Untargeted metabolomic profiling in children identifies novel pathways in asthma and atopy.

BACKGROUND: Asthma and other atopic disorders can present with varying clinical phenotypes marked by differential metabolomic manifestations and enriched biological pathways. OBJECTIVE: We sought to identify these unique metabolomic profiles in atopy and asthma. METHODS: We analyzed baseline nonfasted plasma samples from a large multisite pediatric population of 470 children aged <13 years from 3 different sites in the United States and France. Atopy positivity (At+) was defined as skin prick test result of ≥3 mm and/or specific IgE ≥ 0.35 IU/mL and/or total IgE ≥ 173 IU/mL. Asthma positivity (As+) was based on physician diagnosis. The cohort was divided into 4 groups of varying combinations of asthma and atopy, and 6 pairwise analyses were conducted to best assess the differential metabolomic profiles between groups. RESULTS: Two hundred ten children were classified as At-As-, 42 as At+As-, 74 as At-As+, and 144 as At+As+. Untargeted global metabolomic profiles were generated through ultra-high-performance liquid chromatography-tandem mass spectroscopy. We applied 2 independent machine learning classifiers and short-listed 362 metabolites as discriminant features. Our analysis showed the most diverse metabolomic profile in the At+As+/At-As- comparison, followed by the At-As+/At-As- comparison, indicating that asthma is the most discriminant condition associated with metabolomic changes. At+As+ metabolomic profiles were characterized by higher levels of bile acids, sphingolipids, and phospholipids, and lower levels of polyamine, tryptophan, and gamma-glutamyl amino acids. CONCLUSION: The At+As+ phenotype displays a distinct metabolomic profile suggesting underlying mechanisms such as modulation of host-pathogen and gut microbiota interactions, epigenetic changes in T-cell differentiation, and lower antioxidant properties of the airway epithelium.

Combining avidin with CD63 improves basophil activation test accuracy in classifying peanut allergy.

BACKGROUND: Conventional basophil activation tests (BATs) measure basophil activation by the increased expression of CD63. Previously, fluorophore-labeled avidin, a positively-charged molecule, was found to bind to activated basophils, which tend to expose negatively charged granule constituents during degranulation. This study further compares avidin versus CD63 as basophil activation biomarkers in classifying peanut allergy. METHODS: Seventy subjects with either a peanut allergy (N = 47), a food allergy other than peanut (N = 6), or no food allergy (N = 17) were evaluated. We conducted BATs in response to seven peanut extract (PE) concentrations (0.01-10,000 ng/mL) and four control conditions (no stimulant, anti-IgE, fMLP (N-formylmethionine-leucyl-phenylalanine), and anti-FcεRI). We measured avidin binding and CD63 expression on basophils with flow cytometry. We evaluated logistic regression and XGBoost models for peanut allergy classification and feature identification. RESULTS: Avidin binding was correlated with CD63 expression. Both markers discriminated between subjects with and without a peanut allergy. Although small by percentage, an avidin+ /CD63- cell subset was found in all allergic subjects tested, indicating that the combination of avidin and CD63 could allow a more comprehensive identification of activated basophils. Indeed, we obtained the best classification accuracy (97.8% sensitivity, 96.7% specificity) by combining avidin and CD63 across seven PE doses. Similar accuracy was obtained by combining PE dose of 10,000 ng/mL for avidin and PE doses of 10 and 100 ng/mL for CD63. CONCLUSIONS: Avidin and CD63 are reliable BAT activation markers associated with degranulation. Their combination enhances the identification of activated basophils and improves the classification accuracy of peanut allergy.

Proinflammatory polarization of monocytes by particulate air pollutants is mediated by induction of trained immunity in pediatric asthma.

BACKGROUND: The impact of exposure to air pollutants, such as fine particulate matter (PM), on the immune system and its consequences on pediatric asthma, are not well understood. We investigated whether ambient levels of fine PM with aerodynamic diameter ≤2.5 microns (PM2.5 ) are associated with alterations in circulating monocytes in children with or without asthma. METHODS: Monocyte phenotyping was performed by cytometry time-of-flight (CyTOF). Cytokines were measured using cytometric bead array and Luminex assay. ChIP-Seq was utilized to address histone modifications in monocytes. RESULTS: Increased exposure to ambient PM2.5 was linked to specific monocyte subtypes, particularly in children with asthma. Mechanistically, we hypothesized that innate trained immunity is evoked by a primary exposure to fine PM and accounts for an enhanced inflammatory response after secondary stimulation in vitro. We determined that the trained immunity was induced in circulating monocytes by fine particulate pollutants, and it was characterized by the upregulation of proinflammatory mediators, such as TNF, IL-6, and IL-8, upon stimulation with house dust mite or lipopolysaccharide. This phenotype was epigenetically controlled by enhanced H3K27ac marks in circulating monocytes. CONCLUSION: The specific alterations of monocytes after ambient pollution exposure suggest a possible prognostic immune signature for pediatric asthma, and pollution-induced trained immunity may provide a potential therapeutic target for asthmatic children living in areas with increased air pollution.

