Fe-S Cluster Synthesis Research Articles

Impaired Iron-Sulfur Cluster Synthesis Induces Mitochondrial PARthanatos in Diabetic Cardiomyopathy.

Diabetic cardiomyopathy (DCM), a severe complication of diabetes, is characterized by mitochondrial dysfunction, oxidative stress, and DNA damage. Despite its severity, the intrinsic factors governing cardiomyocyte damage in DCM remain unclear. It is hypothesized that impaired iron-sulfur (Fe-S) cluster synthesis plays a crucial role in the pathogenesis of DCM. Reduced S-sulfhydration of cysteine desulfurase (NFS1) is a novel mechanism that contributes to mitochondrial dysfunction and PARthanatos in DCM. Mechanistically, hydrogen sulfide (H2S) supplementation restores NFS1 S-sulfhydration at cysteine 383 residue, thereby enhancing Fe-S cluster synthesis, improving mitochondrial function, increasing cardiomyocyte viability, and alleviating cardiac damage. This study provides novel insights into the interplay between Fe-S clusters, mitochondrial dysfunction, and PARthanatos, highlighting a promising therapeutic target for DCM and paving the way for potential clinical interventions to improve patient outcomes.

MTORC1 Signaling Inhibition Modulates Mitochondrial Function in Frataxin Deficiency.

Lysosomes regulate mitochondrial function through multiple mechanisms including the master regulator, mechanistic Target of Rapamycin Complex 1 (mTORC1) protein kinase, which is activated at the lysosomal membrane by nutrient, growth factor and energy signals. mTORC1 promotes mitochondrial protein composition changes, respiratory capacity, and dynamics, though the full range of mitochondrial-regulating functions of this protein kinase remain undetermined. We find that acute chemical modulation of mTORC1 signaling decreased mitochondrial oxygen consumption, increased mitochondrial membrane potential and reduced susceptibility to stress-induced mitophagy. In cellular models of Friedreich's Ataxia (FA), where loss of the Frataxin (FXN) protein suppresses Fe-S cluster synthesis and mitochondrial respiration, the changes induced by mTORC1 inhibitors lead to improved cell survival. Proteomic-based profiling uncover compositional changes that could underlie mTORC1-dependent modulation of FXN-deficient mitochondria. These studies highlight mTORC1 signaling as a regulator of mitochondrial composition and function, prompting further evaluation of this pathway in the context of mitochondrial disease.

Mitochondrial respiratory function is preserved under cysteine starvation via glutathione catabolism in NSCLC

Cysteine metabolism occurs across cellular compartments to support diverse biological functions and prevent the induction of ferroptosis. Though the disruption of cytosolic cysteine metabolism is implicated in this form of cell death, it is unknown whether the substantial cysteine metabolism resident within the mitochondria is similarly pertinent to ferroptosis. Here, we show that despite the rapid depletion of intracellular cysteine upon loss of extracellular cystine, cysteine-dependent synthesis of Fe-S clusters persists in the mitochondria of lung cancer cells. This promotes a retention of respiratory function and a maintenance of the mitochondrial redox state. Under these limiting conditions, we find that glutathione catabolism by CHAC1 supports the mitochondrial cysteine pool to sustain the function of the Fe-S proteins critical to oxidative metabolism. We find that disrupting Fe-S cluster synthesis under cysteine restriction protects against the induction of ferroptosis, suggesting that the preservation of mitochondrial function is antagonistic to survival under starved conditions. Overall, our findings implicate mitochondrial cysteine metabolism in the induction of ferroptosis and reveal a mechanism of mitochondrial resilience in response to nutrient stress.

Apicoplast-Resident Processes: Exploiting the Chink in the Armour of Plasmodium falciparum Parasites.

The discovery of a relict plastid, also known as an apicoplast (apicomplexan plastid), that houses housekeeping processes and metabolic pathways critical to Plasmodium parasites' survival has prompted increased research on identifying potent inhibitors that can impinge on apicoplast-localised processes. The apicoplast is absent in humans, yet it is proposed to originate from the eukaryote's secondary endosymbiosis of a primary symbiont. This symbiotic relationship provides a favourable microenvironment for metabolic processes such as haem biosynthesis, Fe-S cluster synthesis, isoprenoid biosynthesis, fatty acid synthesis, and housekeeping processes such as DNA replication, transcription, and translation, distinct from analogous mammalian processes. Recent advancements in comprehending the biology of the apicoplast reveal it as a vulnerable organelle for malaria parasites, offering numerous potential targets for effective antimalarial therapies. We provide an overview of the metabolic processes occurring in the apicoplast and discuss the organelle as a viable antimalarial target in light of current advances in drug discovery. We further highlighted the relevance of these metabolic processes to Plasmodium falciparum during the different stages of the lifecycle.

