Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 12.438
Filtrar
1.
Nat Commun ; 11(1): 4706, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32943618

RESUMO

Yeast physiology is temporally regulated, this becomes apparent under nutrient-limited conditions and results in respiratory oscillations (YROs). YROs share features with circadian rhythms and interact with, but are independent of, the cell division cycle. Here, we show that YROs minimise energy expenditure by restricting protein synthesis until sufficient resources are stored, while maintaining osmotic homeostasis and protein quality control. Although nutrient supply is constant, cells sequester and store metabolic resources via increased transport, autophagy and biomolecular condensation. Replete stores trigger increased H+ export which stimulates TORC1 and liberates proteasomes, ribosomes, chaperones and metabolic enzymes from non-membrane bound compartments. This facilitates translational bursting, liquidation of storage carbohydrates, increased ATP turnover, and the export of osmolytes. We propose that dynamic regulation of ion transport and metabolic plasticity are required to maintain osmotic and protein homeostasis during remodelling of eukaryotic proteomes, and that bioenergetic constraints selected for temporal organisation that promotes oscillatory behaviour.


Assuntos
Metabolismo Energético/fisiologia , Células Eucarióticas/fisiologia , Proteostase/fisiologia , Autofagia/fisiologia , Reatores Biológicos , Ritmo Circadiano , Glicogênio/metabolismo , Resposta ao Choque Térmico , Ionomicina , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Metabolômica , Chaperonas Moleculares , Concentração Osmolar , Pressão Osmótica , Oxigênio/metabolismo , Biossíntese de Proteínas , Processamento de Proteína Pós-Traducional , Proteoma , Proteômica , Ribossomos , Leveduras/fisiologia
2.
Mol Cell ; 79(6): 876-877, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32946761

RESUMO

In this issue of Molecular Cell, Jalihal et al. (2020) show that cell volume changes upon osmotic stress result in rapid and reversible condensation of numerous multivalent proteins.


Assuntos
Proteínas , Tamanho Celular , Pressão Osmótica
3.
Proc Natl Acad Sci U S A ; 117(33): 20292-20297, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32747529

RESUMO

Nuclear Factor of Activated T cells 5 (NFAT5) is a transcription factor (TF) that mediates protection from adverse effects of hypertonicity by increasing transcription of genes, including those that lead to cellular accumulation of protective organic osmolytes. NFAT5 has three intrinsically ordered (ID) activation domains (ADs). Using the NFAT5 N-terminal domain (NTD), which contains AD1, as a model, we demonstrate by biophysical methods that the NTD senses osmolytes and hypertonicity, resulting in stabilization of its ID regions. In the presence of sufficient NaCl or osmolytes, trehalose and sorbitol, the NFAT5 NTD undergoes a disorder-to-order shift, adopting higher average secondary and tertiary structure. Thus, NFAT5 is activated by the stress that it protects against. In its salt and/or osmolyte-induced more ordered conformation, the NTD interacts with several proteins, including HMGI-C, which is known to protect against apoptosis. These findings raise the possibility that the increased intracellular ionic strength and elevated osmolytes caused by hypertonicity activate and stabilize NFAT5.


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Fatores de Transcrição/química , Escherichia coli/metabolismo , Pressão Osmótica , Ligação Proteica , Dobramento de Proteína , Cloreto de Sódio , Sorbitol , Fatores de Transcrição/metabolismo , Trealose
4.
Mol Cell ; 79(6): 978-990.e5, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32857953

RESUMO

Processing bodies (PBs) and stress granules (SGs) are prominent examples of subcellular, membraneless compartments that are observed under physiological and stress conditions, respectively. We observe that the trimeric PB protein DCP1A rapidly (within ∼10 s) phase-separates in mammalian cells during hyperosmotic stress and dissolves upon isosmotic rescue (over ∼100 s) with minimal effect on cell viability even after multiple cycles of osmotic perturbation. Strikingly, this rapid intracellular hyperosmotic phase separation (HOPS) correlates with the degree of cell volume compression, distinct from SG assembly, and is exhibited broadly by homo-multimeric (valency ≥ 2) proteins across several cell types. Notably, HOPS sequesters pre-mRNA cleavage factor components from actively transcribing genomic loci, providing a mechanism for hyperosmolarity-induced global impairment of transcription termination. Our data suggest that the multimeric proteome rapidly responds to changes in hydration and molecular crowding, revealing an unexpected mode of globally programmed phase separation and sequestration.


