Search Results (70)

The BCS1L gene encodes a mitochondrial chaperone which inserts the Fe₂S₂ iron–sulfur Rieske protein into the nascent electron transfer complex III. Variants in the BCS1L gene are associated with a spectrum of mitochondrial disorders, ranging from mild to severe phenotypes. Björnstad syndrome, a milder condition, is characterized by sensorineural hearing loss (SNHL) and pili torti. More severe disorders include Complex III Deficiency, which leads to neuromuscular and metabolic dysfunctions with multi-systemic issues and Growth Retardation, Aminoaciduria, Cholestasis, Iron Overload, and Lactic Acidosis syndrome (GRACILE). The severity of these conditions varies depending on the specific BCS1L mutation and its impact on mitochondrial function. This study describes a 27-month-old child with SNHL, proximal renal tubular acidosis, woolly hypopigmented hair, developmental delay, and metabolic alterations. Genetic analysis revealed a homozygous BCS1L variant (c.38A>G, p.Asn13Ser), previously reported in a patient with a more severe phenotype that, however, was not functionally characterized. In this work, functional studies in a yeast model and patient-derived fibroblasts demonstrated that the variant impairs mitochondrial respiration, complex III activity (CIII), and also alters mitochondrial morphology in affected fibroblasts. Interestingly, we unveil a new possible mechanism of pathogenicity for BCS1L mutant protein. Since the interaction between BCS1L and CIII is increased, this suggests the formation of a BCS1L-containing nonfunctional preCIII unable to load RISP protein and complete CIII assembly. These findings support the pathogenicity of the BCS1L c.38A>G variant, suggesting altered interaction between the mutant BCS1L and CIII. Full article

For nearly three decades, interspecies somatic cell nuclear transfer (iSCNT) has been explored as a potential tool for cloning, regenerative medicine, and wildlife conservation. However, developmental inefficiencies remain a major challenge, largely due to persistent barriers in nucleocytoplasmic transport, mitonuclear communication, and epigenome crosstalk. This review synthesized peer-reviewed English articles from PubMed, Web of Science, and Scopus, spanning nearly three decades, using relevant keywords to explore the molecular mechanisms underlying iSCNT inefficiencies and potential improvement strategies. We highlight recent findings deepening the understanding of interspecies barriers in iSCNT, emphasizing their interconnected complexities, including the following: (1) nucleocytoplasmic incompatibility may disrupt nuclear pore complex (NPC) assembly and maturation, impairing the nuclear transport of essential transcription factors (TFs), embryonic genome activation (EGA), and nuclear reprogramming; (2) mitonuclear incompatibility could lead to nuclear and mitochondrial DNA (nDNA-mtDNA) mismatches, affecting electron transport chain (ETC) assembly, oxidative phosphorylation, and energy metabolism; (3) these interrelated incompatibilities can further influence epigenetic regulation, potentially leading to incomplete epigenetic reprogramming in iSCNT embryos. Addressing these challenges requires a multifaceted, species-specific approach that balances multiple incompatibilities rather than isolating a single factor. Gaining insight into the molecular interactions between the donor nucleus and recipient cytoplast, coupled with optimizing strategies tailored to specific pairings, could significantly enhance iSCNT efficiency, ultimately transforming experimental breakthroughs into real-world applications in reproductive biotechnology, regenerative medicine, and species conservation. Full article