Mitocentricity.

Worldwide, interest in mitochondria is constantly growing, as evidenced by scientific statistics, and studies of the functioning of these organelles are becoming more prevalent than studies of other cellular structures. In this analytical review, mitochondria are conditionally placed in a certain cellular center, which is responsible for both energy production and other non-energetic functions, without which the existence of not only the eukaryotic cell itself, but also the entire organism is impossible. Taking into account the high multifunctionality of mitochondria, such a fundamentally new scheme of cell functioning organization, including mitochondrial management of processes that determine cell survival and death, may be justified. Considering that this issue is dedicated to the memory of V. P. Skulachev, who can be called mitocentric, due to the history of his scientific activity almost entirely aimed at studying mitochondria, this work examines those aspects of mitochondrial functioning that were directly or indirectly the focus of attention of this outstanding scientist. We list all possible known mitochondrial functions, including membrane potential generation, synthesis of Fe-S clusters, steroid hormones, heme, fatty acids, and CO2. Special attention is paid to the participation of mitochondria in the formation and transport of water, as a powerful biochemical cellular and mitochondrial regulator. The history of research on reactive oxygen species that generate mitochondria is subject to significant analysis. In the section "Mitochondria in the center of death", special emphasis is placed on the analysis of what role and how mitochondria can play and determine the program of death of an organism (phenoptosis) and the contribution made to these studies by V. P. Skulachev.

Two novel variants in the SLC25A38 gene among two Iranian families with congenital sideroblastic anemia

Congenital Sideroblastic Anemia (CSA) is a rare genetic disease caused by mutations in genes related to heme synthesis pathway, FeS cluster and mitochondrial protein synthesis. Changes in the SLC25A38 gene have been reported as one of the reasons of non syndromic autosomal recessive congenital sideroblastic anemia.In this study we had two patients in two families with the symptoms of CSA. After performing Whole Exome Sequencing (WES), a novel nonsense variant (c.166C > T, p.Gln56Ter) and a novel frameshift variant (c.220_221insTTCA, p.Leu75HisfsTer79) in the SLC25A38 gene were identified in the families.Then, Sanger sequencing and segregation analysis were used to confirm the variants. The sequencing confirmed that these variants were homozygous in each proband and heterozygous in their parents.After that, the variant effects and its pathogenicity were evaluated using different bioinformatics analysis which identified the existing variant as pathogenic in more cases.The results of real-time PCR also showed that the level of mRNA expression of the gene in the patient with nonsense variant was significantly down-regulated compared to the normal person (p < 0.001).This is one of the first studies about the sideroblastic anemia in Khuzestan province of Iran and its results could indicate the relationship between this gene and CSA in this population. Our findings suggests that the mentioned variants, in an allele of the SLC25A38 gene, by alone, not enough to cause disease. This study also increases the list of mutations involved in the SLC25A38 gene and raises our knowledge about the role of this gene in CSA disease and would be very useful for screening in populations.

44 Dual Proteomic Exploration of the Mechanisms Underlying Brake Dust-Induced Impairment of Phagocytic Capacity in Macrophages

