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1.
Cell ; 186(9): 1877-1894.e27, 2023 04 27.
Article in English | MEDLINE | ID: mdl-37116470

ABSTRACT

Negative-stranded RNA viruses can establish long-term persistent infection in the form of large intracellular inclusions in the human host and cause chronic diseases. Here, we uncover how cellular stress disrupts the metastable host-virus equilibrium in persistent infection and induces viral replication in a culture model of mumps virus. Using a combination of cell biology, whole-cell proteomics, and cryo-electron tomography, we show that persistent viral replication factories are dynamic condensates and identify the largely disordered viral phosphoprotein as a driver of their assembly. Upon stress, increased phosphorylation of the phosphoprotein at its interaction interface with the viral polymerase coincides with the formation of a stable replication complex. By obtaining atomic models for the authentic mumps virus nucleocapsid, we elucidate a concomitant conformational change that exposes the viral genome to its replication machinery. These events constitute a stress-mediated switch within viral condensates that provide an environment to support upregulation of viral replication.


Subject(s)
Mumps virus , Persistent Infection , Humans , Mumps virus/physiology , Nucleocapsid , Phosphoproteins/metabolism , Virus Replication
2.
Cell ; 186(23): 5068-5083.e23, 2023 11 09.
Article in English | MEDLINE | ID: mdl-37804830

ABSTRACT

Metabolic reprogramming is a hallmark of cancer. However, mechanisms underlying metabolic reprogramming and how altered metabolism in turn enhances tumorigenicity are poorly understood. Here, we report that arginine levels are elevated in murine and patient hepatocellular carcinoma (HCC), despite reduced expression of arginine synthesis genes. Tumor cells accumulate high levels of arginine due to increased uptake and reduced arginine-to-polyamine conversion. Importantly, the high levels of arginine promote tumor formation via further metabolic reprogramming, including changes in glucose, amino acid, nucleotide, and fatty acid metabolism. Mechanistically, arginine binds RNA-binding motif protein 39 (RBM39) to control expression of metabolic genes. RBM39-mediated upregulation of asparagine synthesis leads to enhanced arginine uptake, creating a positive feedback loop to sustain high arginine levels and oncogenic metabolism. Thus, arginine is a second messenger-like molecule that reprograms metabolism to promote tumor growth.


Subject(s)
Arginine , Carcinoma, Hepatocellular , Liver Neoplasms , Animals , Humans , Mice , Arginine/metabolism , Carcinoma, Hepatocellular/metabolism , Cell Line, Tumor , Lipid Metabolism , Liver Neoplasms/metabolism
3.
Nat Rev Mol Cell Biol ; 23(9): 603-622, 2022 09.
Article in English | MEDLINE | ID: mdl-35505252

ABSTRACT

The eukaryotic transcription apparatus synthesizes a staggering diversity of RNA molecules. The labour of nuclear gene transcription is, therefore, divided among multiple DNA-dependent RNA polymerases. RNA polymerase I (Pol I) transcribes ribosomal RNA, Pol II synthesizes messenger RNAs and various non-coding RNAs (including long non-coding RNAs, microRNAs and small nuclear RNAs) and Pol III produces transfer RNAs and other short RNA molecules. Pol I, Pol II and Pol III are large, multisubunit protein complexes that associate with a multitude of additional factors to synthesize transcripts that largely differ in size, structure and abundance. The three transcription machineries share common characteristics, but differ widely in various aspects, such as numbers of RNA polymerase subunits, regulatory elements and accessory factors, which allows them to specialize in transcribing their specific RNAs. Common to the three RNA polymerases is that the transcription process consists of three major steps: transcription initiation, transcript elongation and transcription termination. In this Review, we outline the common principles and differences between the Pol I, Pol II and Pol III transcription machineries and discuss key structural and functional insights obtained into the three stages of their transcription processes.


