Glucosamine-6-phosphate synthase--the multi-facets enzyme

Generation and validation of a versatile inducible multiplex CRISPRi system to examine bacterial regulation in the Euprymna-Vibrio fischeri symbiosis

The Vibrio fischeri-Euprymna scolopes symbiosis has become a powerful animal-microbe model system to examine the genetic underpinnings of symbiont development and regulation. Although there has been a number of elegant bacterial genetic technologies developed to examine this symbiosis, there is still a need to develop more sophisticated methodologies to better understand complex regulatory pathways that lie within the association. Therefore, we have developed a suite of CRISPR interference (CRISPRi) vectors for inducible repression of specific V. fischeri genes associated with symbiotic competence. The suite utilizes both Tn7-integrating and shuttle vector plasmids that allow for inducible expression of CRISPRi dCas9 protein along with single-guide RNAs (sgRNA) modules. We validated this CRISPRi tool suite by targeting both exogenous (an introduced mRFP reporter) and endogenous genes (luxC in the bioluminescence producing lux operon, and flrA, the major regulatory gene controlling flagella production). The suite includes shuttle vectors expressing both single and multiple sgRNAs complementary to the non-template strand of multiple targeted genetic loci, which were effective in inducible gene repression, with significant reductions in targeted gene expression levels. V. fischeri cells harboring a version of this system targeting the luxC gene and suppressing the production of luminescence were used to experimentally validate the hypothesis that continuous luminescence must be produced by the symbiont in order to maintain the symbiosis at time points longer than the known 24-h limit. This robust new CRISPRi genetic toolset has broad utility and will enhance the study of V. fischeri genes, bypassing the need for gene disruptions by standard techniques of allelic knockout-complementation-exchange and the ability to visualize symbiotic regulation in vivo.

Coordinated Transcriptional Increases in Cell Wall Synthesis Genes in Neisseria gonorrhoeae Lacking the Lytic Transglycosylase, ltgA

Lytic transglycosylase A in Neisseria gonorrhoeae cleaves the β-1,4-glycosidic bond between peptidoglycan (PG) monomers to liberate 1,6-anhydro-PG fragments that are either recycled or released as cytotoxic fragments. To gain further insight into the effect of LtgA on cellular processes in Neisseria gonorrhoeae, we performed a proteomic analysis comparing wild-type and an isogenic ltgA null mutant strain. Proteins were separated by two-dimensional gel electrophoresis and identified by MALDI-TOF mass spectrometry, which revealed several proteins that were increased in their level of expression upon loss of LtgA. The most notable changes corresponded to enzymes related to aminosugar and pyrimidine metabolism. Quantitative real-time RT-PCR of mRNA from a ltgA null strain confirmed increased transcription of genes encoding enzymes involved in UDP-N-acetylglucosamine (UDP-GlcNAc) synthesis, a major precursor in PG and lipooligosaccharide (LOS) synthesis, during normal growth conditions and following exposure to penicillin. We also found that the ltgA mutant strains were more susceptible to β-lactam antibiotics, vancomycin, and the human-cathelicidin antibacterial peptide, LL-37, than their corresponding wild-type parental strains. Our results suggest that increased expression of enzymes responsible for production UDP-GlcNAc is an adaptive response due to inactivation of ltgA and/or exposure to penicillin.

High-Efficiency CRISPR-Cas9 Genome Editing Unveils Biofilm Insights and Enhances Antimicrobial Activity in Bacillus velezensis FZB42

Bacillus velezensis FZB42 is a prominent plant growth-promoting rhizobacterium and biocontrol agent known for producing a wide array of antimicrobial compounds. The capability to genetically manipulate this strain would facilitate understanding its metabolism and enhancing its sustainable agriculture applications. In this study, we report the first successful implementation of high-efficiency CRISPR-Cas9 genome editing in B. velezensis FZB42, enabling targeted genetic modifications to gain insights into its plant growth-promotion and biocontrol properties. Deletion of the slrR gene, a key regulator of biofilm formation, resulted in significant alterations in biofilm structure and development, as demonstrated by scanning electron microscopy and quantitative biofilm assays. These findings provide valuable insights into the mechanisms of biofilm formation, which are critical for root colonization and plant growth promotion. Additionally, we overexpressed the bac gene cluster responsible for bacilysin biosynthesis by replacing its native promoter with the strong constitutive promoter P43 and integrating an additional copy of the bacG gene. This genetic manipulation led to a 2.7-fold increase in bacB gene expression and significantly enhanced antibacterial activity against Escherichia coli and Lactobacillus diolivorans. The successful implementation of the CRISPR-Cas9 system for genome editing in FZB42 provides a valuable tool for genetic engineering, with the potential to improve its biocontrol efficacy and broaden its applications in agriculture and other biotechnology areas. Our principles and procedures are broadly applicable to other agriculturally significant microorganisms.

Cys-tRNAj as a Second Translation Initiator for Priming Proteins with Cysteine in Bacteria

We report the construction of an alternative protein priming system to recode genetic translation in Escherichia coli by designing, through trial and error, a chimeric initiator whose sequence identity points partly to elongator tRNACys and partly to initiator tRNAf Met. The elaboration of a selection based on the N-terminal cysteine imperative for the function of glucosamine-6-phosphate synthase, an essential enzyme in bacterial cell wall synthesis, was a crucial step to achieve the engineering of this Cys-tRNAj. Iterative improvement of successive versions of Cys-tRNAj was corroborated in vitro by using a biochemical luciferase assay and in vivo by selecting for translation priming of E. coli thymidylate synthase. Condensation assays using specific fluorescent reagent FITC-Gly-cyanobenzothiazole provided biochemical evidence of cysteine coding at the protein priming stage. We showed that translation can be initiated, by N-terminal incorporation of cysteine, at a codon other than UGC by expressing a tRNAj with the corresponding anticodon. The optimized tRNAj is now available to recode the priming of an arbitrary subset of proteins in the bacterial proteome with absolute control of their expression and to evolve the use of xenonucleotides and the emergence of a tXNAj in vivo.

The role of protein O-GlcNAcylation in diabetic cardiomyopathy

It is well established that diabetes markedly increases the risk of multiple types of heart disease including heart failure. However, despite substantial improvements in the treatment of heart failure in recent decades the relative increased risk associated with diabetes remains unchanged. There is increasing appreciation of the importance of the post translational modification by O-linked-N-acetylglucosamine (O-GlcNAc) of serine and threonine residues on proteins in regulating cardiomyocyte function and mediating stress responses. In response to diabetes there is a sustained increase in cardiac O-GlcNAc levels, which has been attributed to many of the adverse effects of diabetes on the heart. Here we provide an overview of potential mechanisms by which increased cardiac O-GlcNAcylation contributes to the adverse effects on the heart and highlight some of the key gaps in our knowledge.

Insights into the regulatory role of bacterial sncRNA and its extracellular delivery via OMVs

Small noncoding RNAs (sncRNAs) play important regulatory roles in bacterial physiological processes and host-pathogen interactions. Meanwhile, bacterial outer membrane vesicles (OMVs), as naturally secreted outer membrane structures, play a vital role in the interaction between bacteria and their living environment, including the host environment. However, most current studies focus on the biological functions of sncRNAs in bacteria or hosts, while neglecting the roles and regulatory mechanisms of the OMVs that encapsulate these sncRNAs. Therefore, this review aims to summarize the intracellular regulatory roles of bacterial sncRNAs in promoting pathogen survival by regulating virulence, modulating bacterial drug resistance, and regulating iron metabolism, and their extracellular regulatory function for influencing host immunity through host-pathogen interactions. Additionally, we introduce the key role played by OMVs, which serve as important cargoes in bacterial sncRNA-host interactions. We propose emerging pathways of sncRNA action to further discuss the mode of host-pathogen interactions, highlighting that the inhibition of sncRNA delivery by OMVs may prevent the occurrence of infection to some extent. Hence, this review lays the foundation for future prophylactic treatments against bacterial infections and strategies for addressing bacterial drug resistance. KEY POINTS: •sncRNAs have intracellular and extracellular regulatory functions in bacterial physiological processes and host-pathogen interactions. •OMVs are potential mediators between bacterial sncRNAs and host cells. •OMVs encapsulating sncRNAs have more potential biological functions.

