Fluorescence Resonance Energy Transfer Assay Research Articles

Isolation, Virtual Screening, and Evaluation of Hazelnut-Derived Immunoactive Peptides for the Inhibition of SARS-CoV-2 Main Protease.

The aim of this study is to validate the activity of hazelnut (Corylus avellana L.)-derived immunoactive peptides inhibiting the main protease (Mpro) of SARS-CoV-2 and further unveil their interaction mechanism using in vitro assays, molecular dynamics (MD) simulations, and binding free energy calculations. In general, the enzymatic hydrolysis components, especially molecular weight < 3 kDa, possess good immune activity as measured by the proliferation ability of mouse splenic lymphocytes and phagocytic activity of mouse peritoneal macrophages. Over 866 unique peptide sequences were isolated, purified, and then identified by nanohigh-performance liquid chromatography/tandem mass spectrometry (NANO-HPLC-MS/MS) from hazelnut protein hydrolysates, but Trp-Trp-Asn-Leu-Asn (WWNLN) and Trp-Ala-Val-Leu-Lys (WAVLK) in particular are found to increase the cell viability and phagocytic capacity of RAW264.7 macrophages as well as promote the secretion of the cytokines nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). Fluorescence resonance energy transfer assay elucidated that WWNLN and WAVLK exhibit excellent inhibitory potency against Mpro, with IC50 values of 6.695 and 16.750 μM, respectively. Classical all-atom MD simulations show that hydrogen bonds play a pivotal role in stabilizing the complex conformation and protein-peptide interaction. Molecular Mechanics/Generalized Born Surface Area (MM/GBSA) calculation indicates that WWNLN has a lower binding free energy with Mpro than WAVLK. Furthermore, adsorption, distribution, metabolism, excretion, and toxicity (ADMET) predictions illustrate favorable drug-likeness and pharmacokinetic properties of WWNLN compared to WAVLK. This study provides a new understanding of the immunomodulatory activity of hazelnut hydrolysates and sheds light on peptide inhibitors targeting Mpro.

Relative biomembrane fusogenicities of the tumor-selective liposomes of RGDK- and CGKRK-lipopeptides.

Cancer is the second leading cause of death globally after heart diseases. Currently used highly cytotoxic anti-cancer drugs not only kill cancer cells but also often kill non-cancerous healthy body cells, causing adverse side effects. Efforts are now being directed towards developing tumor-selective chemotherapy. Tumor/tumor endothelial cell selective peptide ligands are being covalently grafted onto the exo-surfaces of drug carriers such as liposomes, polymers, etc. A number of prior studies used conjugation of tumor/tumor endothelial cell-selective RGDK- or CGKRK-peptide ligands on the outer surfaces of liposomes, metal-based nanoparticles, single walled carbon nanotubes (SWNTs), etc. However, studies aimed at examining the relative cell membrane fusogenicities and the relative degrees of cellular uptake for the RGDK- and CGKRK-ligand-grafted nanometric drug carriers have not yet been undertaken. Herein, using the widely used liposomes of DOPC, DOPE, DOPS and cholesterol (45 : 25 : 20 : 15, w/w ratio) as the model biomembranes and the fluorescence resonance energy transfer (FRET) assay for measuring membrane fusogenicities, we show that the liposomes of the RGDK-lipopeptide are more biomembrane fusogenic than the liposomes of the CGKRK-lipopeptide. Notably, such FRET assay-derived relative biomembrane fusogenicities of the liposomes of RGDK- and CGKRK-lipopeptides were found to be consistent with their relative degrees of cellular uptake in cultured cancer cells. The present findings open the door for undertaking in-depth in vivo studies aimed at evaluating the relative therapeutic potential of different nanocarriers of drugs/genes/siRNA having tumor-targeting RGDK- and CGKRK-peptides on their exo-surfaces.

Fraxetin Targeting to Sortase A Decreases the Pathogenicity of Streptococcus agalactiae to Nile Tilapia.