Subject(s)
DNA-Directed RNA Polymerases , Eukaryota , DNA-Directed RNA Polymerases/genetics , DNA-Directed RNA Polymerases/metabolism , Eukaryota/genetics , Eukaryota/metabolism , RNA , RNA Polymerase II/metabolism , Transcription, Genetic/genetics
4.
Cell ; 173(6): 1495-1507.e18, 2018 05 31.
Article in English | MEDLINE | ID: mdl-29706546

ABSTRACT

Quantitative mass spectrometry has established proteome-wide regulation of protein abundance and post-translational modifications in various biological processes. Here, we used quantitative mass spectrometry to systematically analyze the thermal stability and solubility of proteins on a proteome-wide scale during the eukaryotic cell cycle. We demonstrate pervasive variation of these biophysical parameters with most changes occurring in mitosis and G1. Various cellular pathways and components vary in thermal stability, such as cell-cycle factors, polymerases, and chromatin remodelers. We demonstrate that protein thermal stability serves as a proxy for enzyme activity, DNA binding, and complex formation in situ. Strikingly, a large cohort of intrinsically disordered and mitotically phosphorylated proteins is stabilized and solubilized in mitosis, suggesting a fundamental remodeling of the biophysical environment of the mitotic cell. Our data represent a rich resource for cell, structural, and systems biologists interested in proteome regulation during biological transitions.


Subject(s)
Cell Cycle , DNA/analysis , Proteome/analysis , Proteomics/methods , Chromatin Assembly and Disassembly , Cluster Analysis , HeLa Cells , Hot Temperature , Humans , Mass Spectrometry , Mitosis , Phosphorylation , Protein Processing, Post-Translational , Protein Stability , RNA Polymerase II/metabolism , Solubility
5.
Cell ; 164(5): 999-1014, 2016 Feb 25.
Article in English | MEDLINE | ID: mdl-26875865

ABSTRACT

Transcription factors (TFs) are thought to function with partners to achieve specificity and precise quantitative outputs. In the developing heart, heterotypic TF interactions, such as between the T-box TF TBX5 and the homeodomain TF NKX2-5, have been proposed as a mechanism for human congenital heart defects. We report extensive and complex interdependent genomic occupancy of TBX5, NKX2-5, and the zinc finger TF GATA4 coordinately controlling cardiac gene expression, differentiation, and morphogenesis. Interdependent binding serves not only to co-regulate gene expression but also to prevent TFs from distributing to ectopic loci and activate lineage-inappropriate genes. We define preferential motif arrangements for TBX5 and NKX2-5 cooperative binding sites, supported at the atomic level by their co-crystal structure bound to DNA, revealing a direct interaction between the two factors and induced DNA bending. Complex interdependent binding mechanisms reveal tightly regulated TF genomic distribution and define a combinatorial logic for heterotypic TF regulation of differentiation.


Subject(s)
GATA4 Transcription Factor/metabolism , Homeodomain Proteins/metabolism , Myocardium/cytology , Organogenesis , T-Box Domain Proteins/metabolism , Transcription Factors/metabolism , Animals , Cell Differentiation , Crystallography, X-Ray , Embryo, Mammalian/metabolism , Homeobox Protein Nkx-2.5 , Homeodomain Proteins/genetics , Mice , Mice, Transgenic , Models, Molecular , Myocardium/metabolism , Promoter Regions, Genetic , Protein Interaction Domains and Motifs , T-Box Domain Proteins/genetics , Transcription Factors/genetics
6.
Nature ; 608(7923): 626-631, 2022 08.
Article in English | MEDLINE | ID: mdl-35896743

ABSTRACT

Emissions of the critical ozone-depleting and greenhouse gas nitrous oxide (N2O) from soils and industrial processes have increased considerably over the last decades1-3. As the final step of bacterial denitrification, N2O is reduced to chemically inert N2 (refs. 1,4) in a reaction that is catalysed by the copper-dependent nitrous oxide reductase (N2OR) (ref. 5). The assembly of its unique [4Cu:2S] active site cluster CuZ requires both the ATP-binding-cassette (ABC) complex NosDFY and the membrane-anchored copper chaperone NosL (refs. 4,6). Here we report cryo-electron microscopy structures of Pseudomonas stutzeri NosDFY and its complexes with NosL and N2OR, respectively. We find that the periplasmic NosD protein contains a binding site for a Cu+ ion and interacts specifically with NosL in its nucleotide-free state, whereas its binding to N2OR requires a conformational change that is triggered by ATP binding. Mutually exclusive structures of NosDFY in complex with NosL and with N2OR reveal a sequential metal-trafficking and assembly pathway for a highly complex copper site. Within this pathway, NosDFY acts as a mechanical energy transducer rather than as a transporter. It links ATP hydrolysis in the cytoplasm to a conformational transition of the NosD subunit in the periplasm, which is required for NosDFY to switch its interaction partner so that copper ions are handed over from the chaperone NosL to the enzyme N2OR.


