Initial rates of pyruvate transport in mitochondria determined by an "inhibitor-stop" technique.
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ABSTRACT:
SUBMITTER: Titheradge MA
PROVIDER: S-EPMC1165770 | biostudies-other | 1975 Sep
REPOSITORIES: biostudies-other
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Project description:We have previously demonstrated that the overexpression of enzymes involved in the production of pyruvate, enolase 2 (Eno2) and D-lactate dehydrogenase (Dld3) renders yeast highly sensitive to methylmercury and that the promotion of intracellular pyruvate synthesis may be involved in intensifying the toxicity of methylmercury. In the present study, we showed that the addition of pyruvate to culture media in non-toxic concentrations significantly enhanced the sensitivity of yeast and human neuroblastoma cells to methylmercury. The results also suggested that methylmercury promoted the transport of pyruvate into mitochondria and that the increased pyruvate concentrations in mitochondria were involved in intensifying the toxicity of methylmercury without pyruvate being converted to acetyl-CoA. Furthermore, in human neuroblastoma cells, methylmercury treatment alone decreased the mitochondrial membrane potential, and the addition of pyruvate led to a further significant decrease. In addition, treatment with N-acetylcysteine (an antioxidant) significantly alleviated the toxicity of methylmercury and significantly inhibited the intensification of methylmercury toxicity by pyruvate. Based on these data, we hypothesize that methylmercury exerts its toxicity by raising the level of pyruvate in mitochondria and that mitochondrial dysfunction and increased levels of reactive oxygen species are involved in the action of pyruvate.
| S-EPMC4761912 | biostudies-literature
Project description:1. Mitochondria isolated from the thermogenic spadices of Arum maculatum and Sauromatum guttatum plants oxidized external NADH, succinate, citrate, malate, 2-oxoglutarate and pyruvate without the need to add exogenous cofactors. 2. Oxidation of substrates was virtually all via the alternative oxidase, the cytochrome pathway constituting only 10-20% of the total activity, depending on the stage of spadix development. 3. During later stages of spadix development, pyruvate oxidation was enhanced by the addition of aspartate. This was caused by acetyl-CoA condensing with oxaloacetate, produced from pyruvate/aspartate transamination, and so decreasing feedback inhibition of pyruvate dehydrogenase. 4. Pyruvate oxidation was inhibited by the long-chain acid maleimides AM5-11, but not by those with shorter polymethylene side groups, AM1-4. 5. The alpha-cyanocinnamate derivatives UK5099 [alpha-cyano-beta-(1-phenylindol-3-yl)acrylate] and CHCA [alpha-cyano-4-hydroxycinnamate] inhibited pyruvate-dependent O2 consumption and the carrier-mediated uptake of pyruvate across the mitochondrial inner membrane. Characteristics of non-competitive inhibition were observed for CHCA, whereas for UK5099 the results were more complex, suggesting a very low rate of dissociation of the inhibitor-carrier complex. 6. A comparison of the values of Vmax. and Km for oxidation and transport suggested that it was the latter which controls the overall rate of pyruvate oxidation by mitochondria from both tissues.
| S-EPMC1148428 | biostudies-other
Project description:The genetic code that specifies the identity of amino acids incorporated into proteins during protein synthesis is almost universally conserved. Mitochondrial translation deviates from the standard genetic code which includes the reassignment of two arginine codons into stop codons {Jukes, 1993 #438}. Translation termination at these non-canonical stop codons requires a protein factor to release the newly synthesized polypeptide chain, however, the identity of this factor is not known currently{Nadler, 2021 #406}. Here, we used gene editing and ribo-profiling in combination with cryo-electron microscopy to establish that the unusual mitochondrial release factor 1 (mtRF1) detects the non-canonical stop codons. We show that loss of mtRF1 leads to stalling of mitochondrial ribosomes on non-canonical stop codons and consequent reduced translation of cytochrome C oxidase subunit 1 that results in decreased mitochondrial respiration. We show that binding of mtRF1 to the decoding center of the ribosome stabilizes a highly unusual distortion in the mRNA conformation and that the ribosomal RNA importantly participates in the specific recognition of the non-canonical stop codons.