Abstract Exposure to brake abrasion dust (BAD) reduces the phagocytic capacity of macrophages, possibly contributing to increased risk of airway infections in polluted regions. The mechanisms that underlie this toxicity remain to be characterised and, considering that pre-exposure of respiratory bacteria to alternative traffic-related particulates enhances their dissemination into the lungs of mice, may include changes in the virulence of pathogens themselves. Dual proteomic screening (TMT-labelled UPLC-MS) was performed for RAW 264.7 monocyte-derived macrophages and S.aureus (USA300) following 24h exposures to BAD (0-16 ug/ml). In S.aureus, expression of agr-regulated, anti-leukocytic virulence factors (lipases, staphopains, hemolysins) increased in a dose-dependent manner as well as proteins required for epithelial invasion (serine proteases) and antibiotic resistance. RAW 264.7 exhibited a predominantly adaptive response following exposures, enhancing expression of proteins required for metal homeostasis, NFkB-mediated inflammation and endosomal maturation. However, disrupted expression of proteins required for electron transport chain activity and Fe-S cluster synthesis accompanied significant dose-dependent reductions in ATP production (60-82%, p&amp;lt; 0.001) while transition electron microscopy (TEM) detected disrupted mitochondrial membrane morphology. TEM also identified reductions in pseudopodia length in exposed macrophages (54% shorter than control, p&amp;lt; 0.05), highlighting a mechanism by which BAD exposure may decrease the incidence of host-pathogen interactions. These data highlight dual mechanisms by which BAD emissions could impair bacterial phagocytosis and enhance susceptibility to airway infections. Through avoidance and suppression of host anti-microbial mechanisms by the bacteria and, as actin polymerisation depends on ATP availability, loss of mitochondrial function and downstream pseudopodia projection in macrophages.

Maintenance of genome integrity by the late-acting cytoplasmic iron-sulfur assembly (CIA) complex.

Iron-sulfur (Fe-S) clusters are unique, redox-active co-factors ubiquitous throughout cellular metabolism. Fe-S cluster synthesis, trafficking, and coordination result from highly coordinated, evolutionarily conserved biosynthetic processes. The initial Fe-S cluster synthesis occurs within the mitochondria; however, the maturation of Fe-S clusters culminating in their ultimate insertion into appropriate cytosolic/nuclear proteins is coordinated by a late-acting cytosolic iron-sulfur assembly (CIA) complex in the cytosol. Several nuclear proteins involved in DNA replication and repair interact with the CIA complex and contain Fe-S clusters necessary for proper enzymatic activity. Moreover, it is currently hypothesized that the late-acting CIA complex regulates the maintenance of genome integrity and is an integral feature of DNA metabolism. This review describes the late-acting CIA complex and several [4Fe-4S] DNA metabolic enzymes associated with maintaining genome stability.

An early origin of iron-sulfur cluster biosynthesis machineries before Earth oxygenation.

Iron-sulfur (Fe-S) clusters are ubiquitous cofactors essential for life. It is largely thought that the emergence of oxygenic photosynthesis and progressive oxygenation of the atmosphere led to the origin of multiprotein machineries (ISC, NIF and SUF) assisting Fe-S cluster synthesis in the presence of oxidative stress and shortage of bioavailable iron. However, previous analyses have left unclear the origin and evolution of these systems. Here, we combine exhaustive homology searches with genomic context analysis and phylogeny to precisely identify Fe-S cluster biogenesis systems in over 10,000 archaeal and bacterial genomes. We highlight the existence of two additional and clearly distinct 'minimal' Fe-S cluster assembly machineries, MIS (minimal iron-sulfur) and SMS (SUF-like minimal system), which we infer in the last universal common ancestor (LUCA) and we experimentally validate SMS as a bona fide Fe-S cluster biogenesis system. These ancestral systems were kept in archaea whereas they went through stepwise complexification in bacteria to incorporate additional functions for higher Fe-S cluster synthesis efficiency leading to SUF, ISC and NIF. Horizontal gene transfers and losses then shaped the current distribution of these systems, driving ecological adaptations such as the emergence of aerobic lifestyles in archaea. Our results show that dedicated machineries were in place early in evolution to assist Fe-S cluster biogenesis and that their origin is not directly linked to Earth oxygenation.

Molecular Basis of Rare Diseases Associated to the Maturation of Mitochondrial [4Fe-4S]-Containing Proteins

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.

Multiple Independent Losses of Photosynthetic Ability in Eukaryotic Evolution and the Metabolism of Non-Photosynthetic Plastids

Multiple independent losses of photosynthesis have occurred among several unrelated eukaryotic lineages including red and green algae, land plants, alveolates, stramenopiles, cryptophytes and euglenophytes. Most plastid genomes of non-photosynthetic eukaryotes do not contain genes associated with photosynthesis, but they usually encode at least one gene product involved in an essential non-photosynthetic metabolic pathway. Complete loss of plastid genome and simultaneous retention of plastid compartment is rare, and complete plastid loss is documented only for few alveolate species. Non-photosynthetic plastids are often involved in essential fatty acid, isoprenoid, Fe-S cluster, and heme synthesis.

