Placing steroid hormones within the human ABCC3 transporter reveals a compatible amphiphilic substrate-binding pocket.

The human ABC transporter ABCC3 (also known as MRP3) transports a wide spectrum of substrates, including endogenous metabolites and exogenous drugs. Accordingly, it participates in multiple physiological processes and is involved in diverse human diseases such as intrahepatic cholestasis of pregnancy, which is caused by the intracellular accumulation of bile acids and estrogens. Here, we report three cryogenic electron microscopy structures of ABCC3: in the apo-form and in complexed forms bound to either the conjugated sex hormones ß-estradiol 17-(ß-D-glucuronide) and dehydroepiandrosterone sulfate. For both hormones, the steroid nuclei that superimpose against each other occupy the hydrophobic center of the transport cavity, whereas the two conjugation groups are separated and fixed by the hydrophilic patches in two transmembrane domains. Structural analysis combined with site-directed mutagenesis and ATPase activity assays revealed that ABCC3 possesses an amphiphilic substrate-binding pocket able to hold either conjugated hormone in an asymmetric pattern. These data build on consensus features of the substrate-binding pocket of MRPs and provide a structural platform for the rational design of inhibitors.

New insights on the photocomplex of Roseiflexus castenholzii revealed from comparisons of native and carotenoid-depleted complexes.

In wild-type phototrophic organisms, carotenoids (Crts) are primarily packed into specific pigment-protein complexes along with (Bacterio)chlorophylls and play important roles in the photosynthesis. Diphenylamine (DPA) inhibits carotenogenesis but not phototrophic growth of anoxygenic phototrophs and eliminates virtually all Crts from photocomplexes. To investigate the effect of Crts on assembly of the reaction center-light-harvesting (RC-LH) complex from the filamentous anoxygenic phototroph Roseiflexus (Rfl.) castenholzii, we generated carotenoidless (Crt-less) RC-LH complexes by growing cells in the presence of DPA. Here, we present cryo-EM structures of the Rfl. castenholzii native and Crt-less RC-LH complexes with resolutions of 2.86 Å and 2.85 Å, respectively. From the high-quality map obtained, several important but previously unresolved details in the Rfl. castenholzii RC-LH structure were determined unambiguously including the assignment and likely function of three small polypeptides, and the content and spatial arrangement of Crts with bacteriochlorophyll molecules. The overall structures of Crt-containing and Crt-less complexes are similar. However, structural comparisons showed that only five Crts remain in complexes from DPA-treated cells and that the subunit X (TMx) flanked on the N-terminal helix of the Cyt-subunit is missing. Based on these results, the function of Crts in the assembly of the Rfl. castenholzii RC-LH complex and the molecular mechanism of quinone exchange is discussed. These structural details provide a fresh look at the photosynthetic apparatus of an evolutionary ancient phototroph as well as new insights into the importance of Crts for proper assembly and functioning of the RC-LH complex.

Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium, Halorhodospira halochloris.

Halorhodospira (Hlr.) halochloris is a triply extremophilic phototrophic purple sulfur bacterium, as it is thermophilic, alkaliphilic, and extremely halophilic. The light-harvesting-reaction center (LH1-RC) core complex of this bacterium displays an LH1-Qy transition at 1,016 nm, which is the lowest-energy wavelength absorption among all known phototrophs. Here we report the cryo-EM structure of the LH1-RC at 2.42 Å resolution. The LH1 complex forms a tricyclic ring structure composed of 16 αßγ-polypeptides and one αß-heterodimer around the RC. From the cryo-EM density map, two previously unrecognized integral membrane proteins, referred to as protein G and protein Q, were identified. Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC L-subunit and are absent from the LH1-RC complexes of all other purple bacteria of which the structures have been determined so far. Besides bacteriochlorophyll b molecules (B1020) located on the periplasmic side of the Hlr. halochloris membrane, there are also two arrays of bacteriochlorophyll b molecules (B800 and B820) located on the cytoplasmic side. Only a single copy of a carotenoid (lycopene) was resolved in the Hlr. halochloris LH1-α3ß3 and this was positioned within the complex. The potential quinone channel should be the space between the LH1-α3ß3 that accommodates the single lycopene but does not contain a γ-polypeptide, B800 and B820. Our results provide a structural explanation for the unusual Qy red shift and carotenoid absorption in the Hlr. halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