Metabolite Profiling of Hydroponic Lettuce Roots Affected by Nutrient Solution Flow: Insights from Comprehensive Analysis Using Widely Targeted Metabolomics and MALDI Mass Spectrometry Imaging Approaches

Root morphology, an important determinant of nutrient absorption and plant growth, can adapt to various growth environments to promote survival. Solution flow under hydroponic conditions provides a mechanical stimulus, triggering adaptive biological responses, including altered root morphology and enhanced root growth and surface area to facilitate nutrient absorption. To clarify these mechanisms, we applied untargeted metabolomics technology, detecting 1737 substances in lettuce root samples under different flow rates, including 17 common differential metabolites. The abscisic acid metabolic pathway product dihydrophaseic acid and the amino and nucleotide sugar metabolism factor N-acetyl-d-mannosamine suggest that nutrient solution flow rate affects root organic acid and sugar metabolism to regulate root growth. Spatial metabolomics analysis of the most stressed root bases revealed significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways: "biosynthesis of cofactors" and "amino sugar and nucleotide sugar metabolism". Colocalization analysis of pathway metabolites revealed a flow-dependent spatial distribution, with higher flavin mononucleotide, adenosine-5'-diphosphate, hydrogenobyrinic acid, and D-glucosamine 6-phosphate under flow conditions, the latter two showing downstream-side enrichment. In contrast, phosphoenolpyruvate, 1-phospho-alpha-D-galacturonic acid, 3-hydroxyanthranilic acid, and N-acetyl-D-galactosamine were more abundant under no-flow conditions, with the latter two concentrated on the upstream side. As metabolite distribution is associated with function, observing their spatial distribution in the basal roots will provide a more comprehensive understanding of how metabolites influence plant morphology and response to environmental changes than what is currently available in the literature.

Discovery of metal-binding proteins by thermal proteome profiling

Metal-binding proteins (MBPs) have various and important biological roles in all living species and many human diseases are intricately linked to dysfunctional MBPs. Here, we report a chemoproteomic method named 'metal extraction-triggered agitation logged by thermal proteome profiling' (METAL-TPP) to globally profile MBPs in proteomes. The method involves the extraction of metals from MBPs using chelators and monitoring the resulting protein stability changes through thermal proteome profiling. Applying METAL-TPP to the human proteome with a broad-spectrum chelator, EDTA, revealed a group of proteins with reduced thermal stability that contained both previously known MBPs and currently unannotated MBP candidates. Biochemical characterization of one potential target, glutamine-fructose-6-phosphate transaminase 2 (GFPT2), showed that zinc bound the protein, inhibited its enzymatic activity and modulated the hexosamine biosynthesis pathway. METAL-TPP profiling with another chelator, TPEN, uncovered additional MBPs in proteomes. Collectively, this study developed a robust tool for proteomic discovery of MBPs and provides a rich resource for functional studies of metals in cell biology.

Caffeine-induced protein kinase A activation restores cognitive deficits induced by sleep deprivation by regulating O-GlcNAc cycling in adult zebrafish

Sleep deprivation (SD) is widely acknowledged as a significant risk factor for cognitive impairment. In this study, intraperitoneal caffeine administration significantly ameliorated the learning and memory (L/M) deficits induced by SD and reduced aggressive behaviors in adult zebrafish. SD led to a reduction in protein kinase A (PKA) phosphorylation, phosphorylated-cAMP response element-binding protein (p-CREB), and c-Fos expression in zebrafish brain. Notably, these alterations were effectively reversed by caffeine. In addition, caffeine mitigated neuroinflammation induced by SD, as evident from suppression of the SD-mediated increase in glial fibrillary acidic protein (GFAP) and nuclear factor-κB (NF-κB) activation. Caffeine restored normal O-GlcNAcylation and O-GlcNAc transferase (OGT) levels while reversing the increased expression of O-GlcNAcase (OGA) in zebrafish brain after SD. Intriguingly, rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, effectively mitigated cognitive deficits, restored p-CREB and c-Fos levels, and attenuated the increase in GFAP in brain induced by SD. In addition, rolipram reversed the decrease in O-GlcNAcylation and OGT expression as well as elevation of OGA expression following SD. Treatment with H89, a PKA inhibitor, significantly impaired the L/M functions of zebrafish compared with the control group, inducing a decrease in O-GlcNAcylation and OGT expression and, conversely, an increase in OGA expression. The H89-induced changes in O-GlcNAc cycling and L/M dysfunction were effectively reversed by glucosamine treatment. H89 suppressed, whereas caffeine and rolipram promoted O-GlcNAc cycling in Neuro2a cells. Our collective findings underscore the interplay between PKA signaling and O-GlcNAc cycling in the regulation of cognitive function in the brain, offering potential therapeutic targets for cognitive deficits associated with SD.NEW & NOTEWORTHY Our observation highlights the intricate interplay between cAMP/PKA signaling and O-GlcNAc cycling, unveiling a novel mechanism that potentially governs the regulation of learning and memory functions. The dynamic interplay between these two pathways provides a novel and nuanced perspective on the molecular foundation of learning and memory regulation. These insights open avenues for the development of targeted interventions to treat conditions that impact cognitive function, including SD.

Sugar Utilization-Associated Food-Grade Selection Markers in Lactic Acid Bacteria and Yeast

This comprehensive review explores the development of food-grade selection markers in lactic acid bacteria and yeast; some of their strains are precisely defined as safe microorganisms and are crucial in the food industry. Lactic acid bacteria, known for their ability to ferment carbohydrates into lactic acid, provide essential nutrients and contribute to immune responses. With its strong fermentation capabilities and rich nutritional profile, yeast finds use in various food products. Genetic engineering in these microorganisms has grown rapidly, enabling the expression of enzymes and secondary products for food production. However, the focus is on ensuring safety, necessitating food-grade selection markers. Traditional antibiotic and heavy metal resistance selection markers pose environmental and health risks, prompting the search for safer alternatives. Complementary selection markers, such as sugar utilization markers, offer a promising solution. These markers use carbohydrates as carbon sources for growth and are associated with the natural metabolism of lactic acid bacteria and yeast. This review discusses the use of specific sugars, such as lactose, melibiose, sucrose, D-xylose, glucosamine, and N-acetylglucosamine, as selection markers, highlighting their advantages and limitations. In summary, this review underscores the importance of food-grade selection markers in genetic engineering and offers insights into their applications, benefits, and challenges, providing valuable information for researchers in the field of food microbiology and biotechnology.

Expression of accessory genes in Salmonella requires the presence of the Gre factors

Genomic studies with Salmonella enterica serovar Typhimurium reveal a crucial role of horizontal gene transfer (HGT) in the acquisition of accessory cellular functions involved in host-interaction. Many virulence genes are located in genomic islands, plasmids and prophages. GreA and GreB proteins, Gre factors, interact transiently with the RNA polymerase alleviating backtracked complexes during transcription elongation. The overall effect of Gre factors depletion in Salmonella expression profile was studied. Both proteins are functionally redundant since only when both Gre factors were depleted a major effect in gene expression was detected. Remarkably, the accessory gene pool is particularly sensitive to the lack of Gre factors, with 18.6% of accessory genes stimulated by the Gre factors versus 4.4% of core genome genes. Gre factors involvement is particularly relevant for the expression of genes located in genomic islands. Our data reveal that Gre factors are required for the expression of accessory genes.