HIV-associated neurocognitive disorders are prevalent despite antiretroviral intervention. Some HIV virotoxins, such as the trans-activator of transcription (Tat), are not targeted by antiretrovirals, and their neurotoxic actions may be exacerbated by opioids. Both Tat and morphine disrupt mitochondrial function, which may promote neurotoxicity, but the mechanisms are poorly understood. Herein, we assess the capacity of HIV Tat and morphine to alter the fundamental ability of mitochondria to generate and transfer energy along the electron transport chain (ETC). We find that exposure to Tat inhibits mitochondrial respiration driven by ETC complexes I or II in a concentration-dependent manner. Findings were consistent across models of permeabilized neuroblastoma cells, murine-derived mitoplasts, and mitochondria derived from mice exposed to Tat in vivo. In cell culture models, Tat promoted Ca²⁺ influx and the generation of cytosolic reactive oxygen species (ROS). Acute exposure to morphine exerted no effect on mitochondrial respiration, but morphine modestly offset Tat-mediated effects on complex I and some effects for the generation of ROS. Morphine did not exert any protective effects when acutely administered in vivo. The mitoprotective steroid, allopregnanolone (AlloP), increased mitochondrial respiration in neuroblastoma cells (complex I) or mitoplasts (complex II) and attenuated Tat-mediated impairment of complexes I and II in neuroblastoma cells or mice exposed to Tat in vivo. AlloP further attenuated Tat-mediated intracellular Ca²⁺ influx and cytosolic ROS production. Taken together, these results suggest that HIV Tat compromises mitochondrial function through the impairment of respiratory complexes I and II and that physiological AlloP may exert protective effects. Full article

The neurotoxicity of phosphorylated tau protein (P-tau) and mitochondrial dysfunction play a significant role in the pathophysiology of Alzheimer’s disease (AD). In vitro studies of the effects of P-tau oligomers on mitochondrial bioenergetics and reactive oxygen species production will allow us to evaluate the direct influence of P-tau on mitochondrial function. We measured the in vitro effect of P-tau oligomers on oxygen consumption and hydrogen peroxide production in isolated brain mitochondria. An appropriate combination of specific substrates and inhibitors of the phosphorylation pathway enabled the measurement and functional analysis of the effect of P-tau on mitochondrial respiration in defined coupling control states achieved in complex I-, II-, and I&II-linked electron transfer pathways. At submicromolar P-tau concentrations, we found no significant effect of P-tau on either mitochondrial respiration or hydrogen peroxide production in different respiratory states. The titration of P-tau showed a nonsignificant dose-dependent decrease in hydrogen peroxide production for complex I- and I&II-linked pathways. An insignificant in vitro effect of P-tau oligomers on both mitochondrial respiration and hydrogen peroxide production indicates that P-tau-induced mitochondrial dysfunction in AD is not due to direct effects of P-tau on the efficiency of the electron transport chain and on the production of reactive oxygen species. Full article

Mitochondria are the powerhouses of cells, also involved in ROS (reactive oxygen species) generation and cellular death regulation. Thus, several diseases are associated with mitochondrial impairment, including cardiovascular disorders (CVDs). Since CVDs are currently the leading cause of death worldwide, it is very important to evaluate targeting mitochondrial effectors in clinical treatment protocols. Hence, in the present study, antimycin A and rotenone, established inhibitors of the mitochondrial electron transfer chain, were shown to halt apoptotic death induced by curcumin (50 μM) and sorbitol (0.5 M), in H9c2 cardiac cells. In particular, immunoblotting analysis revealed that they totally abolished PARP [poly(ADP-ribose) polymerase] proteolysis, under these conditions. This finding was accompanied by an enhancement of cell viability, recovery of mitochondria networks’ integrity, suppression of cytochrome c release into the cytoplasm, and reversal of chromatin condensation. Chelating extracellular calcium (with EGTA) further enhanced the beneficial impact of antimycin A and rotenone on curcumin- or sorbitol-treated H9c2 cells viability. Of interest, the phosphorylation of eIF2α, indicative of the onset of the pro-survival Integrated Stress Response (IRS), was sustained under these conditions. Overall, our data highlight the anti-apoptotic effect of these compounds, unmasking their potential as mediators in novel therapeutic interventions against mitochondria-associated cardiac dysfunction. Full article

Cytochrome c is one of the most prominent representatives of peripheral membrane proteins. Besides functioning as an electron transfer carrier in the mitochondrial respiratory chain, it can acquire peroxidase capability, promote the self-assembly of α-synuclein, and function as a scavenger of superoxide. An understanding of its function requires knowledge of how the protein interacts with the inner membrane of mitochondria. The first part of this article provides an overview of a variety of experiments that were aimed at exploring the details of cytochrome c binding to anionic lipid liposomes, which serve as a model system for the inner membrane. While cytochrome c binding involves a conformational change from a folded into a partially disordered state, α-synuclein is intrinsically disordered in solution and subjected to a partial coil -> helix transition on membranes. Depending on the solution conditions and the surface density of α-synuclein, the protein facilitates the self-assembly into oligomers and fibrils. As for cytochrome c, results of binding experiments are discussed. In addition, the article analyzes experiments that explored α-synuclein aggregation. Similarities and differences between cytochrome c and α-synuclein binding are highlighted. Finally, the article presents a brief account of the interplay between cytochrome c and α-synuclein and its biological relevance. Full article