CyAnno: a semi-automated approach for cell type annotation of mass cytometry datasets.

MOTIVATION: For immune system monitoring in large-scale studies at the single-cell resolution using CyTOF, (semi-)automated computational methods are applied for annotating live cells of mixed cell types. Here, we show that the live cell pool can be highly enriched with undefined heterogeneous cells, i.e. 'ungated' cells, and that current semi-automated approaches ignore their modeling resulting in misclassified annotations. RESULT: We introduce 'CyAnno', a novel semi-automated approach for deconvoluting the unlabeled cytometry dataset based on a machine learning framework utilizing manually gated training data that allows the integrative modeling of 'gated' cell types and the 'ungated' cells. By applying this framework on several CyTOF datasets, we demonstrated that including the 'ungated' cells can lead to a significant increase in the precision of the 'gated' cell types prediction. CyAnno can be used to identify even a single cell type, including rare cells, with higher efficacy than current state-of-the-art semi-automated approaches. AVAILABILITY AND IMPLEMENTATION: The CyAnno is available as a python script with a user-manual and sample dataset at https://github.com/abbioinfo/CyAnno. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

The genome of the zoonotic malaria parasite Plasmodium simium reveals adaptations to host switching.

BACKGROUND: Plasmodium simium, a malaria parasite of non-human primates (NHP), was recently shown to cause zoonotic infections in humans in Brazil. We sequenced the P. simium genome to investigate its evolutionary history and to identify any genetic adaptions that may underlie the ability of this parasite to switch between host species. RESULTS: Phylogenetic analyses based on whole genome sequences of P. simium from humans and NHPs reveals that P. simium is monophyletic within the broader diversity of South American Plasmodium vivax, suggesting P. simium first infected NHPs as a result of a host switch of P. vivax from humans. The P. simium isolates show the closest relationship to Mexican P. vivax isolates. Analysis of erythrocyte invasion genes reveals differences between P. vivax and P. simium, including large deletions in the Duffy-binding protein 1 (DBP1) and reticulocyte-binding protein 2a genes of P. simium. Analysis of P. simium isolated from NHPs and humans revealed a deletion of 38 amino acids in DBP1 present in all human-derived isolates, whereas NHP isolates were multi-allelic. CONCLUSIONS: Analysis of the P. simium genome confirmed a close phylogenetic relationship between P. simium and P. vivax, and suggests a very recent American origin for P. simium. The presence of the DBP1 deletion in all human-derived isolates tested suggests that this deletion, in combination with other genetic changes in P. simium, may facilitate the invasion of human red blood cells and may explain, at least in part, the basis of the recent zoonotic infections.

Novel tumour suppressor roles for GZMA and RASGRP1 in Theileria annulata-transformed macrophages and human B lymphoma cells.

Theileria annulata is a tick-transmitted apicomplexan parasite that infects and transforms bovine leukocytes into disseminating tumours that cause a disease called tropical theileriosis. Using comparative transcriptomics we identified genes transcriptionally perturbed during Theileria-induced leukocyte transformation. Dataset comparisons highlighted a small set of genes associated with Theileria-transformed leukocyte dissemination. The roles of Granzyme A (GZMA) and RAS guanyl-releasing protein 1 (RASGRP1) were verified by CRISPR/Cas9-mediated knockdown. Knocking down expression of GZMA and RASGRP1 in attenuated macrophages led to a regain in their dissemination in Rag2/γC mice confirming their role as dissemination suppressors in vivo. We further evaluated the roles of GZMA and RASGRP1 in human B lymphomas by comparing the transcriptome of 934 human cancer cell lines to that of Theileria-transformed bovine host cells. We confirmed dampened dissemination potential of human B lymphomas that overexpress GZMA and RASGRP1. Our results provide evidence that GZMA and RASGRP1 have a novel tumour suppressor function in both T. annulata-infected bovine host leukocytes and in human B lymphomas.

