Search Results (24)

Mitochondria are a key organelle in maintaining metabolic homeostasis. It not only generates most of the cell’s energy through oxidative phosphorylation but also acts as a complex sensor of the redox state and oxygen in the cell. This review thoroughly analyzes the interactions among mitochondrial iron metabolism, mitochondrial reactive oxygen species (mtROS), and lipid peroxidation (LPO), the triggering factors of ferroptosis, an iron-dependent form of programmed cell death. We point out research showing that intrinsic mitochondrial machinery, such as iron–sulfur (Fe-S) cluster assembly and heme metabolism, is both an important cofactor and a master regulator. If these processes are disrupted, they can lead to ferroptosis. Unlike views that focus on the cytosol, we explain that the stability of Fe-S clusters in complexes such as aconitase and respiratory Complex I is crucial for preventing electron leakage and excessive mtROS formation. The Fenton reaction and its direct effect on cardiolipin (CL) oxidation in the inner membrane of mitochondria is a central event in cardiometabolic diseases. Its peroxidation and breakdown make the organelle very unstable and lead to cell death though Ca²⁺ overload and a significantly decreased reduced/oxidized glutathione ratio. Additionally, the functions of essential iron transporters and glutathione homeostasis are examined, and their dysregulation is correlated with ferroptosis-associated progression of cardiometabolic and neurodegenerative disorders, such as obesity and Alzheimer’s disease. This review focused on the need to revisit the classic bioenergetic core of the mitochondria as a key player in the pathophysiology of metabolic and neurodegenerative diseases. Full article

Frataxin is a component of the iron–sulfur (Fe-S) cluster assembly complex in mitochondria, and deficiency is associated with Friedreich ataxia (FA). The yeast homolog Yfh1 resembles and cross-complements with its human equivalent, and frataxin bypass scenarios are of particular interest because they may point to strategies for treating FA. Here, we describe frataxin/Yfh1 bypass by overexpression of Rsm22, an assembly factor for the mitochondrial ribosome. Rsm22 overexpression in Yfh1-depleted yeast cells restored critical processes in mitochondria, including Fe-S cluster assembly, lipoic acid synthesis, iron homeostasis, and heme synthesis, to a significant extent. Formation of cytoplasmic Fe-S proteins was also restored, suggesting recovery of the mitochondrial ability to generate the (Fe-S)_int intermediate that is exported from mitochondria and is utilized for cytoplasmic Fe-S cluster assembly. Importantly, an essential component of the mitochondrial iron–sulfur cluster machinery, namely ferredoxin, was virtually absent in mitochondria lacking Yfh1, but it was recovered with Rsm22 overexpression. Interestingly, ferredoxin overexpression could offset some of the effects of Yfh1 depletion. Ferredoxin has recently been shown to bind to the cysteine desulfurase protein Nfs1 at the same site as Yfh1, in a conserved arginine patch on Nfs1, such that ferredoxin binding at this site may confer frataxin-bypass activity. Full article

Iron deficiency is highly prevalent in patients with idiopathic pulmonary hypertension; nevertheless, its role and clinical significance in hypoxic pulmonary hypertension (HPH) remain elusive. Therefore, this study aims to clarify the role and molecular mechanisms of iron in HPH. By means of a retrospective analysis of clinical data from HPH patients and examinations of HPH animal models, we discovered that both HPH patients and animal models exhibit significant iron deficiency, characterized by reduced hepatic iron storage and elevated hepcidin expression. To further explore iron’s role in HPH, we modulated iron metabolism through pharmacological and dietary interventions in chronic hypoxic animal models. The results showed that iron deficiency exacerbated chronic hypoxia-induced pulmonary hypertension and right ventricular hypertrophy, while iron supplementation alleviated these conditions. Further investigations revealed that iron regulates HIF2α expression in pulmonary arterial endothelial cells (PAECs) under chronic hypoxia. Therefore, through in vivo and in vitro experiments, we demonstrated that HIF2α inhibition attenuates chronic hypoxia-induced pulmonary hypertension and right ventricular hypertrophy. Mechanistically, chronic hypoxia-mediated iron deficiency enhances HIF2α activation, subsequently suppressing iron/sulfur cluster assembly enzyme (ISCU) expression. This leads to decreased mitochondrial complexes I and III activity, increased reactive oxygen species (ROS) production, and inhibited oxidative phosphorylation. Consequently, metabolic reprogramming in PAECs results in a proliferation/apoptosis imbalance, ultimately exacerbating hypoxia-induced pulmonary hypertension and right ventricular hypertrophy. Collectively, our findings demonstrate that iron supplementation mitigates HPH progression by modulating HIF2α-mediated metabolic reprogramming in PAECs, revealing multiple therapeutic targets for HPH. Full article

