Structural Insight into the Catalytic Mechanisms of an L-Sorbosone Dehydrogenase

L-Sorbosone dehydrogenase (SNDH) is a key enzyme involved in the biosynthesis of 2-keto-L-gulonic acid , which is a direct precursor for the industrial scale production of vitamin C. Elucidating the structure and the catalytic mechanism is essential for improving SNDH performance. By solving the crystal structures of SNDH from Gluconobacter oxydans WSH-004, a reversible disulfide bond between Cys295 and the catalytic Cys296 residues is discovered. It allowed SNDH to switch between oxidation and reduction states, resulting in opening or closing the substrate pocket. Moreover, the Cys296 is found to affect the NADP+ binding pose with SNDH. Combining the in vitro biochemical and site-directed mutagenesis studies, the redox-based dynamic regulation and the catalytic mechanisms of SNDH are proposed. Moreover, the mutants with enhanced activity are obtained by extending substrate channels. This study not only elucidates the physiological control mechanism of the dehydrogenase, but also provides a theoretical basis for engineering similar enzymes.

15 N labeling technology reveals enhancement of nitrogen uptake and transfer by root interaction in cotton/soybean intercropping

BACKGROUND

Biological nitrogen fixation in legumes and their transfer of nitrogen to non-legumes in legume/non-legume intercropping systems are considered to be important for the improvement of productivity. However, research on interspecific interaction and root nitrogen transfer in cotton/soybean intercropping systems has rarely been undertaken. In this study, the roots of cotton and soybean were separated with either complete root barriers (CB), using plastic film, or semi-root barriers (SB), using nylon net. No root barrier (NB) was used as the control.

RESULTS

The results showed that cotton produced more above-ground dry matter (DM) than soybean. The above-ground DM and nitrogen uptake of cotton was greatest with the NB treatment. The above-ground DM and nitrogen uptake of soybean was greatest with the CB treatment. At the harvest stage, the nitrogen transfer rate from soybean to cotton was 22.47% with the SB treatment and 40.41% with the NB treatment. Interspecific root interaction increased the nitrogen transfer amount, especially for the cotton roots in the 0-15 cm soil layer and for the soybean roots in the 0-30 cm soil layer. The root distribution of soybean was the key factor affecting nitrogen transfer amount, and nitrogen transfer amount was the key factor affecting nitrogen uptake of cotton in the cotton/soybean intercropping system.

CONCLUSION

These results indicated that nitrogen transfer from soybean to cotton through root interaction improved cotton above-ground DM and nitrogen uptake. © 2023 Society of Chemical Industry.

Efficient C-N coupling in the direct synthesis of urea from CO2 and N2 by amorphous SbxBi1-xOy clusters

Although direct generation of high-value complex molecules and feedstock by coupling of ubiquitous small molecules such as CO2 and N2 holds great appeal as a potential alternative to current fossil-fuel technologies, suitable scalable and efficient catalysts to this end are not currently available as yet to be designed and developed. To this end, here we prepare and characterize SbxBi1-xOy clusters for direct urea synthesis from CO2 and N2 via C-N coupling. The introduction of Sb in the amorphous BiOx clusters changes the adsorption geometry of CO2 on the catalyst from O-connected to C-connected, creating the possibility for the formation of complex products such as urea. The modulated Bi(II) sites can effectively inject electrons into N2, promoting C-N coupling by advantageous modification of the symmetry for the frontier orbitals of CO2 and N2 involved in the rate-determining catalytic step. Compared with BiOx, SbxBi1-xOy clusters result in a lower reaction potential of only -0.3 V vs. RHE, an increased production yield of 307.97 μg h-1 mg-1cat, and a higher Faraday efficiency (10.9%), pointing to the present system as one of the best catalysts for urea synthesis in aqueous systems among those reported so far. Beyond the urea synthesis, the present results introduce and demonstrate unique strategies to modulate the electronic states of main group p-metals toward their use as effective catalysts for multistep electroreduction reactions requiring C-N coupling.

Requirement of WDR70 for POLE3-mediated DNA double-strand breaks repair

H2BK120ub1 triggers several prominent downstream histone modification pathways and changes in chromatin structure, therefore involving it into multiple critical cellular processes including DNA transcription and DNA damage repair. Although it has been reported that H2BK120ub1 is mediated by RNF20/40 and CRL4WDR70, less is known about the underlying regulation mechanism for H2BK120ub1 by WDR70. By using a series of biochemical and cell-based studies, we find that WDR70 promotes H2BK120ub1 by interacting with RNF20/40 complex, and deposition of H2BK120ub1 and H3K79me2 in POLE3 loci is highly sensitive to POLE3 transcription. Moreover, we demonstrate that POLE3 interacts CHRAC1 to promote DNA repair by regulation on the expression of homology-directed repair proteins and KU80 recruitment and identify CHRAC1 D121Y mutation in colorectal cancer, which leads to the defect in DNA repair due to attenuated the interaction with POLE3. These findings highlight a previously unknown role for WDR70 in maintenance of genomic stability and imply POLE3 and CHRAC1 as potential therapeutic targets in cancer.

