CCR5 structural plasticity shapes HIV-1 phenotypic properties

Abstract

CCR5 plays immune functions and is the coreceptor for R5 HIV-1 strains. It exists in diverse conformations and oligomerization states. We interrogated the significance of the CCR5 structural diversity on HIV-1 infection. We show that envelope glycoproteins (gp120s) from different HIV-1 strains exhibit divergent binding levels to CCR5 on cell lines and primary cells, but not to CD4 or the CD4i monoclonal antibody E51. This owed to differential binding of the gp120s to different CCR5 populations, which exist in varying quantities at the cell surface and are differentially expressed between different cell types. Some, but not all, of these populations are antigenically distinct conformations of the coreceptor. The different binding levels of gp120s also correspond to differences in their capacity to bind CCR5 dimers/oligomers. Mutating the CCR5 dimerization interface changed conformation of the CCR5 homodimers and modulated differentially the binding of distinct gp120s. Env-pseudotyped viruses also use particular CCR5 conformations for entry, which may differ between different viruses and represent a subset of those binding gp120s. In particular, even if gp120s can bind both CCR5 monomers and oligomers, impairment of CCR5 oligomerization improved viral entry, suggesting that HIV-1 prefers monomers for entry. From a functional standpoint, we illustrate that the nature of the CCR5 molecules to which gp120/HIV-1 binds shapes sensitivity to inhibition by CCR5 ligands and cellular tropism. Differences exist in the CCR5 populations between T-cells and macrophages, and this is associated with differential capacity to bind gp120s and to support viral entry. In macrophages, CCR5 structural plasticity is critical for entry of blood-derived R5 isolates, which, in contrast to prototypical M-tropic strains from brain tissues, cannot benefit from enhanced affinity for CD4. Collectively, our results support a role for CCR5 heterogeneity in diversifying the phenotypic properties of HIV-1 isolates and provide new clues for development of CCR5-targeting drugs.

Mechanisms of HIV-1 evasion to the antiviral activity of chemokine CXCL12 indicate potential links with pathogenesis

“…Late X4 Envs were three-fold less sensitive to inhibition by sCD4 than early Envs (IC 50 = 56 vs 146 nM, P = 0.016). In contrast, early and late R5 Envs exhibited similar sensitivity to sCD4, in the range of that of the JR-CSF strain ( Fig 2D ), which is notoriously resistant to sCD4 [ 32 ]. Of note, the X4 Envs from patient #39 (red symbols in Fig 2C ) were unusually highly sensitive to sCD4.…”

“…Remarkably, SENS gp120s consistently bound more CXCR4 molecules than RES gp120s ( Fig 4A ). Similarly, we recently reported that distinct R5 gp120s can recognize different amounts of CCR5 [ 32 ], because they bind differentially to distinct conformations of the receptor, which exist in different quantities at the cell surface [ 32 ]. Monoclonal antibodies (mAbs) also showed divergent binding levels to CCR5 [ 47 ] or CXCR4 [ 48 , 49 ].…”

Manipulation of Mononuclear Phagocytes by HIV: Implications for Early Transmission Events

“…Adding to the complexity, a recent study has highlighted that CCR5 exists in heterogeneous conformations and oligomerization states. Different subpopulations of CCR5 were preferred by divergent viruses (93) and importantly, macrophages and T cells expressed different subpopulations of CCR5 and it is likely another factor driving virus strains to be macrophage-tropic or T cell-tropic. It remains to be studied what subpopulations of CCR5 are expressed by all the various tissue myeloid cells that exist at the site of infection or if indeed this is the main determinant of M-tropism.…”

Endogenous Labeling for Light Microscopy during HIV-1 Immune Responses

“…CCR5 exists in diverse conformations and oligomerization states with different strains of HIV-1 binding differently to CCR5 molecules [4]. Binding assays of 35 S-labeled Env from different HIV-1 strains to activated CD4 + T cells has shown that Env recognizes different densities of CCR5 at the cell surface, with the number of CCR5 molecules recognized varying across cell types [4], such as T cells and macrophages.…”

“…CCR5 exists in diverse conformations and oligomerization states with different strains of HIV-1 binding differently to CCR5 molecules [4]. Binding assays of 35 S-labeled Env from different HIV-1 strains to activated CD4 + T cells has shown that Env recognizes different densities of CCR5 at the cell surface, with the number of CCR5 molecules recognized varying across cell types [4], such as T cells and macrophages. Thus, imaging endogenously labeled CD4 and its coreceptors Glossary Bioluminescence resonance energy transfer (BRET): nonradiative phenomenon that occurs between a bioluminescence donor dipole and an acceptor dipole when both are situated at the right distance and orientation.…”