Sortase A (SrtA) is responsible for anchoring surface proteins to the cell wall, and has been identified as a promising target developing anti-infective drugs of Gram-positive bacteria. The aim of the study was to identify inhibitors of Streptococcus agalactiae (S. agalactiae) SrtA from natural compounds to overcome the spread of antibiotic resistance in aquaculture. Here, we found that the MIC of fraxetin against S. agalactiae was higher than 256 μg/mL, indicating that fraxetin had no anti- S. agalactiae activity. But fraxetin could dose-dependently decrease the activity of SrtA in vitro at concentrations ranging between 4-32 μg/mL by a fluorescence resonance energy transfer (FRET) assay. Moreover, the inhibition of SrtA by fraxetin decreased the anchoring of surface proteins with the LPXTG motif to the cell wall by detecting the immunofluorescence change of serine-rich repeat protein 1 (Srr1) on the bacterial cell surface. The results of fibronectin binding and cell adhesion assays indicated that fraxetin could significantly decrease the adhesion ability of S. agalactiae in a dose-dependent manner. The results were further proven by immunofluorescence staining. Animal challenge results showed that treatment with fraxetin could reduce the mortality of tilapia infected with S. agalactiae to 46.67%, indicating that fraxetin could provide a significant amount of protection to tilapia by inactivating SrtA. Taken together, these findings provided a novel inhibitor of S. agalactiae SrtA and a promising candidate for treating S. agalactiae infections in aquaculture.

Abstract LB021: BAU-243: A novel BCL-2 inhibitor inducing autophagic cell death in glioblastoma, unveiled through multistep virtual screening, comprehensive in vitro and in vivo animal model evaluation

Abstract The excessive expression of antiapoptotic members in the B-cell leukemia/lymphoma-2 (BCL-2) family proteins emerges as a noteworthy oncogenic target in cancer cells. Employing a multistep virtual screening and filtering approach that integrates structure and ligand-based drug design, we aimed to identify novel and potent BCL-2 inhibitors from a sizable small molecule database, comprising over 210,000 compounds. Subsequently, seven selected molecules underwent rigorous biological activity tests in human cancer cell lines and Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) assays. Four of these compounds exhibited notable inhibitory effects on cancer cell proliferation and led to an increase in apoptotic cell fractions. Among the identified compounds, BAU-243 displayed a substantial affinity for Bcl-2, demonstrating efficacy in reducing glioblastoma (GBM) cell proliferation, including cancer-initiating cells. Notably, in contrast to the selective Bcl-2 inhibitor ABT-199, BAU-243 induced autophagic cell death in GBM cells. In vivo investigations using orthotopic brain tumor models revealed a significant reduction in tumor growth with BAU-243 compared to both the vehicle group and animals treated with ABT-199. Computational modeling simulations, in concordance with in vitro findings, proposed that BAU-243 activates autophagic cell death by disrupting the Beclin 1:Bcl-2 complex. This positions BAU-243 as a promising small molecule for the treatment of GBM. Citation Format: Seyma Calis, Berna Dogan, Asuman Celebi, Ozlem Yapicier, Turker Kilic, Eda Tahir Turanli, Timucin Avsar, Serdar Durdagi. BAU-243: A novel BCL-2 inhibitor inducing autophagic cell death in glioblastoma, unveiled through multistep virtual screening, comprehensive in vitro and in vivo animal model evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB021.

427 Defining the Impact of the Fecal Microbiome and Secretome on Multiple System Atrophy and α-Synuclein Aggregation

OBJECTIVES/GOALS: Aim 1: We will determine whether temporal changes in the fecal microbiome signature correlate with a clinical multiple system atrophy (MSA) phenotype. Aim 2: We will evaluate whether secretomes cultured from fecal samples from MSA patients enhance intracellular and extracellular α-synuclein (αSyn) aggregation using in vitro functional assays. METHODS/STUDY POPULATION: Aim 1: Gut microbiome profiling will be performed by 16S rRNA gene sequencing, tandem mass spectrometry for expression proteomics, and targeted metabolomics in fecal samples from 30 MSA cases matched to 30 healthy controls, a Parkinson’s disease comparison group, and household controls. Aim 2: Microbial species will be isolated using dilution-to-extinction on MSA fecal samples and then will be cultured to obtain secretomes. To assess the effect of MSA fecal secretomes on αSyn aggregation, culture media from microbial isolates will be used in fluorescence resonance energy transfer (FRET) assays and luciferase reporter assays, both modified to measure αSyn aggregation. Positive tests will undergo expanded metagenomic characterization of the microbes and secretome to identify potential causative agent(s). RESULTS/ANTICIPATED RESULTS: Based on cross-sectional metagenomic studies on MSA, MSA cases are expected to have genus reductions in Blautia and Dorea (acetate production); Paraprevotella (succinic and acetic acid production); and Ruminococcus, Coprococcus, and Faecalibacterium (butyrate production). Increases in genus Bacteroides (clinical pathogen) and Akkermansia (mucin degradation) and pro-inflammatory families Clostridiaceae and Rikenellaceae are also expected. MSA is predicted to be associated with reduced levels of short chain fatty acids and increased lipopolysaccharide. These microbial proteins and metabolites are anticipated to modulate intracellular and extracellular αSyn aggregation in vitro. Microbe isolation and secretome culturing methods are expected to identify additional drivers of αSyn aggregation. DISCUSSION/SIGNIFICANCE: This study’s novel use of longitudinal sampling, household controls, and secretome culturing aim to develop a more comprehensive understanding of the complex interactions between the gut microbiome and MSA. The success of this work offers the potential for new insights into the impact of the gut microbiome and secretome on MSA and αSyn aggregation.