Subject(s)
Bacterial Proteins , Cryoelectron Microscopy , Nitrous Oxide , Oxidoreductases , Pseudomonas stutzeri , Adenosine Triphosphate/metabolism , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Bacterial Proteins/ultrastructure , Binding Sites , Copper/chemistry , Copper/metabolism , Cytoplasm/enzymology , Molecular Chaperones/metabolism , Nitrous Oxide/metabolism , Oxidoreductases/chemistry , Oxidoreductases/metabolism , Oxidoreductases/ultrastructure , Periplasm/enzymology , Protein Binding , Protein Conformation , Pseudomonas stutzeri/cytology , Pseudomonas stutzeri/enzymology
7.
Nat Methods ; 20(12): 1900-1908, 2023 Dec.
Article in English | MEDLINE | ID: mdl-37932397

ABSTRACT

Cryo-electron tomography (cryo-ET) allows for label-free high-resolution imaging of macromolecular assemblies in their native cellular context. However, the localization of macromolecules of interest in tomographic volumes can be challenging. Here we present a ligand-inducible labeling strategy for intracellular proteins based on fluorescent, 25-nm-sized, genetically encoded multimeric particles (GEMs). The particles exhibit recognizable structural signatures, enabling their automated detection in cryo-ET data by convolutional neural networks. The coupling of GEMs to green fluorescent protein-tagged macromolecules of interest is triggered by addition of a small-molecule ligand, allowing for time-controlled labeling to minimize disturbance to native protein function. We demonstrate the applicability of GEMs for subcellular-level localization of endogenous and overexpressed proteins across different organelles in human cells using cryo-correlative fluorescence and cryo-ET imaging. We describe means for quantifying labeling specificity and efficiency, and for systematic optimization for rare and abundant protein targets, with emphasis on assessing the potential effects of labeling on protein function.


Subject(s)
Neural Networks, Computer , Organelles , Humans , Cryoelectron Microscopy/methods , Ligands , Organelles/ultrastructure , Electron Microscope Tomography/methods
8.
Nature ; 586(7831): 796-800, 2020 10.
Article in English | MEDLINE | ID: mdl-32879490

ABSTRACT

Nuclear pore complexes (NPCs) fuse the inner and outer membranes of the nuclear envelope. They comprise hundreds of nucleoporins (Nups) that assemble into multiple subcomplexes and form large central channels for nucleocytoplasmic exchange1,2. How this architecture facilitates messenger RNA export, NPC biogenesis and turnover remains poorly understood. Here we combine in situ structural biology and integrative modelling with correlative light and electron microscopy and molecular perturbation to structurally analyse NPCs in intact Saccharomyces cerevisiae cells within the context of nuclear envelope remodelling. We find an in situ conformation and configuration of the Nup subcomplexes that was unexpected from the results of previous in vitro analyses. The configuration of the Nup159 complex appears critical to spatially accommodate its function as an mRNA export platform, and as a mediator of NPC turnover. The omega-shaped nuclear envelope herniae that accumulate in nup116Δ cells3 conceal partially assembled NPCs lacking multiple subcomplexes, including the Nup159 complex. Under conditions of starvation, herniae of a second type are formed that cytoplasmically expose NPCs. These results point to a model of NPC turnover in which NPC-containing vesicles bud off from the nuclear envelope before degradation by the autophagy machinery. Our study emphasizes the importance of investigating the structure-function relationship of macromolecular complexes in their cellular context.


