Oxidative Phosphorylation Proteins Research Articles

Mitonuclear compatibility is maintained despite relaxed selection on male mitochondrial DNA in bivalves with doubly uniparental inheritance.

Mitonuclear coevolution is common in eukaryotes, but bivalve lineages that have doubly uniparental inheritance (DUI) of mitochondria may be an interesting example. In this system, females transmit mtDNA (F mtDNA) to all offspring, while males transmit a different mtDNA (M mtDNA) solely to their sons. Molecular evolution and functional data suggest oxidative phosphorylation (OXPHOS) genes encoded in M mtDNA evolve under relaxed selection due to their function being limited to sperm only (vs. all other tissues for F mtDNA). This has led to the hypothesis that mitonuclear coevolution is less important for M mtDNA. Here, we use comparative phylogenetics, transcriptomics, and proteomics to understand mitonuclear interactions in DUI bivalves. We found nuclear OXPHOS proteins coevolve and maintain compatibility similarly with both F and M mtDNA OXPHOS proteins. Mitochondrial recombination did not influence mitonuclear compatibility and nuclear-encoded OXPHOS genes were not upregulated in tissues with M mtDNA to offset dysfunction. Our results support that selection maintains mitonuclear compatibility with F and M mtDNA despite relaxed selection on M mtDNA. Strict sperm transmission, lower effective population size, and higher mutation rates may explain the evolution of M mtDNA. Our study highlights that mitonuclear coevolution and compatibility may be broad features of eukaryotes.

Central dogma rates in human mitochondria.

In human cells, the nuclear and mitochondrial genomes engage in a complex interplay to produce dual-encoded oxidative phosphorylation (OXPHOS) complexes. The coordination of these dynamic gene expression processes is essential for producing matched amounts of OXPHOS protein subunits. This review focuses on our current understanding of the mitochondrial central dogma rates, highlighting the striking differences in gene expression rates between mitochondrial and nuclear genes. We synthesize a coherent model of mitochondrial gene expression kinetics, highlighting the emerging principles and emphasizing where more precise measurements would be beneficial. Such an understanding is pivotal for grasping the unique aspects of mitochondrial function and its role in cellular energetics, and it has profound implications for aging, metabolic disorders, and neurodegenerative diseases.

Illuminating mitochondrial translation through mouse models.

Mitochondria are hubs of metabolic activity with a major role in ATP conversion by oxidative phosphorylation (OXPHOS). The mammalian mitochondrial genome encodes 11 mRNAs encoding 13 OXPHOS proteins along with 2 rRNAs and 22 tRNAs, that facilitate their translation on mitoribosomes. Maintaining the internal production of core OXPHOS subunits requires modulation of the mitochondrial capacity to match the cellular requirements and correct insertion of particularly hydrophobic proteins into the inner mitochondrial membrane. The mitochondrial translation system is essential for energy production and defects result in severe, phenotypically diverse diseases, including mitochondrial diseases that typically affect postmitotic tissues with high metabolic demands. Understanding the complex mechanisms that underlie the pathologies of diseases involving impaired mitochondrial translation is key to tailoring specific treatments and effectively targeting the affected organs. Disease mutations have provided a fundamental, yet limited, understanding of mitochondrial protein synthesis, since effective modification of the mitochondrial genome has proven challenging. However, advances in next generation sequencing, cryoelectron microscopy, and multi-omic technologies have revealed unexpected and unusual features of the mitochondrial protein synthesis machinery in the last decade. Genome editing tools have generated unique models that have accelerated our mechanistic understanding of mitochondrial translation and its physiological importance. Here we review the most recent mouse models of disease pathogenesis caused by defects in mitochondrial protein synthesis and discuss their value for preclinical research and therapeutic development.