Development and validation of a coagulation-related genes prognostic model for hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) has a high incidence and mortality worldwide, which seriously threatens people's physical and mental health. Coagulation is closely related to the occurrence and development of HCC. Whether coagulation-related genes (CRGs) can be used as prognostic markers for HCC remains to be investigated. METHODS: Firstly, we identified differentially expressed coagulation-related genes of HCC and control samples in the datasets GSE54236, GSE102079, TCGA-LIHC, and Genecards database. Then, univariate Cox regression analysis, LASSO regression analysis, and multivariate Cox regression analysis were used to determine the key CRGs and establish the coagulation-related risk score (CRRS) prognostic model in the TCGA-LIHC dataset. The predictive capability of the CRRS model was evaluated by Kaplan-Meier survival analysis and ROC analysis. External validation was performed in the ICGC-LIRI-JP dataset. Besides, combining risk score and age, gender, grade, and stage, a nomogram was constructed to quantify the survival probability. We further analyzed the correlation between risk score and functional enrichment, pathway, and tumor immune microenvironment. RESULTS: We identified 5 key CRGs (FLVCR1, CENPE, LCAT, CYP2C9, and NQO1) and constructed the CRRS prognostic model. The overall survival (OS) of the high-risk group was shorter than that of the low-risk group. The AUC values for 1 -, 3 -, and 5-year OS in the TCGA dataset were 0.769, 0.691, and 0.674, respectively. The Cox analysis showed that CRRS was an independent prognostic factor for HCC. A nomogram established with risk score, age, gender, grade, and stage, has a better prognostic value for HCC patients. In the high-risk group, CD4+T cells memory resting, NK cells activated, and B cells naive were significantly lower. The expression levels of immune checkpoint genes in the high-risk group were generally higher than that in the low-risk group. CONCLUSIONS: The CRRS model has reliable predictive value for the prognosis of HCC patients.

Effect and Mechanism of Curdione Combined with Gemcitabine on Migration and Invasion of Bladder Cancer.

Bladder cancer (BCa), which usually occurs in bladder epithelial cells and is the fifth most common type of cancer in the world. he recurrence rate within 5 years after surgery is 0.8-45% of patients with early bladder cancer. Therefore, finding appropriate drug therapy for patients with bladder cancer can provide a reference for clinical treatment and play an important role in improving the prognosis of patients. In this study, CCK8 assay result showed that the inhibition of bladder cancer cell activity by Curdione and GEM increased with time and dose. Subsequently, CCK8, clone formation assay and Transwell result showed Curdione enhances GEM inhibition of bladder cancer cell activity, clonal formation and migration, these combine therapeutic schedule also could inhibited growth of in vivo xenograft tumors. The comprehensive database showed that CA2 is a potential target genes of Curdione, and Knockdown CA2 enhances GEM induced inhibition of cell proliferation and migration. Based on these advantages, Curdione may be a new type of action drug or adjunct for the treatment of bladder cancer.

Effect of dapagliflozin on the prognosis of patients with acute myocardial infarction undergoing percutaneous coronary intervention.

