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Proceedings of the National Academy of... Jul 2022The mitochondrial electron transport chain maintains the proton motive force that powers adenosine triphosphate (ATP) synthesis. The energy for this process comes from...
The mitochondrial electron transport chain maintains the proton motive force that powers adenosine triphosphate (ATP) synthesis. The energy for this process comes from oxidation of reduced nicotinamide adenine dinucleotide (NADH) and succinate, with the electrons from this oxidation passed via intermediate carriers to oxygen. Complex IV (CIV), the terminal oxidase, transfers electrons from the intermediate electron carrier cytochrome to oxygen, contributing to the proton motive force in the process. Within CIV, protons move through the K and D pathways during turnover. The former is responsible for transferring two protons to the enzyme's catalytic site upon its reduction, where they eventually combine with oxygen and electrons to form water. CIV is the main site for respiratory regulation, and although previous studies showed that steroid binding can regulate CIV activity, little is known about how this regulation occurs. Here, we characterize the interaction between CIV and steroids using a combination of kinetic experiments, structure determination, and molecular simulations. We show that molecules with a sterol moiety, such as glyco-diosgenin and cholesteryl hemisuccinate, reversibly inhibit CIV. Flash photolysis experiments probing the rapid equilibration of electrons within CIV demonstrate that binding of these molecules inhibits proton uptake through the K pathway. Single particle cryogenic electron microscopy (cryo-EM) of CIV with glyco-diosgenin reveals a previously undescribed steroid binding site adjacent to the K pathway, and molecular simulations suggest that the steroid binding modulates the conformational dynamics of key residues and proton transfer kinetics within this pathway. The binding pose of the sterol group sheds light on possible structural gating mechanisms in the CIV catalytic cycle.
Topics: Animals; Binding Sites; Catalytic Domain; Cattle; Diosgenin; Electron Transport; Electron Transport Complex IV; Oxidation-Reduction; Oxygen; Protein Conformation; Protons; Steroids; Sterols
PubMed: 35858451
DOI: 10.1073/pnas.2205228119 -
BMC Pregnancy and Childbirth Sep 2022Assessing the severity of transferred neonates at admission can improve resource allocation. This study evaluated the role of TOPS (illness severity score including... (Observational Study)
Observational Study
BACKGROUND
Assessing the severity of transferred neonates at admission can improve resource allocation. This study evaluated the role of TOPS (illness severity score including temperature, oxygen saturation, skin perfusion and blood sugar) in predicting mortality in neonates transferred by ambulance in a low-resource setting.
METHODS
The study was conducted at Beira Central Hospital (Mozambique). Infants who were transferred by ambulance to the Neonatal Intensive Care Unit between 16th June and 16th October 2021 were included. The association between TOPS and mortality was investigated with a logistic regression model. Receiver-operating characteristics (ROC) curve was derived for TOPS; area under the ROC curve, sensitivity and specificity were calculated.
RESULTS
In-transport mortality was 2/198 (1.0%) and in-hospital mortality was 75/196 (38.3%). Median gestational age and birthweight were 38 weeks and 2600 g. Main causes of admission were asphyxia (29.3%), prematurity (25.3%) and sepsis (22.7%). Hypothermia and oxygen desaturation at admission were 75.8% and 32.3%. TOPS ≥ 1 was associated with increased mortality risk (odds ratio 7.06. 95% confidence interval 1.90 to 45.82), with 0.97 sensitivity and 0.26 specificity.
CONCLUSIONS
The high mortality rate calls for interventions and quality initiative studies to improve the transfer process and the conditions at admission. TOPS can be used to identify neonates at risk of mortality and concentrate efforts of health care providers. Interventions preventing hypothermia and oxygen desaturation should be implemented in pre-transport stabilization and care during transport.
Topics: Ambulances; Blood Glucose; Cyclic N-Oxides; Humans; Hypothermia; Infant; Infant, Newborn; Oxygen; Prognosis; Retrospective Studies
PubMed: 36151540
DOI: 10.1186/s12884-022-05060-9 -
Nature Mar 2021Mitochondria are specialized eukaryotic organelles that have a dedicated function in oxygen respiration and energy production. They evolved about 2 billion years ago...
Mitochondria are specialized eukaryotic organelles that have a dedicated function in oxygen respiration and energy production. They evolved about 2 billion years ago from a free-living bacterial ancestor (probably an alphaproteobacterium), in a process known as endosymbiosis. Many unicellular eukaryotes have since adapted to life in anoxic habitats and their mitochondria have undergone further reductive evolution. As a result, obligate anaerobic eukaryotes with mitochondrial remnants derive their energy mostly from fermentation. Here we describe 'Candidatus Azoamicus ciliaticola', which is an obligate endosymbiont of an anaerobic ciliate and has a dedicated role in respiration and providing energy for its eukaryotic host. 'Candidatus A. ciliaticola' contains a highly reduced 0.29-Mb genome that encodes core genes for central information processing, the electron transport chain, a truncated tricarboxylic acid cycle, ATP generation and iron-sulfur cluster biosynthesis. The genome encodes a respiratory denitrification pathway instead of aerobic terminal oxidases, which enables its host to breathe nitrate instead of oxygen. 'Candidatus A. ciliaticola' and its ciliate host represent an example of a symbiosis that is based on the transfer of energy in the form of ATP, rather than nutrition. This discovery raises the possibility that eukaryotes with mitochondrial remnants may secondarily acquire energy-providing endosymbionts to complement or replace functions of their mitochondria.
Topics: Adenosine Triphosphate; Anaerobiosis; Bacteria; Biological Evolution; Cell Respiration; Ciliophora; Citric Acid Cycle; Denitrification; Electron Transport; Energy Metabolism; Genome, Bacterial; Host Microbial Interactions; Mitochondria; Nitrates; Oxygen; Phylogeny; Symbiosis
PubMed: 33658719
DOI: 10.1038/s41586-021-03297-6 -
Nucleic Acids Research Jul 2019Post-transcriptional regulons coordinate the expression of groups of genes in eukaryotic cells, yet relatively few have been characterized. Parasitic trypanosomatids are... (Comparative Study)
Comparative Study
Post-transcriptional regulons coordinate the expression of groups of genes in eukaryotic cells, yet relatively few have been characterized. Parasitic trypanosomatids are particularly good models for studies on such mechanisms because they exhibit almost exclusive polycistronic, and unregulated, transcription. Here, we identify the Trypanosoma brucei ZC3H39/40 RNA-binding proteins as regulators of the respiratome; the mitochondrial electron transport chain (complexes I-IV) and the FoF1-ATP synthase (complex V). A high-throughput RNAi screen initially implicated both ZC3H proteins in variant surface glycoprotein (VSG) gene silencing. This link was confirmed and both proteins were shown to form a cytoplasmic ZC3H39/40 complex. Transcriptome and mRNA-interactome analyses indicated that the impact on VSG silencing was indirect, while the ZC3H39/40 complex specifically bound and stabilized transcripts encoding respiratome-complexes. Quantitative proteomic analyses revealed specific positive control of >20 components from complexes I, II and V. Our findings establish a link between the mitochondrial respiratome and VSG gene silencing in bloodstream form T. brucei. They also reveal a major respiratome regulon controlled by the conserved trypanosomatid ZC3H39/40 RNA-binding proteins.
Topics: Adaptation, Physiological; Amino Acid Sequence; Cell Respiration; Electron Transport; Gene Expression Regulation; Gene Silencing; Humans; Mitochondria; Parasitemia; Protein Interaction Mapping; Proteomics; Proton-Translocating ATPases; Protozoan Proteins; RNA Interference; RNA-Binding Proteins; Regulon; Sequence Alignment; Sequence Homology, Amino Acid; Transcriptome; Trypanosoma brucei brucei; Trypanosomiasis, African; Variant Surface Glycoproteins, Trypanosoma
PubMed: 31127277
DOI: 10.1093/nar/gkz455 -
In Vivo (Athens, Greece) 2023This study aimed to investigate the effects of acupuncture treatment through the ear acupoints on transport stress in experimental microminipigs.
BACKGROUND/AIM
This study aimed to investigate the effects of acupuncture treatment through the ear acupoints on transport stress in experimental microminipigs.
MATERIALS AND METHODS
Experiment 1: Six animals were equally divided into two groups (Control and Treatment). In the treatment group, before transportation (6 h; vehicle and plane), short, ultrathin circular transdermal needles were applied to locations corresponding to the acupoints on the apical area of both ears. Peripheral blood samples were collected from the cranial vena cava 2 days before and immediately after transportation. Blood stress markers, biochemistry indicators, and oxidative stress levels were examined. Experiment 2 (follow-up study: diarrhea incidence after transportation): Diarrhea incidence after transportation in the control and treatment groups was investigated.
RESULTS
Experiment 1: Transport stress induced an increase in blood cortisol, serum amyloid A (SAA), glucose, non-esterified fatty acid, and derivatives of reactive oxygen metabolites (d-ROMs) and decreased the biological antioxidant potential (BAP)/d-ROMs ratio yet did not affect BAP. Acupuncture suppressed the increases in SAA and d-ROMs values and the decrease in BAP/d-ROMs ratio. Experiment 2: The total diarrhea incidence was 25% in the control group, whereas diarrhea was not observed in the treatment group.
CONCLUSION
Acupuncture treatment suppresses hypothalamic-pituitary-adrenal function and, as a result, reduces transport stress without affecting the suppression of the central catecholaminergic system. Acupuncture treatment for transport stress can improve animal welfare.
Topics: Animals; Acupuncture Points; Follow-Up Studies; Oxidative Stress; Antioxidants; Acupuncture Therapy; Oxygen; Diarrhea
PubMed: 37652514
DOI: 10.21873/invivo.13307 -
International Journal of Molecular... Feb 2022Adaptive mechanisms that facilitate intestinal colonization by the human microbiota, including , may be better understood by analyzing the physiology and gene expression...
Combined Transcriptomic and Proteomic Profiling of under Microaerobic versus Aerobic Conditions: The Multifaceted Roles of Noncoding Small RNAs and Oxygen-Dependent Sensing in Global Gene Expression Control.
Adaptive mechanisms that facilitate intestinal colonization by the human microbiota, including , may be better understood by analyzing the physiology and gene expression of bacteria in low-oxygen environments. We used high-throughput transcriptomics and proteomics to compare the expression profiles of grown under aerobic versus microaerobic conditions. Clustering of high-abundance transcripts under microaerobiosis highlighted genes controlling acid-stress adaptation (, , and operons), cell adhesion/biofilm formation ( and operons), electron transport (), oligopeptide transport (), and anaerobic respiration/fermentation ( and operons). In contrast, downregulated genes were involved in iron transport (, and operons), iron-sulfur cluster assembly ( and operons), aerobic respiration ( and operons), and de novo nucleotide synthesis (). Additionally, quantitative proteomics showed that the products (proteins) of these high- or low-abundance transcripts were expressed consistently. Our findings highlight interrelationships among energy production, carbon metabolism, and iron homeostasis. Moreover, we have identified and validated a subset of differentially expressed noncoding small RNAs (i.e., CsrC, RyhB, RprA and GcvB), and we discuss their regulatory functions during microaerobic growth. Collectively, we reveal key changes in gene expression at the transcriptional and post-transcriptional levels that sustain growth when oxygen levels are low.
Topics: Anaerobiosis; Escherichia coli; Escherichia coli Proteins; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Humans; Iron; Membrane Proteins; Oxygen; Proteomics; RNA, Untranslated; Transcriptome
PubMed: 35269716
DOI: 10.3390/ijms23052570 -
Mitochondrion Jul 2020The biological function of plant mitochondrial uncoupling proteins (pUCPs) has been a matter of considerable controversy. For example, the pUCP capacity to uncouple... (Review)
Review
The biological function of plant mitochondrial uncoupling proteins (pUCPs) has been a matter of considerable controversy. For example, the pUCP capacity to uncouple respiration from ATP synthesis in vivo has never been fully acknowledged, in contrast to the mammalian UCP1 (mUCP1) role in uncoupling respiration-mediated thermogenesis. Interestingly, both pUCPs and mUCPs have been associated with stress response and metabolic perturbations. Some central questions that remain are how pUCPs and mUCPs compare in biochemical properties, molecular structure and cell biology under physiological and metabolically perturbed conditions. This review takes advantage of the large amount of data available for mUCPs to review the biochemical properties, 3D structure models and potential physiological roles of pUCPs during plant development and response to stress. The biochemical properties and structure of pUCPs are revisited in light of the recent findings that pUCPs catalyse the transport of metabolites across the mitochondrial inner membrane and the resolved mUCP2 protein structure. Additionally, transcriptional regulation and co-expression networks of UCP orthologues across species are analysed, taking advantage of publicly available curated experimental datasets. Taking these together, the biological roles of pUCPs are analysed in the context of their potential roles in thermogenesis, ROS production, cell signalling and the regulation of plant cellular bioenergetics. Finally, pUCPs biological function is discussed in the context of their potential role in protecting against environmental stresses.
Topics: Energy Metabolism; Gene Expression Regulation, Plant; Mitochondrial Uncoupling Proteins; Models, Molecular; Plant Development; Plant Proteins; Plants; Protein Conformation; Stress, Physiological
PubMed: 32439620
DOI: 10.1016/j.mito.2020.05.001 -
Biochemical Society Transactions Dec 2020In fluctuating environmental conditions, organisms must modulate their bioenergetic production in order to maintain cellular homeostasis for optimal fitness.... (Review)
Review
In fluctuating environmental conditions, organisms must modulate their bioenergetic production in order to maintain cellular homeostasis for optimal fitness. Mitochondria are hubs for metabolite and energy generation. Mitochondria are also highly dynamic in their function: modulating their composition, size, density, and the network-like architecture in relation to the metabolic demands of the cell. Here, we review the recent research on the post-transcriptional regulation of mitochondrial composition focusing on mRNA localization, mRNA translation, protein import, and the role that dynamic mitochondrial structure may have on these gene expression processes. As mitochondrial structure and function has been shown to be very important for age-related processes, including cancer, metabolic disorders, and neurodegeneration, understanding how mitochondrial composition can be affected in fluctuating conditions can lead to new therapeutic directions to pursue.
Topics: Animals; Cell Cycle; Cell Respiration; Cricetinae; Environment; Fermentation; Fungal Proteins; Gene Expression Regulation; Genes, Fungal; HeLa Cells; Homeostasis; Humans; Mitochondria; Mitochondrial Proteins; Myocardium; Neoplasms; Osteosarcoma; Oxygen Consumption; Protein Transport; RNA, Messenger; Saccharomyces cerevisiae
PubMed: 33245320
DOI: 10.1042/BST20200250 -
Oxidative Medicine and Cellular... 2021Photobiomodulation with 808 nm laser light electively stimulates Complexes III and IV of the mitochondrial respiratory chain, while Complexes I and II are not...
