Cytosolic Ca2+ regulates the energization of isolated brain mitochondria by formation of pyruvate through the malate–aspartate shuttle

2012 ◽  
Vol 443 (3) ◽  
pp. 747-755 ◽  
Author(s):  
Frank Norbert Gellerich ◽  
Zemfira Gizatullina ◽  
Sonata Trumbekaite ◽  
Bernard Korzeniewski ◽  
Timur Gaynutdinov ◽  
...  
Keyword(s):  
Lactate Dehydrogenase ◽  
Brain Mitochondria ◽  
Central Component ◽  
Mitochondrial Matrix ◽  
Oxidation Rates ◽  
Key Factor ◽  
Common Substrate ◽  
Reconstituted System ◽  
Malate Aspartate Shuttle ◽  
Ldh Lactate Dehydrogenase

The glutamate-dependent respiration of isolated BM (brain mitochondria) is regulated by Ca2+cyt (cytosolic Ca2+) (S0.5=225±22 nM) through its effects on aralar. We now also demonstrate that the α-glycerophosphate-dependent respiration is controlled by Ca2+cyt (S0.5=60±10 nM). At higher Ca2+cyt (>600 nM), BM accumulate Ca2+ which enhances the rate of intramitochondrial dehydrogenases. The Ca2+-induced increments of state 3 respiration decrease with substrate in the order glutamate>α-oxoglutarate>isocitrate>α-glycerophosphate>pyruvate. Whereas the oxidation of pyruvate is only slightly influenced by Ca2+cyt, we show that the formation of pyruvate is tightly controlled by Ca2+cyt. Through its common substrate couple NADH/NAD+, the formation of pyruvate by LDH (lactate dehydrogenase) is linked to the MAS (malate–aspartate shuttle) with aralar as a central component. A rise in Ca2+cyt in a reconstituted system consisting of BM, cytosolic enzymes of MAS and LDH causes an up to 5-fold enhancement of OXPHOS (oxidative phosphorylation) rates that is due to an increased substrate supply, acting in a manner similar to a ‘gas pedal’. In contrast, Ca2+mit (intramitochondrial Ca2+) regulates the oxidation rates of substrates which are present within the mitochondrial matrix. We postulate that Ca2+cyt is a key factor in adjusting the mitochondrial energization to the requirements of intact neurons.

scholarly journals The Effect of Modified Biolasol Solution on the Efficacy of Storing Isolated Porcine Kidneys

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Aneta Ostróżka-Cieślik ◽  
Barbara Dolińska ◽  
Florian Ryszka
Keyword(s):  
Ascorbic Acid ◽  
Lactate Dehydrogenase ◽  
Vitamin C ◽  
Alanine Aminotransferase ◽  
Lactate Concentration ◽  
Synergistic Action ◽  
High Efficacy ◽  
Graft Storage ◽  
Ldh Lactate Dehydrogenase ◽  
Alt Alanine Aminotransferase

Biolasol is a newly developed solution for storing the liver, pancreas, kidneys, and heart by simple hypothermia. It exhibits high efficacy in maintaining structural and functional integrity of the graft prior to its transplantation. The solution was modified by the addition of ascorbic acid (0.088g/l) and ascorbic acid with prolactin (1 μg/l PRL + 0.088g/l vitamin C). The effectiveness of the obtained solutions in the protection of nephrons of isolated porcine kidneys was assessed based on the analysis of the activity of ALT (alanine aminotransferase), AST (aspartate aminotransferase), and LDH (lactate dehydrogenase) as well as lactate concentration determined in perfundates collected after 2 h (0′ and 30′ preservation) and 48 h (0′ and 30′ preservation) of graft storage. It has been found that the synergistic action of Biolasol components determines the integrity and stability of cell membranes, which in turn affects the proper functioning of the organ after transplantation. The addition of ascorbic acid and prolactin to Biolasol affects the maintenance of the normal cytoskeleton of the stored graft.

scholarly journals The reconstitution of l-3-glycerophosphate-cytochrome c oxidoreductase from l-3-glycerophosphate dehydrogenase, ubiquinone-10 and ubiquinol—cytochrome c oxidoreductase

1980 ◽  
Vol 192 (1) ◽  
pp. 19-31 ◽  
Author(s):  
I R Cottingham ◽  
C I Ragan
Keyword(s):  
Cytochrome C ◽  
Nadh Dehydrogenase ◽  
Brain Mitochondria ◽  
Complex Iii ◽  
Protein Ratio ◽  
Bovine Heart ◽  
Glycerophosphate Dehydrogenase ◽  
Reconstituted System ◽  
Ubiquinone 10 ◽  
Self Aggregation