Discussing pathologic mechanisms of Diabetic retinopathy & therapeutic potentials of curcumin and β-glucogallin in the management of Diabetic retinopathy

Diabetic retinopathy (DR) is a form of retinal microangiopathy that occurs as a result of long-term Diabetes mellitus (DM). Patients with Diabetes mellitus typically suffer from DR as a progression of the disease that may be due to initiation and dysregulation of pathways like the polyol, hexosamine, the AGE/RAGE, and the PKC pathway, which all have negative impacts on eye health and vision. In this review, various databases, including PubMed, Google Scholar, Web of Science, and Science Direct, were scoured for data relevant to the aforementioned title. The three most common therapies for DR today are retinal photocoagulation, anti-vascular endothelial growth factor (VEGF) therapy, and vitrectomy, however, there are a number of drawbacks and limits to these methods. So, it is of critical importance and profound interest to discover treatments that may successfully address the pathogenesis of DR. Curcumin and β-glucogallin are the two potent compounds of natural origin that are already being used in various nutraceutical formulations for several ailments. They have been shown potent antiapoptotic, anti-inflammatory, antioxidant, anticancer, and pro-vascular function benefits in animal experiments. Their parent plant species have been used for generations by practitioners of traditional herbal medicine for the treatment and prevention of various eye ailments. In this review, we will discuss about pathophysiology of Diabetic retinopathy and the therapeutic potentials of curcumin and β-glucogallin one of the principal compounds from Curcuma longa and Emblica officinalis in Diabetic retinopathy.

O-GlcNAcylation: cellular physiology and therapeutic target for human diseases

O-linked-β-N-acetylglucosamine (O-GlcNAcylation) is a distinctive posttranslational protein modification involving the coordinated action of O-GlcNAc transferase and O-GlcNAcase, primarily targeting serine or threonine residues in various proteins. This modification impacts protein functionality, influencing stability, protein-protein interactions, and localization. Its interaction with other modifications such as phosphorylation and ubiquitination is becoming increasingly evident. Dysregulation of O-GlcNAcylation is associated with numerous human diseases, including diabetes, nervous system degeneration, and cancers. This review extensively explores the regulatory mechanisms of O-GlcNAcylation, its effects on cellular physiology, and its role in the pathogenesis of diseases. It examines the implications of aberrant O-GlcNAcylation in diabetes and tumorigenesis, highlighting novel insights into its potential role in cardiovascular diseases. The review also discusses the interplay of O-GlcNAcylation with other protein modifications and its impact on cell growth and metabolism. By synthesizing current research, this review elucidates the multifaceted roles of O-GlcNAcylation, providing a comprehensive reference for future studies. It underscores the potential of targeting the O-GlcNAcylation cycle in developing novel therapeutic strategies for various pathologies.

Deconvolution of multichannel LC-MS/MS chromatograms of glucosamine-phosphates: Evidence of a GlmS regulatory difference between Staphylococcus aureus and Enterococcus faecium

Resolving isomeric analytes is challenging given their physical similarity - making chromatographic resolution difficult, and their identical masses - making simple mass resolution impossible. MS/MS data provides a means to resolve isomeric analytes if their MS/MS intensity profiles are sufficiently different. Glucosamine-6-phosphate (GlcN-6P) and glucosamine-1-phosphate (GlcN-1P) are early bacterial cell wall intermediates. These and other isomeric hexosamine-phosphates are highly polar and unretained on reverse-phase chromatography media. Three commercially available hexosamine-phosphate standards (GlcN-6P, GlcN-1P, and GalN-1P) were derivatized with octanoic anhydride, and chromatographic conditions were established to resolve these analytes on C18 columns. GlcN-1P and GalN-1P overlapped chromatographically under all tested chromatography conditions. Three MS/MS fragments (79, 97, and 199 m/z) were common to all three commercially available hexosamine-phosphates. Intensity ratios of the three MS/MS fragments from these three hexosamine-phosphate standards were used to deconvolute mixture chromatograms of these standards by non-negative linear regression. This approach allowed the complete resolution of these analytes. The chromatographically overlapping GlcN-1P and GalN-1P, which shared similar but modestly different MS/MS intensity profiles, were fully resolved with this non-negative deconvolution approach. This approach was then applied to MRSA, VSE, and VRE bacterial extracts before and after exposure to vancomycin. This demonstrated a substantial (3-fold) increase in GlcN-6P in vancomycin-treated MRSA samples but not in vancomycin-treated VSE or VRE samples. These observations appear to localize previously observed differences between MRSA and VRE/VSE peptidoglycan biosynthesis regulation to GlmS, which synthesizes GlcN-6P and is the product of a regulatory ribozyme sensitive to the levels of GlcN-6P.

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives

Fructosamine has long been considered as a key intermediate of the Maillard reaction, which to a large extent is responsible for specific aroma, taste, and color formation in thermally processed or dehydrated foods. Since the 1980s, however, as a product of the Amadori rearrangement reaction between glucose and biologically significant amines such as proteins, fructosamine has experienced a boom in biomedical research, mainly due to its relevance to pathologies in diabetes and aging. In this chapter, we assess the scope of the knowledge on and applications of fructosamine-related molecules in chemistry, food, and health sciences, as reflected mostly in publications within the past decade. Methods of fructosamine synthesis and analysis, its chemical, and biological properties, and degradation reactions, together with fructosamine-modifying and -recognizing proteins are surveyed.

Antibacterial and immunological properties of piperine evidenced by preclinical studies: a systematic review

Aim: To review in vitro, in vivo, and in silico studies examining the antibacterial and immunomodulatory properties of piperine (PPN). Methods: This systematic review followed PRISMA guidelines, and five databases were searched. Results: A total of 40 articles were included in this study. Six aspects of PPN activity were identified, including antibacterial spectrum, association with antibiotics, efflux pump inhibition, biofilm effects, protein target binding, and modulation of immune functions/virulence factors. Most studies focused on Mycobacterium spp. and Staphylococcus aureus. Cell lineages and in vivo models were employed to study PPN antibacterial effects. Conclusion: We highlight PPN as a potential adjuvant in the treatment of bacterial infections. PPN possesses several antibacterial properties that need further exploration to determine the mechanisms behind its pharmacological activity.

Hexosamine biosynthetic pathway and O-GlcNAc cycling of glucose metabolism in brain function and disease

Impaired brain glucose metabolism is considered a hallmark of brain dysfunction and neurodegeneration. Disruption of the hexosamine biosynthetic pathway (HBP) and subsequent O-linked N-acetylglucosamine (O-GlcNAc) cycling has been identified as an emerging link between altered glucose metabolism and defects in the brain. Myriads of cytosolic and nuclear proteins in the nervous system are modified at serine or threonine residues with a single N-acetylglucosamine (O-GlcNAc) molecule by O-GlcNAc transferase (OGT), which can be removed by β-N-acetylglucosaminidase (O-GlcNAcase, OGA). Homeostatic regulation of O-GlcNAc cycling is important for the maintenance of normal brain activity. Although significant evidence linking dysregulated HBP metabolism and aberrant O-GlcNAc cycling to induction or progression of neuronal diseases has been obtained, the issue of whether altered O-GlcNAcylation is causal in brain pathogenesis remains uncertain. Elucidation of the specific functions and regulatory mechanisms of individual O-GlcNAcylated neuronal proteins in both normal and diseased states may facilitate the identification of novel therapeutic targets for various neuronal disorders. The information presented in this review highlights the importance of HBP/O-GlcNAcylation in the neuronal system and summarizes the roles and potential mechanisms of O-GlcNAcylated neuronal proteins in maintaining normal brain function and initiation and progression of neurological diseases.