Abstract 192: Orchestrating CDC42 turnover to regulate membrane protrusion and tumor metastasis

Abstract F-actin cytoskeleton remodeling is essential for cell migration, organ development, and immune responses. CDC42, a factor orchestrating F-actin remodeling for membrane dynamics, switches between its inactive GDP- and active GTP-bound forms. However, the biological and clinical significance of the mechanisms regulating CDC42 protein turnover remains unclear. Here we show that KLHL23-mediated CDC42·GTP polyubiquitylation for degradation and RhoGDI-mediated CDC42·GDP sequestration away from the plasma membrane co-inactivate CDC42 in a spatiotemporal context, influencing membrane dynamics and homeostasis during migration. Via a functional genomic screen, we identified KLHL23 as a suppressor of tumor invasion. Decreased KLHL23 level was associated with tumor metastasis and poor clinical outcomes in patients with liver and pancreas cancers. KLHL23 functions as the E3 ligase responsible for CDC42 polyubiquitylation and degradation. KLHL23 shares with RhoGDI the switch II region of CDC42 for binding, enhancing selective targeting of CDC42·GTP and CDC42·GDP, respectively. KLHL23 depletion in cells leads to F-actin and membrane over-protrusion, as well as epithelial-mesenchymal transition and tumor metastasis. Fluorescence resonance energy transfer assays reveal that the KLHL23—CDC42·GTP interaction plays a primary role in quenching CDC42 activity during membrane protrusion-retraction, while the RhoGDI—CDC42·GDP interaction occurs lately. Our results demonstrate the spatiotemporal interplay between RhoGDI and KLHL23 in regulating CDC42 turnover for membrane dynamics. As KLHL23/RhoGDI—CDC42 axis dysregulation causes tumor metastasis, our findings open avenues for exploring novel therapeutics. Citation Format: Sen-Yung Hsieh. Orchestrating CDC42 turnover to regulate membrane protrusion and tumor metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 192.

Overview of ADAMTS13 Protein in Diagnosis and Patient Management of TTP

The accurate diagnosis and effective management of Thrombotic Thrombocytopenic Purpura (TTP), a rare but life-threatening hematologic disorder, rely critically on the assessment of ADAMTS13 activity. ADAMTS13, a von Willebrand factor-cleaving protease, plays a pivotal role in the pathophysiology of TTP. This review synthesizes current understanding and recent advancements in the role of ADAMTS13 in the diagnosis and therapeutic monitoring of TTP, with a specific focus on the implementation of a fluorescence resonance energy transfer (FRET)-based assay for ADAMTS13 activity. Our retrospective analysis of 50 suspected TTP cases, including 19 confirmed diagnoses, revealed that the FRET-based assay significantly improved the sensitivity and specificity of TTP diagnosis compared to traditional qualitative methods. Furthermore, the FRET assay facilitated timely initiation of appropriate therapies and monitoring of disease activity, underscoring its utility in clinical practice. Our findings highlight the FRET-based ADAMTS13 activity assay's contribution to enhancing the diagnostic accuracy and management efficiency of TTP, suggesting its potential as a standard diagnostic tool in clinical settings. The review aims to provide a comprehensive overview for hematologists and laboratory medicine practitioners, encouraging the adoption of the FRET-based assay to improve patient outcomes in TTP management.