Purified L-3-glycerophosphate dehydrogenase from pig brain mitochondria interacts with ubiquinone-10 and ubiquinol-cytochrome c oxidoreductase (Complex III) from bovine heart mitochondria to reconstitute antimycin-sensitive L-3-glycerophosphate- cytochrome c oxidoreductase. This activity is completely dependent on the two enzymes and largely dependent on ubiquinone-10. Reconstitution requires that the two enzymes should be simultaneously present in the same membranous aggregate produced by removal of detergent from the enzymes. Reconstitution by removing detergent by dialysis or dilution is inefficient because of self-aggregation of the dehydrogenase. Highly efficient reconstitution can be achieved if the enzymes are co-precipitated by addition of ethanol. The rate with reconstituted enzyme approaches that expected from the turnover of the dehydrogenase with ubiquinone-1 as acceptor. The behaviour of the reconstituted system shows some of the characteristics expected for a stoicheiometric association of one molecule of dehydrogenase with one molecule of Complex III. On raising the phospholipid/protein ratio, the dehydrogenase and Complex III appear to operate as independent enzymes acting in sequence. These effects are very similar to those observed for the interaction of NADH dehydrogenase and Complex III and are explained in terms of the model proposed by Heron, Ragan & Trumpower [(1978) biochem. J. 174, 791-800].

scholarly journals Lactate is oxidized outside of the mitochondrial matrix in rodent brain

2018 ◽  
Vol 43 (5) ◽  
pp. 467-474 ◽  
Author(s):  
Eric A.F. Herbst ◽  
Mitchell A.J. George ◽  
Karen Brebner ◽  
Graham P. Holloway ◽  
Daniel A. Kane
Keyword(s):  
Brain Mitochondria ◽  
Muscle Fibres ◽  
Mitochondrial Matrix ◽  
Lactate Oxidation ◽  
Rodent Brain ◽  
The Matrix ◽  
Mouse Brain Cortex ◽  
Glutamate Pyruvate ◽  
Permeabilized Muscle ◽  
Mitochondrial Reticulum

The nature and existence of mitochondrial lactate oxidation is debated in the literature. Obscuring the issue are disparate findings in isolated mitochondria, as well as relatively low rates of lactate oxidation observed in permeabilized muscle fibres. However, respiration with lactate has yet to be directly assessed in brain tissue with the mitochondrial reticulum intact. To determine if lactate is oxidized in the matrix of brain mitochondria, oxygen consumption was measured in saponin-permeabilized mouse brain cortex samples, and rat prefrontal cortex and hippocampus (dorsal) subregions. While respiration in the presence of ADP and malate increased with the addition of lactate, respiration was maximized following the addition of exogenous NAD+, suggesting maximal lactate metabolism involves extra-matrix lactate dehydrogenase. This was further supported when NAD+-dependent lactate oxidation was significantly decreased with the addition of either low-concentration α-cyano-4-hydroxycinnamate or UK-5099, inhibitors of mitochondrial pyruvate transport. Mitochondrial respiration was comparable between glutamate, pyruvate, and NAD+-dependent lactate oxidation. Results from the current study demonstrate that permeabilized brain is a feasible model for assessing lactate oxidation, and support the interpretation that lactate oxidation occurs outside the mitochondrial matrix in rodent brain.

scholarly journals Geographic and seasonal variation of dissolved methane and aerobic methane oxidation in Alaskan lakes

2015 ◽  
Vol 12 (15) ◽  
pp. 4595-4606 ◽  
Author(s):  
K. Martinez-Cruz ◽  
A. Sepulveda-Jauregui ◽  
K. Walter Anthony ◽  
F. Thalasso
Keyword(s):  
Organic Carbon ◽  
Ch4 Oxidation ◽  
Geographic Variations ◽  
Large Variability ◽  
Thermokarst Lakes ◽  
Oxidation Rates ◽  
Key Factor ◽  
Thawing Permafrost ◽  
Surrounding Landscape ◽  
Dissolved O2

Abstract. Methanotrophic bacteria play an important role oxidizing a significant fraction of methane (CH4) produced in lakes. Aerobic CH4 oxidation depends mainly on lake CH4 and oxygen (O2) concentrations, in such a manner that higher MO rates are usually found at the oxic/anoxic interface, where both molecules are present. MO also depends on temperature, and via methanogenesis, on organic carbon input to lakes, including from thawing permafrost in thermokarst (thaw)-affected lakes. Given the large variability in these environmental factors, CH4 oxidation is expected to be subject to large seasonal and geographic variations, which have been scarcely reported in the literature. In the present study, we measured CH4 oxidation rates in 30 Alaskan lakes along a north-south latitudinal transect during winter and summer with a new field laser spectroscopy method. Additionally, we measured dissolved CH4 and O2 concentrations. We found that in the winter, aerobic CH4 oxidation was mainly controlled by the dissolved O2 concentration, while in the summer it was controlled primarily by the CH4 concentration, which was scarce compared to dissolved O2. The permafrost environment of the lakes was identified as another key factor. Thermokarst (thaw) lakes formed in yedoma-type permafrost had significantly higher CH4 oxidation rates compared to other thermokarst and non-thermokarst lakes formed in non-yedoma permafrost environments. As thermokarst lakes formed in yedoma-type permafrost have been identified to receive large quantities of terrestrial organic carbon from thaw and subsidence of the surrounding landscape into the lake, confirming the strong coupling between terrestrial and aquatic habitats and its influence on CH4 cycling.