Subject(s)
Cryoelectron Microscopy , Nuclear Pore/metabolism , Nuclear Pore/ultrastructure , Saccharomyces cerevisiae/cytology , Saccharomyces cerevisiae/ultrastructure , Autophagy , Models, Molecular , Nuclear Pore/chemistry , Nuclear Pore Complex Proteins/metabolism , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Tomography
9.
EMBO Rep ; 24(7): e57498, 2023 Jul 05.
Article in English | MEDLINE | ID: mdl-37227159

ABSTRACT

The surprising decision by Novo Nordisk Foundation (NNF) to discontinue funding for the Center for Protein Research in Copenhagen should prompt discussions about public and private commitment to support basic research.

10.
Genes Dev ; 31(9): 939-952, 2017 05 01.
Article in English | MEDLINE | ID: mdl-28536148

ABSTRACT

DEAD-box RNA helicases play important roles in a wide range of metabolic processes. Regulatory proteins can stimulate or block the activity of DEAD-box helicases. Here, we show that LOTUS (Limkain, Oskar, and Tudor containing proteins 5 and 7) domains present in the germline proteins Oskar, TDRD5 (Tudor domain-containing 5), and TDRD7 bind and stimulate the germline-specific DEAD-box RNA helicase Vasa. Our crystal structure of the LOTUS domain of Oskar in complex with the C-terminal RecA-like domain of Vasa reveals that the LOTUS domain occupies a surface on a DEAD-box helicase not implicated previously in the regulation of the enzyme's activity. We show that, in vivo, the localization of Drosophila Vasa to the nuage and germ plasm depends on its interaction with LOTUS domain proteins. The binding and stimulation of Vasa DEAD-box helicases by LOTUS domains are widely conserved.


Subject(s)
DEAD-box RNA Helicases/metabolism , Drosophila Proteins/metabolism , Drosophila/metabolism , Germ Cells/metabolism , Animals , Animals, Genetically Modified/genetics , Animals, Genetically Modified/growth & development , Animals, Genetically Modified/metabolism , Cells, Cultured , DEAD-box RNA Helicases/chemistry , DEAD-box RNA Helicases/genetics , Drosophila/genetics , Drosophila/growth & development , Drosophila Proteins/chemistry , Drosophila Proteins/genetics , Female , Gene Expression Regulation, Enzymologic , Protein Conformation , Protein Domains
11.
J Am Chem Soc ; 146(17): 11887-11896, 2024 May 01.
Article in English | MEDLINE | ID: mdl-38529556

ABSTRACT

Monitoring the spontaneous reconstruction of the surface of metal oxides under electrocatalytic reaction conditions is critical to identifying the active sites and establishing structure-activity relationships. Here, we report on a self-terminated surface reconstruction of Ruddlesden-Popper lanthanum nickel oxide (La2NiO4+δ) that occurs spontaneously during reaction with alkaline electrolyte species. Using a combination of high-resolution scanning transmission electron microscopy (HR-STEM), surface-sensitive X-ray photoelectron spectroscopy (XPS), and soft X-ray absorption spectroscopy (sXAS), as well as electrochemical techniques, we identify the structure of the reconstructed surface layer as an amorphous (oxy)hydroxide phase that features abundant under-coordinated nickel sites. No further amorphization of the crystalline oxide lattice (beyond the ∼2 nm thick layer formed) was observed during oxygen evolution reaction (OER) cycling experiments. Notably, the formation of the reconstructed surface layer increases the material's oxygen evolution reaction (OER) activity by a factor of 45 when compared to that of the pristine crystalline surface. In contrast, a related perovskite phase, i.e., LaNiO3, did not show noticeable surface reconstruction, and also no increase in its OER activity was observed. This work provides detailed insight into a surface reconstruction behavior dictated by the crystal structure of the parent oxide and highlights the importance of surface dynamics under reaction conditions.

