Summary Background Until now, polymyxin resistance has involved chromosomal mutations but has never been reported via horizontal gene transfer. During a routine surveillance project on antimicrobial ...resistance in commensal Escherichia coli from food animals in China, a major increase of colistin resistance was observed. When an E coli strain, SHP45, possessing colistin resistance that could be transferred to another strain, was isolated from a pig, we conducted further analysis of possible plasmid-mediated polymyxin resistance. Herein, we report the emergence of the first plasmid-mediated polymyxin resistance mechanism, MCR-1, in Enterobacteriaceae. Methods The mcr-1 gene in E coli strain SHP45 was identified by whole plasmid sequencing and subcloning. MCR-1 mechanistic studies were done with sequence comparisons, homology modelling, and electrospray ionisation mass spectrometry. The prevalence of mcr-1 was investigated in E coli and Klebsiella pneumoniae strains collected from five provinces between April, 2011, and November, 2014. The ability of MCR-1 to confer polymyxin resistance in vivo was examined in a murine thigh model. Findings Polymyxin resistance was shown to be singularly due to the plasmid-mediated mcr-1 gene. The plasmid carrying mcr-1 was mobilised to an E coli recipient at a frequency of 10−1 to 10−3 cells per recipient cell by conjugation, and maintained in K pneumoniae and Pseudomonas aeruginosa . In an in-vivo model, production of MCR-1 negated the efficacy of colistin. MCR-1 is a member of the phosphoethanolamine transferase enzyme family, with expression in E coli resulting in the addition of phosphoethanolamine to lipid A. We observed mcr-1 carriage in E coli isolates collected from 78 (15%) of 523 samples of raw meat and 166 (21%) of 804 animals during 2011–14, and 16 (1%) of 1322 samples from inpatients with infection. Interpretation The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance. Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drug-resistant Gram-negative bacteria. Funding Ministry of Science and Technology of China, National Natural Science Foundation of China.
Summary
Starch degradation is a necessary process determining banana fruit quality during ripening. Many starch degradation‐related genes are well studied. However, the transcriptional regulation of ...starch degradation during banana fruit ripening remains poorly understood. In this study, we identified a MYB transcription factor (TF) termed MaMYB3, as a putative protein binding the promoter of MaGWD1, a member of glucan water dikinase (GWD) family which has been demonstrated as an important enzyme of starch degradation. MaMYB3 was ripening‐ and ethylene‐repressible, and its expression was negatively correlated with starch degradation. Acting as a nucleus‐localized transcriptional repressor, MaMYB3 repressed the transcription of 10 starch degradation‐related genes, including MaGWD1, MaSEX4, MaBAM7‐MaBAM8, MaAMY2B, MaAMY3, MaAMY3A, MaAMY3C, MaMEX1, and MapGlcT2‐1, by directly binding to their promoters. Interestingly, a previously identified activator of starch degradation‐related genes, MabHLH6, was also suppressed by MaMYB3. The ectopic overexpression of MaMYB3 in tomato down‐regulated the expression of starch degradation‐related genes, inhibited starch degradation and delayed fruit ripening. Based on these findings, we conclude that MaMYB3 negatively impacts starch degradation by directly repressing starch degradation‐related genes and MabHLH6, and thereby delays banana fruit ripening. Collectively, our study expands our understanding of the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.
Significance Statement
MaMYB3 negatively impacts starch degradation by the direct repression of MabHLH6 and starch degradation‐related genes, and thus delays banana fruit ripening. Our findings illustrate the complex transcriptional regulatory hierarchy modulating starch degradation during fruit ripening.
Scutellaria baicalensis root is traditionally used for the treatment of common cold, fever and influenza. Flavonoids are the major chemical components of S. baicalensis root.
To evaluate the ...therapeutic effects and action mechanism of flavonoids-enriched extract from S. baicalensis root (FESR) on acute lung injury (ALI) induced by influenza A virus (IAV) in mice.
The anti-influenza, anti-inflammatory and anti-complementary properties of FESR and the main flavonoids were evaluated in vitro. Mice were challenged intranasally with influenza virus H1N1 (A/FM/1/47) 2 h before treatment. FESR (50, 100 and 200 mg/kg) was administrated intragastrically. Baicalin (BG), the most abundant compound in FESR was given as reference control. Survival rates, life spans and lung indexes of IAV-infected mice were measured. Histopathological changes, virus levels, inflammatory markers and complement deposition in lungs were analyzed.
Compared with the main compound BG, FESR and lower content aglycones (baicalein, oroxylin A, wogonin and chrysin) in FESR significantly inhibited H1N1 activity in virus-infected Madin-Darby canine kidney (MDCK) cells and markedly decreased nitric oxide (NO) production from lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In vitro assays showed that FESR and BG had no anti-complementary activity whereas baicalein, oroxylin A, wogonin and chrysin exhibited obvious anti-complementary activity.
