ABSTRACT
Objetivo Evaluar la costoefectividad incremental del régimen combinado de mirabegron/solifenacina en comparación con el uso temprano de toxina botulínica, desde la perspectiva del sistema de salud colombiano, para el tratamiento de adultos con vejiga hiperactiva. Métodos Se empleó un modelo de Markov en que se comparan dos secuencias de tratamiento, una con y otra sin mirabegron/solifenacina, para evaluar la costoefectividad en un horizonte temporal de cinco años. Debido a la perspectiva de análisis, sólo se tuvieron en cuenta los costos médicos directos. La eficacia del tratamiento evaluado y su comparador fue medida en términos de la reducción de episodios diarios de incontinencia y de la frecuencia de micciones. Los costos fueron expresados en pesos colombianos de 2019, y se aplicó una tasa de descuento de 5% tanto para desenlaces como para costos. Resultados Para el caso base, el costo del tratamiento en la secuencia que incluye mirabegron/solifenacina fue mayor, pero generó un mayor número de años de vida ajustados por calidad, y así e obtuvo una razón de costoefectividad incremental de $13.637,184 si se considera el desenlace de reducción de episodios diarios de incontinencia de 50%, y de $29.313,848 si se considera el del 100%. Conclusiones De acuerdo con los resultados de esta evaluación, para un horizonte de análisis de cinco años, la secuencia de tratamiento con mirabegron/solifenacina es una alternativa costoefectiva, si se considera un umbral de disposición a pagar de tres veces el producto interno bruto (PIB) per cápita.
Aim To evaluate the incremental cost-effectiveness of the combined regimen of mirabegron/solifenacin compared with the early use of botulinum toxin, from the perspective of the Colombian health system, for the treatment of adults with overactive bladder. Methods A Markov model comparing two treatment sequences, one with and one without mirabegron/solifenacin, was used to assess cost-effectiveness over a five-year period. Due to the perspective of the analysis, only direct medical costs were considered. The efficacy of the evaluated treatment and its comparator was measured in terms of the reduction in the daily incontinence episodes and the frequency of micturition. The costs were expressed in Colombian pesos of 2019, and a discount rate of 5% was applied for both outcomes and costs. Results For the base case, the cost of the treatment in the sequence that includes mirabegron/solifenacin was higher, but it generated a greater number of quality-adjusted years of life, thus obtaining an incremental cost-effectiveness ratio of $13,637,184 when considering the outcome of 50% of reduction in the daily incontinence episodes, and $29,313,848 when considering 100%. Conclusions According to the results of the present assessment, for a five-year period of analysi, the mirabegron/solifenacin treatment sequence is a cost-effective alternative when considering a threshold of willingness to pay three times the per capita gross domestic product (GDP).
Subject(s)
Humans , Syndrome , Urinary Bladder, Overactive , Guanosine Diphosphate , Effectiveness , Botulinum Toxins , Treatment Outcome , Solifenacin Succinate , Gender IdentityABSTRACT
The metabolic and signaling functions of lysosomes depend on their intracellular positioning and trafficking, but the underlying mechanisms are little understood. Here, we have discovered a novel septin GTPase-based mechanism for retrograde lysosome transport. We found that septin 9 (SEPT9) associates with lysosomes, promoting the perinuclear localization of lysosomes in a Rab7-independent manner. SEPT9 targeting to mitochondria and peroxisomes is sufficient to recruit dynein and cause perinuclear clustering. We show that SEPT9 interacts with both dynein and dynactin through its GTPase domain and N-terminal extension, respectively. Strikingly, SEPT9 associates preferentially with the dynein intermediate chain (DIC) in its GDP-bound state, which favors dimerization and assembly into septin multimers. In response to oxidative cell stress induced by arsenite, SEPT9 localization to lysosomes is enhanced, promoting the perinuclear clustering of lysosomes. We posit that septins function as GDP-activated scaffolds for the cooperative assembly of dynein-dynactin, providing an alternative mechanism of retrograde lysosome transport at steady state and during cellular adaptation to stress.
Subject(s)
Dynactin Complex/metabolism , Dyneins/metabolism , Septins/metabolism , Animals , COS Cells , Chlorocebus aethiops , Endosomes/metabolism , Guanosine Diphosphate/metabolism , HeLa Cells , Humans , Lysosomes/metabolism , Neurons/metabolism , Oxidative Stress , Protein Binding , Protein Domains , Protein Transport , Rats , Septins/chemistry , rab GTP-Binding Proteins/metabolism , rab7 GTP-Binding ProteinsABSTRACT
Ribosome biogenesis in eukaryotes requires the participation of several transactivation factors that are involved in the modification, assembly, transport and quality control of the ribosomal subunits. One of these factors is the Large subunit GTPase 1 (Lsg1), a protein that acts as the release factor for the export adaptor named Nonsense-mediated mRNA decay 3 protein (Nmd3) and facilitates the incorporation of the last structural protein uL16 into the 60S subunit. Here, we characterised the recombinant yeast Lsg1 and studied its catalysis and binding properties for guanine nucleotides. We described the interaction of Lsg1 with guanine nucleotides alone and in the presence of the complex Nmd3â¢60S using fluorescence spectroscopy. Lsg1 has a greater affinity for GTP than for GDP suggesting that in the cell cytoplasm it exists mainly bound to the former. In the presence of 60S subunits loaded with Nmd3, the affinity of Lsg1 for both nucleotides increases but to a larger extent towards GTP. From this observation together with the excess of GTP present in the cytoplasm of exponentially growing cells over that of GDP, we can infer that the pre-ribosomal particle composed by Nmd3â¢60S acts as a GTP Stabilising Factor for Lsg1. Additionally, Lsg1 undergoes different conformational changes depending on its binding partner or the guanine nucleotides it interacts with. Steady-state kinetic analysis of free Lsg1 indicated slow GTP hydrolysis with values of kcat 1â¯min-1 and Km of 34⯵M.