12.
PLoS Pathog ; 18(12): e1011066, 2022 12.
Article in English | MEDLINE | ID: mdl-36574449

ABSTRACT

Invasive aspergillosis remains one of the most devastating fungal diseases and is predominantly linked to infections caused by the opportunistic human mold pathogen Aspergillus fumigatus. Major treatment regimens for the disease comprise the administration of antifungals belonging to the azole, polyene and echinocandin drug class. The prodrug 5-fluorocytosine (5FC), which is the only representative of a fourth class, the nucleobase analogs, shows unsatisfactory in vitro activities and is barely used for the treatment of aspergillosis. The main route of 5FC activation in A. fumigatus comprises its deamination into 5-fluorouracil (5FU) by FcyA, which is followed by Uprt-mediated 5FU phosphoribosylation into 5-fluorouridine monophosphate (5FUMP). In this study, we characterized and examined the role of a metabolic bypass that generates this nucleotide via 5-fluorouridine (5FUR) through uridine phosphorylase and uridine kinase activities. Resistance profiling of mutants lacking distinct pyrimidine salvage activities suggested a minor contribution of the alternative route in 5FUMP formation. We further analyzed the contribution of drug efflux in 5FC tolerance and found that A. fumigatus cells exposed to 5FC reduce intracellular fluoropyrimidine levels through their export into the environment. This release, which was particularly high in mutants lacking Uprt, generates a toxic environment for cytosine deaminase lacking mutants as well as mammalian cells. Employing the broad-spectrum fungal efflux pump inhibitor clorgyline, we demonstrate synergistic properties of this compound in combination with 5FC, 5FU as well as 5FUR.


Subject(s)
Antineoplastic Agents , Aspergillosis , Animals , Humans , Flucytosine/pharmacology , Flucytosine/metabolism , Flucytosine/therapeutic use , Antifungal Agents/pharmacology , Antifungal Agents/therapeutic use , Antineoplastic Agents/pharmacology , Antimetabolites , Fluorouracil/pharmacology , Aspergillosis/drug therapy , Aspergillus fumigatus/metabolism , Drug Resistance, Fungal , Mammals
13.
Clin Exp Allergy ; 54(3): 195-206, 2024 03.
Article in English | MEDLINE | ID: mdl-38234127

ABSTRACT

BACKGROUND: IgE antibodies to cross-reactive carbohydrate determinants (CCD) are usually clinically irrelevant but they can be a cause of false positive outcomes of allergen-specific IgE tests in vitro. Their prevalence and levels have been so far cross-sectionally examined among adult allergic patients and much less is known about their origins and relevance in childhood. METHODS: We examined CCD with a cross-sectional approach in 1263 Italian pollen allergic children (Panallergen in Paediatrics, PAN-PED), as well as with a longitudinal approach in 612 German children (Multicenter Allergy Study, MAS), whose cutaneous and IgE sensitization profile to a broad panel of allergen extracts and molecules was already known. The presence and levels of IgE to CCD were examined in the sera of both cohorts using bromelain (MUXF3) as reagent and a novel chemiluminescence detection system, operating in a solid phase of fluorescently labelled and streptavidin-coated paramagnetic microparticles (NOVEOS, HYCOR, USA). RESULTS: IgE to CCD was found in 22% of the Italian pollen allergic children, mainly in association with an IgE response to grass pollen. Children with IgE to CCD had higher total IgE levels and were sensitized to more allergenic molecules of Phleum pratense than those with no IgE to CCD. Among participants of the German MAS birth cohort study, IgE to CCD emerged early in life (even at pre-school age), with IgE sensitization to group 1 and 4 allergen molecules of grasses, and almost invariably persisted over the full observation period. CONCLUSIONS: Our results contribute to dissect the immunological origins, onset, evolution and risk factors of CCD-sIgE response in childhood, and raise the hypothesis that group 1 and/or 4 allergen molecules of grass pollen are major inducers of these antibodies through an antigen-specific, T-B cell cognate interaction.