Oral administration of FESR effectively protected the IAV-infected mice, increased the survival rate (FESR: 67%; BG: 33%), decreased the lung index (FESR: 0.90; BG: 1.00) and improved the lung morphology in comparing with BG group. FESR efficiently decreased lung virus titers, reduced haemagglutinin (HA) titers and inhibited neuraminidase (NA) activities in lungs of IAV-infected mice. FESR modulated the inflammatory responses by decreasing the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1), and increasing the levels of interferon-γ (IFN-γ) and interleukin-10 (IL-10) in lung tissues. Although showing no anti-complementary activity in vitro, FESR obviously reduced complement deposition and decreased complement activation product level in the lung .
FESR has a great potential for the treatment of ALI induced by IAV and the underlying action mechanism might be closely associated with antiviral, anti-inflammatory and anti-complementary properties. Furthermore, FESR resulted in more potent therapeutic effect than BG in the treatment of IAV-induced ALI.
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Tumor repopulation is a major cause of radiotherapy failure. Previous investigations highlighted that dying tumor cells played vital roles in tumor repopulation through promoting proliferation of the ...residual tumor repopulating cells (TRCs). However, TRCs also suffer DNA damage after radiotherapy, and might undergo mitotic catastrophe under the stimulation of proliferative factors released by dying cells. Hence, we intend to find out how these paradoxical biological processes coordinated to potentiate tumor repopulation after radiotherapy.
Tumor repopulation models in vitro and in vivo were used for evaluating the therapy response and dissecting underlying mechanisms. RNA-seq was performed to find out the signaling changes and identify the significantly changed miRNAs. qPCR, western blot, IHC, FACS, colony formation assay, etc. were carried out to analyze the molecules and cells.
Exosomes derived from dying tumor cells induced G1/S arrest and promoted DNA damage response to potentiate survival of TRCs through delivering miR-194-5p, which further modulated E2F3 expression. Moreover, exosomal miR-194-5p alleviated the harmful effects of oncogenic HMGA2 under radiotherapy. After a latent time, dying tumor cells further released a large amount of PGE2 to boost proliferation of the recovered TRCs, and orchestrated the repopulation cascades. Of note, low-dose aspirin was found to suppress pancreatic cancer repopulation upon radiation via inhibiting secretion of exosomes and PGE2.
Exosomal miR-194-5p enhanced DNA damage response in TRCs to potentiate tumor repopulation. Combined use of aspirin and radiotherapy might benefit pancreatic cancer patients.
Summary
Although starch degradation has been well studied in model systems such as Arabidopsis leaves and cereal seeds, this process in starchy fruits during ripening, especially in bananas, is ...largely unknown. In this study, 38 genes encoding starch degradation‐related proteins were identified and characterized from banana fruit. Expression analysis revealed that 27 candidate genes were significantly induced during banana fruit ripening, with concomitant conversion of starch‐to‐sugars. Furthermore, iTRAQ‐based proteomics experiments identified 18 starch degradation‐associated enzymes bound to the surface of starch granules, of which 10 were markedly up‐regulated during ripening. More importantly, a novel bHLH transcription factor, MabHLH6, was identified based on a yeast one‐hybrid screening using MaGWD1 promoter as a bait. Transcript and protein levels of MabHLH6 were also increased during fruit ripening. Electrophoretic mobility shift assays, chromatin immunoprecipitation and transient expression experiments confirmed that MabHLH6 activates the promoters of 11 starch degradation‐related genes, including MaGWD1, MaLSF2, MaBAM1, MaBAM2, MaBAM8, MaBAM10, MaAMY3, MaAMY3C, MaISA2, MaISA3 and MapGlcT2‐2 by recognizing their E‐box (CANNTG) motifs present in the promoters. Collectively, these findings suggest that starch degradation during banana fruit ripening may be attributed to the complex actions of numerous enzymes related to starch breakdown at transcriptional and translational levels, and that MabHLH6 may act as a positive regulator of this process via direct activation of a series of starch degradation‐related genes.
Previous reports have confirmed that saponins (ginsenosides) derived from Panax ginseng. C. A. Meyer exerted obvious memory‐enhancing and antiaging effects, and the simpler the structure of ...ginsenosides, the better the biological activity. In this work, we aimed to explore the therapeutic effect and underlying molecular mechanism of 20(S)‐protopanaxatriol (PPT), the aglycone of panaxatriol‐type ginsenosides, by establishing D‐galactose (D‐gal)‐induced subacute brain aging model in mice. The results showed that PPT treatment (10 and 20 mg/kg) for 4 weeks could significantly restore the D‐gal (800 mg/kg for 8 weeks)‐induced impaired memory function, choline dysfunction, and redox system imbalance in mice. Meanwhile, PPT also significantly reduced the histopathological changes caused by D‐gal exposure. Moreover, PPT could increase TFEB/LAMP2 protein expression to promote mitochondrial autophagic flow. Importantly, the results from molecular docking showed that PPT had good binding ability with LAMP2 and TFEB, suggesting that TFEB/LAMP2 might play an important role in PPT to alleviate D‐gal‐caused brain aging.