Subject(s)
GTP-Binding Proteins/metabolism , Guanosine Diphosphate/metabolism , Guanosine Triphosphate/metabolism , RNA-Binding Proteins/metabolism , Ribosomal Proteins/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae/enzymology , Binding Sites , Cloning, Molecular , Escherichia coli/genetics , Escherichia coli/metabolism , GTP-Binding Proteins/chemistry , GTP-Binding Proteins/genetics , Gene Expression , Genetic Vectors/chemistry , Genetic Vectors/metabolism , Guanosine Diphosphate/chemistry , Guanosine Triphosphate/chemistry , Kinetics , Maltose-Binding Proteins/chemistry , Maltose-Binding Proteins/genetics , Maltose-Binding Proteins/metabolism , Models, Molecular , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Protein Structure, Tertiary , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/genetics , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Ribosomal Proteins/chemistry , Ribosomal Proteins/genetics , Ribosome Subunits, Large, Eukaryotic/enzymology , Ribosome Subunits, Large, Eukaryotic/genetics , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/genetics , Substrate Specificity , ThermodynamicsABSTRACT
MAIN CONCLUSION: Reduced GDP-L-galactose phosphorylase expression and deficiency of ascorbic acid content lead to decreased fruit set and yield in tomato plants. Reduced GDP-L-galactose phosphorylase expression and deficiency of ascorbic acid content lead to decreased fruit set and yield in tomato plants. GDP-L-galactose phosphorylase (GGP) catalyzes the first step committed to ascorbic acid synthesis. The participation of GDP-L-galactose phosphorylase and ascorbate in tomato fruit production and quality was studied in this work using two SlGGP1 deficient EMS Micro-Tom mutants. The SlGGP1 mutants display decreased concentrations of ascorbate in roots, leaves, flowers, and fruit. The initiation of anthesis is delayed in ggp1 plants but the number of flowers is similar to wild type. The number of fruits is reduced in ggp1 mutants with an increased individual weight. However, the whole fruit biomass accumulation is reduced in both mutant lines. Fruits of the ggp1 plants produce more ethylene and show higher firmness and soluble solids content than the wild type after the breaker stage. Leaf CO2 uptake decreases about 50% in both ggp1 mutants at saturating light conditions; however, O2 production in an enriched CO2 atmosphere is only 19% higher in wild type leaves. Leaf conductance that is largely reduced in both mutants may be the main limitation for photosynthesis. Sink-source assays and hormone concentration were measured to determine restrictions to fruit yield. Manipulation of leaf area/fruit number relationship demonstrates that the number of fruits and not the provision of photoassimilates from the source restricts biomass accumulation in the ggp1 lines. The lower gibberellins concentration measured in the flowers would contribute to the lower fruit set, thus impacting in tomato yield. Taken as a whole these results demonstrate that ascorbate biosynthetic pathway critically participates in tomato development and fruit production.
Subject(s)
Ascorbic Acid/biosynthesis , Fruit/enzymology , Fruit/growth & development , Galactose/metabolism , Guanosine Diphosphate/metabolism , Phosphoric Monoester Hydrolases/deficiency , Plant Proteins/metabolism , Solanum lycopersicum/enzymology , Biomass , Gases/metabolism , Solanum lycopersicum/growth & development , Mutation/genetics , Photosynthesis , Plant Leaves/metabolism , Principal Component AnalysisABSTRACT
Septins are GTP-binding proteins that will often spontaneously assemble into filaments. In some species, particularly budding yeast, it is well known that these are capable of associating with membranes in order to fulfill their cellular role as a component of the cytoskeleton. Different from other human septins, SEPT7 appears to be unique in that it is an essential component of all hetero-oligomeric complexes described to date. As a step towards understanding the molecular basis of filament assembly, here we present two high-resolution structures of the SEPT7 GTPase domain complexed with GDP. One of these reveals a previously unreported coordination for the magnesium ion involving four water molecules and only a tenuous connection to the protein. The higher resolution structures provide unambiguous insight into the interactions at the G-interface where a structural motif based on an antiparallel ß-bridge allows for the rationalization of why some septins show nucleotide-dependent ß-strand slippage and others do not.