YAP upregulates AMPKα1 to induce cancer cell senescence

Yes-associated protein (YAP)—a major effector protein of the Hippo pathway— regulates cell proliferation, differentiation, apoptosis, and senescence. Amp-activated protein kinase (AMPK) is a key sensor that monitors cellular nutrient supply and energy status. Although YAP and AMPK are considered to regulate cellular senescence, it is still unclear whether AMPK is involved in YAP-regulated cellular senescence. Here, we found that YAP promoted AMPKα1 aggregation and localization around mitochondria by co-transfecting CFP-YAP and YFP-AMPKα1 plasmids. Subsequent live cell fluorescence resonance energy transfer (FRET) assay did not exhibit direct interaction between YAP and AMPKα1. FRET, Co-immunoprecipitation, and western blot experiments revealed that YAP directly bound to TEAD, enhancing the expression of AMPKα1 and p-AMPKα. Treatment with verteporfin inhibited YAP’s binding to TEAD and reversed the elevated expression of AMPKα1 in the cells overexpressing CFP-YAP. Verteporfin also reduced the proportion of AMPKα1 puncta in the cells co-expressing CFP-YAP and YFP-AMPKα1. In addition, the AMPKα1 puncta were demonstrated to inhibit cell viability, autophagy, and proliferation, and ultimately promote cell senescence. In conclusion, YAP binds to TEAD to upregulate AMPKα1 and promotes the formation of AMPKα1 puncta around mitochondria under the condition of co-expression of CFP-YAP and YFP-AMPKα1, in which AMPKα1 puncta lead to cellular senescence.

Different Coactivator Recruitment to Human PPARα/δ/γ Ligand-Binding Domains by Eight PPAR Agonists to Treat Nonalcoholic Fatty Liver Disease.

Three peroxisome proliferator-activated receptor subtypes, PPARα, PPAR(ß/)δ, and PPARγ, exert ligand-dependent transcriptional control in concert with retinoid X receptors (RXRs) on various gene sets harboring PPAR response elements (PPREs) in their promoter regions. Ligand-bound PPAR/RXR complexes do not directly regulate transcription; instead, they recruit multiprotein coactivator complexes to specific genomic regulatory loci to cooperatively activate gene transcription. Several coactivators are expressed in a single cell; however, a ligand-bound PPAR can be associated with only one coactivator through a consensus LXXLL motif. Therefore, altered gene transcription induced by PPAR subtypes/agonists may be attributed to the recruitment of various coactivator species. Using a time-resolved fluorescence resonance energy transfer assay, we analyzed the recruitment of four coactivator peptides (PGC1α, CBP, SRC1, and TRAP220) to human PPARα/δ/γ-ligand-binding domains (LBDs) using eight PPAR dual/pan agonists (bezafibrate, fenofibric acid, pemafibrate, pioglitazone, elafibranor, lanifibranor, saroglitazar, and seladelpar) that are/were anticipated to treat nonalcoholic fatty liver disease. These agonists all recruited four coactivators to PPARα/γ-LBD with varying potencies and efficacy. Only five agonists (bezafibrate, pemafibrate, elafibranor, lanifibranor, and seladelpar) recruited all four coactivators to PPARδ-LBD, and their concentration-dependent responses differed from those of PPARα/γ-LBD. These results indicate that altered gene expression through consensus PPREs by different PPAR subtypes/agonists may be caused, in part, by different coactivators, which may be responsible for the unique pharmacological properties of these PPAR agonists.

Discovery of 5-aminopyrido[2,3-d]pyrimidin-7(8H)-one derivatives as new hematopoietic progenitor kinase 1 (HPK1) inhibitors

Hematopoietic progenitor kinase 1 (HPK1) is a negative regulator of T-cell receptor signaling. While HPK1 is considered as a promising target for cancer immunotherapy, no small-molecule HPK1 inhibitors have been approved for cancer treatment. Herein, we report the discovery of a series of new HPK1 inhibitors with a 5-aminopyrido[2,3-d]pyrimidin-7(8H)-one scaffold. The most potent compound 9f inhibited HPK1 kinase activity with an IC50 of 0.32 nM in the time-resolved fluorescence resonance energy transfer (TR-FRET) assays, while displayed reasonable selectivity in a panel of 416 kinases. Cellular engagement of HPK1 by compound 9f was confirmed through the nano-bioluminescence resonance energy transfer (Nano-BRET) experiments. Compound 9f effectively reduced the phosphorylation of the downstream protein SLP-76 in primary peripheral blood mononuclear cells (PBMCs) and human T lymphocytic leukemia Jurkat cells. Compound 9f also enhanced the IL-2 and IFN-γ secretion in PBMCs. Furthermore, the binding mode of compound 9f with HPK1 was confirmed by the resolved cocrystal structure. Taken together, this study provides HPK1 inhibitors with a novel scaffold and clear binding mode for further development of HPK1-targeted therapeutic agents.