Assuntos
Endorribonucleases/genética , Precursores de RNA/genética , Estresse Fisiológico/genética , Transativadores/genética , Terminação da Transcrição Genética , Animais , Tamanho Celular , Sobrevivência Celular/genética , Humanos , Pressão Osmótica/fisiologia , Proteoma/genética
5.
Int J Food Microbiol ; 330: 108783, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-32659523

RESUMO

The contamination of Aspergillus carbonarius causes decreases and great decay of agricultural products, and threatens the human and animal health by producing mycotoxins, especially ochratoxin A. Bacillus subtilis has been proved to efficiently inhibit the growth of A. carbonarius. Revealing the major active compound and the mechanisms for the antifungal of B. subtilis are essential to enhance its antifungal activity and control the quality of antifungal products made of it. In this study, we determined that iturin A is the major compound that inhibits Aspergillus carbonarius, a widespread fungal pathogen of grape and other fruits. Iturin A significantly inhibited growth and ochratoxin A production of A. carbonarius with minimal inhibitory concentrations (MICs) of 10 µg/mL and 0.312 µg/mL, respectively. Morphological observations revealed that iturin A caused swelling of the fungal cells and thinning of the cell wall and membrane at 1/2 MIC, whereas it inhibited fungal spore germination and caused mitochondrial swelling at higher concentrations. A differential transcriptomic analysis indicated that the mechanisms used by iturin A to inhibit A. carbonarius were to downregulate the expression of genes related to cell membrane, transport, osmotic pressure, oxidation-reduction processes, and energy metabolism. Among the down-regulated genes, those related to the transport capacity were most significantly influenced, including the increase of energy-related transport pathways and decrease of other pathways. Notably, the genes related to taurine and hypotaurine metabolism were also decreased, indicating iturin A potentially cause the occurrence of osmotic imbalance in A. carbonarius, which may be the intrinsic cause for the swelling of fungal cells and mitochondria. Overall, iturin A produced by B. subtilis played important roles to inhibit A. carbonarius via changing the fungal cell structure and causing perturbations to energy, transport and osmotic pressure metabolisms in fungi. The results indicated a new direction for researches on the mechanisms for lipopeptides and provided useful information to develop more efficient antifungal agents, which are important to agriculture and biomedicine.


Assuntos
Antifúngicos/farmacologia , Aspergillus/efeitos dos fármacos , Aspergillus/metabolismo , Bacillus subtilis/metabolismo , Peptídeos Cíclicos/farmacologia , Antifúngicos/metabolismo , Aspergillus/genética , Aspergillus/crescimento & desenvolvimento , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/genética , Metabolismo Energético/efeitos dos fármacos , Metabolismo Energético/genética , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Micotoxinas/metabolismo , Pressão Osmótica/efeitos dos fármacos , Peptídeos Cíclicos/metabolismo , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/metabolismo , Transcriptoma
6.
Am J Physiol Heart Circ Physiol ; 319(2): H410-H421, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32648820

RESUMO

Cardiac t tubules undergo significant remodeling in various pathological and experimental conditions, which can be associated with mechanical or osmotic stress. In particular, it has been shown that removal of hyposmotic stress can lead to sealing of t tubules. However, the mechanisms underlying the sealing process remain essentially unknown. In this study we used dextran trapping assay to demonstrate that in adult mouse cardiomyocytes, t-tubular sealing can also be induced by hyperosmotic challenge and that both hypo- and hyperosmotic sealing display a clear threshold behavior requiring ≈100 mosmol/L minimal stress. Importantly, during both hypo- and hyperosmotic challenges, the sealing of t tubules occurs only during the shrinking phase. Analysis of the time course of t-tubular remodeling following removal of hyposmotic stress shows that t tubules become sealed essentially instantly, well before any significant reduction in cell size can be observed. Overall, the data support the hypothesis that the critical event in the process of t-tubular sealing during osmotic challenges is detachment (peeling) of the membrane from the underlying cytoskeleton due to suprathreshold stress.NEW & NOTEWORTHY This study provides new insights into how t-tubular membranes respond to osmotic forces. In particular, the data show that osmotically induced sealing of cardiac t tubules is a threshold phenomenon initiated by detachment of t-tubular membrane from the underlying cytoskeleton. The findings are consistent with the hypothesis that final sealing of t tubules is driven by negative hydrostatic intracellular pressure coincident with cell shrinking.