Subject(s)
Cell Cycle Proteins/chemistry , GTP-Binding Proteins/chemistry , Septins/chemistry , Binding Sites , Crystallography, X-Ray , GTP Phosphohydrolases/metabolism , Guanosine Diphosphate/metabolism , Humans , Manganese/chemistry , Protein Conformation, beta-Strand , Protein Domains , Water/chemistryABSTRACT
In this paper, we analyze the relationship between adult height and early-life disease environment, proxied by the infant mortality rate (IMR) in the first year of life, using cohort-region level data for Chile for 1960-1989. IMRs show a remarkable reduction of 100 points per thousand over this thirty-year period, declining from 119.4 to 21.0 per thousand. We also document a 0.96 cm increase in height per decade.We find that the drop in IMRs observed among our cohorts explains almost all of the long-term trend in rising adult heights, and that per capita GDP does not appear to have any predictive power in this context. Results are robust in a variety of specifications, which include area and cohort dummies, an adjustment for internal migration, and urbanization rates. Our results point to the long-term effect of a public health policy.
Subject(s)
Body Height , Infant Mortality/trends , Adult , Chile/epidemiology , Cohort Studies , Environment , Female , Guanosine Diphosphate , Health Policy , Humans , Infant , Male , Public Policy , Socioeconomic Factors , UrbanizationABSTRACT
Objetivo: Avaliar a custo-efetividade e o impacto orçamentário da adição do omalizumabe (Oma) ao tratamento padrão [corticosteroide inalatório [CI] em dose média/alta e agente beta 2-agonista de longa ação (LABA)] no tratamento da asma alérgica grave não controlada, sob a perspectiva do sistema privado de saúde no Brasil. Método: Na análise econômica, utilizou-se o modelo de Markov baseado na evolução da asma, considerando os seguintes desfechos clínicos: exacerbações graves clinicamente significantes (EGCS) e exacerbações não graves clinicamente significantes (ECS), além de taxa de mortalidade por asma e uso de recursos e custos com o tratamento. Calculou-se razões de custo-efetividade incremental (RCEI) e o impacto orçamentário, com base em dados da saúde suplementar sobre população elegível e horizonte de 5 anos. Resultados: A análise de custoefetividade realizada mostrou que o tratamento com Oma teve maior benefício, se comparado ao tratamento padrão, e gerou uma RCEI de R$ 60.293,00 por ano de vida salvo, que é três vezes inferior ao produto interno bruto (PIB) per capita no Brasil. A análise de sensibilidade, para avaliar o impacto da incerteza dos parâmetros sobre o resultado encontrado, demonstrou que os resultados permanecem estáveis a favor do Oma. A análise do impacto orçamentário apontou um custo por beneficiário de R$ 0,40 no primeiro ano, chegando a R$ 1,80 no quinto ano. Conclusão: A análise econômica demonstrou que a combinação do tratamento com Oma com o padrão para asma alérgica grave não controlada é custo-efetivo no cenário nacional, e a sua incorporação na saúde suplementar é viável.
Objective: To evaluate the cost-effectiveness and budgetary impact of adding omalizumab (Oma) to standard treatment (medium/highdose inhaled corticosteroid [ICS] and long-acting beta 2-agonist [LABA]) in the treatment of severe uncontrolled allergic asthma, from the perspective of the Brazilian private health system (PHS). Method: In economic analysis, the Markov model was used based on the progression of asthma considering the following clinical outcomes: clinically significant severe exacerbations (CSSE) and clinically significant non-severe exacerbations (CSNSE), as well as asthma mortality rate and use of resources and costs of treatment. Incremental cost-effectiveness ratios (ICER) and budgetary impact were calculated based on PHS data regarding eligible population and 5-year horizon scanning. Results: The cost-effectiveness analysis showed that treatment with Oma provided greater benefit compared to the standard treatment and generated an ICER of BRL 60,293 per life-years saved, corresponding to less than three times the gross domestic product (GDP) per capita in Brazil. A sensitivity analysis to evaluate the impact of parameter uncertainty showed that results still favor Oma. The budget impact analysis showed a cost of BRL 0.40 per recipient in the first year, reaching BRL 1.80 in the fifth year. Conclusion: The economic analysis demonstrated that combined Oma treatment and standard treatment of uncontrolled severe allergic asthma is cost-effective in the national setting and its incorporation into PHS is feasible.