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

Accurate DNA replication is essential for the maintenance of genome stability and the generation of healthy offspring. When DNA replication is challenged, signals accumulate at blocked replication forks that elicit a multifaceted cellular response, orchestrating DNA replication, DNA repair and cell cycle progression. This replication stress response promotes the recovery of DNA replication, maintaining chromosome integrity and preventing mutations. Defects in this response are linked to heightened genetic instability, which contributes to tumorigenesis and genetic disorders. Iron–sulfur (Fe-S) clusters are emerging as important cofactors in supporting the response to replication stress. These clusters are assembled and delivered to target proteins that function in the cytosol and nucleus via the conserved cytosolic Fe-S cluster assembly (CIA) machinery and the CIA targeting complex. This review summarizes recent advances in understanding the structure and function of the CIA machinery in yeast and mammals, emphasizing the critical role of Fe-S clusters in the replication stress response. Full article

Fe-S clusters are essential cofactors for the activity of a large variety of metalloproteins that play important roles in respiration, photosynthesis, nitrogen fixation, regulation of gene expression, and numerous metabolic pathways, including biosynthesis of other protein cofactors. Assembly of iron and sulfur atoms into a cluster, followed by its insertion into the polypeptide chain, is a complex process ensured by multiproteic systems. Through evolution, eukaryotes have acquired two Fe-S protein biogenesis systems by endosymbiosis from bacteria. These systems, ISC and SUF, are compartmentalized in mitochondria and plastids, respectively. The eukaryotic Fe-S protein biogenesis system (CIA) is dedicated to the biogenesis of cytosolic and nuclear Fe-S proteins. While the CIA system is absent in bacteria, at least two of its components share homologies with bacterial Fe-S protein biogenesis factors, Mrp and SufT. Here, we provide an overview of the role of Mrp and SufT in Fe-S protein biogenesis in bacteria, aiming to put forward specific but also common features with their eukaryotic CIA counterparts. Full article

The Yessentuki mineral water deposit (YMWD) is a well-known source of balneologically valuable drinking mineral water, but it has rarely been investigated in terms of the microbes inhabiting it. In this work, we have studied the microbial communities of the continuously operating production well 9, penetrating the Lower Cretaceous aquifer of the YMWD, and characterized, in detail, two novel representatives of class Ignavibacteria (Bacteroidota). One representative of the so-called XYB12-FULL-38-5 group within the family Melioribacteraceae has been isolated in pure culture, designated strain 09-Me, and physiologically characterized. It is a facultatively anaerobic thermotolerant microorganism capable of fermentation and respiration on simple and complex sugars (lichenan, xanthan gum, glucomannan, curdlan, pachyman). In addition to oxygen, ferric iron, arsenate, and elemental sulfur were also used as electron acceptors. Phylogenomic and physiological analyses reveal this novel isolate to represent a novel genus and species for which the name Stygiobacter electus gen. nov., sp. nov. is proposed. The second representative of the family Melioribacteraceae described here belonged to the so-called DSXH01 group, which comprises the dominant group (up to 28%) of the microbial community of well 9 water. The organism was characterized through the analysis of its genome, assembled from metagenome of well 9 (Ess09-04 MAG). Genes encoding enzymes of carbohydrate utilization and genes responsible for aerobic and anaerobic respiration have been identified in the genomes of both bacteria. The investigation of the environmental distribution of Stygiobacter genus-related bacteria and representatives of the lineage DSXH01 has shown that they all are typical inhabitants of the subsurface biosphere, and are often found in bioreactors. These data significantly expand our knowledge on the microbes of subsurface water basins and pave the way for future studies of the novel members of Ignavibacteria class. Full article