Assuntos
Membrana Celular/patologia , Tamanho Celular , Citoesqueleto/patologia , Miócitos Cardíacos/patologia , Pressão Osmótica , Vacúolos/patologia , Animais , Membrana Celular/metabolismo , Citoesqueleto/metabolismo , Feminino , Masculino , Camundongos Endogâmicos C57BL , Miócitos Cardíacos/metabolismo , Fatores de Tempo , Vacúolos/metabolismo
7.
Artigo em Inglês | MEDLINE | ID: mdl-32502716

RESUMO

Thymol is a natural phenolic monoterpene widely produced by different species belonging to the Labiateae family. Although the thymol phytotoxicity is well known, the knowledge of its potential toxic mechanism is still limited. In this regard, the model species Arabidopsis thaliana was treated for 16 days by sub-irrigation with 300 µM of thymol. The results confirmed the high phytotoxic potential of this phenolic compound, which caused a reduction in plant growth and development. Thymol induced a water status alteration accompanied by an increase in ABA content and stomatal closure. Furthermore, leaves appeared necrotic in the margins and their temperature rinsed. The increase in H2O2 content suggested an oxidative stress experienced by treated plants. Both metabolomic and proteomic analysis confirmed this hypothesis showing a strong increase in osmoprotectants content, such as galactinol and proline, and a significant up-accumulation of proteins involved in ROS detoxification. Furthermore, the down-accumulation of proteins and pigments involved in the photosynthetic machinery, the increase in light sensitivity and the lower PSII efficiency well indicated a reduction in photosynthetic activity. Overall, we can postulate that thymol-induced phytotoxicity could be related to a combined osmotic and oxidative stress that resulted in reduced plant development.


Assuntos
Arabidopsis/efeitos dos fármacos , Metaboloma , Proteoma , Timol/toxicidade , Ácido Abscísico , Arabidopsis/crescimento & desenvolvimento , Peróxido de Hidrogênio , Pressão Osmótica , Estresse Oxidativo , Fotossíntese , Folhas de Planta
8.
PLoS One ; 15(6): e0234085, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32497140

RESUMO

Late embryogenesis abundant (LEA) proteins are widely involved in many adverse conditions among plants. In this study, we isolated a LEA4 gene from alfalfa (Medicago sativa L.) termed MsLEA4-4 via a homology cloning strategy. MsLEA4-4 encodes 166 amino acids, and the structural analysis showed that the gene contained five repeating TAQAAKEKTQQ amino acid motifs. There were a large number of α-helix in MsLEA4-4, and belongs to hydrophilic amino acid. Subcellular localization analysis showed that MsLEA4-4 was localized in the nucleus. The MsLEA4-4 promoter consisted of G-box and A-box elements, abscisic acid-responsive elements (ABREs), photo regulation and photoperiodic-controlling cis-acting elements, and endosperm expression motifs. The MsLEA4-4 overexpressing in Arabidopsis conferred late-germination phenotypes. Resistance of the overexpressed plants to abiotic stress significantly outperformed the wild-type (WT) plants. Under salt stress and abscisic acid treatment, with more lateral roots and higher chlorophyll content, the overexpressed plants has a higher survival rate measured against WT. Compared to those in the WT plants, the levels of soluble sugar and the activity of various antioxidant enzymes were elevated in the overexpressed plants, whereas the levels of proline and malondialdehyde were significantly reduced. The expression levels of several genes such as ABF3, ABI5, NCED5, and NCED9 increased markedly in the overexpressed plants compared to the WT under osmotic stress.


