Adenosine Triphosphate Production Rate Research Articles

The Warburg Effect is the result of faster ATP production by glycolysis than respiration

Many prokaryotic and eukaryotic cells metabolize glucose to organism-specific by-products instead of fully oxidizing it to carbon dioxide and water-a phenomenon referred to as the Warburg Effect. The benefit to a cell is not fully understood, given that partial metabolism of glucose yields an order of magnitude less adenosine triphosphate (ATP) per molecule of glucose than complete oxidation. Here, we test a previously formulated hypothesis that the benefit of the Warburg Effect is to increase ATP production rate by switching from high-yielding respiration to faster glycolysis when excess glucose is available and respiration rate becomes limited by proteome occupancy. We show that glycolysis produces ATP faster per gram of pathway protein than respiration in Escherichia coli, Saccharomyces cerevisiae, and mammalian cells. We then develop a simple mathematical model of energy metabolism that uses five experimentally estimated parameters and show that this model can accurately predict absolute rates of glycolysis and respiration in all three organisms under diverse conditions, providing strong support for the validity of the ATP production rate maximization hypothesis. In addition, our measurements show that mammalian respiration produces ATP up to 10-fold slower than respiration in E. coli or S. cerevisiae, suggesting that the ATP production rate per gram of pathway protein is a highly evolvable trait that is heavily optimized in microbes. We also find that E. coli respiration is faster than fermentation, explaining the observation that E. coli, unlike S. cerevisiae or mammalian cells, never switch to pure fermentation in the presence of oxygen.

Bacillus cereus Sensu Lato Accelerate Cellular Bioenergetic Metabolism of Human Colorectal Adenocarcinoma Caco-2 Cell Line.

How foodborne enterotoxigenic Bacillus cereus rewires energy metabolism during intestinal tract infection is still not understood. In this study, we used the Seahorse XFe technology to simultaneously analyze oxygen consumption and acidification rates to estimate bioenergetic changes in the intestinal Caco-2 cell line after exposure to the B. cereus sensu lato (s.l.) enterotoxin-producing pathotypes, American Type Culture Collection (ATCC) 14579 (836), NVH0391-98 (828), and NVH0075/95 (825). Infection of Caco-2 led to a more energetic phenotype due to increased flux through oxidative phosphorylation and glycolysis. Strain 836 caused the most pronounced effects toward the specific energy phenotype, followed by strains 828 and 825. However, the metabolic potential of Caco-2 cells was most strongly induced by the 828 strain. Furthermore, infected cells manifested an increased adenosine triphosphate (ATP) production rate. Strain 828 caused the highest glycolytic and mitochondrial ATP production rates, followed by the 836 and 825 B. cereus s.l. strains. The glycolytic stress assay showed that strains 828 and 826 slightly increased compensatory glycolysis, providing a better understanding of the pathogenicity of this versatile pathogen. The results of this study underline that extracellular flux measurement can be used to accurately estimate bioenergetic perturbations of Caco-2 cells as a consequence of infection. Our findings enhance our understanding of how intestinal cells adjust their metabolism during infection with B. cereus s.l.

Succinate oxidation rescues mitochondrial ATP synthesis at high temperature in Drosophila melanogaster.

Decreased NADH-induced and increased reduced FADH2 -induced respiration rates at high temperatures are associated with thermal tolerance in Drosophila. Here, we determined whether this change was associated with adjustments of adenosine triphosphate (ATP) production rate and coupling efficiency (ATP/O) in Drosophila melanogaster. We show that decreased pyruvate + malate oxidation at 35°C is associated with a collapse of ATP synthesis and a drop in ATP/O ratio. However, adding succinate triggered a full compensation of both oxygen consumption and ATP synthesis rates at this high temperature. Addition of glycerol-3-phosphate (G3P) led to a huge increase in respiration with no further advantage in terms of ATP production. We conclude that succinate is the only alternative substrate able to compensate both oxygen consumption and ATP production rates during oxidative phosphorylation at high temperature, which has important implications for thermal adaptation.

Accurate Visualization of Metabolic Aberrations in Cancer Cells by Temperature Mapping with Quantum Coherence Modulation Microscopy.