Antibacterial and anti-biofilm activity of radezolid against Staphylococcus aureus clinical isolates from China

Although the potent antibacterial ability of radezolid against Staphylococcus aureus has been widely reported worldwide, its antibacterial and anti-biofilm activity against the S. aureus clinical isolates from China remains elusive. In this study, the minimum inhibitory concentration (MIC) of radezolid was determined in S. aureus clinical isolates from China using the agar dilution method, and the relationship between radezolid susceptibility and ST distribution was also investigated. The anti-biofilm activity of radezolid against S. aureus was determined by a crystal violet assay and compared with that of linezolid and contezolid. The quantitative proteomics of S. aureus treated with radezolid was analyzed, and the genetic mutations in radezolid-induced resistant S. aureus were determined by whole-genome sequencing. The dynamic changes in transcriptional expression levels of several biofilm-related genes were analyzed by quantitative RT-PCR. Our data showed that radezolid MIC ranged from ≤0.125 to 0.5 mg/L, which was almost 1/4 × MIC of linezolid against S. aureus, indicating the greater antibacterial activity of radezolid than linezolid. The S. aureus clinical isolates with radezolid MICs of 0.5 mg/L were most widely distributed in ST239 of MRSA and ST7 of MSSA. Moreover, the more robust anti-biofilm activity of radezolid with subinhibitory concentrations (1/8 × MIC and 1/16 × MIC) was demonstrated against S. aureus when compared with that of contezolid and linezolid. Genetic mutations were found in glmS, 23S rRNA, and DUF1542 domain-containing protein in radezolid-induced resistant S. aureus selected by in vitro induction of drug exposure. Quantitative proteomic analysis of S. aureus indicated that the global expression of some biofilm-related and virulence-related proteins was downregulated. Quantitative RT-PCR further confirmed that the expressions of some downregulated biofilm-related proteins, including sdrD, carA, sraP, hlgC, sasG, spa, sspP, fnbA, and oatA, were decreased after 12 h and 24 h of exposure to radezolid. Conclusively, radezolid shows robust antibacterial and anti-biofilm activity against S. aureus clinical isolates from China when compared with contezolid and linezolid.

Assessment of the Antioxidant and Antimicrobial Potential of Ptychotis verticillata Duby Essential Oil from Eastern Morocco: An In Vitro and In Silico Analysis

Ptychotis verticillata Duby, referred to as Nûnkha in the local language, is a medicinal plant that is native to Morocco. This particular plant is a member of the Apiaceae family and has a longstanding history in traditional medicine and has been utilized for therapeutic purposes by practitioners for generations. The goal of this research is to uncover the phytochemical makeup of the essential oil extracted from P. verticillata, which is indigenous to the Touissite region in Eastern Morocco. The extraction of the essential oil of P. verticillata (PVEO) was accomplished through the use of hydro-distillation via a Clevenger apparatus. The chemical profile of the essential oil was then determined through analysis utilizing gas chromatography–mass spectrometry (GC/MS). The study findings indicated that the essential oil of P. verticillata is composed primarily of Carvacrol (37.05%), D-Limonene (22.97%), γ-Terpinene (15.97%), m-Cymene (12.14%) and Thymol (8.49%). The in vitro antioxidant potential of PVEO was evaluated using two methods: the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical trapping assay and the ferric reducing antioxidant power (FRAP) method. The data demonstrated considerable radical scavenging and relative antioxidative power. Escherichia coli, Staphylococcus aureus, Listeria innocua, and Pseudomonas aeruginosa were the most susceptible bacterial strains tested, while Geotrichum candidum, Candida albicans, and Rhodotorula glutinis were the most resilient fungi strains. PVEO had broad-spectrum antifungal and antibacterial properties. To elucidate the antioxidative and antibacterial characteristics of the identified molecules, we applied the methodology of molecular docking, a computational approach that forecasts the binding of a small molecule to a protein. Additionally, we utilized the Prediction of Activity Spectra for Substances (PASS) algorithm; Absorption, Distribution, Metabolism, and Excretion (ADME); and Pro-Tox II (to predict the toxicity in silico) tests to demonstrate PVEO’s identified compounds’ drug-likeness, pharmacokinetic properties, the anticipated safety features after ingestion, and the potential pharmacological activity. Finally, our findings scientifically confirm the ethnomedicinal usage and usefulness of this plant, which may be a promising source for future pharmaceutical development.

Emerging Role of Protein O-GlcNAcylation in Liver Metabolism: Implications for Diabetes and NAFLD

O-linked b-N-acetyl-glucosaminylation (O-GlcNAcylation) is one of the most common post-translational modifications of proteins, and is established by modifying the serine or threonine residues of nuclear, cytoplasmic, and mitochondrial proteins. O-GlcNAc signaling is considered a critical nutrient sensor, and affects numerous proteins involved in cellular metabolic processes. O-GlcNAcylation modulates protein functions in different patterns, including protein stabilization, enzymatic activity, transcriptional activity, and protein interactions. Disrupted O-GlcNAcylation is associated with an abnormal metabolic state, and may result in metabolic disorders. As the liver is the center of nutrient metabolism, this review provides a brief description of the features of the O-GlcNAc signaling pathway, and summarizes the regulatory functions and underlying molecular mechanisms of O-GlcNAcylation in liver metabolism. Finally, this review highlights the role of O-GlcNAcylation in liver-associated diseases, such as diabetes and nonalcoholic fatty liver disease (NAFLD). We hope this review not only benefits the understanding of O-GlcNAc biology, but also provides new insights for treatments against liver-associated metabolic disorders.

Characterization of the glmS Ribozymes from Listeria Monocytogenes and Clostridium Difficile

The glmS ribozyme regulates the expression of the essential GlmS enzyme being involved in cell wall biosynthesis. While >450 variants of the glmS ribozyme were identified by in silico approaches and homology searches, only a few have yet been experimentally investigated. Herein, we validate and characterize the glmS ribozymes of the human pathogens Clostridium difficile and Listeria monocytogenes. Both ribozymes, as their previous characterized homologs rely on glucosamine-6-phosphate as co-factor and the presence of divalent cations for exerting the cleavage reaction. The observed EC₅₀ values in turn were found to be in the submicromolar range, at least an order of magnitude lower than observed for glmS ribozymes from other bacteria. The glmS ribozyme of L. monocytogenes was further shown to bear unique properties. It discriminates between co-factors very stringently and other than the glmS ribozyme of C. difficile retains activity at low temperatures. This finding illustrates that albeit being highly conserved, glmS ribozymes have unique characteristics.

Inhibitors of glucosamine-6-phosphate synthase as potential antimicrobials or antidiabetics - synthesis and properties

Glucosamine-6-phosphate synthase (GlcN-6-P synthase) is known as a promising target for antimicrobial agents and antidiabetics. Several compounds of natural or synthetic origin have been identified as inhibitors of this enzyme. This set comprises highly selective l-glutamine, amino sugar phosphate or transition state intermediate cis-enolamine analogues. Relatively low antimicrobial activity of these inhibitors, poorly penetrating microbial cell membranes, has been improved using the pro-drug approach. On the other hand, a number of heterocyclic and polycyclic compounds demonstrating antimicrobial activity have been presented as putative inhibitors of the enzyme, based on the results of molecular docking to GlcN-6-P synthase matrix. The most active compounds of this group could be considered promising leads for development of novel antimicrobial drugs or antidiabetics, provided their selective toxicity is confirmed.