Differential contribution of two organelles of endosymbiotic origin to iron-sulfur cluster synthesis and overall fitness in Toxoplasma.

Iron-sulfur (Fe-S) clusters are one of the most ancient and ubiquitous prosthetic groups, and they are required by a variety of proteins involved in important metabolic processes. Apicomplexan parasites have inherited different plastidic and mitochondrial Fe-S clusters biosynthesis pathways through endosymbiosis. We have investigated the relative contributions of these pathways to the fitness of Toxoplasma gondii, an apicomplexan parasite causing disease in humans, by generating specific mutants. Phenotypic analysis and quantitative proteomics allowed us to highlight notable differences in these mutants. Both Fe-S cluster synthesis pathways are necessary for optimal parasite growth in vitro, but their disruption leads to markedly different fates: impairment of the plastidic pathway leads to a loss of the organelle and to parasite death, while disruption of the mitochondrial pathway trigger differentiation into a stress resistance stage. This highlights that otherwise similar biochemical pathways hosted by different sub-cellular compartments can have very different contributions to the biology of the parasites, which is something to consider when exploring novel strategies for therapeutic intervention.

Overexpression and characterization of Escherichia coli dihydropyrimidine dehydrogenase: a four iron-sulphur cluster containing flavoprotein.

Escherichia coli dihydropyrimidine dehydrogenase (EcDPD) catalyses the NADH-dependent reduction of uracil and thymine to the corresponding 5,6-dihydropyrimidines to control their metabolite pools. EcDPD consists of two subunits, PreT and PreA, and requires FAD, FMN and Fe-S clusters for activity. Recombinant EcDPD with a C-terminal His6-tagged-PreA subunit was overproduced in a DPD-lacking E. coli cells with augmented Fe-S cluster synthesis. Anaerobic purification resulted in purified enzyme with a specific activity of 13 μmol min-1 mg-1. The purified EcDPD was a heterotetramer and contained 0.81 FAD, 0.99 FMN, 14 acid-labile sulphur and 15 iron per PreT-PreA dimer. The enzyme exhibited Michaelis-Menten kinetics for both the forward and reverse reactions, which is distinct from mammalian DPDs showing substrate inhibition kinetics. For uracil reduction, the kcat, kcat/KNADH and kcat/Kuracil values were constant over the pH range of 5.5-10. For dihydrouracil (DHU) dehydrogenation, the pH-dependence of the kcat and kcat/KNAD+ values indicated that a residue with a pKa of 6.6 must be deprotonated for activity. Biochemical and kinetic comparisons with pig DPD revealed that protonation sates of the catalytically competent forms of EcDPD are distinct from those of pig enzyme.

Occurrence, Evolution and Specificities of Iron-Sulfur Proteins and Maturation Factors in Chloroplasts from Algae.

Iron-containing proteins, including iron-sulfur (Fe-S) proteins, are essential for numerous electron transfer and metabolic reactions. They are present in most subcellular compartments. In plastids, in addition to sustaining the linear and cyclic photosynthetic electron transfer chains, Fe-S proteins participate in carbon, nitrogen, and sulfur assimilation, tetrapyrrole and isoprenoid metabolism, and lipoic acid and thiamine synthesis. The synthesis of Fe-S clusters, their trafficking, and their insertion into chloroplastic proteins necessitate the so-called sulfur mobilization (SUF) protein machinery. In the first part, we describe the molecular mechanisms that allow Fe-S cluster synthesis and insertion into acceptor proteins by the SUF machinery and analyze the occurrence of the SUF components in microalgae, focusing in particular on the green alga Chlamydomonas reinhardtii. In the second part, we describe chloroplastic Fe-S protein-dependent pathways that are specific to Chlamydomonas or for which Chlamydomonas presents specificities compared to terrestrial plants, putting notable emphasis on the contribution of Fe-S proteins to chlorophyll synthesis in the dark and to the fermentative metabolism. The occurrence and evolutionary conservation of these enzymes and pathways have been analyzed in all supergroups of microalgae performing oxygenic photosynthesis.

Fe-S Protein Synthesis in Green Algae Mitochondria.