Subject(s)
Hypersensitivity , Immunoglobulin E , Adult , Humans , Child , Child, Preschool , Cohort Studies , Prevalence , Allergens , Carbohydrates , Risk Factors , Cross Reactions
14.
Plant Cell Environ ; 2024 Oct 17.
Article in English | MEDLINE | ID: mdl-39420635

ABSTRACT

The application of microbial inoculants holds promise for the sustainable restoration of abandoned mine sites by affecting soil nutrients and microbial communities. However, the responses of plant microbial communities to microbial inoculants in mine restoration remain largely unknown. To bridge this knowledge gap, we conducted a 4-year field experiment at an abandoned carbonate mine site to assess the impacts of microbial inoculants on the soil-plant microbiome. Our findings revealed that microbial inoculants significantly changed roots, fine root bacterial and fungal communities. Further, no significant correlations were observed between the soil-plant nutrient content (Z-score) and microbial alpha diversity. However, a significantly positive correlation was found between the relative abundance of the keystone ecological cluster (Module #1) and soil-plant nutrient content. The application of microbial inoculants also increased complexity, albeit decreased stability of plant microbiome networks, alongside a reduction in stochastic assembly. Conversely, they decreased the complexity but increased the stability of soil microbiome networks, accompanied by an increase in stochastic assembly. Notably, the number of specifically enriched microbiome functional traits of roots and root nodules under the microbial inoculant treatments surpassed that of the control. In summary, our findings underscored the potential of microbial inoculants to enhance soil-plant functionality at abandoned mine restoration sites.

15.
J Card Fail ; 30(10): 1222-1230, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39389730

ABSTRACT

BACKGROUND: Percutaneous coronary intervention (PCI) might improve outcome at severe stages of cardiac allograft vasculopathy (CAV) among patients after heart transplantation (HTx). Yet, risk stratification of HTx patients after PCI remains challenging. AIMS: To assess whether the International Society for Heart and Lung Transplantation (ISHLT) CAV classification remains prognostic after PCI and whether risk-stratification models of non-transplanted patients extend to HTx patients with CAV. METHODS: At 2 European academic centers, 203 patients were stratified in cohort 1 (ISHLT CAV1, without PCI, n = 126) or cohort 2 (ISHLT CAV2 and 3, with PCI). At first diagnosis of CAV or first PCI, respectively, ISHLT CAV grades, SYNTAX scores I and II (SXS-I, SXS-II) were used to quantify baseline and residual CAV (rISHLT, rSXS-I, rSXS-II). RSXS-I > 0 defined incomplete revascularization (IR). RESULTS: SXS-II predicted mortality in cohort 1 (P = 0.004), whereas SXS-I (P = 0.009) and SXS-II (P = 0.002) predicted mortality in cohort 2. Post-PCI, IR (P = 0.004), high rISHLT (P = 0.02) and highest tertile of rSXS-II (P = 0.006) were associated with higher 5-year mortality. In bivariable Cox analysis, baseline SXS-II, IR and rSXS-II remained predictors of 5-year mortality post-PCI. There was a strong inverse relationship between baseline and rSXS-I (r = -0.55; P < 0.001 and r = -0.50; P = 0.003, respectively) regarding the interval to first reintervention. CONCLUSION: People with ISHLT CAV classification could apply for risk stratification after PCI. SYNTAX scores could be complemental for risk stratification and individualization of invasive follow-up of HTx patients with CAV.


Subject(s)
Allografts , Heart Transplantation , Percutaneous Coronary Intervention , Humans , Heart Transplantation/adverse effects , Male , Female , Middle Aged , Percutaneous Coronary Intervention/methods , Percutaneous Coronary Intervention/adverse effects , Retrospective Studies , Treatment Outcome , Coronary Artery Disease/surgery , Adult , Follow-Up Studies , Cohort Studies , Postoperative Complications/epidemiology , Postoperative Complications/diagnosis , Risk Assessment/methods , Aged
16.
Glob Chang Biol ; 30(4): e17290, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38651789