Ferritinophagy mediates adaptive resistance to EGFR tyrosine kinase inhibitors in non-small cell lung cancer

Osimertinib (Osi) is a widely used epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). However, the emergence of resistance is inevitable, partly due to the gradual evolution of adaptive resistant cells during initial treatment. Here, we find that Osi treatment rapidly triggers adaptive resistance in tumor cells. Metabolomics analysis reveals a significant enhancement of oxidative phosphorylation (OXPHOS) in Osi adaptive-resistant cells. Mechanically, Osi treatment induces an elevation of NCOA4, a key protein of ferritinophagy, which maintains the synthesis of iron-sulfur cluster (ISC) proteins of electron transport chain and OXPHOS. Additionally, active ISC protein synthesis in adaptive-resistant cells significantly increases the sensitivity to copper ions. Combining Osi with elesclomol, a copper ion ionophore, significantly increases the efficacy of Osi, with no additional toxicity. Altogether, this study reveals the mechanisms of NCOA4-mediated ferritinophagy in Osi adaptive resistance and introduces a promising new therapy of combining copper ionophores to improve its initial efficacy.

Starvation-Induced Changes to the Midgut Proteome and Neuropeptides in Manduca sexta.

Starvation is a complex physiological state that induces changes in protein expression to ensure survival. The insect midgut is sensitive to changes in dietary content as it is at the forefront of communicating information about incoming nutrients to the body via hormones. Therefore, a DIA proteomics approach was used to examine starvation physiology and, specifically, the role of midgut neuropeptide hormones in a representative lepidopteran, Manduca sexta. Proteomes were generated from midguts of M. sexta fourth-instar caterpillars, starved for 24 h and 48 h, and compared to fed controls. A total of 3047 proteins were identified, and 854 of these were significantly different in abundance. KEGG analysis revealed that metabolism pathways were less abundant in starved caterpillars, but oxidative phosphorylation proteins were more abundant. In addition, six neuropeptides or related signaling cascade proteins were detected. Particularly, neuropeptide F1 (NPF1) was significantly higher in abundance in starved larvae. A change in juvenile hormone-degrading enzymes was also detected during starvation. Overall, our results provide an exploration of the midgut response to starvation in M. sexta and validate DIA proteomics as a useful tool for quantifying insect midgut neuropeptide hormones.

Role of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1a) in regulating mitochondrial energy effciency in skeletal muscle

Previous studies have shown that exercise training improves mitochondrial energy effciency in skeletal muscle, but the molecular mechanism is unclear. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1a) is a transcriptional co-activator that coordinately regulates exercise-induced mitochondrial biogenesis and quality control. This study aimed to test the hypothesis that PGC-1a is involved in the improvement of mitochondrial energy effciency in skeletal muscle by using a skeletal muscle-specific PGC-1a overexpression mouse model. Ten to twelve-week-old skeletal muscle-specific PGC-1a transgenic mice (MCK-PGC-1a) and their wildtype littermates (WT) were used. Protein levels of oxidative phosphorylation (OXPHOS) subunits in skeletal muscle were determined by Western blot analysis. The rate of O2 consumption ( JO2) and ATP production ( JATP) in isolated mitochondria from skeletal muscle were evaluated using high-resolution respirometry and fluorometry, respectively, and mitochondrial energy effciency (ATP produced per O2 consumed, or P/O) was calculated. Overexpression of PGC-1a in skeletal muscle did not affect body weights and muscle weights. Consistent with previous studies, MCK-PGC-1a mice had significantly higher OXPHOS protein content than WT mice. On the other hand, JO2, JATP, and P/O in isolated muscle mitochondria were not different between genotypes. Our results suggest that exercise training-induced improvement in muscle mitochondrial energy effciency is not mediated by PGC-1a. This research is supported by NIH grant DK107397 to K.F. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Oxidative Stress-Mediated RUNX3 Mislocalization Occurs Via Jun Activation Domain-Binding Protein 1 and Histone Modification.