Subject(s)
Humans , Asthma , Adrenal Cortex Hormones , Supplemental Health , Cost-Effectiveness Analysis , Omalizumab , Analysis of the Budgetary Impact of Therapeutic Advances , Patients , Therapeutics , Effectiveness , Health Systems , Cost-Benefit Analysis , Dosage , Gross Domestic Product , Guanosine Diphosphate , Health ResourcesABSTRACT
Objetivos: Determinar a relação custo-efetividade da adição do omalizumabe (Oma) no tratamento da urticária crônica espontânea (UCE) refratária aos tratamentos convencionais, bem como o impacto orçamentário no contexto da saúde suplementar (SS) no Brasil. Métodos: Na análise econômica, utilizou-se o modelo de Markov baseado no Urticaria Activity Score for 7 days (UAS7), considerando- se os desfechos clínicos: anos de vida salvos com doença controlada (UAS7 = 0 ou UAS7 ≤ 6), e anos de vida ajustados à qualidade (QALY). Três razões de custo-efetividade incremental (RCEI) foram calculadas. O impacto orçamentário foi calculado com base em dados da SS, população elegível e o horizonte de 5 anos. Resultados: As RCEI calculadas para o desfecho anos de vida salvos com doença controlada nos horizontes de 3 e 5 anos foram R$ 108.935,42 e R$ 166.977,29, respectivamente. O impacto orçamentário, do primeiro ao quinto ano, da incorporação do Oma à SS para o tratamento de pacientes com UCE refratária variou entre R$ 65 milhões e R$ 157 milhões, que equivaleria a R$ 1,38/assistido no primeiro ano incorporação. Sendo assim, ao analisar os custos adicionais por desfecho adicional salvo, nota-se que a RCEI também se mostrou menor que três vezes o PIB per capita no Brasil, podendo-se dizer que o tratamento com Oma é custo-efetivo em comparação ao tratamento atual também neste desfecho. Conclusão: A análise econômica demonstrou que o tratamento com Oma da UCE refratária ao tratamento com antihistamínicos H1 em doses elevadas é custo-efetivo no cenário nacional, e a sua incorporação na SS é viável.
Objectives: To determine the cost-effectiveness of adding omalizumab (Oma) to the treatment of chronic spontaneous urticaria (CSU) refractory to conventional treatments, as well as its budgetary impact in the context of private health insurance (PHI) in Brazil. Methods: In the economic analysis, the Markov model based on the Urticaria Activity Score over 7 days (UAS7) was used considering the following clinical outcomes: life years saved with controlled disease (UAS7 = 0 or UAS7 ≤ 6) and quality-adjusted life years (QALYs). Three incremental cost-effectiveness ratios (ICERs) were calculated. The budgetary impact was calculated using PHI data, eligible population, and 5-year horizon. Results: The estimated ICERs for life years saved with controlled disease in 3- and 5-year horizons were R$ 108,935.42 and R$ 166,977.29, respectively. The budgetary impact from the first to the fifth year of the incorporation of Oma into PHI for the treatment of patients with refractory CSU ranged from R$ 65 million to R$ 157 million, equivalent to R$ 1.38/assisted patient in the first year of incorporation. When additional costs were analyzed per additional outcome saved, ICER was shown to be less than three times the GDP per capita in Brazil. Thus, Oma is cost-effective compared to the current treatment in this outcome as well. Conclusion: The economic analysis demonstrated that treatment with Oma of CSU refractory to the treatment with H1 antihistamines in high doses is cost-effective in the Brazilian setting and its incorporation into the PHI system is feasible.
Subject(s)
Humans , Supplemental Health , Cost-Effectiveness Analysis , Omalizumab , Analysis of the Budgetary Impact of Therapeutic Advances , Chronic Urticaria , Histamine Antagonists , Patients , Therapeutics , Effectiveness , Cost-Benefit Analysis , Quality-Adjusted Life Years , Gross Domestic Product , Guanosine Diphosphate , MethodsABSTRACT
Septins are GTP-binding proteins that are highly conserved among eukaryotes and which are usually membrane-associated. They have been linked to several critical cellular functions such as exocytosis and ciliogenesis, but little mechanistic detail is known. Their assembly into filaments and membrane binding properties are incompletely understood and that is specially so for non-human septins where such information would offer therapeutic potential. In this study we use Schistosoma mansoni, exhibiting just four septin genes, as a simpler model for characterizing the septin structure and organization. We show that the biochemical and biophysical proprieties of its SmSEPT5 and SmSEPT10 septins are consistent with their human counterparts of subgroups SEPT2 and SEPT6, respectively. By succeeding to isolate stable constructs comprising distinct domains of SmSEPT5 and SmSEPT10 we were able to infer the influence of terminal interfaces in the oligomerization and membrane binding properties. For example, both proteins tended to form oligomers interacting by the N- and C-terminal interfaces in a nucleotide independent fashion but form heterodimers via the G interface, which are nucleotide dependent. Furthermore, we report for the first time that it is the C-terminus of SmSETP10, rather than the N-terminal polybasic region found in other septins, that mediates its binding to liposomes. Upon binding we observe formation of discrete lipo-protein clusters and higher order septin structures, making our system an exciting model to study interactions of septins with biological membranes.