T-Cell Protein Tyrosine Phosphatase (TCPTP, PTPN2) is a non-receptor type protein tyrosine phosphatase that is ubiquitously expressed in human cells. TCPTP is a critical component of a variety of key ...signaling pathways that are directly associated with the formation of cancer and inflammation. Thus, understanding the molecular mechanism of TCPTP activation and regulation is essential for the development of TCPTP therapeutics. Under basal conditions, TCPTP is largely inactive, although how this is achieved is poorly understood. By combining biomolecular nuclear magnetic resonance spectroscopy, small-angle X-ray scattering, and chemical cross-linking coupled with mass spectrometry, we show that the C-terminal intrinsically disordered tail of TCPTP functions as an intramolecular autoinhibitory element that controls the TCPTP catalytic activity. Activation of TCPTP is achieved by cellular competition, i.e., the intrinsically disordered cytosolic tail of Integrin-α1 displaces the TCPTP autoinhibitory tail, allowing for the full activation of TCPTP. This work not only defines the mechanism by which TCPTP is regulated but also reveals that the intrinsically disordered tails of two of the most closely related PTPs (PTP1B and TCPTP) autoregulate the activity of their cognate PTPs via completely different mechanisms.
The triad types of molecules with various combinations of electron donors (D) and acceptors (A) have been widely explored in optoelectronics. However, their photophysical and photochemical ...properties, which are frequently unconventional, are relatively unexplored. In this study, a donor–donor–acceptor (D–D–A)-type triad, CTPS, consisting of the donor moiety of triphenylamine (D1) and the acceptor moiety of dibenzothiophene sulfone (A) bridging through the second donor carbazole (D2) into a U-shape configuration, was synthesized. CTPS exhibited dual emission bands, both of which reveal solvent-polarity-dependent solvatochromism and unusual excitation-wavelength-dependent ratiometric emission. Comprehensive studies clarified that two emissions originate from two different D–A charge-transfer (CT) states. The lower-energy CT(S) state possesses D1 → A through-space CT nature with optically forbidden transition, whereas the higher-lying CT(B) state is associated with optically allowed D2 → A CT through the π-conjugation transition. Upon S0 → CT(B) excitation, the charge transfer creates D2δ+Aδ− dipolar changes and Aδ−–D1 repulsion, leading to structural relaxation of the CT(B) state that competes with fast CT(B) → CT(S) internal conversion. Therefore, despite the fact that they originate from the same Franck–Condon excited state, both energy-stabilized CT(B) and CT(S) states are populated through two independent channels. The stabilized CT(B) and CT(S) states possess different optimized geometries and do not interconvert during their lifespans, rendering different population decay time constants. The slim highest occupied molecular orbital/lowest unoccupied molecular orbital overlapped D1–A CT(S) state exhibits thermally activated delayed fluorescence (TADF), the character of which was further exploited as a host in organic light-emitting diode. The results gain new insights into the properties of the bending-type D–D–A TADF triads. CTPS should not be a unique case. Bizarre photophysical behavior encountered in molecules comprising multiple D and A groups may involve the interplay among various local CT states, which might have been overlooked.
Stress cardiac magnetic resonance imaging (CMR) has demonstrated excellent diagnostic and prognostic value in single-center studies.
This study sought to investigate the prognostic value of stress ...CMR and downstream costs from subsequent cardiac testing in a retrospective multicenter study in the United States.
In this retrospective study, consecutive patients from 13 centers across 11 states who presented with a chest pain syndrome and were referred for stress CMR were followed for a target period of 4 years. The authors associated CMR findings with a primary outcome of cardiovascular death or nonfatal myocardial infarction using competing risk-adjusted regression models and downstream costs of ischemia testing using published Medicare national payment rates.
In this study, 2,349 patients (63 ± 11 years of age, 47% female) were followed for a median of 5.4 years. Patients with no ischemia or late gadolinium enhancement (LGE) by CMR, observed in 1,583 patients (67%), experienced low annualized rates of primary outcome (<1%) and coronary revascularization (1% to 3%), across all years of study follow-up. In contrast, patients with ischemia+/LGE+ experienced a >4-fold higher annual primary outcome rate and a >10-fold higher rate of coronary revascularization during the first year after CMR. Patients with ischemia and LGE both negative had low average annual cost spent on ischemia testing across all years of follow-up, and this pattern was similar across the 4 practice environments of the participating centers.
In a multicenter U.S. cohort with stable chest pain syndromes, stress CMR performed at experienced centers offers effective cardiac prognostication. Patients without CMR ischemia or LGE experienced a low incidence of cardiac events, little need for coronary revascularization, and low spending on subsequent ischemia testing. (Stress CMR Perfusion Imaging in the United States SPINS: A Society for Cardiovascular Resonance Registry Study; NCT03192891)
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