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Overcoming resistance to bioactive small molecules is a significant challenge for health care and agriculture. As a result, efforts to uncover the mechanisms of resistance are essential to the development of new antibiotics, anticancer drugs and pesticides. To study how nature evolves resistance to highly potent natural products, we examined the biosynthesis and mechanism of self-resistance of the fungal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) inhibitor heptelidic acid (HA). HA is a nanomolar inhibitor of GADPH through the covalent modification of the active site cysteine thiol. The biosynthetic pathway of HA was elucidated, which uncovered the enzymatic basis of formation of the epoxide warhead. Structure-activity relationship study using biosynthetic intermediates established the importance of the fused lactone ring system in HA. The molecular basis of HA inhibiting human GAPDH was illustrated through the crystal structure of Hs-GAPDH covalently bound with HA. A GAPDH isozyme HepG encoded in the HA cluster was characterized to be less sensitive to HA, and therefore contribute to self-resistance for the producing host. Comparison of the crystal structures of human GAPDH and HepG showed mutations both within and remote to the active site can contribute to resistance of inactivation, which was confirmed through mutagenesis. Due to the critical role GAPDH plays in aerobic glycolysis and other cellular functions, knowledge of HA mode of action and self-resistance mechanism could accelerate the development of improved inhibitors.

This study aimed to prepare Gardenia fructus carbon dots (GF-CDs) and examine their efficacy in mitigating oxidative stress and apoptosis in intestinal porcine epithelial cells from the jejunum (IPEC-J2 cells) induced by lipopolysaccharide (LPS). The GF-CDs were synthesized using a one-step hydrothermal method. The oxidative damage model of IPEC-J2 cells was induced through LPS treatment. The potential mechanism by which GF-CDs affect cellular oxidative damage was examined through the perspectives of apoptosis, reactive oxygen species level, antioxidant-related enzyme index, mRNA transcription of antioxidant-related genes, and the expression of antioxidant proteins. The results revealed that GF-CDs, characterized by particle sizes<7 nm, abundant functional groups, and good water solubility, were synthesized using a one-step hydrothermal method. The carbon spots of Gardenia fructus at concentrations of 50, 100, and 200 μg/mL exhibited protective effects, as evidenced by their ability to enhance viability (P <0.01) and restore cellular morphology after oxidative damage. The GF-CDs decreased oxidative damage and reduced the apoptosis rate of cells by upregulating AKT1 expression and downregulating the expression of Caspase 3, STAT3, TNF-α, and JNK. These results indicate that GF-CDs have the characteristic physicochemical properties of CDs, exhibit biological activities related to antioxidation and cellular damage mitigation, and may serve as a potential healthcare product in swine raising. [ABSTRACT FROM AUTHOR]

Bioactive natural products have evolved to inhibit specific cellular targets and have served as lead molecules for health and agricultural applications for the past century1-3. The post-genomics era has brought a renaissance in the discovery of natural products using synthetic-biology tools4-6. However, compared to traditional bioactivity-guided approaches, genome mining of natural products with specific and potent biological activities remains challenging4. Here we present the discovery and validation of a potent herbicide that targets a critical metabolic enzyme that is required for plant survival. Our approach is based on the co-clustering of a self-resistance gene in the natural-product biosynthesis gene cluster7-9, which provides insight into the potential biological activity of the encoded compound. We targeted dihydroxy-acid dehydratase in the branched-chain amino acid biosynthetic pathway in plants; the last step in this pathway is often targeted for herbicide development10. We show that the fungal sesquiterpenoid aspterric acid, which was discovered using the method described above, is a sub-micromolar inhibitor of dihydroxy-acid dehydratase that is effective as a herbicide in spray applications. The self-resistance gene astD was validated to be insensitive to aspterric acid and was deployed as a transgene in the establishment of plants that are resistant to aspterric acid. This herbicide-resistance gene combination complements the urgent ongoing efforts to overcome weed resistance11. Our discovery demonstrates the potential of using a resistance-gene-directed approach in the discovery of bioactive natural products.

Persister cells (PS) selected for anticancer therapy have been recognized as a significant contributor to the development of treatment‐resistant malignancies. It is found that imposing glutamine restriction induces the generation of PS, which paradoxically bestows heightened resistance to glutamine restriction treatment by activating the integrated stress response and initiating the general control nonderepressible 2‐activating transcription factor 4‐alanine, serine, cysteine‐preferring transporter 2 (GCN2‐ATF4‐ASCT2) axis. Central to this phenomenon is the stress‐induced ATF4 translational reprogramming. Unfortunately, directly targeting ATF4 protein has proven to be a formidable challenge because of its flat surface. Nonetheless, a G‐quadruplex structure located within the promoter region of ATF4 (ATF4‐G4) is uncovered and resolved, which functions as a transcriptional regulator and can be targeted by small molecules. The investigation identifies the natural compound coptisine (COP) as a potent binder that interacts with and stabilizes ATF4‐G4. For the first time, the high‐resolution structure of the COP‐ATF4‐G4 complex is determined. The formation of this stable complex disrupts the interaction between transcription factor AP‐2 alpha (TFAP2A) and ATF4‐G4, resulting in a substantial reduction in intracellular ATF4 levels and the eventual death of cancer cells. These seminal findings underscore the potential of targeting the ATF4‐G4 structure to yield significant therapeutic advantages within the realm of persister cancer cells induced by glutamine‐restricted therapy. [ABSTRACT FROM AUTHOR]

Over the years, microbiome research has achieved tremendous advancements driven by culture‐independent meta‐omics approaches. Despite extensive research, our understanding of the functional roles and causal effects of the microbiome on phenotypes remains limited. In this study, we focused on the rumen metaproteome, combining it with metatranscriptome and metabolome data to accurately identify the active functional distributions of rumen microorganisms and specific functional groups that influence feed efficiency. By integrating host genetics data, we established the potentially causal relationships between microbes‐proteins/metabolites‐phenotype, and identified specific patterns in which functional groups of rumen microorganisms influence host feed efficiency. We found a causal link between Selenomonas bovis and rumen carbohydrate metabolism, potentially mediated by bacterial chemotaxis and a two‐component regulatory system, impacting feed utilization efficiency of dairy cows. Our study on the nutrient utilization functional groups in the rumen of high‐feed‐efficiency dairy cows, along with the identification of key microbiota functional proteins and their potentially causal relationships, will help move from correlation to causation in rumen microbiome research. This will ultimately enable precise regulation of the rumen microbiota for optimized ruminant production. Highlights: We combined rumen metaproteome, metatranscriptome, and metabolome data to identify active functional distributions of rumen microorganisms influencing feed efficiency.By integrating host genetics data, we identified causal relationships between microbes, proteins/metabolites, and phenotypes.We found a causal link between Selenomonas bovis and rumen carbohydrate metabolism, suggesting its role in improving feed utilization efficiency in dairy cows. [ABSTRACT FROM AUTHOR]