Interface-Based Design of High-Affinity Affibody Ligands for the Purification of RBD from Spike Proteins

The outbreak of coronavirus disease 2019 (COVID-19) has sparked an urgent demand for advanced diagnosis and vaccination worldwide. The discovery of high-affinity ligands is of great significance for vaccine and diagnostic reagent manufacturing. Targeting the receptor binding domain (RBD) from the spike protein of severe acute respiratory syndrome-coronavirus 2, an interface at the outer surface of helices on the Z domain from protein A was introduced to construct a virtual library for the screening of ZRBD affibody ligands. Molecular docking was performed using HADDOCK software, and three potential ZRBD affibodies, ZRBD-02, ZRBD-04, and ZRBD-07, were obtained. Molecular dynamics (MD) simulation verified that the binding of ZRBD affibodies to RBD was driven by electrostatic interactions. Per-residue free energy decomposition analysis further substantiated that four residues with negative-charge characteristics on helix α1 of the Z domain participated in this process. Binding affinity analysis by microscale thermophoresis showed that ZRBD affibodies had high affinity for RBD binding, and the lowest dissociation constant was 36.3 nmol/L for ZRBD-07 among the three potential ZRBD affibodies. Herein, ZRBD-02 and ZRBD-07 affibodies were selected for chromatographic verifications after being coupled to thiol-activated Sepharose 6 Fast Flow (SepFF) gel. Chromatographic experiments showed that RBD could bind on both ZRBD SepFF gels and was eluted by 0.1 mol/L NaOH. Moreover, the ZRBD-07 SepFF gel had a higher affinity for RBD. This research provided a new idea for the design of affibody ligands and validated the potential of affibody ligands in the application of RBD purification from complex feedstock.

Highly selective NH3 synthesis from N2 on electron-rich Bi0 in a pressurized electrolyzer

Electrochemical conversion of N2 into ammonia presents a sustainable pathway to produce hydrogen storage carrier but yet requires further advancement in electrocatalyst design and electrolyzer integration. This technology suffers from low selectivity and yield owing to the extremely strong N≡N bond and the exceptionally low solubility of N2 in aqueous systems. A high NH3 synthesis performance is restricted by the high activation energy of N≡N bond and the supply insufficiency of N2 to active sites. This paper describes the introduction of electron-rich Bi0 sites into Ag catalysts with a high-pressure electrolyzer that enables a dramatically enhanced Faradaic efficiency of 44.0% and yield of 28.43 μg cm-2 h-1 at 4.0 MPa. Combined with density functional theory results, in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy demonstrates that N2 reduction reaction follows an associative mechanism, in which a high coverage of N-N bond and -NH2 intermediates suggest electron-rich Bi0 boosts sound activation of N2 molecules and low hydrogenation barrier. The proposed strategy of engineering electrochemical catalysts and devices provides powerful guidelines for achieving industrial-level green ammonia production.

Identification and Characterization of a Potential Probiotic, Clostridium butyricum G13, Isolated from the Intestine of the Mud Crab (Scylla paramamosain)

The butyrate-producing bacterium Clostridium butyricum has been proven to be important in improving the growth and health benefits of aquatic animals. In this study, C. butyricum G13 was isolated for the first time from the gut of the mud crab (Scylla paramamosain). The results of this study showed that C. butyricum G13 could produce a high concentration of butyric acid and grow well in a wide range of pHs (4 to 9) and NaCl (1 to 2.5%) and bile salt (0.2 to 1.0%) concentrations. In vitro characterization revealed that C. butyricum G13 is a Gram-positive and gamma-hemolytic bacterium sensitive to most antibiotics and shows hydrophobicity and the capacity to degrade starch. In vitro fermentation using mud crab gut contents showed that C. butyricum G13 alone or in combination with galactooligosaccharides (GOS) and/or resistant starch (RS) significantly increased butyric acid production and beneficially affected the abundance and diversity of intestinal microbiota. In addition, C. butyricum G13 can improve the survival rate of mud crabs and effectively maintain the normal structure of gut morphology after infection with Vibrio parahaemolyticus. In conclusion, C. butyricum G13 can be considered a potential probiotic that improves the immune capacity and confers health benefits on mud crabs. IMPORTANCE With the development of society, more and more aquatic animals are demanded. Intensification in the aquaculture scale is facing problems, such as disease outbreaks, eutrophication of water bodies, and misuse of antibiotics. Among these challenges, disease outbreak is the most important factor directly affecting aquaculture production. It is crucial to explore new approaches effective for the prevention and control of diseases. Probiotics have been widely used in aquaculture and have shown beneficial effects on the host. In this study, the butyrate-producing bacterium Clostridium butyricum G13 was isolated for the first time from the intestine of the mud crab through in vitro fermentation. The bacterium has probiotic properties and changes the gut microbiota to be beneficial to hosts in vitro as well as protecting hosts from Vibrio parahaemolyticus infection in vivo. The outcomes of this study indicate that C. butyricum G13 can be used as a potential probiotic in mud crab aquaculture.

