Conformational dynamics underlying atypical chemokine receptor 3 activation.

Atypical Chemokine Receptor 3 (ACKR3) belongs to the G protein-coupled receptor family but it does not signal through G proteins. The structural properties that govern the functional selectivity and the conformational dynamics of ACKR3 activation are poorly understood. Here, we combined hydrogen/deuterium exchange mass spectrometry, site-directed mutagenesis, and molecular dynamics simulations to examine the binding mode and mechanism of action of ACKR3 ligands of different efficacies. Our results show that activation or inhibition of ACKR3 is governed by intracellular conformational changes of helix 6, intracellular loop 2, and helix 7, while the DRY motif becomes protected during both processes. Moreover, we identified the binding sites and the allosteric modulation of ACKR3 upon ß-arrestin 1 binding. In summary, this study highlights the structure-function relationship of small ligands, the binding mode of ß-arrestin 1, the activation dynamics, and the atypical dynamic features in ACKR3 that may contribute to its inability to activate G proteins.

ACKR3 in olfactory glia cells shapes the immune defense of the olfactory mucosa.

Barrier-forming olfactory glia cells, termed sustentacular cells, play important roles for immune defense of the olfactory mucosa, for example as entry sites for SARS-CoV-2 and subsequent development of inflammation-induced smell loss. Here we demonstrate that sustentacular cells express ACKR3, a chemokine receptor that functions both as a scavenger of the chemokine CXCL12 and as an activator of alternative signaling pathways. Differential gene expression analysis of bulk RNA sequencing data obtained from WT and ACKR3 conditional knockout mice revealed upregulation of genes involved in immune defense. To map the regulated genes to the different cell types of the olfactory mucosa, we employed biocomputational methods utilizing a single-cell reference atlas. Transcriptome analysis, PCR and immunofluorescence identified up-regulation of NF-κB-related genes, known to amplify inflammatory signaling and to facilitate leukocyte transmigration, in the gliogenic lineage. Accordingly, we found a marked increase in leukocyte-expressed genes and confirmed leukocyte infiltration into the olfactory mucosa. In addition, lack of ACKR3 led to enhanced expression and secretion of early mediators of immune defense by Bowman's glands. As a result, the number of apoptotic cells in the epithelium was decreased. In conclusion, our research underlines the importance of sustentacular cells in immune defense of the olfactory mucosa. Moreover, it identifies ACKR3, a druggable G protein-coupled receptor, as a promising target for modulation of inflammation-associated anosmia.

The CXCL12/CXCR4/ACKR3 Axis in the Tumor Microenvironment: Signaling, Crosstalk, and Therapeutic Targeting.

Elevated expression of the chemokine receptors CXCR4 and ACKR3 and of their cognate ligand CXCL12 is detected in a wide range of tumors and the tumor microenvironment (TME). Yet, the molecular mechanisms by which the CXCL12/CXCR4/ACKR3 axis contributes to the pathogenesis are complex and not fully understood. To dissect the role of this axis in cancer, we discuss its ability to impinge on canonical and less conventional signaling networks in different cancer cell types; its bidirectional crosstalk, notably with receptor tyrosine kinase (RTK) and other factors present in the TME; and the infiltration of immune cells that supporttumor progression. We discuss current and emerging avenues that target the CXCL12/CXCR4/ACKR3 axis. Coordinately targeting both RTKs and CXCR4/ACKR3 and/or CXCL12 is an attractive approach to consider in multitargeted cancer therapies. In addition, inhibiting infiltrating immune cells or reactivating the immune system along with modulating the CXCL12/CXCR4/ACKR3 axis in the TME has therapeutic promise.

ACKR3 Antagonism Enhances the Repair of Demyelinated Lesions Through Both Immunomodulatory and Remyelinating Effects.