Assuntos
Arabidopsis/genética , Arabidopsis/fisiologia , Secas , Medicago sativa/genética , Estresse Oxidativo/genética , Proteínas de Plantas/genética , Estresse Salino/genética , Sequência de Aminoácidos , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Sequência de Bases , Clonagem Molecular , Expressão Gênica , Germinação , Pressão Osmótica , Proteínas de Plantas/química , Regiões Promotoras Genéticas/genética
9.
Nat Commun ; 11(1): 3171, 2020 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-32576833

RESUMO

Precise regulation of gene expression in response to environmental changes is crucial for cell survival, adaptation and proliferation. In eukaryotic cells, extracellular signal integration is often carried out by Mitogen-Activated Protein Kinases (MAPK). Despite a robust MAPK signaling activity, downstream gene expression can display a great variability between single cells. Using a live mRNA reporter, here we monitor the dynamics of transcription in Saccharomyces cerevisiae upon hyper-osmotic shock. We find that the transient activity of the MAPK Hog1 opens a temporal window where stress-response genes can be activated. We show that the first minutes of Hog1 activity are essential to control the activation of a promoter. Chromatin repression on a locus slows down this transition and contributes to the variability in gene expression, while binding of transcription factors increases the level of transcription. However, soon after Hog1 activity peaks, negative regulators promote chromatin closure of the locus and transcription progressively stops.


Assuntos
Cromatina/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Fatores de Transcrição/metabolismo , Regulação Fúngica da Expressão Gênica , Pressão Osmótica/fisiologia , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Transdução de Sinais
10.
Nat Commun ; 11(1): 2926, 2020 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-32522991

RESUMO

Metabolic changes alter the cellular milieu; can this also change intracellular protein folding? Since proteostasis can modulate mutational buffering, if change in metabolism has the ability to change protein folding, arguably, it should also alter mutational buffering. Here we find that altered cellular metabolic states in E. coli buffer distinct mutations on model proteins. Buffered-mutants have folding problems in vivo and are differently chaperoned in different metabolic states. Notably, this assistance is dependent upon the metabolites and not on the increase in canonical chaperone machineries. Being able to reconstitute the folding assistance afforded by metabolites in vitro, we propose that changes in metabolite concentrations have the potential to alter protein folding capacity. Collectively, we unravel that the metabolite pools are bona fide members of proteostasis and aid in mutational buffering. Given the plasticity in cellular metabolism, we posit that metabolic alterations may play an important role in cellular proteostasis.


Assuntos
Proteostase/fisiologia , Escherichia coli/genética , Escherichia coli/metabolismo , Metaboloma/genética , Mutação/genética , Pressão Osmótica/fisiologia , Dobramento de Proteína , Proteostase/genética
11.
PLoS One ; 15(4): e0232244, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32353000