An RNAi-based high-throughput screening assay to identify small molecule inhibitors of hepatitis B virus replication.

Persistent or chronic infection with the hepatitis B virus (HBV) represents one of the most common viral diseases in humans. The hepatitis B virus deploys the hepatitis B virus X protein (HBx) as a suppressor of host defenses consisting of RNAi-based silencing of viral genes. Because of its critical role in countering host defenses, HBx represents an attractive target for antiviral drugs. Here, we developed and optimized a loss-of-function screening procedure, which identified a potential pharmacophore that abrogated HBx RNAi suppression activity. In a survey of 14,400 compounds in the Maybridge Screening Collection, we prioritized candidate compounds via high-throughput screening based on reversal of green fluorescent protein (GFP)-reported, RNAi-mediated silencing in a HepG2/GFP-shRNA RNAi sensor line. The screening yielded a pharmacologically active compound, N-(2,4-difluorophenyl)-N'-[3-(1H-imidazol-1-yl) propyl] thiourea (IR415), which blocked HBx-mediated RNAi suppression indicated by the GFP reporter assay. We also found that IR415 reversed the inhibitory effect of HBx protein on activity of the Dicer endoribonuclease. We further confirmed the results of the primary screen in IR415-treated, HBV-infected HepG2 cells, which exhibited a marked depletion of HBV core protein synthesis and down-regulation of pre-genomic HBV RNA. Using a molecular interaction analysis system, we confirmed that IR415 selectively targets HBx in a concentration-dependent manner. The screening assay presented here allows rapid and improved detection of small-molecule inhibitors of HBx and related viral proteins. The assay may therefore potentiate the development of next-generation RNAi pathway-based therapeutics and promises to accelerate our search for novel and effective drugs in antiviral research.

Role of CYP1B1, p.E229K and p.R368H mutations among 120 families with sporadic juvenile onset open-angle glaucoma.

BACKGROUND: To determine the frequency of CYP1B1 p.E229K and p.R368H, gene mutations in a cohort of sporadic juvenile onset open-angle glaucoma (JOAG) patients and to evaluate their genotype/phenotype correlation. METHODS: Unrelated JOAG patients whose first-degree relatives had been examined and found to be unaffected were included in the study. The patients and their parents were screened for p.E229K and p.R368H mutations. The phenotypic characteristics were compared between probands carrying the mutations and those who did not carry these mutations. RESULTS: Out of 120 JOAG patients included in the study, the p.E229K mutation was seen in 9 probands (7.5%) and p.R368H in 7 (5.8%). The average age of onset of the disease (p = 0.3) and the highest untreated IOP (p = 0.4) among those carrying mutations was not significantly different from those who did not have these mutations. The proportion of probands with angle dysgenesis among those with p.E229K and p.R368H mutations was 70% (11 out of 16) in comparison to 65% (67 out of 104) of those who did not harbour these mutations (p = 0.56). Similarly, the probands with moderate to high myopia among those with p.E229K and p.R368H mutations was 20% (3 out of 16) in comparison to 18% (18 out of 104) of those who did not harbour these mutations (p = 0.59). CONCLUSION: The frequency of p.E229K and p.R368H mutations of the CYP1B1 gene is low even among sporadic JOAG patients. Moreover, there is no clinical correlation between the presence of these mutations and disease severity.

Proteomic Identification and Analysis of Arginine-Methylated Proteins of Plasmodium falciparum at Asexual Blood Stages.

Plasmodium falciparum undergoes a tightly regulated developmental process in human erythrocytes, and recent studies suggest an important regulatory role of post-translational modifications (PTMs). As compared with Plasmodium phosphoproteome, little is known about other PTMs in the parasite. In the present study, we performed a global analysis of asexual blood stages of Plasmodium falciparum to identify arginine-methylated proteins. Using two different methyl arginine-specific antibodies, we immunoprecipitated the arginine-methylated proteins from the stage-specific parasite lysates and identified 843 putative arginine-methylated proteins by LC-MS/MS. Motif analysis of the protein sequences unveiled that the methylation sites are associated with the previously known methylation motifs such as GRx/RGx, RxG, GxxR, or WxxxR. We identified Plasmodium homologues of known arginine-methylated proteins in trypanosomes, yeast, and human. Hydrophilic interaction liquid chromatography (HILIC) was performed on the immunoprecipitates from the trophozoite stage to enrich arginine-methylated peptides. Mass spectrometry analysis of immunoprecipitated and HILIC fractions identified 55 arginine-methylated peptides having 62 methylated arginine sites. Functional classification revealed that the arginine-methylated proteins are involved in RNA metabolism, protein synthesis, intracellular protein trafficking, proteolysis, protein folding, chromatin organization, hemoglobin metabolic process, and several other functions. Summarily, the findings suggest that protein methylation of arginine residues is a widespread phenomenon in Plasmodium, and the PTM may play an important regulatory role in a diverse set of biological pathways, including host-pathogen interactions.

