Identification of overlapping but differential binding sites for the high-affinity CXCR3 antagonists NBI-74330

ABSTRACT CXC chemokine receptor CXCR3 and/or its main three ligands CXCL9, CXCL10, and CXCL11 are highly upregulated in a variety of diseases. As such, considerable efforts have been made to develop small-molecule receptor CXCR3 antagonists, yielding distinct chemical classes of antagonists blocking binding and/or function of CXCR3 chemokines. Although it is suggested that these compounds bind in an allosteric fashion, thus far no evidence has been provided regarding the molecular details of their interaction with CXCR3. Using site-directed mutagenesis complemented with in silico homology modeling, we report the binding modes of two high-affinity CXCR3 antagonists of distinct chemotypes: Here we show that NBI-74330 is anchored in the transmembrane minor pocket lined by helices 2 (W2.60, D2.63), 3 (F3.32), and 7 (S7.39, Y7.43), whereas VUF11211 extends from the minor pocket into the major pocket of the transmembrane domains, located between residues in helices 1 (Y1.39), 2 (W2.60), 3 (F3.32), 4 (D4.60), 6 (Y6.51), and 7 (S7.39, Y7.43). Mutation of these residues did not affect CXCL11 binding significantly, confirming the allosteric nature of the interaction of these small molecules with CXCR3. Moreover, the model derived from our in silico-guided studies fits well with the already published structure-activity relationship data on these ligands. Altogether, in this study, we show overlapping, yet different binding sites for two high-affinity CXCR3 antagonists, which offer new opportunities for the structure-based design of allosteric modulators for CXCR3

Ubiquitination of CXCR7 Controls Receptor Trafficking

The chemokine receptor CXCR7 binds CXCL11 and CXCL12 with high affinity, chemokines that were previously thought to bind exclusively to CXCR4 and CXCR3, respectively. Expression of CXCR7 has been associated with cardiac development as well as with tumor growth and progression. Despite having all the canonical features of G protein-coupled receptors (GPCRs), the signalling pathways following CXCR7 activation remain controversial, since unlike typical chemokine receptors, CXCR7 fails to activate Gαi-proteins. CXCR7 has recently been shown to interact with β-arrestins and such interaction has been suggested to be responsible for G protein-independent signals through ERK-1/2 phosphorylation. Signal transduction by CXCR7 is controlled at the membrane by the process of GPCR trafficking. In the present study we investigated the regulatory processes triggered by CXCR7 activation as well as the molecular interactions that participate in such processes. We show that, CXCR7 internalizes and recycles back to the cell surface after agonist exposure, and that internalization is not only β-arrestin-mediated but also dependent on the Serine/Threonine residues at the C-terminus of the receptor. Furthermore we describe, for the first time, the constitutive ubiquitination of CXCR7. Such ubiquitination is a key modification responsible for the correct trafficking of CXCR7 from and to the plasma membrane. Moreover, we found that CXCR7 is reversibly de-ubiquitinated upon treatment with CXCL12. Finally, we have also identified the Lysine residues at the C-terminus of CXCR7 to be essential for receptor cell surface delivery. Together these data demonstrate the differential regulation of CXCR7 compared to the related CXCR3 and CXCR4 receptors, and highlight the importance of understanding the molecular determinants responsible for this process

Early mobilisation in critically ill COVID-19 patients: a subanalysis of the ESICM-initiated UNITE-COVID observational study

Background Early mobilisation (EM) is an intervention that may improve the outcome of critically ill patients. There is limited data on EM in COVID-19 patients and its use during the first pandemic wave. Methods This is a pre-planned subanalysis of the ESICM UNITE-COVID, an international multicenter observational study involving critically ill COVID-19 patients in the ICU between February 15th and May 15th, 2020. We analysed variables associated with the initiation of EM (within 72 h of ICU admission) and explored the impact of EM on mortality, ICU and hospital length of stay, as well as discharge location. Statistical analyses were done using (generalised) linear mixed-effect models and ANOVAs. Results Mobilisation data from 4190 patients from 280 ICUs in 45 countries were analysed. 1114 (26.6%) of these patients received mobilisation within 72 h after ICU admission; 3076 (73.4%) did not. In our analysis of factors associated with EM, mechanical ventilation at admission (OR 0.29; 95% CI 0.25, 0.35; p = 0.001), higher age (OR 0.99; 95% CI 0.98, 1.00; p ≤ 0.001), pre-existing asthma (OR 0.84; 95% CI 0.73, 0.98; p = 0.028), and pre-existing kidney disease (OR 0.84; 95% CI 0.71, 0.99; p = 0.036) were negatively associated with the initiation of EM. EM was associated with a higher chance of being discharged home (OR 1.31; 95% CI 1.08, 1.58; p = 0.007) but was not associated with length of stay in ICU (adj. difference 0.91 days; 95% CI − 0.47, 1.37, p = 0.34) and hospital (adj. difference 1.4 days; 95% CI − 0.62, 2.35, p = 0.24) or mortality (OR 0.88; 95% CI 0.7, 1.09, p = 0.24) when adjusted for covariates. Conclusions Our findings demonstrate that a quarter of COVID-19 patients received EM. There was no association found between EM in COVID-19 patients' ICU and hospital length of stay or mortality. However, EM in COVID-19 patients was associated with increased odds of being discharged home rather than to a care facility. Trial registration ClinicalTrials.gov: NCT04836065 (retrospectively registered April 8th 2021)

