Competitive Inhibitor Research Articles

Specific and potent inhibition of steroid hormone pre-receptor regulator AKR1C2 by perfluorooctanoic acid: Implications for androgen metabolism

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental pollutants that are highly stable synthetic organofluorine compounds. One congener perfluorooctanoic acid (PFOA) can be detected in nearly all humans and is recognized as an endocrine disrupting chemical (EDC). EDCs disrupt hormone synthesis and metabolism and receptor function. One mechanism of steroid hormone action is the pre-receptor regulation of ligand access to steroid hormone receptors by aldo-keto reductases. Here we report PFOA inhibition of AKR family 1 member C2 (AKR1C2), leading to dysregulation of androgen action. Spectrofluorimetric inhibitor screens identified PFOA as a competitive and tight binding inhibitor of AKR1C2, whose role is to inactivate 5α-dihydrotestosterone (5α-DHT). Further site directed mutagenesis studies along with molecular docking simulations revealed the importance of residue Valine 54 in mediating AKR1C2 inhibitor specificity. Binding site restrictions were explored by testing inhibition of other related PFAS chemicals, confirming that steric hinderance is a key factor. Furthermore, radiochromatography using HPLC and in line radiometric detection confirmed the accumulation of 5α-DHT as a result of PFOA inhibition of AKR1C2. We showed that PFOA could enhance the transactivation of AR in reporter genes assays in which 5α-DHT metabolism was blocked by AKR1C2 inhibition in HeLa cells. Taken together, these data suggest PFOA has a role in disrupting androgen action through inhibiting AKR1C2. Our work identifies an EDC function for PFOA not previously revealed.

Nanomolar Activity of Coumarin-3-thiosemicarbazones Targeting Trypanosoma cruzi Cruzain and T. brucei Cathepsin-L-like Protease

Trypanosoma cruzi (T. cruzi) and Trypanosoma brucei (T. brucei) urgently demand innovative drug development due to their impact on public health worldwide. Their cysteine proteases, Cruzain (CRZ) and T. brucei Cathepsin L-like protease (TbrCATL) are established drug targets for these parasites. In this study, our coumarin-3-thiosemicarbazones demonstrated nanomolar IC50 values (22-698 nM) toward these proteases. Against T. cruzi amastigotes and T. brucei trypomastigotes, LASF-01 displayed a promising result. Herein, MCG-02, the most potent TbrCATL inhibitor, underwent comprehensive analyses, including cytotoxicity assessments and in vitro tests. Molecular dynamics (MD) simulations and a multiscale Quantum Mechanics/Quantum Mechanics (QM/QM) approach were used to generate insights into their binding modes. These suggested that MCG-02 could be a reversible, competitive covalent inhibitor. Further, confirmatory assays were experimentally performed changing different parameters to prove its efficacy. Additionally, the predicted pharmacokinetic profile showed that there is no violation of the Lipinski rule of five. Notably, coumarin-3-thiosemicarbazone hybrids emerged as promising candidates for designing highly active inhibitors against CRZ and TbrCATL. Overall, the integration of in silico and experimental approaches enhanced our understanding regarding the binding modes of MCG-02, which were experimentally corroborated, providing valuable insights for future drug development.

Chaotic dynamics and optimal therapeutic strategies for Caputo fractional tumor immune model in combination therapy.

In this paper, a Caputo fractional tumor immune model of combination therapy is established. First, the stability and biological significance of each equilibrium point are analyzed, and it is demonstrated that chaos may arise under specific conditions. Combined with the mathematical definition of Caputo fractional differentiation (CFD), it is found that there is a high correlation between the chaotic phenomenon of the patient's condition and the sensitivity of the patient to the change in the state of the day. The bifurcation threshold of each parameter is determined through numerical simulation, and the Hopf bifurcation of direct competition coefficient and inhibition coefficient between tumor cells and host healthy cells is elaborated upon in detail. Subsequently, a novel method combining optimal control theory with the particle swarm optimization (PSO) algorithm is proposed for the optimal control of the tumor immune model in combination therapy. Finally, the Adams-Bashforth-Moulton (ABM) prediction correction method is utilized in numerical simulations which demonstrate that the introduction of the CFD alters the model dynamics. Furthermore, these results indicate that fractional calculus can effectively be applied to tumor immune models better to elucidate complex chaotic dynamics of tumor cell evolution. Concurrently, the PSO can be successfully integrated with optimal control theory to address optimization challenges in cancer treatment.