Two Novel Adenovirus Vectors Mediated Differential Antibody Responses via Interferon-α and Natural Killer Cells

Recombinant adenovirus vectors have been widely used in vaccine development. To overcome the preexisting immunity of human adenovirus type 5 (Ad5) in populations, a range of chimpanzee or rare human adenovirus vectors have been generated. However, these novel adenovirus vectors mediate the diverse immune responses in the hosts. In this study, we explored the immune mechanism of differential antibody responses to SARS-CoV-2 S protein in mice immunized by our previously developed two novel simian adenovirus type 23 (Sad23L) and human adenovirus type 49 (Ad49L), and Ad5 vectored COVID-19 vaccines. Sad23L-nCoV-S and Ad5-nCoV-S vaccines induced the low level of interferon-α (IFN-α) and the high level of antigen-specific antibody responses in wild-type and IFN-α/β receptor defective (IFNAR-/-) C57 mice, while Ad49L-nCoV-S vaccine induced the high IFN-α and low antibody responses in C57 mice but the high antibody response in IFNAR-/- mice. In addition, the high antibody response was detected in natural killer (NK) cells-blocked but the low in follicular helper T (TFH) cells -blocked C57 mice immunized with Ad49L-nCoV-S vaccine. These results showed that Ad49L vectored vaccine stimulated IFN-α secretion to activate NK cells, and then reduced the number of TFH cells, generation center (GC) B cells and plasma cells, and subsequently reduced antigen-specific antibody production. The different novel adenovirus vectors could be selected for vaccine development according to the need for either humoral or cellular or both immune protections against a particular disease. IMPORTANCE Novel adenovirus vectors are an important antigen delivery platform for vaccine development. Understanding the immune diversity between different adenoviral vectors is critical to design the proper vaccine against an aim disease. In this study, we described the immune mechanism of Sad23L and Ad49L vectored vaccines for raising the equally high specific T cell response but the different level of specific antibody responses in mice. We found that Ad49L-vectored vaccine initiated the high IFN-α and activated NK cells to inhibit antibody response via downregulating the number of CD4+ TFH cells leading to the decline of GC B cells and plasma cells.

Regulation of local alternating electric fields on synaptic plasticity in brain tissue

Purpose

External electric fields can regulate the neural network and change the excitability of the in-vivo cerebral cortex. Here, to prove the effect of alternating electric fields on the synaptic plasticity of ex-vivo tissues, the regular changes in the synaptic structure under alternating electric fields were studied.

Methods

This study applied alternating electric fields with a peak voltage of 20 V and frequencies of 5, 20, 50, and 80 Hz to the porcine cerebral cortex. Relying on transmission electron microscopy (TEM), the ultrastructure of synapses was observed, and the curvature radius of post-synaptic density (PSD) and the synaptic gap distance was quantified.

Results

The results indicated that under alternating electric fields, the average synaptic curvature of the PSD decreased by 30-59% with increasing frequency, and the average synaptic gap distance became narrower.

Conclusion

In ex-vivo brain tissue, synaptic plasticity can be regulated by alternating electric fields of different frequencies. This study can provide reference data for the storage and regulation of ex-vivo organs, as well as comparable data for in-vivo studies.

Cathepsin S deficiency improves muscle mass loss and dysfunction via the modulation of protein metabolism in mice under pathological stress conditions

Cathepsin S (CTSS) is a widely expressed cysteinyl protease that has garnered attention because of its enzymatic and non-enzymatic functions under inflammatory and metabolic pathological conditions. Here, we examined whether CTSS participates in stress-related skeletal muscle mass loss and dysfunction, focusing on protein metabolic imbalance. Eight-week-old male wildtype (CTSS^+/+ ) and CTSS-knockout (CTSS^-/- ) mice were randomly assigned to non-stress and variable-stress groups for 2 weeks, and then processed for morphological and biochemical studies. Compared with non-stressed mice, stressed CTSS^+/+ mice showed significant losses of muscle mass, muscle function, and muscle fiber area. In this setting, the stress-induced harmful changes in the levels of oxidative stress-related (gp91^phox and p22^phox ,), inflammation-related (SDF-1, CXCR4, IL-1β, TNF-α, MCP-1, ICAM-1, and VCAM-1), mitochondrial biogenesis-related (PPAR-γ and PGC-1α) genes and/or proteins and protein metabolism-related (p-PI3K, p-Akt, p-FoxO3α, MuRF-1, and MAFbx1) proteins; and these alterations were rectified by CTSS deletion. Metabolomic analysis revealed that stressed CTSS^-/- mice exhibited a significant improvement in the levels of glutamine metabolism pathway products. Thus, these findings indicated that CTSS can control chronic stress-related skeletal muscle atrophy and dysfunction by modulating protein metabolic imbalance, and thus CTSS was suggested to be a promising new therapeutic target for chronic stress-related muscular diseases.

Cross-Platform Transcriptomic Data Integration, Profiling, and Mining in Vibrio cholerae

A large number of transcriptome studies generate important data and information for the study of pathogenic mechanisms of pathogens, including Vibrio cholerae. V. cholerae transcriptome data include RNA-seq and microarray: microarray data mainly include clinical human and environmental samples, and RNA-seq data mainly focus on laboratory processing conditions, including different stresses and experimental animals in vivo. In this study, we integrated the data sets of both platforms using Rank-in and the Limma R package normalized Between Arrays function, achieving the first cross-platform transcriptome data integration of V. cholerae. By integrating the entire transcriptome data, we obtained the profiles of the most active or silent genes. By transferring the integrated expression profiles into the weighted correlation network analysis (WGCNA) pipeline, we identified the important functional modules of V. cholerae in vitro stress treatment, gene manipulation, and in vitro culture as DNA transposon, chemotaxis and signaling, signal transduction, and secondary metabolic pathways, respectively. The analysis of functional module hub genes revealed the uniqueness of clinical human samples; however, under specific expression patterning, the Δhns, ΔoxyR1 strains, and tobramycin treatment group showed high expression profile similarity with human samples. By constructing a protein-protein interaction (PPI) interaction network, we discovered several unreported novel protein interactions within transposon functional modules. IMPORTANCE We used two techniques to integrate RNA-seq data for laboratory studies with clinical microarray data for the first time. The interactions between V. cholerae genes were obtained from a global perspective, as well as comparing the similarity between clinical human samples and the current experimental conditions, and uncovering the functional modules that play a major role under different conditions. We believe that this data integration can provide us with some insight and basis for elucidating the pathogenesis and clinical control of V. cholerae.

Oral Probiotic Expressing Human Ethanol Dehydrogenase Attenuates Damage Caused by Acute Alcohol Consumption in Mice

Alcohol is an essential drug in human life with multiple medical functions, but excessive alcohol intake, even a single episode of binge drinking, can cause serious damage. Reducing alcohol consumption or absorption is a direct way to alleviate the related harm. Alcohol is decomposed successively by alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) in the liver. Here, we produced a human ADH1B (hADH1B)-expressing probiotic, a recombinant Lactococcus lactis, that aimed to enhance alcohol degradation in the intestinal tract after oral administration. Our results showed that the oral hADH1B-expressing probiotic reduced alcohol absorption, prolonged the alcohol tolerance time, and shortened the recovery time after acute alcohol challenge. More importantly, the liver and intestine were protected from acute injury caused by alcohol challenge. Therefore, the engineered probiotic has the potential to protect organ damage from alcohol consumption. Furthermore, this engineered probiotic may have beneficial effects on alcohol-related diseases such as alcoholic fatty liver disease. IMPORTANCE Alcohol plays an important role in medical treatment, culture, and social interaction. However, excessive alcohol consumption or improper alcohol intake patterns can lead to serious damage to health. Aiming to reduce the harm of alcohol consumption, we designed a recombinant probiotic expressing hADH1B. Our results showed that this recombinant probiotic can reduce alcohol absorption and protect the body from alcohol damage, including hangover, liver, and intestinal damage. Reducing alcohol damage is helpful to the health of people with difficulty in abstinence. The engineered probiotic may provide new strategies for treatment and prevention of the negative effects of alcohol, and it also has the potential for widespread application.

A Nationwide Genomic Study of Clinical Klebsiella pneumoniae Carrying blaOXA-232 and rmtF in China

OXA-232 carbapenemase is becoming a threat in China due to its high prevalence, mortality, and limited treatment options. However, little information is available on the impact of OXA-232-producing Klebsiella pneumoniae in China. This study aims to characterize the clonal relationships, the genetic mechanisms of resistance, and the virulence of OXA-232-producing K. pneumoniae isolates in China. We collected 81 OXA-232-producing K. pneumoniae clinical isolates from 2017 to 2021. Antimicrobial susceptibility testing was performed using the broth microdilution method. Capsular types, multilocus sequence types, virulence genes, antimicrobial resistance (AMR) determinants, plasmid replicon types, and single-nucleotide polymorphism (SNP) phylogeny were inferred from whole-genome sequences. OXA-232-producing K. pneumoniae strains were resistant to most antimicrobial agents. These isolates showed partial differences in susceptibility to carbapenems: all strains were resistant to ertapenem, while the resistance rates to imipenem and meropenem were 67.9% and 97.5%, respectively. Sequencing and capsular diversity analysis of the 81 K. pneumoniae isolates revealed 3 sequence types (ST15, ST231, and one novel ST [ST-V]), 2 K-locus types (KL112 and KL51), and 2 O-locus types (O2V1 and O2V2). The predominant plasmid replicon types associated with the OXA-232 and rmtF genes were ColKP3 (100%) and IncFIB-like (100%). Our study summarized the genetic characteristics of OXA-232-producing K. pneumoniae circulating in China. The results demonstrate the practical applicability of genomic surveillance and its utility in providing methods to prevent transmission. It alerts us to the urgent need for longitudinal surveillance of these transmissible lineages. IMPORTANCE In recent years, the detection rate of carbapenem-resistant K. pneumoniae has increased and represents a major threat to clinical anti-infective therapy. Compared with KPC-type carbapenemases and NDM-type metallo-β-lactamases, OXA-48 family carbapenemases are another important resistance mechanism mediating bacterial resistance to carbapenems. In this study, we investigated the molecular characteristics of OXA-232 carbapenemase-producing K. pneumoniae isolated from several hospitals to clarify the epidemiological dissemination characteristics of such drug-resistant strains in China.