Cell compensatory responses of fungi to damage of the cell wall induced by Calcofluor White and Congo Red with emphasis on Sporothrix schenckii and Sporothrix globosa. A review

The cell wall (CW) of fungi exhibits a complex structure and a characteristic chemical composition consisting almost entirely of interacting crystalline and amorphous polysaccharides. These are synthesized by a number of sugar polymerases and depolymerases encoded by a high proportion of the fungal genome (for instance, 20% in Saccharomyces cerevisiae). These enzymes act in an exquisitely coordinated process to assemble the tridimensional and the functional structure of the wall. Apart from playing a critical role in morphogenesis, cell protection, viability and pathogenesis, the CW represents a potential target for antifungals as most of its constituents do not exist in humans. Chitin, β-glucans and cellulose are the most frequent crystalline polymers found in the fungal CW. The hexosamine biosynthesis pathway (HBP) is critical for CW elaboration. Also known as the Leloir pathway, this pathway ends with the formation of UDP-N-GlcNAc after four enzymatic steps that start with fructose-6-phosphate and L-glutamine in a short deviation of glycolysis. This activated aminosugar is used for the synthesis of a large variety of biomacromolecules in a vast number of organisms including bacteria, fungi, insects, crustaceans and mammalian cells. The first reaction of the HBP is catalyzed by GlcN-6-P synthase (L-glutamine:D-fructose-6-phosphate amidotransferase; EC 2.6.1.16), a critical enzyme that has been considered as a potential target for antifungals. The enzyme regulates the amount of cell UDP-N-GlcNAc and in eukaryotes is feedback inhibited by the activated aminosugar and other factors. The native and recombinant forms of GlcN-6-P synthase has been purified and characterized from both prokaryotic and eukaryotic organisms and demonstrated its critical role in CW remodeling and morphogenesis after exposure of some fungi to agents that stress the cell surface by interacting with wall polymers. This review deals with some of the cell compensatory responses of fungi to wall damage induced by Congo Red and Calcofluor White.

A Riboswitch-Driven Era of New Antibacterials

Riboswitches are structured non-coding RNAs found in the 5′ UTR of important genes for bacterial metabolism, virulence and survival. Upon the binding of specific ligands that can vary from simple ions to complex molecules such as nucleotides and tRNAs, riboswitches change their local and global mRNA conformations to affect downstream transcription or translation. Due to their dynamic nature and central regulatory role in bacterial metabolism, riboswitches have been exploited as novel RNA-based targets for the development of new generation antibacterials that can overcome drug-resistance problems. During recent years, several important riboswitch structures from many bacterial representatives, including several prominent human pathogens, have shown that riboswitches are ideal RNA targets for new compounds that can interfere with their structure and function, exhibiting much reduced resistance over time. Most interestingly, mainstream antibiotics that target the ribosome have been shown to effectively modulate the regulatory behavior and capacity of several riboswitches, both in vivo and in vitro, emphasizing the need for more in-depth studies and biological evaluation of new antibiotics. Herein, we summarize the currently known compounds that target several main riboswitches and discuss the role of mainstream antibiotics as modulators of T-box riboswitches, in the dawn of an era of novel inhibitors that target important bacterial regulatory RNAs.

Antibacterial and Antioxidant Activity of Dysphania ambrosioides (L.) Mosyakin and Clemants Essential Oils: Experimental and Computational Approaches

Dysphania ambrosioides (L.) Mosyakin and Clemants, also known as Mexican tea, and locally known as Mkhinza, is a polymorphic annual and perennial herb, and it is widely used in folk medicine to treat a broad range of illnesses in Morocco. The aim of this study was to determine the phytochemical content and the antioxidant and the antibacterial properties of essential oils isolated from D. ambrosioides aerial components, growing in Eastern Morocco (Figuig). Hydrodistillation was used to separate D. ambrosioides essential oils, and the abundance of each phytocompound was determined by using Gas Chromatography coupled with Mass Spectrometry (GC-MS). In vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and inhibition of β-carotene/linoleic acid bleaching assays were used to determine D. ambrosioides essential oils' antioxidant activity. The findings revealed relative antioxidative power and modest radical scavenging. The antibacterial activity of the essential oils was broad-spectrum, with Escherichia coli, Staphylococcus aureus, and Enterococcus faecalis as the most susceptible strains tested. To elucidate the physicochemical nature, drug-likeness, and the antioxidant and antibacterial action of the identified phytocomponents, computational techniques, such as ADMET analysis, and molecular docking were used.

Chiral Primary Amine Catalyzed Enantioselective Tandem Reactions Based on Heyns Rearrangement: Synthesis of α-Tertiary Amino Ketones

Herein, we disclose a new catalytic asymmetric tandem reaction based on the Heyns rearrangement for the synthesis of chiral α-amino ketones with readily available substrates. The rearrangement is different from the Heyns rearrangement in that the α-amino ketones were obtained without the shift of the carbonyl group. The key to success is using chiral primary amine as a catalyst by mimicking glucosamine-6-phosphate synthase in catalyzing the efficient Heyns rearrangement in organisms.

Slt2 Is Required to Activate ER-Stress-Protective Mechanisms through TORC1 Inhibition and Hexosamine Pathway Activation

Slt2, the MAPK of the cell wall integrity (CWI) pathway, connects different signaling pathways and performs different functions in the protective response of S. cerevisiae to stress. Previous work has evidenced the relation of the CWI pathway and the unfolded protein response (UPR), a transcriptional program activated upon endoplasmic reticulum (ER) stress. However, the mechanisms of crosstalk between these pathways and the targets regulated by Slt2 under ER stress remain unclear. Here, we demonstrated that ectopic expression of GFA1, the gene encoding the first enzyme in the synthesis of UDP-GlcNAc by the hexosamine biosynthetic pathway (HBP) or supplementation of the growth medium with glucosamine (GlcN), increases the tolerance of slt2 mutant cells to different ER-stress inducers. Remarkably, GlcN also alleviates the sensitivity phenotype of cells lacking IRE1 or HAC1, the main actors in controlling the UPR. The exogenous addition of GlcN reduced the abundance of glycosylated proteins and triggered autophagy. We also found that TORC1, the central stress and growth controller, is inhibited by tunicamycin exposure in cells of the wild-type strain but not in those lacking Slt2. Consistent with this, the tunicamycin-induced activation of autophagy and the increased synthesis of ATP in response to ER stress were absent by knock-out of SLT2. Altogether, our data placed Slt2 as an essential actor of the ER stress response by regulating the HBP activity and the TORC1-dependent signaling.

Antimicrobial Activity and In Silico Molecular Docking Studies of Pentacyclic Spiro[oxindole-2,3′-pyrrolidines] Tethered with Succinimide Scaffolds

Three-component cascade reactions of (E)-3-arylidene-1-methyl-pyrrolidine-2,5-diones, L-valine and various isatin derivatives are described. A series of 17 spiropyrrolidine derivatives with wide structural complexity and diversity have been thus obtained in moderate to excellent yields under mild reaction conditions. The structure and stereochemistry of these N-heterocyclic cycloadducts has been established by spectroscopic techniques and unambiguously confirmed by a single-crystal X-ray diffraction analysis performed on one derivative. UV-visible spectra have been recorded for all new compounds. Furthermore, the synthesized N-heterocyclic compounds have been screened for their in vitro antibacterial and antifungal activities. Several derivatives exhibited moderate to good activities, comparable to those of the known standard drugs Amphotericin B and Tetracycline. Structural activity relationships (SARs) and molecular docking of the most promising derivatives into the binding sites of glucosamine 6-phosphate synthase (GlcN6P) and methionyl-trna-synthetase (1PFV) were also established. Furthermore, pharmacokinetic studies indicate that the heterocycles exhibit acceptable predictive ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties and good drug ability.