Imetelstat, a novel, first-in-class telomerase inhibitor: Mechanism of action, clinical, and translational science.

Most cancers and neoplastic progenitor cells have elevated telomerase activity and preservation of telomeres that promote cellular immortality, making telomerase a rational target for the treatment of cancer. Imetelstat is a first-in-class, 13-mer oligonucleotide that binds with high affinity to the template region of the RNA component of human telomerase and acts as a competitive inhibitor of human telomerase enzymatic activity. Pharmacokinetics, pharmacodynamics, exposure-response analyses, efficacy, and safety of imetelstat have been evaluated invitro, invivo, and clinically in solid tumor and hematologic malignancies, including lower-risk myelodysplastic syndromes (LR-MDS) and myeloproliferative neoplasms. Imetelstat was approved in the United States in June 2024 for the treatment of adult patients with LR-MDS with transfusion-dependent anemia requiring four or more red blood cell units over 8 weeks who have not responded to or have lost response to or are ineligible for erythropoiesis-stimulating agents, with a recommended dosing regimen of 7.1 mg/kg administered via 2-h intravenous infusion every 4 weeks. In the pivotal trial, significantly more patients treated with imetelstat versus placebo achieved ≥8-week and ≥24-week red blood cell-transfusion independence, and imetelstat was associated with a manageable safety profile characterized primarily by short-lived and manageable neutropenia and thrombocytopenia. This mini-review summarizes the mechanism of action, pharmacokinetic and pharmacodynamic characteristics, clinical development, and clinical efficacy and safety data of imetelstat.

Assessing plasmatic transport inhibitors of thyroid hormone in mammals in the Xenopus Eleutheroembryonic Thyroid Assay (XETA).

The Xenopus Eleutheroembryonic Thyroid Assay (XETA, OECD TG 248) was established as an alternative to the Amphibian Metamorphosis Assay (AMA, OECD TG 231) for the analysis of (anti-)thyroid activity of chemicals. The XETA is a New Approach Method (NAM) since the embryonic life stages used in the assay are not yet feeding independently, which renders the assay to be considered a non-animal test under many national laws. Physiologically, the used embryos are not fully developed yet, and thus there are limitations to the XETA for detecting certain mechanisms along the hypothalamic-pituitary-thyroid (HPT) axis. However, the plasmatic transport inhibition of thyroid hormone should physiologically be detectable in the XETA but has not yet been sufficiently investigated. Here, we tested three substances that are known, amongst others, to inhibit thyroid hormone transport by competitive binding to transthyretin in mammalian studies, namely pentachlorophenol (PCP), tetrabromo bisphenol A (TBBPA), and mefenamic acid. Following the test guideline, X. laevis eleutheroembryos of Nieuwkoop-Faber stage 45 were exposed for 72h at 21°C in 6-well plates to different concentrations of the test substances. For PCP and TBBPA, the XETA showed a decrease in fluorescence intensity, which would be expected for thyroid hormone transport inhibition amongst other, similar modes of action, while for the lower potency substance mefenamic acid, a trend was visible, but no statistically significant inhibition was detected. Overall, the results indicate that in the XETA, the plasmatic transport inhibition of thyroid hormone should be detectable alongside other inhibitory modes of action on the HPT axis.

WWOX tuning of oleic acid signaling orchestrates immunosuppressive macrophage polarization and sensitizes hepatocellular carcinoma to immunotherapy

BackgroundImmune checkpoint inhibitors (ICIs) are therapeutically effective for hepatocellular carcinoma (HCC) but are individually selective. This study examined the role of specific common fragile sites (CFSs) related gene in HCC...

A larval expressed chemosensory protein involved in recognition of anthocyanins in Spodoptera litura (Lepidoptera: Noctuidae).