Photobiomodulation with 808 nm laser light electively stimulates Complexes III and IV of the mitochondrial respiratory chain, while Complexes I and II are not affected. At the wavelength of 1064 nm, Complexes I, III, and IV are excited, while Complex II and some mitochondrial matrix enzymes seem to be not receptive to photons at that wavelength. Complex IV was also activated by 633 nm. The mechanism of action of wavelengths in the range 900-1000 nm on mitochondria is less understood or not described. Oxidative stress from reactive oxygen species (ROS) generated by mitochondrial activity is an inescapable consequence of aerobic metabolism. The antioxidant enzyme system for ROS scavenging can keep them under control. However, alterations in mitochondrial activity can cause an increment of ROS production. ROS and ATP can play a role in cell death, cell proliferation, and cell cycle arrest. In our work, bovine liver isolated mitochondria were irradiated for 60 sec, in continuous wave mode with 980 nm and powers from 0.1 to 1.4 W (0.1 W increment at every step) to generate energies from 6 to 84 J, fluences from 7.7 to 107.7 J/cm, power densities from 0.13 to 1.79 W/cm, and spot size 0.78 cm. The control was equal to 0 W. The activity of the mitochondria's complexes, Krebs cycle enzymes, ATP production, oxygen consumption, generation of ROS, and oxidative stress were detected. Lower powers (0.1-0.2 W) showed an inhibitory effect; those that were intermediate (0.3-0.7 W) did not display an effect, and the higher powers (0.8-1.1 W) induced an increment of ATP synthesis. Increasing the power (1.2-1.4 W) recovered the ATP production to the control level. The interaction occurred on Complexes III and IV, as well as ATP production and oxygen consumption. Results showed that 0.1 W uncoupled the respiratory chain and induced higher oxidative stress and drastic inhibition of ATP production. Conversely, 0.8 W kept mitochondria coupled and induced an increase of ATP production by increments of Complex III and IV activities. An augmentation of oxidative stress was also observed, probably as a consequence of the increased oxygen consumption and mitochondrial isolation experimental conditions. No effect was observed using 0.5 W, and no effect was observed on the enzymes of the Krebs cycle.
Topics: Animals; Cattle; Cell Respiration; Electron Transport Complex III; Electron Transport Complex IV; Female; Isocitrate Dehydrogenase; Lasers, Semiconductor; Lipid Peroxidation; Low-Level Light Therapy; Malate Dehydrogenase; Male; Mitochondria; Oxidative Phosphorylation; Oxidative Stress; Proton-Translocating ATPases; Reactive Oxygen Species; Superoxides; Temperature
PubMed: 33763170
DOI: 10.1155/2021/6626286 -
PLoS Biology Oct 2022The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily...
The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily revealed by staining for cytochrome oxidase-the last enzyme in the respiratory electron transport chain located in the inner mitochondrial membrane. It has been hypothesized that a high-density band of cytochrome oxidase in cortical layer IV reflects higher oxygen consumption under baseline (unstimulated) conditions. Here, we tested the above hypothesis using direct measurements of the partial pressure of O2 (pO2) in cortical tissue by means of 2-photon phosphorescence lifetime microscopy (2PLM). We revisited our previously developed method for extraction of the cerebral metabolic rate of O2 (CMRO2) based on 2-photon pO2 measurements around diving arterioles and applied this method to estimate baseline CMRO2 in awake mice across cortical layers. To our surprise, our results revealed a decrease in baseline CMRO2 from layer I to layer IV. This decrease of CMRO2 with cortical depth was paralleled by an increase in tissue oxygenation. Higher baseline oxygenation and cytochrome density in layer IV may serve as an O2 reserve during surges of neuronal activity or certain metabolically active brain states rather than reflecting baseline energy needs. Our study provides to our knowledge the first quantification of microscopically resolved CMRO2 across cortical layers as a step towards better understanding of brain energy metabolism.
Topics: Animals; Mice; Electron Transport Complex IV; Oxygen Consumption; Oxygen; Cerebral Cortex; Brain; Cerebrovascular Circulation
PubMed: 36301995
DOI: 10.1371/journal.pbio.3001440