RESUMO

BACKGROUND: Microorganisms living in saline environments are forced to regulate turgor via the synthesis of organic osmoprotective compounds. Microbial adaptation to fluctuations in external salinity includes degradation of compatible solutes. Here we have examined the biochemical pathway of degradation of the cyclic imino acid ectoine, the major osmoprotector in halotolerant methane-utilizing bacteria. METHODS: The BLAST search of the genes involved in ectoine degradation in the halotolerant methanotroph Methylotuvimicrobium alcaliphilum 20Z was performed with the reference sequences of Halomonas elongata. The genes for the key enzymes of the pathway were disrupted by insertion mutagenesis and the cellular metabolites in the methanol extracts of mutant cells were analyzed by HPLC. The doeA gene from Mm. alcaliphilum 20Z was heterologously expressed in Escherichia coli to identify the product of ectoine hydrolysis catalyzed by ectoine hydrolase DoeA. RESULTS: We have shown that the halotolerant methanotroph Mm. alcaliphilum 20Z possesses the doeBDAC gene cluster coding for putative ectoine hydrolase (DoeA), Nα-acetyl-L-2,4-diaminobutyrate deacetylase (DoeB), diaminobutyrate transaminase (DoeD) and aspartate-semialdehyde dehydrogenase (DoeC). The deletion of the doeA gene resulted in accumulation of the higher level of ectoine compared to the wild type strain. Nγ-acetyl-L-2,4-diaminobutyrate (Nγ-acetyl-DAB), a substrate for ectoine synthase, was found in the cytoplasm of the wild type strain. Nα-acetyl-L-2,4-diaminobutyrate (Nα-acetyl-DAB), a substrate for the DoeB enzyme, appeared in the cells as a result of exposure of the doeB mutant to low osmotic pressure. The genes for the enzymes involved in ectoine degradation were found in all aerobic methylotrophs capable of ectoine biosynthesis. These results provide the first evidence for the in vivo operation of the ectoine degradation pathway in methanotrophs and thus expand our understanding of the regulation mechanisms of bacterial osmoadaptation. CONCLUSIONS: During adaptation to the changes in external osmolarity, halophilic and halotolerant methylotrophs cleave ectoine, thereby entering the carbon and nitrogen of the compatible solute to the central metabolic pathways. The biochemical route of ectoine degradation in the halotolerant methanotroph Mm. alcaliphilum 20Z is similar to that in heterotrophic halophiles. We have shown that ectoine hydrolase DoeA in this methanotroph hydrolyzes ectoine with the formation of the only isomer: Nα-acetyl-DAB. All aerobic methylotrophs capable of ectoine biosynthesis harbor the genetic determinants for ectoine degradation.


Assuntos
Diamino Aminoácidos/metabolismo , Redes e Vias Metabólicas/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica/genética , Genes Bacterianos/genética , Halomonas/genética , Halomonas/metabolismo , Redes e Vias Metabólicas/genética , Methylococcaceae/genética , Methylococcaceae/metabolismo , Família Multigênica/genética , Pressão Osmótica/fisiologia , Salinidade
12.
J Pharmacol Sci ; 143(3): 176-181, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32386905

RESUMO

The volume-regulated anion channel (VRAC) plays a central role in maintaining cell volume in response to osmotic stress. Leucine-rich repeat-containing 8A (LRRC8A) was recently identified as an essential component of VRAC although other Cl- channels were also suggested to contribute to VRAC. VRAC is activated when a cell is challenged with a hypotonic environment or even in isotonic conditions challenged with different stimuli. It is not clear how VRAC is activated and whether activation of VRAC in hypotonic and isotonic conditions share the same mechanism. In this present study, we investigated relative contribution of LRRC8A and anoctamin 1(ANO1) to VRAC currents activated by fetal bovine serum (FBS) in isotonic condition, and studied the role of intracellular Ca2+ in this activation. We used CRISPR/Cas9 gene editing approach, electrophysiology, and pharmacology approaches to show that VRAC currents induced by FBS is mostly mediated by LRRC8A in HEK293 cells, but also with significant contribution from ANO1. FBS induces Ca2+ transients and these Ca2+ signals are required for the activation of VRAC by serum. These findings will help to further understand the mechanism in activation of VRAC.


Assuntos
Anoctamina-1/fisiologia , Cálcio/metabolismo , Tamanho Celular , Proteínas de Membrana/fisiologia , Proteínas de Neoplasias/fisiologia , Canais de Ânion Dependentes de Voltagem/metabolismo , Canais de Ânion Dependentes de Voltagem/fisiologia , Animais , Proteína 9 Associada à CRISPR/genética , Bovinos , Canais de Cloreto/metabolismo , Canais de Cloreto/fisiologia , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Edição de Genes , Células HEK293 , Humanos , Pressão Osmótica/fisiologia , Soro
13.
Water Res ; 176: 115732, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32278921