Runt domain transcription factor 3 (RUNX3) suppresses many different cancer types and is disabled by mutations, epigenetic repression, or cytoplasmic mislocalization. In this study, we investigated whether oxidative stress is associated with RUNX3 accumulation from the nucleus to the cytoplasm in terms of histone modification. Oxidative stress elevated histone deacetylase (HDAC) level and lowered that of histone acetyltransferase. In addition, oxidative stress decreased the expression of mixed lineage leukemia (MLL), a histone methyltransferase, but increased the expression of euchromatic histone-lysine N-methyltransferase 2 (EHMT2/G9a), which is also a histone methyltransferase. Moreover, oxidative stress-induced RUNX3 phosphorylation, Src activation, and Jun activation domain-binding protein 1 (JAB1) expression were inhibited by knockdown of HDAC and G9a, restoring the nuclear localization of RUNX3 under oxidative stress. Cytoplasmic RUNX3 localization was followed by oxidative stress-induced histone modification, activated Src along with RUNX3 phosphorylation, and induction of JAB1, resultingin RUNX3 inactivation.

Repeated sprint training in hypoxia induces specific skeletal muscle adaptations through S100A protein signaling.

Athletes increasingly engage in repeated sprint training consisting in repeated short all-out efforts interspersed by short recoveries. When performed in hypoxia (RSH), it may lead to greater training effects than in normoxia (RSN); however, the underlying molecular mechanisms remain unclear. This study aimed at elucidating the effects of RSH on skeletal muscle metabolic adaptations as compared to RSN. Sixteen healthy young men performed nine repeated sprint training sessions in either normoxia (FIO2 = 0.209, RSN, n = 7) or normobaric hypoxia (FIO2 = 0.136, RSH, n = 9). Before and after the training period, exercise performance was assessed by using repeated sprint ability (RSA) and Wingate tests. Vastus lateralis muscle biopsies were performed to investigate muscle metabolic adaptations using proteomics combined with western blot analysis. Similar improvements were observed in RSA and Wingate tests in both RSN and RSH groups. At the muscle level, RSN and RSH reduced oxidative phosphorylation protein content but triggered an increase in mitochondrial biogenesis proteins. Proteomics showed an increase in several S100A family proteins in the RSH group, among which S100A13 most strongly. We confirmed a significant increase in S100A13 protein by western blot in RSH, which was associated with increased Akt phosphorylation and its downstream targets regulating protein synthesis. Altogether our data indicate that RSH may activate an S100A/Akt pathway to trigger specific adaptations as compared to RSN.

Capsaicin induces ATP-dependent thermogenesis via the activation of TRPV1/β3-AR/α1-AR in 3T3-L1 adipocytes and mouse model

Capsaicin (CAP) is a natural bioactive compound in chili pepper that activates the transient receptor potential vanilloid subfamily 1 (TRPV1) and is known to stimulate uncoupling protein 1 (UCP1)-dependent thermogenesis. However, its effect on ATP-dependent thermogenesis remains unknown. In this study, we employed qRT-PCR, immunoblot, staining method, and assay kit to investigate the role of CAP on ATP-dependent thermogenesis and its modulatory roles on the TRPV1, β3-adrenergic receptor (β3-AR), and α1-AR using in vitro and in vivo models. The studies showed that CAP treatment in high-fat diet-induced obese mice resulted in lower body weight gain and elevated ATP-dependent thermogenic effectors' protein and gene expression through ATP-consuming calcium and creatine futile cycles. In both in vitro and in vivo experiments, CAP treatment elevated the protein and gene expressions of sarcoendoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2), ryanodine receptor 2 (RYR2), creatine kinase B (CKB), and creatine kinase mitochondrial 2 (CKMT2) mediated by the activation of β3-AR, α1-AR, and TRPV1. Our study showed that CAP increased intracellular Ca2+ levels and the expression of voltage-dependent anion channel (VDAC) and mitochondrial calcium uniporter (MCU) which indicates that increased mitochondrial Ca2+ levels lead to increased expression of oxidative phosphorylation protein complexes as a result of ATP-futile cycle activation. A mechanistic study in 3T3-L1 adipocytes revealed that CAP induces UCP1- and ATP-dependent thermogenesis mediated by the β3-AR/PKA/p38MAPK/ERK as well as calcium-dependent α1-AR/TRPV1/CaMKII/AMPK/SIRT1 pathway. Taken together, we identified CAP's novel functional and modulatory roles in UCP1- and ATP-dependent thermogenesis, which is important for developing therapeutic strategies for combating obesity and metabolic diseases.

