RESUMEN
Trace amine-associated receptor 1 (TAAR1) senses a spectrum of endogenous amine-containing metabolites (EAMs) to mediate diverse psychological functions and is useful for schizophrenia treatment without the side effects of catalepsy. Here, we systematically profiled the signaling properties of TAAR1 activation and present nine structures of TAAR1-Gs/Gq in complex with EAMs, clinical drugs, and synthetic compounds. These structures not only revealed the primary amine recognition pocket (PARP) harboring the conserved acidic D3.32 for conserved amine recognition and "twin" toggle switch for receptor activation but also elucidated that targeting specific residues in the second binding pocket (SBP) allowed modulation of signaling preference. In addition to traditional drug-induced Gs signaling, Gq activation by EAM or synthetic compounds is beneficial to schizophrenia treatment. Our results provided a structural and signaling framework for molecular recognition by TAAR1, which afforded structural templates and signal clues for TAAR1-targeted candidate compounds design.
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Receptores Acoplados a Proteínas G , Transducción de Señal , Humanos , Aminas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Esquizofrenia/metabolismoRESUMEN
Trace-amine-associated receptors (TAARs), a group of biogenic amine receptors, have essential roles in neurological and metabolic homeostasis1. They recognize diverse endogenous trace amines and subsequently activate a range of G-protein-subtype signalling pathways2,3. Notably, TAAR1 has emerged as a promising therapeutic target for treating psychiatric disorders4,5. However, the molecular mechanisms underlying its ability to recognize different ligands remain largely unclear. Here we present nine cryo-electron microscopy structures, with eight showing human and mouse TAAR1 in a complex with an array of ligands, including the endogenous 3-iodothyronamine, two antipsychotic agents, the psychoactive drug amphetamine and two identified catecholamine agonists, and one showing 5-HT1AR in a complex with an antipsychotic agent. These structures reveal a rigid consensus binding motif in TAAR1 that binds to endogenous trace amine stimuli and two extended binding pockets that accommodate diverse chemotypes. Combined with mutational analysis, functional assays and molecular dynamic simulations, we elucidate the structural basis of drug polypharmacology and identify the species-specific differences between human and mouse TAAR1. Our study provides insights into the mechanism of ligand recognition and G-protein selectivity by TAAR1, which may help in the discovery of ligands or therapeutic strategies for neurological and metabolic disorders.
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Proteínas de Unión al GTP , Receptores Acoplados a Proteínas G , Animales , Humanos , Ratones , Aminas/metabolismo , Anfetamina/metabolismo , Antipsicóticos/química , Antipsicóticos/metabolismo , Sitios de Unión , Catecolaminas/agonistas , Catecolaminas/química , Catecolaminas/metabolismo , Microscopía por Crioelectrón , Proteínas de Unión al GTP/química , Proteínas de Unión al GTP/metabolismo , Proteínas de Unión al GTP/ultraestructura , Ligandos , Simulación de Dinámica Molecular , Mutación , Polifarmacología , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/metabolismo , Receptores Acoplados a Proteínas G/ultraestructura , Especificidad de la Especie , Especificidad por SustratoRESUMEN
Odorants are detected as smell in the nasal epithelium of mammals by two G-protein-coupled receptor families, the odorant receptors and the trace amine-associated receptors1,2 (TAARs). TAARs emerged following the divergence of jawed and jawless fish, and comprise a large monophyletic family of receptors that recognize volatile amine odorants to elicit both intraspecific and interspecific innate behaviours such as attraction and aversion3-5. Here we report cryo-electron microscopy structures of mouse TAAR9 (mTAAR9) and mTAAR9-Gs or mTAAR9-Golf trimers in complex with ß-phenylethylamine, N,N-dimethylcyclohexylamine or spermidine. The mTAAR9 structures contain a deep and tight ligand-binding pocket decorated with a conserved D3.32W6.48Y7.43 motif, which is essential for amine odorant recognition. In the mTAAR9 structure, a unique disulfide bond connecting the N terminus to ECL2 is required for agonist-induced receptor activation. We identify key structural motifs of TAAR family members for detecting monoamines and polyamines and the shared sequence of different TAAR members that are responsible for recognition of the same odour chemical. We elucidate the molecular basis of mTAAR9 coupling to Gs and Golf by structural characterization and mutational analysis. Collectively, our results provide a structural basis for odorant detection, receptor activation and Golf coupling of an amine olfactory receptor.