ABSTRACT

Soil organic nitrogen (N) mineralization not only supports ecosystem productivity but also weakens carbon and N accumulation in soils. Recalcitrant (mainly mineral-associated organic matter) and labile (mainly particulate organic matter) organic materials differ dramatically in nature. Yet, the patterns and drivers of recalcitrant (MNrec) and labile (MNlab) organic N mineralization rates and their consequences on ecosystem N retention are still unclear. By collecting MNrec (299 observations) and MNlab (299 observations) from 57 15N tracing studies, we found that soil pH and total N were the master factors controlling MNrec and MNlab, respectively. This was consistent with the significantly higher rates of MNrec in alkaline soils and of MNlab in natural ecosystems. Interestingly, our analysis revealed that MNrec directly stimulated microbial N immobilization and plant N uptake, while MNlab stimulated the soil gross autotrophic nitrification which discouraged ammonium immobilization and accelerated nitrate production. We also noted that MNrec was more efficient at lower precipitation and higher temperatures due to increased soil pH. In contrast, MNlab was more efficient at higher precipitation and lower temperatures due to increased soil total N. Overall, we suggest that increasing MNrec may lead to a conservative N cycle, improving the ecosystem services and functions, while increasing MNlab may stimulate the potential risk of soil N loss.


Subject(s)
Nitrogen , Soil Microbiology , Soil , Soil/chemistry , Nitrogen/metabolism , Plants/metabolism , Hydrogen-Ion Concentration , Nitrification , Nitrogen Cycle
17.
Glob Chang Biol ; 30(1): e17003, 2024 Jan.
Article in English | MEDLINE | ID: mdl-37943245

ABSTRACT

Identifying tipping points in the relationship between aridity and gross nitrogen (N) cycling rates could show critical vulnerabilities of terrestrial ecosystems to climate change. Yet, the global pattern of gross N cycling response to aridity across terrestrial ecosystems remains unknown. Here, we collected 14,144 observations from 451 15 N-labeled studies and used segmented regression to identify the global threshold responses of soil gross N cycling rates and soil process-related variables to aridity index (AI), which decreases as aridity increases. We found on a global scale that increasing aridity reduced soil gross nitrate consumption but increased soil nitrification capacity, mainly due to reduced soil microbial biomass carbon (MBC) and N (MBN) and increased soil pH. Threshold response of gross N production and retention to aridity was observed across terrestrial ecosystems. In croplands, gross nitrification and extractable nitrate were inhibited with increasing aridity below the threshold AI ~0.8-0.9 due to inhibited ammonia-oxidizing archaea and bacteria, while the opposite was favored above this threshold. In grasslands, gross N mineralization and immobilization decreased with increasing aridity below the threshold AI ~0.5 due to decreased MBN, but the opposite was true above this threshold. In forests, increased aridity stimulated nitrate immobilization below the threshold AI ~1.0 due to increased soil C/N ratio, but inhibited ammonium immobilization above the threshold AI ~1.3 due to decreased soil total N and increased MBC/MBN ratio. Soil dissimilatory nitrate reduction to ammonium decreased with increasing aridity globally and in forests when the threshold AI ~1.4 was passed. Overall, we suggest that any projected increase in aridity in response to climate change is likely to reduce plant N availability in arid regions while enhancing it in humid regions, affecting the provision of ecosystem services and functions.


Subject(s)
Ammonium Compounds , Ecosystem , Soil , Nitrates , Nitrogen/analysis , Soil Microbiology
18.
Glob Chang Biol ; 30(10): e17537, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39425618

ABSTRACT

Anthropogenic land-use practices influence ecosystem functions and the environment. Yet, the effect of global land-use change on ecosystem nitrogen (N) cycling remains unquantified despite that ecosystem N cycling plays a critical role in maintaining food security. Here, we analysed 2430 paired observations globally to show that converting natural to managed ecosystems increases ratios of autotrophic nitrification to ammonium immobilisation and nitrate to ammonium, but decreases soil immobilisation of mineral N, causing increased N losses via leaching and gaseous N emissions, such as nitrous oxide (e.g., via denitrification), resulting in a leaky N cycle. Changing land use from intensively managed to one that resembles natural ecosystems reversed N losses by 108% on average, resulting in a more conservative N cycle. Structural equation modelling revealed that changes in soil organic carbon, pH and carbon to N ratio were more important than changes in soil moisture content and temperature in predicting ecosystem N retention capacities following land-use conversion and its reversion. The hotspots of leaky N cycles were mostly in equatorial and tropical regions, as well as in Western Europe, the United States and China. Our results suggest that whether an ecosystem exhibits a conservative N cycle after land-use reversion depends on management practices.