BACKGROUND AND AIMS: The effect of dapagliflozin (DAPA) on the prognosis of patients with acute myocardial infarction (AMI) is unclear. The present study was conducted to evaluate the association between DAPA administration and adverse events in patients with AMI undergoing percutaneous coronary intervention (PCI). METHODS: This single-center retrospective analysis study included a total of 786 patients with AMI from January 2019 to August 2021 who were or were not administered DAPA at discharge. The primary endpoint was the composite of major adverse cardiovascular events (MACE), including overall deaths, heart failure, nonfatal MI, nonfatal stroke, and unplanned repeat revascularization (URR). Differences in the triglyceride glucose (TyG) index and the atherogenic index of plasma (AIP) both during hospitalization and 12 months after discharge (if achievable) were also compared. RESULTS: During a median follow-up of 23 months, 130 patients had MACE (118 in the DAPA-free group and 12 in the DAPA group). Kaplan-Meier survival analyses revealed that the cumulative incidence of MACE (log-rank test, p = 0.009), heart failure (p = 0.003), nonfatal MI (p = 0.005), and URR (p = 0.031) was higher in the DAPA-free group. In addition, the multivariate Cox analysis showed that DAPA was significantly associated with the reduced risk of MACE (hazard ratio = 0.170, 95% confidence interval = 0.078-0.373, p < 0.001). Considering each specific adverse event, the DAPA-free group was associated with heart failure, nonfatal MI, and URR in multivariate Cox regression analyses. Stratification analyses suggested that DAPA has a strong protective effect in patients with AMI of advanced age with concomitant diabetes or those who are not on angiotensin receptor enkephalinase inhibitors. Furthermore, the TyG index and AIP of the patients 12 months after DAPA administration at discharge were significantly lower than those during hospitalization. CONCLUSIONS: DAPA is an independent protective factor against MACE and may provide incremental prognostic information in patients with AMI undergoing PCI.

Mechanism of Catalytic Transfer Hydrogenation for Furfural Using Single Ni Atom Catalysts Anchored to Nitrogen-Doped Graphene Sheets.

Catalytic transfer hydrogenation (CTH) of α,ß-unsaturated aldehydes using single metal atom catalysts supported on nitrogen-incorporated graphene sheet (M-Nx-Gr) materials has attracted increasing attention recently, yet the reaction mechanism remains to be explored. Compared to the Ni-N4-Gr model in which the dissociation of isopropanol is highly unfavorable as a result of steric hindrance and inertness of the Ni-N4 site embedded in graphene, the Ni-N3 site in Ni-N3-Gr is more active and facilitates the formation of *H with isopropanol as the H donor, where the dissociation of H from isopropanol with an energy barrier of 0.83 eV is the rate-determining step. An alternative reaction path starts from the coadsorption of isopropanol and furfural molecules at the Ni-N3 site, followed by a direct hydrogen transfer between the two molecules; however, the rate-determining step has a much higher energy barrier of 1.32 eV. Our calculations suggest that the hydrogenation of the aldehyde group is kinetically more favorable than the C═C hydrogenation, revealing the high chemoselectivity of furfural to furfuryl alcohol. Our investigations reveal that the CTH mechanism using the Ni-N3-Gr catalyst is different from that on traditional metal oxides, where the former has only one single active site, while two active sites are required for the latter. The proposed reaction mechanism of CTH for furfural in this study should be helpful to guide the design of single metal atom catalysts with appropriate N coordination for application in chemoselective hydrogenation reactions.

Theoretical understanding on all-solid frustrated Lewis pair sites of C2N anchored by single metal atom.

The design of all-solid heterogeneous catalysts with frustrated Lewis pairs (FLPs) has attracted much attention recently because of their appealing low dissociation energy for H2 molecules due to which a promotion of hydrogenation reaction is expected. The sterically encumbered Lewis acid (metal site) and base (nitrogen site) in the cavity of single transition metal atom-doped M/C2N sheets make them potential candidates for the design of catalysts with FLPs, while a comprehensive understanding of their intrinsic property and reactivity is still lacking. Calculations show that the complete dissociation of the H2 molecule into two H* states at the N sites requires two steps: heterolytic cleavage of the H2 molecule and the transfer of H* from the metal site to the N site, which are strongly related to the acidity of the metal site. Ni/C2N and Pd/C2N, which outperform the other eight transition metal atom (M) anchored M/C2N candidates, possess low energy barriers for the complete dissociation of H2 molecules, with values of only 0.30 and 0.20 eV, respectively. Furthermore, both Ni/C2N and Pd/C2N catalysts can achieve semi-hydrogenation of C2H2 into C2H4, with overall barriers of 0.81 and 0.75 eV, respectively, which are lower than those reported for many other catalysts. It is speculated that M/C2N catalysts with intrinsic FLPs may also find applications in other important hydrogenation reactions.