RESUMO

With increasing freshwater scarcity and greater use of seawater, fluctuating salinities are becoming common in water treatment systems. This can be challenging for salinity-sensitive processes like nitrification, especially in recirculating aquaculture systems (RAS), where maintaining nitrification efficiency is crucial for fish health. This study was undertaken to determine if prior exposure to seawater (priming) could improve nitrification in moving bed biofilm reactors (MBBR) under salinity increase from freshwater to seawater. The results showed that seawater-primed freshwater MBBRs had less than 10% reduction in nitrification activity and twice the ammonia oxidation capacity of the unprimed bioreactors after seawater transfer. The primed biofilms had different microbial community composition but the same nitrifying taxa, suggesting that priming promoted physiological adaptation of the nitrifiers. Priming may also have strengthened the extrapolymeric matrix protecting the nitrifiers. In MBBRs started up in brackish water (12‰ salinity), seawater priming had no significant impact on the nitrification activity and the microbial community composition. These bioreactors were inherently robust to salinity increase, likely because they were already primed to osmotic stress by virtue of their native salinity of 12‰. The results show that osmotic stress priming is an effective strategy for improving salinity acclimation in nitrifying biofilms and can be applied to water treatment systems where salinity variations are expected.


Assuntos
Biofilmes , Reatores Biológicos , Aclimatação , Amônia , Nitrificação , Pressão Osmótica , Salinidade
14.
Artigo em Inglês | MEDLINE | ID: mdl-32224382

RESUMO

Osmotic stresses caused by reduced water availability or the accumulation of salts in the soil can be highly damaging to plants. The objective of this study was to investigate physiological responses and tolerance mechanisms of two turfgrass species (seashore paspalum and centipedegrass) with distinct differences in salinity tolerance exposed to osmotic and iso-osmotic salt stresses. Three turfgrass genotypes including seashore paspalums 'Seastar' and 'UGP113', and centipedegrass 'TifBlair' were grown in ½ strength Hoagland's solution with three different treatment conditions; control (no external addition), salt stress (-0.4 MPa by adding NaCl) and osmotic stress [-0.4 MPa by adding polyethylene glycol (PEG)]. Osmotic stress damages were more severe with greater reductions in turf quality, photochemical efficiency (Fv/Fm), relative water content (RWC) and leaf water potential (Ψw) compared to iso-osmotic salt stress in both seashore paspalum and centipedegrass. Greater osmotic adjustment (OA) with greater accumulation of metabolically inexpensive inorganic osmolytes (Na+) helped turfgrasses to lessen damages in salt stress compared to osmotic stress. However, such accumulation of Na+ resulted ion-toxicity and triggered some damages in terms of increased electrolyte leakage (EL) and reduced total protein in salt-sensitive centipedegrass. Seashore paspalum had better ion regulation and also maintained greater antioxidant enzyme activities compared to centipedegrass; therefore it was able to avoid ion-specific damages under salt stress. Differences in the utilization of specific solutes for osmotic adjustment and antioxidant metabolism are partially responsible for the differences in salt versus osmotic stress responses in these species; the regulation of these defense mechanisms requires further investigation.


Assuntos
Pressão Osmótica , Poaceae/fisiologia , Estresse Salino , Tolerância ao Sal , Genótipo , Paspalum/crescimento & desenvolvimento , Paspalum/fisiologia , Poaceae/genética
15.
Environ Sci Technol ; 54(10): 6385-6395, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32310656

RESUMO

Membrane deformation is a significant problem in osmotically driven membrane processes, as it restricts practical operating conditions and reduces overall process performance due to unfavorable alteration of membrane permeation characteristics. In this respect, a spacer plays a crucial role, as it dictates the form and extent of membrane deformation in association with concentration polarization (CP), which is also influenced by spacer-induced hydrodynamic behavior near the membrane surface. These two roles of spacers on membrane permeation characteristics are inherently inseparable with the coexistence of hydraulic and osmotic pressures. Here, we suggest a novel analytical method to differentially quantify the proportions of effective osmotic pressure drop caused by membrane deformation and CP. Furthermore, we tested two different FO membranes with three different spacer configurations to define and discuss different forms of membrane deformation and their effects on membrane permeation characteristics. The differential analysis revealed the effect of spacer configuration on effective osmotic pressure drop in membrane deformation (up to ∼201% of variation) is much greater than that in CP (up to ∼20.1% of variation). In addition, a combined configuration of a feed spacer and tricot spacer demonstrated its ability of mitigating membrane deformation with lower selectivity loss and channel pressure drop under pressurization.