Online Versus Offline Peer Feedback in Higher Education: A Meta-Analysis

In recent years, the technical possibilities of educational technologies regarding online peer feedback have developed rapidly. However, the impact of online peer feedback activities compared to traditional offline variants has not specifically been meta-analyzed. Therefore, the aim of the current meta-analysis is to do an in-depth comparison between online versus offline peer feedback approaches. An earlier and broader meta-analysis focusing on technology-facilitated peer feedback in general, was used as a starting point. We synthesized 12 comparisons between online and offline peer feedback in higher education, from 10 different studies. Moreover, we reviewed student perceptions of online peer feedback when these were included in the studies. The results show that online peer feedback is more effective than offline peer feedback, with an effect size of 0.33. Moreover, online peer feedback is more effective when the outcome measure is competence rather than self-efficacy for skills. In addition, students are mostly positive towards online peer feedback but also list several downsides. Finally, implications for online peer feedback in teaching practice are discussed and leads are identified for further research on this topic

At-line coupling of LC-MS to bioaffinity and selectivity assessment for metabolic profiling of ligands towards chemokine receptors CXCR1 and CXCR2

This study describes an analytical method for bioaffinity and selectivity assessment of CXCR2 antagonists and their metabolites. The method is based on liquid chromatographic separation (LC) of metabolic mixtures followed by parallel mass spectrometry (MS) identification and bioaffinity determination. The bioaffinity is assessed using radioligand binding assays in 96-well plates after at-line nanofractionation. The described method was optimized for chemokines and low-molecular weight CXCR2 ligands. The limits of detection (LODs; injected amounts) for MK-7123, a high affinity binder to both CXCR1 and CXCR2 receptors belonging to the diaminocyclobutendione chemical class, were 40pmol in CXCR1 binding and 8pmol in CXCR2 binding. For CXCL8, the LOD was 5pmol in both binding assays. A control compound was always taken along with each bioassay plate as triplicate dose-response curve. For MK-7123, the calculated IC50 values were 314±59nM (CXCR1 binding) and 38±11nM (CXCR2 binding). For CXCL8, the IC50 values were 6.9±1.4nM (CXCR1 binding) and 2.7±1.3nM (CXCR2 binding). After optimization, the method was applied to the analysis of metabolic mixtures of eight LMW CXCR2 antagonists generated by incubation with pig liver microsomes. Moreover, metabolic profiling of the MK-7123 compound was described using the developed method. Three bioactive metabolites were found, two of which were (partially) identified. This method is suitable for bioaffinity and selectivity assessment of mixtures targeting the CXCR2. In contrary to conventional LC-MS based metabolic profiling studies done at the early lead discovery stage, additional qualitative bioactivity information of drug metabolites is obtained with the method described

Metabolic profiling of ligands for the chemokine receptor CXCR3 by liquid chromatography-mass spectrometry coupled to bioaffinity assessment

Chemokine receptors belong to the class of G protein-coupled receptors and are important in the host defense against infections and inflammation. However, aberrant chemokine signaling is linked to different disorders such as cancer, central nervous system and immune disorders, and viral infections [Scholten DJ et al. (2012) Br J Pharmacol 165(6):1617-1643]. Modulating the chemokine receptor function provides new ways of targeting specific diseases. Therefore, discovery and development of drugs targeting chemokine receptors have received considerable attention from the pharmaceutical industry in the past decade. Along with that, the determination of bioactivities of individual metabolites derived from lead compounds towards chemokine receptors is crucial for drug selectivity, pharmacodynamics, and potential toxicity issues. Therefore, advanced analytical methodologies are in high demand. This study is aimed at the optimization of a new analytical method for metabolic profiling with parallel bioaffinity assessment of CXCR3 ligands of the azaquinazolinone and piperazinyl-piperidine class and their metabolites. The method is based on mass spectrometric (MS) identification after liquid chromatographic (LC) separation of metabolic mixtures. The bioaffinity assessment is performed "at-line" via high-resolution nanofractionation onto 96-well plates allowing direct integration of radioligand binding assays. This new method enables identification of metabolites from lead compounds with associated estimation of their individual bioaffinity. Moreover, the identification of the metabolite structures via accurate mass measurements and MS(2) allows the identification of liable metabolic "hotspots" for further lead optimization. The efficient combination of chemokine receptor ligand binding assays with analytical techniques, involving nanofractionation as linking technology, allows implementation of comprehensive metabolic profiling in an early phase of the drug discovery process

Pharmacological characterization of [3H]VUF11211, a novel radiolabeled small-molecule inverse agonist for the chemokine receptor CXCR3

Chemokine receptor CXCR3 has attracted much attention, as it is thought to be associated with a wide range of immune-related diseases. As such, several small molecules with different chemical structures targeting CXCR3 have been discovered. Despite limited clinical success so far, these compounds serve as interesting tools for investigating receptor activation and antagonism. Accumulating evidence suggests that many of these compounds are allosteric modulators for CXCR3. One feature of allosteric ligands is that the magnitude of the mediated allosteric effect is dependent on the orthosteric probe that is used. Consequently, there is a risk for incorrect assessment of affinity for allosteric modulators with orthosteric radioligands, which has so far been the most applied approach for chemokine receptors. Therefore, we aimed to use a small-molecule allosteric ligand from the piperazinyl-piperidine class, also known as VUF11211 [(S)-5-chloro-6-(4-(1-(4-chlorobenzyl)piperidin-4-yl)-3-ethylpiperazin-1-yl)-N-ethylnicotinamide]. VUF11211 acts as an inverse agonist at a constitutively active mutant of CXCR3. Radiolabeling of VUF11211 gave [(3)H]VUF11211, which in radioligand binding studies shows high affinity for CXCR3 (Kd = 0.65 nM) and reasonably fast association (kon= 0.03 minute(-1)nM(-1)) and dissociation kinetics (koff = 0.02 minute(-1)). The application of the [(3)H]VUF11211 to assess CXCR3 pharmacology was validated with diverse classes of CXCR3 compounds, including both antagonists and agonists, as well as VUF11211 analogs. Interestingly, VUF11211 seems to bind to a different population of CXCR3 conformations compared with the CXCR3 agonists CXC chemokine ligand 11 (CXCL11), VUF11418 [1-((1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl)-N-((2'-iodobiphenyl-4-yl)methyl)-N,N-dimethylmethanaminium Iodide], and VUF10661 [N-(6-amino-1-(2,2-diphenylethylamino)-1-oxohexan-2-yl)-2-(4-oxo-4-phenylbutanoyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxamide]. These findings, taken together, indicate that this allosteric inverse agonist radioligand for CXCR3 may facilitate the discovery, characterization, and optimization of allosteric modulators for the chemokine receptor CXCR3

Practical Guidelines to Redesign Introductory Chemistry Courses Using a Flexible and Adaptive Blended Format

Incorporation of increased flexibility and adaptivity in courses can support freshmen with taking responsibility for their learning process. This is especially beneficial in the case of chemistry courses given their typically abstract nature and associated need for engaging in practice and higher order thinking. Blended learning can be used to achieve course flexibility and adaptivity, and increased student engagement. Adopting blended learning requires teachers to reconsider and redesign their course setup. The willingness for this will largely be dictated by perceived practicality, however. To this end, our aim is to develop practical redesign guidelines for flexible blended learning. Such guidelines need to be instrumental, congruent, and of 'low cost' for a teacher. The resulting four guidelines were fine-tuned in two phases over 5 years using two introductory chemistry courses and incorporated various blended learning elements, such as slide-cast lectures, live lectures, formative in-cast multiple choice questions, tutorials, formative electronic tutorial questions, and student voting on the course schedule. The outcome of our multiyear endeavor was positive and sustainable by all metrics used, including online engagement by students, learning outcomes, and student evaluations. The teachers in phase II largely embraced the guidelines emerging from phase I, and in their course experienced them predominantly as practical while limitations were also identified. We hope that our guidelines and experiences can provide fellow teachers with a blueprint for practical incorporation of flexibility and adaptivity using blended learning in their chemistry courses