Subject(s)
Guanosine Triphosphate/metabolism , Helminth Proteins/metabolism , Schistosoma mansoni/metabolism , Septins/metabolism , Animals , Binding Sites/genetics , Biophysical Phenomena , Circular Dichroism , Guanosine Diphosphate/metabolism , Helminth Proteins/chemistry , Helminth Proteins/genetics , Hydrogen-Ion Concentration , Hydrolysis , Liposomes/chemistry , Liposomes/metabolism , Multigene Family , Protein Binding , Protein Multimerization , Schistosoma mansoni/genetics , Septins/chemistry , Septins/genetics , Spectrometry, Fluorescence , Temperature , ThermodynamicsABSTRACT
The protozoan parasite Leishmania amazonensis is the etiological agent of cutaneous leishmaniasis. During its life cycle, the flagellated metacyclic promastigote forms are transmitted to vertebrate hosts by sandfly bites, and they develop into amastigotes inside macrophages, where they multiply. L. amazonensis possesses a bifunctional enzyme, called 3'-nucleotidase/nuclease (3'NT/NU), which is able to hydrolyze extracellular 3'-monophosphorylated nucleosides and nucleic acids. 3'NT/NU plays an important role in the generation of extracellular adenosine and has been described as a key enzyme in the acquisition of purines by trypanosomatids. Furthermore, it has been observed that 3'NT/NU also plays a valuable role in the establishment of parasitic infection. In this context, this study aimed to investigate the modulation of the 3'-nucleotidase (3'NT) activity of L. amazonensis by several nucleotides. It was observed that 3'NT activity is inhibited by micromolar concentrations of guanosine and guanine nucleotides. The inhibition promoted by 5'-GMP on the 3'NT activity of L. amazonensis is reversible and uncompetitive because the addition of the inhibitor decreased the kinetic parameters Km and Vmax. Finally, we found that the addition of 5'-GMP is able to reverse the stimulation promoted by 3'-AMP in a macrophage-parasite interaction assay. The determination of compounds that can inhibit the 3'NT activity of Leishmania is very important because this enzyme does not occur in mammals, making it a potential therapeutic target.
Subject(s)
Guanosine Diphosphate/pharmacology , Guanosine Monophosphate/pharmacology , Guanosine Triphosphate/pharmacology , Leishmania mexicana/enzymology , Nucleotidases/antagonists & inhibitors , Animals , Kinetics , Leishmania mexicana/drug effects , Macrophages/parasitology , Mice , Nucleotidases/metabolism , RAW 264.7 CellsABSTRACT
Neurons are highly polarized cells that contain specialized subcellular domains involved in information transmission in the nervous system. Specifically, the somatodendritic compartment receives neuronal inputs while the axons convey information through the synapse. The establishment of asymmetric domains requires a specific delivery of components, including organelles, proteins, and membrane. The Rab family of small GTPases plays an essential role in membrane trafficking. Signaling cascades triggered by extrinsic and intrinsic factors tightly regulate Rab functions in cells, with Rab protein activation depending on GDP/GTP binding to establish a binary mode of action. This review summarizes the contributions of several Rab family members involved in trans-Golgi, early/late endosomes, and recycling endosomes during neurite development and axonal outgrowth. The regulation of some Rabs by guanine exchanging factors and GTPase activating proteins will also be addressed. Finally, discussion will be provided on how specific effector-mediated Rab activation modifies several molecules essential to neuronal differentiation. © 2016 Wiley Periodicals, Inc.
Subject(s)
Actins/metabolism , Axons/metabolism , Neurites/metabolism , Signal Transduction , rab GTP-Binding Proteins/metabolism , Cytidine Triphosphate/metabolism , Endosomes/metabolism , Guanosine Diphosphate/metabolism , Humans , trans-Golgi Network/metabolismABSTRACT
Labor pain has been reported as a severe pain and can be considered as a model of acute visceral pain. It is well known that extracellular purines have an important role in pain signaling in the central nervous system. This study analyzes the relationship between extracellular purines and pain perception during active labor. A prospective observational study was performed. Cerebrospinal fluid (CSF) levels of the purines and their metabolites were compared between women at term pregnancy with labor pain (n = 49) and without labor pain (Caesarian section; n = 47). Control groups (healthy men and women without chronic or acute pain-n = 40 and 32, respectively) were also investigated. The CSF levels of adenosine were significantly lower in the labor pain group (P = 0.026) and negatively correlated with pain intensity measured by a visual analogue scale (r = -0.48, P = 0.0005). Interestingly, CSF levels of uric acid were significantly higher in healthy men as compared to women. Additionally, pregnant women showed increased CSF levels of ADP, GDP, adenosine and guanosine and reduced CSF levels of AMP, GTP, and uric acid as compared to non-pregnant women (P < 0.05). These findings suggest that purines, in special the nucleoside adenosine, are associated with pregnancy and labor pain.