2023-03-21 | GSE216979 | GEO
Project description:BackgroundThe aim of this study is to compare the results of stop-start technique with stop-start technique together with sphincter control training applied in the treatment of premature ejaculation.MethodsThis research was conducted as a pre-test post-test quasi-experimental study. The sample of the study consisted of 80 men. The study was conducted on men who applied to the urology outpatient clinic of LIV Hospital, a prıvate hospital, in Gaziantep, Turkey, between 01 October 2021 and 01 March 2022. "Personal Information Form", "Intravaginal Ejaculation Latency Time (IELT)", "Fold Increase Intravaginal Ejaculation Latency Time (F-IELT)" "Premature Ejaculation Diagnostic Tool (PEDT) Questionnaire" and "Arabic Index Premature Ejaculation (AIPE)" were used as the data collection tools. Behavioral therapy, consisting of a total of 6 sessions, was applied once every two weeks, with each session lasting for 45 minutes. After 3rd and 6th months from the beginning of the application, the data collection tools were applied again. "Stop-Start Technique (Group A)" and "Stop-Start Technique and Sphincter Control Training (Group B)" were used in the treatment.ResultsIn both groups, the IELT and AIPE values after 3rd and 6th months from the beginning of the application were statistically higher than those obtained before (p<0.05). IELT and AIPE values increased more in Group B than Group A (p<0.05). F-IELT values after 6th months from the beginning of the application were found to be statistically significant with a low level of effect size than those obtained before (p<0.05, Cohen's d = 0.027). In both groups, the PEDT values in the 3rd and 6th months after the application were statistically lower than those seen before (p<0.05). PEDT value decreased more in Group B than Group A (p<0.05). The differences between the two groups' IELT (Cohen's d = 0.011), AIPE (Cohen's d = 0.044), and PEDT (Cohen's d = 0.066) values in the 3rd month after the application and IELT (Cohen's d = 0.025), AIPE (Cohen's d = 0.048), and PEDT (Cohen's d = 0.024) values in the 6th month after the application were found to be clinically weak.ConclusionsIt was determined that the stop-start technique given to men with premature ejaculation increased the time spent in the vagina and eliminated the problem of premature ejaculation. It was determined that the stop-start technique in combination with sphincter control training were more effective than the stop-start technique alone.
| S-EPMC10414676 | biostudies-literature
Project description:Bacteria use trans-translation and the alternative rescue factors ArfA (P36675) and ArfB (Q9A8Y3) to hydrolyze peptidyl-tRNA on ribosomes that stall near the 3' end of an mRNA during protein synthesis. The eukaryotic protein ICT1 (Q14197) is homologous to ArfB. In vitro ribosome rescue assays of human ICT1 and Caulobacter crescentus ArfB showed that these proteins have the same activity and substrate specificity. Both ArfB and ICT1 hydrolyze peptidyl-tRNA on nonstop ribosomes or ribosomes stalled with ≤6 nucleotides extending past the A site, but are unable to hydrolyze peptidyl-tRNA when the mRNA extends ≥14 nucleotides past the A site. ICT1 provided sufficient ribosome rescue activity to support viability in C. crescentus cells that lacked both trans-translation and ArfB. Likewise, expression of ArfB protected human cells from death when ICT1 was silenced with siRNA. These data indicate that ArfB and ICT1 are functionally interchangeable, and demonstrate that ICT1 is a ribosome rescue factor. Because ICT1 is essential in human cells, these results suggest that ribosome rescue activity in mitochondria is required in humans.