Addressing inflammation, demyelination, and associated neurodegeneration in inflammatory demyelinating diseases like multiple sclerosis (MS) remains challenging. ACT-1004-1239, a first-in-class and potent ACKR3 antagonist, currently undergoing clinical development, showed promise in preclinical MS models, reducing neuroinflammation and demyelination. However, its effectiveness in treating established disease and impact on remyelination after the occurrence of demyelinated lesions remain unexplored. This study assessed the therapeutic effect of ACT-1004-1239 in two demyelinating disease models. In the proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) model, ACT-1004-1239 administered upon the detection of the first signs of paralysis, resulted in a dose-dependent reduction in EAE disease severity, concomitant with diminished immune cell infiltrates in the CNS and reduced demyelination. Notably, efficacy correlated with elevated plasma concentrations of CXCL11 and CXCL12, two pharmacodynamic biomarkers of ACKR3 antagonism. Combining ACT-1004-1239 with siponimod, an approved immunomodulatory treatment for MS, synergistically reduced EAE severity. In the cuprizone-induced demyelination model, ACT-1004-1239 administered after 5 weeks of cuprizone exposure, significantly accelerated remyelination, already quantifiable one week after cuprizone withdrawal. Additionally, ACT-1004-1239 penetrated the CNS, elevating brain CXCL12 concentrations. These results demonstrate that ACKR3 antagonism significantly reduces the severity of experimental demyelinating diseases, even when treatment is initiated therapeutically, after the occurrence of lesions. It confirms the dual mode of action of ACT-1004-1239, exhibiting both immunomodulatory effects by reducing neuroinflammation and promyelinating effects by accelerating myelin repair. The results further strengthen the rationale for evaluating ACT-1004-1239 in clinical trials for patients with demyelinating diseases.

BMP2 induces osteogenic differentiation through ACKR3 in mesenchymal stem cells.

In recent years, bone loss related diseases have attracted more and more attention, such as osteoporosis and osteonecrosis of the femoral head exhibited symptoms of osteopenia or insufficient bone mass in a certain stage. Mesenchymal stem cells (MSCs), which can be induced to differentiate into osteoblasts under certain conditions can provide a new solution bone disease. Herein, we deciphered the possible mechanism by which BMP2 drives the transduction of MSCs to the osteoblast lineage through ACKR3/p38/MAPK signaling. The levels of ACKR3 in femoral tissues of samples from humans with different ages and sexes were measured firstly and found that ACKR3 protein levels increase with age. In vitro cellular assays showed that ACKR3 inhibits BMP2-induced osteo-differentiation and promotes adipo-differentiation of MSCs, whereas siACKR3 exhibited the opposite effects. In vitro embryo femur culture experiment showed that inhibition of ACKR3 enhanced BMP2-induced trabecular bone formation in C57BL6/J mouse. In terms of molecular mechanisms, we found that p38/MAPK signaling might play the key role. ACKR3 agonist TC14012 suppressed the phosphorylation of p38 and STAT3 in BMP2 induced MSCs differentiation. Our findings suggested that ACKR3 might be a novel therapeutic target for the treatment of bone-associated diseases and bone-tissue engineering.

ACKR3 orchestrates Hedgehog signaling to promote renal cell carcinoma progression.

Renal cell carcinoma (RCC) is the second commonest urological malignant neoplasm and mortality rate of patients with RCC appears to be increasing each year. Thus, further understanding of the molecular mechanisms responsible for the development and progression of RCC is of particular importance. Here, we report that atypical chemokine receptor 3 (ACKR3) orchestrates the Hedgehog (Hh)-GLI1 signaling to promote RCC progression. The expression of ACKR3 is elevated in RCC tissues, which is associated with malignant and clinical outcomes of RCC, and ACKR3 expression is positively correlated with GLI1 expression in RCC tissues. Mechanically, Hh promotes RCC progression through GLI1-mediated ACKR3 transcription by the directly binding of GLI1 to ACKR3 gene, while CXCL12-ACKR3 axis simultaneously enhances Hh activation via the binding of ACKR3 to Smoothened (SMO), a receptor in Hh pathway, resulting in the upregulation of SMO phosphorylation that potentiates downstream signal activity and consequently contributes to RCC progression. Thus, our findings may provide with the evidence of developing a novel treatment method with specific target for RCC.