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Aminas Biogénicas , Odorantes , Percepción Olfatoria , Poliaminas , Receptores Odorantes , Animales , Ratones , Aminas Biogénicas/análisis , Aminas Biogénicas/química , Aminas Biogénicas/metabolismo , Microscopía por Crioelectrón , Subunidades alfa de la Proteína de Unión al GTP Gs/química , Subunidades alfa de la Proteína de Unión al GTP Gs/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gs/ultraestructura , Odorantes/análisis , Percepción Olfatoria/fisiología , Poliaminas/análisis , Poliaminas/química , Poliaminas/metabolismo , Receptores de Amina Biogénica/química , Receptores de Amina Biogénica/genética , Receptores de Amina Biogénica/metabolismo , Receptores de Amina Biogénica/ultraestructura , Receptores Odorantes/química , Receptores Odorantes/genética , Receptores Odorantes/metabolismo , Receptores Odorantes/ultraestructura , Olfato/fisiología , Espermidina/análisis , Espermidina/química , Espermidina/metabolismoRESUMEN
In the clades of animals that diverged from the bony fish, a group of Mas-related G-protein-coupled receptors (MRGPRs) evolved that have an active role in itch and allergic signals1,2. As an MRGPR, MRGPRX2 is known to sense basic secretagogues (agents that promote secretion) and is involved in itch signals and eliciting pseudoallergic reactions3-6. MRGPRX2 has been targeted by drug development efforts to prevent the side effects induced by certain drugs or to treat allergic diseases. Here we report a set of cryo-electron microscopy structures of the MRGPRX2-Gi1 trimer in complex with polycationic compound 48/80 or with inflammatory peptides. The structures of the MRGPRX2-Gi1 complex exhibited shallow, solvent-exposed ligand-binding pockets. We identified key common structural features of MRGPRX2 and describe a consensus motif for peptidic allergens. Beneath the ligand-binding pocket, the unusual kink formation at transmembrane domain 6 (TM6) and the replacement of the general toggle switch from Trp6.48 to Gly6.48 (superscript annotations as per Ballesteros-Weinstein nomenclature) suggest a distinct activation process. We characterized the interfaces of MRGPRX2 and the Gi trimer, and mapped the residues associated with key single-nucleotide polymorphisms on both the ligand and G-protein interfaces of MRGPRX2. Collectively, our results provide a structural basis for the sensing of cationic allergens by MRGPRX2, potentially facilitating the rational design of therapies to prevent unwanted pseudoallergic reactions.
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Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/metabolismo , Prurito/metabolismo , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Neuropéptido/química , Receptores de Neuropéptido/metabolismo , Alérgenos/inmunología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Sitios de Unión , Secuencia de Consenso , Microscopía por Crioelectrón , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gq-G11/metabolismo , Humanos , Modelos Moleculares , Proteínas del Tejido Nervioso/inmunología , Proteínas del Tejido Nervioso/ultraestructura , Receptores Acoplados a Proteínas G/inmunología , Receptores Acoplados a Proteínas G/ultraestructura , Receptores de Neuropéptido/inmunología , Receptores de Neuropéptido/ultraestructuraRESUMEN
The G-protein-coupled bile acid receptor (GPBAR) conveys the cross-membrane signalling of a vast variety of bile acids and is a signalling hub in the liver-bile acid-microbiota-metabolism axis1-3. Here we report the cryo-electron microscopy structures of GPBAR-Gs complexes stabilized by either the high-affinity P3954 or the semisynthesized bile acid derivative INT-7771,3 at 3 Å resolution. These structures revealed a large oval pocket that contains several polar groups positioned to accommodate the amphipathic cholic core of bile acids, a fingerprint of key residues to recognize diverse bile acids in the orthosteric site, a putative second bile acid-binding site with allosteric properties and structural features that contribute to bias properties. Moreover, GPBAR undertakes an atypical mode of activation and G protein coupling that features a different set of key residues connecting the ligand-binding pocket to the Gs-coupling site, and a specific interaction motif that is localized in intracellular loop 3. Overall, our study not only reveals unique structural features of GPBAR that are involved in bile acid recognition and allosteric effects, but also suggests the presence of distinct connecting mechanisms between the ligand-binding pocket and the G-protein-binding site in the G-protein-coupled receptor superfamily.
