scholarly journals Metabolic evidence for distinct pyruvate pools inside plant mitochondria

2021 ◽  
Author(s):  
Xuyen Le ◽  
Chun Pong Lee ◽  
Dario Monachello ◽  
A. Harvey Millar
Keyword(s):  
Malic Enzyme ◽  
Metabolic Regulation ◽  
Plant Mitochondria ◽  
Tca Cycle ◽  
Pool Size ◽  
Isolated Mitochondria ◽  
Metabolic Products ◽  
The Matrix ◽  
Exogenous Addition ◽  
Different Sources

The majority of the pyruvate inside plant mitochondria is either transported into the matrix from the cytosol via the mitochondria pyruvate carrier (MPC) or synthesised in the matrix by alanine aminotransferase (AlaAT) or NAD-malic enzyme (NAD-ME). Pyruvate from these origins could mix into a single pool in the matrix and contribute indistinguishably to respiration, or they could maintain a degree of independence in metabolic regulation. Here, we demonstrated that feeding isolated mitochondria with U-13C-pyruvate and unlabelled malate enables the assessment of pyruvate contribution from different sources to TCA cycle intermediate production. Imported pyruvate is the preferred source for citrate production even when the synthesis of NAD-ME-derived pyruvate was optimised. Genetic or pharmacological elimination of MPC activity removed this preference and allowed an equivalent amount of citrate to be generated from the pyruvate produced by NAD-ME. Increasing mitochondrial pyruvate pool size by exogenous addition only affected metabolites from pyruvate transported by MPC whereas depleting pyruvate pool size by transamination to alanine only affected metabolic products derived from NAD-ME. Together, these data reveal respiratory substrate supply in plants involves distinct pyruvate pools inside the matrix that can be flexibly mixed based on the rate of pyruvate transport from the cytosol. These pools are independently regulated and contribute differentially to organic acids export from plant mitochondria.

scholarly journals Slow passive diffusion of NAD+ between intact isolated plant mitochondria and suspending medium

1983 ◽  
Vol 216 (2) ◽  
pp. 443-450 ◽  
Author(s):  
M Neuburger ◽  
R Douce
Keyword(s):  
Solanum Tuberosum ◽  
Plant Mitochondria ◽  
Passive Diffusion ◽  
High Rate ◽  
O2 Consumption ◽  
Initial State ◽  
Matrix Space ◽  
Isolated Mitochondria ◽  
The Matrix ◽  
Isopycnic Centrifugation

Isolated potato (Solanum tuberosum) tuber mitochondria purified by isopycnic centrifugation in density gradients of Percoll were found to be highly intact, to be devoid of extramitochondrial contaminations and to retain a high rate of O2 consumption. When suspended in a medium that avoided rupture of the outer membrane, intact purified mitochondria progressively lost their NAD+ content by passive diffusion. This led to a slow decrease of oxoglutarate-dependent O2 consumption by isolated mitochondria. Addition of NAD+ to the medium restored the initial State-3 rate of oxoglutarate oxidation. The rate of NAD+ accumulation in the matrix space was concentration-dependent, exhibited Michaelis-Menten kinetics and was strongly inhibited by the analogue N-4-azido-2-nitrophenyl-4-aminobutyryl-NAD+.

scholarly journals The mitochondrial pyruvate carrier (MPC) complex is one of three pyruvate-supplying pathways that sustain Arabidopsis respiratory metabolism

2021 ◽  
Author(s):  
Xuyen H. Le ◽  
Chun-Pong Lee ◽  
A. Harvey Millar
Keyword(s):  
Plant Growth ◽  
Plant Mitochondria ◽  
Complex Function ◽  
Tca Cycle ◽  
Respiratory Metabolism ◽  
The Tca Cycle ◽  
Mitochondrial Pyruvate Carrier ◽  
The Matrix ◽  
Branched Chain ◽  
Malate Oxidation

