Single-molecule imaging reveals distinct effects of ligands on CCR5 dynamics depending on its dimerization status

G protein-coupled receptors (GPCR) are present at the cell surface in different conformational and oligomeric states. However, how these states impact GPCRs biological function and therapeutic targeting remains incompletely known. Here, we investigated this issue in living cells for the CC chemokine receptor 5 (CCR5), a major receptor in inflammation and the principal entry co-receptor for Human Immunodeficiency Viruses (HIV-1). We used TIRF microscopy and an original statistical method to track and classify the motion of different receptors subpopulations. We showed a diversity of ligand-free forms of CCR5 at the cell surface constituted of various oligomeric states and exhibiting transient Brownian and restricted motions. These forms were stabilized differently by distinct ligands. In particular, agonist stimulation restricted the mobility of CCR5 and led to its clustering, a feature depending on b-arrestin, while inverse agonist stimulation exhibited the opposite effect. These results suggest a link between receptor activation and immobilization. Applied to HIV-1 envelope glycoproteins gp120, our quantitative analysis revealed agonist-like properties of gp120s. Distinct gp120s influenced CCR5 dynamics differently, suggesting that they stabilize different CCR5 conformations. Then, using a dimerization-compromized mutant, we showed that dimerization (i) impacts CCR5 precoupling to G proteins, (ii) is a pre-requisite for the immobilization and clustering of receptors upon activation, and (iii) regulates receptor endocytosis, thereby impacting the fate of activated receptors. This study demonstrates that tracking the dynamic behavior of a GPCR is an efficient way to link GPCR conformations to their functions, therefore improving the development of drugs targeting specific receptor conformations.

Structural basis of the activation of the CC chemokine receptor 5 by a chemokine agonist

The human CC chemokine receptor 5 (CCR5) is a G protein–coupled receptor (GPCR) that plays a major role in inflammation and is involved in cancer, HIV, and COVID-19. Despite its importance as a drug target, the molecular activation mechanism of CCR5, i.e., how chemokine agonists transduce the activation signal through the receptor, is yet unknown. Here, we report the cryo-EM structure of wild-type CCR5 in an active conformation bound to the chemokine super-agonist [6P4]CCL5 and the heterotrimeric Gi protein. The structure provides the rationale for the sequence-activity relation of agonist and antagonist chemokines. The N terminus of agonist chemokines pushes onto specific structural motifs at the bottom of the orthosteric pocket that activate the canonical GPCR microswitch network. This activation mechanism differs substantially from other CC chemokine receptors that bind chemokines with shorter N termini in a shallow binding mode involving unique sequence signatures and a specialized activation mechanism.

Effect of rose extract treatment on soluble CCR5 and CXCR4 secretion by the endothelial cells in vitro

Background: CC-Chemokine Receptor 5 (CCR5) and Chemokine C-X-C-Motif Receptor 4 (CXCR4) are expressed in various tissues, and they are potential molecules involved in multiple pathways. CCR5 and CXCR4 targets are associated with immune regulation in patients in multiple tissues and numerous clinical conditions. The study was performed searching for a novel therapy for immune regulation on these CCR5 and CXCR4 receptors with rose extract. Methods: The crushed red rose extract was prepared, and it was processed for analysis. The HUVEC cells were obtained for seeding in the cell culture. The cells were tested in normal physiological conditions and varying degrees of hypoxia. The cells were treated with extract for 72 hours, and the resultant secreted supernatants were analyzed for expression of CCR5 and CXCR4 by the Elisa technique. Results: The CCR5 levels were significantly elevated at normoxia compared to untreated controls. The surge of CCR5 was persistent in 12% hypoxia, and at higher degrees of hypoxia, the levels were mildly lower than the untreated levels. The CXCR4 levels were not changed in normoxia, and even with significant hypoxia, the levels were similar or mildly reduced compared to untreated values. Conclusion: The rose extract has the potentials to induce the secretion of soluble CCR5 from the HUVEC cells, and it can prevent the reduction of soluble CXCR4 levels during the hypoxic challenge of the endothelial cells. This in-turn can modulate the receptor levels on the endothelial cells, which has clinical applications.