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Ácidos y Sales Biliares/metabolismo , Microscopía por Crioelectrón , Receptores Acoplados a Proteínas G/metabolismo , Receptores Acoplados a Proteínas G/ultraestructura , Regulación Alostérica/efectos de los fármacos , Ácidos y Sales Biliares/química , Sitios de Unión/efectos de los fármacos , Ácidos Cólicos/química , Ácidos Cólicos/farmacología , Subunidades alfa de la Proteína de Unión al GTP Gs/química , Subunidades alfa de la Proteína de Unión al GTP Gs/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gs/ultraestructura , Humanos , Ligandos , Modelos Moleculares , Unión Proteica , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/química , Especificidad por SustratoRESUMEN
The G protein-coupled bile acid receptor (GPBAR) is the membrane receptor for bile acids and a driving force of the liver-bile acid-microbiota-organ axis to regulate metabolism and other pathophysiological processes. Although GPBAR is an important therapeutic target for a spectrum of metabolic and neurodegenerative diseases, its activation has also been found to be linked to carcinogenesis, leading to potential side effects. Here, via functional screening, we found that two specific GPBAR agonists, R399 and INT-777, demonstrated strikingly different regulatory effects on the growth and apoptosis of non-small cell lung cancer (NSCLC) cells both in vitro and in vivo. Further mechanistic investigation showed that R399-induced GPBAR activation displayed an obvious bias for ß-arrestin 1 signaling, thus promoting YAP signaling activation to stimulate cell proliferation. Conversely, INT-777 preferentially activated GPBAR-Gs signaling, thus inactivating YAP to inhibit cell proliferation and induce apoptosis. Phosphorylation of GPBAR by GRK2 at S310/S321/S323/S324 sites contributed to R399-induced GPBAR-ß-arrestin 1 association. The cryoelectron microscopy (cryo-EM) structure of the R399-bound GPBAR-Gs complex enabled us to identify key interaction residues and pivotal conformational changes in GPBAR responsible for the arrestin signaling bias and cancer cell proliferation. In summary, we demonstrate that different agonists can regulate distinct functions of cell growth and apoptosis through biased GPBAR signaling and control of YAP activity in a NSCLC cell model. The delineated mechanism and structural basis may facilitate the rational design of GPBAR-targeting drugs with both metabolic and anticancer benefits.
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Carcinoma de Pulmón de Células no Pequeñas , Proteínas de Ciclo Celular , Neoplasias Pulmonares , Receptores Acoplados a Proteínas G , Factores de Transcripción , Ácidos y Sales Biliares/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/patología , Proteínas de Ciclo Celular/metabolismo , Ácidos Cólicos/farmacología , Microscopía por Crioelectrón , Humanos , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/química , Receptores Acoplados a Proteínas G/metabolismo , Factores de Transcripción/metabolismo , beta-Arrestina 1/metabolismoRESUMEN
The associations of arbuscular mycorrhizal (AM) or ectomycorrhiza (EcM) fungi with plants have sequentially evolved and significantly contributed to enhancing plant nutrition. Nonetheless, how evolutionary and ecological forces drive nutrient acquisition strategies of AM and EcM woody plants remains poorly understood. Our global analysis of woody species revealed that, over divergence time, AM woody plants evolved faster nitrogen mineralization rates without changes in nitrogen resorption. However, EcM woody plants exhibited an increase in nitrogen mineralization but a decrease in nitrogen resorption, indicating a shift towards a more inorganic nutrient economy. Despite this alteration, when evaluating present-day woody species, AM woody plants still display faster nitrogen mineralization and lower nitrogen resorption than EcM woody plants. This inorganic nutrient economy allows AM woody plants to thrive in warm environments with a faster litter decomposition rate. Our findings indicate that the global pattern of nutrient acquisition strategies in mycorrhizal plants is shaped by the interplay between phylogeny and climate.