Inhibition of NS2B-NS3 protease from all four serotypes of dengue virus by punicalagin, punicalin and ellagic acid identified from Punica granatum

Despite a major threat to the public health in tropical and subtropical regions, dengue virus (DENV) infections are untreatable. Therefore, efforts are needed to investigate cost-effective therapeutic agents that could cure DENV infections in future. The NS2B-NS3 protease encoded by the genome of DENV is considered a critical target for the development of anti-dengue drugs. The objective of the current study was to find out a specific inhibitor of the NS2B-NS3 proteases from all four serotypes of DENV. To begin with, nine plant extracts with a medicinal history were evaluated for their role in inhibiting the NS2B-NS3 proteases by Fluorescence Resonance Energy Transfer (FRET) assay. Among the tested extracts, Punica granatum was found to be the most effective one. The metabolic profiling of this extract revealed the presence of several active compounds, including ellagic acid, punicalin and punicalagin, which are well-established antiviral agents. Further evaluation of IC50 values of these three antiviral molecules revealed punicalagin as the most potent anti-NS2B-NS3 protease drug with IC50 of 0.91 ± 0.10, 0.75 ± 0.05, 0.42 ± 0.03, 1.80 ± 0.16 µM against proteases from serotypes 1, 2, 3 and 4, respectively. The docking studies demonstrated that these compounds interacted at the active site of the enzyme, mainly with His and Ser residues. Molecular dynamics simulations analysis also showed the structural stability of the NS2B-NS3 proteases in the presence of punicalagin. In summary, this study concludes that the punicalagin can act as an effective inhibitor against NS2B-NS3 proteases from all four serotypes of DENV. Communicated by Ramaswamy H. Sarma

Identification of SARS-CoV-2 Main Protease Inhibitors Using Chemical Similarity Analysis Combined with Machine Learning.

SARS-CoV-2 Main Protease (Mpro) is an enzyme that cleaves viral polyproteins translated from the viral genome, which is critical for viral replication. Mpro is a target for anti-SARS-CoV-2 drug development. Herein, we performed a large-scale virtual screening by comparing multiple structural descriptors of reference molecules with reported anti-coronavirus activity against a library with >17 million compounds. Further filtering, performed by applying two machine learning algorithms, identified eighteen computational hits as anti-SARS-CoV-2 compounds with high structural diversity and drug-like properties. The activities of twelve compounds on Mpro's enzymatic activity were evaluated by fluorescence resonance energy transfer (FRET) assays. Compound 13 (ZINC13878776) significantly inhibited SARS-CoV-2 Mpro activity and was employed as a reference for an experimentally hit expansion. The structural analogues 13a (ZINC4248385), 13b (ZNC13523222), and 13c (ZINC4248365) were tested as Mpro inhibitors, reducing the enzymatic activity of recombinant Mpro with potency as follows: 13c > 13 > 13b > 13a. Then, their anti-SARS-CoV-2 activities were evaluated in plaque reduction assays using Vero CCL81 cells. Subtoxic concentrations of compounds 13a, 13c, and 13b displayed in vitro antiviral activity with IC50 in the mid micromolar range. Compounds 13a-c could become lead compounds for the development of new Mpro inhibitors with improved activity against anti-SARS-CoV-2.

Evaluation of natural products from virtual screenings as SARS-CoV-2 main protease inhibitors using combinational experiments

Recently, andrographolide, kaempferol, maslinic acid, rutin, and schaftoside have been identified as potent SARS-CoV-2 main protease (Mpro) inhibitors via molecular docking studies. However, no comprehensive in vitro testing of these compounds against Mpro has been conducted. In this study, we rigorously evaluated the in vitro inhibition of Mpro by these compounds using combinational experiments, including fluorescence resonance energy transfer (FRET), fluorescence polarization (FP), and dimerization-dependent red fluorescent protein (ddRFP) assays. Our data revealed that these compounds are not Mpro inhibitors based on the results from a set of in vitro assays. These results suggest that an efficient combination of a molecular docking approach and an experimental assay is essential for the discovery of Mpro inhibitors in the future.

KRAS4b:RAF-1 Homogenous Time-Resolved Fluorescence Resonance Energy Transfer Assay for Drug Discovery.

Homogenous time-resolved FRET (HTRF) assays have become one of the most popular tools for pharmaceutical drug screening efforts over the last two decades. Large Stokes shifts and long fluorescent lifetimes of lanthanide chelates lead to robust signal to noise, as well as decreased false positive rates compared to traditional assay techniques. In this chapter, we describe an HTRF protein-protein interaction (PPI) assay for the KRAS4b G-domain in the GppNHp-bound state and the RAF-1-RBD currently used for drug screens. Application of this assay contributes to the identification of lead compounds targeting the GTP-bound active state of K-RAS.

Syringa reticulata potently inhibits the activity of SARS-CoV-2 3CL protease

The ongoing coronavirus infectious disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) still urgently requires effective treatments. The 3C-like (3CL) protease of SARS-CoV-2 is a highly conserved cysteine protease that plays an important role in the viral life cycle and host inflammation, providing an ideal target for developing broad-spectrum antiviral drugs. Herein, we describe the discovery of a large number of herbs mainly produced in Heilongjiang Province, China, that exhibited different inhibitory activities against SARS-CoV-2 3CL protease. We confirmed that Syringa reticulata, which is used for clinical treatment of chronic bronchitis and asthma, is a specific and potent inhibitor of 3CL protease. A 70 % ethanol extract of S. reticulata dose-dependently inhibited the cleavage activity of 3CL protease in a fluorescence resonance energy transfer assay with an IC50 value of 0.0018 mg/mL, but had minimal effect in pseudovirus-based cell entry and luciferase-based RNA-dependent RNA polymerase assays. These results suggest that S. reticulata will be a potential leading candidate for COVID-19 treatment.

Pathogenic Variants in USH1G/SANS Alter Protein Interaction with Pre-RNA Processing Factors PRPF6 and PRPF31 of the Spliceosome.

Pre-mRNA splicing is an essential process orchestrated by the spliceosome, a dynamic complex assembled stepwise on pre-mRNA. We have previously identified that USH1G protein SANS regulates pre-mRNA splicing by mediating the intranuclear transfer of the spliceosomal U4/U6.U5 tri-snRNP complex. During this process, SANS interacts with the U4/U6 and U5 snRNP-specific proteins PRPF31 and PRPF6 and regulates splicing, which is disturbed by variants of USH1G/SANS causative for human Usher syndrome (USH), the most common form of hereditary deaf-blindness. Here, we aim to gain further insights into the molecular interaction of the splicing molecules PRPF31 and PRPF6 to the CENTn domain of SANS using fluorescence resonance energy transfer assays in cells and in silico deep learning-based protein structure predictions. This demonstrates that SANS directly binds via two distinct conserved regions of its CENTn to the two PRPFs. In addition, we provide evidence that these interactions occur sequentially and a conformational change of an intrinsically disordered region to a short α-helix of SANS CENTn2 is triggered by the binding of PRPF6. Furthermore, we find that pathogenic variants of USH1G/SANS perturb the binding of SANS to both PRPFs, implying a significance for the USH1G pathophysiology.

First Full-Length Cloning of Human NaV1.7 in S. Cerevisiae-Based Novel D-Crypt Platform for its High-Scale Production

NaV1.7, a voltage-gated sodium channel, induces chronic pain. Current research on the discovery of inhibitors against NaV1.7 is advancing with the hope of treating chronic pain conditions in patients suffering from various diseases. However, to characterize NaV1.7 and inhibitor interactions, a higher yield of expression is required to obtain sufficient protein. Molecular cloning of hNaV1.7 was done using the homologous recombination method in our novel S. cerevisiae-based D-cryptÔ platform. The platform was designed for the high-yield production of ‘difficult-to-express’ proteins (DTE-Ps) up to 500 L. The changes in the cell membrane potential of hNaV1.7 were determined using a fluorescence resonance energy transfer (FRET) assay with tetracaine (hNaV1.7 inhibitor). Expression analysis of hNaV1.7 showed 2 bands of size 250 and 280 kDa that were absent in untransfected yeast cells. Immunofluorescence images revealed the presence of hNaV1.7 on the membrane of hNaV1.7-expressing yeast cells. Tetracaine exhibited concentration-dependent inhibition of the FRET ratio, with the order of potency (IC50 = 0.46 µM) being approximately the same as previously reported, suggesting the functionality of the channel protein expressed in the D-cryptÔ platform. Cloning of NaV1.7 in the D-cryptÔ platform will help to scale up the production of channel proteins, which will ultimately help in the structural and functional characterization of the binding interactions between toxins and the NaV1.7 channel to identify more specific NaV1.7 inhibitors. HIGHLIGHTS 7 is a voltage-gated sodium channel and induces chronic pain 7 inhibitors can advance the treatment of chronic pain associated with various diseases To characterize interaction of Nav1.7 with its inhibitors, higher yield of the NaV1.7 is required D-crypt is a platform designed for the high-yield production of ‘difficult-to-express’ proteins (DTE-Ps) up to 500 L Successful cloning of NaV1.7 in D-crypt platform suggest that the D-crypt platform is a suitable platform for expressing full-length functionally active hNaV1.7 channel at larger scale. It will further aid in the screening of NaV1.7 inhibitors GRAPHICAL ABSTRACT

INPP5D is associated with tau seeding and tau pathogenesis

AbstractBackgroundAlzheimer’s disease (AD) is the most common type of dementia characterized by extracellular amyloid deposits and intracellular neurofibrillary tangles composed of hyperphosphorylated tau aggregates. GWAS studies have identified variants in several inflammatory genes as significant risk factors for AD, highlighting that neuroinflammation is a critical, underlying pathological component in AD. INPP5D, a family member of Src homology 2 domain containing inositol 5' polyphosphatases (SHIPs), is an AD risk gene related to innate immunity in late‐onset AD (LOAD). Inpp5d plays a role in regulating signal transduction initiated by immune cell surface receptors. INPP5D binds receptor ITIMs, competes with kinases, and converts PI(3,4,5)P3 to PI(3,4)P¬2, thereby limiting downstream signaling. We previously reported that Inpp5d expression is increased in LOAD and is positively correlated with amyloid burden. However, the relationship of Inpp5d in tau pathology remains unclear. We hypothesize that inhibiting INPP5D will release the break and increase microglial function.MethodsTo assess the role of Inpp5d in tau pathology, we performed a fluorescence resonance energy transfer (FRET) assay on human‐AD brains obtained from NCRAD. We also crossed a mouse model deficient in Inpp5d (Inpp5d+/−) with a PS19 model of tau pathology and measured tau phosphorylation and transcriptomics. Primary microglia were utilized to measure microglial internalization of Tau.ResultsIn human AD‐ brains, increased tau seeding was positively correlated with Inpp5d expression. Furthermore, in PS19 mice, Inpp5d protein expression was upregulated and positively correlated with phosphorylated tau (S202, Thr205). Utilizing the NanoString nCounter assay, we found an upregulation of the immune‐related and cell migration related genes in PS19.Inpp5d+/‐ mice compared to PS19 mice. Primary microglia from Inpp5d+/− mice released increased tau internalization compared to WT microglia.ConclusionOur findings confirmed that elevated Inpp5d expression in human‐AD subjects is recapitulated in PS19 mice and correlated with increased tau pathology. In PS19.Inpp5d+/‐ mice we found alterations in immune related and cell migration related pathways suggesting that Inpp5d modulates the disease progression through these pathways. Furthermore, pathogenesis may be modulated through increased internalization of tau. Together these results suggest that therapeutic interventions aimed at reducing Inpp5d may be beneficial in tauopathies.

CP-25 inhibits the hyperactivation of rheumatic synoviocytes by suppressing the switch in Gαs-Gαi coupling to the β2-adrenergic receptor

In essence, the β2 adrenergic receptor (β2AR) plays an antiproliferative role by increasing the intracellular cyclic 3’,5’-adenosine monophosphate (cAMP) concentration through Gαs coupling, but interestingly, β2AR antagonists are able to effectively inhibit fibroblast-like synoviocytes (FLSs) proliferation, thus ameliorating experimental RA, indicating that the β2AR signalling pathway is impaired in RA FLSs via unknown mechanisms. The local epinephrine (Epi) level was found to be much higher in inflammatory joints than in normal joints, and high-level stimulation with Epi or isoproterenol (ISO) directly promoted FLSs proliferation and migration due to impaired β2AR signalling and cAMP production. By applying inhibitor of receptor internalization, and small interfering RNA (siRNA) of Gαs and Gαi, and by using fluorescence resonance energy transfer and coimmunoprecipitation assays, a switch in Gαs-Gαi coupling to β2AR was observed in inflammatory FLSs as well as in FLSs with chronic ISO stimulation. This Gαi coupling was then revealed to be initiated by G protein coupled receptor kinase 2 (GRK2) but not β-arrestin2 or protein kinase A-mediated phosphorylation of β2AR. Inhibiting the activity of GRK2 with the novel GRK2 inhibitor paeoniflorin-6′-O-benzene sulfonate (CP-25), a derivative of paeoniflorin, or the accepted GRK2 inhibitor paroxetine effectively reversed the switch in Gαs-Gαi coupling to β2AR during inflammation and restored the intracellular cAMP level in ISO-stimulated FLSs. As expected, CP-25 significantly inhibited the hyperplasia of FLSs in a collagen-induced arthritis (CIA) model (CIA FLSs) and normal FLSs stimulated with ISO and finally ameliorated CIA in rats. Together, our findings revealed the pathological changes in β2AR signalling in CIA FLSs, determined the underlying mechanisms and identified the pharmacological target of the GRK2 inhibitor CP-25 in treating CIA.7HWufKwpH5ZfY_hx8fyY6aVideo