Specific metabolic aberrations of cancer cells rapidly generate energy with a minuscule but detectable temperature variation, which is a typical characteristic providing insight into cancer pathogenesis. However, to date, intracellular temperature mapping of cancer cell metabolism with high temporal and spatial resolution has not been realized. In this study, we mapped and monitored in real-time the intracellular temperature variations of mitochondria and cytoplasm at a subcellular scale via a single-molecule coherent modulation microscopy coupling targeted molecule labeling technique. According to the variation of the decoherence processes of targeted molecules as a function of intracellular temperature, we achieved a high temperature resolution (<0.1 K) and proved that this technique could eliminate interference from fluorescence intensity disturbance and external pH change. Furthermore, we showed a positive correlation between the determined temperature and the adenosine triphosphate production rate of mitochondrial metabolism in combination with a cell energy metabolic analyzer. This technology enables accurate real-time temporal and spatial visualization of cancer metabolism and establishes diagnoses and therapies for cancer.

Lysosomal acid lipase regulates bioenergetic process during the cytodifferentiation of human periodontal ligament cells

Lipid metabolism is one of energy metabolic pathways that produce adenosine triphosphate (ATP). In this pathway, lysosomal acid lipase (LAL) encoded by Lipase A (LIPA), plays an important role in catalyzing lipids to fatty acids (FAs), which drive oxidative phosphorylation (OXPHOS) and generate ATP. Previously, we found that a LIPA single nucleotide polymorphism rs143793106, which decreases the LAL activity, suppressed the cytodifferentiation of human periodontal ligament (HPDL) cells. However, the mechanisms underlying that suppression are still not fully clarified. Thus, we aimed to investigate the mechanisms regulating the cytodifferentiation of HPDL cells by LAL in terms of energy metabolism. We performed the osteogenic induction of HPDL cells with or without Lalistat-2, a LAL inhibitor. To visualize lipid droplet (LD) utilization, we performed confocal microscopy on HPDL cells. We also performed real-time PCR to analyze the gene expression of calcification-related and metabolism-related genes. Furthermore, we measured the ATP production rate from two major energy production pathways, OXPHOS and glycolysis, and OXPHOS-related parameters of HPDL cells during their cytodifferentiation. We found that LDs were utilized during the cytodifferentiation of HPDL cells. Alkaline phosphatase (ALPL), collagen type 1 alpha 1 chain (COL1A1), ATP synthase F1 subunit alpha (ATP5F1A), and carnitine palmitoyltransferase 1A (CPT1A) mRNA expressions were upregulated, whereas lactate dehydrogenase A (LDHA) mRNA expression was downregulated. Additionally, total ATP production rate was significantly increased. In contrast, in the presence of Lalistat-2, LD utilization was inhibited and ALPL, COL1A1, and ATP5F1A mRNA expression was downregulated. Additionally, ATP production rate and spare respiratory capacity of the OXPHOS pathway were decreased in HPDL cells during their cytodifferentiation. Collectively, the defect of LAL in HPDL cells decreased LD utilization and OXPHOS capacity, resulting in reduced energy to sustain the adequate ATP production required for the cytodifferentiation of HPDL cells. Thus, LAL is important for periodontal tissue homeostasis as a regulator of bioenergetic process of HPDL cells.

Abstract 4835: EP4 increases the mitochondrial respiration and promotes cell migration in oral cancer

