Mutagenetic analysis of the biosynthetic pathway of tetramate bripiodionen bearing 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione skeleton.

BACKGROUND: Natural tetramates are a family of hybrid polyketides bearing tetramic acid (pyrrolidine-2,4-dione) moiety exhibiting a broad range of bioactivities. Biosynthesis of tetramates in microorganisms is normally directed by hybrid polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) machineries, which form the tetramic acid ring by recruiting trans- or cis-acting thioesterase-like Dieckmann cyclase in bacteria. There are a group of tetramates with unique skeleton of 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione, which remain to be investigated for their biosynthetic logics. RESULTS: Herein, the tetramate type compounds bripiodionen (BPD) and its new analog, featuring the rare skeleton of 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione, were discovered from the sponge symbiotic bacterial Streptomyces reniochalinae LHW50302. Gene deletion and mutant complementation revealed the production of BPDs being correlated with a PKS-NRPS biosynthetic gene cluster (BGC), in which a Dieckmann cyclase gene bpdE was identified by sit-directed mutations. According to bioinformatic analysis, the tetramic acid moiety of BPDs should be formed on an atypical NRPS module constituted by two discrete proteins, including the C (condensation)-A (adenylation)-T (thiolation) domains of BpdC and the A-T domains of BpdD. Further site-directed mutagenetic analysis confirmed the natural silence of the A domain in BpdC and the functional necessities of the two T domains, therefore suggesting that an unusual aminoacyl transthiolation should occur between the T domains of two NRPS subunits. Additionally, characterization of a LuxR type regulator gene led to seven- to eight-fold increasement of BPDs production. The study presents the first biosynthesis case of the natural molecule with 3-(2H-pyran-2-ylidene)pyrrolidine-2,4-dione skeleton. Genomic mining using BpdD as probe reveals that the aminoacyl transthiolation between separate NRPS subunits should occur in a certain population of NRPSs in nature.

A novel TNKS/USP25 inhibitor blocks the Wnt pathway to overcome multi-drug resistance in TNKS-overexpressing colorectal cancer.

Modulating Tankyrases (TNKS), interactions with USP25 to promote TNKS degradation, rather than inhibiting their enzymatic activities, is emerging as an alternative/specific approach to inhibit the Wnt/ß-catenin pathway. Here, we identified UAT-B, a novel neoantimycin analog isolated from Streptomyces conglobatus, as a small-molecule inhibitor of TNKS-USP25 protein-protein interaction (PPI) to overcome multi-drug resistance in colorectal cancer (CRC). The disruption of TNKS-USP25 complex formation by UAT-B led to a significant decrease in TNKS levels, triggering cell apoptosis through modulation of the Wnt/ß-catenin pathway. Importantly, UAT-B successfully inhibited the CRC cells growth that harbored high TNKS levels, as demonstrated in various in vitro and in vivo studies utilizing cell line-based and patient-derived xenografts, as well as APCmin/+ spontaneous CRC models. Collectively, these findings suggest that targeting the TNKS-USP25 PPI using a small-molecule inhibitor represents a compelling therapeutic strategy for CRC treatment, and UAT-B emerges as a promising candidate for further preclinical and clinical investigations.

Modified Hongyu Decoction promotes wound healing by activating the VEGF/PI3K/Akt signaling pathway.

Wound healing is a considerable problem for clinicians. Ever greater attention has been paid to the role of Chinese herbal monomers and compounds on wound healing. This study aims to elucidate the wound healing mechanism of Modified Hongyu Decoction (MHD) in vivo and in vitro. MHD wound healing activity in vivo was evaluated using an excision rat model. H and E staining, Masson's staining and immunofluorescence of wound tissue on days 7 and 14 were performed to evaluate the efficacy of MHD on wound healing. Subsequently, human umbilical vein endothelial cells (HUVECs) were used to evaluate wound healing characteristics in vitro. Cell Counting Kit-8 (CCK-8) and scratch assays were conducted to assess the effects of MHD on the proliferation and migration of HUVECs. The involvement of the VEGF/PI3K/Akt signaling pathway was assessed by western blotting. The rats in the MHD group displayed more neovascularization and collagen fibers. Western blotting of wound tissue showed that VEGF, PI3K, p-Akt and p-eNOS expression were significantly increased (p<0.05) in the MHD group. Cell Counting Kit-8 and scratch assays demonstrated that MHD promoted HUVECs proliferation and migration. MHD treatment significantly increased VEGF, PI3K, p-Akt and p-eNOS expression in HUVECs (p<0.05), which was inhibited by LY294002. Both in vivo and in vitro data indicated that MHD promotes wound healing by regulating the VEGF/PI3K/Akt signaling pathway.

Serine peptidase Vpr forms enzymatically active fibrils outside Bacillus bacteria revealed by cryo-EM.

Bacteria develop a variety of extracellular fibrous structures crucial for their survival, such as flagella and pili. In this study, we use cryo-EM to identify protein fibrils surrounding lab-cultured Bacillus amyloiquefaciens and discover an unreported fibril species in addition to the flagellar fibrils. These previously unknown fibrils are composed of Vpr, an extracellular serine peptidase. We find that Vpr assembles into fibrils in an enzymatically active form, potentially representing a strategy of enriching Vpr activities around bacterial cells. Vpr fibrils are also observed under other culture conditions and around other Bacillus bacteria, such as Bacillus subtilis, which may suggest a general mechanism across all Bacillus bacterial groups. Taken together, our study reveals fibrils outside the bacterial cell and sheds light on the physiological role of these extracellular fibrils.