Glucosamine Supplementation Improves Physical Performance in Trained Mice

INTRODUCTION

D-Glucosamine (GlcN) is one of the most widely consumed dietary supplements and complementary medicines in the world and has been traditionally used to attenuate osteoarthritis in humans. GlcN extends lifespan in different animal models. In humans, its supplementation has been strongly associated with decreased total mortality and improved vascular endothelial function. GlcN acts as a suppressor of inflammation and by inhibiting glycolysis, it can activate the metabolism of stored fat and mitochondrial respiration.

METHODS

The conventional human GlcN dose is 1,500 mg x day-1 but extensive evidence indicates that much higher doses are well tolerated. GlcN is one of the supplements that has experienced a greater use in the last years in elite athletes mainly due to its potential chondroprotective effects that may promote cartilage health. However, the possibility of it being an ergogenic aid has not been explored. We aimed to study the potential beneficial effects of GlcN on mitochondrial content, on physical performance and oxidative stress in mice that were aerobically trained and supplemented with three different doses of glucosamine (250, 500, and 1,000 mg x Kg-1) for six weeks. We measured exercise performance (grip strength, motor coordination and running capacity) before and after the training period. Proteins involved in mitochondrial biogenesis (AMPK, PGC-1, NRF-1, SIRT-1, cytochrome c, citrate synthase), markers of oxidative stress (GSSG/GSH) or damage (MDA, carbonylated proteins), antioxidant enzymes (NRF-2, SOD1, SOD2, Catalase and PRDX6) and MAPKs (p38 and ERK ½) were also determined in skeletal muscle.

RESULTS AND CONCLUSIONS

Our results show that GlcN supplementation in aerobically trained mice, at doses equivalent to those conventionally used in humans, increases the protein levels of mitochondrial biogenesis markers, improves motor coordination and may have a synergistic effect with exercise training on running distance.

REM Sleep Deprivation Impairs Learning and Memory by Decreasing Brain O-GlcNAc Cycling in Mouse

Rapid eye movement (REM) sleep is implicated learning and memory (L/M) functions and hippocampal long-term potentiation (LTP). Here, we demonstrate that REM sleep deprivation (REMSD)-induced impairment of contextual fear memory in mouse is linked to a reduction in hexosamine biosynthetic pathway (HBP)/O-GlcNAc flux in mouse brain. In mice exposed to REMSD, O-GlcNAcylation, and O-GlcNAc transferase (OGT) were downregulated while O-GlcNAcase was upregulated compared to control mouse brain. Foot shock fear conditioning (FC) induced activation of protein kinase A (PKA) and cAMP response element binding protein (CREB), which were significantly inhibited in brains of the REMSD group. Intriguingly, REMSD-induced defects in L/M functions and FC-induced PKA/CREB activation were restored upon increasing O-GlcNAc cycling with glucosamine (GlcN) or Thiamet G. Furthermore, Thiamet G restored the REMSD-induced decrease in dendritic spine density. Suppression of O-GlcNAcylation by the glutamine fructose-6-phosphate amidotransferase (GFAT) inhibitor, 6-diazo-5-oxo-L-norleucine (DON), or OGT inhibitor, OSMI-1, impaired memory function, and inhibited FC-induced PKA/CREB activation. DON additionally reduced the amplitude of baseline field excitatory postsynaptic potential (fEPSP) and magnitude of long-term potentiation (LTP) in normal mouse hippocampal slices. To our knowledge, this is the first study to provide comprehensive evidence of dynamic O-GlcNAcylation changes during the L/M process in mice and defects in this pathway in the brain of REM sleep-deprived mice. Our collective results highlight HBP/O-GlcNAc cycling as a novel molecular link between sleep and cognitive function.

Synthesis of a Series of Novel 2-Amino-5-Substituted 1,3,4-oxadiazole and 1,3,4-thiadiazole Derivatives as Potential Anticancer, Antifungal and Antibacterial Agents

BACKGROUND

Many compounds containing a five-membered heterocyclic ring display exceptional chemical properties and versatile biological activities.

OBJECTIVE

The objective of the present study was the desire to prepare the 5-substituted 2-amino-1,3,4-oxadiazole and 2-amino-1,3,4-thiadiazole derivatives and evaluate their potential anticancer, antibacterial and antifungal activities.

METHODS

Twenty-seven derivatives were synthesized by iodine-mediated cyclization of semicarbazones or thiosemicarbazones obtained from condensation of semicarbazide or thiosemicarbazide and aldehydes. The structures were confirmed by 1H-NMR, 13C-NMR and MS spectra. The antibacterial and antifungal activities were evaluated by diffusion method and the anticancer activities were evaluated by MTT assay.

RESULTS

Twenty-seven derivatives have been synthesized in moderate to good yields. A number of derivatives exhibited potential antibacterial, antifungal and anticancer activities.

CONCLUSION

Compounds (1b, 1e and 1g) showed antibacterial activity against Streptococcus faecalis, MSSA and MRSA with MIC ranging between 4 to 64 µg/mL. Compound (2g) showed antifungal activity against Candida albicans (8 µg/mL) and Aspergillus niger (64 µg/mL). Compound (1o) exhibited high cytotoxic activity against HepG2 cell line (IC50 value 8.6 µM), which is comparable to the activity of paclitaxel, and is non-toxic on LLC-PK1 normal cell line. The structure activity relationship and molecular docking study of the synthesized compounds are also reported.

Appraisal of the Role of In silico Methods in Pyrazole Based Drug Design

Pyrazole and its derivatives are a pharmacologically and significantly active scaffolds that have innumerable physiological and pharmacological activities. They can be very good targets for the discovery of novel anti-bacterial, anti-cancer, anti-inflammatory, anti-fungal, anti-tubercular, antiviral, antioxidant, antidepressant, anti-convulsant and neuroprotective drugs. This review focuses on the importance of in silico manipulations of pyrazole and its derivatives for medicinal chemistry. The authors have discussed currently available information on the use of computational techniques like molecular docking, structure-based virtual screening (SBVS), molecular dynamics (MD) simulations, quantitative structure activity relationship (QSAR), comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) to drug design using pyrazole moieties. Pyrazole based drug design is mainly dependent on the integration of experimental and computational approaches. The authors feel that more studies need to be done to fully explore the pharmacological potential of the pyrazole moiety and in silico method can be of great help.

The World of Stable Ribonucleoproteins and Its Mapping With Grad-Seq and Related Approaches

Macromolecular complexes of proteins and RNAs are essential building blocks of cells. These stable supramolecular particles can be viewed as minimal biochemical units whose structural organization, i.e., the way the RNA and the protein interact with each other, is directly linked to their biological function. Whether those are dynamic regulatory ribonucleoproteins (RNPs) or integrated molecular machines involved in gene expression, the comprehensive knowledge of these units is critical to our understanding of key molecular mechanisms and cell physiology phenomena. Such is the goal of diverse complexomic approaches and in particular of the recently developed gradient profiling by sequencing (Grad-seq). By separating cellular protein and RNA complexes on a density gradient and quantifying their distributions genome-wide by mass spectrometry and deep sequencing, Grad-seq charts global landscapes of native macromolecular assemblies. In this review, we propose a function-based ontology of stable RNPs and discuss how Grad-seq and related approaches transformed our perspective of bacterial and eukaryotic ribonucleoproteins by guiding the discovery of new RNA-binding proteins and unusual classes of noncoding RNAs. We highlight some methodological aspects and developments that permit to further boost the power of this technique and to look for exciting new biology in understudied and challenging biological models.