Cross-reactive MHC class I T cell epitopes may dictate heterologous immune responses between respiratory viruses and food allergens.

Respiratory virus infections play a major role in asthma, while there is a close correlation between asthma and food allergy. We hypothesized that T cell-mediated heterologous immunity may induce asthma symptoms among sensitized individuals and used two independent in silico pipelines for the identification of cross-reactive virus- and food allergen- derived T cell epitopes, considering individual peptide sequence similarity, MHC binding affinity and immunogenicity. We assessed the proteomes of human rhinovirus (RV1b), respiratory syncytial virus (RSVA2) and influenza-strains contained in the seasonal quadrivalent influenza vaccine 2019/2020 (QIV 2019/2020), as well as SARS-CoV-2 for human HLA alleles, in addition to more than 200 most common food allergen protein sequences. All resulting allergen-derived peptide candidates were subjected to an elaborate scoring system considering multiple criteria, including clinical relevance. In both bioinformatics approaches, we found that shortlisted peptide pairs that are potentially binding to MHC class II molecules scored up to 10 × lower compared to MHC class I candidate epitopes. For MHC class I food allergen epitopes, several potentially cross-reactive peptides from shrimp, kiwi, apple, soybean and chicken were identified. The shortlisted set of peptide pairs may be implicated in heterologous immune responses and translated to peptide immunization strategies with immunomodulatory properties.

Granzymes, IL-16, and poly(ADP-ribose) polymerase 1 increase during wildfire smoke exposure.

Background: Given the increasing prevalence of wildfires worldwide, understanding the effects of wildfire air pollutants on human health-particularly in specific immunologic pathways-is crucial. Exposure to air pollutants is associated with cardiorespiratory disease; however, immune and epithelial barrier alterations require further investigation. Objective: We sought to determine the impact of wildfire smoke exposure on the immune system and epithelial barriers by using proteomics and immune cell phenotyping. Methods: A San Francisco Bay area cohort (n = 15; age 30 ± 10 years) provided blood samples before (October 2019 to March 2020; air quality index = 37) and during (August 2020; air quality index = 80) a major wildfire. Exposure samples were collected 11 days (range, 10-12 days) after continuous exposure to wildfire smoke. We determined alterations in 506 proteins, including zonulin family peptide (ZFP); immune cell phenotypes by cytometry by time of flight (CyTOF); and their interrelationship using a correlation matrix. Results: Targeted proteomic analyses (n = 15) revealed a decrease of spondin-2 and an increase of granzymes A, B, and H, killer cell immunoglobulin-like receptor 3DL1, IL-16, nibrin, poly(ADP-ribose) polymerase 1, C1q TNF-related protein, fibroblast growth factor 19, and von Willebrand factor after 11 days' average continuous exposure to smoke from a large wildfire (P < .05). We also observed a large correlation cluster between immune regulation pathways (IL-16, granzymes A, B, and H, and killer cell immunoglobulin-like receptor 3DL1), DNA repair [poly(ADP-ribose) 1, nibrin], and natural killer cells. We did not observe changes in ZFP levels suggesting a change in epithelial barriers. However, ZFP was associated with immune cell phenotypes (naive CD4+, TH2 cells). Conclusion: We observed functional changes in critical immune cells and their proteins during wildfire smoke exposure. Future studies in larger cohorts or in firefighters exposed to wildfire smoke should further assess immune changes and intervention targets.

Pangenome Analysis of the Soilborne Fungal Phytopathogen Rhizoctonia solani and Development of a Comprehensive Web Resource: RsolaniDB.