AbstractMalate oxidation by plant mitochondria enables the generation of both oxaloacetate (OAA) and pyruvate for tricarboxylic acid (TCA) cycle function, potentially eliminating the need for pyruvate transport into mitochondria in plants. Here we show that the absence of the mitochondrial pyruvate carrier 1 (MPC1) causes the co-commitment loss of its orthologs, MPC3/MPC4, and eliminates pyruvate transport into Arabidopsis mitochondria, proving it is essential for MPC complex function. While the loss of either MPC or mitochondrial pyruvate-generating NAD-malic enzyme (NAD-ME) did not cause vegetative phenotypes, the lack of both reduced plant growth and caused an increase in cellular pyruvate levels, indicating a block in respiratory metabolism, and elevated the levels of branched-chain amino acids at night, a sign of alterative substrate provision for respiration. 13C-pyruvate feeding of leaves lacking MPC showed metabolic homeostasis were largely maintained except for alanine and glutamate, indicating that transamination contributes to restoration of the metabolic network to an operating equilibrium by delivering pyruvate independently of MPC into the matrix. Inhibition of alanine aminotransferases (AlaAT) when MPC1 is absent resulted in extremely retarded phenotypes in Arabidopsis, suggesting all pyruvate-supplying enzymes work synergistically to support the TCA cycle for sustained plant growth.

scholarly journals Mitochondrial redox systems as central hubs in plant metabolism and signalling

2021 ◽  
Author(s):  
Olivier Van Aken
Keyword(s):  
Stress Responses ◽  
Plant Mitochondria ◽  
Nuclear Gene ◽  
Tca Cycle ◽  
Cellular Damage ◽  
Future Research ◽  
Antioxidant Systems ◽  
Plant Metabolism ◽  
Redox Systems ◽  
Glutathione Cycle

Abstract Plant mitochondria are indispensable for plant metabolism and are tightly integrated into cellular homeostasis. This review provides an update on the latest research concerning the organisation and operation of plant mitochondrial redox systems, and how they affect cellular metabolism and signalling, plant development and stress responses. New insights into the organisation and operation of mitochondrial energy systems such as the tricarboxylic acid (TCA) cycle and mitochondrial electron chain (mtETC) are discussed. The mtETC produces reactive oxygen and nitrogen species, which can act as signals or lead to cellular damage, and are thus efficiently removed by mitochondrial antioxidant systems, including Mn-superoxide dismutase, ascorbate-glutathione cycle and thioredoxin-dependent peroxidases. Plant mitochondria are tightly connected with photosynthesis, photorespiration and cytosolic metabolism, thereby providing redox-balancing. Mitochondrial proteins are targets of extensive post-translational modifications, but their functional significance and how they are added or removed remains unclear. To operate in sync with the whole cell, mitochondria can communicate their functional status via mitochondrial retrograde signalling to change nuclear gene expression, and several recent breakthroughs here are discussed. At a whole organism level, plant mitochondria thus play crucial roles from the first minutes after seed imbibition, supporting meristem activity, growth and fertility, until senescence of darkened and aged tissue. Finally, plant mitochondria are tightly integrated with cellular and organismal responses to environmental challenges such as drought, salinity, heat and submergence, but also threats posed by pathogens. Both the major recent advances and outstanding questions are reviewed, which may help future research efforts on plant mitochondria.

scholarly journals β-Hydroxybutyrate Oxidation Promotes the Accumulation of Immunometabolites in Activated Microglia Cells

Metabolites ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 346
Author(s):  
Adrian Benito ◽  
Nabil Hajji ◽  
Kevin O’Neill ◽  
Hector C. Keun ◽  
Nelofer Syed
Keyword(s):  
Metabolic Regulation ◽  
Marker Gene ◽  
Tca Cycle ◽  
Metabolic Reprogramming ◽  
Glycolytic Flux ◽  
Dihydroxyacetone Phosphate ◽  
Glycolytic Intermediate ◽  
Critical Set ◽  
The Tca Cycle ◽  
Bv2 Cells

Metabolic regulation of immune cells has arisen as a critical set of processes required for appropriate response to immunological signals. While our knowledge in this area has rapidly expanded in leukocytes, much less is known about the metabolic regulation of brain-resident microglia. In particular, the role of alternative nutrients to glucose remains poorly understood. Here, we use stable-isotope (13C) tracing strategies and metabolomics to characterize the oxidative metabolism of β-hydroxybutyrate (BHB) in human (HMC3) and murine (BV2) microglia cells and the interplay with glucose in resting and LPS-activated BV2 cells. We found that BHB is imported and oxidised in the TCA cycle in both cell lines with a subsequent increase in the cytosolic NADH:NAD+ ratio. In BV2 cells, stimulation with LPS upregulated the glycolytic flux, increased the cytosolic NADH:NAD+ ratio and promoted the accumulation of the glycolytic intermediate dihydroxyacetone phosphate (DHAP). The addition of BHB enhanced LPS-induced accumulation of DHAP and promoted glucose-derived lactate export. BHB also synergistically increased LPS-induced accumulation of succinate and other key immunometabolites, such as α-ketoglutarate and fumarate generated by the TCA cycle. Finally, BHB upregulated the expression of a key pro-inflammatory (M1 polarisation) marker gene, NOS2, in BV2 cells activated with LPS. In conclusion, we identify BHB as a potentially immunomodulatory metabolic substrate for microglia that promotes metabolic reprogramming during pro-inflammatory response.

scholarly journals A Matrix-Variate t Model for Networks

2021 ◽  
Vol 4 ◽  
Author(s):  
Monica Billio ◽  
Roberto Casarin ◽  
Michele Costola ◽  
Matteo Iacopini
Keyword(s):  
Network Analysis ◽  
Measurement Errors ◽  
Statistical Treatment ◽  
Centrality Measures ◽  
Random Errors ◽  
Inference Procedure ◽  
Financial Firms ◽  
The Matrix ◽  
Different Sources ◽  
Flexible Model

Networks represent a useful tool to describe relationships among financial firms and network analysis has been extensively used in recent years to study financial connectedness. An aspect, which is often neglected, is that network observations come with errors from different sources, such as estimation and measurement errors, thus a proper statistical treatment of the data is needed before network analysis can be performed. We show that node centrality measures can be heavily affected by random errors and propose a flexible model based on the matrix-variate t distribution and a Bayesian inference procedure to de-noise the data. We provide an application to a network among European financial institutions.

Tricarboxylic acid cycle intermediates in human muscle at rest and during prolonged cycling

1997 ◽  
Vol 272 (2) ◽  
pp. E239-E244 ◽  
Author(s):  
M. J. Gibala ◽  
M. A. Tarnopolsky ◽  
T. E. Graham
Keyword(s):  
Fiber Type ◽  
Tricarboxylic Acid Cycle ◽  
Vastus Lateralis ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Human Muscle ◽  
Pool Size ◽  
Recruitment Pattern ◽  
Total Pool ◽  
Tca Cycle Intermediates

Previous studies have used the muscle concentration of citrate + malate + fumarate to estimate tricarboxylic acid (TCA) cycle pool size in humans [e.g., Am. J. Physiol. 259 (Cell Physiol. 28): C834-C841, 1990]. Our purpose was to quantify changes in individual TCA cycle intermediates (TCAI) and total pool size by measuring the concentrations of the eight TCAI in human muscle. Eight males cycled to exhaustion (Exh) at approximately 70% of their maximal oxygen uptake, and biopsies were obtained from the vastus lateralis at rest and during exercise. Succinyl-CoA was not consistently detectable, but the sum of the other seven TCAI was 1.23 +/- 0.04 mmol/kg dry wt at rest, 4.80 +/- 0.25 and 4.87 +/- 0.30 mmol/kg after 5 and 15 min of exercise, respectively, and 3.08 +/- 0.15 mmol/kg at Exh. Pool size during exercise was approximately 50% higher than that seen in rodent muscle after intense electrical stimulation (Eur. J. Biochem. 110: 371-377, 1980). Relative changes in individual TCAI were not uniform, and no one intermediate was "representative" of the changes in total pool size. We conclude that changes in specific intermediates or total pool size cannot be used as indicators of cycle flux and that the apparent species differences in total pool size may reflect differences in fiber type composition, recruitment pattern, or relative intensity of contraction.

Metabolic regulation at the tricarboxylic acid and glyoxylate cycles of the lignin-degrading basidiomycetePhanerochaete chrysosporium against exogenous addition of vanillin

PROTEOMICS ◽  
2005 ◽  
Vol 5 (15) ◽  
pp. 3919-3931 ◽  
Author(s):  
Motoyuki Shimizu ◽  
Naoki Yuda ◽  
Tomofumi Nakamura ◽  
Hiroo Tanaka ◽  
Hiroyuki Wariishi
Keyword(s):  
Metabolic Regulation ◽  
Tricarboxylic Acid ◽  
Exogenous Addition

Protein hyperacylation links mitochondrial dysfunction with nuclear organization

2020 ◽  
Author(s):  
John Smestad ◽  
Micah McCauley ◽  
Matthew Amato ◽  
Yuning Xiong ◽  
Juan Liu ◽  
...  
Keyword(s):  
Chromatin Structure ◽  
Metabolic Regulation ◽  
Tca Cycle ◽  
Interphase Chromatin ◽  
Histone Octamer ◽  
The Tca Cycle ◽  
Transport Chain ◽  
Topologically Associated Domains ◽  
Biophysical Effects ◽  
Liquid Liquid Phase Separation

SummaryCellular metabolism is linked to epigenetics, but the biophysical effects of metabolism on chromatin structure and implications for gene regulation remain largely unknown. Here, using a broken tricarboxylic acid (TCA) cycle and disrupted electron transport chain (ETC) exemplified by succinate dehydrogenase subunit C (SDHC) deficiency, we investigated the effects of metabolism on chromatin architecture over multiple distance scales [nucleosomes (∼102 bp), topologically-associated domains (TADs; ∼105 – 106 bp), and chromatin compartments (106 – 108 bp)]. Metabolically-driven hyperacylation of histones led to weakened nucleosome positioning in multiple types of chromatin, and we further demonstrate that lysine acylation directly destabilizes histone octamer-DNA interactions. Hyperacylation of cohesin subunits correlated with decreased mobility on interphase chromatin and increased TAD boundary strength, suggesting that cohesin is metabolically regulated. Erosion of chromatin compartment distinctions reveals metabolic regulation of chromatin liquid-liquid phase separation. The TCA cycle and ETC thus modulate chromatin structure over multiple distance scales.

Regular and copular fragments in Basaá

Linguistics ◽  
2019 ◽  
Vol 57 (5) ◽  
pp. 915-966 ◽  
Author(s):  
Paul Roger Bassong
Keyword(s):  
Left Periphery ◽  
Matrix Clause ◽  
Polarity Item ◽  
Regular Source ◽  
Fragment Answers ◽  
The Matrix ◽  
Embedded Clause ◽  
Crosslinguistic Variation ◽  
New Evidence ◽  
Different Sources

Abstract The aim of this Article is to propose that fragment answers in Basaá (Bantu) derive from two different sources, namely, a regular source and a copular source. Regular fragments are those that are derived by movement of a Negative Polarity Item (NPI) or a CP complement to the left periphery of the clause followed by clausal ellipsis (Merchant 2004 and related work). Conversely, copular fragments involve a biclausal structure whereby the focalized fragment, no matter the syntactic function it fulfills in clause structure, finally ends up being the subject of the null verbal copula of the main clause. The fragment is initially selected as the external argument of the null verbal copula within the matrix VP along the lines of the VP-Internal Subject Hypothesis (Koopman and Sportiche 1991). From Spec-VP it raises to Spec-TP to satisfy the EPP requirements. The internal argument of the null copula is a headless relative in which a relative operator (covert/overt) moves to Spec-CP, a position above FocP the target of ellipsis. This gives rise to a structure whereby the fragment answer in the matrix clause and the relative operator in the embedded clause resist ellipsis. The analysis also provides semantic evidence that copular fragments are not clefts. The ellipsis approach is supported by a range of grammatical properties such as connectivity effects, locality constraints and subcategorization requirements. This paper is not only a contribution to Merchant’s (2004) ellipsis approach but it also provides new evidence for our understanding of the crosslinguistic variation of ellipsis.

scholarly journals MORPHOLOGY AND ATP-ASE OF ISOLATED MITOCHONDRIA

1955 ◽  
Vol 1 (2) ◽  
pp. 127-138 ◽  
Author(s):  
Robert F. Witter ◽  
Michael L. Watson ◽  
Mary A. Cottone
Keyword(s):  
Electron Microscope ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Substantial Part ◽  
Mitochondrial Matrix ◽  
Isolated Mitochondria ◽  
The Matrix ◽  
First Time ◽  
Methods Of Isolation

Changes in the morphology of rat liver mitochondria brought about by different methods of isolation and the concomitant changes in ATP-ase activity were studied. The morphology was investigated with the electron microscope. It was found that the ATP-ase activity of the isolated mitochondria cannot be readily correlated with the morphology of the mitochondria. The ATP-ase found in these preparations was latent, resembling the enzyme described in mitochondria prepared in 0.25 M sucrose. In confirmation of earlier results the use of 0.88 M sucrose yielded preparations with a higher initial ATP-ase than did other methods. Preparation in 0.25 M sucrose resulted in round, swollen mitochondria of which 30 to 40 per cent appeared to have lost a substantial part of the mitochondrial matrix. Preparations in 0.44 to 0.88 M sucrose contained mainly rod-shaped mitochondria plus a small amount of another type of swollen mitochondria. The matrix of mitochondria isolated in 0.88 M sucrose was highly condensed. By the use of 0.44 M sucrose adjusted to pH 6.2 with citric acid, it was possible to isolate, for the first time, mitochondria closely resembling those in situ and containing latent ATP-ase.

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