Subject(s)
Labor Pain/cerebrospinal fluid , Labor, Obstetric/cerebrospinal fluid , Purines/cerebrospinal fluid , Adenosine/cerebrospinal fluid , Adenosine Diphosphate/cerebrospinal fluid , Adult , Cesarean Section , Female , Guanosine/cerebrospinal fluid , Guanosine Diphosphate/cerebrospinal fluid , Humans , Male , Pain Measurement , Pain Perception , Pregnancy , Prospective StudiesABSTRACT
Enhanced mitochondrial generation of oxidants, including hydrogen peroxide (H2O2), is related to a large number of pathological conditions, including diet-induced obesity and steatohepatosis. Indeed, we have previously shown that high fat diets increase the generation of H2O2 in liver mitochondria energized by activated fatty acids. Here, we further study fatty-acid induced H2O2 release in liver mitochondria, and determine the characteristics that regulate it. We find that this production of H2O2 is independent of mitochondrial inner membrane integrity and insensitive to purine nucleotides. On the other hand, palmitate-induced H2O2 production is strongly enhanced by high fat diets and is pH-sensitive, with a peak at a matrix pH of ~8.5. Using recombinantly expressed human very long chain acyl-CoA dehydrogenase, we are able to demonstrate that palmitate-induced H2O2 release may be ascribed to the activity of this enzyme alone, acting as an oxidase. Our results add to a number of findings indicating that sources outside of the electron transport chain can generate significant, physiopathologically relevant, amounts of oxidants in mitochondria.
Subject(s)
Acyl-CoA Dehydrogenase, Long-Chain/metabolism , Diet, High-Fat , Hydrogen Peroxide/metabolism , Mitochondria, Liver/metabolism , Acyl-CoA Dehydrogenase, Long-Chain/genetics , Adenosine Diphosphate/pharmacology , Adenosine Monophosphate/pharmacology , Adenosine Triphosphate/pharmacology , Animals , Enzyme Assays , Female , Guanosine Diphosphate/pharmacology , Guanosine Triphosphate/pharmacology , Hydrogen-Ion Concentration , Kinetics , Mice , Mitochondria, Liver/drug effects , Oxidation-Reduction , Palmitic Acid/pharmacology , Recombinant Proteins/genetics , Recombinant Proteins/metabolismABSTRACT
Septins are filament-forming GTP-binding proteins involved in important cellular events, such as cytokinesis, barrier formation, and membrane remodeling. Here, we present two crystal structures of the GTPase domain of a Schistosoma mansoni septin (SmSEPT10), one bound to GDP and the other to GTP. The structures have been solved at an unprecedented resolution for septins (1.93 and 2.1 Å, respectively), which has allowed for unambiguous structural assignment of regions previously poorly defined. Consequently, we provide a reliable model for functional interpretation and a solid foundation for future structural studies. Upon comparing the two complexes, we observe for the first time the phenomenon of a strand slippage in septins. Such slippage generates a front-back communication mechanism between the G and NC interfaces. These data provide a novel mechanistic framework for the influence of nucleotide binding to the GTPase domain, opening new possibilities for the study of the dynamics of septin filaments.
Subject(s)
Schistosoma mansoni/chemistry , Septins/chemistry , Animals , Binding Sites , Calorimetry , Catalysis , Cell Membrane/metabolism , Crystallography, X-Ray , Escherichia coli/metabolism , GTP Phosphohydrolases/chemistry , Guanosine Diphosphate/chemistry , Guanosine Triphosphate/chemistry , Hydrolysis , Magnesium/chemistry , Magnetic Resonance Spectroscopy , Nucleotides/chemistry , Protein Structure, Secondary , Protein Structure, Tertiary , Recombinant Proteins/chemistry , Thermodynamics , Water/chemistryABSTRACT
TASK-2 (K2P5.1) is a background K(+) channel opened by extra- or intracellular alkalinisation that plays a role in renal bicarbonate handling, central chemoreception and cell volume regulation. Here, we present results that suggest that TASK-2 is also modulated by Gßγ subunits of heterotrimeric G protein. TASK-2 was strongly inhibited when GTP-γ-S was used as a replacement for intracellular GTP. No inhibition was present using GDP-ß-S instead. Purified Gßγ introduced intracellularly also inhibited TASK-2 independently of whether GTP or GDP-ß-S was present. The effects of GTP-γ-S and Gßγ subunits were abolished by neutralisation of TASK-2 C terminus double lysine residues K257-K258 or K296-K297. Use of membrane yeast two hybrid (MYTH) experiments and immunoprecipitation assays using tagged proteins gave evidence for a physical interaction between Gß1 and Gß2 subunits and TASK-2, in agreement with expression of these subunits in proximal tubule cells. Co-immunoprecipitation was impeded by mutating C terminus K257-K258 (but not K296-K297) to alanines. Gating by extra- or intracellular pH was unaltered in GTP-γ-S-insensitive TASK-2-K257A-K258A mutant. Shrinking TASK-2-expressing cells in hypertonic solution decreased the current to 36 % of its initial value. The same manoeuvre had a significantly diminished effect on TASK-2-K257A-K258A- or TASK-2-K296-K297-expressing cells, or in cells containing intracellular GDP-ß-S. Our data are compatible with the concept that TASK-2 channels are modulated by Gßγ subunits of heterotrimeric G protein. We propose that this modulation is a novel way in which TASK-2 can be tuned to its physiological functions.