Abstract Introduction: EP4 is one of the prostaglandin E2 (PGE2) receptors. We previously reported that EP4 promoted cell migration via Ca2+ signaling, however the underlying mechanism has remained unclear. In Ca2+ signaling, Store-operated Ca2+entry (SOCE) is a major mechanism of Ca2+ import from the extracellular to the intracellular space. Orai1, one of the selective Ca2+ channels, plays an important role in SOCE. We focused on the correlation with EP4 and Orai1. Additionally, we found that EP4 promoted the phosphorylation of calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) and AMP-activated protein kinase (AMPK) located downstream of CaMKK2, i.e., cell energy regulators. AMPK activation can control positively or negatively the cellular adenosine triphosphate (ATP) supply. Therefore, we investigated how EP4 regulated the mitochondrial function via Ca2+ and promoted the cell migration in oral cancer cells. Materials and Methods: HSC-3, human tongue squamous cell carcinoma cell line was used. ONO-AE1-437 was used as EP4 agonist. HSC-3 cells were transduced with Orai1 shRNA, and control shRNA using lentivirus. The migration ability was evaluated by scratch assay. Measurement of intracellular Ca2+ concentration was measured using Fura-2. Immunoprecipitation was performed to evaluate the interaction between EP4 and Orai1. XF Cell Mito Stress Test and XF Real-Time ATP Rate Assay were performed to evaluate the mitochondrial aspiration and the ATP production using Extracellular Flux Analyzer. Results: Scratch assay showed EP4 promoted cell migration in oral cancer cells (n=4, p&amp;lt;0.05). In contrast, Orai1 knockdown negated EP4-induced cell migration. EP4 rapidly increased the intracellular Ca2+ concentration, while Orai1 knockdown negated EP4-indued Ca2+ increase (n=4, p&amp;lt;0.05). Immunoprecipitation showed that EP4 was colocalized and formed complexes with Orai1 (n=4, p&amp;lt;0.05). These results indicated that EP4 promoted the cell migration via Ca2+ signaling through Orai1. EP4 increased the maximal respiration 3h after the stimulation (n=6, p&amp;lt;0.05). ATP production rate shifted mitoATP dominant. These data indicated that EP4 increased the mitochondrial function and the respiratory capacity, potentially regulating its energy supply. These results demonstrated that EP4 promoted mitochondria respiration and then increased the energy production from mitochondria in oral cancer cells. Conclusion: We concluded that EP4 regulated the mitochondrial function via Ca2+ through Orai1 and promoted the cell migration in oral cancer cells. Citation Format: Rina Nakakaji, Masanari Umemura, Kohei Osawa, Soichiro Ishikawa, Kenji Mitsudo, Yoshihiro Ishikawa. EP4 increases the mitochondrial respiration and promotes cell migration in oral cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4835.

Glucose metabolism in amyotrophic lateral sclerosis: it is bitter-sweet.

Glucose metabolism in amyotrophic lateral sclerosis: it is bitter-sweet.

In vitro biosynthesis of ATP from adenosine and polyphosphate

Adenosine triphosphate (ATP) acts as a crucial energy currency in vivo, and it is a widely used energy and/or phosphate donor for enzyme-catalyzed reactions in vitro. In this study, we established an in vitro multi-enzyme cascade system for ATP production. Using adenosine and inorganic polyphosphate (polyP) as key substrates, we combined adenosine kinase and two functionally distinct polyphosphate kinases (PPKs) in a one-pot reaction to achieve chain-like ATP regeneration and production. Several sources of PPK were screened and characterized, and two suitable PPKs were selected to achieve high rates of ATP production. Among these, Sulfurovum lithotrophicum PPK (SlPPK) exhibited excellent activity over a wide pH range (pH 4.0–9.0) and synthesized ATP from ADP using short-chain polyP. Furthermore, it had a half-life > 155.6 h at 45 °C. After optimizing the reaction conditions, we finally carried out the coupling-catalyzed reaction with different initial adenosine concentrations of 10, 20, and 30 mM. The highest yields of ATP were 76.0, 70.5, and 61.3%, respectively.Graphical

A sex chromosome inversion is associated with copy number variation of mitochondrial DNA in zebra finch sperm

The propulsion of sperm cells via movement of the flagellum is of vital importance for successful fertilization. While the exact mechanism of energy production for this movement varies between species, in avian species energy is thought to come predominantly from the mitochondria located in the sperm midpiece. Larger midpieces may contain more mitochondria, which should enhance the energetic capacity and possibly promote mobility. Due to an inversion polymorphism on their sex chromosome TguZ, zebra finches (Taeniopygia guttata castanotis) exhibit large within-species variation in sperm midpiece length, and those sperm with the longest midpieces swim the fastest. Here, we test through quantitative real-time PCR in zebra finch ejaculates whether the inversion genotype has an effect on the copy number of mitochondrial DNA (mtDNA). We find that zebra finches carrying the derived allele (correlated with longer sperm midpieces) have more copies of the mtDNA in their ejaculates than those homozygous for the ancestral allele (shorter midpieces). We suggest downstream effects of mtDNA copy number variation on the rate of adenosine triphosphate production, which in turn may influence sperm swimming speed and fertilization success. Central components of gamete energy metabolism may thus be the proximate cause for a fitness-relevant genetic polymorphism, stabilizing a megabase-scale inversion at an intermediate allele frequency in the wild.

