

P2X1 Receptor Antagonists Inhibit HIV-1 Fusion by Blocking Virus-Coreceptor Interactions

“…The incomplete inhibition of CXCR4 signaling in CEM-A cells by NF279 may reflect a greater heterogeneity of this coreceptor due to posttranslational modifications that are different from those in TZM-bl cells. The existence of distinct pools of CCR5 and CXCR4 on the cell surface was previously documented (52)(53)(54)(55)(56)(57). In addition, it appears that NF279 can promiscuously interfere with the function of other chemokine receptors, as exemplified by its ability to block calcium influx elicited by the CXCR3/CXCR7 agonist I-TAC in T cells.…”

Combination of the CCL5-Derived Peptide R4.0 with Different HIV-1 Blockers Reveals Wide Target Compatibility and Synergic Cobinding to CCR5

“…Considering the large surface of interaction between CCR5 and CCL5 (45), the conformational flexibility of the receptor, the relatively small targeting site by MVC, and the occupancy of only a portion of the CCL5 interaction area by R4.0, a scenario may be conceived in which most CCR5 molecules on the surface of the target cell are engaged by one or more of these ligands. A deeper explanation is inspired by a recent report investigating the CCR5 conformational preferences exerted by natural CCR5 ligands, 5p12-RANTES, and HIV-1 (46). While the virus does not discriminate between CCR5 conformations, CCR5-binding chemokines, including CCL5, have high affinity for nucleotide-free G protein-bound CCR5 and low affinity for CCR5 uncoupled from nucleotide-free G protein (46).…”