Subject(s)
Ecosystem , Nitrogen Cycle , Soil , Soil/chemistry , Agriculture/methods , Nitrogen/metabolism , Nitrogen/analysis , Models, Theoretical , Denitrification
19.
Chemphyschem ; 25(17): e202400270, 2024 Sep 02.
Article in English | MEDLINE | ID: mdl-38837531

ABSTRACT

NMR spectroscopy studies using parahydrogen-induced polarization have previously established the existence of the pairwise hydrogen addition route in the hydrogenation of unsaturated hydrocarbons over heterogeneous catalysts, including those based on rhodium (Rh0). This pathway requires the incorporation of both hydrogen atoms from one hydrogen molecule to the same product molecule. However, the underlying mechanism for such pairwise hydrogen addition must be better understood. The involvement of carbon, either in the form of carbonaceous deposits on the surface of a catalyst or as a metal carbide phase, is known to modify catalytic properties significantly and thus could also affect the pairwise hydrogen addition route. Here, we explored carbon's role by studying the hydrogenation of propene and propyne with parahydrogen on a Rh2C catalyst and comparing the results with those for a Rh0/C catalyst obtained from Rh2C via H2 pretreatment. While the catalysts Rh2C and Rh0/C differ notably in the rate of conversion of parahydrogen to normal hydrogen as well as in terms of hydrogenation activity, our findings suggest that the carbide phase does not play a significant role in the pairwise H2 addition route on rhodium catalysts.

20.
BJU Int ; 133(6): 680-689, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38469686

ABSTRACT

BACKGROUND: Older men (aged ≥75 years) with high risk, non-metastatic prostate cancer (PCa) are increasingly treated with curative therapy (surgery or radiotherapy). However, it is unclear if curative therapy prolongs life and improves health-related quality of life (HRQoL) in this age group compared to conservative therapy, which has evolved considerably during the last decade. STUDY DESIGN: The Scandinavian Prostate Cancer Group (SPCG) 19/Norwegian Get-Randomized Research Group-Prostate (GRand-P) is a randomised, two-armed, controlled, multicentre, phase III trial carried out at study centres in Norway, Denmark, Finland, and Sweden. ENDPOINTS: The primary endpoints are overall survival and HRQoL (burden of disease scale, European Organisation for the Research and Treatment of Cancer [EORTC] Elderly Cancer patients). Secondary endpoints are PCa-specific survival, metastasis-free survival, role-functioning scale (EORTC quality of life questionnaire 30-item core), urinary irritative/obstructive scale (26-item Expanded Prostate Cancer Index Composite [EPIC-26]), bowel scale (EPIC-26), intervention-free survival, PCa morbidity, use of secondary and tertiary systemic therapies, mean quality-adjusted life-years (QALYs), and mean total healthcare costs. PATIENTS AND METHODS: A total of 980 men (aged ≥75 years) with non-metastatic, high-risk PCa will initially be screened with Geriatric 8 (G8) health status screening tool and Mini-COG© brief cognitive test. Participants identified by G8 as 'fit' or 'frail' will be randomised (ratio 1:1) to either immediate curative therapy (radiotherapy or prostatectomy) or conservative therapy (endocrine therapy or observation). Participants who are unable or unwilling to participate in randomisation will be enrolled in a separate observation group. Randomised patients will be followed for 10 years. TRIAL REGISTRATION: Ethics approval has been granted in Norway (457593), Denmark (H-22051998), Finland (R23043) and Sweden (Dnr 2023-05296-01). The trial is registered on Clinicaltrials.org (NCT05448547).


Subject(s)
Conservative Treatment , Prostatic Neoplasms , Quality of Life , Aged , Aged, 80 and over , Humans , Male , Clinical Trials, Phase III as Topic , Prostatectomy , Prostatic Neoplasms/therapy , Prostatic Neoplasms/pathology , Randomized Controlled Trials as Topic , Multicenter Studies as Topic
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