Multiple regulation towards an all-in-one NiCuMo/MoOx heterostructure for improving alkaline hydrogen oxidation.

Herein, we report a multiple regulation strategy towards an all-in-one NiCuMo/MoOx heterostructure for the HOR, which exhibits ultrahigh HOR activity (j@0.05V = 4.63 mA cm-2) and excellent durability for almost 24 h for the synergistic regulation of Mo and Cu on the Ni electrode. This study provides a new strategy for designing efficient non-noble metal-based HOR catalysts.

Investigation of carbonyl amidation and O-methylation during biosynthesis of the pharmacophore pyridyl of antitumor piericidins.

Piericidins are a large family of bacterial α-pyridone antibiotics with antitumor activities such as their anti-renal carcinoma activity exhibited recently in nude mice. The backbones of piericidins are derived from ß, δ-diketo carboxylic acids, which are offloaded from a modular polyketide synthase (PKS) and putatively undergo a carbonyl amidation before α-pyridone ring formation. The tailoring modifications to the α-pyridone structure mainly include the verified hydroxylation and O-methylation of the C-4' position and an unidentified C-5' O-methylation. Here, we describe a piericidin producer, terrestrial Streptomyces conglobatus, which contains a piericidin biosynthetic gene cluster in two different loci. Deletion of the amidotransferase gene pieD resulted in the accumulation of two fatty acids that should be degraded from the nascent carboxylic acid released by the PKS, supporting the carbonyl amidation function of PieD during α-pyridone ring formation. Deletion of the O-methyltransferase gene pieB1 led to the production of three piericidin analogues lacking C-5' O-methylation, therefore confirming that PieB1 specifically catalyses the tailoring modification. Moreover, bioactivity analysis of the mutant-derived products provided clues regarding the structure-function relationship for antitumor activity. The work addresses two previously unidentified steps involved in pyridyl pharmacophore formation during piericidin biosynthesis, facilitating the rational bioengineering of the biosynthetic pathway towards valuable antitumor agents.

Biosynthesis of depsipeptides with a 3-hydroxybenzoate moiety and selective anticancer activities involves a chorismatase.

Neoantimycins are anticancer compounds of 15-membered ring antimycin-type depsipeptides. They are biosynthesized by a hybrid multimodular protein complex of nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS), typically from the starting precursor 3-formamidosalicylate. Examining fermentation extracts of Streptomyces conglobatus, here we discovered four new neoantimycin analogs, unantimycins B-E, in which 3-formamidosalicylates are replaced by an unusual 3-hydroxybenzoate (3-HBA) moiety. Unantimycins B-E exhibited levels of anticancer activities similar to those of the chemotherapeutic drug cisplatin in human lung cancer, colorectal cancer, and melanoma cells. Notably, they mostly displayed no significant toxicity toward noncancerous cells, unlike the serious toxicities generally reported for antimycin-type natural products. Using site-directed mutagenesis and heterologous expression, we found that unantimycin productions are correlated with the activity of a chorismatase homolog, the nat-hyg5 gene, from a type I PKS gene cluster. Biochemical analysis confirmed that the catalytic activity of Nat-hyg5 generates 3-HBA from chorismate. Finally, we achieved selective production of unantimycins B and C by engineering a chassis host. On the basis of these findings, we propose that unantimycin biosynthesis is directed by the neoantimycin-producing NRPS-PKS complex and initiated with the starter unit of 3-HBA. The elucidation of the biosynthetic unantimycin pathway reported here paves the way to improve the yield of these compounds for evaluation in oncotherapeutic applications.

Glipizide controlled-release tablets, with or without acarbose, improve glycaemic variability in newly diagnosed Type 2 diabetes.

1. The aim of the present study was to compare the effects of glipizide controlled-release (CR) tablets monotherapy with that of glipizide CR tablets plus acarbose on glycaemic variability in newly diagnosed Type 2 diabetes (T2DM) patients using a continuous glucose-monitoring system (CGMS). 2. Forty newly diagnosed T2DM patients whose glycated haemoglobin A1c (HbA1c) levels ranged from 7.0% to 9.8% were randomized to either monotherapy or combination therapy. Overall glycaemic control and blood glucose variability were evaluated by CGMS parameters. 3. After 8 weeks treatment, fasting and postprandial blood glucose, HbA1c, glycated albumin (GA), mean blood glucose (MBG), mean amplitude of glycaemic excursions (MAGE), postprandial incremental area under the curve (AUC(pp)) and homeostasis model assessment of insulin resistance decreased significantly in both groups (P < 0.01). There was also a significant decrease in the mean of daily differences (MODD) in the combination therapy group. Mean changes in MBG, MAGE, MODD and AUC(pp) were significantly greater in the combination therapy group than in the monotherapy group (all P < 0.01), whereas no significant differences were found in the mean changes of HbA1c and GA. Multivariate regression analysis showed that the decrement in AUC(pp) was significantly associated with decreases in MAGE. 4. In conclusion, glipizide CR tablets alone or in combination with acarbose can improve overall blood glucose levels and glycaemic variability. Combination therapy using glipizide CR tablets and acarbose was more effective in reducing intraday and day-to-day glycaemic variability than glipizide CR tablet monotherapy.