In recent decades, several discoveries have been made that force us to reconsider old ideas about mitochondria and energy metabolism in the light of these discoveries. In this review, we discuss metabolic interaction between various organs, the metabolic significance of the primary substrates and their metabolic pathways, namely aerobic glycolysis, lactate shuttling, and fatty acids β-oxidation. We rely on the new ideas about the supramolecular structure of the mitochondrial respiratory chain (respirasome), the necessity of supporting substrates for fatty acids β-oxidation, and the reverse electron transfer via succinate dehydrogenase during β-oxidation. We conclude that ATP production during fatty acid β-oxidation has its upper limits and thus cannot support high energy demands alone. Meanwhile, β-oxidation creates conditions that significantly accelerate the cycle: glucose-aerobic glycolysis-lactate-gluconeogenesis-glucose. Therefore, glycolytic ATP production becomes an important energy source in high energy demand. In addition, lactate serves as a mitochondrial substrate after converting to pyruvate + H⁺ by the mitochondrial lactate dehydrogenase. All coupled metabolic pathways are irreversible, and the enzymes are organized into multienzyme structures. Full article

Gallium-based therapy has been considered a potentially effective cancer therapy for decades and has recently re-emerged as a novel therapeutic strategy for the management of glioblastoma tumors. Gallium targets the iron-dependent phenotype associated with aggressive tumors by mimicking iron in circulation and gaining intracellular access through transferrin-receptor-mediated endocytosis. Mechanistically, it is believed that gallium inhibits critical iron-dependent enzymes like ribonucleotide reductase and NADH dehydrogenase (electron transport chain complex I) by replacing iron and removing the ability to transfer electrons through the protein secondary structure. However, information regarding the effects of gallium on cellular iron metabolism is limited. As mitochondrial iron metabolism serves as a central hub of the iron metabolic network, the goal of this study was to investigate the effects of gallium on mitochondrial iron metabolism in glioblastoma cells. Here, it has been discovered that gallium nitrate can induce mitochondrial iron depletion, which is associated with the induction of DNA damage. Moreover, the generation of gallium-resistant cell lines reveals a highly unstable phenotype characterized by impaired colony formation associated with a significant decrease in mitochondrial iron content and loss of the mitochondrial iron uptake transporter, mitoferrin-1. Moreover, gallium-resistant cell lines are significantly more sensitive to radiation and have an impaired ability to repair any sublethal damage and to survive potentially lethal radiation damage when left for 24 h following radiation. These results support the hypothesis that gallium can disrupt mitochondrial iron metabolism and serve as a potential radiosensitizer. Full article

Succinate dehydrogenase (also known as complex II) plays a dual role in respiration by catalyzing the oxidation of succinate to fumarate in the tricarboxylic acid (TCA) cycle and transferring electrons from succinate to ubiquinone in the mitochondrial electron transport chain (ETC). Owing to the privileged position of SDH/CII, its dysfunction leads to TCA cycle arrest and altered respiration. This review aims to elucidate the widely documented profound metabolic effects of SDH/CII deficiency, along with the newly unveiled survival mechanisms in SDH/CII-deficient cells. Such an understanding reveals exploitable vulnerabilities for strategic targeting, which is crucial for the development of novel and more precise therapies for primary mitochondrial diseases, as well as for familial and sporadic cancers associated with SDH/CII mutations. Full article