Iron and sulfur are two essential elements for all organisms. These elements form the Fe-S clusters that are present as cofactors in numerous proteins and protein complexes related to key processes in cells, such as respiration and photosynthesis, and participate in numerous enzymatic reactions. In photosynthetic organisms, the ISC and SUF Fe-S cluster synthesis pathways are located in organelles, mitochondria, and chloroplasts, respectively. There is also a third biosynthetic machinery in the cytosol (CIA) that is dependent on the mitochondria for its function. The genes and proteins that participate in these assembly pathways have been described mainly in bacteria, yeasts, humans, and recently in higher plants. However, little is known about the proteins that participate in these processes in algae. This review work is mainly focused on releasing the information on the existence of genes and proteins of green algae (chlorophytes) that could participate in the assembly process of Fe-S groups, especially in the mitochondrial ISC and CIA pathways.

TRNA Modifications as a Readout of S and Fe-S Metabolism.

Iron-Sulfur (Fe-S) clusters function as core prosthetic groups known to modulate the activity of metalloenzymes, act as trafficking vehicles for biological iron and sulfur, and participate in several intersecting metabolic pathways. The formation of these clusters is initiated by a class of enzymes called cysteine desulfurases, whose primary function is to shuttle sulfur from the amino acid L-cysteine to a variety of sulfur transfer proteins involved in Fe-S cluster synthesis as well as in the synthesis of other thiocofactors. Thus, sulfur and Fe-S cluster metabolism are connected through shared enzyme intermediates, and defects in their associated pathways cause a myriad of pleiotropic phenotypes, which are difficult to dissect. Post-transcriptionally modified transfer RNA (tRNA) represents a large class of analytes whose synthesis often requires the coordinated participation of sulfur transfer and Fe-S enzymes. Therefore, these molecules can be used as biologically relevant readouts for cellular Fe and S status. Methods employing LC-MS technology provide a valuable experimental tool to determine the relative levels of tRNA modification in biological samples and, consequently, to assess genetic, nutritional, and environmental factors modulating reactions dependent on Fe-S clusters. Herein, we describe a robust method for extracting RNA and analytically evaluating the degree of Fe-S-dependent and -independent tRNA modifications via an LC-MS platform.

Circular Dichroism to Probe the Synthesis, Transfer, and Stability of Fe-S Clusters.

All Fe-S proteins are characterized by distinctive circular dichroism (CD) features in the visible region of the spectrum due to chiral interaction between the cluster itself and the protein backbone. Therefore, the presence of a CD signal in the visible region relates to the presence of the cluster, whereas the disappearance of the signal refers to cluster breakdown or redox changes. The position of the CD features in the spectrum and the intensity of individual components of the CD signal show great variations among different Fe-S proteins. This feature can provide information on transfer processes between proteins, as well as on possible changes in cluster nuclearity. This method can also be used to detect changes in the chemical nature or spatial organization of cluster ligands that may be concurrent with cluster transfer and associated events.

A key cytosolic iron-sulfur cluster synthesis protein localizes to the mitochondrion of Toxoplasma gondii.

Iron-sulfur (Fe-S) clusters are prosthetic groups on proteins that function in a range of enzymatic and electron transfer reactions. Fe-S cluster synthesis is essential for the survival of all eukaryotes. Independent Fe-S cluster biosynthesis pathways occur in the mitochondrion, plastid, and cytosolic compartments of eukaryotic cells. Little is known about the cytosolic Fe-S cluster biosynthesis in apicomplexan parasites, the causative agents of diseases such as malaria and toxoplasmosis. NBP35 serves as a key scaffold protein on which cytosolic Fe-S clusters assemble, and has a cytosolic localization in most eukaryotes studied thus far. Unexpectedly, we found that the NBP35 homolog of the apicomplexan Toxoplasma gondii (TgNBP35) localizes to the outer mitochondrial membrane, with mitochondrial targeting mediated by an N-terminal transmembrane domain. We demonstrate that TgNBP35 is critical for parasite proliferation, but that, despite its mitochondrial localization, it is not required for Fe-S cluster synthesis in the mitochondrion. Instead, we establish that TgNBP35 is important for the biogenesis of cytosolic Fe-S proteins. Our data are consistent with TgNBP35 playing a central and specific role in cytosolic Fe-S cluster biosynthesis, and imply that the assembly of cytosolic Fe-S clusters occurs on the cytosolic face of the outer mitochondrial membrane in these parasites.