Anthocyanins are secondary metabolites which act as diverse functions during plant growth. Insects can discriminate host plants by their sensitive gustatory systems. It is hypothetical that chemosensory proteins (CSPs) play a crucial role in regulating this behavioral process. However, the underlying molecular mechanisms remain obscure. In the present study, we characterized a CSP SlitCSP8 from the Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Quantitative real-time-polymerase chain reaction analysis demonstrated that SlitCSP8 was mainly expressed in the head of the 7th S. litura larvae, especially labrum. Further, recombinant SlitCSP8 was obtained using bacterial expression system. Fluorescence competitive binding assays demonstrated that the purified SlitCSP8 exhibited a strong binding affinity to anthocyanins, a natural compound derived from the host plant. Silencing SlitCSP8 through RNAi significantly reduced the sensitivity of S. litura larvae to anthocyanins-treated leaf disks, the development from larva to pupae was not affected. These data provide insight into the molecular basis that CSP8 can detect anthocyanins in host plants by chemosensory system of insects. It can be further used in designing novel optimal food attractant targeting to the CSPs for pest control.

Pharmacokinetic Model of Drug Interaction of Tacrolimus with Combined Administration of CYP3A4 Inhibitors Voriconazole and Clarithromycin After Bone Marrow Transplantation.

A pharmacokinetic model has been developed to quantify the drug-drug interactions of tacrolimus with concentration-dependent inhibition of cytochrome P450 (CYP) 3A4 from voriconazole and clarithromycin based on the CYP3A5 and CYP2C19 genotypes. This retrospective study recruited unrelated bone marrow transplant recipients receiving oral tacrolimus concomitantly with voriconazole and clarithromycin. The published population pharmacokinetic model that implemented genotypes of CYP3A5 (tacrolimus) and CYP2C19 (voriconazole) was integrated. The tested CYP3A4 inhibition models (Sigmoid efficacy maximum [Emax], Emax, log-linear, and linear) were a function of competitive inhibition of voriconazole and mechanism-based inhibition of clarithromycin in a virtual enzyme compartment. The total tacrolimus trough concentrations were 119 points, with a median of 4.3 (range: 2.0-9.9) ng/mL (n = 3). The final model comprised the Sigmoid Emax model for voriconazole and clarithromycin, which depicted time-course alterations in tacrolimus concentration and clearance when given voriconazole and clarithromycin. These findings could facilitate the model-informed precision dosing of tacrolimus after unrelated bone marrow transplant.

Competitive network of polyamines metabolic and ethylene biosynthesis pathways during gibberellin-induced parthenocarpic grape fruit setting

Polyamines (PAs) and ethylene are involved in the modulation of plant growth and development. However, their roles in fruit-set, especially in exogenous gibberellin (GA3)-induced grape parthenocarpic berries, and the related competitive action mode are poorly understood. For this, we, here performed their content determination, bioinformatics and expression pattern analysis of genes to identify the key ones in the competitive network of polyamines metabolic and ethylene biosynthesis (PMEB) pathways. The content of putrescine (Put) significantly increased; while 1-aminocyclopropanecarboxylic acid (ACC) sharply decreased during the fruit-set process of GA3-induced grape parthenocarpic seedless berries. Totally, twenty-five genes in PMEB pathways, including 20 polyamines metabolic (PM) genes and 5 ethylene biosynthesis (EB) ones were identified in grape, of which 8 PM and 2 EB genes possessed the motifs responsive to phytohormone GA. The expression levels of most PMEB genes kept changing during grape fruit-set generating a competitive action mode of GA3-mediated two metabolic fluxes toward PAs and ethylene synthesis. Exogenous GA3 might enhance grape fruit-set of parthenocarpic berries via up-regulation of VvSAMS4, VvSAMDC1/2, VvODC1, VvSPDS1, and VvPAO1 to promote PAs accumulation, whereby repressing the ethylene synthesis by down-regulation of VvACS1 and VvACO2. Our findings provide novel insights into GA3-mediated competitive inhibition of ethylene by PAs to promote the fruit-set of parthenocarpic berries in grape, which has important implications for molecular breeding of seedless grape with high fruit-setting rate.