Abstract 1158: Spatially resolved cell profiling unveils tumor metabolic states associated with immunotherapy response in NSCLC

Abstract Background. Only a subset of non-small cell lung cancer (NSCLC) patients benefit from immune checkpoint inhibitors (ICIs). Thus, there is a clinical need to develop predictive biomarkers for ICIs. Deeper insights from the tumor microenvironment (TME) can lead to identification of spatial features associated with clinical responses to immune checkpoint inhibitors (ICI). In this study, we investigated functional profiles within cell subtypes as a surrogate for ICI clinical endpoints. Methods. We profiled a retrospective cohort of 39 NSCLC tissue cores from 27 patients treated with ICI, using highly multiplexed immunofluorescence (mIF) stained by the Phenocycler Fusion platform (Akoya Biosciences) capturing 45 proteins. Utilizing a deep learning based multiplex imaging analysis pipeline, cells were classified to 15 cell types by known marker expression and were further subclassified by unsupervised clustering. Cells were assigned to the tumor area or TME and more than 1000 spatial features were calculated based on cell type, marker positivity, and area assignments, and were compared between responders and non-responders to ICI therapy using Fisher’s exact and logrank tests. Results. Unsupervised cell subtyping of the 15 cell types identified 43 cell subsets, which were mostly segregated by their metabolism and activation status. Interestingly, all lymphocytes showed a similar pattern of clustering resulting in two clusters of metabolically active and inactive cells. The most significantly differentially expressed proteins between these cell types were oxidative phosphorylation proteins such as CS, SDHA and ATPA5, and other metabolic enzymes such as HK1, GLUT1 and LDHA. We found a direct connection between metabolic state, effector functions and tissue localization as the metabolically active lymphocytes exhibited higher levels of PD-1, MHC class I and II and CD44 positivity, and were more abundant within tumor infiltrating lymphocytes (TILs) and tertiary lymphoid structures (TLS). Unsupervised clustering of tumor cells demonstrated segregation to three main metabolic states - OXPHOS+, OXPHOS- and a third cluster (PPP+) which was characterized by upregulation of ASCT2, a glutamine transporter, as well as pNRF2 and G6PD, regulators of the pentose phosphate pathway. These cells also exhibited higher proliferation rate and CD44, a tumor stemness marker, positivity. All tumors with high content of PPP+ tumor cells (>40%) were resistant to PD-1 blockade (0/8 vs. 10/18 response rate in other tumors, p=0.009) and showed reduced overall survival (OS) rates (median OS of 27.6 vs 90.3 months, p=0.02). Conclusions. Taken together, this study reveals connections between metabolic states, effector functions, and immunotherapy outcome and contributes to the evolving landscape of predictive biomarkers for ICI therapies. Citation Format: James Monkman, Rotem Czertok, Shai Bookstein, Becky Arbiv, Yuval Shachaf, Ron Elran, Kenneth Bloom, Oscar Puig, Ken O'Byrne, Ettai Markovits, Arutha Kulasinghe. Spatially resolved cell profiling unveils tumor metabolic states associated with immunotherapy response in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1158.