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Micorrizas , Raíces de Plantas/microbiología , Nitrógeno , Plantas , Nutrientes , Suelo , SimbiosisRESUMEN
Increasing evidence shows the oncogenic function of FAM83D in human cancer, but how FAM83D exerts its oncogenic function remains largely unclear. Here, we investigated the importance of FAM83D/FBXW7 interaction in breast cancer (BC). We systematically mapped the FBXW7-binding sites on FAM83D through a comprehensive mutational analysis together with co-immunoprecipitation assay. Mutations at the FBXW7-binding sites on FAM83D led to that FAM83D lost its capability to promote the ubiquitination and proteasomal degradation of FBXW7; cell proliferation, migration, and invasion in vitro; and tumor growth and metastasis in vivo, indicating that the FBXW7-binding sites on FAM83D are essential for its oncogenic functions. A meta-evaluation of FAM83D revealed that the prognostic impact of FAM83D was independent on molecular subtypes. The higher expression of FAM83D has poorer prognosis. Moreover, high expression of FAM83D confers resistance to chemotherapy in BCs, which is experimentally validated in vitro. We conclude that identification of FBXW7-binding sites on FAM83D not only reveals the importance for FAM83D oncogenic function, but also provides valuable insights for drug target.
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Neoplasias de la Mama , Proteínas de Ciclo Celular , Humanos , Femenino , Proteína 7 que Contiene Repeticiones F-Box-WD/genética , Proteína 7 que Contiene Repeticiones F-Box-WD/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Línea Celular Tumoral , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Pronóstico , Proliferación Celular/genética , Regulación Neoplásica de la Expresión Génica , Proteínas Asociadas a Microtúbulos/genética , Proteínas Asociadas a Microtúbulos/metabolismoRESUMEN
Dual-mode humidity sensors have received wide attention in recent years due to their great potential in multifunction applications. Herein, following a "two birds with one stone" strategy, a dual-mode and self-powered low humidity sensor based on LiBr-MOF-801 with high response and power generation is proposed. The optimized LiBr-MOF-801-based sensor exhibits impedance-voltage dual-mode sensitivity in the low humidity range of 0-23% relative humidity (RH) with high response (57.1 and 0.61 V), small hysteresis (0.3% RH) and good long-term stability at room temperature (20 °C). Moreover, an integrated humidity power generator is obtained by series connection of the self-powered humidity sensor within 15 cm2, and the output voltage reaches 2.6 V with an output power density of 110 nW cm-2, and can be used as energy, supplying power to commercial electronic equipment even in low humidity. This work provides a new sight for fabricating high-performance, dual-mode, and self-powered low-humidity sensors.
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Increased atmospheric nitrogen (N) deposition significantly disturbs ecosystem N cycle. Although foliar interception and uptake of N deposition can provide an important alternative N supply to forest ecosystems, the mechanisms regulating foliar N uptake from wet deposition are not fully understood. Here, we selected 19 woody species with a wide range of plant traits from different functional groups and conducted a 15N isotope labelling experiment through brushing 15NH4 + and 15NO3 - solution on canopy leaves. Our findings demonstrate that leaves can directly absorb N from wet deposition within a few hours. The average leaf 15N recoveries were 10% and 28% under 15NH4 + and 15NO3 - treatments across species, respectively, while twig N recoveries were only 1%-7% of leaf N recoveries. Differences in foliar N uptake efficiency among species were closely associated with leaf traits but were little influenced by meteorological conditions or soil nutrient status. Specifically, plants with higher leaf N concentration, larger specific leaf area and lower wax concentration exhibited higher leaf N recovery. Our results indicated that tree canopies could directly absorb N from atmospheric deposition. We highlight the critical role of leaf traits in determining canopy foliar N uptake, which may consequently influence plant competition under elevated N deposition.