Imaging of pH distribution inside individual microdroplet by stimulated Raman microscopy

Aerosol microdroplets as microreactors for many important atmospheric reactions are ubiquitous in the atmosphere. pH largely regulates the chemical processes within them; however, how pH and chemical species spatially distribute within an atmospheric microdroplet is still under intense debate. The challenge is to measure pH distribution within a tiny volume without affecting the chemical species distribution. We demonstrate a method based on stimulated Raman scattering microscopy to visualize the three-dimensional pH distribution inside single microdroplets of varying sizes. We find that the surface of all microdroplets is more acidic, and a monotonic trend of pH decreasing is observed in the 2.9-μm aerosol microdroplet from center to edge, which is well supported by molecular dynamics simulation. However, bigger cloud microdroplet differs from small aerosol for pH distribution. This size-dependent pH distribution in microdroplets can be related to the surface-to-volume ratio. This work presents noncontact measurement and chemical imaging of pH distribution in microdroplets, filling the gap in our understanding of spatial pH in atmospheric aerosol.

Nanoelectrochemistry reveals how soluble Aβ42 oligomers alter vesicular storage and release of glutamate

Glutamate (Glu) is the major excitatory transmitter in the nervous system. Impairment of its vesicular release by β-amyloid (Aβ) oligomers is thought to participate in pathological processes leading to Alzheimer's disease. However, it remains unclear whether soluble Aβ42 oligomers affect intravesicular amounts of Glu or their release in the brain, or both. Measurements made in this work on single Glu varicosities with an amperometric nanowire Glu biosensor revealed that soluble Aβ42 oligomers first caused a dramatic increase in vesicular Glu storage and stimulation-induced release, accompanied by a high level of parallel spontaneous exocytosis, ultimately resulting in the depletion of intravesicular Glu content and greatly reduced release. Molecular biology tools and mouse models of Aβ amyloidosis have further established that the transient hyperexcitation observed during the primary pathological stage is mediated by an altered behavior of VGLUT1 responsible for transporting Glu into synaptic vesicles. Thereafter, an overexpression of Vps10p-tail-interactor-1a, a protein that maintains spontaneous release of neurotransmitters by selective interaction with t-SNAREs, resulted in a depletion of intravesicular Glu content, triggering advanced-stage neuronal malfunction. These findings are expected to open perspectives for remediating Aβ42-induced neuronal hyperactivity and neuronal degeneration.

Improving Theaflavin-3,3'-digallate Production Efficiency Optimization by Transition State Conformation of Polyphenol Oxidase

Theaflavins (TFs) are good for health because of their bioactivities. Enzymatic synthesis of TFs has garnered much attention; however, the source and activity of the enzymes needed limit their wide application. In this study, a microbial polyphenol oxidase from Bacillus megaterium was screened for the synthesis of theaflavin-3,3'-digallate (TFDG). Based on structural and mechanistic analyses of the enzyme, the O-O bond dissociation was identified as the rate-determining step. To address this issue, a transition state (TS) conformation optimization strategy was adopted to stabilize the spatial conformation of the O-O bond dissociation, which improved the catalytic efficiency of tyrosinase. Under the optimum transformation conditions of pH 4.0, temperature 25 °C, (-)-epigallocatechin gallate/epicatechin gallate molar ratio of 2:1, and time of 30 min, Mu₄ (BmTyr^V218A/R209S) produced 960.36 mg/L TFDG with a 44.22% conversion rate, which was 6.35-fold higher than that of the wild type. Thus, the method established has great potential in the synthesis of TFDG and other TFs.

Porcine Enteric Alphacoronavirus Entry through Multiple Pathways (Caveolae, Clathrin, and Macropinocytosis) Requires Rab GTPases for Endosomal Transport

Porcine enteric alphacoronavirus (PEAV) is a new bat HKU2-like porcine coronavirus, and its endemic outbreak has caused severe economic losses to the pig industry. Its broad cellular tropism suggests a potential risk of cross-species transmission. A limited understanding of PEAV entry mechanisms may hinder a rapid response to potential outbreaks. This study analyzed PEAV entry events using chemical inhibitors, RNA interference, and dominant-negative mutants. PEAV entry into Vero cells depended on three endocytic pathways: caveolae, clathrin, and macropinocytosis. Endocytosis requires dynamin, cholesterol, and a low pH. Rab5, Rab7, and Rab9 GTPases (but not Rab11) regulate PEAV endocytosis. PEAV particles colocalize with EEA1, Rab5, Rab7, Rab9, and Lamp-1, suggesting that PEAV translocates into early endosomes after internalization, and Rab5, Rab7, and Rab9 regulate trafficking to lysosomes before viral genome release. PEAV enters porcine intestinal cells (IPI-2I) through the same endocytic pathway, suggesting that PEAV may enter various cells through multiple endocytic pathways. This study provides new insights into the PEAV life cycle. IMPORTANCE Emerging and reemerging coronaviruses cause severe human and animal epidemics worldwide. PEAV is the first bat-like coronavirus to cause infection in domestic animals. However, the PEAV entry mechanism into host cells remains unknown. This study demonstrates that PEAV enters into Vero or IPI-2I cells through caveola/clathrin-mediated endocytosis and macropinocytosis, which does not require a specific receptor. Subsequently, Rab5, Rab7, and Rab9 regulate PEAV trafficking from early endosomes to lysosomes, which is pH dependent. The results advance our understanding of the disease and help to develop potential new drug targets against PEAV.