A stagewise response to mitochondrial dysfunction in mitochondrial DNA maintenance disorders

Mitochondrial DNA (mtDNA) deletions which clonally expand in skeletal muscle of patients with mtDNA maintenance disorders, impair mitochondrial oxidative phosphorylation dysfunction. Previously we have shown that these mtDNA deletions arise and accumulate in perinuclear mitochondria causing localised mitochondrial dysfunction before spreading through the muscle fibre. We believe that mito-nuclear signalling is a key contributor in the accumulation and spread of mtDNA deletions, and that knowledge of how muscle fibres respond to mitochondrial dysfunction is key to our understanding of disease mechanisms.To understand the contribution of mito-nuclear signalling to the spread of mitochondrial dysfunction, we use imaging mass cytometry. We characterise the levels of mitochondrial Oxidative Phosphorylation proteins alongside a mitochondrial mass marker, in a cohort of patients with mtDNA maintenance disorders. Our expanded panel included protein markers of key signalling pathways, allowing us to investigate cellular responses to different combinations of oxidative phosphorylation dysfunction and ragged red fibres.We find combined Complex I and IV deficiency to be most common. Interestingly, in fibres deficient for one or more complexes, the remaining complexes are often upregulated beyond the increase of mitochondrial mass typically observed in ragged red fibres. We further find that oxidative phosphorylation deficient fibres exhibit an increase in the abundance of proteins involved in proteostasis, e.g. HSP60 and LONP1, and regulation of mitochondrial metabolism (including oxidative phosphorylation and proteolysis, e.g. PHB1). Our analysis suggests that the cellular response to mitochondrial dysfunction changes depending on the combination of deficient oxidative phosphorylation complexes in each fibre.

Mevalonate kinase-deficient THP-1 cells show a disease-characteristic pro-inflammatory phenotype.

Bi-allelic pathogenic variants in the MVK gene, which encodes mevalonate kinase (MK), an essential enzyme in isoprenoid biosynthesis, cause the autoinflammatory metabolic disorder mevalonate kinase deficiency (MKD). We generated and characterized MK-deficient monocytic THP-1 cells to identify molecular and cellular mechanisms that contribute to the pro-inflammatory phenotype of MKD. Using CRISPR/Cas9 genome editing, we generated THP-1 cells with different MK deficiencies mimicking the severe (MKD-MA) and mild end (MKD-HIDS) of the MKD disease spectrum. Following confirmation of previously established disease-specific biochemical hallmarks, we studied the consequences of the different MK deficiencies on LPS-stimulated cytokine release, glycolysis versus oxidative phosphorylation rates, cellular chemotaxis and protein kinase activity. Similar to MKD patients' cells, MK deficiency in the THP-1 cells caused a pro-inflammatory phenotype with a severity correlating with the residual MK protein levels. In the MKD-MA THP-1 cells, MK protein levels were barely detectable, which affected protein prenylation and was accompanied by a profound pro-inflammatory phenotype. This included a markedly increased LPS-stimulated release of pro-inflammatory cytokines and a metabolic switch from oxidative phosphorylation towards glycolysis. We also observed increased activity of protein kinases that are involved in cell migration and proliferation, and in innate and adaptive immune responses. The MKD-HIDS THP-1 cells had approximately 20% residual MK activity and showed a milder phenotype, which manifested mainly upon LPS stimulation or exposure to elevated temperatures. MK-deficient THP-1 cells show the biochemical and pro-inflammatory phenotype of MKD and are a good model to study underlying disease mechanisms and therapeutic options of this autoinflammatory disorder.

Cardiovascular and muscular plasticity in an endurance-master athlete following 12 weeks of detraining and retraining: A case study.

Introduction
 This study aimed at examining the cardiorespiratory and muscular adaptations following 12 weeks of detraining and retraining in a 53-year-old endurance master athlete.
 Methods
 Data were collected before and after detraining and after retraining. Maximal oxygen uptake (VO2max) was evaluated during maximal cycling exercise. Proteins involved in muscle contraction, mitochondrial function and glycolysis were investigated using western blot analysis.
 Results
 VO2max decreased by 7% after detraining and was 5% greater than baseline after retraining. Detraining induced an important increase in the ryanodine receptor type 1 protein levels (RyR1, +44%) with a decrease in the protein levels of its stabilizer FKBP12 (-24%). We observed a 138% increase in the sarco-endoplasmic reticulum ATPase 1 protein and a 42% increase in the myosin heavy chain fast-twitch protein in response to detraining, suggesting transformation towards a more glycolytic phenotype. This was associated with depressed levels of the mitochondrial biogenesis and oxidative phosphorylation (OXPHOS) proteins, while the expression of the mitochondrial dynamic proteins appeared stimulated. Twelve weeks of retraining reversed almost all the alterations observed in muscle proteins, but specifically increased mitochondrial biogenesis, OXPHOS and antioxidant defense proteins as well as the glucose transporter 4 (Glut -4, +36%) and hexokinase (+100%) proteins levels compared to baseline. The mitochondrial dynamic proteins were further increased with the retraining.
 Discussion/Conclusion
 These data provide novel information on cardiorespiratory and muscular plasticity suggesting that highly endurance-trained athletes might show substantial muscular adaptations while retrained after a detraining period and call for more extensive clinical trials.