DDX41 Dissolves G-Quadruplexes to Maintain Erythroid Genomic Integrity and Prevent Genome DNA Leakage-Induced Cgas Activation

DDX41 is one of the most frequently mutated genes that are associated with familial myeloid neoplasms. To understand the pathogenesis of DDX41 mutations, which often lead to loss of function, we developed various mouse models with lineage-specific deletion of Ddx41. We found embryonical lethality with the hematopoietic specific knockout (KO) of Ddx41 ( VavCre:Ddx41 fl/fl). Examination of E13.5 fetuses showed that Ddx41 deficient fetal livers are pale with marked apoptosis, indicating defects in erythropoiesis. Indeed, depletion of Ddx41 in the early stage of erythropoiesis ( EpoRCre:Ddx41 fl/fl) also led to embryonic death. However, mice with Ddx41 KO in the late-stage erythropoiesis ( HBBCre:Ddx41 fl/fl) survived with normal complete blood count, indicating a stage-specific requirement of Ddx41 in erythropoiesis. We further revealed that mice with Ddx41 KO in monocytes ( LysMCre:Ddx41 fl/fl), granulocytes ( MRP8Cre:Ddx41 fl/ fl), and dendritic cells ( CD11cCre:Ddx41 fl/fl) also showed no obvious phenotypes, suggesting that Ddx41 is dispensable in other myeloid cells in mice. We further discovered that Ddx41 KO in erythroid cells induces the accumulation of G-quadruplexes (G4), a noncanonical DNA structure that is often associated with active replication. We found that erythroid cells contain significantly higher G4 signals. G4 accumulation reaches its peak level in the CFU-Es and proerythroblasts, which is likely due to replication stress at this stage of erythropoiesis and consistent with the lethality of EpoRCre:Ddx41 fl/flmice. A CUT&amp;Tag analysis revealed genome-wide colocalization of Ddx41 and G4 in hematopoietic stem and progenitor cells, which became further enhanced in erythroid cells. We confirmed the direct binding of Ddx41 to G4, which is sequence independent. A fluorescence resonance energy transfer (FRET) assay demonstrated that Ddx41 binds to and dose-dependently dissolves G4. These findings indicate a critical role of DDX41 in erythropoiesis by maintaining the level of G4 and genomic integrity. Consistent with the knowledge that increased level of G4 induces genomic instability, we found an increased level of γ-H2AX in Ddx41 KO erythroid cells or cells treated with pyridostatin (PDS), a well-known G4 stabilizer. One unique feature of developing erythroblasts is the dynamic nuclear opening with the release of genomic materials, which is critical for nuclear condensation. However, this process also poses potential risks of triggering the cGAS-STING pathway with the increased damage-associated molecular patterns (DAMPs), particularly under situations with increased genomic instability. Indeed, we found an increased level of cGAS and STING in Ddx41 KO and PDS-treated erythroid cells. Consistently, erythroblasts from cGAS KO mice are resistant to PDS treatment mediated cell death. The significance of the cGAS pathway was genetically confirmed in that cGAS KO completely rescued the lethality of VavCre:Ddx41 fl/fl mice. In addition, we demonstrated that Ddx41 KO and PDS treatment-mediated activation of the cGAS-STING pathway induces an increased level of interferon, which results in ribosome biogenesis defect, p53 upregulation, and cell apoptosis. Notably, cGAS KO in VavCre:Ddx41 fl/fl mice counteracted these effects and rescued erythroid ribosomopathy, although the level of G4 remains upregulated. Overall, our study reveals a critical role of DDX41 in dissolving G4 and maintaining the genomic integrity of the erythroid cells. Our data also indicate that defect in the erythroid lineage through ribosomopathy is one of the major pathologic features in DDX41 mutated myeloid neoplasms, which is important for the development of novel therapies.