Abstract PO-028: Investigating the contribution of CHAC1 to persistent mitochondrial respiratory function in NSCLC under cysteine deprivation

Abstract Solid tumors exhibit metabolic rewiring to enhance their energetic capacity while meeting the biosynthetic demands for rapid proliferation. Though this reprogramming supports robust tumor growth, it often imposes bottlenecks and metabolic dependencies that can be exploited clinically. Among the metabolic vulnerabilities that is of therapeutic interest is the sensitivity of many cancers to sustained deprivation of the non-essential amino acid cysteine (Cys). In certain malignant contexts, ferroptosis has been linked to mitochondrial dysfunction, where oxidative metabolism drives ROS production, the loss of mitochondrial membrane integrity and respiratory function, leading to the propagation of lipid radicals that cripple cell viability. We found that while non-small cell lung cancer (NSCLC) cells are susceptible to Cys-starvation induced ferroptosis, mitochondrial respiratory function robustly persists under prolonged Cys deprivation in these NSCLC cells. We also find that mitochondrial iron-sulfur (Fe-S) protein function (e.g. aconitase, lipoic acid synthase, and respiratory complexes I-III) critical to oxidative metabolism is unaltered by Cys deprivation despite the need for Cys-derived sulfur in the synthesis of Fe-S clusters. Under these Cys-restricted conditions, we observe an increase in the expression of glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1), a mitochondrial protein that catalyzes the degradation of the antioxidant glutathione (GSH). Because Cys is a constituent of the tripeptide antioxidant, enhanced mitochondrial GSH turnover could provide Cys for the generation of Fe-S clusters. Consistent with this, CRISPR-mediated knockout of CHAC1 diminished Fe-S protein function in Cys-starved NSCLC cells. Despite this decrease in oxidative capacity, CHAC1 knockout prolonged survival under Cys-deprivation, suggesting that intact mitochondrial function may contribute to Cys-starvation induced cell death. Enhanced GSH degradation by CHAC1 would also restrict GSH-based antioxidant capacity imposing a greater requirement for the NADPH-dependent thioredoxin system. Interestingly, we find that Cys deprivation also induces the expression of nicotinamide nucleotide transhydrogenase (NNT), a critical contributor of mitochondrial NADPH in lung cancer. Moreover, we find that the activity of the mitochondrial NADPH-producing isocitrate dehydrogenase (IDH2) is enhanced under Cys deprivation independent of a change in expression. Collectively, these data indicate a potential rewiring of mitochondrial antioxidant defenses for the maintenance of robust mitochondrial respiratory function in the absence of extracellular Cys. This ultimately may constitute a self-defeating response to nutrient stress in NSCLC, where mitochondria selfishly sustain functionality at the expense of cell viability. Citation Format: Nathan P. Ward, Gina M. DeNicola. Investigating the contribution of CHAC1 to persistent mitochondrial respiratory function in NSCLC under cysteine deprivation [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-028.

A Global Proteomic Approach Sheds New Light on Potential Iron-Sulfur Client Proteins of the Chloroplastic Maturation Factor NFU3.

Iron-sulfur (Fe-S) proteins play critical functions in plants. Most Fe-S proteins are synthetized in the cytosol as apo-proteins and the subsequent Fe-S cluster incorporation relies on specific protein assembly machineries. They are notably formed by a scaffold complex, which serves for the de novo Fe-S cluster synthesis, and by transfer proteins that insure cluster delivery to apo-targets. However, scarce information is available about the maturation pathways of most plastidial Fe-S proteins and their specificities towards transfer proteins of the associated SUF machinery. To gain more insights into these steps, the expression and protein localization of the NFU1, NFU2, and NFU3 transfer proteins were analyzed in various Arabidopsis thaliana organs and tissues showing quite similar expression patterns. In addition, quantitative proteomic analysis of an nfu3 loss-of-function mutant allowed to propose novel potential client proteins for NFU3 and to show that the protein accumulation profiles and thus metabolic adjustments differ substantially from those established in the nfu2 mutant. By clarifying the respective roles of the three plastidial NFU paralogs, these data allow better delineating the maturation process of plastidial Fe-S proteins.