Cell lineage–guided mass spectrometry reveals increased energy metabolism and reactive oxygen species in the vertebrate organizer

Molecular understanding of the vertebrate Organizer, a tissue center critical for inductive signaling during gastrulation, has so far been mostly limited to transcripts and a few proteins, the latter due to limitations in detection and sensitivity. The Spemann-Mangold Organizer (SMO) in the South African Clawed Frog (X. laevis), a popular model of development, has long been known to be the origin of signals that pattern the mesoderm and central nervous system. Molecular screens of the SMO have identified several genes responsible for the ability of the SMO to establish the body axis. Nonetheless, a comprehensive study of proteins and metabolites produced specifically in the SMO and their functional roles has been lacking. Here, we pioneer a deep discovery proteomic and targeted metabolomic screen of the SMO in comparison to the remainder of the embryo using high-resolution mass spectrometry (HRMS). Quantification of ~4,600 proteins and a panel of targeted metabolites documented differential expression for 460 proteins and multiple intermediates of energy metabolism in the SMO. Upregulation of oxidative phosphorylation and redox regulatory proteins gave rise to elevated oxidative stress and an accumulation of reactive oxygen species in the SMO. Imaging experiments corroborated these findings, discovering enrichment of hydrogen peroxide in the SMO. Chemical perturbation of the redox gradient perturbed mesoderm involution during early gastrulation. HRMS expands the bioanalytical toolbox of cell and developmental biology, providing previously unavailable information on molecular classes to challenge and refine our classical understanding of the Organizer and its function during early patterning of the embryo.

NADPH oxidase overexpression and mitochondrial OxPhos impairment are more profound in human hearts donated after circulatory death than brain death.

This study investigated cardiac stress and mitochondrial oxidative phosphorylation (OxPhos) in human donation after circulatory death (DCD) hearts regarding warm ischemic time (WIT) and subsequent cold storage and compared them with that of human brain death donor (DBD) hearts. A total of 24 human hearts were procured for the research study-6 in the DBD group and 18 in the DCD group. DCD group was divided into three groups (n = 6) based on different WITs (20, 40, and 60 min). All hearts received del Nido cardioplegia before being placed in normal saline cold storage for 6 h. Left ventricular biopsies were performed at hours 0, 2, 4, and 6. Cardiac stress [nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits: 47-kDa protein of phagocyte oxidase (p47phox), 91-kDa glycoprotein of phagocyte oxidase (gp91phox)] and mitochondrial oxidative phosphorylation [OxPhos, complex I (NADH dehydrogenase) subunit of ETC (CI)-complex V (ATP synthase) subunit of ETC (CV)] proteins were measured in cardiac tissue and mitochondria respectively. Modulation of cardiac stress and mitochondrial dysfunction were observed in both DCD and DBD hearts. However, DCD hearts suffered more cardiac stress (overexpressed NADPH oxidase subunits) and diminished mitochondrial OxPhos than DBD hearts. The severity of cardiac stress and impaired oxidative phosphorylation in DCD hearts correlated with the longer WIT and subsequent cold storage time. More drastic changes were evident in DCD hearts with a WIT of 60 min or more. Activation of NADPH oxidase via overproduction of p47phox and gp91phox proteins in cardiac tissue may be responsible for cardiac stress leading to diminished mitochondrial oxidative phosphorylation. These protein changes can be used as biomarkers for myocardium damage and might help assess DCD and DBD heart transplant suitability.NEW & NOTEWORTHY First human DCD heart research studied cardiac stress and mitochondrial dysfunction concerning WIT and the efficacy of del Nido cardioplegia as an organ procurement solution and subsequent cold storage. Mild to moderate cardiac stress and mitochondrial dysfunction were noticed in DCD hearts with WIT 20 and 40 min and cold storage for 4 and 2 h, respectively. These changes can serve as biomarkers, allowing interventions to preserve mitochondria and extend WIT in DCD hearts.