Assuntos
Filtração , Purificação da Água , Hidrodinâmica , Membranas Artificiais , Osmose , Pressão Osmótica , Pressão
16.
Invest Ophthalmol Vis Sci ; 61(4): 2, 2020 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-32271891

RESUMO

Purpose: Contact lenses, osmotic stressors, and chemical burns may trigger severe discomfort and vision loss by damaging the cornea, but the signaling mechanisms used by corneal epithelial cells (CECs) to sense extrinsic stressors are not well understood. We therefore investigated the mechanisms of swelling, temperature, strain, and chemical transduction in mouse CECs. Methods: Intracellular calcium imaging in conjunction with electrophysiology, pharmacology, transcript analysis, immunohistochemistry, and bioluminescence assays of adenosine triphosphate (ATP) release were used to track mechanotransduction in dissociated CECs and epithelial sheets isolated from the mouse cornea. Results: The transient receptor potential vanilloid (TRPV) transcriptome in the mouse corneal epithelium is dominated by Trpv4, followed by Trpv2, Trpv3, and low levels of Trpv1 mRNAs. TRPV4 protein was localized to basal and intermediate epithelial strata, keratocytes, and the endothelium in contrast to the cognate TRPV1, which was confined to intraepithelial afferents and a sparse subset of CECs. The TRPV4 agonist GSK1016790A induced cation influx and calcium elevations, which were abolished by the selective blocker HC067047. Hypotonic solutions, membrane strain, and moderate heat elevated [Ca2+]CEC with swelling- and temperature-, but not strain-evoked signals, sensitive to HC067047. GSK1016790A and swelling evoked calcium-dependent ATP release, which was suppressed by HC067027 and the hemichannel blocker probenecid. Conclusions: These results demonstrate that cation influx via TRPV4 transduces osmotic and thermal but not strain inputs to CECs and promotes hemichannel-dependent ATP release. The TRPV4-hemichannel-ATP signaling axis might modulate corneal pain induced by excessive mechanical, osmotic, and chemical stimulation.


Assuntos
Epitélio Anterior/metabolismo , Mecanotransdução Celular/fisiologia , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , Sinalização do Cálcio/fisiologia , Células Cultivadas , Eletrofisiologia , Feminino , Regulação da Expressão Gênica/fisiologia , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pressão Osmótica , Técnicas de Patch-Clamp , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Canais de Cátion TRPV/genética
17.
Proc Natl Acad Sci U S A ; 117(16): 8924-8933, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32265285

RESUMO

Adaptation to environmental changes is crucial for cell fitness. In Saccharomyces cerevisiae, variations in external osmolarity trigger the activation of the stress-activated protein kinase Hog1 (high-osmolarity glycerol 1), which regulates gene expression, metabolism, and cell-cycle progression. The activation of this kinase leads to the regulation of G1, S, and G2 phases of the cell cycle to prevent genome instability and promote cell survival. Here we show that Hog1 delays mitotic exit when cells are stressed during metaphase. Hog1 phosphorylates the nucleolar protein Net1, altering its affinity for the phosphatase Cdc14, whose activity is essential for mitotic exit and completion of the cell cycle. The untimely release of Cdc14 from the nucleolus upon activation of Hog1 is linked to a defect in ribosomal DNA (rDNA) and telomere segregation, and it ultimately delays cell division. A mutant of Net1 that cannot be phosphorylated by Hog1 displays reduced viability upon osmostress. Thus, Hog1 contributes to maximizing cell survival upon stress by regulating mitotic exit.