Dehydroabietylamine, A Diterpene from Carthamus tinctorious L. Showing Antibacterial and Anthelmintic Effects with Computational Evidence

BACKGROUND

Plant-based drugs provide an outstanding contribution to modern therapeutics, and it is well known that the presence of different phytochemicals is responsible for such pharmacological effects. Carthamus tinctorius L. is one such medicinally important plant whose different solvent extracts have been reported with several pharmacological effects like antibacterial, hepatoprotective, and wound healing. The exploration of phytoconstituents from such a medicinally important plant for different pharmacological effects could produce new and effective drugs to treat human diseases.

OBJECTIVE

The present study attempts to explore the antibacterial and anthelmintic properties of dehydroabietylamine, a diterpene isolated from Carthamus tinctorius L. followed by the in silico elucidation of its probable mode of action.

METHODS

The minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) of dehydroabietylamine were assessed against Staphylococcus aureus and Pseudomonas aeruginosa, using micro- broth dilution method. The anthelmintic activity of was determined to assess the time taken for paralysis and death of Pheretima Posthuma at different concentrations. Additionally, molecular docking study was conducted to understand the interaction between dehydroabietylamine with target proteins identified for both antibacterial and anthelmintic activity viz., glucosamine-6-phosphate synthase and β-Tubulin, respectively.

RESULTS

The dehydroabietylamine showed the significant MIC for S. aureus (12.5 μg/ml) and P. aeruginosa (6.25μg/ml), respectively. The result of anthelmintics effect of dehydroabietylamine was found to be dosedependent and compared to the standard drug, albendazole.

CONCLUSION

The interactions of dehydroabietylamine with the two target proteins with high binding affinity indicated the probable inhibition of target proteins, which could be the cause for prominent antibacterial and antihelminthic effects.

Responses of Sporothrix globosa to the cell wall perturbing agents Congo Red and Calcofluor White

It is well documented that disturbance of cell surface by some agents triggers compensatory responses aimed to maintain the cell wall integrity in fungi and other organisms. Here, the thermodimorphic fungus Sporothrix globosa, a member of the pathogenic clade of the Sporothrix complex, was propagated in yeast-peptone-dextrose medium under conditions to obtain the mycelium (pH 4.5, 27-28 °C) or the yeast (pH 7.8, 32-34 °C) morphotypes in the absence and presence of the wall-interacting dyes Congo Red (CR) and Calcofluor White (CFW) either alone or in combination. After different periods of time, growth, cell morphology and activity of glucosamine-6-phosphate synthase (GlcN-6-P synthase), an ubiquitous enzyme that plays a crucial role in cell wall biogenesis, were determined. CR and to a lower extent CFW affected growth and morphology of both fungal morphotypes and significantly increased enzyme activity. Notoriously, CR or CR in combination with CFW induced the transient conversion of yeasts into conidia-forming filamentous cells even under culture conditions adjusted for yeast development, most likely as a strategy to evade the noxious effect of the dye. After sometime, hypha returned to yeast cells. An hypothetical model to explain the effect of CR on morphology and enzyme activity based on the possible role of membrane-spanning proteins known as mechanosensors is proposed. Results are discussed in terms of the fungal responses to cell wall damage.

L-arabinose induces the formation of viable non-proliferating spheroplasts in Vibrio cholerae

Vibrio cholerae, the agent of the deadly human disease cholera, propagates as a curved rod-shaped bacterium in warm waters. It is sensitive to cold, but persists in cold waters under the form of viable but non-dividing coccoidal shaped cells. Additionally, V. cholerae is able to form non-proliferating spherical cells in response to cell wall damage. It was recently reported that L-arabinose, a component of the hemicellulose and pectin of terrestrial plants, stops the growth of V. cholerae. Here, we show that L-arabinose induces the formation of spheroplasts that lose the ability to divide and stop growing in volume over time. However, they remain viable and upon removal of L-arabinose they start expanding in volume, form branched structures and give rise to cells with a normal morphology after a few divisions. We further show that WigKR, a histidine kinase/response regulator pair implicated in the induction of a high expression of cell wall synthetic genes, prevents the lysis of the spheroplasts during growth restart. Finally, we show that the physiological perturbations result from the import and catabolic processing of L-arabinose by the V. cholerae homolog of the E. coli galactose transport and catabolic system. Taken together, our results suggest that the formation of non-growing spherical cells is a common response of Vibrios exposed to detrimental conditions. They also permit to define conditions preventing any physiological perturbation of V. cholerae when using L-arabinose to induce gene expression from the tightly regulated promoter of the Escherichia coli araBAD operon.Importance Vibrios among other bacteria form transient cell wall deficient forms as a response to different stresses and revert to proliferating rods when permissive conditions have been restored. Such cellular forms have been associated to antimicrobial tolerance, chronic infections and environmental dispersion.The effect of L-Ara on V. cholerae could provide an easily tractable model to study the ability of Vibrios to form viable reversible spheroplasts. Indeed, the quick transition to spheroplasts and reversion to proliferating rods by addition or removal of L-Ara is ideal to understand the genetic program governing this physiological state and the spatial rearrangements of the cellular machineries during cell shape transitions.

Comparative Study of Metabolite Changes After Antihypertensive Therapy With Calcium Channel Blockers or Angiotensin Type 1 Receptor Blockers

ABSTRACT

The high prevalence of hypertension contributes to an increased global burden of cardiovascular diseases. Calcium channel blockers (CCBs) and angiotensin type 1 receptor blockers (ARBs) are the most widely used antihypertensive drugs, and the effects of these drugs on serum metabolites remain unknown. Untargeted metabolomics has been proved to be a powerful approach for the detection of biomarkers and new compounds. In this study, we aimed to determine the changes in metabolites after single-drug therapy with a CCB or ARB in patients newly diagnosed with mild to moderate primary hypertension. We enrolled 33 patients and used an untargeted metabolomics approach to measure 625 metabolites associated with the response to a 4-week treatment of antihypertensive drugs. After screening based on P < 0.05, fold change > 1.2 or fold change < 0.83, and variable importance in projection > 1, 63 differential metabolites were collected. Four metabolic pathways-cysteine and methionine metabolism, phenylalanine metabolism, taurine and hypotaurine metabolism, and tyrosine metabolism-were identified in participants treated with ARBs. Only taurine and hypotaurine metabolism were identified in participants treated with CCBs. Furthermore, homocitrulline and glucosamine-6-phosphate were relevant to whether the blood pressure reduction achieved the target blood pressure (P < 0.05). Our study provides some evidence that changes in certain metabolites may be a potential marker for the dynamic monitoring of the protective effects and side effects of antihypertensive drugs.

Emerging roles of protein O-GlcNAcylation in cardiovascular diseases: Insights and novel therapeutic targets

Cardiovascular diseases (CVDs) are the leading cause of death globally. While the major focus of pharmacological and non-pharmacological interventions has been on targeting disease pathophysiology and limiting predisposing factors, our understanding of the cellular and molecular mechanisms underlying the pathogenesis of CVDs remains incomplete. One mechanism that has recently emerged is protein O-GlcNAcylation. This is a dynamic, site-specific reversible post-translational modification of serine and threonine residues on target proteins and is controlled by two enzymes: O-linked β-N-acetylglucosamine transferase (OGT) and O-linked β-N-acetylglucosaminidase (OGA). Protein O-GlcNAcylation alters the cellular functions of these target proteins which play vital roles in pathways that modulate vascular homeostasis and cardiac function. Through this review, we aim to give insights on the role of protein O-GlcNAcylation in cardiovascular diseases and identify potential therapeutic targets in this pathway for development of more effective medicines to improve patient outcomes.