Endothelial ACKR3 drives atherosclerosis by promoting immune cell adhesion to vascular endothelium.

Atherosclerosis is the foundation of potentially fatal cardiovascular diseases and it is characterized by plaque formation in large arteries. Current treatments aimed at reducing atherosclerotic risk factors still allow room for a large residual risk; therefore, novel therapeutic candidates targeting inflammation are needed. The endothelium is the starting point of vascular inflammation underlying atherosclerosis and we could previously demonstrate that the chemokine axis CXCL12-CXCR4 plays an important role in disease development. However, the role of ACKR3, the alternative and higher affinity receptor for CXCL12 remained to be elucidated. We studied the role of arterial ACKR3 in atherosclerosis using western diet-fed Apoe-/- mice lacking Ackr3 in arterial endothelial as well as smooth muscle cells. We show for the first time that arterial endothelial deficiency of ACKR3 attenuates atherosclerosis as a result of diminished arterial adhesion as well as invasion of immune cells. ACKR3 silencing in inflamed human coronary artery endothelial cells decreased adhesion molecule expression, establishing an initial human validation of ACKR3's role in endothelial adhesion. Concomitantly, ACKR3 silencing downregulated key mediators in the MAPK pathway, such as ERK1/2, as well as the phosphorylation of the NF-kB p65 subunit. Endothelial cells in atherosclerotic lesions also revealed decreased phospho-NF-kB p65 expression in ACKR3-deficient mice. Lack of smooth muscle cell-specific as well as hematopoietic ACKR3 did not impact atherosclerosis in mice. Collectively, our findings indicate that arterial endothelial ACKR3 fuels atherosclerosis by mediating endothelium-immune cell adhesion, most likely through inflammatory MAPK and NF-kB pathways.

The CXCL12/CXCR4/ACKR3 Response Axis in Chronic Neurodegenerative Disorders of the Central Nervous System: Therapeutic Target and Biomarker.

There has been an increase in the incidence of chronic neurodegenerative disorders of the central nervous system, including Alzheimer's and Parkinson's diseases, over the recent years mostly due to the rise in the number of elderly individuals. In addition, various neurodegenerative disorders are related to imbalances in the CXCL12/CXCR4/ACKR3 response axis. Notably, the CXC Chemokine Ligand 12 (CXCL12) is essential for the development of the central nervous system. Moreover, the expression and distribution of CXCL12 and its receptors are associated with the aggravation or alleviation of symptoms of neurodegenerative disorders. Therefore, the current review sought to highlight the specific functions of CXCL12 and its receptors in various neurodegenerative disorders, in order to provide new insights for future research.

Atypical chemokine receptor 3 induces colorectal tumorigenesis in mice by promoting ß-arrestin-NOLC1-fibrillarin-dependent rRNA biogenesis.

Atypical chemokine receptor 3 (ACKR3) has emerged as a key player in various biological processes. Its atypical "intercepting receptor" properties have established ACKR3 as the major regulator in the pathophysiological processes in many diseases. In this study, we investigated the role of ACKR3 activation in promoting colorectal tumorigenesis. We showed that ACKR3 expression levels were significantly increased in human colon cancer tissues, and high levels of ACKR3 predicted the increased severity of cancer. In Villin-ACKR3 transgenic mice with a high expression level of CKR3 in their intestinal epithelial cells, administration of AOM/DSS induced more severe colorectal tumorigenesis than their WT littermates. Cancer cells of Villin-ACKR3 transgenic mice were characterised by the nuclear ß-arrestin-1 (ß-arr1)-activated perturbation of rRNA biogenesis. In HCT116 cells, cotreatment with CXCL12 and AMD3100 selectively activated ACKR3 and induced nuclear translocation of ß-arr1, leading to an interaction of ß-arr1 with nucleolar and coiled-body phosphoprotein 1 (NOLC1). NOLC1, as the phosphorylated protein, further interacted with fibrillarin, a conserved nucleolar methyltransferase responsible for ribosomal RNA methylation in the nucleolus, thereby increasing the methylation in histone H2A and promoting rRNA transcription in ribosome biogenesis. In conclusion, ACKR3 promotes colorectal tumorigenesis through the perturbation of rRNA biogenesis by the ß-arr1-induced interaction of NOLC1 with fibrillarin.