Evaluating the Association between CCR5delta32 Polymorphism (rs333) and the Risk of Breast Cancer in a Cohort of Iranian Population

Background: CC chemokine receptor 5 (CCR5) is introduced as an immune response modulator. The activity of CCR5 influences breast tumour development in a p53-dependent manner. This study aimed to investigate the frequency of CCR5delta32 and its association with the risk of breast cancer in 1038 blood samples in North East of Iran. Methods: In this case-control study, we genotyped 570 control samples and 468 breast cancer patients by a gel electrophoresis-based gap-polymerase chain reaction (gap-PCR) method Mashhad, Iran. The data were analyzed using the SPSS software. Results: Of 570 controls included, 542 (95.09%) had CCR5delta32 wild/wild (W/W) genotype, 28 samples (4.91%) had CCR5delta32 wild/deletion (W/D) genotype and none of them were CCR5delta32 deletion/deletion (D/D) genotype (0%). While 428 samples of patients (91.45%) had CCR5delta32 W/W genotype, 40 samples (8.55%) had CCR5delta32 W/D and CCR5delta32 D/D homozygous was nil (0%) amongst cases. All samples were in the Hardy–Weinberg equilibrium (P>0.05). According to the allele frequency, D allele, as a risky allele, in the cases was more than the control samples (0.0427 vs 0.0245, respectively) (P=0.0206). Hence, W/D genotype may confer a risk effect (OR=1.77, CI: 1.09-2.90; P=0.0206) compared with WW genotype between case and control groups. Conclusion: There is a statistically significant association between CCR5W/D and breast cancer risk. CCR5 may be regarded as a target for the prevention of breast cancer in certain conditions such as interaction with p53 variants, which remains to be further investigated.

CCR5Δ32 Deletion as a Protective Factor in Czech First-Wave COVID-19 Subjects

Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease (COVID-19), has spread widely around the globe. Significant inter-individual differences have been observed during the course of the infection, which suggests that genetic susceptibility may be a contributing factor. CC chemokine receptor 5 (CCR5), which acts as a co-receptor for the entry of HIV-1 into cells, is promising candidate whose can have an influence on SARS-CoV-2 infection. A genetic mutation known as CCR5Δ32, consisting of a 32-nucleotide deletion, encodes a truncated protein that protects homozygous carriers of the deletion from HIV-1 infection. Similarly, inhibition of CCR5 seems to be protective against COVID-19. In our study, we successfully genotyped 416 first-wave SARS-CoV-2-positive infection survivors (164 asymptomatic and 252 symptomatic) for CCR5Δ32, comparing them with a population based sample of 2,404 subjects. We found the highest number (P=0.03) of CCR5Δ32 carriers in SARS-CoV-2-positive/COVID-19-asympto-matic subjects (23.8 %) and the lowest number in SARS-CoV-2-positive/COVID-19-symptomatic patients (16.7 %), with frequency in the control population in the middle (21.0 %). We conclude that the CCR5Δ32 I/D polymorphism may have the potential to predict the severity of SARS-CoV-2 infection.

Structural basis of the activation of the CC chemokine receptor 5 by a chemokine agonist

The human CC chemokine receptor 5 (CCR5) is a G protein-coupled receptor (GPCR) that plays a major role in inflammation and is involved in the pathology of cancer, HIV, and COVID-19. Despite its significance as a drug target, the activation mechanism of CCR5, i.e. how chemokine agonists transduce the activation signal through the receptor, is yet unknown. Here, we report the cryo-EM structure of wild-type CCR5 in an active conformation bound to the chemokine super-agonist [6P4]CCL5 and the heterotrimeric Gi protein. The structure provides the rationale for the sequence-activity relation of agonist and antagonist chemokines. The N-terminus of agonist chemokines pushes onto an aromatic connector that transmits activation to the canonical GPCR microswitch network. This activation mechanism differs significantly from other CC chemokine receptors that bind shorter chemokines in a shallow binding mode and have unique sequence signatures and a specialized activation mechanism.One-sentence summaryThe structure of CCR5 in complex with the chemokine agonist [6P4]CCL5 and the heterotrimeric Gi protein reveals its activation mechanism