| S-EPMC4814080 | biostudies-literature
Project description:The abundant RNA modification pseudouridine (Ψ) has been mapped transcriptome-wide by chemically modifying pseudouridines with carbodiimide and detecting the resulting reverse transcription stops in high-throughput sequencing. However, these methods have limited sensitivity and specificity, in part due to the use of reverse transcription stops. We sought to use mutations rather than just stops in sequencing data to identify pseudouridine sites. Here, we identify reverse transcription conditions that allow read-through of carbodiimide-modified pseudouridine (CMC-Ψ), and we show that pseudouridines in carbodiimide-treated human ribosomal RNA have context-dependent mutation and stop rates in high-throughput sequencing libraries prepared under these conditions. Furthermore, accounting for the context-dependence of mutation and stop rates can enhance the detection of pseudouridine sites. Similar approaches could contribute to the sequencing-based detection of many RNA modifications.
2018-05-07 | GSE110247 | GEO
Project description:Attempts to restore the anatomical footprint during rotator cuff repair for retracted, relatively immobile tears can be difficult. In some cases, it can lead to excessive tension of the repair. Previous studies have noted improved clinical outcomes when repair tension is not excessive, and medialization of the anatomical footprint has been suggested as a technique that can help surgeons repair large, retracted tears without excessive tension and achieve improved clinical outcomes. Of note, excessive tension when restoring the rotator cuff tendon to the anatomical footprint is not limited to large, retracted tears. In some cases, restoring small- and medium-sized tears to the anatomical footprint also can lead to excessive tension. Therefore, it is not uncommon for the authors to employ some degree of footprint medialization even for repair of small- or medium-sized tears if repair to the anatomical footprint will lead to excess tension. The purpose of this article and video demonstration is to provide instruction for a reproducible rotator cuff technique using a medialized single-row rip-stop construct combined with convergence. Technique Video Video 1 An arthroscopic rotator cuff repair with a medialized rip-stop convergence technique is shown for a left shoulder in the beach-chair position, as viewed through a posterior portal and lateral portal with lateral subacromial viewing perspective. Techniques and advantages of medialization are demonstrated with emphasis on creating an opportunity to perform a double-row repair when one otherwise would not be feasible due to the entire footprint’s medial shift.
| S-EPMC10466296 | biostudies-literature
Project description:Excellent estimations of initial rates can be obtained from plots of delta P/t versus product formed (where P is the instantaneous concentration of the product). delta P/t is the chord from P0,t0 to P,t on an ordinary P-versus-t plot. When the chord is plotted as a function of product, the intercept at P0 of the resulting curve is necessarily dP/dt0. This curve approximates to a straight line extremely closely in all cases tested thus far. If delta P/t versus product is calculated from the integrated rate equation for a first-order reaction, and if a straight line is fitted through points representing the first 50% of the reaction, the discrepancy between the true initial rate and dP/dt0 estimated from the plot is 0.68%. For the most common form of the integrated rate equation for catalysed reactions the discrepancy varies between 0 and 0.90%. Because of the complexities of the integrated rate equations, catalysed second-order reactions have not been evaluated directly; uncatalysed reactions have been done instead. For a reaction with one reactant and two products, the discrepancy varies from 0.68 to 2.02%. For two reactants and one product, it varies from 0 to 0.68%; for two and two, 0 to 2.02%. The larger discrepancies occur only when unfavourable equilibrium constants are being overcome by the initial conditions.
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Project description:Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep, intense circuit activity, or dietary restrictions, posing significant metabolic stress. Here, we demonstrate that the mammalian brain utilizes pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability within a neuron and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation which in turn modulates mitochondrial pyruvate uptake. Importantly, our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in synaptic transmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval, functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of synaptic transmission in hippocampal terminals.
| S-EPMC10983914 | biostudies-literature
Project description:The transporter which uptakes pyruvate into the mitochondria during pyruvate oxidation, called the Mitochondrial Pyruvate Carrier (MPC), was only recently identified. While the MPC has been studied in a variety of cell types, including cancer cells and stem cells, very little is known about the importance of MPC in immune cells. Here, we delete MPC from hematopoietic cells and measure its impact on T cell gene expression.
2020-04-27 | GSE122711 | GEO