Assessing Bioenergetic Function in Response to Reactive Oxygen Species in Neural Cells

In this study, we characterized the bioenergetic response of the Lund human mesencephalic (LUHMES) cell line and a mouse astrocyte cell line to oxidative stress. Extracellular hydrogen peroxide (H2O2) levels and bioenergetic response were investigated in these cell lines after exposure to paraquat (PQ), a redox cycling compound that causes oxidative stress in cells. We used extracellular flux analysis to measure mitochondrial function in adherent astrocytes and LUHMES cells. Extracellular H2O2 was measured fluorometrically. H2O2 levels increased in both cell lines after exposure to 5 µM PQ for 18 h; however, the extent of H2O2 increase with astrocytes was significantly lower than that with LUHMES cells (33% vs. 67%). Measurements of basal mitochondrial respiration showed that PQ almost completely eliminated oxygen consumption rate (OCR) in astrocytes and significantly reduced it in LUHMES cells. Notably, OCR in LUHMES cells was higher than that in astrocytes, indicating that neuronal cells maintain higher oxidative metabolism than glial cells, which is also consistent with higher energy demands of the neuronal cells. Moreover, LUHMES cells exhibited a higher amount of adenosine triphosphate (ATP) being produced by oxidative phosphorylation than by glycolysis. In contrast, astrocytes demonstrated a higher glycolytic capacity and glycolytic reserve than LUHMES cells and higher ATP production rate by glycolysis than its production by mitochondrial oxidative metabolism. Collectively, this study showed the differential bioenergetic responses between astrocytes and LUHMES cells in responding to oxidative stress and the findings may provide insights into the mitochondrial reserve capacity in neurons and astrocytes in responding to oxidative stress. (First online: Mar 30, 2021)

Quantitative Assessment of Occipital Metabolic and Energetic Changes in Parkinson's Patients, Using In Vivo 31P MRS-Based Metabolic Imaging at 7T.

Abnormal energy metabolism associated with mitochondrial dysfunction is thought to be a major contributor to the progression of neurodegenerative diseases such as Parkinson’s disease (PD). Recent advancements in the field of magnetic resonance (MR) based metabolic imaging provide state-of-the-art technologies for non-invasively probing cerebral energy metabolism under various brain conditions. In this proof-of-principle clinical study, we employed quantitative 31P MR spectroscopy (MRS) imaging techniques to determine a constellation of metabolic and bioenergetic parameters, including cerebral adenosine triphosphate (ATP) and other phosphorous metabolite concentrations, intracellular pH and nicotinamide adenine dinucleotide (NAD) redox ratio, and ATP production rates in the occipital lobe of cognitive-normal PD patients, and then we compared them with age-sex matched healthy controls. Small but statistically significant differences in intracellular pH, NAD and ATP contents and ATPase enzyme activity between the two groups were detected, suggesting that subtle defects in energy metabolism and mitochondrial function are quantifiable before regional neurological deficits or pathogenesis begin to occur in these patients. Pilot data aiming to evaluate the bioenergetic effect of mitochondrial-protective bile acid, ursodeoxycholic acid (UDCA) were also obtained. These results collectively demonstrated that in vivo 31P MRS-based neuroimaging can non-invasively and quantitatively assess key metabolic-energetic metrics in the human brain. This provides an exciting opportunity to better understand neurodegenerative diseases, their progression and response to treatment.

Real-Time Assessment of Mitochondrial Toxicity in HepG2 Cells Using the Seahorse Extracellular Flux Analyzer.

The liver is the primary organ responsible for drug detoxification. Drug-induced liver injury (DILI) is a leading cause of attrition during drug development and is one of the main reasons that drugs are withdrawn from the market. Hence, the prevention of DILI plays a central role in the overall drug-discovery process. Most of the liver's energy supply comes in the form of adenosine triphosphate (ATP), which is largely generated by mitochondria. This article describes the evaluation of drug-induced mitochondrial dysfunction using the Seahorse Extracellular Flux Analyzer (Agilent). The described protocols detail the accurate measurement of ATP production rate in HepG2 cells after exposure to a panel of potentially toxic compounds. This assay measures changes in extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) as indicators of glycolysis and mitochondrial respiration-the two major energy-generating pathways in a cell. This assay provides a useful model to predict mitochondrial dysfunction-mediated DILI. © 2021 Wiley Periodicals LLC. Basic Protocol: Measurement of cellular ECAR, OCR, and ATP production in live HepG2 cells Support Protocol 1: Culturing and maintaining of HepG2 cells Support Protocol 2: Determining optimal cell density per well.

Propofol induces impairment of mitochondrial biogenesis through inhibiting the expression of peroxisome proliferator-activated receptor-γ coactivator-1α.

Propofol is a commonly used general anesthetic in patient care. Recent studies have shown that propofol has neurological side effects especially in young children, which raises a concern regarding the safety of its use. We explored the effects of the molecular mechanism of propofol on neuronal mitochondrial function in SH-SY5Y cells. Our results demonstrate that clinically relevant doses of propofol reduce the expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in a dose- and time-dependent manner. At a concentration of 2%, propofol suppresses the mitochondrial regulator nuclear respiratory factor 1 and mitochondrial transcription factor A and impairs neuronal mitochondrial biogenesis. These impairments involve reduction of mitochondrial mass and reduction of the ratio of mitochondrial to nuclear DNA as well as reduction of cytochrome C oxidase activity. Propofol treatment reduces intracellular adenosine triphosphate (ATP) production, the mitochondrial respiratory rate, and increases mitochondrial reactive oxygen species production, implying that it disturbs neuronal mitochondrial function. Overexpression of PGC-1α rescued propofol-induced reduced mitochondrial mass, ATP production, and respiratory rate, indicating that PGC-1α is the mediator of the effect of propofol on mitochondrial function. Finally, we demonstrate that propofol suppresses PGC-1α by inhibiting cAMP-response element bindingprotein (CREB) activation and promoting PKA RI expression, and the addition of cyclic adenosine monophosphate rescues propofol-mediated reduced PGC-1α. In conclusion, PGC-1α is the central mediator of propofol-induced impairment of mitochondrial biogenesis and neuronal mitochondrial dysfunction. Our study demonstrates the molecular mechanism behind propofol-induced neurotoxicity and provides valuable information regarding its side effects in clinical practice.

Adenosine Triphosphate Production of Muscle Mitochondria after Acute Exercise in Lean and Obese Humans.

Current evidence indicates mitochondrial dysfunction in humans with obesity. Acute exercise appears to enhance mitochondrial function in the muscle of nonobese humans, but its effects on mitochondrial function in muscle of humans with obesity are not known. We sought to determine whether acute aerobic exercise stimulates mitochondrial function in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in humans with obesity. We assessed maximal adenosine triphosphate production rate (MAPR) and citrate synthase (CS) activity in isolated SS and IMF mitochondria from subjects with body mass index < 27 kg·m (median age, 25 yr; interquartile range, 22-39 yr) and subjects with body mass index > 32 kg·m (median age, 29 yr; interquartile range, 20-39 yr) before and 3 h after a 45-min cycling exercise at an intensity corresponding to 65% HR reserve. The SS and IMF mitochondria were isolated from muscle biopsies using differential centrifugation. Maximal adenosine triphosphate production rate and CS activities were determined using luciferase-based and spectrophotometric enzyme-based assays, respectively. Exercise increased MAPR in IMF mitochondria in both nonobese subjects and subjects with obesity (P < 0.05), but CS-specific activity did not change in either group (P > 0.05). Exercise increased MAPR supported by complex II in SS mitochondria, in both groups (P < 0.05), but MAPR supported by complex I or palmitate did not increase by exercise in the subjects with obesity (P > 0.05). Citrate synthase-specific activity increased in SS mitochondria in response to exercise only in nonobese subjects (P < 0.05). In nonobese humans, acute aerobic exercise increases MAPR in both SS and IMF mitochondria. In humans with obesity, the exercise increases MAPR in IMF mitochondria, but this response is less evident in SS mitochondria.

Activin type IIB receptor blockade does not limit adenosine triphosphate supply in mouse skeletal muscle in Vivo.

Postnatal activin/myostatin type IIB receptor (ActRIIB) blockade increases skeletal muscle mass and strength but also increases muscle fatigability and impairs oxidative metabolism. The objective of this study was to determine in vivo whether this increased fatigability is due to energy supply limitation. The impact of 8-week ActRIIB blockade with soluble receptor (sActRIIB-Fc) on muscle function and adenosine triphosphate (ATP) fluxes was investigated noninvasively by using multimodal magnetic resonance and indirect calorimetry measurements in wild-type mice. Activin/myostatin type IIB receptor blockade reduced (-41%) the muscle apparent mitochondrial capacity and increased (+11%) the basal body energy expenditure. During a fatiguing exercise, ActRIIB blockade decreased both oxidative ATP production rate (-32%) and fatigue resistance (-36%), but these changes affected neither the total ATP production rate nor the contractile ATP cost. These findings demonstrate that the increased fatigability after ActRIIB blockade is not due to limitation in energy supply and/or disturbance in contractile ATP cost. Muscle Nerve 58:834-842, 2018.

Costs of being hungry in a fast‐paced world

Costs of being hungry in a fast‐paced world

Empagliflozin Increases Cardiac Energy Production in Diabetes: Novel Translational Insights Into the Heart Failure Benefits of SGLT2 Inhibitors

SGLT2 inhibitors have profound benefits on reducing heart failure and cardiovascular mortality in individuals with type 2 diabetes, although the mechanism(s) of this benefit remain poorly understood. Because changes in cardiac bioenergetics play a critical role in the pathophysiology of heart failure, the authors evaluated cardiac energy production and substrate use in diabetic mice treated with the SGTL2 inhibitor, empagliflozin. Empagliflozin treatment of diabetic db/db mice prevented the development of cardiac failure. Glycolysis, and the oxidation of glucose, fatty acids and ketones weremeasured in the isolated working heart perfused with 5 mmol/l glucose, 0.8 mmol/l palmitate, 0.5 mmol/l ß-hydroxybutyrate (ßOHB), and 500 μU/ml insulin. In vehicle-treated db/db mice, cardiac glucose oxidation rates were decreased by 61%, compared with control mice, but only by 43% in empagliflozin-treated diabetic mice. Interestingly, cardiac ketone oxidation rates in db/db mice decreased to 45% of the rates seen in control mice, whereas a similar decrease (43%) was seen in empagliflozin-treated db/db mice. Overall cardiac adenosine triphosphate (ATP) production rates decreased by 36% in db/db vehicle-treated hearts compared with control mice, with fatty acid oxidation providing 42%, glucose oxidation 26%, ketone oxidation 10%, and glycolysis 22% of ATP production in db/db mouse hearts. In empagliflozin-treated db/db mice, cardiac ATP production rates increased by 31% compared with db/db vehicle-treated mice, primarily due to a 61% increase in the contribution of glucose oxidation to energy production. Cardiac efficiency (cardiac work/O2 consumed) decreased by 28% in db/db vehicle-treated hearts, compared with control hearts, and empagliflozin did not increase cardiac efficiency per se. Because ketone oxidation was impaired in db/db mouse hearts, the authors determined whether this contributed to the decrease in cardiac efficiency seen in the db/db mouse hearts.Addition of 600 μmol/l ßOHB to db/db mouse hearts perfused with5mmol/l glucose, 0.8 mmol/l palmitate, and100 μU/ml insulin increased ketone oxidation rates, butdidnotdecrease either glucose oxidation or fatty acid oxidation rates. The presence of ketones did not increase cardiac efficiency, but did increase ATP production rates, due tothe additional contribution ofketoneoxidation to energy production. The authors conclude that empagliflozin treatment is associatedwithanincrease in ATP production, resulting in an enhanced energy status of the heart.

USMG5 Ashkenazi Jewish founder mutation impairs mitochondrial complex V dimerization and ATP synthesis.

Leigh syndrome is a frequent, heterogeneous pediatric presentation of mitochondrial oxidative phosphorylation (OXPHOS) disease, manifesting with psychomotor retardation and necrotizing lesions in brain deep gray matter. OXPHOS occurs at the inner mitochondrial membrane through the integrated activity of five protein complexes, of which complex V (CV) functions in a dimeric form to directly generate adenosine triphosphate (ATP). Mutations in several different structural CV subunits cause Leigh syndrome; however, dimerization defects have not been associated with human disease. We report four Leigh syndrome subjects from three unrelated Ashkenazi Jewish families harboring a homozygous splice-site mutation (c.87 + 1G>C) in a novel CV subunit disease gene, USMG5. The Ashkenazi population allele frequency is 0.57%. This mutation produces two USMG5 transcripts, wild-type and lacking exon 3. Fibroblasts from two Leigh syndrome probands had reduced wild-type USMG5 mRNA expression and undetectable protein. The mutation did not alter monomeric CV expression, but reduced both CV dimer expression and ATP synthesis rate. Rescue with wild-type USMG5 cDNA in proband fibroblasts restored USMG5 protein, increased CV dimerization and enhanced ATP production rate. These data demonstrate that a recurrent USMG5 splice-site founder mutation in the Ashkenazi Jewish population causes autosomal recessive Leigh syndrome by reduction of CV dimerization and ATP synthesis.

Bioinspired Assembly of Hierarchical Light‐Harvesting Architectures for Improved Photophosphorylation

AbstractMolecular assembly offers a bottom‐up way to construct biomimetic architectures with unique structures and properties. Although artificial photophosphorylation systems have long been developed, their microstructures have yet to achieve the sophisticated order and hierarchy of natural organisms. Herein, by utilizing principles in the natural plant leaves, it is shown that a biomimetic system with hierarchically ordered and compartmentalized structures, combining photosystem II (PSII) and adenosine triphosphate (ATP) synthase, can be obtained through template‐directed layer‐by‐layer assembly. Under light illumination, PSII in such a highly ordered light‐harvesting array, splits water to produce protons and electrons. Furthermore, a remarkable proton gradient is created across the covering ATP synthase‐reconstituted lipid membrane. As a consequence, highly efficient photophosphorylation is achieved. Outstandingly, the rate of ATP production in this hierarchical light‐harvesting architecture is enhanced 14 times, compared to that in the nature. This study paves a new way to assemble bioinspired systems with enhanced solar‐to‐chemical energy conversion efficiency.

Plasma Amino Acids Stimulate Uncoupled Respiration of Muscle Subsarcolemmal Mitochondria in Lean but Not Obese Humans.

Obesity is associated with mitochondrial dysfunction in skeletal muscle. Increasing the plasma amino acid (AA) concentrations stimulates mitochondrial adenosine triphosphate (ATP) production in lean individuals. To determine whether acute elevation in plasma AAs enhances muscle mitochondrial respiration and ATP production in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in obese adults. Assessment of SS and IMF mitochondrial function during saline (i.e., control) and AA infusions. Eligible participants were healthy lean (body mass index, <25 kg/m2; age, 37 ± 3 years; n = 10) and obese (body mass index >30 kg/m2; age 35 ± 3 years; n = 11) subjects. Single trial of saline infusion followed by AA infusion. SS and IMF mitochondria were isolated from muscle biopsies collected at the end of the saline and AA infusions. Mitochondrial respiration and ATP production. AA infusion increased adenosine 5'-diphosphate (ADP)-stimulated respiration and ATP production rates of SS mitochondria in the lean (P < 0.05), but not obese, subjects. Furthermore, AA infusion increased the uncoupled (i.e., non-ADP-stimulated) respiration of SS mitochondria in the lean subjects only (P < 0.05). AA infusion had no effect on any of these parameters in IMF mitochondria in either lean or obese subjects (P > 0.05). Increasing the plasma AA concentrations enhances the capacity for respiration and ATP production of muscle SS, but not IMF, mitochondria in lean individuals, in parallel with increases in uncoupled respiration. However, neither of these parameters increases in muscle SS or IMF mitochondria in obese individuals.