scholarly journals Cytosolic, but not matrix, calcium is essential for adjustment of mitochondrial pyruvate supply

2020 ◽  
Vol 295 (14) ◽  
pp. 4383-4397 ◽  
Author(s):  
Marten Szibor ◽  
Zemfira Gizatullina ◽  
Timur Gainutdinov ◽  
Thomas Endres ◽  
Grazyna Debska-Vielhaber ◽  
...  
Keyword(s):  
Oxidation Reaction ◽  
Control Mechanisms ◽  
Mitochondrial Matrix ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Phenotypic Changes ◽  
Substrate Supply ◽  
Health And Disease ◽  
Malate Aspartate Shuttle ◽  
Working Rat Heart

Mitochondrial oxidative phosphorylation (OXPHOS) and cellular workload are tightly balanced by the key cellular regulator, calcium (Ca2+). Current models assume that cytosolic Ca2+ regulates workload and that mitochondrial Ca2+ uptake precedes activation of matrix dehydrogenases, thereby matching OXPHOS substrate supply to ATP demand. Surprisingly, knockout (KO) of the mitochondrial Ca2+ uniporter (MCU) in mice results in only minimal phenotypic changes and does not alter OXPHOS. This implies that adaptive activation of mitochondrial dehydrogenases by intramitochondrial Ca2+ cannot be the exclusive mechanism for OXPHOS control. We hypothesized that cytosolic Ca2+, but not mitochondrial matrix Ca2+, may adapt OXPHOS to workload by adjusting the rate of pyruvate supply from the cytosol to the mitochondria. Here, we studied the role of malate-aspartate shuttle (MAS)-dependent substrate supply in OXPHOS responses to changing Ca2+ concentrations in isolated brain and heart mitochondria, synaptosomes, fibroblasts, and thymocytes from WT and MCU KO mice and the isolated working rat heart. Our results indicate that extramitochondrial Ca2+ controls up to 85% of maximal pyruvate-driven OXPHOS rates, mediated by the activity of the complete MAS, and that intramitochondrial Ca2+ accounts for the remaining 15%. Of note, the complete MAS, as applied here, included besides its classical NADH oxidation reaction the generation of cytosolic pyruvate. Part of this largely neglected mechanism has previously been described as the “mitochondrial gas pedal.” Its implementation into OXPHOS control models integrates seemingly contradictory results and warrants a critical reappraisal of metabolic control mechanisms in health and disease.

Democratic Openings and Country Visibility: Media Attention and the Allocation of US Democracy Aid, 1975–2010

2019 ◽  
Vol 16 (3) ◽  
pp. 373-396
Author(s):  
James M Scott ◽  
Charles M Rowling ◽  
Timothy M Jones
Keyword(s):  
Media Coverage ◽  
The United States ◽  
Central Component ◽  
Media Attention ◽  
Democracy Assistance ◽  
Key Factor ◽  
Policy Priority ◽  
Effects Of Media ◽  
The Impact

Abstract Late in the twentieth century, the United States embraced democracy promotion as a foreign policy priority, a central component of which involved allocating democracy aid to governments, political parties, and nongovernmental organizations around the world to support and encourage democratization. Nonetheless, as a scarce resource, democracy assistance is allocated selectively: some states receive substantial commitments while others receive none. As previous studies have concluded, democracy aid allocations are, in part, strategic bets placed on the likelihood of progress toward and consolidation of democracy, as donors consider cues that identify situations where democracy aid is likely to be most successful. We introduce the role of media coverage as a key factor in democracy aid allocations and argue that a shift toward democracy within a potential recipient state interacts with media attention to that state to generate cues for aid allocators. To gauge the agenda-setting and cueing effects of media coverage on democracy aid allocations, we examine US democracy assistance from 1975 to 2010, weighing the impact of media attention, democratic openings, and other factors related to recipient characteristics and US political, strategic, economic, and ideational interests on democracy assistance. We conclude with a discussion of the implications of these findings.

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