Ultra-high-efficiency capture of lead ions over acetylenic bond-rich graphdiyne adsorbent in aqueous solution

A satisfactory material with high adsorption capacity is urgently needed to solve the serious problem of environment and human health caused by lead pollution. Herein, hydrogen-substituted graphdiyne (HsGDY) was successfully fabricated and employed to remove lead ions from sewage and lead-containing blood. The as-prepared HsGDY exhibits the highest adsorption capacity of lead among the reported materials with a maximum adsorption capacity of 2,390 mg/g, i.e., ~five times larger than that of graphdiyne (GDY). The distinguished hexagonal hole and stack mode of HsGDY allows the adsorption of more lead via its inner side adsorption mode in one single unit space. In addition, the Pb 6s and H 1s hybridization promotes the strong bonding of lead atom adsorbed at the acetylenic bond of HsGDY, contributing to the high adsorption capacity. HsGDY can be easily regenerated by acid treatment and showed excellent regeneration ability and reliability after six adsorption-regeneration cycles. Langmuir isotherm model, pseudo second order, and density functional theory (DFT) demonstrated that the lead adsorption process in HsGDY is monolayer chemisorption. Furthermore, the HsGDY-based portable filter can handle 1,000 μg/L lead-containing aqueous solution up to 1,000 mL, which is nearly 6.67 times that of commercial activated carbon particles. And, the HsGDY shows good biocompatibility and excellent removal efficiency to 100 μg/L blood lead, which is 1.7 times higher than that of GDY. These findings suggest that HsGDY could be a promising adsorbent for practical lead and other heavy metal removal.

Spontaneous dark formation of OH radicals at the interface of aqueous atmospheric droplets

Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo)chemical processes, uptake from gaseous OH, or related to interfacial O3 and NO3 radical-driven chemistry. Here, we present experimental evidence that OH radicals are spontaneously produced at the air-water interface of aqueous droplets in the dark and the absence of known precursors, possibly due to the strong electric field that forms at such interfaces. The measured OH production rates in atmospherically relevant droplets are comparable to or significantly higher than those from known aqueous bulk sources, especially in the dark. As aqueous droplets are ubiquitous in the troposphere, this interfacial source of OH radicals should significantly impact atmospheric multiphase oxidation chemistry, with substantial implications on air quality, climate, and health.

Serotonin/5-HT7 receptor provides an adaptive signal to enhance pigmentation response to environmental stressors through cAMP-PKA-MAPK, Rab27a/RhoA, and PI3K/AKT signaling pathways

Serotonin (5-HT), a neurotransmitter, is essential for normal and pathological pigmentation processing, and its receptors may be therapeutical targets. The effect and behavior of the 5-HT7 receptor (5-HT7R) in melanogenesis in high vertebrates remain unknown. Herein, we examine the role and molecular mechanism of 5-HT7R in the pigmentation of human skin cells, human tissue, mice, and zebrafish models. Firstly, 5-HT7R protein expression decreased significantly in stress-induced depigmentation skin and vitiligo epidermis. Stressed mice received transdermal serotonin 5-HT7R selective agonists (LP-12, 0.01%) for 12 or 60 days. Mice might recover from persistent stress-induced depigmentation. The downregulation of tyrosinase (Tyr), microphthalmia-associated transcription factor (Mitf) expression, and 5-HT7R was consistently restored in stressed skin. High-throughput RNA sequencing showed that structural organization (dendrite growth and migration) and associated pathways were activated in the dorsal skin of LP-12-treated animals. 5-HT7R selective agonist, LP-12, had been demonstrated to enhance melanin production, dendrite growth, and chemotactic motility in B16F10 cells, normal human melanocytes (NHMCs), and zebrafish. Mechanistically, the melanogenic, dendritic, and migratory functions of 5-HT7R were dependent on the downstream signaling of cAMP-PKA-ERK1/2, JNK MAPK, RhoA/Rab27a, and PI3K/AKT pathway activation. Importantly, pharmacological inhibition and genetic siRNA of 5-HT7R by antagonist SB269970 partially/completely abolished these functional properties and the related activated pathways in both NHMCs and B16F10 cells. Consistently, htr7a/7b genetic knockdown in zebrafish could blockade melanogenic effects and abrogate 5-HT-induced melanin accumulation. Collectively, we have first identified that 5-HT7R regulates melanogenesis, which may be a targeted therapy for pigmentation disorders, especially those worsened by stress.

The adverse impact of ecotropic viral integration site-1 (EVI1) overexpression on the prognosis of acute myeloid leukemia with KMT2A gene rearrangement in different risk stratification subtypes

INTRODUCTION

AML patients with KMT2A-MLLT3 and other 11q23 abnormalities belong to the intermediate and high-risk level groups, respectively. Whether the poor prognostic value of Ecotropic Viral Integration site-1 (EVI1) overexpression suits either the subtypes of KMT2A-MLLT3 or Non-KMT2A-MLLT3 AML patients (intermediate and high risk group) needs to be further investigated.