Disturbance of serum lipid metabolites and potential biomarkers in the Bleomycin model of pulmonary fibrosis in young mice.

BACKGROUND: Altered metabolic pathways have recently been considered as potential drivers of idiopathic pulmonary fibrosis (IPF) for the study of drug therapeutic targets. However, our understanding of the metabolite profile during IPF formation is lacking. METHODS: To comprehensively characterize the metabolic disorders of IPF, a mouse IPF model was constructed by intratracheal injection of bleomycin into C57BL/6J male mice, and lung tissues from IPF mice at 7 days, 14 days, and controls were analyzed by pathology, immunohistochemistry, and Western Blots. Meanwhile, serum metabolite detections were conducted in IPF mice using LC-ESI-MS/MS, KEGG metabolic pathway analysis was applied to the differential metabolites, and biomarkers were screened using machine learning algorithms. RESULTS: We analyzed the levels of 1465 metabolites and found that more than one-third of the metabolites were altered during IPF formation. There were 504 and 565 metabolites that differed between M7 and M14 and controls, respectively, while 201 differential metabolites were found between M7 and M14. In IPF mouse sera, about 80% of differential metabolite expression was downregulated. Lipids accounted for more than 80% of the differential metabolite species with down-regulated expression. The KEGG pathway enrichment analysis of differential metabolites was mainly enriched to pathways such as the metabolism of glycerolipids and glycerophospholipids. Eight metabolites were screened by a machine learning random forest model, and receiver operating characteristic curves (ROC) assessed them as ideal diagnostic tools. CONCLUSIONS: In conclusion, we have identified disturbances in serum lipid metabolism associated with the formation of pulmonary fibrosis, contributing to the understanding of the pathogenesis of pulmonary fibrosis.

Identification of antidiabetic components in Uncariae Rammulus Cum Uncis based on phytochemical isolation and spectrum-effect relationship analysis.

OBJECTIVES: Uncariae Rammulus Cum Uncis (URCU) is a commonly used herbal medicine to treat diabetes. This work is aimed to discover and identify the antidiabetic components from URCU extract. METHODS: Column chromatography and recrystallisation were used to separate individual compounds from URCU extract, and the obtained individual compounds were used for determination of α-glucosidase inhibitory activity. Molecular docking was applied to predict the molecular interactions. High-performance liquid chromatography (HPLC) was used for fingerprint analysis of 12 batches of URCU. HPLC fingerprints were assessed by the similarity analysis (SA) and hierarchical clustering analysis (HCA). The spectrum-effect relationship analysis of URCU was assessed by orthogonal partial least squares (OPLS) and bivariate correlation analysis (BCA). RESULTS: A total of 10 potential bioactive compounds were isolated and six of them showed potent α-glucosidase inhibitory activity (IC50 = 4.21-166.10 µM). The molecular docking results revealed that the binding energy was consistent with the results of α-glucosidase inhibition activity analysis (-8.55 to -4.84 kcal/mol). The ethanol extracts of the 12 batches of URCU showed inhibitory effect on α-glucosidase in a dose-dependent manner, and the IC50 values ranged from 0.94 µg/mL to 12.57 µg/mL. The spectrum-effect relationship analysis results indicated that 13 peaks might be potential antidiabetic compounds in URCU, including 18 (hyperoside) and 19 (rutin). CONCLUSION: A comprehensive connection between URCU chemical components and α-glucosidase inhibitory activity was established for the first time by using a spectrum-effect relationship model, which might be applicable to the quality control of URCU.

Clinical treatment outcomes and their changes in extremely preterm twins: a multicenter retrospective study in Guangdong Province, China. / è¶ æœªæˆç†ŸåŒèƒŽå„¿ä¸´åºŠæ•‘æ²»ç»“å±€åŠå˜åŒ–åˆ†æžï¼šä¸€é¡¹å¹¿ä¸œçœå¤šä¸­å¿ƒå›žé¡¾æ€§ç ”ç©¶.