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Obesity is a major cause of nonalcohol fatty liver disease (NAFLD), which is characterized by hepatic fibrosis, lipotoxicity, inflammation, and apoptosis. Previous studies have shown that an imbalance in the autonomic nervous system is closely related to the pathogenesis of NAFLD. In this study, we investigated the effects of pyridostigmine (PYR), a cholinesterase (AChE) inhibitor, on HFD-induced liver injury and explored the potential mechanisms involving mitochondrial damage and oxidative stress. A murine model of HFD-induced obesity was established using the C57BL/6 mice, and PYR (3 mg/kg/d) or placebo was administered for 20 weeks. PYR reduced the body weight and liver weight of the HFD-fed mice. Additionally, the serum levels of IL-6, TNF-α, cholesterol, and triglyceride were significantly lower in the PYR-treated versus the untreated mice, corresponding to a decrease in hepatic fibrosis, lipid accumulation, and apoptosis in the former. Furthermore, the mitochondrial morphology improved significantly in the PYR-treated group. Consistently, PYR upregulated ATP production and the mRNA level of the mitochondrial dynamic factors OPA1, Drp1 and Fis1, and the mitochondrial unfolded protein response (UPRmt) factors LONP1 and HSP60. Moreover, PYR treatment activated the Keap1/Nrf2 pathway and upregulated HO-1 and NQO-1, which mitigated oxidative injury as indicated by decreased 8-OHDG, MDA and H2 O2 levels, and increased SOD activity. Finally, PYR elevated acetylcholine (ACh) levels by inhibiting AChE, and upregulated the α7nAChR and M3AChR proteins in the HFD-fed mice. PYR alleviated obesity-induced hepatic injury in mice by mitigating mitochondrial damage and oxidative stress via α7nAChR and M3AChR.
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Enfermedad Hepática Crónica Inducida por Sustancias y Drogas , Enfermedad del Hígado Graso no Alcohólico , Ratones , Animales , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Enfermedad del Hígado Graso no Alcohólico/etiología , Enfermedad del Hígado Graso no Alcohólico/metabolismo , Bromuro de Piridostigmina/farmacología , Receptor Nicotínico de Acetilcolina alfa 7/metabolismo , Proteína 1 Asociada A ECH Tipo Kelch/metabolismo , Enfermedad Hepática Crónica Inducida por Sustancias y Drogas/complicaciones , Enfermedad Hepática Crónica Inducida por Sustancias y Drogas/metabolismo , Ratones Endogámicos C57BL , Factor 2 Relacionado con NF-E2/metabolismo , Hígado/metabolismo , Estrés Oxidativo , Cirrosis Hepática/metabolismo , Obesidad/tratamiento farmacológico , Obesidad/metabolismo , Dieta , Dieta Alta en Grasa/efectos adversosRESUMEN
BACKGROUND: Postoperative sore throat (POST) is a common postoperative complication. COMPLICATION: Chewing gum can inhibit the growth of oral bacteria, cleanse, and lubricate the oral cavity, which can help reduce postoperative sore throat. We hypothesize that chewing gum before surgery could relieve POST. METHODS: Patients planned to undergo total thyroidectomy under general anesthesia with tracheal intubation were randomized to swallow saliva twice or chew 1.4 g/2.8 g of gum for 2 minutes before surgery. A standard anesthesia protocol was performed. The numerical rating scale scores of POST at 1, 24, and 48 h after surgery were collected. The primary outcome was the incidence of moderate/severe POST (numerical rating scale score >3) within 48 h. RESULTS: Data from 148 patients (control group, n = 50; 1.4 g group, n = 48; and 2.8 g group, n = 50) were included in the analysis. Within 48 h, there was a significant difference among the three groups in the incidence of moderate/severe POST (control group: 74% vs. 1.4 g group: 65% vs. 2.8 g group: 50%. P = 0.04). The 2.8 g group had less incidence of moderate/severe POST than the control group (Odds Ratio = 0.351 95% Confidence Interval: (0.152 and 0.814) P = 0.02). CONCLUSION: Chewing 2.8 g gum before total thyroidectomy can reduce the incidence of moderate/severe POST within 48 h after surgery.