Crosstalk between CXCR4/ACKR3 and EGFR Signaling in Breast Cancer Cells.

A better understanding of the complex crosstalk among key receptors and signaling pathways involved in cancer progression is needed to improve current therapies. We have investigated in cell models representative of the major subtypes of breast cancer (BC) the interplay between the chemokine CXCL12/CXCR4/ACKR3 and EGF receptor (EGFR) family signaling cascades. These cell lines display a high heterogeneity in expression profiles of CXCR4/ACKR3 chemokine receptors, with a predominant intracellular localization and different proportions of cell surface CXCR4+, ACKR3+ or double-positive cell subpopulations, and display an overall modest activation of oncogenic pathways in response to exogenous CXCL12 alone. Interestingly, we find that in MDA-MB-361 (luminal B subtype, Her2-overexpressing), but not in MCF7 (luminal A) or MDA-MB-231 (triple negative) cells, CXCR4/ACKR3 and EGFR receptor families share signaling components and crosstalk mechanisms to concurrently promote ERK1/2 activation, with a key involvement of the G protein-coupled receptor kinase 2 (GRK2) signaling hub and the cytosolic tyrosine kinase Src. Our findings suggest that in certain BC subtypes, a relevant cooperation between CXCR4/ACKR3 and growth factor receptors takes place to integrate concurrent signals emanating from the tumor microenvironment and foster cancer progression.

Ligand-specific conformational transitions and intracellular transport are required for atypical chemokine receptor 3-mediated chemokine scavenging.

The atypical chemokine receptor ACKR3 contributes to chemotaxis by binding, internalizing, and degrading the chemokines CXCL11 and CXCL12 to shape and terminate chemotactic gradients during development and immune responses. Although unable to trigger G protein activation, both ligands activate G protein-independent ACKR3 responses and prompt arrestin recruitment. This offers a model to specifically study ligand-specific receptor conformations leading to G protein-independent signaling and to functional parameters such as receptor transport and chemokine degradation. We here show chemokine specificity in arrestin recruitment, by different effects of single amino acid substitutions in ACKR3 on arrestin in response to CXCL12 or CXCL11. Chemokine specificity in receptor transport was also observed, as CXCL11 induced faster receptor internalization, slower recycling, and longer intracellular sojourn of ACKR3 than CXCL12. Internalization and recycling rates of the ACKR3 R1423.50A substitution in response to each chemokine were similar; however, ACKR3 R1423.50A degraded only CXCL12 and not CXCL11. This suggests that ligand-specific intracellular receptor transport is required for chemokine degradation. Remarkably, the failure of ACKR3 R1423.50A to degrade CXCL11 was not caused by the lack of arrestin recruitment; rather, arrestin was entirely dispensable for scavenging of either chemokine. This suggests the involvement of another, yet unidentified, ACKR3 effector in scavenging. In summary, our study correlates ACKR3 ligand-specific conformational transitions with chemokine-dependent receptor transport dynamics and points toward unexpected ligand specificity in the mechanisms of chemokine degradation.

Mutational Analysis of Atypical Chemokine Receptor 3 (ACKR3/CXCR7) Interaction with Its Chemokine Ligands CXCL11 and CXCL12.

Atypical chemokine receptors do not mediate chemotaxis or G protein signaling, but they recruit arrestin. They also efficiently scavenge their chemokine ligands, thereby contributing to gradient maintenance and termination. ACKR3, also known as CXCR7, binds and degrades the constitutive chemokine CXCL12, which also binds the canonical receptor CXCR4, and CXCL11, which also binds CXCR3. Here we report comprehensive mutational analysis of the ACKR3 interaction with its chemokine ligands, using 30 substitution mutants. Readouts are radioligand binding competition, arrestin recruitment, and chemokine scavenging. Our results suggest different binding modes for both chemokines. CXCL11 depends on the ACKR3 N terminus and some extracellular loop (ECL) positions for primary binding, ECL residues mediate secondary binding and arrestin recruitment potency. CXCL12 binding required key residues Asp-1794.60 and Asp-2756.58 (residue numbering follows the Ballesteros-Weinstein scheme), with no evident involvement of N-terminal residues, suggesting an uncommon mode of receptor engagement. Mutation of residues corresponding to CRS2 in CXCR4 (positions Ser-1032.63 and Gln-3017.39) increased CXCL11 binding, but reduced CXCL12 affinity. Mutant Q301E7.39 did not recruit arrestin. Mutant K118A3.26 in ECL1 showed moderate baseline arrestin recruitment with ablation of ligand-induced responses. Substitutions that affected CXCL11 binding also diminished scavenging. However, detection of reduced CXCL12 scavenging by mutants with impaired CXCL12 affinity required drastically reduced receptor expression levels, suggesting that scavenging pathways can be saturated and that CXCL12 binding exceeds scavenging at higher receptor expression levels. Arrestin recruitment did not correlate with scavenging; although Q301E7.39 degraded chemokines in the absence of arrestin, S103D2.63 had reduced CXCL11 scavenging despite intact arrestin responses.

CXCL12-mediated feedback from granule neurons regulates generation and positioning of new neurons in the dentate gyrus.

Adult hippocampal neurogenesis is implicated in learning and memory processing. It is tightly controlled at several levels including progenitor proliferation as well as migration, differentiation and integration of new neurons. Hippocampal progenitors and immature neurons reside in the subgranular zone (SGZ) and are equipped with the CXCL12-receptor CXCR4 which contributes to defining the SGZ as neurogenic niche. The atypical CXCL12-receptor CXCR7 functions primarily by sequestering extracellular CXCL12 but whether CXCR7 is involved in adult neurogenesis has not been assessed. We report that granule neurons (GN) upregulate CXCL12 and CXCR7 during dentate gyrus maturation in the second postnatal week. To test whether GN-derived CXCL12 regulates neurogenesis and if neuronal CXCR7 receptors influence this process, we conditionally deleted Cxcl12 and Cxcr7 from the granule cell layer. Cxcl12 deletion resulted in lower numbers, increased dispersion and abnormal dendritic growth of immature GN and reduced neurogenesis. Cxcr7 ablation caused an increase in progenitor proliferation and progenitor numbers and reduced dispersion of immature GN. Thus, we provide a new mechanism where CXCL12-signals from GN prevent dispersion and support maturation of newborn GN. CXCR7 receptors of GN modulate the CXCL12-mediated feedback from GN to the neurogenic niche.

Emerging roles of atypical chemokine receptor 3 (ACKR3) in normal development and physiology.

The discovery that atypical chemokine receptors (ACKRs) can initiate alternative signaling pathways rather than classical G-protein coupled receptor (GPCR) signaling has changed the paradigm of chemokine receptors and their roles in modulating chemotactic responses. The ACKR family has grown over the years, with discovery of new functions and roles in a variety of pathophysiological conditions. However, the extent to which these receptors regulate normal physiology is still continuously expanding. In particular, atypical chemokine receptor 3 (ACKR3) has proven to be an important receptor in mediating normal biological functions, including cardiac development and migration of cortical neurons. In this review, we illustrate the versatile and intriguing role of ACKR3 in physiology.

Breast Cancer: An Examination of the Potential of ACKR3 to Modify the Response of CXCR4 to CXCL12.