METTL17 is an Fe-S cluster checkpoint for mitochondrial translation

Friedreich's ataxia (FA) is a debilitating, multisystemic disease caused by the depletion of frataxin (FXN), a mitochondrial iron-sulfur (Fe-S) cluster biogenesis factor. To understand the cellular pathogenesis of FA, we performed quantitative proteomics in FXN-deficient human cells. Nearly every annotated Fe-S cluster-containing protein was depleted, indicating that as a rule, cluster binding confers stability to Fe-S proteins. We also observed depletion of a small mitoribosomal assembly factor METTL17 and evidence of impaired mitochondrial translation. Using comparative sequence analysis, mutagenesis, biochemistry, and cryoelectron microscopy, we show that METTL17 binds to the mitoribosomal small subunit during late assembly and harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability. METTL17 overexpression rescued the mitochondrial translation and bioenergetic defects, but not the cellular growth, of FXN-depleted cells. These findings suggest that METTL17 acts as an Fe-S cluster checkpoint, promoting translation of Fe-S cluster-rich oxidative phosphorylation (OXPHOS) proteins only when Fe-S cofactors are replete.

Daily fluctuations in blood glucose with normal aging are inversely related to hippocampal synaptic mitochondrial proteins

Defective brain glucose utilization is a hallmark of Alzheimer’s disease (AD) while Type II diabetes and elevated blood glucose escalate the risk for AD in later life. Isolating contributions of normal aging from coincident metabolic or brain diseases could lead to refined approaches to manage specific health risks and optimize treatments targeted to susceptible older individuals. We evaluated metabolic, neuroendocrine, and neurobiological differences between young adult (6 months) and aged (24 months) male rats. Compared to young adults, blood glucose was significantly greater in aged rats at the start of the dark phase of the day but not during the light phase. When challenged with physical restraint, a potent stressor, aged rats effected no change in blood glucose whereas blood glucose increased in young adults. Tissues were evaluated for markers of oxidative phosphorylation (OXPHOS), neuronal glucose transport, and synapses. Outright differences in protein levels between age groups were not evident, but circadian blood glucose was inversely related to OXPHOS proteins in hippocampal synaptosomes, independent of age. The neuronal glucose transporter, GLUT3, was positively associated with circadian blood glucose in young adults whereas aged rats tended to show the opposite trend. Our data demonstrate aging increases daily fluctuations in blood glucose and, at the level of individual differences, negatively associates with proteins related to synaptic OXPHOS. Our findings imply that glucose dyshomeostasis may exacerbate metabolic aspects of synaptic dysfunction that contribute to risk for age-related brain disorders.

Additive impact of soy protein dietary intake and exercise on visceral fat mass reduction and mitochondrial complex I activation in skeletal muscle.