METHODS

We retrospectively analyzed the clinical characteristics of 166 KMT2A-r and KMT2A-PTD AML patients.

RESULTS

For the Non-KMT2A-MLLT3 group, patients in the EVI1-high subgroup had shorter OS and DFS and higher CIR than those in the EVI1-low subgroup (p = .027, p = .018, and p = .020, respectively). Additionally, both KMT2A-MLLT3 and Non-KMT2A-MLLT3 patients who received chemotherapy alone had poorer prognosis than patients who also received allogeneic hematopoietic stem cell transplant (allo-HSCT) regardless of their EVI1 expression level (all p < .001). For transplanted patients with KMT2A-MLLT3 or Non-KMT2A-MLLT3 rearrangement, the EVI1-high subgroup had worse prognosis than the EVI1-low subgroup (all p < .05). The 2-year CIR of the KMT2A-MLLT3 and Non-KMT2A-MLLT3 groups with high EVI1 expression was high (52% and 49.6%, respectively). However, for patients with low EVI1 expression, the 2-year CIR of transplanted patients with KMT2A-MLLT3 and Non-KMT2A-MLLT3 was relatively low.

CONCLUSIONS

Our study showed that for the Non-KMT2A-MLLT3 group, the EVI1-high group had shorter OS and DFS than the EVI1-low group. High EVI1 expression showed an adverse effect in AML with KMT2A rearrangement in different risk stratification subtypes. For the EVI1-high patients with non-KMT2A-MLLT3 rearrangement, other novel regimens towards relapse should be taken into consideration.

Key Residue in the Precursor Region of M Protein Contributes to the Neurovirulence and Neuroinvasiveness of the African Lineage of Zika Virus

The Zika virus (ZIKV) represents an important global health threat due to its unusual association with congenital Zika syndrome. ZIKV strains are phylogenetically grouped into the African and Asian lineages. However, the viral determinants underlying the phenotypic differences between the lineages remain unknown. Here, multiple sequence alignment revealed a highly conserved residue at position 21 of the premembrane (prM) protein, which is glutamic acid and lysine in the Asian and African lineages, respectively. Using reverse genetics, we generated a recombinant virus carrying an E21K mutation based on the genomic backbone of the Asian lineage strain FSS13025 (termed E21K). The E21K mutation significantly increased viral replication in multiple neural cell lines with a higher ratio of M to prM production. Animal studies showed E21K exhibited increased neurovirulence in suckling mice, leading to more severe defects in mouse brains by causing more neural cell death and destruction of hippocampus integrity. Moreover, the E21K substitution enhanced neuroinvasiveness in interferon alpha/beta (IFN-α/β) receptor knockout mice, as indicated by the increased mortality, and enhanced replication in mouse brains. The global transcriptional analysis showed E21K infection profoundly altered neuron development networks and induced stronger antiviral immune response than wild type (WT) in both neural cells and mouse brains. More importantly, the reverse K21E mutation based on the genomic backbone of the African strain MR766 caused less mouse neurovirulence. Overall, our findings support the 21st residue of prM functions as a determinant for neurovirulence and neuroinvasiveness of the African lineage of ZIKV. IMPORTANCE The suspected link of Zika virus (ZIKV) to birth defects led the World Health Organization to declare ZIKV a Public Health Emergency of International Concern. ZIKV has been identified to have two dominant phylogenetic lineages, African and Asian. Significant differences exist between the two lineages in terms of neurovirulence and neuroinvasiveness in mice. However, the viral determinants underlying the phenotypic differences are still unknown. Here, combining reverse genetics, animal studies, and global transcriptional analysis, we provide evidence that a single E21K mutation of prM confers to the Asian lineage strain FSS130125 significantly enhanced replication in neural cell lines and more neurovirulent and neuroinvasiveness phenotypes in mice. Our findings support that the highly conserved residue at position 21 of prM functions as a determinant of neurovirulence and neuroinvasiveness of the African lineage of ZIKV in mice.

Membrane Protein Amuc_1100 Derived from Akkermansia muciniphila Facilitates Lipolysis and Browning via Activating the AC3/PKA/HSL Pathway

Obesity, defined as a disorder of lipid metabolism caused by white fat accumulation, is closely related to the gut microbiota. Akkermansia muciniphila (Akk), one of the most common gut commensals, can reduce fat storage and promote the browning of white adipocytes, alleviating disorders of lipid metabolism. However, which components of Akk produce the effect remain unclear, limiting the application of Akk in the treatment of obesity. Here, we found that the membrane protein Amuc_1100 of Akk decreased formation of lipid droplets and fat accumulation during the differentiation process and stimulated browning in vivo and in vitro. Transcriptomics revealed that Amuc_1100 accelerated lipolysis through upregulation of the AC3/PKA/HSL pathway in 3T3-L1 preadipocytes. Quantitative PCR (qPCR) and Western blotting showed that Amuc_1100 intervention promotes steatolysis and browning of preadipocytes by increasing lipolysis-related genes (AC3/PKA/HSL) and brown adipocyte marker genes (PPARγ, UCP1, and PGC1α) at both the mRNA and protein levels. These findings introduce new insight into the effects of beneficial bacteria and provide new avenues for the treatment of obesity. IMPORTANCE An important intestinal bacterial strain Akkermansia muciniphila contributes to improving carbohydrate and lipid metabolism, thus alleviating obesity symptoms. Here, we find that the Akk membrane protein Amuc_1100 regulates lipid metabolism in 3T3-L1 preadipocytes. Amuc_1100 inhibits lipid adipogenesis and accumulation during the differentiation process of preadipocytes, upregulates the browning-related genes of preadipocytes, and promotes thermogenesis through activation of uncoupling protein-1 (UCP-1), including Acox1 involved in lipid oxidation. Amuc_1100 accelerates lipolysis via the AC3/PKA/HSL pathway, phosphorylating HSL at Ser 660. The experiments illustrated here identify the specific molecules and functional mechanisms of Akk. Therapeutic approaches with Amuc_1100 derived from Akk may help alleviate obesity and metabolic disorders.