Upon binding with the chemokine CXCL12, the chemokine receptor CXCR4 has been shown to promote breast cancer progression. This process, however, can be affected by the expression of the atypical chemokine receptor ACKR3. Given ACKR3's ability to form heterodimers with CXCR4, we investigated how dual expression of both receptors differed from their lone expression in terms of their signalling pathways. We created single and double CXCR4 and/or ACKR3 Chinese hamster ovary (CHO) cell transfectants. ERK and Akt phosphorylation after CXCL12 stimulation was assessed and correlated with receptor internalization. Functional consequences in cell migration and proliferation were determined through wound healing assays and calcium flux. Initial experiments showed that CXCR4 and ACKR3 were upregulated in primary breast cancer and that CXCR4 and ACKR3 could form heterodimers in transfected CHO cells. This co-expression modified CXCR4's Akt activation after CXCL12's stimulation but not ERK phosphorylation (p < 0.05). To assess this signalling disparity, receptor internalization was assessed and it was observed that ACKR3 was recycled to the surface whilst CXCR4 was degraded (p < 0.01), a process that could be partially inhibited with a proteasome inhibitor (p < 0.01). Internalization was also assessed with the ACKR3 agonist VUF11207, which caused both CXCR4 and ACKR3 to be degraded after internalization (p < 0.05 and p < 0.001), highlighting its potential as a dual targeting drug. Interestingly, we observed that CXCR4 but not ACKR3, activated calcium flux after CXCL12 stimulation (p < 0.05) and its co-expression could increase cellular migration (p < 0.01). These findings suggest that both receptors can signal through ERK and Akt pathways but co-expression can alter their kinetics and internalization pathways.

CXCR7 prevents excessive CXCL12-mediated downregulation of CXCR4 in migrating cortical interneurons.

The CXCL12/CXCR4 signaling pathway is involved in the development of numerous neuronal and non-neuronal structures. Recent work established that the atypical second CXCL12 receptor, CXCR7, is essential for the proper migration of interneuron precursors in the developing cerebral cortex. Two CXCR7-mediated functions were proposed in this process: direct modulation of ß-arrestin-mediated signaling cascades and CXCL12 scavenging to regulate local chemokine availability and ensure responsiveness of the CXCL12/CXCR4 pathway in interneurons. Neither of these functions has been proven in the embryonic brain. Here, we demonstrate that migrating interneurons efficiently sequester CXCL12 through CXCR7. CXCR7 ablation causes excessive phosphorylation and downregulation of CXCR4 throughout the cortex in mice expressing CXCL12, but not in CXCL12-deficient animals. Cxcl12(-/-) mice lack activated CXCR4 in embryonic brain lysates and display a similar interneuron positioning defect as Cxcr4(-/-), Cxcr7(-/-) and Cxcl12(-/-);Cxcr7(-/-) animals. Thus, CXCL12 is the only CXCR4-activating ligand in the embryonic brain and deletion of one of the CXCL12 receptors is sufficient to generate a migration phenotype that corresponds to the CXCL12-deficient pathway. Our findings imply that interfering with the CXCL12-scavenging activity of CXCR7 causes loss of CXCR4 function as a consequence of excessive CXCL12-mediated CXCR4 activation and degradation.

Dual targeting of the chemokine receptors CXCR4 and ACKR3 with novel engineered chemokines.

The chemokine CXCL12 and its G protein-coupled receptors CXCR4 and ACKR3 are implicated in cancer and inflammatory and autoimmune disorders and are targets of numerous antagonist discovery efforts. Here, we describe a series of novel, high affinity CXCL12-based modulators of CXCR4 and ACKR3 generated by selection of N-terminal CXCL12 phage libraries on live cells expressing the receptors. Twelve of 13 characterized CXCL12 variants are full CXCR4 antagonists, and four have Kd values <5 nm. The new variants also showed high affinity for ACKR3. The variant with the highest affinity for CXCR4, LGGG-CXCL12, showed efficacy in a murine model for multiple sclerosis, demonstrating translational potential. Molecular modeling was used to elucidate the structural basis of binding and antagonism of selected variants and to guide future designs. Together, this work represents an important step toward the development of therapeutics targeting CXCR4 and ACKR3.

Relationship between astrocyte damage and different levels of cerebrospinal fluid markers and prognosis in patients with subarachnoid hemorrhage.