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Goma de Mascar , Faringitis , Humanos , Tiroidectomía/efectos adversos , Faringitis/etiología , Faringitis/prevención & control , Faringitis/epidemiología , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/prevención & control , Anestesia General , Intubación Intratraqueal/efectos adversosRESUMEN
The preparation of polyolefins with high polar monomer contents (above 20 mol %) has long been a challenge. Half-titanocenes (Cp')[HC(Ar)N]2BOTiCl2 bearing bulky electron-donating N-heterocyclic boryloxy ligands have been designed and synthesized. The complexes (Cp*)[HC(Ar)N]2BOTiCl2 (2, Ar = 2,6-iPr2C6H3; 5, Ar = 2,4,6-Me3C6H2) supported by Cp* and the bulky boryloxy ligands have been shown to efficiently catalyze the copolymerization of ethylene with long chain α-olefins. In particular, precatalyst 5 enabled the controlled synthesis of poly(ethylene-co-9-decen-1-ol) with unprecedented high polar monomer contents up to 32.1 mol% while maintaining high catalytic activity. The structural analysis and DFT calculations disclosed that the bulky and strong electron-donating boryloxy ligands could effectively stabilize cationic active species. The mechanical studies on the hydroxyl-functionalized copolymers disclosed that they exhibited high strength and toughness because of the existence of hydrogen bonds in the polymer network.
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The synthesis, structures, and reactivity of the first unsaturated AlSi2 three-membered ring systems were described. Reactions of dilithiodisilene [(NHB)LiSiâSiLi(NHB)] (1, NHB = diazaborolyl) with aluminum halides AlCl3, Ar(SiMe3)NAlCl2 (Ar = 2,6-iPr2C6H3), Cp*AlBr2 (Cp* = C5Me5), and TipAlBr2·Et2O (Tip = 2,4,6-iPr3C6H2) led to the formation of AlSi2 three-membered ring species, solvated (NHBSi)2AlCl(OEt2) (2) and solvent-free (NHBSi)2AlN(SiMe3) Ar (3), (NHBSi)2AlCp* (4), and (NHBSi)2AlTip (5), in good yields. X-ray diffraction studies and DFT calculations disclosed delocalized AlSi2 2π electron systems. Methanolysis of 4a resulted in cleavage of the Al-Si σ and Si-Si π bonds, giving trihydrodisilane (NHB)H(MeO)SiSiH2 (NHB) (6). Reaction of 4b with 4 equiv of N2O and H2CâCH2 resulted in the insertion of four oxygen atoms and four H2CâCH2 π bonds into all of the Al-Si and Si-Si bonds, yielding the O- and CH2CH2-bridged polycyclic species 7 and 8, demonstrating the synergistic reactivity of the Al-Si and Si-Si bonds in the AlSi2 ring system.
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Understanding how plants adapt to spatially heterogeneous phosphorus (P) supply is important to elucidate the effect of environmental changes on ecosystem productivity. Plant P supply is concurrently controlled by plant internal conservation and external acquisition. However, it is unclear how climate, soil, and microbes influence the contributions and interactions of the internal and external pathways for plant P supply. Here, we measured P and nitrogen (N) resorption efficiency, litter and soil acid phosphatase (AP) catalytic parameters (Vmax(s) and Km ), and soil physicochemical properties at four sites spanning from cold temperate to tropical forests. We found that the relative P limitation to plants was generally higher in tropical forests than temperate forests, but varied greatly among species and within sites. In P-impoverished habitats, plants resorbed more P than N during litterfall to maintain their N : P stoichiometric balance. In addition, once ecosystems shifted from N-limited to P-limited, litter- and soil-specific AP catalytic efficiency (Vmax(s) /Km ) increased rapidly, thereby enhancing organic P mineralization. Our findings suggested that ecosystems develop a coupled aboveground-belowground strategy to maintain P supply and N : P stoichiometric balance under P-limitation. We also highlighted that N cycle moderates P cycles and together shape plant P acquisition in forest ecosystems.