Assuntos
Proteínas de Ciclo Celular/metabolismo , Segregação de Cromossomos/fisiologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Mitose/fisiologia , Proteínas Nucleares/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Ciclo Celular/genética , DNA Ribossômico/metabolismo , Mutação , Proteínas Nucleares/genética , Pressão Osmótica/fisiologia , Fosforilação/genética , Proteínas Tirosina Fosfatases/metabolismo , Saccharomyces cerevisiae/fisiologia , Proteínas de Saccharomyces cerevisiae/genética , Homeostase do Telômero/fisiologia
18.
Proc Natl Acad Sci U S A ; 117(11): 5604-5609, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32132211

RESUMO

Recent experiments reveal that the volume of adhered cells is reduced as their basal area is increased. During spreading, the cell volume decreases by several thousand cubic micrometers, corresponding to large pressure changes of the order of megapascals. We show theoretically that the volume regulation of adhered cells is determined by two concurrent conditions: mechanical equilibrium with the extracellular environment and a generalization of Donnan (electrostatic) equilibrium that accounts for active ion transport. Spreading affects the structure and hence activity of ion channels and pumps, and indirectly changes the ionic content in the cell. We predict that more ions are released from the cell with increasing basal area, resulting in the observed volume-area dependence. Our theory is based on a minimal model and describes the experimental findings in terms of measurable, mesoscale quantities. We demonstrate that two independent experiments on adhered cells of different types fall on the same master volume-area curve. Our theory also captures the measured osmotic pressure of adhered cells, which is shown to depend on the number of proteins confined to the cell, their charge, and their volume, as well as the ionic content. This result can be used to predict the osmotic pressure of cells in suspension.


Assuntos
Adesão Celular , Tamanho Celular , Modelos Teóricos , Osmorregulação/fisiologia , Animais , Humanos , Transporte de Íons , Pressão Osmótica
19.
J Environ Manage ; 261: 110229, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32148299

RESUMO

Technologies for water recycling within oil refineries have been gaining interest at an extensive rate due to the large volume of wastewater generated, high dependency of water and the progressive scarcity of this valuable resource. Phenols are part of a specific class of organic pollutants that have been contributing to a low-quality effluent in oil refineries due to their hazardous nature and strict environmental legislation associated. The reuse of stripped sour water within refineries is often blocked due to its rich phenolic content. This study evaluates the retention of phenols in refinery wastewater through reverse osmosis (RO) at its major source of emission, for water reclamation. The RO membrane selected exhibited rejections of up to 98% of phenols and 99% of both chemical oxygen demand (COD) and total organic carbon (TOC). Permeate quality remained intact despite flux decline caused by phenolic and hydrocarbon adsorption when the oil content, in the feed, reached 771 ppm. The effluent's low conductivity due to lack of salts led to minor osmotic pressure differences (less than 2.5 bar at a volume concentration factor of 3), therefore, showing appealing performances of reverse osmosis filtration. Characterization of all permeates obtained from cross-flow filtration experiments showed COD levels in line with water reuse quality standards for make-up water in cooling processes.


Assuntos
Eliminação de Resíduos Líquidos , Purificação da Água , Filtração , Hidrocarbonetos , Membranas Artificiais , Osmose , Pressão Osmótica , Fenóis , Águas Residuárias
20.
Electron. j. biotechnol ; 44: 19-24, Mar. 2020. ilus, graf
Artigo em Inglês | LILACS | ID: biblio-1087631

RESUMO

BACKGROUND: Pyruvic acid (PA), a vital α-oxocarboxylic acid, plays an important role in energy and carbon metabolism. The oleaginous yeast Yarrowia lipolytica (Y. lipolytica) has considerable potential for the production of PA. An increased NaCl concentration reportedly increases the biomass and PA yield of Y. lipolytica. RESULTS: To increase the yield of PA, the NaCl-tolerant Y. lipolytica A4 mutant was produced using the atmospheric and room temperature plasma method of mutation. The A4 mutant showed growth on medium containing 160 g/L NaCl. The PA yield of the A4 mutant reached 97.2 g/L at 120 h (0.795 g/g glycerol) in a 20-L fermenter with glycerol as the sole carbon source, which was 28.9% higher than that of the parental strain. CONCLUSION: The PA yield from Y. lipolytica can be improved by increasing its NaCl tolerance.


Assuntos
Ácido Pirúvico/metabolismo , Yarrowia/genética , Yarrowia/metabolismo , Pressão Osmótica , Leveduras , Carbono/metabolismo , Cloreto de Sódio , Reatores Biológicos , Tolerância ao Sal/genética , Fermentação , Glicerol/metabolismo , Mutação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA