Chemokine Receptor Function Research Articles

Structural insights into CXCR4 modulation and oligomerization.

Activation of the chemokine receptor CXCR4 by its chemokine ligand CXCL12 regulates diverse cellular processes. Previously reported crystal structures of CXCR4 revealed the architecture of an inactive, homodimeric receptor. However, many structural aspects of CXCR4 remain poorly understood. Here, we use cryo-electron microscopy to investigate various modes of human CXCR4 regulation. CXCL12 activates CXCR4 by inserting its N terminus deep into the CXCR4 orthosteric pocket. The binding of US Food and Drug Administration-approved antagonist AMD3100 is stabilized by electrostatic interactions with acidic residues in the seven-transmembrane-helix bundle. A potent antibody blocker, REGN7663, binds across the extracellular face of CXCR4 and inserts its complementarity-determining region H3 loop into the orthosteric pocket. Trimeric and tetrameric structures of CXCR4 reveal modes of G-protein-coupled receptor oligomerization. We show that CXCR4 adopts distinct subunit conformations in trimeric and tetrameric assemblies, highlighting how oligomerization could allosterically regulate chemokine receptor function.

CXCR4 WHIM syndrome is a cancer predisposition condition for virus-induced malignancies.

Warts, hypogammaglobulinaemia, infections and myelokathexissyndrome (WHIMS) is a rare combined primary immunodeficiency caused by the gain of function of the CXCR4 chemokine receptor. We present the prevalence of cancer in WHIMS patients based on data from the French Severe Chronic Neutropenia Registry and an exhaustive literature review. The median follow-up of the 14 WHIMS 'patients was 28.5 years. A central review and viral evaluation of pathological samples were organized, and we conducted a thorough literature review to identify all reports of WHIMS cases. Six French patients were diagnosed with cancer at a median age of 37.6 years. The 40-year risk of malignancy was 39% (95% confidence interval [CI]: 6%-74%). We observed two human papillomavirus (HPV)-induced vulvar carcinomas, three lymphomas (two Epstein-Barr virus [EBV]-related) and one basal cell carcinoma. Among the 155 WHIMS cases from the literature, 22 cancers were reported in 16 patients, with an overall cancer 40-year risk of 23% (95% CI: 13%-39%). Malignancies included EBV-associated lymphoproliferative disorders and HPV-positive genital and anal cancers as in the French cohort. Worldwide, nine cases of malignancy were associated with HPV and four with EBV. Immunocompromised WHIMS patients appear to be particularly susceptible to developing early malignancy, mainly HPV-induced carcinomas, followed by EBV-related lymphomas.

Chemokine receptors in primary and secondary lymphoid tissues.

Chemokine receptors are a complex superfamily of surface G protein-coupled receptors present mostly in leukocytes. In this chapter, we review the presence and functions of chemokine receptors in the immune cells of the primary and secondary lymphoid organs. Those include bone marrow, thymus, spleen, lymph nodes, and Peyer's patches as the main components of the gut-associated lymphoid tissue. There are general groups of chemokine receptors: conventional and atypical. We will mostly cover the role of conventional chemokine receptors, which are divided into four classes (CC, CXC, CX3C, and XC). Some relevant members are CXCR4, CXCR5, CCR4 and CCR7. For example, CXCR4 is a key chemokine receptor in the bone marrow controlling from the homing of progenitor cells into the bone marrow, the development of B cells, to the homing of long-lived plasma cells to this primary lymphoid organ. CCR7 and CCR4 are two of the main players in the thymus. CCR7 along with CCR9 control the traffic of thymic seed progenitors into the thymus, while CCR4 and CCR7 are critical for the entry of thymocytes into the medulla and as controllers of the central tolerance in the thymus. CXCR4 and CXCR5 have major roles in the spleen, guiding the maturation and class-switching of B cells in the different areas of the germinal center. In the T-cell zone, CCR7 guides the differentiation of naïve T cells. CCR7 also controls and directs the entry of T cells, B cells, and dendritic cells into secondary lymphoid tissues, including the spleen and lymph nodes. As new technologies emerge, techniques such as high dimensional spectral flow cytometry or single-cell sequencing allow a more comprehensive knowledge of the chemokine receptor network and their ligands, as well as the discovery of new interactions mediating unknown and overlooked mechanisms in health and disease.

Canonical and atypical chemokine receptors in the neutrophil life cycle

Chemokines are mainly studied for their local function in the control of leukocyte extravasation in homeostatic and inflammatory conditions. However, they have additional roles at the systemic level including the regulation of the hematopoietic process and leukocyte differentiation. Due to the redundancy and pleiotropicity of the chemokine system, chemokines have often multiple and complex roles in neutrophil differentiation ranging from retention and control of proliferation of progenitors to the mobilization of mature cells from the bone marrow (BM) to the bloodstream and their further differentiation in tissues. Atypical chemokine receptors (ACKRs) are regulators of the chemokine system by controlling chemokine bioavailability and chemokine receptor function. Even though ACKRs bind a wide range of chemokines, they appear to have a selective role in the process of neutrophil production and differentiation. The aim of this review is to give an overview of the current evidence regarding the role of chemokines and chemokine receptors in the life of neutrophils with a focus on the regulation exerted by ACKRs.

CXCR4-Targeted Radiopharmaceuticals for the Imaging and Therapy of Malignant Tumors.

C-X-C chemokine receptor type 4 (CXCR4), also known as fusin or CD184, is a 7-transmembrane helix G-protein-coupled receptor that is encoded by the CXCR4 gene. Involved in various physiological processes, CXCR4 could form an interaction with its endogenous partner, chemokine ligand 12 (CXCL12), which is also named SDF-1. In the past several decades, the CXCR4/CXCL12 couple has attracted a large amount of research interest due to its critical functions in the occurrence and development of refractory diseases, such as HIV infection, inflammatory diseases, and metastatic cancer, including breast cancer, gastric cancer, and non-small cell lung cancer. Furthermore, overexpression of CXCR4 in tumor tissues was shown to have a high correlation with tumor aggressiveness and elevated risks of metastasis and recurrence. The pivotal roles of CXCR4 have encouraged an effort around the world to investigate CXCR4-targeted imaging and therapeutics. In this review, we would like to summarize the implementation of CXCR4-targeted radiopharmaceuticals in the field of various kinds of carcinomas. The nomenclature, structure, properties, and functions of chemokines and chemokine receptors are briefly introduced. Radiopharmaceuticals that could target CXCR4 will be described in detail according to their structure, such as pentapeptide-based structures, heptapeptide-based structures, nonapeptide-based structures, etc. To make this review a comprehensive and informative article, we would also like to provide the predictive prospects for the CXCR4-targeted species in future clinical development.

The Chemokine, CCL20, and Its Receptor, CCR6, in the Pathogenesis and Treatment of Psoriasis and Psoriatic Arthritis.

Chemokines represent a superfamily of immune-modulatory small protein molecules that regulate leukocyte migration to inflammatory sites through their chemoattractant and cell signaling properties. This review focuses on the immunological functions of the CCR6 chemokine receptor and is chemokine ligand, CCL20, that contribute to it role in inflammation in human psoriasis. Peer-reviewed relevant articles are searched and selected from 2000 to 2022 using the search engines including PubMed and Google Scholar. After selectively reviewing and evaluating over seventy articles, a comprehensive overview on the immunology of CCL20-CCR6 axis in psoriasis and psoriatic arthritis, the X-ray crystal structures of CCL20 monomers, and the potential of developing clinical therapies targeting this axis is summarized. Over the past decade, preclinical studies carried out in animal models of psoriasis involving agents targeting CCL20-CCR6 axis have yielded promising results. Other studies that this axis may play a role in a number of other autoimmune diseases, including rheumatoid arthritis, suggesting a rationale for further investigation into this key signaling/migratory pathway.

“Glyco-sulfo barcodes” regulate chemokine receptor function

Chemokine ligands and receptors regulate the directional migration of leukocytes. Post-translational modifications of chemokine receptors including O-glycosylation and tyrosine sulfation have been reported to regulate ligand binding and resulting signaling. Through in silico analyses, we determined potential conserved O-glycosylation and sulfation sites on human and murine CC chemokine receptors. Glyco-engineered CHO cell lines were used to measure the impact of O-glycosylation on CC chemokine receptor CCR5, while mutation of tyrosine residues and treatment with sodium chlorate were performed to determine the effect of tyrosine sulfation. Changing the glycosylation or tyrosine sulfation on CCR5 reduced the receptor signaling by the more positively charged CCL5 and CCL8 more profoundly compared to the less charged CCL3. The loss of negatively charged sialic acids resulted only in a minor effect on CCL3-induced signal transduction. The enzymes GalNAc-T1 and GalNAc-T11 were shown to be involved in the process of chemokine receptor O-glycosylation. These results indicate that O-glycosylation and tyrosine sulfation are involved in the fine-tuning and recognition of chemokine interactions with CCR5 and the resulting signaling.

Regulation and Function of Chemokines at the Maternal-Fetal Interface.

Successful pregnancy requires the maternal immune system to tolerate the semi-allogeneic embryo. A good trophoblast function is also essential for successful embryo implantation and subsequent placental development. Chemokines are initially described in recruiting leukocytes. There are rich chemokines and chemokine receptor system at the maternal–fetal interface. Numerous studies have reported that they not only regulate trophoblast biological behaviors but also participate in the decidual immune response. At the same time, the chemokine system builds an important communication network between fetally derived trophoblast cells and maternally derived decidual cells. However, abnormal functions of chemokines or chemokine receptors are involved in a series of pregnancy complications. As growing evidence points to the roles of chemokines in pregnancy, there is a great need to summarize the available data on this topic. This review aimed to describe the recent research progress on the regulation and function of the main chemokines in pregnancy at the maternal–fetal interface. In addition, we also discussed the potential relationship between chemokines and pregnancy complications.

Effect of CXC chemokine receptor 7 on cell cycle of neuronal cells in ischemic stroke

To investigate the function and mechanism of CXC chemokine receptor 7 (CXCR7) in neuronal cells of ischemic stroke. The expression of CXCR7 in human neuroblastoma SH-SY5Y cells was interfered by small interfering RNA (si-RNA) technique. Oxygen-glucose deprivation/reoxygenation (OGD/R) injury model was constructed in SH-SY5Y cells. CXCR7 protein expression and cell cycle were detected by flow cytometry (FCM). The protein expression of CXCR7 and Akt signaling pathway was detected by Western blotting. After 6 hours of OGD/R, the expression of CXCR7 was significantly decreased compared with OGD/R 0 hour (CXCR7/GAPDH: 0.483±0.098 vs. 1.000±0.000 by Western blotting and 0.686±0.0524 vs. 1.000±0.000 by FCM, both P < 0.01), cell cycle arrest in G0/G1 phase (1.190±0.040 vs. 1.000±0.000, P < 0.01). After CXCR7 si-RNA interference with SH-SY5Y cells, OGD/R was constructed again for 6 hours. Compared with negative control group (si-NC group) under the same environment, the expression of CXCR7 and phosphorylated Akt (p-Akt) was significantly decreased (CXCR7/GAPDH: 0.471±0.051 vs. 1.000±0.000, p-Akt/GAPDH: 0.616±0.027 vs. 1.000±0.000, both P < 0.001) and cell cycle arrest in G0/G1 phase (1.105±0.033 vs. 1.000±0.000, P < 0.05). The CXCR7 could regulate the cycle of neuronal cells in ischemic stroke through Akt signaling pathway, which has a protective effect on neuronal cells.

Patient-Oriented Perspective on Chemokine Receptor Expression and Function in Glioma.

Simple SummaryChemokines and their receptors have been pointed out as key actors in a variety of human cancers, playing pivotal roles in multiples processes and pathways. The present study aims at deciphering the functions of several chemokine receptors in gliomas, starting from publicly available patient-derived transcriptomic data with support from the current literature in the field, and sheds light on the clinical relevance of chemokine receptors in targeted therapeutic approaches for glioma patients.Gliomas are severe brain malignancies, with glioblastoma (GBM) being the most aggressive one. Despite continuous efforts for improvement of existing therapies, overall survival remains poor. Over the last years, the implication of chemokines and their receptors in GBM development and progression has become more evident. Recently, large amounts of clinical data have been made available, prompting us to investigate chemokine receptors in GBM from a still-unexplored patient-oriented perspective. This study aims to highlight and discuss the involvement of chemokine receptors—CCR1, CCR5, CCR6, CCR10, CX3CR1, CXCR2, CXCR4, ACKR1, ACKR2, and ACKR3—most abundantly expressed in glioma patients based on the analysis of publicly available clinical datasets. Given the strong intratumoral heterogeneity characterizing gliomas and especially GBM, receptor expression was investigated by glioma molecular groups, by brain region distribution, emphasizing tissue-specific receptor functions, and by cell type enrichment. Our study constitutes a clinically relevant and patient-oriented guide that recapitulates the expression profile and the complex roles of chemokine receptors within the highly diversified glioma landscape. Additionally, it strengthens the importance of patient-derived material for development and precise amelioration of chemokine receptor-targeting therapies.

PET Imaging Radiotracers of Chemokine Receptors

Chemokines and chemokine receptors have been recognized as critical signal components that maintain the physiological functions of various cells, particularly the immune cells. The signals of chemokines/chemokine receptors guide various leukocytes to respond to inflammatory reactions and infectious agents. Many chemokine receptors play supportive roles in the differentiation, proliferation, angiogenesis, and metastasis of diverse tumor cells. In addition, the signaling functions of a few chemokine receptors are associated with cardiac, pulmonary, and brain disorders. Over the years, numerous promising molecules ranging from small molecules to short peptides and antibodies have been developed to study the role of chemokine receptors in healthy states and diseased states. These drug-like candidates are in turn exploited as radiolabeled probes for the imaging of chemokine receptors using noninvasive in vivo imaging, such as positron emission tomography (PET). Recent advances in the development of radiotracers for various chemokine receptors, particularly of CXCR4, CCR2, and CCR5, shed new light on chemokine-related cancer and cardiovascular research and the subsequent drug development. Here, we present the recent progress in PET radiotracer development for imaging of various chemokine receptors.

More Levels of Complexity in the Control of Intestinal Inflammation

More Levels of Complexity in the Control of Intestinal Inflammation

CXCL14 Preferentially Synergizes With Homeostatic Chemokine Receptor Systems.

Reflecting their importance in immunity, the activity of chemokines is regulated on several levels, including tissue and context-specific expression and availability of their cognate receptor on target cells. Chemokine synergism, affecting both chemokine and chemokine receptor function, has emerged as an additional control mechanism. We previously demonstrated that CXCL14 is a positive allosteric modulator of CXCR4 in its ability to synergize with CXCL12 in diverse cellular responses. Here, we have extended our study to additional homeostatic, as well as a selection of inflammatory chemokine systems. We report that CXCL14 strongly synergizes with low (sub-active) concentrations of CXCL13 and CCL19/CCL21 in in vitro chemotaxis with immune cells expressing the corresponding receptors CXCR5 and CCR7, respectively. CXCL14 by itself was inactive, not only on cells expressing CXCR5 or CCR7 but also on cells expressing any other known conventional or atypical chemokine receptor, as assessed by chemotaxis and/or β-arrestin recruitment assays. Furthermore, synergistic migration responses between CXCL14 and inflammatory chemokines CXCL10/CXCL11 and CCL5, targeting CXCR3 and CCR5, respectively, were marginal and occasional synergistic Ca2+ flux responses were observed. CXCL14 bound to 300-19 cells and interfered with CCL19 binding to CCR7-expressing cells, suggesting that these cellular interactions contributed to the reported CXCL14-mediated synergistic activities. We propose a model whereby tissue-expressed CXCL14 contributes to cell localization under steady-state conditions at sites with prominent expression of homeostatic chemokines.

Modulating endothelial adhesion and migration impacts stem cell therapies efficacy.

BackgroundLimited knowledge of stem cell therapies` mechanisms of action hampers their sustainable implementation into the clinic. Specifically, the interactions of transplanted stem cells with the host vasculature and its implications for their therapeutic efficacy are not elucidated. We tested whether adhesion receptors and chemokine receptors on stem cells can be functionally modulated, and consequently if such modulation may substantially affect therapeutically relevant stem cell interactions with the host endothelium.MethodsWe investigated the effects of cationic molecule polyethylenimine (PEI) treatment with or without nanoparticles on the functions of adhesion receptors and chemokine receptors of human bone marrow-derived Mesenchymal Stem Cells (MSC). Analyses included MSC functions in vitro, as well as homing and therapeutic efficacy in rodent models of central nervous system´s pathologies in vivo.FindingsPEI treatment did not affect viability, immunomodulation or differentiation potential of MSC, but increased the CCR4 expression and functionally blocked their adhesion receptors, thus decreasing their adhesion capacity in vitro. Intravenously applied in a rat model of brain injury, the homing rate of PEI-MSC in the brain was highly increased with decreased numbers of adherent PEI-MSC in the lung vasculature. Moreover, in comparison to untreated MSC, PEI-MSC featured increased tumour directed migration in a mouse glioblastoma model, and superior therapeutic efficacy in a murine model of stroke.InterpretationBalanced stem cell adhesion and migration in different parts of the vasculature and tissues together with the local microenvironment impacts their therapeutic efficacy.FundingRobert Bosch Stiftung, IZEPHA grant, EU grant 7 FP Health

Functions of the CXCL12 Receptor ACKR3/CXCR7-What Has Been Perceived and What Has Been Overlooked.

The CXCL12 system is central to the development of many organs and is further crucially engaged in pathophysiological processes underlying cancer, inflammation, and cardiovascular disorders. This disease-associated role presently focuses major interest on the two CXCL12 receptors, CXCR4 and atypical chemokine receptor 3 (ACKR3)/CXCR7, as promising therapeutic targets. Major obstacles in these ongoing efforts are confusing reports on the differential use of either ACKR3/CXCR7 and/or CXCR4 across various cells as well as on the specific function(s) of ACKR3/CXCR7. Although basically no doubts remain that CXCR4 represents a classic chemokine receptor, functions assigned to ACKR3/CXCR7 range from those of a strictly silent scavenger receptor eventually modulating CXCR4 signaling to an active and independent signaling receptor. In this review, we depict a thorough analysis of our present knowledge on different modes of organization and functions of the cellular CXCL12 system. We further highlight the potential role of ACKR3/CXCR7 as a "crosslinker" of different receptor systems. Finally, we discuss mechanisms with the potency to impinge on the cellular organization of the CXCL12 system and hence might represent additional future therapeutic targets. SIGNIFICANCE STATEMENT: Delineating the recognized functions of atypical chemokine receptor 3 and CXCR4 in CXCL12 signaling is central to the more detailed understanding of the role of the CXCL12 system in health and disease and will help to guide future research efforts.

Dispensable role of chemokine receptors in migration of mycobacterial antigen-specific CD4+ T cells into mycobacteria-infected lung

Abstract Mycobacterial antigen-specific CD4+ Th1 cells have a pivotal role in protective immunity against mycobacterial infections, including pulmonary tuberculosis. In the course of infection, Th1 cells differentiate in the lung-draining lymph nodes and migrate into the infected lung. Chemokine receptors on T cells are involved in T cell migration into the intestine and skin. However, the role of chemokine receptors in the migration of CD4+ T cells into the lung has not yet been determined. To address this issue, the role of chemokine receptors in T cell migration into the mycobacteria-infected lung was analyzed using mycobacterial Ag85B peptide 25-specific T cell receptor-transgenic (P25) CD4+ T cells. P25 T cells in the Mycobacterium bovis BCG-infected lung and lung-draining mediastinal lymph nodes (MedLN) expressed the chemokine receptors, CCR5, CCR6, CXCR3, and CXCR5, which bind chemokines produced by the BCG-infected lung. To further analyze the role of chemokine receptors in the migration of BCG-primed P25 T cells into the lung and medLN, P25 T cells were adoptively transferred into BCG-infected wild-type mice and their migration into the lung was monitored. Unexpectedly, blocking chemokine receptor function with pertussis toxin, a G-protein inhibitor, failed to suppress migration of T cells into the infected lung. However, the treatment completely blocked migration of the MedLN P25 T cells into the recipient lymph node. These results suggest that the interaction of chemokine receptors on mycobacterial antigen-specific Th1 cells with chemokines is dispensable for their migration into the mycobacteria-infected lung.

CRISPR-Mediated Protein Tagging with Nanoluciferase to Investigate Native Chemokine Receptor Function and Conformational Changes

SummaryG protein-coupled receptors are a major class of membrane receptors that mediate physiological and pathophysiological cellular signaling. Many aspects of receptor activation and signaling can be investigated using genetically encoded luminescent fusion proteins. However, the use of these biosensors in live cell systems requires the exogenous expression of the tagged protein of interest. To maintain the normal cellular context here we use CRISPR/Cas9-mediated homology-directed repair to insert luminescent tags into the endogenous genome. Using NanoLuc and bioluminescence resonance energy transfer we demonstrate fluorescent ligand binding at genome-edited chemokine receptors. We also demonstrate that split-NanoLuc complementation can be used to investigate conformational changes and internalization of CXCR4 and that recruitment of β-arrestin2 to CXCR4 can be monitored when both proteins are natively expressed. These results show that genetically encoded luminescent biosensors can be used to investigate numerous aspects of receptor function at native expression levels.

The expression and biological function of chemokine CXCL12 and receptor CXCR4/CXCR7 in placenta accreta spectrum disorders.

ObjectivesInvestigation of mechanism related to excessive invasion of trophoblast cells in placenta accreta spectrum disorders (PAS) provides more strategies and ideas for clinical diagnosis and treatment.Materials and MethodsBlood and placental samples were collected from included patients. The distribution and expression of CXCL12, CXCR4 and CXCR7 proteins in the paraffin of placental tissue in the included cases were analysed, and we analyse the downstream pathways or key proteins involved in cell invasion.ResultsFirstly, our results determined that CXCL12 and CXCR4/CXCR7 were increased in extravillous trophoblastic cell (CXCL12: P < .001; CXCR4: P < .001; CXCR7: P < .001), and the expression levels were closely related to the invasion depth of trophoblastic cells. Secondly, CXCL12 has the potential to become a biochemical indicator of PAS since the high expression of placental trophoblast CXCL12 may be an important source of blood CXCL12. Using lentivirus‐mediated RNA interference and overexpression assay, it was found that both chemokine CXCL12 and receptor CXCR4/CXCR7 are associated with regulation of trophoblast cell proliferation, migration and invasion. Further results proved that through the activating the phosphorylation and increasing the expression of MLC and AKT proteins in the Rho/rock, PI3K/AKT signalling pathway, CXCL12, CXCR4 and CXCR7 could up‐regulate the expression of RhoA, Rac1 and Cdc42 proteins to promote the migration and invasion of extravillous trophoblastic cell and ultimately formate the placenta accrete compare to the normal placenta.ConclusionsOur research proved that trophoblasts may contribute to a PAS‐associated increase in CXCL12 levels in maternal blood. CXCL12 is not only associated with biological roles of PAS, but may also be potential for prediction of PAS.

New insights into the structure and function of chemokine receptor:chemokine complexes from an experimental perspective.

Chemokines are small soluble proteins that drive cell migration through the formation of concentration gradients. Chemokine binding to G protein-coupled chemokine receptors in the cell membrane activates intracellular signaling pathways and is a fundamental process involved in numerous physiological and pathophysiological functions. In the past few years, significant experimental developments have made it possible to characterize complexes between chemokine receptors and chemokines at a molecular level. Here, I review these developments from an experimental perspective, focusing on how the ability to express, purify, and stabilize receptor:chemokine complexes have made studies by X-ray crystallography, nuclear magnetic resonance, and other methods possible. I give examples of how these studies have advanced our understanding of the architecture of receptor:chemokine complexes as well as the mechanisms involved in complex formation. Finally, I discuss some of the many remaining questions and challenges that will require studies of more receptors and chemokines as well as further development of experimental methods.

CXC Chemokine Receptors in the Tumor Microenvironment and an Update of Antagonist Development.

Chemokine receptors, a diverse group within the seven-transmembrane G protein-coupled receptor superfamily, are frequently overexpressed in malignant tumors. Ligand binding activates multiple downstream signal transduction cascades that drive tumor growth and metastasis, resulting in poor clinical outcome. These receptors are thus considered promising targets for anti-tumor therapy. This article reviews recent studies on the expression and function of CXC chemokine receptors in various tumor microenvironments and recent developments in cancer therapy using CXC chemokine receptor antagonists.