Subject(s)
GTP-Binding Protein beta Subunits/metabolism , GTP-Binding Protein gamma Subunits/metabolism , Heterotrimeric GTP-Binding Proteins/metabolism , Potassium Channels, Tandem Pore Domain/metabolism , Amino Acid Sequence , Animals , GTP-Binding Protein beta Subunits/genetics , GTP-Binding Protein gamma Subunits/genetics , Guanosine Diphosphate/analogs & derivatives , Guanosine Diphosphate/pharmacology , HEK293 Cells , Heterotrimeric GTP-Binding Proteins/genetics , Humans , Ion Channel Gating/drug effects , Mice , Thionucleotides/pharmacology , Two-Hybrid System TechniquesABSTRACT
The UCP1 [first UCP (uncoupling protein)] that is found in the mitochondria of brown adipocytes [BAT (brown adipose tissue)] regulates the heat production, a process linked to non-shivering thermogenesis. The activity of UCP1 is modulated by GDP and fatty acids. In this report, we demonstrate that respiration and heat released by BAT mitochondria vary depending on the respiratory substrate utilized and the coupling state of the mitochondria. It has already been established that, in the presence of pyruvate/malate, BAT mitochondria are coupled by faf-BSA (fatty-acid-free BSA) and GDP, leading to an increase in ATP synthesis and mitochondrial membrane potential along with simultaneous decreases in both the rates of respiration and heat production. Oleate restores the uncoupled state, inhibiting ATP synthesis and increasing the rates of both respiration and heat production. We now show that in the presence of succinate: (i) the rates of uncoupled mitochondria respiration and heat production are five times slower than in the presence of pyruvate/malate; (ii) faf-BSA and GDP accelerate heat and respiration as a result and, in coupled mitochondria, these two rates are accelerated compared with pyruvate/malate; (iii) in spite of the differences in respiration and heat production noted with the two substrates, the membrane potential and the ATP synthesized were the same; and (iv) oleate promoted a decrease in heat production and respiration in coupled mitochondria, an effect different from that observed using pyruvate/malate. These effects are not related to the production of ROS (reactive oxygen species). We suggest that succinate could stimulate a new route to heat production in BAT mitochondria.
Subject(s)
Adipose Tissue, Brown/metabolism , Fatty Acids/metabolism , Guanosine Diphosphate/metabolism , Mitochondria/metabolism , Adenosine Triphosphate/biosynthesis , Animals , Cell Respiration/drug effects , Fatty Acids/pharmacology , Hydrogen Peroxide/metabolism , Malates/metabolism , Malates/pharmacology , Male , Oleic Acid/metabolism , Oleic Acid/pharmacology , Pyruvic Acid/metabolism , Pyruvic Acid/pharmacology , Rats , Rats, Wistar , Rotenone/pharmacology , Succinic Acid/metabolism , Succinic Acid/pharmacology , Thermogenesis/drug effects , Uncoupling Agents/pharmacologyABSTRACT
Ethanol is a widely consumed drug that acts on the central nervous system (CNS), modifying several signal transduction pathways activated by hormones and neurotransmitters. The zebrafish is an experimental model for the study of human diseases and the use of this species in biochemical and behavioral studies on alcoholism and alcohol-dependence has increased recently. However, there are no data concerning the effects of chronic ethanol exposure on the purinergic system, where extracellular nucleotides act as signaling molecules. Purinergic signaling is controlled by a group of enzymes named ectonucleotidases, which include NTPDases and ecto-5'-nucleotidase already characterized in zebrafish brain. The aim of this study was to evaluate nucleotide hydrolysis by NTPDases and ecto-5'-nucleotidase after long-term ethanol exposure. Additionally, the gene expression patterns of NTPDases1-3 and 5'-nucleotidase were determined. Animals were exposed to 0.5% ethanol for 7, 14, and 28 days. There were no significant changes in ATP and GTP hydrolysis after all treatments. However, a decrease in ADP (46% and 34%) and GDP (48% and 36%) hydrolysis was verified after 7 and 14 days, respectively. After 7 and 14 days of ethanol exposure, a significant decrease in AMP hydrolysis (48% and 36%) was also observed, whereas GMP hydrolysis was inhibited only after 7 days (46%). NTPDase2_mv and NTPDase3 mRNA transcript levels decreased after 7 and 14 days, respectively. In contrast, ethanol increased NTPDase1, NTPDase2_mq, and NTPDase3 transcript levels after 28 days of exposure. NTPDase2_mg and 5'-nucleotidase gene expression was not altered. Therefore, the ectonucleotidase pathway may be a target of chronic ethanol toxicity and the regulation of purinergic system could play a key role in the neurochemical mechanisms underlying the effects of ethanol on the CNS.