A computational assay for identifying millet-derived compounds that antagonize the interaction between bisphenols and estrogen-related receptor gamma.

The use of Bisphenol A (BPA) and its analogs in industries, as well as the products made from them, is becoming a significant concern for human health. Scientific studies have revealed that BPA functions as an endocrine disruptor. While some analogs of BPA (bisphenols) have been used for a longer time, it was later discovered that they are toxic, similar to BPA. Their widespread use ensures their presence in the environment, and thus, everyone is exposed to them. Scientific research has shown that BPA interacts with estrogen-related receptor gamma (ERRγ), affecting its normal function. ERRγ is involved in biological processes including energy metabolism and mitochondrial function. Therefore, continuous exposure to bisphenols increases the risk of various diseases. In our previous study, we observed that some analogs of BPA had a higher binding affinity to ERRγ compared to BPA itself and analyzed the amino acid residues involved in this interaction. We hypothesized that by antagonizing the interaction between bisphenols and ERRγ, we could neutralize their toxic effects. Taking into account the health benefits of millets and their toxin removal properties, virtual screening of millet-derived compounds was conducted along with prediction of their ADMET profiles. Top five candidates were prioritized for Density Functional Theory (DFT) calculations and further analyses. Long-term molecular dynamics simulation (1µs) were utilized to evaluate their binding, stability, and antagonizing abilities. Furthermore, reevaluation of their binding energy was conducted using the MM-PBSA method. This study reports millet-derived compounds, namely, Tricin 7-rutinoside, Tricin 7-glucoside, Glucotricin, Kaempferol, and Setarin. These compounds are predicted to be potent competitive inhibitors that can antagonize the interactions between bisphenols and ERRγ. These compounds could potentially assist in the development of future therapeutics. They may also be considered for use as food supplements, although further investigations, including wet-lab experiments and clinical studies, are needed.

Recognition-Encoded Molecules: A Minimal Self-Replicator.

Nucleic acids, with their unique duplex structure, which is key for information replication, have sparked interest in self-replication's role in life's origins. Early template-based replicators, initially built on short oligonucleotides, expanded to include peptides and synthetic molecules. We explore here the potential of a class of synthetic duplex-forming oligoanilines, as self-replicators. We have recently developed oligoanilines equipped with 2-trifluoromethylphenol-phosphine oxide H-bond base pairs and we investigate whether the imine formed between aniline and aldehyde complementary monomers can self-replicate. Despite lacking a clear sigmoidal kinetic profile, control experiments with a methylated donor and a competitive inhibitor support self-replication. Further investigations with the reduced aniline dimer demonstrate templated synthesis, revealing a characteristic parabolic growth. After showing sequence selective duplex formation, templated synthesis and the emergence of catalytic function, the self-replication behaviour further suggests that the unique properties of nucleic acids can be paralleled by synthetic recognition-encoded molecules.

LncRNA HAGLROS: A Vital Oncogenic Propellant in Various Human Cancers.

HAGLR Opposite Strand lncRNA (HAGLROS) is a long non-coding RNA (lncRNA) located on the long arm of human chromosome 2 at locus 2q31.1. Emerging evidence highlights HAGLROS as a pivotal player in human cancers, characterized by its significant upregulation across multiple malignancies where it functions as an oncogenic driver. Its aberrant expression is closely linked to the initiation and progression of 13 distinct cancer types, notably correlating with adverse clinical outcomes and reduced overall survival rates in 9 of these cancer types. Mechanistically, HAGLROS is under the regulatory influence of the transcription factor STAT3, exerts competitive binding to 9 miRNAs, activates 5 signaling pathways pivotal for cancer cell proliferation and metastasis, as well as intricately modulates gene expression profiles. Given its multifaceted roles, HAGLROS emerges as a promising candidate for cancer diagnostics and prognostics. Moreover, its potential as a therapeutic target holds considerable promise for novel treatment strategies in oncology. This review synthesizes current research on HAGLROS, covering its expression patterns, biological roles, and clinical significance in cancer. By shedding light on these aspects, this review aims to contribute new perspectives that advance our understanding of cancer biology, enhance diagnostic accuracy, refine prognostic assessments, and pave the way for targeted therapeutic interventions.