Riboswitches as Drug Targets for Antibiotics

Riboswitches reside in the untranslated region of RNA and regulate genes involved in the biosynthesis of essential metabolites through binding of small molecules. Since their discovery at the beginning of this century, riboswitches have been regarded as potential antibacterial targets. Using fragment screening, high-throughput screening and rational ligand design guided by X-ray crystallography, lead compounds against various riboswitches have been identified. Here, we review the current status and suitability of the thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), glmS, guanine, and other riboswitches as antibacterial targets and discuss them in a biological context. Further, we highlight challenges in riboswitch drug discovery and emphasis the need to develop riboswitch specific high-throughput screening methods.

Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy

Diabetic polyneuropathy (DPN) is the most common neuropathy manifested in diabetes. Symptoms include allodynia, pain, paralysis, and ulcer formation. There is currently no established radical treatment, although new mechanisms of DPN are being vigorously explored. A pathophysiological feature of DPN is abnormal glucose metabolism induced by chronic hyperglycemia in the peripheral nerves. Particularly, activation of collateral glucose-utilizing pathways such as the polyol pathway, protein kinase C, advanced glycation end-product formation, hexosamine biosynthetic pathway, pentose phosphate pathway, and anaerobic glycolytic pathway are reported to contribute to the onset and progression of DPN. Inhibitors of aldose reductase, a rate-limiting enzyme involved in the polyol pathway, are the only compounds clinically permitted for DPN treatment in Japan, although their efficacies are limited. This may indicate that multiple pathways can contribute to the pathophysiology of DPN. Comprehensive metabolic analysis may help to elucidate global changes in the collateral glucose-utilizing pathways during the development of DPN, and highlight therapeutic targets in these pathways.

Reprint of: Role of O-linked N-acetylglucosamine (O-GlcNAc) modification of proteins in diabetic cardiovascular complications

The post-translational modification of serine and threonine residues of proteins by O-linked N-acetylglucosamine (O-GlcNAc) regulates diverse cellular processes in the cardiovascular system. UDP-GlcNAc is a substrate for O-GlcNAc transferase, which catalyzes the attachment of O-GlcNAc to proteins. O-GlcNAcase catalyzes the removal of O-GlcNAc from proteins. UDP-GlcNAc is the end product of the hexosamine biosynthesis pathway, which is regulated primarily by glucose-6-phosphate-Glutamine:fructose-6-phosphate amidotransferase (GFAT). GFAT catalyzes the formation of glucosamine-6-phosphate from fructose-6-phosphate and glutamine. Whereas O-GlcNAc is essential for cell viability, sustained increases in O-GlcNAc levels have been implicated in the etiology of many chronic diseases and is associated with glucose toxicity and diabetic complications in various organs including the cardiovascular system. This review provides an overview of the regulation of protein O-GlcNAcylation followed by a discussion of potential mechanisms by which dysregulation in O-GlcNAc cycling contributes to the adverse effects of diabetes on the cardiovascular system.

Role of O-linked N-acetylglucosamine (O-GlcNAc) modification of proteins in diabetic cardiovascular complications

The post-translational modification of serine and threonine residues of proteins by O-linked N-acetylglucosamine (O-GlcNAc) regulates diverse cellular processes in the cardiovascular system. UDP-GlcNAc is a substrate for O-GlcNAc transferase, which catalyzes the attachment of O-GlcNAc to proteins. O-GlcNAcase catalyzes the removal of O-GlcNAc from proteins. UDP-GlcNAc is the end product of the hexosamine biosynthesis pathway, which is regulated primarily by glucose-6-phosphate-Glutamine:fructose-6-phosphate amidotransferase (GFAT). GFAT catalyzes the formation of glucosamine-6-phosphate from fructose-6-phosphate and glutamine. Whereas O-GlcNAc is essential for cell viability, sustained increases in O-GlcNAc levels have been implicated in the etiology of many chronic diseases and is associated with glucose toxicity and diabetic complications in various organs including the cardiovascular system. This review provides an overview of the regulation of protein O-GlcNAcylation followed by a discussion of potential mechanisms by which dysregulation in O-GlcNAc cycling contributes to the adverse effects of diabetes on the cardiovascular system.

Role of O-Linked N-Acetylglucosamine Protein Modification in Cellular (Patho)Physiology

In the mid-1980s, the identification of serine and threonine residues on nuclear and cytoplasmic proteins modified by a N-acetylglucosamine moiety (O-GlcNAc) via an O-linkage overturned the widely held assumption that glycosylation only occurred in the endoplasmic reticulum, Golgi apparatus, and secretory pathways. In contrast to traditional glycosylation, the O-GlcNAc modification does not lead to complex, branched glycan structures and is rapidly cycled on and off proteins by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. Since its discovery, O-GlcNAcylation has been shown to contribute to numerous cellular functions, including signaling, protein localization and stability, transcription, chromatin remodeling, mitochondrial function, and cell survival. Dysregulation in O-GlcNAc cycling has been implicated in the progression of a wide range of diseases, such as diabetes, diabetic complications, cancer, cardiovascular, and neurodegenerative diseases. This review will outline our current understanding of the processes involved in regulating O-GlcNAc turnover, the role of O-GlcNAcylation in regulating cellular physiology, and how dysregulation in O-GlcNAc cycling contributes to pathophysiological processes.

Glucosamine regulates hepatic lipid accumulation by sensing glucose levels or feeding states of normal and excess

Dose-dependent lipid accumulation was induced by glucose in HepG2 cells. GlcN also exerted a promotory effect on lipid accumulation in HepG2 cells under normal glucose conditions (NG, 5 mM) and liver of normal fed zebrafish larvae. High glucose (HG, 25 mM)-induced lipid accumulation was suppressed by l-glutamine-d-fructose 6-phosphate amidotransferase inhibitors. ER stress inhibitors did not suppress HG or GlcN-mediated lipid accumulation. HG and GlcN stimulated protein expression, DNA binding and O-GlcNAcylation of carbohydrate-responsive element-binding protein (ChREBP). Furthermore, both HG and GlcN increased nuclear sterol regulatory element-binding protein-1 (SREBP-1) levels in HepG2 cells. In contrast to its stimulatory effect under NG, GlcN suppressed lipid accumulation in HepG2 cells under HG conditions. Similarly, GlcN suppressed lipid accumulation in livers of overfed zebrafish. In addition, GlcN activity on DNA binding and O-GlcNAcylation of ChREBP was stimulatory under NG and inhibitory under HG conditions. Moreover, GlcN enhanced ChREBP, SREBP-1c, ACC, FAS, L-PK and SCD-1 mRNA expression under NG but inhibited HG-induced upregulation in HepG2 cells. The O-GlcNAc transferase inhibitor, alloxan, reduced lipid accumulation by HG or GlcN while the O-GlcNAcase inhibitor, PUGNAc, enhanced lipid accumulation in HepG2 cells and liver of zebrafish larvae. GlcN-induced lipid accumulation was inhibited by the AMPK activator, AICAR. Phosphorylation of AMPK (p-AMPK) was suppressed by GlcN under NG while increased by GlcN under HG. PUGNAc downregulated p-AMPK while alloxan restored GlcN- or HG-induced p-AMPK inhibition. Our results collectively suggest that GlcN regulates lipogenesis by sensing the glucose or energy states of normal and excess fuel through AMPK modulation.