Soy protein has shown remarkable effectiveness in reducing fat mass compared with other protein sources, and exercise has the potential to further enhance this fat loss effect. Previous studies have demonstrated that soy protein intake leads to decreased fatty acid synthesis, which contributes to its fat-loss properties. However, the exact mechanism by which these lipids are consumed remains unclear. To investigate this, we conducted a comprehensive study using C57/BL6 male mice, comparing the effects of soy and casein proteins with and without exercise (Casein-Sed, Casein-Ex, Soy-Sed, and Soy-Ex groups) under high- and low-protein conditions (14% or 40% protein). Our findings revealed that combining soy protein intake with exercise significantly reduced epididymal white adipose tissue (eWAT) weight, particularly in the high-protein diet group. Further analysis revealed that exercise increased the expression of lipid oxidation-regulatory proteins, including mitochondrial oxidative phosphorylation protein (OXPHOS) complexes, in the plantaris muscle regardless of the protein source. Although soy protein intake did not directly affect muscle mitochondrial protein expression, the activity of OXPHOS complex I was additively enhanced by exercise and soy protein under the 40% protein condition. Notably, complex I activity inversely correlated with eWAT weight in the soy protein diet group. These results highlight the potential link between improved complex I activity induced by soy protein and fat mass reduction, which emphasizes the promising benefits of combining soy protein with exercise in promoting fat loss.NEW & NOTEWORTHY The findings revealed that soy protein intake combined with exercise resulted in reduced adipose tissue weight compared with that obtained with casein protein intake. Furthermore, the joint impact of exercise and soy protein consumption resulted in enhanced activity of oxidative phosphorylation protein (OXPHOS) complex I in fast-twitch muscles, which appears to be associated with fat mass reduction. These findings elucidate the potential additive effects of soy protein and exercise on body weight management.

The Oxidative Phosphorylation and Cytoskeleton Proteins of Mouse Ovaries after 96 Hours of Hindlimb Suspension.

The purpose of this study was to assess oxidative phosphorylation (OXPHOS) in mouse ovaries, determine the relative content of proteins that form the respiratory chain complexes and the main structures of the cytoskeleton, and determine the mRNA of the corresponding genes after hindlimb suspension for 96 h. After hindlimb suspension, the maximum rate of oxygen uptake increased by 133% (p < 0.05) compared to the control due to the complex I of the respiratory chain. The content of mRNA of genes encoding the main components of the respiratory chain increased (cyt c by 78%, cox IV by 56%, ATPase by 69%, p < 0.05 compared with the control). The relative content of cytoskeletal proteins that can participate in the processes of transport and localization of mitochondria does not change, with the exception of an increase in the content of alpha-tubulin by 25% (p < 0.05) and its acetylated isoform (by 36%, p < 0.05); however, the mRNA content of these cytoskeletal genes did not differ from the control. The content of GDF9 mRNA does not change after hindlimb suspension. The data obtained show that short-term exposure to simulated weightlessness leads to intensification of metabolism in the ovaries.

Synergistic lethality in chronic myeloid leukemia – targeting oxidative phosphorylation and unfolded protein response effectively complements tyrosine kinase inhibitor treatment

Chronic myeloid leukemia (CML) is effectively treated with tyrosine kinase inhibitors (TKIs), targeting the BCR::ABL1 oncoprotein. Still, resistance to therapy, relapse after treatment discontinuation, and side effects remain significant issues of long-term TKI treatment. Preliminary studies have shown that targeting oxidative phosphorylation (oxPhos) and the unfolded protein response (UPR) are promising therapeutic approaches to complement CML treatment. Here, we tested the efficacy of different TKIs, combined with the ATP synthase inhibitor oligomycin and the ER stress inducer thapsigargin in the CML cell lines K562, BV173, and KU812 and found a significant increase in cell death. Both, oligomycin and thapsigargin, triggered the upregulation of the UPR proteins ATF4 and CHOP, which was inhibited by imatinib. We observed comparable effects on cell death when combining TKIs with the ATP synthase inhibitor 8-chloroadenosine (8-Cl-Ado) as a potentially clinically applicable therapeutic agent. Stress-related apoptosis was triggered via a caspase cascade including the cleavage of caspase 3 and the inactivation of poly ADP ribose polymerase 1 (PARP1). The inhibition of PARP by olaparib also increased CML death in combination with TKIs. Our findings suggest a rationale for combining TKIs with 8-Cl-Ado or olaparib for future clinical studies in CML.