OBJECTIVES: To investigate the clinical treatment outcomes and the changes of the outcomes over time in extremely preterm twins in Guangdong Province, China. METHODS: A retrospective analysis was performed for 269 pairs of extremely preterm twins with a gestational age of <28 weeks who were admitted to the department of neonatology in 26 grade A tertiary hospitals in Guangdong Province from January 2008 to December 2017. According to the admission time, they were divided into two groups: 2008-2012 and 2013-2017. Besides, each pair of twins was divided into the heavier infant and the lighter infant subgroups according to birth weight. The perinatal data of mothers and hospitalization data of neonates were collected. The survival rate of twins and the incidence rate of complications were compared between the 2008-2012 and 2013-2017 groups. RESULTS: Compared with the 2008-2012 group, the 2013-2017 group (both the heavier infant and lighter infant subgroups) had lower incidence rates of severe asphyxia and smaller head circumference at birth (P<0.05). The mortality rates of both of the twins, the heavier infant of the twins, and the lighter infant of the twins were lower in the 2013-2017 group compared with the 2008-2012 group (P<0.05). Compared with the 2008-2012 group, the 2013-2017 group (both the heavier infant and lighter infant subgroups) had lower incidence rates of pulmonary hemorrhage, patent ductus arteriosus (PDA), periventricular-intraventricular hemorrhage (P-IVH), and neonatal respiratory distress syndrome (NRDS) and a higher incidence rate of bronchopulmonary dysplasia (P<0.05). CONCLUSIONS: There is a significant increase in the survival rate over time in extremely preterm twins with a gestational age of <28 weeks in the 26 grade A tertiary hospitals in Guangdong Province. The incidences of severe asphyxia, pulmonary hemorrhage, PDA, P-IVH, and NRDS decrease in both the heavier and lighter infants of the twins, but the incidence of bronchopulmonary dysplasia increases. With the improvement of diagnosis and treatment, the multidisciplinary collaboration between different fields of fetal medicine including prenatal diagnosis, obstetrics, and neonatology is needed in the future to jointly develop management strategies for twin pregnancy.

Cyclic-di-GMP binds to histidine kinase RavS to control RavS-RavR phosphotransfer and regulates the bacterial lifestyle transition between virulence and swimming.

The two-component signalling system (TCS) comprising a histidine kinase (HK) and a response regulator (RR) is the predominant bacterial sense-and-response machinery. Because bacterial cells usually encode a number of TCSs to adapt to various ecological niches, the specificity of a TCS is in the centre of regulation. Specificity of TCS is defined by the capability and velocity of phosphoryl transfer between a cognate HK and a RR. Here, we provide genetic, enzymology and structural data demonstrating that the second messenger cyclic-di-GMP physically and specifically binds to RavS, a HK of the phytopathogenic, gram-negative bacterium Xanthomonas campestris pv. campestris. The [c-di-GMP]-RavS interaction substantially promotes specificity between RavS and RavR, a GGDEF-EAL domain-containing RR, by reinforcing the kinetic preference of RavS to phosphorylate RavR. [c-di-GMP]-RavS binding effectively decreases the phosphorylation level of RavS and negatively regulates bacterial swimming. Intriguingly, the EAL domain of RavR counteracts the above regulation by degrading c-di-GMP and then increasing the level of phosphorylated RavS. Therefore, RavR acts as a bifunctional phosphate sink that finely controls the level of phosphorylated RavS. These biochemical processes interactively modulate the phosphoryl flux between RavS-RavR and bacterial lifestyle transition. Our results revealed that c-di-GMP acts as an allosteric effector to dynamically modulate specificity between HK and RR.

Single non-noble metal atom doped C2N catalysts for chemoselective hydrogenation of 3-nitrostyrene.