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Ecosistema , Fósforo , Fósforo/metabolismo , Monoéster Fosfórico Hidrolasas/metabolismo , Bosques , Plantas/metabolismo , Suelo/química , Fosfatasa Ácida/metabolismo , Nitrógeno/metabolismo , Hojas de la Planta/metabolismoRESUMEN
The effects and mechanisms of zinc oxide nanoparticles (ZnO NPs) and their aging products, sulfidized (s-) ZnO NPs, on the carbon cycling in the legume rhizosphere are still unclear. We observed that, after 30 days of cultivation, in the rhizosphere soil of Medicago truncatula, under ZnO NP and s-ZnO NP treatments, the dissolved organic carbon (DOC) concentrations were significantly increased by 1.8- to 2.4-fold compared to Zn2+ treatments, although the soil organic matter (SOM) contents did not change significantly. Compared to Zn2+ additions, the additions of NPs significantly induced the production of root metabolites such as carboxylic acids and amino acids and also stimulated the growth of microbes involved in the degradations of plant-derived and recalcitrant SOM, such as bacteria genera RB41 and Bryobacter, and fungi genus Conocybe. The bacterial co-occurrence networks indicated that microbes associated with SOM formation and decomposition were significantly increased under NP treatments. The adsorption of NPs by roots, the generation of root metabolites (e.g., carboxylic acid and amino acid), and enrichment of key taxa (e.g., RB41 and Gaiella) were the major mechanisms by which ZnO NPs and s-ZnO NPs drove DOC release and SOM decomposition in the rhizosphere. These results provide new perspectives on the effect of ZnO NPs on agroecosystem functions in soil-plant systems.
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Fabaceae , Nanopartículas , Contaminantes del Suelo , Óxido de Zinc , Fabaceae/metabolismo , Rizosfera , Nanopartículas/química , Plantas/metabolismo , Bacterias/metabolismo , Suelo/químicaRESUMEN
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is known to be a tobacco-specific N-nitrosamine and has peripheral carcinogenic properties. It can also induce oxidative stress, glial cell activation, and neuronal damage in the brain. However, the distribution and metabolic characteristics of NNK in the central nervous system are still unclear. Here, a sensitive and effective UHPLC-HRMS/MS method was established to identify and investigate the metabolites of NNK and their distribution in the rat brain. In addition, the pharmacokinetic profiles were simultaneously investigated via blood-brain synchronous microdialysis. NNK and its seven metabolites were well quantified in the hippocampus, cortex, striatum, olfactory bulb, brain stem, cerebellum, and other regions of rat brain after peripheral exposure (5 mg/kg, i.p.). The average content of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in all brain regions was at least threefold higher than that of NNK, indicating a rapid carbonyl reduction of NNK in the brain. Lower concentrations of pyridine N-oxidation products in the cortex, olfactory bulb, hippocampus, and striatum might be related to the poor detoxification ability in these regions. Compared to α-methyl hydroxylation, NNK and NNAL were more inclined to the α-methylene hydroxylation pathway. Synchronous pharmacokinetic results indicated that the metabolic activity of NNK in the brain was different from that in the blood. The mean α-hydroxylation ratio in the brain and blood was 0.037 and 0.161, respectively, which indicated poor metabolic activity of NNK in the central nervous system.
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Nitrosaminas , Ratas , Animales , Cromatografía Líquida de Alta Presión , Nitrosaminas/metabolismo , Carcinógenos , Encéfalo/metabolismoRESUMEN
As the most known therapeutic component of bear bile acids, ursodeoxycholic acid (UDCA) is an FDA-approved drug for the treatment of primary biliary cirrhosis (PBC), the dissolution of cholesterol gallstones. UDCA produces many beneficial effects on metabolism and immune responses via its interaction with the membrane G protein-coupled bile acid receptor (GPBAR); however, how UDCA interacts with GPBAR and its selective cellular effects remain elusive. In this study, we delineated the interaction of UDCA with GPBAR and activation mechanism of GPBAR by scattered alanine scanning and molecular docking. Our results indicated that transmembrane helix 2 (TM2), TM3, TM5 and TM6 of GPBAR contribute to the interaction of UDCA in GPBAR binding pocket. Moreover, we predicted that the engagement of the 3-OH of UDCA with phenolic oxygen of Y2406.51 in GPBAR plays a key role in GPBAR activation. Unexpectedly, in addition to the well-known roles of intracellular loop2 (ICL2) residues, we identified that ICL3 residues play an important role in G protein coupling to GPBAR in response to UDCA binding. Our study provides a preliminary molecular mechanism of how GPBAR recognizes UDCA and subsequent activation and G protein interaction, which may facilitate the development of new bile acid derivatives as therapeutics.