Subject(s)
5'-Nucleotidase/metabolism , Adenosine Triphosphatases/metabolism , Adenosine Triphosphate/metabolism , Brain/drug effects , Ethanol/toxicity , Guanosine Triphosphate/metabolism , Zebrafish Proteins/metabolism , Zebrafish/metabolism , 5'-Nucleotidase/genetics , Adenosine Diphosphate/metabolism , Adenosine Triphosphatases/genetics , Animals , Brain/enzymology , Female , Gene Expression Regulation, Enzymologic/drug effects , Guanosine Diphosphate/metabolism , Hydrolysis , Male , RNA, Messenger/metabolism , Time Factors , Zebrafish/genetics , Zebrafish Proteins/geneticsABSTRACT
Seven-transmembrane receptors mediate diverse skeletal muscle responses for a wide variety of stimuli, via activation of heterotrimeric G-proteins. Herein we evaluate the expression and activation of rat diaphragm or cultured skeletal muscle G-proteins using [(35)S]GTPγS. Total membrane Gα subunit content was 4-7 times higher in rat primary cultured myotubes and L6 cell line than in diaphragm (32.6±1.2fmol/mg protein) and 7-27% of them were in the active conformational state. Immunoprecipitation assay showed equal expression of diaphragm Gαs, Gαq and Gαi/o. Addition of GDP allowed the measurement of G-protein activation by different GPCR, including adrenoceptor, adenosine, melatonin and muscarinic receptors. Diaphragm denervation resulted in a marked increase in both total and active state G-protein levels. Together, the results show that [(35)S]GTPγS binding assay is a sensitive and valuable method to evaluate GPCR activity in skeletal muscle cells, which is of particular interest for pharmacological analysis of drugs with potential use in the management of respiratory muscle failure.
Subject(s)
Diaphragm/enzymology , Heterotrimeric GTP-Binding Proteins/physiology , Animals , Cells, Cultured , Diaphragm/drug effects , Diaphragm/innervation , Guanosine Diphosphate/pharmacology , Male , Muscarinic Agonists/pharmacology , Oxotremorine/pharmacology , Phrenic Nerve/drug effects , Phrenic Nerve/physiology , Rats , Rats, Wistar , Receptors, Adrenergic/drug effects , Receptors, Adrenergic/physiology , Receptors, G-Protein-Coupled/drug effects , Receptors, G-Protein-Coupled/physiology , Receptors, Melatonin/drug effects , Receptors, Melatonin/physiology , Receptors, Muscarinic/drug effects , Receptors, Muscarinic/physiology , Receptors, Purinergic P1/drug effects , Receptors, Purinergic P1/physiologyABSTRACT
Uncoupling proteins (UCPs) are mitochondrial carriers distributed throughout the eukaryotic kingdoms. While genes coding for UCPs have been identified in plants and animals, evidences for the presence of UCPs in fungi and protozoa are only functional. Here, it is reported that in the yeast Yarrowia lipolytica there is a fatty acid-promoted and GDP-sensitive uncoupling activity indicating the presence of a UCP. The uncoupling activity is higher in the stationary phase than in the mid-log growth phase. The in silico search on the Y. lipolytica genome led to the selection of two genes with the highest homology to the UCP family, XM_503525 and XM_500457. By phylogenetic analysis, XP_503525 was predicted to be an oxaloacetate carrier while XP_500457 would be a dicarboxylate carrier. Each of these two genes was cloned and heterologously expressed in Saccharomyces cerevisiae and the resulting phenotype was analyzed. The transport activity of the two gene products confirmed the phylogenetic predictions. In addition, only mitochondria isolated from yeasts expressing XP_503525 showed bioenergetic properties characteristic of a UCP: the proton conductance was increased by linoleic acid and inhibited by GDP. It is concluded that the XM_503525 gene from Y. lipolytica encodes for an oxaloacetate carrier although, remarkably, it also displays an uncoupling activity stimulated by fatty acids and inhibited by nucleotides.
Subject(s)
Mitochondria/metabolism , Oxygen Consumption , Yarrowia/metabolism , Biological Transport , Fatty Acids/pharmacology , Guanosine Diphosphate/metabolism , Ion Channels/metabolism , Membrane Potentials/physiology , Mitochondria/physiology , Mitochondrial Proteins/metabolism , Phylogeny , Succinates/metabolism , Sulfates/metabolism , Uncoupling Protein 1 , Vancomycin/pharmacologyABSTRACT
It has been suggested that voltage-dependent G protein modulation of Ca(V)2.2 channels is carried out at closed states of the channel. Our purpose was to estimate the number of gating charges of Ca(V)2.2 channel in control and G protein-modulated conditions. By using a Cole-Moore protocol we observed a significant delay in Ca(V)2.2 channel activation according to a transit of the channel through a series of closed states before channel opening. If G protein voltage-dependent modulation were carried out at these closed states, then we would have expected a greater Cole-Moore lag in the presence of a neurotransmitter. This prediction was confirmed for noradrenaline, while no change was observed in the presence of angiotensin II, a voltage-insensitive G protein modulator. We used the limiting slope method for calculation of the gating charge per channel. Effective charge z was 6.32+/-0.65 for Ca(V)2.2 channels in unregulated conditions, while GTPgammaS reduced elementary charge by approximately 4 e(0). Accordingly, increased concentration of noradrenaline induced a gradual decrease on z, indicating that this decrement was due to a G protein voltage-sensitive modulation. This paper shows for the first time a significant and reversible decrease in charge transfer of Ca(V)2.2 channels under G protein modulation, which might depend on the activated G protein inhibitory pathway.