Improving the reaction selectivity and activity for challenging substrates such as nitroaromatics bearing two reducible functional groups is important in industry, yet remains a great challenge using traditional metal nanoparticle based catalysts. In this study, single metal atom doped M-C2N catalysts were theoretically screened for selective hydrogenation of 3-nitrostyrene to 3-vinylaniline with H2 as the H-source. Among 20 M-C2N catalysts, the non-noble Mn-C2N catalyst was found to have excellent reaction selectivity. Importantly, due to the solid frustrated Lewis pair sites in the pores of Mn-C2N, a low H2 activation energy is achieved on high-spin Mn-C2N and the rate-determining step for the hydrogenation reactions is the H diffusion from the metal site to the N site. The unraveled mechanism of the hydrogenation of 3-nitrostyrene using Mn-C2N enriches the applications of Mn based catalysts and demonstrates its excellent properties for catalyzing the challenging hydrogenation reaction of substrates with two reducible functional groups.

Changes in acid-base status in oxygen toxicity at 230 kPa oxygen as a function of exposure time.

Breathing less than 50 kPa of oxygen over time can lead to pulmonary oxygen toxicity (POT). Vital capacity (VC) as the sole parameter for POT has its limitations. In this study we try to find out the changes of acid-base status in a POT rat model. Fifty male rats were randomly divided into five groups, exposed to 230 kPa oxygen for three, six, nine and 12 hours, respectively. Rats exposed to air were used as controls. After exposure the mortality and behavior of rats were observed. Arterial blood samples were collected for acid-base status detection and wet-dry (W/D) ratios of lung tissues were tested. Results showed that the acid-base status in rats exposed to 230 kPa oxygen presented a dynamic change. The primary status was in the compensatory period when primary respiratory acidosis was mixed with compensated metabolic alkalosis. Then the status changed to decompensated alkalosis and developed to decompensated acidosis in the end. pH, PCO2, HCO3-, TCO2, and BE values had two phases: an increase and a later decrease with increasing oxygen exposure time, while PaO2 and lung W/D ratio showed continuously increasing trends with the extension of oxygen exposure time. Lung W/D ratio was significantly associated with PaO2 (r = 0.6385, p = 0.002), while other parameters did not show a significant correlation. It is concluded that acid-base status in POT rats presents a dynamic change: in the compensatory period first, then turns to decompensated alkalosis and ends up with decompensated acidosis status. Blood gas analysis is a useful method to monitor the development of POT.

Plasmodium yoelii 17XL infection modified maturation and function of dendritic cells by skewing Tregs and amplificating Th17.

BACKGROUND: Emerging data has suggested that Tregs, Th17, Th1 and Th2 are correlated with early immune mechanisms by controlling Plasmodium infection. Plasmodium infection appeared to impair the antigen presentation and maturation of DCs, leading to attenuation of specific cellular immune response ultimately. Hence, in this study, we aim to evaluate the relevance between DCs and Tregs/Th17 populations in the process and outcomes of infection with Plasmodium yoelii 17XL (P.y17XL). METHODS: DCs detection/analysis dynamically was performed by Tregs depletion or Th17 neutralization in P.y17XL infected BALB/c mice via flow cytometry. Then the levels of cytokines production were detected using enzyme-linked mmunosorbent assay (ELISA). RESULTS: Our results indicated that Tregs depletion or Th17 neutralization in BALB/c mice infected with P.y17XL significantly up-regulated the percentages of mDC and pDC, increased the expressions of major histocompatibility complex (MHC) class II, CD80, CD86 on DCs and the levels of IL-10/IL-12 secreted by DCs, indicating that abnormal amplification of Tregs or Th17 may damage the maturation and function of DCs during the early stage of malaria infection. Interestingly, we also found that the abnormal amplification of Th17, as well as Tregs, could inhibit the maturation of DCs. CONCLUSIONS: Tregs skewing or Th17 amplification during the early stage of malaria infection may inhibit the maturation and function of DCs by modifying the subsets of DCs, expressions of surface molecules on DCs and secretion mode of cytokines.

The relationship between elevated serum uric acid and arterial stiffness in a healthy population.