INTRODUCTION: The aim of the study was to explore the relationship between astrocyte damage and different levels of cerebrospinal fluid markers and prognosis in patients with subarachnoid hemorrhage (SAH). MATERIAL AND METHODS: A total of 168 SAH patients diagnosed and treated in the emergency department of our hospital during the period October 2019 to February 2022 were randomly selected as the study subjects. The severity of these patients' condition was evaluated by Hunt-Hess grading and these subjects were graded as the low-level group (78 patients) and high-level group (90 patients) according to the evaluation results. The Extended Disability Status Scale (EDSS) score was employed to evaluate the astrocyte damage. The content of atypical chemokine receptor 3 (ACKR3), Connexin 43 (Cx43), oxygenated hemoglobin (HbO 2 ), and endothelin (ET) in cerebrospinal fluid was measured. The relationship between the content of ACKR3, Cx43, HbO 2 , and ET in cerebrospinal fluid with EDSS score was analyzed through Pearson correlation analysis. Multivariate logistic regression analysis was adopted to analyze the risk factors. RESULTS: ACKR3 was mainly expressed in the cytoplasm of cerebrospinal fluid monocytes, and Cx43 was mainly expressed in the cell membrane and cytoplasm. Patients in the high-level group had markedly higher expression rates of ACKR3 and Cx43 positive cells in cerebrospinal fluid than those in the low-level group ( p < 0.05). Patients in the high-level group had higher content of HbO 2 and ET in cerebrospinal fluid and EDSS score than patients in the low-level group ( p < 0.05). The content of ACKR3, Cx43, HbO 2 , and ET in cerebrospinal fluid of SAH patients was positively correlated with EDSS scores ( p < 0.05). Systolic blood pressure, Hunt-Hess grade, rebleeding, emotional control, EDSS score, ACKR3, Cx43 positive cell rate, and HbO 2 and ET expression levels were independent risk factors for the prognosis of SAH patients ( p < 0.05). CONCLUSIONS: Astrocyte damage in SAH patients was positively correlated with the content of ACKR3, Cx43, HbO 2 , and ET in cerebrospinal fluid. These indicators increased significantly with the increasing severity of the disease, and had certain value in reflecting the patient's condition. Astrocyte damage combined with cerebrospinal fluid markers had potential value in evaluating the severity and prognosis of patients.

Bilayer lipids modulate ligand binding to atypical chemokine receptor 3.

Chemokine receptors belong to the large class of G protein-coupled receptors (GPCRs) and are involved in a number of (patho)physiological processes. Previous studies highlighted the importance of membrane lipids for modulating GPCR structure and function. However, the underlying mechanisms of how lipids regulate GPCRs are often poorly understood. Here, we report that anionic lipid bilayers increase the binding affinity of the chemokine CXCL12 for the atypical chemokine receptor 3 (ACKR3) by modulating the CXCL12 binding kinetics. Notably, the anionic bilayer favors CXCL12 over the more positively charged chemokine CXCL11, which we explained by bilayer interactions orienting CXCL12 but not CXCL11 for productive ACKR3 binding. Furthermore, our data suggest a stabilization of active ACKR3 conformations in anionic bilayers. Taken together, the described regulation of chemokine selectivity of ACKR3 by the lipid bilayer proposes an extended version of the classical model of chemokine binding including the lipid environment of the receptor.

Crosstalk between CXCL12/CXCR4/ACKR3 and the STAT3 Pathway.

The reciprocal modulation between the CXCL12/CXCR4/ACKR3 axis and the STAT3 signaling pathway plays a crucial role in the progression of various diseases and neoplasms. Activation of the CXCL12/CXCR4/ACKR3 axis triggers the STAT3 pathway through multiple mechanisms, while the STAT3 pathway also regulates the expression of CXCL12. This review offers a thorough and systematic analysis of the reciprocal regulatory mechanisms between the CXCL12/CXCR4/ACKR3 signaling axis and the STAT3 signaling pathway in the context of diseases, particularly tumors. It explores the potential clinical applications in tumor treatment, highlighting possible therapeutic targets and novel strategies for targeted tumor therapy.