The geomagnetic field (GMF) is a natural component of the biosphere, and, during evolution, all organisms experienced its presence while some evolved the ability to perceive magnetic fields (MF). We studied the response of 14-3-3 proteins and the plasma membrane (PM) proton pump H⁺-ATPase to reduced GMF values by lowering the GMF intensity to a near-null magnetic field (NNMF). Seedling morphology, H⁺-ATPase activity and content, 14-3-3 protein content, binding to PM and phosphorylation, gene expression, and ROS quantification were assessed in maize (Zea mays) dark-grown seedlings. Phytohormone and melatonin quantification were also assessed by LG-MS/MS. Our results suggest that the GMF regulates the PM H⁺-ATPase, and that NNMF conditions alter the proton pump activity by reducing the binding of 14-3-3 proteins. This effect was associated with both a reduction in H₂O₂ and downregulation of genes coding for enzymes involved in ROS production and scavenging, as well as calcium homeostasis. These early events were followed by the downregulation of IAA synthesis and gene expression and the increase in both cytokinin and ABA, which were associated with a reduction in root growth. The expression of the homolog of the MagR gene, ZmISCA2, paralleled that of CRY1, suggesting a possible role of ISCA in maize magnetic induction. Interestingly, melatonin, a widespread molecule present in many kingdoms, was increased by the GMF reduction, suggesting a still unknown role of this molecule in magnetoreception. Full article

Multiple mitochondrial dysfunctions syndrome type 2 with hyperglycinemia (MMDS2) is a severe disorder of mitochondrial energy metabolism, associated with biallelic mutations in the gene encoding for BOLA3, a protein with a not yet completely understood role in iron-sulfur (Fe-S) cluster biogenesis, but essential for the maturation of mitochondrial [4Fe-4S] proteins. To better understand the role of BOLA3 in MMDS2, we have investigated the impact of the p.His96Arg (c.287A > G) point mutation, which involves a highly conserved residue, previously identified as a [2Fe-2S] cluster ligand in the BOLA3-[2Fe-2S]-GLRX5 heterocomplex, on the structural and functional properties of BOLA3 protein. The His96Arg mutation has been associated with a severe MMDS2 phenotype, characterized by defects in the activity of mitochondrial respiratory complexes and lipoic acid-dependent enzymes. Size exclusion chromatography, NMR, UV-visible, circular dichroism, and EPR spectroscopy characterization have shown that the His96Arg mutation does not impair the interaction of BOLA3 with its protein partner GLRX5, but leads to the formation of an aberrant BOLA3-[2Fe-2S]-GLRX5 heterocomplex, that is not functional anymore in the assembly of a [4Fe-4S] cluster on NFU1. These results allowed us to rationalize the severe phenotype observed in MMDS2 caused by His96Arg mutation. Full article

Enzymes carrying Iron-Sulfur (Fe-S) clusters perform many important cellular functions and their biogenesis require complex protein machinery. In mitochondria, the IBA57 protein is essential and promotes assembly of [4Fe-4S] clusters and their insertion into acceptor proteins. YgfZ is the bacterial homologue of IBA57 but its precise role in Fe-S cluster metabolism is uncharacterized. YgfZ is needed for activity of the radical S-adenosyl methionine [4Fe-4S] cluster enzyme MiaB which thiomethylates some tRNAs. The growth of cells lacking YgfZ is compromised especially at low temperature. The RimO enzyme is homologous to MiaB and thiomethylates a conserved aspartic acid in ribosomal protein S12. To quantitate thiomethylation by RimO, we developed a bottom-up LC-MS² analysis of total cell extracts. We show here that the in vivo activity of RimO is very low in the absence of YgfZ and independent of growth temperature. We discuss these results in relation to the hypotheses relating to the role of the auxiliary 4Fe-4S cluster in the Radical SAM enzymes that make Carbon-Sulfur bonds. Full article

Plants evolved in the presence of the Earth’s magnetic field (or geomagnetic field, GMF). Variations in MF intensity and inclination are perceived by plants as an abiotic stress condition with responses at the genomic and metabolic level, with changes in growth and developmental processes. The reduction of GMF to near null magnetic field (NNMF) values by the use of a triaxial Helmholtz coils system was used to evaluate the requirement of the GMF for Lima bean (Phaseolus lunatus L.) photosynthesis and reactive oxygen species (ROS) production. The leaf area, stomatal density, chloroplast ultrastructure and some biochemical parameters including leaf carbohydrate, total carbon, protein content and δ¹³C were affected by NNMF conditions, as were the chlorophyll and carotenoid levels. RubisCO activity and content were also reduced in NNMF. The GMF was required for the reaction center’s efficiency and for the reduction of quinones. NNMF conditions downregulated the expression of the MagR homologs PlIScA2 and PlcpIScA, implying a connection between magnetoreception and photosynthetic efficiency. Finally, we showed that the GMF induced a higher expression of genes involved in ROS production, with increased contents of both H₂O₂ and other peroxides. Our results show that, in Lima bean, the GMF is required for photosynthesis and that PlIScA2 and PlcpIScA may play a role in the modulation of MF-dependent responses of photosynthesis and plant oxidative stress. Full article