OBJECTIVE: This study aims to investigate the relationship between serum uric acid and arterial stiffness in a healthy population. METHODS: Among the 979 participants, baPWV was non-invasively measured, the circulating levels of uric acid were tested, and the uric acid polymorphisms (rs2231142 and rs11722228) were genotyped. Then, the Mendelian randomization method was employed to test the relationship between serum uric acid and arterial stiffness in a healthy population. RESULTS: After adjusting for age, gender, antihypertensive medication, body mass index, waist-to-hip ratio, urea nitrogen, creatinine and diabetic mellitus, there was a significant allelic difference in uric acid levels for each genotype (P < 0.0001 for rs2231142; P = 0.007 for rs11722228). However, there were no differences on the potential confounders between the genotypes of rs2231142 and rs11722228 (P > 0.05). The baPWV was significantly associated with circulating levels of uric acid after adjusting for cardiovascular risk factors and other potential confounders (P = 0.002). However, neither the single polymorphism, nor the accumulation of culprit alleles was associated with baPWV (P = 0.92 for rs2231142; P = 0.60 for rs11722228; P for trend = 0.77 for the combined analysis of culprit alleles). CONCLUSION: These results do not support the causal role of circulating levels of uric acid in the development of arterial stiffness.

Fatty acid DSF binds and allosterically activates histidine kinase RpfC of phytopathogenic bacterium Xanthomonas campestris pv. campestris to regulate quorum-sensing and virulence.

As well as their importance to nutrition, fatty acids (FA) represent a unique group of quorum sensing chemicals that modulate the behavior of bacterial population in virulence. However, the way in which full-length, membrane-bound receptors biochemically detect FA remains unclear. Here, we provide genetic, enzymological and biophysical evidences to demonstrate that in the phytopathogenic bacterium Xanthomonas campestris pv. campestris, a medium-chain FA diffusible signal factor (DSF) binds directly to the N-terminal, 22 amino acid-length sensor region of a receptor histidine kinase (HK), RpfC. The binding event remarkably activates RpfC autokinase activity by causing an allosteric change associated with the dimerization and histidine phosphotransfer (DHp) and catalytic ATP-binding (CA) domains. Six residues were found essential for sensing DSF, especially those located in the region adjoining to the inner membrane of cells. Disrupting direct DSF-RpfC interaction caused deficiency in bacterial virulence and biofilm development. In addition, two amino acids within the juxtamembrane domain of RpfC, Leu172 and Ala178, are involved in the autoinhibition of the RpfC kinase activity. Replacements of them caused constitutive activation of RpfC-mediated signaling regardless of DSF stimulation. Therefore, our results revealed a biochemical mechanism whereby FA activates bacterial HK in an allosteric manner, which will assist in future studies on the specificity of FA-HK recognition during bacterial virulence regulation and cell-cell communication.

Simvastatin decreases hyperbaric oxygen-induced acute lung injury by upregulating eNOS.

Statins, which are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase competitive inhibitors, not only lower blood cholesterol but also exert pleiotropic and beneficial effects in various diseases. However, the effects of statins on acute lung injury (ALI) induced by hyperbaric oxygen (HBO) have not been investigated. The present study is the first to investigate the effects of simvastatin in ALI induced by HBO in 8- to 9-wk-old C57BL/6 mice exposed to 0.23 MPa [=2.3 atmosphere absolute (ATA)] hyperoxia (≥95% O2) for 6 h. Mice were either given simvastatin (20 mg·kg·-1·day-1) in saline or a saline vehicle for 3 days before oxygen exposure. Lung tissue, serum, and bronchoalveolar lavage fluid (BALF) were collected for analysis of proapoptotic proteins, low-density lipoprotein cholesterol (LDL-C) levels, and lung inflammation. Simvastatin treatment significantly reduced lung permeability, serum LDL-C levels, tissue apoptosis, and inflammation. However, simvastatin treatment had no effect on antioxidant enzyme activity, nicotinamide adenine dinucleotide phosphate oxidase 4 (NADPH4) expression, and Akt phosphorylation levels. Furthermore, we investigated the role of endothelial nitric oxide synthase (eNOS) in simvastatin protection through inhibiting eNOS activity with NG-nitro-l-arginine methyl ester (l-NAME; 20 mg/kg). Results showed that the beneficial effects of simvastatin on ALI induced by HBO (antiinflammatory, antiapoptotic, lipid lowering, and reduction in lung permeability) were reversed. These results showed that simvastatin curbs HBO-induced lung edema, permeability, inflammation, and apoptosis via upregulating eNOS expression and that simvastatin could be an effective therapy to treat prolonged HBO exposure.