The Plasmodium falciparum mitochondrial electron transport chain (mETC) is responsible for essential metabolic pathways such as de novo pyrimidine synthesis and ATP synthesis. The mETC complex III (cytochrome bc₁ complex) is responsible for transferring electrons from ubiquinol to cytochrome c and generating a proton gradient across the inner mitochondrial membrane, which is necessary for the function of ATP synthase. Recent studies have revealed that the composition of Plasmodium falciparum complex III (PfCIII) is divergent from humans, highlighting its suitability as a target for specific inhibition. Indeed, PfCIII is the target of the clinically used anti-malarial atovaquone and of several inhibitors undergoing pre-clinical trials, yet its role in parasite biology has not been thoroughly studied. We provide evidence that the universally conserved subunit, PfRieske, and the new parasite subunit, PfC3AP2, are part of PfCIII, with the latter providing support for the prediction of its divergent composition. Using inducible depletion, we show that PfRieske, and therefore, PfCIII as a whole, is essential for asexual blood stage parasite survival, in line with previous observations. We further found that depletion of PfRieske results in gametocyte maturation defects. These phenotypes are linked to defects in mitochondrial functions upon PfRieske depletion, including increased sensitivity to mETC inhibitors in asexual stages and decreased cristae abundance alongside abnormal mitochondrial morphology in gametocytes. This is the first study that explores the direct role of the PfCIII in gametogenesis via genetic disruption, paving the way for a better understanding of the role of mETC in the complex life cycle of these important parasites and providing further support for the focus of antimalarial drug development on this pathway. Full article

The conversion of nitrate to ammonium, i.e., nitrate reduction, is a major consumer of reductants in plants. Previous studies have reported that the mitochondrial alternative oxidase (AOX) is upregulated under limited nitrate reduction conditions, including no/low nitrate or when ammonium is the sole nitrogen (N) source. Electron transfer from ubiquinone to AOX bypasses the proton-pumping complexes III and IV, thereby consuming reductants efficiently. Thus, upregulated AOX under limited nitrate reduction may dissipate excessive reductants and thereby attenuate oxidative stress. Nevertheless, so far there is no firm evidence for this hypothesis due to the lack of experimental systems to analyze the direct relationship between nitrate reduction and AOX. We therefore developed a novel culturing system for A. thaliana that manipulates shoot activities of nitrate reduction and AOX separately without causing N starvation, ammonium toxicity, or lack of nitrate signal. Using shoots processed with this system, we examined genome-wide gene expression and growth to better understand the relationship between AOX and nitrate reduction. The results showed that, only when nitrate reduction was limited, AOX deficiency significantly upregulated genes involved in mitochondrial oxidative stress, reductant shuttles, and non-phosphorylating bypasses of the respiratory chain, and inhibited growth. Thus, we conclude that AOX alleviates mitochondrial oxidative stress and sustains plant growth under limited nitrate reduction. Full article

Cytochrome c (CytC), a one-electron carrier, transfers electrons from complex bc₁ to cytochrome c oxidase (CcO) in the electron-transport chain. Electrostatic interaction with the partners, complex bc₁ and CcO, is ensured by a lysine cluster near the heme forming the Universal Binding Site (UBS). We constructed three mutant variants of mitochondrial CytC with one (2Mut), four (5Mut), and five (8Mut) Lys->Glu substitutions in the UBS and some compensating Glu->Lys substitutions at the periphery of the UBS for charge compensation. All mutants showed a 4–6 times increased peroxidase activity and accelerated binding of cyanide to the ferric heme of CytC. In contrast, decomposition of the cyanide complex with ferrous CytC, as monitored by magnetic circular dichroism spectroscopy, was slower in mutants compared to WT. Molecular dynamic simulations revealed the increase in the fluctuations of C_α atoms of individual residues of mutant CytC compared to WT, especially in the Ω-loop (70–85), which can cause destabilization of the Fe…S(Met80) coordination link, facilitation of the binding of exogenous ligands cyanide and peroxide, and an increase in peroxidase activity. It was found that only one substitution K72E is enough to induce all these changes, indicating the significance of K72 and the Ω-loop (70–85) for the structure and physiology of mitochondrial CytC. In this work, we also propose using a ferro-ferricyanide buffer as a substrate to monitor the peroxidase activity of CytC. This new approach allows us to determine the rate of peroxidase activity at moderate (200 µM) concentrations of H₂O₂ and avoid complications of radical formation during the reaction. Full article