Molecular Additives as Competitive Binding Agents to Control Supramolecular-Driven Nanoparticle Assembly

Molecular Additives as Competitive Binding Agents to Control Supramolecular-Driven Nanoparticle Assembly

Quorum sensing: the “switch” in the competitive relationship between Gram-positive bacteria based on transcriptomic analysis

Competition phenomenon is widely presented in nature, however, few reports on the competition phenomenon between bacteria based on the perspective of quorum sensing (QS), especially between Gram-positive bacteria. Here, the Gram-positive bacteria Rhodococcus sp. HD1 and Microbacterium sp. HM-2 were co-cultured, and the epiphysiological indicators, transcriptomics combined with gene engineering technique were applied to clarify the role of QS in the competition between Gram-positive bacteria. The results showed that the morphology of strain HD1 was changed into ellipsoids from long rods, the surface-to-volume ratio increased, and the competition index increased within strains HM-2 and HD1. The biomass of strain HD1(8.06×107 CFU/mL) was decreased significantly (p＜0.05) under co-culture system, compared with mono-culture (5.75×108 CFU/mL), indicating that strain HM-2 had an inhibitory effect on HD1 at 12 h. Transcriptomic analysis revealed that QS-related genes were highly expressed in strain HM-2, and the expression level of the virulence gene TM_0352 was the highest (FPKM: 1774.19). Meanwhile, the ABC transporters-related genes in strain HD1 were significantly increased. Furthermore, QS pathway-related genes in strain HM-2 and ABC transporters-related genes in strain HD1 showed a significant correlation with the gene TM_0352 expression by the Mantel test analysis (p<0.05), surmising that the TM_0352 gene played a dominant role in the co-culture system. Knockout and complementation experiments confirmed that the function of gene TM_0352. The structural equation model showed that the QS up-regulation of strain HM-2 significantly promoted the expression of virulence genes, while strain HD1 promoted ABC transporters to cope with the up-regulation of TM_0352. The up-regulation of TM_0352 promoted the biomass of strain HM-2 and inhibited the biomass of HD1.The above results displayed that the competition phenomenon appeared by QS driving the up-regulation of TM_0352 gene in strain HM-2, which led to the up-regulation of ABC transporters in strain HD1. And these findings provided new insights into the perspective of factors related to competition inhibition between bacteria.

Structure-function relationship of dynorphin B variants using naturally occurring amino acid substitutions.

Dynorphins (Dyn) represent the subset of endogenous opioid peptides with the highest binding affinity to kappa opioid receptors (KOPrs). Activation of the G-protein-coupled pathway of KOPrs has strong anticonvulsant effects. Dyn also bind to mu (MOPrs) and delta opioid receptors (DOPrs) with lower affinity and can activate the β-arrestin pathway. To fully exploit the therapeutic potential of dynorphins and reduce potential unwanted effects, increased selectivity for KOPrs combined with reduced activation of the mTOR complex would be favorable. Therefore, we investigated a series of dynorphin B (DynB) variants, substituted in one or two positions with naturally occurring amino acids for differential opioid receptor activation, applying competitive radio binding assays, GTPγS assays, PRESTO-Tango, and Western blotting on single-opioid receptor-expressing cells. Seven DynB derivatives displayed at least 10-fold increased selectivity for KOPrs over either MOPrs or DOPrs. The highest selectivity for KOPrs over MOPrs was obtained with DynB_G3M/Q8H, and the highest selectivity for KOPrs over DOPrs was obtained with DynB_L5S. Increased selectivity for KOPr over MOPr and DOPr was based on a loss of affinity or potency at MOPr and DOPr rather than a higher affinity or potency at KOPr. This suggests that the investigated amino acid exchanges in positions 3, 5, and 8 are of higher importance for binding and activation of MOPr or DOPr than of KOPr. In tests for signal transduction using the GTPγS assay, none of the DynB derivatives displayed increased potency. The three tested variants with substitutions of glycine to methionine in position 3 displayed reduced efficacy and are, therefore, considered partial agonists. The two most promising activating candidates were further investigated for functional selectivity between the G-protein and the β-arrestin pathway, as well as for activation of mTOR. No difference was detected in the respective read-outs, compared to wild-type DynB. Our data indicate that the assessment of affinity to KOPr alone is not sufficient to predict either potency or efficacy of peptidergic agonists on KOPr. Further assessment of downstream pathways is required to allow more reliable predictions of in vivo effects.

The efflux system CdfX exports zinc that cannot be transported by ZntA in Cupriavidus metallidurans.

Cupriavidus metallidurans is able to survive exposure to high concentrations of transition metals, but is also able to grow under metal starvation conditions. A prerequisite of cellular zinc homeostasis is a flow equilibrium combining zinc uptake and efflux processes. The mutant strain ∆e4 of the parental plasmid-free strain AE104 with a deletion of all four chromosomally encoded genes of previously known efflux systems ZntA, CadA, DmeF, and FieF was still able to efflux zinc in a pulse-chase experiment, indicating the existence of a fifth efflux system. The gene cdfX, encoding a protein of the cation diffusion facilitator (CDF) family, is located in proximity to the cadA gene, encoding a P-type ATPase. Deletion of cdfX in the ∆e4 mutant resulted in a further decrease in zinc resistance. Pulse-chase experiments with radioactive 65Zn(II) and stable-isotope-enriched 67Zn(II) provided evidence that CdfX was responsible for the residual zinc efflux activity of the mutant strain ∆e4. Reporter gene fusions with cdfX-lacZ indicated that the MerR-type regulator ZntR, the main regulator of zntA expression, was responsible for zinc- and cadmium-dependent upregulation of cdfX expression, especially in mutant cells lacking one or both of the previously characterized efflux systems, ZntA and CadA. Expression of zntR also proved to be controlled by ZntR itself as well as by zinc and cadmium availability. These data indicate that the cdfX-cadA region provides C. metallidurans with a backup system for the zinc-cadmium-exporting P-type ATPase ZntA, with CdfX exporting zinc and CadA cadmium.IMPORTANCEBacteria have evolved the ability to supply the important trace element zinc to zinc-dependent proteins, despite external zinc concentrations varying over a wide range. Zinc homeostasis can be understood as adaptive layering of homeostatic systems, allowing coverage from extreme starvation to extreme resistance. Central to zinc homeostasis is a flow equilibrium of zinc comprising uptake and efflux reactions, which adjusts the cytoplasmic zinc content. This report describes what happens when an imbalance in zinc and cadmium concentrations impairs the central inner-membrane zinc efflux system for zinc by competitive inhibition for this exporter. The problem is solved by activation of Cd-exporting CadA or Zn-exporting CdfX as additional efflux systems.

Exploring the competitive inhibition of α-glucosidase by citrus pectin enzymatic hydrolysate and its mechanism: An integrated experimental and simulation approach

The endo-polygalacturonase D (PgaD) from Aspergillus niger JL15 was recombinantly expressed in Escherichia coli BL21, exhibiting an optimal activity at 55 °C and pH 4.0. Hydrolysis products of citrus pectin by recombinant PgaD included galacturonic acid (GalA), digalacturonic acid (GalA2), trigalacturonic acid (GalA3), and tetragalacturonic acid (GalA4). The hydrolysates exhibited significant antioxidant capacity and dose-dependent competitive inhibition of α-glucosidase. GalA2 and GalA3 acted as competitive inhibitors of α-glucosidase, with inhibition constant of 0.0589 mmol.L−1 and 0.6732 mmol.L−1, respectively. Molecular dynamics (MD) simulations revealed that both GalA2 and GalA3 penetrated the catalytic pocket of α-glucosidase and formed stable hydrogen bonds with key catalytic residues D352 and D215. The binding free energies of GalA2-α-glucosidase and GalA3-α-glucosidase complexes were − 10.3 ± 0.6 kcal·mol−1 and -10.8 ± 0.7 kcal·mol−1, respectively. These findings might offer new ideas for the development of α-glucosidase inhibitors sourced from citrus pectin, as well as enhance utilization of the renewable plant polysaccharide resources.

Humoral Immunity Profiling to Pandemic and Bat‐Derived Coronavirus Variants: A Geographical Comparison

AbstractDynamic pathogen exposure may impact the immunological response to SARS‐CoV‐2 (SCV2). One potential explanation for the lack of severe SCV2‐related morbidity and mortality in Southeast Asia is prior exposure to related betacoronaviruses. Recent discoveries of SCV2‐related betacoronaviruses from horseshoe bats (Rhinolophus sinicus) in Thailand, Laos, and Cambodia suggest the potential for bat‐to‐human spillover exposures in the region. In this work, serum antibodies to protein constructs from SCV2 and a representative bat coronavirus isolated in Cambodia (RshSTT182) are measured in pre‐pandemic Cambodian human sera using ELISA assays. Of 293 Cambodian samples tested (N = 131 with acute malaria, n = 162 with acute undifferentiated febrile illness), 32 (10.9%) are seropositive for SCV2 based on established Spike and receptor‐binding domain (RBD) cutoffs. Within SCV2 seropositive samples, 16 (50%) have higher antibody levels to antigens from the representative virus RshSTT182 versus SCV2 antigens; competitive binding ELISA assays demonstrate inhibition of reactivity to SCV2 Spike after pre‐incubation with RshSTT182 Spike. Surrogate virus neutralization tests demonstrate that 8/30 (26.7%) SCV2 ELISA positive pre‐pandemic Cambodian samples have neutralizing activity against SCV2, while 14/30 (46.7%) have activity against other SCV2‐related betacoronaviruses. These data suggest that exposure to related betacoronaviruses may elicit cross‐reactive immunity to SCV2 prior to the global pandemic.

Exploring Arylidene-Indolinone Ligands of Autophagy Proteins LC3B and GABARAP.

We report the first structure-activity studies of arylidene-indolinone compound GW5074 which was reported as a ligand of autophagy-related protein LC3B. The literature has conflicting information on the binding affinity of this compound and there is some debate regarding its use as a component of autophagy-dependent degrader compounds. We developed an AlphaScreen assay to measure competitive inhibition of the binding of known peptide ligands to LC3B and its paralog GABARAP. 18 analogs were synthesized and tested against both proteins. Inhibitory potencies were found to be in the mid- to high micromolar range. 2D-NMR data revealed the binding site on GABARAP as hydrophobic pocket 1, where native peptide ligands bind with an aromatic side chain. Our results suggest that GW5074 binds LC3B and GABARAP with micromolar affinity. These affinities could support further exploration in targeted protein degradation, but only if off-target effects and poor solubility can be appropriately addressed.

Design, synthesis, QSAR modelling and molecular dynamic simulations of N-tosyl-indole hybrid thiosemicarbazones as competitive tyrosinase inhibitors

Tyrosinase is an enzyme crucial for the progression of melanogenesis. Immoderate production of melanin may be the cause of hyperpigmentation and darkening leading to skin diseases. Tyrosinase is the most researched target for suppressing melanogenesis since it catalyzes the rate-limiting stage of melanin production. Thiosemicarbazones have been reported to possess strong inhibition capability against tyrosinase. We have designed and synthesized eighteen N-tosyl substituted indole-based thiosemicarbazones as competitive tyrosinase inhibitors in the current work. All the compounds exhibited outstanding to good potency with half maximal inhibitory concentration in the range of 6.40 ± 0.21 µM to 61.84 ± 1.47 µM. The compound 5r displayed the top-tier inhibition amongst the entire series with IC50 = 6.40 ± 0.21 µM. Compounds, 5q and 5r exhibited competitive inhibitions in concentration dependent manner with Ki = 3.42 ± 0.03 and 10.25 ± 0.08 µM respectively. The binding mode of 5r was evaluated through in silico molecular dynamics simulations and molecular docking, while ADME assessment studies predicted the drug-like characteristics of the derivatives. The newly synthesized derivatives may serve as a structural guide for designing and developing novel tyrosinase inhibitors.