Two-Component Signaling System VgrRS Directly Senses Extracytoplasmic and Intracellular Iron to Control Bacterial Adaptation under Iron Depleted Stress.

Both iron starvation and excess are detrimental to cellular life, especially for animal and plant pathogens since they always live in iron-limited environments produced by host immune responses. However, how organisms sense and respond to iron is incompletely understood. Herein, we reveal that in the phytopathogenic bacterium Xanthomonas campestris pv. campestris, VgrS (also named ColS) is a membrane-bound receptor histidine kinase that senses extracytoplasmic iron limitation in the periplasm, while its cognate response regulator, VgrR (ColR), detects intracellular iron excess. Under iron-depleted conditions, dissociation of Fe3+ from the periplasmic sensor region of VgrS activates the VgrS autophosphorylation and subsequent phosphotransfer to VgrR, an OmpR-family transcription factor that regulates bacterial responses to take up iron. VgrR-VgrS regulon and the consensus DNA binding motif of the transcription factor VgrR were dissected by comparative proteomic and ChIP-seq analyses, which revealed that in reacting to iron-depleted environments, VgrR directly or indirectly controls the expressions of hundreds of genes that are involved in various physiological cascades, especially those associated with iron-uptake. Among them, we demonstrated that the phosphorylated VgrR tightly represses the transcription of a special TonB-dependent receptor gene, tdvA. This regulation is a critical prerequisite for efficient iron uptake and bacterial virulence since activation of tdvA transcription is detrimental to these processes. When the intracellular iron accumulates, the VgrR-Fe2+ interaction dissociates not only the binding between VgrR and the tdvA promoter, but also the interaction between VgrR and VgrS. This relieves the repression in tdvA transcription to impede continuous iron uptake and avoids possible toxic effects of excessive iron accumulation. Our results revealed a signaling system that directly senses both extracytoplasmic and intracellular iron to modulate bacterial iron homeostasis.

Overexpression of VpPR10.1 by an efficient transformation method enhances downy mildew resistance in V. vinifera.

KEY MESSAGE: Putrescine and spermidine increase the transformation efficiency of Vitis vinifera L. cv. Thompson seedless. Accumulation of VpPR10.1 in transgenic V. vinifera Thompson seedless, likely increases its resistance to downy mildew. A more efficient method is described for facilitating Agrobacterium-mediated transformation of Vitis vinifera L. cv. Thompson Seedless somatic embryogenesis using polyamines (PAs). The efficacies of putrescine, spermidine and spermine are identified at a range of concentrations (10 µM, 100 µM and 1 mM) added to the culture medium during somatic embryo growth. Putrescine (PUT) and spermidine (SPD) promote the recovery of proembryonic masses (PEM) and the development of somatic embryos (SE) after co-cultivation. Judging from the importance of the time-frame in genetic transformation, PAs added at the co-cultivation stage have a stronger effect than delayed selection treatments, which are superior to antibiotic treatments in the selection stage. Best embryogenic responses are with 1 mM PUT and 100 µM SPD added to the co-culture medium. Using the above method, a pathogenesis-related gene (VpPR10.1) from Chinese wild Vitis pseudoreticulata was transferred into Thompson Seedless for functional evaluation. The transgenic line, confirmed by western blot analysis, was inoculated with Plasmopara viticola to test for downy mildew resistance. Based on observed restrictions of hyphal growth and increases in H2O2 accumulation in the transgenic plants, the accumulation of VpPR10.1 likely enhanced the transgenic plants resistance to downy mildew.