Glycogen storage disease type III (GSDIII) is a hereditary glycogenosis caused by deficiency of the glycogen debranching enzyme (GDE), an enzyme, encoded by Agl, enabling glycogen degradation by catalyzing alpha-1,4-oligosaccharide side chain transfer and alpha-1,6-glucose cleavage. GDE deficiency causes accumulation of phosphorylase-limited dextrin, leading to liver disorder followed by fatal myopathy. Here, we tested the capacity of the new autophagosomal activator GHF-201 to alleviate disease burden by clearing pathogenic glycogen surcharge in the GSDIII mouse model Agl^−/−. We used open field, grip strength, and rotarod tests for evaluating GHF-201’s effects on locomotion, a biochemistry panel to quantify hematological biomarkers, indirect calorimetry to quantify in vivo metabolism, transmission electron microscopy to quantify glycogen in muscle, and fibroblast image analysis to determine cellular features affected by GHF-201. GHF-201 was able to improve all locomotion parameters and partially reversed hypoglycemia, hyperlipidemia and liver and muscle malfunction in Agl^−/− mice. Treated mice burnt carbohydrates more efficiently and showed significant improvement of aberrant ultrastructural muscle features. In GSDIII patient fibroblasts, GHF-201 restored mitochondrial membrane polarization and corrected lysosomal swelling. In conclusion, GHF-201 is a viable candidate for treating GSDIII as it recovered a wide range of its pathologies in vivo, in vitro, and ex vivo. Full article

Maternal obesity has been associated with short- and long-term risks of pregnancy-perinatal adverse events, possibly due to alterations of placental mitochondrial bioenergetics. However, several detrimental mechanisms occurring in the placentas of women with obesity still need to be clarified. Here, we analyzed placental mitochondrial features and oxidative environment of 46 pregnancies in relation to pre-pregnancy BMI. Seventeen Caucasian normal-weight (NW) and twenty-nine women who were obese (OB) were enrolled. The protein expression of mitochondrial CypD and electron transfer chain complexes (C) I–V were measured, as well as ATP production and oxygen consumption rates (OCRs). The protein levels of the pro/anti-oxidant enzymes TXNIP, SOD2, and PON2 were also analyzed. Despite no differences in CypD expression, OCRs were significantly lower in OB vs. NW women. Accordingly, ATP synthase (CV) levels and ATP content were decreased in OB women, positively correlating with placental efficiency, suggesting a link between ATP deficiency and placental dysfunction. SOD2 expression negatively correlated with maternal BMI, indicating a possible impairment of antioxidant defenses with increasing BMI. These changes were worsened in 10 OB women presenting with gestational diabetes mellitus. Overall, these results suggest alterations of placental bioenergetics in pregnancies of women with obesity, possibly leading to placental dysfunction and altered fetal development and programming. Full article

Circadian oscillations of several physiological and behavioral processes are an established process in all the organisms anticipating the geophysical changes recurring during the day. The time-keeping mechanism is controlled by a transcription translation feedback loop involving a set of well-characterized transcription factors. The synchronization of cells, controlled at the organismal level by a brain central clock, can be mimicked in vitro, pointing to the notion that all the cells are endowed with an autonomous time-keeping system. Metabolism undergoes circadian control, including the mitochondrial terminal catabolic pathways, culminating under aerobic conditions in the electron transfer to oxygen through the respiratory chain coupled to the ATP synthesis according to the oxidative phosphorylation chemiosmotic mechanism. In this study, we expanded upon previous isolated observations by utilizing multiple cell types, employing various synchronization protocols and different methodologies to measure mitochondrial oxygen consumption rates under conditions simulating various metabolic stressors. The results obtained clearly demonstrate that mitochondrial respiratory activity undergoes rhythmic oscillations in all tested cell types, regardless of their individual respiratory proficiency, indicating a phenomenon that can be generalized. However, notably, while primary cell types exhibited similar rhythmic respiratory profiles, cancer-derived cell lines displayed highly heterogeneous rhythmic changes. This observation confirms on the one hand the dysregulation of the circadian control of the oxidative metabolism observed in cancer, likely contributing to its development, and on the other hand underscores the necessity of personalized chronotherapy, which necessitates a detailed characterization of the cancer chronotype. Full article