Rhizoctonia solani is a collective group of genetically and pathologically diverse basidiomycetous fungi that damage economically important crops. Its isolates are classified into 13 Anastomosis Groups (AGs) and subgroups having distinctive morphology and host ranges. The genetic factors driving the unique features of R. solani pathology are not well characterized due to the limited availability of its annotated genomes. Therefore, we performed genome sequencing, assembly, annotation and functional analysis of 12 R. solani isolates covering 7 AGs and select subgroups (AG1-IA; AG1-IB; AG1-IC; AG2-2IIIB; AG3-PT, isolates Rhs 1AP and the hypovirulent Rhs1A1; AG3-TB; AG4-HG-I, isolates Rs23 and R118-11; AG5; AG6; and AG8), in which six genomes are reported for the first time. Using a pangenome comparative analysis of 12 R. solani isolates and 15 other Basidiomycetes, we defined the unique and shared secretomes, CAZymes, and effectors across the AGs. We have also elucidated the R. solani-derived factors potentially involved in determining AG-specific host preference, and the attributes distinguishing them from other Basidiomycetes. Finally, we present the largest repertoire of R. solani genomes and their annotated components as a comprehensive database, viz. RsolaniDB, with tools for large-scale data mining, functional enrichment and sequence analysis not available with other state-of-the-art platforms.

CD8+ T cell differentiation status correlates with the feasibility of sustained unresponsiveness following oral immunotherapy.

While food allergy oral immunotherapy (OIT) can provide safe and effective desensitization (DS), the immune mechanisms underlying development of sustained unresponsiveness (SU) following a period of avoidance are largely unknown. Here, we compare high dimensional phenotypes of innate and adaptive immune cell subsets of participants in a previously reported, phase 2 randomized, controlled, peanut OIT trial who achieved SU vs. DS (no vs. with allergic reactions upon food challenge after a withdrawal period; n = 21 vs. 30 respectively among total 120 intent-to-treat participants). Lower frequencies of naïve CD8+ T cells and terminally differentiated CD57+CD8+ T cell subsets at baseline (pre-OIT) are associated with SU. Frequency of naïve CD8+ T cells shows a significant positive correlation with peanut-specific and Ara h 2-specific IgE levels at baseline. Higher frequencies of IL-4+ and IFNγ+ CD4+ T cells post-OIT are negatively correlated with SU. Our findings provide evidence that an immune signature consisting of certain CD8+ T cell subset frequencies is potentially predictive of SU following OIT.

Homologies between SARS-CoV-2 and allergen proteins may direct T cell-mediated heterologous immune responses.

The outbreak of the new severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a public health emergency. Asthma does not represent a risk factor for COVID-19 in several published cohorts. We hypothesized that the SARS-CoV-2 proteome contains T cell epitopes, which are potentially cross-reactive to allergen epitopes. We aimed at identifying homologous peptide sequences by means of two distinct complementary bioinformatics approaches. Pipeline 1 included prediction of MHC Class I and Class II epitopes contained in the SARS-CoV-2 proteome and allergens along with alignment and elaborate ranking approaches. Pipeline 2 involved alignment of SARS-CoV-2 overlapping peptides with known allergen-derived T cell epitopes. Our results indicate a large number of MHC Class I epitope pairs including known as well as de novo predicted allergen T cell epitopes with high probability for cross-reactivity. Allergen sources, such as Aspergillus fumigatus, Phleum pratense and Dermatophagoides species are of particular interest due to their association with multiple cross-reactive candidate peptides, independently of the applied bioinformatic approach. In contrast, peptides derived from food allergens, as well as MHC class II epitopes did not achieve high in silico ranking and were therefore not further investigated. Our findings warrant further experimental confirmation along with examination of the functional importance of such cross-reactive responses.

Global survey-based assessment of lifestyle changes during the COVID-19 pandemic.

Along with the major impact on public health, the COVID-19 outbreak has caused unprecedented concerns ranging from sudden loss of employment to mental stress and anxiety. We implemented a survey-based data collection platform to characterize how the COVID-19 pandemic has affected the socio-economic, physical and mental health conditions of individuals. We focused on three broad areas, namely, changes in social interaction during home confinement, economic impact and their health status. We identified a substantial increase in virtual interaction among individuals, which might be a way to alleviate the sudden unprecedented mental health burden, exacerbated by general awareness about viral infections or other manifestations associated with them. The majority of participants (85%) lived with one or more companions and unemployment issues did not affect 91% of the total survey takers, which was one of the crucial consequences of the pandemic. Nevertheless, measures such as an increased frequency of technology-aided distant social interaction, focus on physical fitness and leisure activities were adopted as coping mechanisms during this period of home isolation. Collectively, these metrics provide a succinct and informative summary of the socio-economic and health impact of the COVID-19 pandemic on the individuals. Findings from our study reflect that continuous surveillance of the psychological consequences for outbreaks should become routine as part of preparedness efforts worldwide. Given the limitations of analyzing the large number of variables, we have made the raw data publicly available on the OMF ME/CFS Data Center server to facilitate further analyses (https://igenomed.stanford.edu/dataset/survey-study-on-lifestyle-changes-during-covid-19-pandemic).