Tuberculosis (TB) remains the leading cause of death due to a single pathogen, accounting for 1.5 million deaths annually on the global level. Mycobacterium tuberculosis, the causative agent of TB, is persistently exposed to stresses such as reactive oxygen species (ROS), reactive nitrogen species (RNS), acidic conditions, starvation, and hypoxic conditions, all contributing toward inhibiting bacterial proliferation and survival. Iron–sulfur (Fe-S) clusters, which are among the most ancient protein prosthetic groups, are good targets for ROS and RNS, and are susceptible to Fe starvation. Mtb holds Fe-S containing proteins involved in essential biological process for Mtb. Fe-S cluster assembly is achieved via complex protein machineries. Many organisms contain several Fe-S assembly systems, while the SUF system is the only one in some pathogens such as Mtb. The essentiality of the SUF machinery and its functionality under the stress conditions encountered by Mtb underlines how it constitutes an attractive target for the development of novel anti-TB. Full article

The importance of mitochondria in mammalian cells is widely known. Several biochemical reactions and pathways take place within mitochondria: among them, there are those involving the biogenesis of the iron–sulfur (Fe-S) clusters. The latter are evolutionarily conserved, ubiquitous inorganic cofactors, performing a variety of functions, such as electron transport, enzymatic catalysis, DNA maintenance, and gene expression regulation. The synthesis and distribution of Fe-S clusters are strictly controlled cellular processes that involve several mitochondrial proteins that specifically interact each other to form a complex machinery (Iron Sulfur Cluster assembly machinery, ISC machinery hereafter). This machinery ensures the correct assembly of both [2Fe-2S] and [4Fe-4S] clusters and their insertion in the mitochondrial target proteins. The present review provides a structural and molecular overview of the rare diseases associated with the genes encoding for the accessory proteins of the ISC machinery (i.e., GLRX5, ISCA1, ISCA2, IBA57, FDX2, BOLA3, IND1 and NFU1) involved in the assembly and insertion of [4Fe-4S] clusters in mitochondrial proteins. The disease-related missense mutations were mapped on the 3D structures of these accessory proteins or of their protein complexes, and the possible impact that these mutations have on their specific activity/function in the frame of the mitochondrial [4Fe-4S] protein biogenesis is described. Full article

Free fatty acids (FFA), hyperglycemia, and inflammatory cytokines are major mediators of β-cell toxicity in type 2 diabetes mellitus, impairing mitochondrial metabolism. Glutaredoxin 5 (Glrx5) is a mitochondrial protein involved in the assembly of iron–sulfur clusters required for complexes of the respiratory chain. We have provided evidence that islet cells are deprived of Glrx5, correlating with impaired insulin secretion during diabetes in genetically obese mice. In this study, we induced diabesity in C57BL/6J mice in vivo by feeding the mice a high-fat diet (HFD) and modelled the diabetic metabolism in MIN6 cells through exposure to FFA, glucose, or inflammatory cytokines in vitro. qRT-PCR, ELISA, immunohisto-/cytochemistry, bioluminescence, and respirometry were employed to study Glrx5, insulin secretion, and mitochondrial biomarkers. The HFD induced a depletion of islet Glrx5 concomitant with an obese phenotype, elevated FFA in serum and reactive oxygen species in islets, and impaired glucose tolerance. Exposure of MIN6 cells to FFA led to a loss of Glrx5 in vitro. The FFA-induced depletion of Glrx5 coincided with significantly altered mitochondrial biomarkers. In summary, we provide evidence that Glrx5 is regulated by FFA in type 2 diabetes mellitus and is linked to mitochondrial dysfunction and blunted insulin secretion. Full article

Iron–sulfur clusters (Fe–S or ISC) are essential cofactors that function in a wide range of biological pathways. In mammalian cells, Fe–S biosynthesis primarily relies on mitochondria and involves a concerted group of evolutionary-conserved proteins forming the ISC pathway. In the early stage of the ISC pathway, the Fe–S core complex is required for de novo assembly of Fe–S. In humans, the Fe–S core complex comprises the cysteine desulfurase NFS1, the scaffold protein ISCU2, frataxin (FXN), the ferredoxin FDX2, and regulatory/accessory proteins ISD11 and Acyl Carrier Protein (ACP). In recent years, the field has made significant advances in unraveling the structure of the Fe–S core complex and the mechanism underlying its function. Herein, we review the key recent findings related to the Fe–S core complex and its components. We highlight some of the unanswered questions and provide a model of the Fe–S assembly within the complex. In addition, we briefly touch on the genetic diseases associated with mutations in the Fe–S core complex components. Full article