Asunto(s)
Ácidos y Sales Biliares , Ácido Ursodesoxicólico , Alanina , Proteínas de Unión al GTP/metabolismo , Simulación del Acoplamiento Molecular , Receptores Acoplados a Proteínas G/metabolismo , Ácido Ursodesoxicólico/uso terapéuticoRESUMEN
Seasonal differences in plant and microbial nitrogen (N) acquisition are believed to be a major mechanism that maximizes ecosystem N retention. There is also a concern that climate change may interrupt the delicate balance in N allocation between plants and microbes. Yet, convincing experimental evidence is still lacking. Using a 15 N tracer, we assessed how deepened snow affects the temporal coupling between plant and microbial N utilization in a temperate Mongolian grassland. We found that microbial 15 N recovery peaked in winter, accounting for 22% of the total ecosystem 15 N recovery, and then rapidly declined during the spring thaw. By stimulating N loss via N2 O emission and leaching, deepened snow reduced the total ecosystem 15 N recovery by 42% during the spring thaw. As the growing season progresses, the 15 N released from microbial biomass was taken up by plants, and the competitive advantage for N shifted from microbes to plants. Plant 15 N recovery reached its peak in August, accounting for 17% of the total ecosystem 15 N recovery. The Granger causality test showed that the temporal dynamics of plant 15 N recovery can be predicted by microbial 15 N recovery under ambient snow but not under deepened snow. In addition, plant 15 N recovery in August was positively correlated with and best explained by microbial 15 N recovery in March. The lower microbial 15 N recovery under deepened snow in March reduced plant 15 N recovery by 73% in August. Together, our results provide direct evidence of seasonal differences in plant and microbial N utilization that are conducive to ecosystem N retention; however, deepened snow disrupted the temporal coupling between plant-microbial N use and turnover. These findings suggest that changes in snowfall patterns may significantly alter ecosystem N cycling and N-based greenhouse gas emissions under future climate change. We highlight the importance of better representing winter processes and their response to winter climate change in biogeochemical models when assessing N cycling under global change.
Asunto(s)
Ecosistema , Nieve , Nitrógeno/análisis , Plantas , Estaciones del Año , SueloRESUMEN
Treatment noncompliance often occurs in longitudinal randomized controlled trials (RCTs) on human subjects, and can greatly complicate treatment effect assessment. The complier average causal effect (CACE) informs the intervention efficacy for the subpopulation who would comply regardless of assigned treatment and has been considered as patient-oriented treatment effects of interest in the presence of noncompliance. Real-world RCTs evaluating multifaceted interventions often employ multiple study endpoints to measure treatment success. In such trials, limited sample sizes, low compliance rates, and small to moderate effect sizes on individual endpoints can significantly reduce the power to detect CACE when these correlated endpoints are analyzed separately. To overcome the challenge, we develop a multivariate longitudinal potential outcome model with stratification on latent compliance types to efficiently assess multivariate CACEs (MCACE) by combining information across multiple endpoints and visits. Evaluation using simulation data shows a significant increase in the estimation efficiency with the MCACE model, including up to 50% reduction in standard errors (SEs) of CACE estimates and 1-fold increase in the power to detect CACE. Finally, we apply the proposed MCACE model to an RCT on Arthritis Health Journal online tool. Results show that the MCACE analysis detects significant and beneficial intervention effects on two of the six endpoints while estimating CACEs for these endpoints separately fail to detect treatment effect on any endpoint.