Changes in strand 6B and helix B during neuroserpin inhibition: Implication in severity of clinical phenotype.

Neuroserpin (NS) is predominantly expressed in brain and inhibits tissue-type plasminogen activator (tPA) with implications in brain development and memory. Nature of conformational change in pathological variants in strand 6B and helix B of NS that cause a relatively mild to severe epilepsy (and/or dementia) remains largely elusive. MD simulation with wild type (WT) NS, strand 6B and helix B variants indicated that substitution in this region affects the conformation of the strands 5B, 5A and reactive centre loop. Therefore, we designed variants of NS in strand 6B (I46D and F48S) and helix B (A54F, L55A and L55P) to investigate their role in tPA inhibition mechanism and propensity to aggregate. An interaction analysis showed disturbance of a hydrophobic patch centered at strands 5B, 6B and helix B in I46D and F48S but not in A54F, L55A, L55P and WT NS. Purified I46D, F48S and L55P variants showed decrease in fluorescence emission intensity but have similar α-helical content, however results of A54F and L55A were comparable to WT NS. Analysis of tPA inhibition showed marginal effect on A54F and L55A variant with tPA-NS complex formation. In contrast, I46D, F48S and L55P variants showed massive decrease in tPA inhibition, with no tPA-NS complex formation. Analysis of native PAGE under under polymerization condition showed prompt conversion of I46D, F48S and L55P to latent conformation but not A54F and L55A variants. Identification of these novel conformational changes will aid in the understanding of variable clinical phenotype of shutter region NS variants and other serpins.

Homologies between SARS-CoV-2 and allergen proteins may direct T cell-mediated heterologous immune responses.

The outbreak of the new Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is a public health emergency. Asthma does not represent a risk factor for COVID-19 in several published cohorts. We hypothesized that the SARS-CoV-2 proteome contains T cell epitopes, which are potentially cross-reactive to allergen epitopes. We aimed at identifying homologous peptide sequences by means of two distinct complementary bioinformatics approaches. Pipeline 1 included prediction of MHC Class I and Class II epitopes contained in the SARS-CoV-2 proteome and allergens along with alignment and elaborate ranking approaches. Pipeline 2 involved alignment of SARS-CoV-2 overlapping peptides with known allergen-derived T cell epitopes. Our results indicate a large number of MHC Class I epitope pairs including known as well as de novo predicted allergen T cell epitopes with high probability for cross-reactivity. Allergen sources, such as Aspergillus fumigatus , Phleum pratense and Dermatophagoides species are of particular interest due to their association with multiple cross-reactive candidate peptides, independently of the applied bioinformatic approach. In contrast, peptides derived from food allergens, as well as MHC class II epitopes did not achieve high in silico ranking and were therefore not further investigated. Our findings warrant further experimental confirmation along with examination of the functional importance of such cross-reactive responses.

Computational prediction and experimental validation of the activator function of C2-ß-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone on pancreatic and hepatic hexokinase.

This study identifies and validates hexokinase type 4 (HK4), an isozyme of hexokinase in the liver and pancreas, as an important target of C2-ß-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (ßdGT), a xanthone glucoside suggested to have antidiabetic property. In the study, we applied the computational pipeline of molecular docking followed by the molecular dynamics simulations to shortlist potential ßdGT protein targets. The analysis of protein dynamics and the binding free energy (ΔG) led us to the identification of HK4 as a key ßdGT target, whereby the binding mode and domain dynamics suggested the activator function of ßdGT. ßdGT bound to the allosteric site of the isozyme ∼13 Å away from the substrate (glucose)-binding site. The binding free energy of the ligand-protein complex was energetically feasible (ΔG, -41.61 kcal/mol) and the cleft angle deviation between the two (small and large) domains of HK4 revealed differential HK4 dynamics in response to ßdGT binding. 3D structure analysis of the isozyme-ligand complex highlighted the role of Arg63, Glu67 and Lys458 in ligand stabilization and hydrophobic interactions mediated by Tyr214 and Met235. Experimental validation of the results of computational analysis confirmed the activator function of ßdGT on HK4. The study has implication in diabetes as ßdGT may be used to lower the blood glucose level by activating hepatic and pancreatic hexokinase without the risk of hypoglycemia.Communicated by Ramaswamy H. Sarma.