Design and synthesis of a small molecular NIR-II chemiluminescence probe for in vivo-activated H2S imaging

Chemiluminescence (CL) with the elimination of excitation light and minimal autofluorescence interference has been wieldy applied in biosensing and bioimaging. However, the traditional emission of CL probes was mainly in the range of 400 to 650 nm, leading to undesired resolution and penetration in a biological object. Therefore, it was urgent to develop CL molecules in the near-infrared window [NIR, including NIR-I (650 to 900 nm) and near-infrared-II (900 to 1,700 nm)], coupled with unique advantages of long-time imaging, sensitive response, and high resolution at depths of millimeters. However, no NIR-II CL unimolecular probe has been reported until now. Herein, we developed an H2S-activated NIR-II CL probe [chemiluminiscence donor 950, (CD-950)] by covalently connecting two Schaap's dioxetane donors with high chemical energy to a NIR-II fluorophore acceptor candidate via intramolecular CL resonance energy transfer strategy, thereby achieving high efficiency of 95%. CD-950 exhibited superior capacity including long-duration imaging (~60 min), deeper tissue penetration (~10 mm), and specific H2S response under physiological conditions. More importantly, CD-950 showed detection capability for metformin-induced hepatotoxicity with 2.5-fold higher signal-to-background ratios than that of NIR-II fluorescence mode. The unimolecular NIR-II CL probe holds great potential for the evaluation of drug-induced side effects by tracking its metabolites in vivo, further facilitating the rational design of novel NIR-II CL-based detection platforms.

A Novel CMY Variant Confers Transferable High-Level Resistance to Ceftazidime-Avibactam in Multidrug-Resistant Escherichia coli

Here, our objective was to explore the molecular mechanism underlying ceftazidime-avibactam resistance in a novel CMY-178 variant produced by the clinical Escherichia coli strain AR13438. The antibiotic susceptibility of the clinical isolate, its transconjugants, and its transformants harboring transferable blaCMY were determined by the agar dilution method. S1-PFGE, cloning experiments, and whole-genome sequencing (WGS) were performed to investigate the molecular characteristics of ceftazidime-avibactam resistance genes. Kinetic parameters were compared among the purified CMY variants. Structural modeling and molecular docking were performed to assess the affinity between the CMYs and drugs. The horizontal transferability of the plasmid was evaluated by a conjugation experiment. The fitness cost of the plasmid was analyzed by determining the maximal growth rate, the maximum optical density at 600 nm (OD600), and the duration of the lag phase. AR13438, a sequence type 457 E. coli strain, was resistant to multiple cephalosporins, piperacillin-tazobactam, and ceftazidime-avibactam at high levels and was susceptible to carbapenems. WGS and cloning experiments indicated that a novel CMY gene, blaCMY-178, was responsible for ceftazidime-avibactam resistance. Compared with the closely related CMY-172, CMY-178 had a nonsynonymous amino acid substitution at position 70 (Asn70Thr). CMY-178 increased the MICs of multiple cephalosporins and ceftazidime-avibactam compared with CMY-172. The kinetic constant Ki values of CMY-172 and CMY-178 against tazobactam were 2.12 ± 0.34 and 2.49 ± 0.51 μM, respectively. Structural modeling and molecular docking indicated a narrowing of the CMY-178 ligand-binding pocket and its entrance and a stronger positive charge at the pocket entrance compared with those observed with CMY-172. blaCMY-178 was located in a 96.9-kb IncI1-type plasmid, designated pAR13438_2, which exhibited high transfer frequency without a significant fitness cost. In conclusion, CMY-178 is a novel CMY variant that mediates high-level resistance to ceftazidime-avibactam by enhancing the ability to hydrolyze ceftazidime and reducing the affinity for avibactam. Notably, blaCMY-178 could be transferred horizontally at high frequency without fitness costs. IMPORTANCE Ceftazidime-avibactam is a novel β-lactam-β-lactamase inhibitor (BLBLI) combination with powerful activity against Enterobacterales isolates producing AmpC, such as CMY-like cephalosporinase. However, in recent years, CMY variants have been reported to confer ceftazidime-avibactam resistance. We reported a novel CMY variant, CMY-178, that confers high-level ceftazidime-avibactam resistance with potent transferability. Therefore, this resistance gene is a tremendous potential menace to public health and needs attention of clinicians.